GENETIC ANALYSIS FOR DESIRABLE ATTRIBUTES IN POPCORN …

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GENETIC ANALYSIS FOR DESIRABLE ATTRIBUTES IN POPCORN

BY

MUHAMMAD NOOR

A dissertation submitted to The University of Agriculture, Peshawar

in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY (Ph. D) IN AGRICULTURE

(PLANT BREEDING AND GENETICS)

DEPARTMENT OF PLANT BREEDING AND GENETICS

FACULTY OF CROP PRODUCTION SCIENCES

THE UNIVERSITY OF AGRICULTURE

PESHAWAR, PAKISTAN

DECEMBER, 2015

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TABLE OF CONTENTS

CHAPTER NO TITLE PAGE NO

TABLE OF CONTENTS…………………………………………………….......i

LIST OF TABLES………………………………………………………………ii

LIST OF APPENDICES ………………………………………………………...iv

ACKNOWLEDGEMENT .......................................................................................v

ABSTRACT...............................................................................................................vi

1. INTRODUCTION……………………………………………………………….1

2. REVIEW OF LITERATURE……………………………………………………6

2.1 Gene action………………………………………………………6

2.2 Heritability………………………………………………………15

2.3 Heterosis ………………………………………………………..22

2.4 Correlation ……………………………………………………...27

3. MATERIALS AND METHODS…………………………………………..……33

3.1 Screening for parents selection ……………………………..….33

3.2 Development of F1 generations …..…………………………….35

3.3 Development of F2 and back crosses …………………………..35

3.4 Field evaluation………………………………………………….36

3.5 Statistical analysis…………………………………………….....40

5. RESULTS……………………………………………………………………….47

5.1 Generation means analysis ………………………………………47

5.2 Heritability estimates ………………………………………….....63

5.3 Heterosis percentage ………...........................................................70

5.4 Genotypic and phenotypic association among traits ....…………..77

6. DISCUSSION……………………………………………………………………96

6.1 Gene action...…………………………………………………….96

6.2 Heritability…. …………………………………............................111

6.3 Heterosis ………………………………………………………...121

6.4 Genotypic and phenotypic association among traits ......................129

SUMMARY………………………………………………………………..……157

CONCLUSIONS ………………………………………………………………..159

LITERATURE CITED…………………………………………………..………160

APPENDICES ……………………………..……………………………………186

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LIST OF TABLES

TABLE NO TITLE PAGE NO

3.1 Mean square values for days to tasseling ................................................. ….33

3.2 List of popcorn inbredlines used in selection of .................................... ….34

3.3 Mean values for days to tasseling ............................................................. ….34

3.4 Pedigree list of selected parents ............................................................... ….35

3.5 List of F1 hybrids ...................................................................................... ….36

3.6 List of BC1 generations ………………………………………………… 36

3.7 List of BC2 generations ………………………………………………….36

3.8 Analysis of variance for generations……………….……………………...41

3.9 Coefficients of and utilized……..………….….………………………42

3.10 Analysis of variance for generations………………….……………………45

3.11 Analysis of covariance for generations………………….………………....45

4.1 Estimates of genetic effects for some quantitative traits in four maize

crosses combined over two locations………………………………..……53

4.2 Estimates of genetic effects for quantitative traits in four maize

crosses combined over two locations ………………………………..……56


crosses combined over two locations .……………………………….……60


crosses combined over two locations .……………………………….……62

4.5 Broad and narrow sense heritability estimates for quantitative

traits in four maize crosses combined over two locations locations...…….68

4.6 Mid and better parent heterosis for quantitative traits for four

maize crosses combined over two locations …….…………..…………...76

4.7 Genotypic (rG) and phenotypic (rP) correlation coefficients among

physiological traits for cross I combined over two locations……………..83

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physiological traits for cross II combined over two locations……………86


physiological traits for cross III combined over two locations…………...89


physiological traits for cross IV combined over two locations…………...92

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LIST OF APPENDICES

APPENDIX NO TITLE PAGE NO

1 Combined analysis of variance for generation means

for days to tasseling, anthesis and silking ………...……..…..186

2 Combined analysis of variance for generation means

for days to maturity, plant height and ear height ……………...186

3. Combined analysis of variance for generation means

for fresh ear weight, ear length and ear diameter ………….…..187

4. Combined analysis of variance for generation

means for kernel rows ear -1, grains row-1 and

grains ear-1 ...................................................................................187

5. Combined analysis of variance for generation means for

100-grain weight, grain yield and biological

yield ……………………………………………...……….…..188

6. Combined analysis of variance for generation means

for harvest index, expansion volume, % unpopped

grains and % shelling ………………………………………..188

7. Generation means from combined analysis for days

to tasseling, anthesis, silking and maturity over two

locations …………………………………………..…………189

8. Generation means from combined analysis for

plant height, ear height and ear weight over two

locations ………………………………………………….….189

9. Generation means from combined analysis for grain yield,

ear length and ear diameter over two locations …………..….190


kernel rows ear-1, grains row-1 and grains ear-1………………190


100-grain weight, harvest index and % shelling

over two locations …………………………………….……..191


expansion volume, % unpopped grains and biological

yield over two locations ……………………………………….191

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ACKNOWLEDGEMENTS

I really have no words to express my deepest sense of gratitude to almighty “ALLAH”,

the most merciful, the most beneficent and the unique source of all knowledge and wisdom

endowed to every mankind, who bestowed upon me the courage to complete this project and to

contribute to the noble field of knowledge. Cordial gratitude and countless salutations to be upon

the Holy Prophet “ Hazrat Muhammad (S.A.W)” , the most perfect among and ever born on the

earth, who is forever a torch of guidance and knowledge for human beings as a whole.

It was an honor for me to have Professor Dr. Hidayat-ur-Rahman as my major supervisor.

His advice, friendship, understanding, helpful suggestions and support during my scholastic life

were invaluable for the development of my study and research programs.

I wish to express my deepest gratitude and profound regards to my honorable co-

supervisor Dr. Muhammad Iqbal for providing plant material, encouragements, helpful

suggestions, friendship, guidance and outstanding support throughout my research on his station.

I would like to express great appreciation and my special acknowledgments to have Dr.

Iftikhar Hussain Khalil and Dr. Sajjid Ali. Their guidance, support and valuable suggestions

were very useful for the development of my studies.

The author also feels highly privileged to express heartfelt thanks to Prof. Dr. Fida

Mohammad, Chairman Department of Plant Breeding and Genetics for his kind cooperation and

encouragement throughout my study.

I am highly indebted to Mr. Muhammad Ramiz, Institute of Biotechnology and Genetic

Engineering (IBGE), The University of Agriculture, Peshawar for his cooperation and helpful

guidance in molecular analysis and interpretation of obtained results of my study.

I am very much thankful to my friends and contemporaries especially Muhammad Yasir,

Hamid ur Rahman, Dr. Farhan Ali, Irfan Ahmed Shah and Ihteram Ullah for their moral support,

cooperation, encouragement and unlimited prayers throughout my Ph. D.

Finally, my special and cordial gratitude to all of my relatives and my family members

especially to my farther for their sacrifices, understandings, patience and being a constant source

of prayers and inspiration that enabled me to achieve this really difficult task.

Muhammad Noor

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GENETIC ANALYSIS FOR DESIRABLE ATTRIBUTES IN POPCORN

Muhammad Noor and Hidayat ur Rahman

Department of Plant Breeding and Genetics

The University of Agriculture, Peshawar

December, 2015

ABSTRACT

Quantification of genetic attributes including gene action, heterotic behavior, heritability

estimates, phenotypic and genotypic associations are important statistical tools in progressive

breeding programs. The genetic material includes eight diverse popcorn inbred lines in which

four were selected on the basis of phenotypic variation. Two of the four parents were developed

from indigenous popcorn material, while the other two were of exotic (Bangladesh). Parental

inbred lines were crossed to get four F1 crosses. These F1 crosses were selfed to generate F2 and

back crossed with their female and male parents to obtained, BC1 and BC2, respectively. In such

way total genetic material synthesized in this study include four each of parents, F1s, F2s, BC1s

and BC2s. These generations were evaluated at two locations i.e. Cereal Crops Research Institute

(CCRI), Pirsabak, Nowshehra and The University of Agriculture (UOA), Peshawar. At both

locations the experimental material was replicated thrice in randomized complete block design.

Data recorded were analyzed using combined analysis of variance. Combined analysis of

variance in all four crosses, revealed non-significant genotype × location interactions in days to

tasseling, silking, anthesis, ear length, fresh ear weight, kernel rows ear-1, grains row-1, grains

ear-1 and % unpopped grains, while rest traits exhibited significant genotype × location

interactions in some crosses. Significant genotype × location interactions were observed for ear

diameter in all crosses.

Generation mean analysis indicated that in all crosses dominant gene action was

predominantly important in the inheritance of both days to tasseling, anthesis and silking. The

additive gene effect was found to be negative in these crosses but significant except PS-Pop-29-

2-1 x BD- Pop-2-1-2 for anthesis. The digenic non-allelic epistasis of additive x dominance and

dominance x dominance was considered the major contributing factor in the inheritance of days

to anthesis in cross PS-1 x BD-2 and PS-2 x BD-2. Duplicate type of epistasis was observed in

cross PS-1 × BD-1 for days to anthesis and silking, while complementary epistasis was observed

in cross PS-1 x BD-2. Similarly, dominant gene actions were positive and significant in all

crosses except, PS-2 × BD-1 (-9.16) for plant and ear height. Duplicate type of epistasis was

observed for ear height in both cross PS-1 × BD-1 and PS-1 × BD-2, while in cross PS-2 × BD-1

and PS-2 × BD-2 complementary epistasis was found. On the basis of these results, it can be

concluded that crosses in which additive gene effects were high, could be improved effectively

in subsequent generations. For grain yield and related traits dominant gene action was positively

significant in all crosses, indicating that the parental populations could be effectively utilized in

hybrid development programs.

Broad sense heritability estimates for all the studied characters varied from moderate to

high level, while narrow sense heritability ranged from low to high in all crosses. Maximum

broad sense heritability estimates for days to tasseling (0.76 and 0.76) and anthesis (0.84 and

0.83) were observed in crosses PS-1 × BD-2 and PS-2 × BD-2, respectively. Maximum narrow

sense heritability estimates for days to anthesis (0.67 and 0.57) and silking (0.67 and 0.58) were

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observed in cross PS-1 × BD-2 and PS-2 × BD-2, respectively. High broad sense (0.82) and

narrow sense (0.62) heritability estimates calculated for grain yield were observed in cross PS-2

× BD-1 and Cross PS-1 × BD-1, respectively. Grain yield related attributes exhibited high broad

sense heritability, while narrow sense heritability estimates for these traits varied from moderate

to high levels, which indicate greater contribution of the genetic portion in the inheritance.

Quality parameter, expansion volume revealed maximum broad sense heritability of 0.76 and

narrow sense heritability of 0.50 for cross PS-1 × BD-1 and PS-2 × BD-1, respectively.

Heterotic levels both, mid parent and better parent were negative for flowering characters

in all crosses. Maximum negative mid- and better parent heterosis of -7.15 and -3.77 for days to

tasseling was observed in cross PS-1 × BD-1 and PS-2 × BD-1, respectively. In cross PS-2 ×

BD-1, maximum negative mid- and better parent heterosis were observed for days to anthesis (-

6.74 and -3.65) and silking (-6.48 and -3.40). Heterotic levels both, mid parent and better parent

were positive and high in magnitude for grain yield and all related attributes. Cross PS-1 × BD-2,

exhibited maximum mid- (80.73) and better (62.74) heterotic values for grain yield. Maximum

mid- and better parent heterotic values are indication of dominance gene actions in all four

crosses.

Genetic and phenotypic association of flowering characteristics with grain yield were

negative in nature, while yield related attributes were positively correlated with grain yield.

Grain yield was positively correlated with plant height, while negatively correlated with ear

height in two crosses. Quality trait of expansion volume was negatively associated with grain

yield.

Based on our results, it would be wise to use those parents in hybrid crosses which

exhibited both additive and dominant gene actions coupled with high narrow sense heritability

estimates and having strong relationship along with high heterotic levels for most of the grain

yield related traits. Although all the F1 hybrids were superior but the PS-2 x BD-2 was

outstanding for grain yield. Therefore, this cross can be recommended for commercial

cultivation. Both popping expansion and percent of unpopped grains was positively and

significantly controlled by dominant genes in two of the four crosses, while in the other two

crosses dominant gene actions were negative in nature.

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Chapter 1

INTRODUCTION

Maize (Zea mays L.) is one of the most important cereal crops in the world and is

classified as extremely diverse crop genetically due to its cross pollinated nature. It is grown at

an altitude from sea level to about 3300 meters above the sea level and from 500N to 400S

latitude as a multipurpose crop in temperate, sub-tropical and tropical regions of the world.

Maize is a cross pollinated crop under natural conditions, where 95% of the grains are the result

of pollen from the nearby plants and the remaining kernels are produced by self-pollination.

Maize behaves in a protandrous way, a phenomenon in which the pollen shedding normally

begins one to three days prior to the emergence of silks (Ali et al., 2011). Maize is a good source

of nutrients and plays a key role in the economy of several countries. It also serves as an

industrial grain crop with variety of products throughout the world (White and Johnson, 2003).

Plant breeding is an art and science of changing and improving the genetic pattern of crop

plants in relation to their economic use with the application of different selection techniques.

When the genetic variability is high the process of selection becomes easy to identify genotypes

with superior attributes. In case of limited variation the breeders usually use diverse technical

approaches to increase the level of variability. Controlled pollination approach is the basic source

of creating variability i.e., cross pollinated species is more variable than self pollinated species.

The differentiation of two maize inbred lines at genetic level is surpasses the difference between

chimpanzee and human being (Yan et al., 2010). The development of maize plants structure and

stature depends upon the genetic variability being present within the 10 chromosomes. Exploring

the genetic potential of this crop is mainly focused to solve the bottlenecks in the field of

genetics and breeding (Ali et al., 2013). Therefore, knowledge of genes involved in determining

different traits is crucial to manipulate maize germplasm in the desirable direction and overcome

the problem of food security (Ali and Yan, 2012). A great diversity in morphology and

physiology of maize is resulted in the process of selection. Based on endosperm and glume

characteristics maize is grouped into seven types including dent, flint, flour, sweet, waxy, pop

and pod corn (Acquaah, 2007). These groups are based on quality, quantity and pattern of the

endosperm composition in kernels, except for pod corn which has primitive characteristics.

Mutation at a single locus may alter the composition of endosperm, as in the case of floury (fl)

versus flint (FI), sugary (su) versus starchy (Su), waxy (wx) versus non-waxy (Wx).

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Popcorn (Zea mays evertaSturt.) or popping corn puffs up upon exposure to heat because

its kernels have a hard moisture-sealed hull and a dense starchy interior. Popcorn has a

distinguished characteristic of large flake formation after kernel popping due to heat. Popcorn

popularity, as a snack food for consumers has increased over the passage of time in developing

countries. Grain yield, popping intensity and popping volume are considered as important

attributes of popcorn. Popcorn needs similar growth requirements as provided to dent corn, with

less adaptability to environmental extremes (Ziegler, 2001).The kernel shape, structure and size

of popcorn make it different from standard grain quality maize. Popcorn is further grouped in

two types: rice-shaped and pearl-shaped popping maize kernels (Acquaah, 2007). Like other

members of family poaceae, the kernel of popcorn contains three major structural parts:

endosperm, germ and pericarp. Pericarp in popcorn grain acts as an outer covering and protective

coat enclosing the kernel and directly takes part in the popping action. During the kernels heat

treatment of popcorn, the pericarp behaves as a vessel under a pressure. The hard moisture-

sealed hull of kernels allows pressure to build inside and explosive “pop” results. Popping of

popcorn kernel occur when inner kernel temperature reach about 177oC. At high temperature the

present moisture in the kernel transforms into steam and provides the force that expands the

grain and breaks the pericarp. The optimum grain moisture content at popping varies over

genotypes, but usually ranges from 12% to 15% (Hoseney et al., 1983). In popcorn the

endosperm has both hard (corneous) and soft (floury) endosperm/starch. Hard endosperm

consists of compact polygonal starch granules, without inter granular spaces. Popcorn, which is

consumed as freshly popped corn, is a relatively minor crop compared to dent corn. The progress

curve of improvement in popcorn for agronomic traits, through selection is slower than that of

standard grain quality maize. The popping expansion or expansion volume of popcorn is the

most important and principal quality parameter, that smake it different from other types of maize.

According to Acquaah (2007), popping expansion is controlled by some dominant genes, and a

greater number of recessive genes, are also involved in the inheritance of other properties, like

flake shape and tenderness and pericarp dispersion at popping.

In cross pollinated species selfing causes inbreeding depression but once inbred lines

become stable and then crossed with genetically diverse inbreds, the result is the expression of

increased hybrid vigor/heterosis. Former researchers remarked genetically effective

improvement, as a result of synthesis, evaluation, selection and recombination of genetically

http://en.wikipedia.org/wiki/Husk

http://en.wikipedia.org/wiki/Starch

http://en.wikipedia.org/wiki/Husk

http://en.wikipedia.org/wiki/Pressure

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variable families/inbred lines used in maize breeding programs. Pixely et al. (2006) proposed

that superior and genetically improved maize cultivars must engross several desirable traits, at

the same time they also addressed that searching of desirable parents for hybrid combination is a

complicated, tedious and lengthy process. According to Ziegler (2001) breeding strategies used

for development of hybrid popcorn are similar to those used in other corn types. He also

mentioned that although improvement in popcorn agronomic traits is very slow but still breeders

have to keep in mind other important traits like, quality characters including, popping expansion,

freedom from hulls and objectionable flavors, and tenderness of the flakes. Grain yield per unit

area in popcorn is less than that of dent corn yield because the grain is usually small as compared

to the kernel of normal maize. Furthermore, the girth of popcorn compared to normal maize is

less.

Planning and execution of a breeding program requires information on the genetic

systems controlling the character of interest, so that the expected gain can be maximized with

selection process (Viana et al., 1999). An effective breeding program mainly depends on the

knowledge about type of gene action involved in the expression of a specific character. Among

genetic effects, dominance gene action results in hybrid vigor of F1 population over the parents..

Similarly additive gene action indicates an average effect of all loci for a trait so selection in

early generations would be effective in bringing about advantageous changes in character

(Edwards et al., 1976). Such information about genetic variances, levels of dominance, and other

non-additive genetic effects provide a base for better understanding of the gene action involved

in the expression of heterosis (Wolf and Hallauer, 1977).

Besides, other biometrical techniques generation mean analysis (GMA) provide efficient

information about estimation of different genetic effects controlling a trait. It also helps in

calculating the degree of dominance and level of additive effects (Mather and Jinks, 1982). The

genetic information obtained through generation mean analysis play a vital role in designing a

breeding method for the improvement of a desired trait. Gamble (1962) indicated that estimation

of genetic effects always help the plant breeders to decide an effective breeding procedure.

According to Hallauer and Miranda (1988) genetic information obtained through generation

mean analysis or other breeding methodologies, not only provide information about the way in

which genes act and interact with each other but also could be efficiently utilized in breeding

programs.

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The total genetic variance can be sub-divided into additive, dominance and epistatic

variance (Suzuki et al., 1981). Hallauer and Miranda (1988) estimated epistatic genetic effects in

maize hybrids using (i) triple-test crosses, (ii) making comparison of single, three-way and

double cross hybrids, or (iii) measuring variance components. The original generation means

analysis, proposed by Hayman (1958), measures the different generations derived from a cross

between two pure lines. Lamkey et al., (1995) suggested that epistasis plays a significant role in

elite maize hybrids production. Darrah and Hallauer (1972) observed that dominance effects

were several times larger than additive effects for all crosses in a maize diallel. The relative

magnitude of dominance gene effects was greater than the additive gene effects in the seedling

root characteristics in maize (Rahman et al., 1994). McConnell and Gardner (1979) detected

epistatic gene effects for grain yield in cold tolerant maize while additive and dominance gene

effects contributed significantly to the variation observed for germination and seedling vigor.

Wolf and Hallauer (1977) reported that an epistatic effect could contribute to the expression of

heterosis for specific hybrids. In the study of Darrah and Hallauer (1972), the additive by

additive and dominance by dominance effects for yield components (ear length, ear diameter and

number of kernel per row) were greater than plant height and ear height. Hallauer (1990)

reported that since inbreeding is conducted simultaneously with hybrid evaluations, favorable

epistatic gene combinations can ultimately be fixed in the inbred lines. Epistasis could also

explain why it has been difficult to develop improved recoveries from some maize inbreds

(Melchinger and Gumber, 1988; Lamkey et al., 1995). It seems that epistasis for complex traits,

such as yield, must exist, but realistic estimates of additive by additive epistasis have not been

obtainable. Other studies, however, have shown that epistatic effects are important for the

specific combination of inbred lines (Wolf and Hallauer, 1977; Lamkey et al., 1995; Chen et al.,

1996; Hinze and Lamkey, 2003). Hence, either the genetic models used are inadequate or

epistasis variance is small relative to the total genetic variance of the maize population (Hallauer

and Miranda, 1988). Biometric methods that use mean comparison rather than variance

component estimation (for example, generation mean analysis and triple test cross) have

regularly indicated that epistatic effects are important for grain yield in maize (Eta-Ndu and

Openshaw, 1999).

Due to cross pollinated nature breeding maize for specific traits require great attention of

plant breeders for commercial seed production. To achieve the objectives, an effective selection

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for specific traits along with some evaluation procedures like: the determination of popping

expansion and flake qualities in popcorn; determination of sugar content and other properties

important for sweet maize; the determination of the oil content in the high-oil types of maize, etc

are mandatory. This study was conducted with the following objectives to;

i. elucidate the pattern of inheritance for yield and yield associated traits in two

groups of maize (popcorn) with diverse origin.

ii. measure the magnitude of various genetic effects in these maize populations.

iii. quantify the magnitude of mid- parent, better-parent heterosis for studied traits.

iv. measure broad and narrow sense heritability estimates for studied characters.

v. measure the phenotypic and genotypic correlations among various parameters.

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Chapter 2

REVIEW OF LITERATURE

Manifestation of some important genetic parameters including, genetic effects, genetic

and phenotypic correlations, broad and narrow-sense heritability and heterosis of quantitative

characteristics are very essential for a sound and successful breeding program. Several types of

analytical techniques are used for estimation of different genetic attributes among which

generation means analysis is a powerful tool for the estimation of additive, dominance and

epistatic effects in quantitatively inherited traits. Plant breeders are always in search for the

exploitation of additive gene action in a quantitatively inherited trait. Their aim is to improve the

genetic ability of crop plants with high heritability. Narrow sense heritability with high additive

genetic correlation of positive nature is extremely important for long term improvement in maize

populations. Commendable research work on maize for these genetic parameters has been

conducted by several researchers to explore the phenomenon of gene action and serve as foot

marks for future research.

2.1 Gene action

A plant breeder must know about the magnitude and behavior of genetic components for

quantitative characters due to their key role in understanding the inheritance of quantitative traits.

Quantitative traits are usually considered to be controlled by multiple genes and are considerably

influenced with the interaction of environment. Generation mean analysis can be utilized to study

the pattern and magnitude of genetic variation present in a breeding population as well as to

obtain valuable preliminary information about the genetic mechanism involved in the expression

of a trait. The major role in designing a breeding method for the improvement of desired traits is

directly linked with the genetic effects obtained though generation mean analysis and other

biometrical techniques. A number of researchers have studied the mode of gene action in maize

through the pattern of diallel crossing techniques, but studies on the inheritance pattern of genes

through generation mean analysis in maize are meager. Information about gene action in maize

through generation mean analysis is albeit dearth throughout the world.

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An insight into the magnitude of variability present in a crop species is of utmost

importance as it provides the basis for effective selection. The total variation i.e., phenotypic

variation, present in a population arises due to genotypic and environmental effects. Phenotypic

variability is the observable variation present in a population for a character. Such variability

includes both genotypic and environmental components of variation. Due to a variable nature of

environmental conditions variation can be seen in phenotypic portion of variability under

different environments. In contrast genotypic variability remains approximately same under

changed environments because of the genetic components. It can be said that such portion of

variability is of the main concern of a plant breeder; because it is heritable and can therefore, in

principle, be manipulated in a breeding program. Fisher (1918) divided genetic variance into

three components: additive, dominance and epistatic variance. Additive variance refers to that

portion of genetic variance, which is produced by the deviations due to average effects of the

alleles of the genes at all segregating loci. Dominance variance arises due to the deviation from

the additive scheme of gene action resulting from intra-allelic interaction that is dominance.

Epistatic variance arises due to deviations as a consequence of inter allelic interactions. Hayman

and Mather (1955) further divided the epistatic variance into three components: additive x

additive, additive × dominance and dominance × dominance interactions. While, Wright (1980)

suggested partitioning of genetic variance into: additive and non-additive components and non-

additive component was further divided into dominance and epistatic components, of which only

the additive component contributes to genetic advance under selection. The variability present in

a breeding population can be assessed by three ways. i) by using simple measures of variability:

these measures include the range, variance, standard deviation, standard error and coefficient of

variation. ii) estimating the various components of variance. This involves the crossing of a

number of genotype or strains in a definite fashion and evaluation of progeny thus obtained in

replicated trials. Diallel, partial diallel, line × tester, generation means analyses are used to

estimate the components of genetic variance. e) by studying the genetic diversity within a

population.

Pípolo et al. (2003) assessed nine popcorn genotypes for genetic diversity through

multivariate techniques. The nine genotypes were divided into two groups by the Tocher method

using the generalized Mahalanobis distances. For selecting progressive parents data were

recorded on agronomic traits including popping expansion, popcorn size and grain mass per

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plant. After using the divergence and these trait scores as criteria for crossing, they

recommended the crosses between genotype 9 (group II) and genotypes 8, 3, 7, and 5 (group I).

Dvojkovic et al. (2004) quantified estimates of gene effects on grain yield components in

two wheat crosses. Eight generations (P1, P2, F1, F2, BC1.1, BC1.2, RBC1.1 and RBC1.2) were

raised and subjected to generation mean analysis for detecting the nature of gene effects in

different traits. In one cross digenic epistatic model was found adequate for grain weight while

additive gene effects in second cross. They expected genetic advance in further segregating

generations in crosses where additive effects with digenic epistasis more accompanied with high

narrow-sense heritability.

Ravikant et al. (2006) planted six generations of maize i.e., P1, P2, F1, F2, BC1 and BC2 to

learn the magnitude and nature of different genetic effects involved in the inheritance of yield

and yield contributing traits using generation means analysis techniques. It was revealed from

their study that most of the characters were controlled by additive type of gene action. They

further added that shelling percentage, grain yield plant-1 and some other traits were governed by

duplicate epistatic genetic effects. Sofi et al. (2006) investigated six generations in maize crosses

(P1, P2, F1, F2, BC1 and BC2) to determine type of gene action and interaction and linkage

relationship between genes for yield and its components through generation means analysis.

They found preponderance of dominant gene actions in the expression of studied traits except,

for days to 50% husk browning (maturity) and 100-grain weight which exhibited the prevalence

of additive type of gene action. Sofi and Rather (2006) studied inheritance of various plant

parameters during evaluation of different maize crosses along with parental lines and testers,

using line x tester analysis procedures. They depicted predominance of non-additive gene action

for most of the traits studied.

Azizi et al. (2006) studied the genetic effects grain yield and other traits through

generation mean analysis in maize inbred lines B73, Mo17 and K74/1 planted at three population

densities. Both additive and dominance effects as well as epistatic some interaction recovered for

most of the trait studied. However, dominant genetic effects were more pronounced than

additive. In both crosses epistasis interactions affected the expression of studied traits under

planting densities.

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Rangel et al. (2007) evaluated 10 popcorn populations for combining ability and genetic

variability of superior hybrids in a circulant diallel scheme. An experiment was conducted at four

different environments for effects on grain yield, plant height and popping expansion (PE). They

reported that evaluation of treatments at multiple locations fully expressed the present genetic

variability in the studied material. High additive effects were observed for PE and the dominance

effects for grain yield and plant height. UNB2U-C1 × Angela and Braskalb× Angela, showed

high grain yield and popping expansion among the combinations. The predicted mean PE and

GY were highest for hybrid UNB2U-C1 × Angela and the composite formed by these parents

(26.54 mL g-1 and 1,446.09 kg ha-1, respectively).

Miranda et al. (2008) characterized the Brazilian popcorn varieties for genetic variability

and heterotic groups. Ten hybrid combinations, i.e. five parents and five check treatments were

arranged in a randomized complete block design with four replicates at two locations. Both

additive and non-additive effects were reported in the inheritance of grain yield, plant height, ear

height, and husk cover, while only additive effects for popping expansion. Hybrid combinations

between the local variety (Branco) and F2 populations (IAC 112 and Zelia) resulted in the third

and fourth highest values for popping expansion. Based on the genetic variability present in

Brazilian popcorn, effective exploitation of additive and non-additive effects was suggested for

grain yield improvement.

Wattoo et al. (2009) studied the genetic analysis of grain yield and quality traits in maize.

Grain yield was narrated as a complex phenomenon in heterozygous crops like maize, and

phenotypic selection cannot directly improve the characters unless dissected by genetic analysis.

Variance/Co-variance graphs revealed that flowering, plant height and yield traits were

controlled by over dominance type of gene action, while quality traits like protein and oil

contents were under the control of partial dominance with additive type of gene action.

Iqbal et al. (2010) detected epistasis for plant height and leaf area palnt-1 in maize while

using generation mean analysis. Significant dominance effects with their high magnitude were

obtained in all crosses for both traits. All crosses in the study also indicated significant additive ×

dominance effects for leaf area. Significant additive × additive effects were also present in some

crosses for the two traits. The presence of complementary and duplicate gene interactions for leaf

24

area and duplicate gene actions in plant height in most crosses compelled them to propose a

slower improvement through selection.

Haq et al. (2010) determined genetic parameters of yield and other quantitative traits.

Analysis of variance showed that inbred lines differed significantly from each other for all traits.

Non-additive genetic effects were obvious in the inheritance study of plant height, flowering and

yield characters. Directional dominance was observed for all the characters under study. They

proposed the exploitation of heterotic effects due to the over-dominance gene action for all the

studied characters.

Ishfaq (2011) studied the genetic base of flowering traits in maize crop using progenies

(F1, F2, BC1, BC2) from a cross between cytoplasmic male sterile A-line I-401(A) and restorer

line I-318(R). He observed that inheritance of grain yield was controlled by additive, dominant

and epistasis genetic effects while, maturity traits were governed by dominance genes only. In

his study duplicate type of gene actions was predominant over complementary type of digenic

non-allelic interaction. Out of inter-allelic interactions dominance × dominance types were more

pronounced than additive × additive and additive × dominance interaction. He suggested

exploitation of heterosis breeding or recurrent selection due to non-adequacy of simple additive-

dominance model for maturity and grain yield.

Zare et al. (2011) observed over-dominance gene effects for days from silking to

physiological maturity, days from anthesis to physiological maturity, plant height, kernel depth,

number of rows per ear and grain yield. Keeping in mind the obtained results reciprocal recurrent

selection was suggested for days from emergence to physiological maturity and number of

kernels per row, having complete dominance. Ear leaf area and ear length were controlled by

partial dominance, indicating that additive gene effects were more important than non-additive

gene effects for controlling the inheritance of these traits.

Vieira et al. (2011) crossed the popcorn inbred lines in a partial circulant diallel mating

scheme and evaluated for grain yield, popping expansion and resistance to southern rust

(Pucciniapolysora, Pp). Significant general combining ability (GCA) effects were obtained for

grain yield, popping expansion and partial resistance to Pp. Based on predominant additive gene

effects they recommended recurrent selection for their popcorn population improvement.

However, none of lines had outstanding grain yield and popping expansion. Specific combining

25

ability (SCA) was detected for grain yield. The P9.24 × P8.6 might be promising for GY, if

exploited using inter-population breeding methods. They recommended the line P8.5 to form

breeding populations against resistance to Pp.

Khodarahmpour (2011a) studied the genetic effects using Hayman-Jinks method. She

observed significant effects for both “a and b” gene effects for all traits in maize germplasm used

in her study. From her study she recorded that grain yield and plant characters were under

control of dominance gene effects while, over dominance and complete dominance for grain

diameter. Similarly additive gene action with partial dominance were observed for ASI, grain

filling period, grain numbers per row, grain number per ear, grain row number in ear, ear

diameter, grain depth, 1000 grain weight and hektolitr weight traits.

Khodarahmpour (2011b) studied the genetic control of grain yield and other related traits

in maize inbred lines using partial diallel fashion under normal and stressed conditions. She

estimated non-additive genetic effects for grain yield and hektolitrweight under both

environments. Similarly she also observed over-dominance and dominant effects other traits.

Ahmet and Kapar (2011) evaluated 18 hybrid genotypes and four commercial popcorn

cultivars at Black Sea Research Institute in Samsun (Turkey) using complete block design during

2006 and 2008. Significant variation were observed among the genotypes for grain yield,

tasseling time, plant height, grain moisture at harvest, percentage of unpopped kernels and

popping volume. Based on their results they selected the genotypes, TCM-05-01, TCM-05-02,

TCM-05-03, TCM-05-04, TCM-05-05, TCM-05-06, TCM-05-09, TCM-05-10, and TCM-05-12

for multi-location yield testing.

Sher et al. (2012) studied the genetic components of flowering characters in subtropical

maize. They evaluated their material comprising six generations viz. P1, P2, F1, F2, BC1 and

BC2in a randomized complete block design with three replications across two years. They

observed that the inheritance of days to pollen shedding silking, maturity and anthesis silking

interval were under the genetic control of both dominant gene action and epistatic interactions.

They concluded that the obtained dominance nature of genetic control can be effectively utilized

in maize breeding programs for the improvement of studied characters.

Khodarahmpour (2011a) studied the genetic effects using Hayman-Jinks method. She

observed significant effects for both “a and b” gene effects for all traits in maize germplasm used

26

in her study. From her study she recorded that grain yield and plant characters were under

control of dominance gene effects while, over dominance and complete dominance for grain

diameter. Similarly additive gene action with partial dominance were observed for ASI, grain

filling period, grain numbers per row, grain number per ear, grain row number in ear, ear

diameter, grain depth, 1000 grain weight and hektolitr weight traits.

Mousa (2014) evaluated a set of twenty three maize genotypes at two locations for

combining ability estimates according to Griffing (1956) Method-4 Model-1. Significant

genotypes x location were observed for majority of the traits. Although both additive and non-

additive gene action were involved in the inheritance of most of traits, however, non-additive

gene action was predominant than the additive gene action. Based on superior performance he

recommended lines P3 and P5 for developing maize hybrids.

According to Dorri et al. (2014) the major important factors involved in selecting

breeding methods and genetic improvement are relative amount of genetic variability and

presence of non-allelic interactions. Generation mean analysis was used for the inheritance study

of grain yield and some agronomic traits. They reported that dominance variance was more

important than additive variance for most of the traits including ear length, number of kernels per

row, kernel depth, 1000 grain weight and days to anthesis. Due to predominant role of dominant

genes they justified production of hybrid varieties in maize.

Chandal and Mankotia (2014) evaluated local CIMMYT germplasm for combining

ability analysis through test cross performance. They obtained negatively significant GCA results

for plant and ear height in four inbred lines while, positive and significant GCA effects were

observed for grain yield and related attributes like, ear diameter, ear length and number of rows

ear-1. The presence of higher general combining ability variance components (σ²GCA) than that

of SCA variance (σ²SCA) for ear length and grain yield indicated involvement of additive gene

action in the inheritance of these traits. They reported that for ear diameter and number of

rows/ear plant height and ear height were under control of non-additive gene actions indicating

their importance over additive gene action in the inheritance of these traits. Environmental

effects on non-additive type of gene actions were supposed to be more than additive effects.

Haq et al. (2014) explained the inheritance pattern and its relative magnitude of genetic

effects for flowering characters using generation mean analysis in maize. Non-additive effects

27

and epistatic interactions were found responsible in governing the inheritance of days to tasseling

and silking. Two and three of the six crosses exhibited that both additive and non-additive

genetic effects were equally controlling inheritance of days to tasseling and silking, respectively.

They also reported duplicate type of epistasis while having significant value with opposite sign

of h and l. They proposed utilization of inbred lines in hybrid breeding program due to

preponderance of dominant gene action for flowering traits.

Sabolu et al. (2014) studied the inheritance of quality traits of eggplant using generation

mean analysis. Using six populations, P1, P2, F1, F2, B1 and B2 significant digenic interactions

were observed for all the characters in majority of crosses studied. Both additive and dominance

genes were responsible in the inheritance of anthocyanin content, glycol alkaloid content, dry

matter content and reducing sugars in some of the crosses. In heritability estimates high broad

sense heritability was reported in most of the crosses for all the quality traits expressing low

magnitude of dominance and environmental variances. After observing duplicate type of

epistasis for many quality traits they suggested mild selection intensity in the earlier and intense

in the later generations because it marks the progress through selection. They emphasized on

exploitation of additive variance for the improvement of eggplant because it makes possible to

select better individuals at gametic level.

Entringer et al. (2014) explained the implications of climate change on leaf curling in

maize. The data was analyzed according to generation mean analysis in which mean and

variances were estimated by the weighted least square method. They found that leaf curling was

under control of additive gene effects that favor selection and exhibit minimal influence from the

environment.

Hussain et al. (2014) conducted a study on genetic analysis for various morphological

traits in maize using a complete diallel fashion under irrigated and drought conditions. Genetic

analysis of maturity, plant and yield related traits exhibited that over-dominance type of

inheritance under both normal and drought conditions. Heterosis breeding was emphasized for

yield and related traits having over-dominance nature of inheritance.

Akhshi et al. (2014) declared that base of efficient breeding procedure is knowledge of

the genetic system controlling a trait. They determined the genetic effects for yield and its

components in two common bean crosses. They reported the adequacy of six parameter genetic

28

model by obtaining significant difference for scaling tests (A, B, C, and D) in both crosses. They

proposed exploitation of heterosis for seed yield as the non-additive genetic effects were

predominant in nature.

Khan et al. (2014) estimated genetic components for various traits in maize under normal

and water stressed conditions. Positive effects of dominance and additive × additive were

achieved for cell membrane thermo stability, stomatal frequency and leaf water potential while

[d] additive effects for leaf water potential under normal conditions. They suggested

development of synthetic variety based on traits having additive and additive × additive

interaction while, hybrid development for traits with dominance genetic effects. They concluded

that based on genetic effects grain yield may be increased under drought conditions in relation

with stomata frequency, stomata size, cell membrane thermo stability, leaf water potential and

excised leaf water loss.

Haddadia et al. (2014) studied the genetic constitution of some agronomic traits in maize

using half diallel mating design. They reported both additive and non-additive gene actions for

plant height, days to silking, ear height, thousand kernel weight, kernel rows ear-1,ear length, leaf

number and grain yield. However, additive genetic effects were of great importance in traits like

days to silking, kernel weight, kernel rows, ear length and ear height due to their high narrow

sense heritability and low degree of dominance.

Hussain et al. (2015) conducted an experiment in full diallel fashion involving eight

maize inbred lines. They observed that quality traits i.e., protein, tryptophan and lysine

percentage were controlled by additive effects with partial-dominance under both normal and

drought stress conditions. Based on the presence of additive gene action and high narrow sense

heritability they proposed an early generation selection for improvement of these traits.

Wannows et al. (2015) conducted an experiment for the inheritance of different traits in

two yellow maize hybrids during three consecutive growing seasons. They revealed that

additive–dominance model as well as non-allelic gene interactions were adequate to explain the

genetic inheritance of most studied traits. Duplicate type of digenic non-allelic actions in most

studied traits for the two crosses were observed. In their studied traits most were under control of

additive and non-additive gene actions, while dominant genes were also found responsible in

some traits. They suggested intensive selection through later generation for improvement of

29

those characters. High heterosis and low narrow sense heritability in most cases were indicative

of dominance of non-additive gene actions.

2.2 Heritability

In crop improvement, the genetic component of variation is very important since only

this component is transmitted to the next generation and therefore responds to selection.

The extent of the contribution of genotype to the phenotypic variation for a trait in a population

is ordinarily expressed as the ratio of genetic variance to the total variance, i.e. phenotypic

variance, for the trait. This ratio is known as heritability. Thus heritability denotes the proportion

of phenotypic variance that is due to genotype, i.e. heritable. Heritability can be estimated by

three different methods: i) from analysis of variance table of a trial consisting of a large number

of genotypes, ii) By estimating the genotypic variance and environmental variance from the

variances of F2, P1, P2 and F1 generations of a cross, and iii) the parent-offspring regression upon

doubling provides an estimate of heritability. Heritability estimated by these three methods is

known as broad sense heritability and it is valid for homozygous lines or homozygous

population. However, when we are dealing with segregating generations, the genetic variance

consists of additive and dominance components (assuming there is no epistasis). Since in cross-

pollinated crops we develop homozygous lines, the dominance component will not contribute to

the phenotype of homozygous lines derived from a population. Consequently, in such cases, only

the additive component of the genetic variance is relevant. Therefore, for segregating

generations, the ratio of additive component of variance to the total phenotypic variance is a

more appropriate estimate of heritability and it is referred as narrow sense heritability.

Twenty one maize genotypes were evaluated by Debnath and Khan (1991) to study

heritability and genetic advance for flowering traits and yield components in maize. They

observed high heritability estimates for days to silk, plant height, ear height and 1000-grain

weight, moderate levels for ear diameter and number of kernels row-1, and low estimates of

heritability for ear length, kernel rows ear-1 and grain yield.

30

Rodrigues and Chaves (2002) studied genetic parameters while, evaluating one hundred

ninety two half-sib families popcorn populations in a randomized complete block design

with two replications at two locations. Sufficient genetic variability was found for grain yield,

poorly husked ear and broken plants evaluated traits, indicating further exploitation of the

material in maize breeding program. High heritability estimate were observed for popping

expansion than for grain yield, the predicted genetic gain for the latter was superior to

popping expansion because of the higher magnitude of the genetic standard deviation for grain

yield. They expected the release of first popcorn variety with yellow grains in the fifth recurrent

cycle for Rio de Janeiro State.

Mahmood et al. (2004) calculated genetic variability, heritability and genetic advance for

flowering, plant and yield characters. Low to high estimates of broad sense heritability were

observed for different plant characters under study. Highest broad sense heritability estimates

were found in grain yield plant per plant and plant height. High heritability estimates for studied

characters indicated that they were under control of additive genetic effects. They guessed a fast

genetic improvement in studied germplasm.

Twenty diverse maize cultivars obtained from various locations within the Ekiti State

were evaluated at Teaching and Research Farm, University of Ado-Ekiti, Nigeria for various

plant traits (Salami et al., 2007). Low levels of heritability in broad sense were estimated for

days to mid anthesis, days to mid silking, plant height and grain yield. From these low levels of

heritability they noticed that perhaps the heritability estimates would have been improved if the

evaluation had been conducted in multiple environments.

Lorenzana and Bernardo (2008) tested maize test crosses of 119 intermated B73 × Mo17

recombinant inbreds in organic and conventional systems at both Waseca and Lamberton, MN,

in 2006. Low heritability was exhibited under organic production system for grain yield and

higher heritability for root lodging, stay green character and ear height. They suggested

screening of conventional inbreds and hybrids for their performance under organic systems.

Abadi et al. (2011) pointed out the importance of combining abilities and genetic effects

in maize hybrid breeding. Test crosses of S6 generation were evaluated in a randomized complete

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block design with three replicates. Additive genetic variance was found to be substantially higher

than dominance genetic variance for all of the traits except, days to physiological maturity. From

obtained results it was indicated that additive gene effects were predominant than dominance

effects in controlling forage yield and some other agronomic traits. As additive genetic effects

were prominent therefore, narrow sense heritability estimates closely resembled the broad sense

heritability estimates except for phenological characters. According to them prevalence of

additive genetic effects and medium to high narrow sense heritability selection would be

favorable for yield improvement.

Olakojo and Olaoye (2011) estimated correlation and heritability of agronomic characters

under artificially infested maize inbred lines with Strigalutea. Moderate to high heritability

estimates were observed for striga emergence count and striga syndrome rating. Similarly low

heritability estimates were obtained for tolerance index, days to tasseling, days to silking, kernel

rows per cob and grain yield. Genetic and phenotypic correlation coefficients of striga

emergence count with other agronomic traits were positively significant. They confirmed that

estimates of heritability and correlation were of prime importance in yield improvement under

stress environments.

Idris and Abuali (2011) assessed genetic variability for vegetative, yield and yield

components in maize. Significant differences were found for plant height, stem diameter, kernel

rows per cob and ear length in first season while, for days to flowering and 100-seed weight in

second season. Maximum heritability estimates were reported for stem diameter and days to

flowering in first and second growing season, respectively. They proposed manipulation of

present genetic diversity of tested populations for further improvement in maize breeding.

S1 lines of maize were evaluated at two locations to study heritability estimates of

maturity and morphological traits (Ali et al., 2012). In this study significant differences were

revealed for all the traits except maturity. Moderate heritability was calculated for maturity traits

while, high heritability for plant characters.

Mhike et al. (2012) studied the genetic control of grain yield and related traits under

irrigated and water stressed environments. High heritability estimates were calculated for grain

32

yield, anthesis silking interval, ears per plant and leaf senescence under drought were higher than

in well irrigated conditions. There was a general decline in heritability from per plot values to

across environment values in all traits except, for anthesis silking interval, ears per plant and leaf

senescence under drought. According to them a real picture of superior hybrids could be

achieved through selection across environments.

Bello et al. (2012) addressed the importance of knowledge regarding magnitude of

genetic variability, heritability and genetic gains in selection for grain yield and related traits.

They reported high heritability estimates and genetic advance for grain yield, number of grains

per ear, ear weight, plant and ear heights. Keeping the evidence of additive gene effects for

studied traits early generation selection was proposed for effective selection and improvement

for studied traits.

Ullah et al. (2013) conducted a trial of half sib families derived from a maize variety

Sarhad White. Maximum broad sense heritability were estimated for plant height, moisture

content and kernel weight while, minimum estimates were observed for days to silking, anthesis

and anthesis silking interval. They suggested use of these half-sib families as source for

improvement of maize germplasm.

Khanmohammadi et al. (2013) measured the performance of maize hybrids using grain

yield, yield components and some of morphological traits. High heritability estimates observed

for grains rows per ear, number of inflorescence branches and days to peak period compared to

other traits. Traits having high heritability could be effectively utilized in breeding programs for

maize improvement. They observed highest direct effect of stem diameter on grain yield and

lowest due to the seed depth.

Noor et al. (2013) evaluated half-sib families through recurrent selection program at two

growing seasons. High broad sense heritability estimates were calculated for grain yield, kernel

rows per ear and ear length in first season while, in second season moderate heritability estimates

were observed for all traits except grain yield. The observed response of grain yield calculated in

first season was greater than the expected one. They validated selection for high grain yield

through its positive value of gain per cycle.

33

Berilli et al. (2013) intimated response to selection by evaluating 242 full-sib families

obtained from CIMMYT and Piranao populations. Although they observed no genotype x

environment interactions still there was a considerable amount of genotypic variability and

heritability. According to them high heritability estimates and correlation coefficient were

important genetic parameters for selection and applying a suitable breeding method.

Shukla et al. (2014) estimated heritability for some yield attributing traits. They observed

a considerable amount of diversity in evaluated germplasm for the studied traits. Heritability

estimates in broad sense ranged from low to high for traits they studied. Low heritability

estimates were calculated for kernel rows per ear and prop root while moderate heritability was

reported for ear length. Maximum genetic improvement was expected to be achieved through

direct selection scheme when heritability and genetic advance were of high magnitude in maize

germplasm.

Sharma et al. (2014) assessed different genetic components including heritability, genetic

variability and genetic advance for grain yield and kernel quality. High heritability and genetic

advance were calculated for most of the traits. They proposed that characters like test weight,

grain yield per plant, grains per cob, cob length, grains per row and harvest index should be

utilized in selection programs for improving maize yield.

Nataraj et al. (2014) estimated broad sense heritability, genetic variability and genetic

advance in 39 inbreds of maize. Data were recorded on twelve quantitative traits viz., days to

tasseling, silking, plant and ear height, ear length, ear diameter, ear weight without husk, ear

weight with husk, number of kernel rows per ear, number of kernels per row, 100-grain weight

and grain yield per plant. High broad sense heritability estimates and genetic advance were found

for grain yield per plant, ear height, plant height, number of kernels per row, number of kernel

rows per ear, ear length, 100 grain weight, ear weight with husk and without husk. Due to high

values of heritability genetic advance and genotypic covariance effective selection was expected

for grain yield improvement.

Aminu et al. (2014) investigated heritability estimates and association of different

agronomic traits in a study conducted at two locations. High heritability estimates were observed

34

for days to tasseling, silking, dehusked cobs and grain yield in combined analysis across

locations. However, they revealed moderate heritability estimates for anthesis silking interval,

plant height, weight of cobs and 100 seed weight, respectively. Heritability estimates and

correlations coefficients were proposed to be best genetic parameters for yield improvement and

selection for drought tolerant genotypes.

Ishaq et al. (2014) estimated heritability estimates and expected responses of maturity

and yield related traits in half-sib families of maize. A variable range of heritability estimates

ranging from low too high was observed for studied traits including days to tasseling, silking,

anthesis, plant and ear height, kernels per row, grain yield, 1000 kernel weight and kernels per

ear. High expected responses were accounted for grain yield 1000 kernel weight, plant and ear

height. They presumed the presence of greater genetic differences among the evaluated half-sib

families.

Kumar et al. (2014a) determined genetic variation, broad sense heritability estimates and

genetic advance in maize genotypes. High broad sense heritability estimates were calculated for

grain yield per plant, plant height, ear height, grains per row and 100-kernel weight whereas,

high to moderate heritability estimates were observed for days to tasseling, silking, maturity,

shelling percentage, ear length, ear girth and number of kernel rows per ear. They suggested that

high heritability accompanied with high to moderate genotypic and phenotypic coefficient of

variation and genetic advance is an indication of additive gene effect due to which selection at

early stages would be effective.

Tengan et al. (2014) obtained high broad sense heritability estimates for cob length, cob

diameter, kernel rows per ear, plant and ear height. Similarly they obtained moderate to low

narrow sense heritability estimates for plant height (24%), ear height (34%) and cob length (4%).

Based on obtained results they suggested that selection should be made in suitable segregating

generations to fully exploit the expression of genes for different traits.

Hussain et al (2015) evaluated eight maize inbred lines and their hybrids in full-diallel

fashion under normal and drought stressed conditions. The inheritance of protein, tryptophan and

lysine percentage was controled additively with partial-dominance under both normal and

35

drought stress conditions. Based on high narrow heritability and additive gene action, they

suggested improvement in maize through early generation selection.

Mukambi et al. (2015) assessed the performance of maize across 17 environments under

Striga-infested and Striga-free conditions. Significant difference and high heritability estimates

were observed among genotypes for grain yield and days to silking in both Striga-infested and

Striga-free conditions. They proposed use of IR OPVs for Striga control and benefiting farmers

with high grain yield.

Abadassi (2015) discussed agronomic traits including earliness, reduced plant and ear

heights, resistance to stalk and root lodging, resistance to diseases, weeds and pests, drought

tolerance, excellent husk cover, high and stable grain yield, high harvest index and appropriate

grain quality of maize for utilizing in breeding programs. A variable range of heritability

estimates from low to moderate and high level was calculated for studied traits. They

emphasized on improvement of tropical maize populations for those traits using suitable

breeding methods.

Kruijer et al. (2015) estimated heritability estimates in maize using high-density markers.

In their methodology the main problem was that software assume a single phenotypic value per

genotype, which they solve using mixed models at individual plant or plot level. In their

heritability estimates they obtained very large standard errors which were biologically

unrealistic. They suggested that mixed models at individual plant or plot level were more

realistic with least standard errors and increased genomic predictions.

Abadassi (2015) emphasized on agronomic characters for grain yield improvement of

maize in tropical zone. These traits included earliness, reduced plant and ear heights, resistance

to stalk and root lodging, resistance to diseases, weeds and pests, drought tolerance, excellent

husk cover, high and stable grain yield, high harvest index and appropriate grain quality. Both

additive and dominance as well as epistatic gene effects were obvious for studied traits. A

considerable variation in heritability estimates was observed for different traits in population,

environment and computation method.

36

2.3 Heterosis

Heterosis, or hybrid vigor, is the increased performance of hybrid progeny compared to

their inbred parents (East, 1908; Shull, 1908). Heterosis is manifested as increased size, growth

rate, and other parameters in the F1 generation in crosses between inbred lines (Tollenaar et al.,

2004). Exploitation of heterosis is largely responsible for the tremendous increase in maize yield

in the United States between the1930’s and the 1970’s (Duvick, 2001). Despite the importance of

heterosis, the molecular basis of this phenomenon is unclear (Birchler et al., 2003; Springer and

Stupar, 2007).

In crosses between broad base maize populations by Rezende and Souza (2000), a much

lower expression of heterosis was indicated for grain yield, 6.05%, 7.38%, 8.50% and 8.80%,

respectively. Sheoran et al. (2000) evaluated six generations (P1, P2, F1, F2, BC1 and BC2) of a

cross between two diverse parents in Pearl millet for plant height, girth and length of ear head,

1000-grain weight, days to flowering and grain yield. Positive and significant heterobeltiosis was

found for all traits they studied except, for days to flowering.

Kara (2001) evaluated 18 F1 maize hybrids along with three male testers and six female

inbred lines in line x tester approach for yield and yield components. It was observed that

average heterosis was positive and significant for all the parameters except for days to tasselling.

It was further noticed that hybrids yielded 79.8% above than that of parents yield. Mickelson et

al. (2001) evaluated nine maize populations and their diallel crosses at five Mexico, Zimbabwe

and U.S. locations and observed low to moderate levels of high parent heterosis for grain yield.

Eight inbred lines from diverse geographical regions of India were crossed in all possible

pairs, and F1s were evaluated for yield and yield components in a replicated trial in two

environments (Mohammadi et al., 2002). High heterotic values were observed for yield

compared to its components (100 grain weight and number of kernels ear-1). It further revealed

the importance of over dominance gene action in maize for the expression of heterosis for yield

and its components.

37

To determine heterotic effects for grain yield in maize Koirala and Gurung (2002) studied

7 x 7 population diallel crosses and observed high parent heterosis for grain yield in maize of -

17.8% to 23.9% among population crosses.

Rodrigues and Chaves (2002) investigated heterosis in high quality protein maize

populations of distinct grain type groups. The germplasm was assessed for agronomic traits and

resistance to some leaf diseases in a partial diallel grown at four environments. Significant

genetic effects were observed for mid parent heterosis of grain yield. They recommended the BR

473 and CMS 52 flint populations, the CMS 474 and ZQP 103 dent populations for an inter-

group reciprocal recurrent selection program, while the dent type CMS 474, ZQP 103 and ZQP

101 populations and the flint type BR 473, CMS 455C, CMS 453, CMS 52, CMS 455 and CMS

458 were recommended to form composites.

Dickert and Tracy (2002) crossed six open pollinated varieties of sweet corn in a diallel

fashion to study heterosis and moderate levels of mid-parent heterosis in plant height (9.0%), ear

height (8.6%), ear length (12.9%) and 100-grain weight (10.0%). Very small heterosis was

observed for days to silking indicating that none of the hybrids exhibited earliness than earliest

parental lines.

Rasmussen (2003) intermated twelve improved maize populations including 8 US. Corn

Belt populations and 4 adapted exotic populations and evaluated for both cultivar and among

crosses agronomic performance. High mid-parent heterosis occurred in the BSSS (R) C14 (Reid

yellow dent) x BSCBI (R) C14 (Landcaster Sure crop) cross (73%) with an average yield of 7.53

ha-1.

Tollenaar et al. (2004) evaluated twelve F1 maize hybrids and their 7 parental inbred lines

for grain yield and its component processes, dry matter accumulation (DMA) at maturity, and the

partition of DMA to the grain (i.e., harvest index), as well as in terms of the physiological

processes under lying those two components. High mid parent heterosis was observed for dry

matter accumulation (DMA) and grain yield. Moderate levels of heterosis from 53-58% were

exhibited, respectively by harvest index and dry matter accumulation (DMA) at 14 leaf stage.

They further noticed that days to silking, days to maturity and ear m-2 showed negative heterosis

38

of low levels, whereas heterosis in 1000 kernel weight, however, was of low level but with

positive magnitude.

Soengas et al. (2006) crossed 10 flint maize varieties with two testers (flint and dent) in a

diallel mating design. The objective of their study was focused on developing hybrids to exploit

heterosis between flint and dent germplasm in the Atlantic Coast of Europe. They observed that

two varieties, Gallego and Norteno when crossed with flint inbred line EP42, exhibited

intermediate variety heterosis for adaptive traits like days to silking and kernel moisture at

harvest.

Pajic et al. (2006) started a strategy for selection and improvement of white grain

popcorn. Eight selected populations were evaluated for combining ability and heterosis of plant

height, ear height, grain yield and popping expansion in northwest region of Paraná. The base

populations, the F1 and five controls were evaluated in Maringá, state of Paraná, across two

years. Very low heterosis was calculated for popping expansion and suggested intra-population

selection in BRS Angela and SC 002, to raise the values of popping expansion up to commercial

levels. Similarly for reduction in plant an ear height they proposed and intense inter-population

selection.

During evaluation of F1 crosses derived from four genetically diverse maize inbred lines,

Uzarowska et al. (2007) observed substantial mid-parent heterosis (MPH) for plant height

ranging from 37.9% to 56.4% in the field and 11.1% to 39.5% under controlled green house

conditions.

Springer and Stupar (2007) reviewed the allelic variation in maize and its effect on

heterosis. It has been documented that intraspecific comparisons of sequence and expression

levels in maize has high level of allelic variation, which includes variation for the content of

genic fragments, variation in repetitive elements surrounding genes, and variation in gene

expression levels. The combination of allelic variants provides a more comprehensive suite of

alleles in the hybrid that may be involved in novel allelic interactions. They proposed that it is

still ambiguous that how the combined allelic variation and interactions in a hybrid give rise to

heterotic phenotypes.

39

Pajic et al. (2008) studied popping volume and yield of popcorn inbred lines in diallel

matting system. Analysis of variance of genetic components for popping volume indicated that

the additive as well as dominant components significantly affected the inheritance of this trait in

popcorn. Both additive and non-additive gene effects were found responsive for grain yield in

their study. They suggested that it is difficult to obtain superior genotypes for both traits but it is

possible to develop genotypes with good popping volume and satisfactory yield.

Flint-Garcia et al. (2009) generated about three hundred hybrid genotypes by crossing the

inbred lines from an association mapping panel to a common inbred line, B73. Heterotic effects

were calculated for seventeen phenotypic traits at multiple environments, and found better-parent

heterosis in majority of hybrids. They suggested that the genetic basis of heterosis is trait-

dependent due to weak correlations between the levels of heterosis for different traits.

Vieira et al. (2009) evaluated hybrids and self’s of six popcorn populations. Highly

significant effects were obvious for treatments, varieties and mean heterosis for plant and ear

heights and for the others traits.

Iqbal et al. (2010) meditated heterosis for morphological traits in maize crosses between

inbred lines of contrasting maturities and plant heights across two years. Significant better-parent

heterosis were observed in all the crosses, similarly mid-parent heterosis was also significant for

all traits in all crosses except one cross. They suggested Pop9804xFRW4 as the best hybrid

combination for early maturity and high fodder yield.

Dhasarathan et al. (2012) evaluated twenty one baby corn single cross hybrids along with

their parents for the exploitation of heterosis and heritability. High heterotic effects were

observed for plant height, number of baby corn per plant, baby corn weight, baby corn yield per

plot, reducing sugars and non-reducing sugars. For most of the traits they found high heritability

coupled with genetic advance, indicating a substantial amount of genetic variation in this

population of hybrids. They recommended the hybrids FDM 7 x FDM 14 due to its high genetic

potential and heterosis for certain important characteristics of baby corn.

Aghaei et al. (2012) studied the effect of water deficiency on morphological traits and

average heterosis, in maize hybrids and their parental lines at Agricultural and Natural Resources

40

Research Center of Moghan. Significant differences across environment were exhibited among

genotypes for all the traits. Highest amount of heterosis for grain yield and yield components in

both conditions was observed for single cross 704 (SC704) derived from a cross between MO17

and B73 inbred lines. They proposed SC704 as a suitable hybrid for Moghan region and water

limited conditions.

Shahrokhi and Khorasani (2013) evaluated six generations (P1, P2, F1, F2, BC1 and BC2)

of an early mature hybrid, SC.400 (KE72012 (P1) × K1263/1(P2)), and a late mature hybrid,

SC.704 (B73 (P1) × MO17 (P2)) maize (Zea mays L.), in a RCBD with three replications in

saline and normal environments. The results showed significant differences between generations

both in normal and saline conditions. They observed higher forage yield (88.106 and 60.734

ton/ha in normal and saline conditions, respectively) for the ’BC1 SC.704’ generation (B73 ×

SC.704).

Hussain and Ali (2014) conducted a maize trial to study heterosis and gene action for

days to tasseling, silking, flag leaf area, plant height, number ofrows per ear, number of grains

per row, grain weight and grain yield in two sowing dates. Hybrids were found to have more

genetic variability as compared to their parents. Studied characters were shown to be effected by

over-dominance effects of some genes. Highest heterosis was exhibited by the three hybrid

combinations viz. 1×6, 2×6, 3×4, 3×5 and 3×7 for most of the studied characters at both sowing

dates.

Jain and Bharadwaj (2014) highlighted the importance of degree and direction of hybrid

vigor for its commercial exploitation in quality protein maize. A marked variation was shown in

the expression of standard heterosis for yield and its related characters. Significant and positive

standard heterosis was manifested for grain yield in three crosses. Similarly highest heterotic

effect among the yield components was recorded for number of cobs per plant, followed by cob

length, grain rows per cob and cob weight, respectively. Selection of best parents was found to

be the most important criteria for developing high yielding quality protein maize hybrids.

41

2.4 Correlation

Correlation is an important genetic parameter which is extensively exploited in maize

breeding programs. The expression of a character in a plant is the consequences of a chain of

inter relationships between two or more variables, either directly or through other events.

Correlation studies pave the way to know the associations prevailing between highly heritable

characters with most economic characters. Correlation coefficient analysis helps to determine the

nature and degree of relation between any two measurable characters. Phenotypic correlation

reflects the observed relationship, while genotypic correlations underline the true relationship

among the characters. Knowledge on these will be of immense help in the selection of suitable

plant types.

Sujiprihati et al. (2003) evaluated single crosses derived from (12 × 12) half diallel

crosses in maize inbred lines and observed positive and significant correlation of grain yield

combined and or individual location analysis with plant and ear height, ear weight, ear length,

ear diameter, number of kernels row-1 and 100-grain weight while it was positive but non-

significant with kernel rows ear-1 and shelling percentage. The relationship of yield was

significant but negative with maturity characteristics (days to tasselling, days to silking and days

to maturity). Plant height and ear height showed highly significant and positive correlation with

almost all the characters studied. They also added that flowering characteristics were negatively

correlated with ear characteristics and shelling percentage. The relationship among ear

characteristics remained positive.

Rafique et al. (2004) studied the correlation of grain yield and its components in 49 maize

hybrids and 14 parental lines. Kernels per row was highly positively correlated with grain yield,

followed by plant height, ear height, length and its diameter. They found high heritability

estimates for all parameters showing heritable variation among genotypes. Heritability for

kernels per row, plant height and grain yield per plant was higher than the other characters.

Highly positive and significant association between days to tasseling and silking was

found while evaluating 47 diverse maize genotypes collected from CIMMYT (Sumathi et al.,

2005). These flowering characteristics were positively and significantly related with plant height

42

and 100- seed weight, while with grain yield, number of rows ear-1, number of kernels row-1 and

number of kernels ear-1, the relationship recorded was negative. They observed positive and

significant relationship of ear weight with kernel rows ear-1, kernels row-1 and grain yield while

with 100-seed weight it was significant but negative. Furthermore, the relationship of grain yield

plant-1 was significant and positive with all the yield associated traits except with 100-seed

weight which was significant but negative in nature.

Malik et al. (2005) disclosed the genetic correlation among grain yield and some

quantitative characters. They revealed a positive genetic correlation of grain yield with plant and

ear heights, leaves per plant, leaf length, width and area, ear weight and kernels per row.

Likewise, negative correlation of days to silking & tasselling and grain moisture content at

harvest was observed with grain yield. Due to a strong positive correlation among plant height,

leaf area, leaves per plant, ear weight, kernels per row and grain yield they suggested utilization

of these traits for improving maize grain yield.

Arnhold et al. (2006) studied the genetic correlations of the popping expansion, hundred

kernel weight, grain production and proportion of ears attacked by pests and diseases. They

evaluated 106 families of popcorn and observed a positive association between popping

expansion and grain production. They reported that ears with high pest incidence were positively

associated with grain disease damages. Based on their obtained results, they proposed

simultaneous selection for yield and popping expansion due to the presence positive correlation

between them.

Zaidi et al. (2007) studied association between line per se and hybrids performance under

excessive soil moisture stress in tropical maize. Across moisture regimes, they observed that all

morpho-physiological traits including plant height, days to 50% anthesis, days to 50% silking

and plant maturity had positive and significant correlation with mid parent traits.

Iqbal et al. (2009) unveiled the genetic and phenotypic correlations among physiological

traits in maize. Six generations viz. P1, P2, F1, F2, BC1 and BC2, derived from 4 maize inbred

lines were used in this study of association. They reported negative non-significant correlation of

leaf area with days to flowering and maturity. Significant association of plant height with days to

43

flowering and maturity was reported, while flowering and maturity traits were positively and

significantly correlated. Based on the results they suggested selection of lines with broader

leaves, early flowering and maturity for fodder purposes.

Bocanski et al. (2009) proposed that due to complex inheritance and low heritability of

grain yield and other economic traits in maize, it is of prime importance to have knowledge of

both genotypic and phenotypic coefficients of correlation. They studied the relationship between

grain yield and morphological traits while, conducting an experiment on eight inbred lines and

their hybrids and observed genetic and phenotypic correlations between grain yield and other

studied traits, except between grain yield and number of kernel row. Genotypic and phenotypic

coefficient of correlation between ear length and cob weight were found highly significant.

A trial conducted by Rafiq et al. (2010) revealed significant genetic correlation among

yield characters like ear diameter, ear length, hundred grain weight, kernel rows per ear and

grains per row in maize. Based on results of path analysis, they reported that highest direct effect

on grain yield was exhibited by hundred grain weight followed by kernel rows per ear, grains per

row, ear length and ear diameter. They reported that most of the traits had positive indirect

effects on hundred grain weight, grains per row and kernel rows per ear.

Ngugi et al. (2013) evaluated maize germplasm in drought stress conditions of Kenya in

an alpha lattice design of three replications. Anthesis silking interval (ASI) was found negatively

correlated with grain yield stress tolerance index, geometric mean productivity, mean

productivity and yield stress index. ASI was significantly positively correlated with stress

susceptible index. They extended the probability of combining high yielding, early maturing and

drought tolerant maize for arid and semi-arid areas of Kenya.

Khalili et al. (2013) studied the effect of drought stress on association of grain yield and

related traits in maize. Highest correlation of grain yield was found with kernel rows per ear and

grains per ear both under control stress conditions. They also found a positive and significant

association of harvest index, kernel rows per ear, grains per ear, grains per row and 100 grains

weight with yield under stress. The genetic correlations between grain yield and related traits

was partitioned. Grain yield was effected positively by biological yield, grains per ear and 100

44

grains weight while, plant height, harvest index, grains per row and kernel rows per ear showed

negative direct effect on grain yield. Biological yield and plant height showed a highest and

lowest direct effect, respectively. They suggested that hundred grains weight, grains per ear

should be used as target traits for improvement of maize grain yield under drought stress.

Direct and indirect effects of both genetic and phenotypic association among yield

attributes were investigated by Munawar et al. (2013) through path analysis. They obtained

positively significant genetic and phenotypic correlation of grain yield with cob position, rows

per cob and grains per row. Positive direct effects of cob height, number of grains per row, stem

diameter and cob girth were reported on grain yield while, cob position showed negative direct

effect on grain yield. They proposed that cob position, kernel rows per cob and grains per cob

might be exploited as reliable criteria for improving grain yield.

Positive and significant correlation of grain yield with flag leaf area, ear diameter,

number of kernel rows per ear, number of kernels per ear row and 100-grain weight was found

both at genetic and phenotypic levels Zeeshan et al. (2013). They found that traits showing

significant positive correlation with grain yield, like flag leaf area, ear diameter, number of

kernel rows per ear, number of kernels per ear row and 100-grain weight, were also having

positive direct effects on the grain yield. From such results they indicated that direct selection

for these traits will be responsive for the improvement in grain yield per plant. They obtained

negative direct effects of plant height, number of leaves per plant and grain on grain yield.

Amini et al. (2013) studied the association of grain yield and its components in maize

using six generations. High genetic associations were obvious than phenotypic for most of the

traits studied. A positive correlation of grain yield was observed with plant height and yield

components while, negatively significant correlation were also found among ear seed weight and

seed yield through large negative indirect effects on other yield components.

Kwaga (2014) studied correlation of grain yield with other characters in a field trial

conducted at Mubi, Nigeria. Associations of grain yield with plant height, cob length, cob

diameter and 100 grains weight were positive while, negative correlation was calculated between

yield and days to tasseling.

45

Azam et al. (2014) conducted an experiment to study correlation and path coefficient

analysis of yield and some other traits in maize. Positive and significant correlation of yield per

plant was observed with cob diameter and grains per row. Contrastingly negative correlation of

yield per plant was also found with ear height and days to mid-tasseling. Highest direct and

positive effect was observed for rows per cob. They suggested that being directly correlated cob

diameter, rows per cob, grains per row and ear height should be kept in mind for an effective

selection.

Bekele and Rao (2014) estimated heritability, genetic advance and correlation in maize

under rainfed conditions in two growing seasons. Along with a negative and significant genetic

association between grain yield and oil content high heritability estimates were calculated for

plant height, ear height, number of seeds per row, 100 seed weight, protein content and grain

yield. They proposed that characters like plant height, grain yield per plot and protein content

should be used for effective selection based on their high genetic advance coupled with high

heritability.

Dugje et al. (2014) evaluated the performance of multi-stress tolerant maize varieties in

Nigeria over two growing seasons. Positive and significant correlation was reported between

maturity and plant characters while, ears per plant was negatively correlated with ear weight.

Similarly grain yield was positively correlated with ears per plant, flowering traits, and ear

height. They viewed that selection criteria used by farmers of the acceptance of any variety

include Striga tolerance, nutrient value, drought tolerance, flour value, good taste, high yield and

early maturity.

According to Kumar et al. (2014b) maize grain yield per plot was positively associated

with plant and ear height, ear length, ear girth, kernels per row, kernel rows per ear, hundred

kernel weight, days to maturity and shelling percentage. They observed negative association of

grain yield with days to tasseling and silking. They reported that largest direct effect on grain

yield at phenotypic level was due to 100-kernel weight followed by number of kernels per row

and ear girth while, days to tasseling, silking and maturity revealed a negative direct effect on

grain yield.

46

Nzuve et al. (2014) determined the genetic control of inheritance of grain yield and

related agronomic traits in maize F1 hybrids along with their parents at three locations in Kenya.

Positive correlation of grain yield was found with ear and plant height, indicating better grain

yield for taller plants compared to stunt one. Taller plants were suggested to have high dry matter

accumulation due to which they produced better yield. They proposed development of

composites and synthetics exploiting positively related traits in further breeding programs for

resource constrained maize farmers.

Abdullah et al. (2015) compared morphological characters in an experiment on maize

crop planted in two consecutive seasons. Correlation analysis revealed that grain yield was in

strong correlation with 100 grains weight, number of grains per ear and number of grains per row

in both years.

Ohunakin and Abedisi (2015) studied partitioning of assimilates in relation to grain yield.

They recorded data on phenology (percentage emergence, days to anthesis, days to silking and

days to grain harvest); plant characters (plant height, number of leaves, leaf area and stem girth);

total nitrogen uptake and yield (plant wet weight, plant dry matter, cob weight and total seed

weight). The association of paired parameters was calculated, and it was found that intra-

parameter correlations from plant growth, phenology and yield as well as paired inter-parameter

correlations between plant growth and yield were positively correlated. Negative correlation was

found between phenology and growth parameters, and between phenology and yield characters.

Bello (2015) studied genetic components, heterosis and correlation among different traits

in maize. Positively significant correlations were reported between grain yield with maturity,

Plant and yield related traits. It indicated that these traits could be used indirectly for the

improvement of grain yield. They calculated 19.4% regression coefficient for all agronomic

characters contributing to grain yield of maize. They confirmed that genetic parameters like

genotypic and phenotypic correlation coefficients, combining abilities, heterosis and regression

analyses were suitable models for yield improvement in maize breeding.

47

Chapter 3

MATERIALS AND METHODS

3.1 Screening for parents selection

The experiment was started by screening eight inbred lines for maturity and yield

parameters in the experimental area of maize section at Cereal Crops Research Institute (CCRI),

Pirsabak, Nowshehra, Khyber Pakhtunkhwa in summer 2011. Four of these inbred lines (PS-1,

PS-3, PS-4 and PS-2) were developed from indigenous germplasm while, other four inbred lines

(BD-1, BD-3, BD-2 and BD-4) were from extraneous (Bangladesh) germplasm (Table 3.2).

These inbred lines were planted on two different sowing dates at CCRI in 2012 maize season.

Significant differences were observed for days to tasseling, silking, anthesis and grain yield

among the evaluated inbred lines. Based on flowering traits and grain yield, four parents (P1, P3,

P5 and P8) were selected for next generation while the remaining inbred lines were excluded

(Table3.4). The selected parents had clustered into two groups (Group I= P1& P3 while Group

II= P5& P8) for days to silking, tasseling and anthesis while for grain yield the grouping had

reshaped (Group I= P3& P5 while Group II= P1& P8). Group I took least days to tasseling (47.67

and 48.00 days), silking (50.0 and 50.33 days) and anthesis (52.00 and 52.00 days) for P1 and P3,

respectively as compared to group II with 52.00 and 52.33 days to tasseling, 55.00 and 55.33

days to silking and 56.33 and 57.33 days to anthesis for P5 and P8, respectively. Based on yield,

the most important parameter for selection, group I excelled with a yield of 3399.67 and 3330.67

kg ha-1 for P3 and P5 while group II lagged by 2502.00 and 2464.33 kg ha-1 for P8 and P1,

respectively. Parents, that were excluded from the selection had lower yield than 1757.33 kg ha-1

(Table 3.3).

Table 3.1 Mean square values of days to tasseling (DT), silking (DS), anthesis (DA) and

grain yield (GY)

SOV DF DT DS DA GY

Rep 2 4.63 4.17 2.79 44656.63

Gen 7 84.99** 94.28** 85.88** 1580421.23**

Error 14 1.96 1.69 1.51 32296.20

Total 23

48

Table 3.2 List of popcorn inbred lines used in selection of parental material

S. No Genotype Crop Maturity Salient Features

1 PS-1 Early Developed at CCRI, Pirsabak from indigenous material

2 PS-3 Late Developed at CCRI, Pirsabak from indigenous material

3 PS-2 Early Developed at CCRI, Pirsabak from indigenous material

4 PS-4 Late Developed at CCRI, Pirsabak from indigenous material

5 BD-1 Medium Developed at CCRI, Pirsabak from exotic material

from Bangladesh

6 BD-3 Late Developed at CCRI, Pirsabak from exotic material

from Bangladesh

7 BD-4 Late Developed at CCRI, Pirsabak from exotic material

from Bangladesh

8 BD-2 Medium Developed at CCRI, Pirsabak from exotic material

from Bangladesh

Table 3.3 Mean values for days to tasseling (DT), silking (DS), anthesis (DA) and grain

yield (GY).

Parents DT DS DA GY (kg/ha)

PS-1 47.67 d 50.00 d 52.00 c 2464.33 b

PS-3 60.67 a 63.33 a 63.00 a 1722.33 c

PS-2 48.00 d 50.33 d 52.00 c 3393.67 a

PS-4 57.00 b 60.67 b 63.33 a 1757.33 c

BD-1 52.00 c 55.00 c 56.33 b 3330.67 a

BD-3 59.00 ab 62.33 ab 63.67 a 1746.67 c

BD-4 60.33 a 63.33 a 65.00 a 1644.00 c

BD-2 52.33 c 55.33 c 57.33 b 2502.00 b

49

The genetic material selected as parents in this experiment comprised a set of four inbred

lines of popcorn. Two of the four inbred line were of Bangladeshi origin and the other two were

developed in Cereal Crops Research Institute, Pirsabak (Table 3.4). Six generations including

two Parents, F1, F2, BC1 and BC2 were developed in two growing seasons for each cross by using

manual pollination procedure of crossing and selfing as described by Russell and Hallauer

(1980).

3.2 1st year spring season: Development of F1 generations

During the first growing season (Spring, 2012), the four parents were crossed with

each other to produce F1 hybrids as given below (Table 3.5).

3.3 1st year kharif season: Development of F2 and back cross (BC1& BC2) generations

Part of seed from each inbred line and their resultant F1 hybrid were grown in the

field during summer 2012 for the production of F2, BC1 and BC2 generations. F2

generation of each cross was produced by selfing each F1, while BC1 (Table 3.6) and BC2

(Table 3.7) generations were developed by crossing F1 with their male and female

parents, respectively.

Table 3.4 Pedigree of the selected parental inbred lines

S.No Name Code Pedigree Maturity

1 P-1 PS-1 PS-PS-1 Early

2 P-2 PS-2 PS-29-2-1 Early

3 P-3 BD-1 BD-POP-1-2-3-3 Moderate

4 P-4 BD-2 BD-POP-2-1-2 Moderate

50

Table 3.5 F1 hybrids after crossing inbred lines

S.No Female Male

1 P-1 × P-3

P-1 × P-4

P-2 × P-3

P-2 × P-4

2

3

4

Table 3.6 BC1 Generations

S.No Female Male

1 (P-1 × P-3) × P-1

2 (P-1 × P-4) × P-1

(P-2 × P-3) × P-2

(P-2 × P-4) × P-2

3

4

Table 3.7 BC2 Generations

S.No Female Male

1 (P-1 × P-3) × P-3

(P-1 × P-4) × P-4

(P-2 × P-3) × P-3

(P-2 × P-4) × P-4

2

3

4

3.4 Field Evaluation

The material comprising 20 entries including four each of parents, F1, F2, BC1 and BC2 were

evaluated in triplicate using randomized complete block (RCB) design at Cereal Crops Research

Institute Pirsabak, Nowshera and The University of Agriculture (UOA), Peshawar, Pakistan

during summer (July-October) 2013. The plot size varied for different generations where the

non-segregating P1, P2 and F1 generations were planted in one row while F2, BC1 and BC2

generations were sown in four rows each. Row length, row to row and plant to plant distances

were kept 5, 0.75 and 0.25m, respectively. To maintain a population of 53,333 plants ha-1, two

51

seeds hill-1 were planted, which were thinned to single plant hill-1 at 3-4 leaf stage. A uniform

fertilizer dose of 200 kg N, 90 kg P2O5 and 90 kg K2SO4 was applied to maintain desired fertility

level in the field. Whole P2O5 was applied in the form of Single Super Phosphate (SSP) and

potash as sulphate of Potash and half N in the form of urea was applied just before planting

during land preparation, while remaining N was applied after three weeks of emergence. As a

pre-emergence control measure for insect damage, seeds were treated with Confidor WP-60

before planting and by application of Furadon granules (3%) one month after planting by

applying in the leaf whirls. Weeds were controlled through application of Primextra Gold @ 600

ml ha-1. Need based hand weeding and other cultural practices were also carried out for weed

control after four weeks of emergence. The crop was irrigated as and when required. Data were

recorded in each plot in each replication on ten plants in P1, P2 and F1, while 20 plants were used

for data recording in F2, BC1 and BC2. Data were recorded on the following parameter as

mentioned below.

1. Days to 50% tasseling

Data regarding days to 50% tasseling were recorded through regular visits of the field and

days were counted from sowing to the day when 50% of the plants produced tassels in each plot.

2. Days to 50% anthesis

Data regarding this parameter was recorded by counting the days from date of sowing till

50% of the plants started shedding pollen in each plot on visual observation by regular visits.

3. Days to 50% silking

Silking data was recorded as the number of days from sowing until 50% of the plants in

each plot when the first silks became visible over the upper ear on plants.

4. Anthesis silking interval (ASI)

ASI was calculated as the difference in number of days to 50% pollen shedding to 50%

silk emergence using the following formula (Ofori et al., 2015):

52

anthesis 50% toDays- silking 50% toDays = ASI

5. Plant height (cm)

Plant height was recorded on ten randomly selected plants in each plot of P1, P2 and F1

with the help of measuring rod as the distance in cm from base of the plant to node of flag leaf,

while twenty plants were taken into consideration in F2, BC1 and BC2.

6. Ear height (cm)

Ear height was measured in cm through measuring rod from ground level to node bearing

the upper most ear. Ten randomly selected plants were averaged for each plot in P1, P2 and F1,

while twenty plants in F2, BC1 and BC2.

7. Days to maturity

Days to maturity were recorded as the number of days from planting to maturity when a

black layer was observed in the grains of the mid portion of the ear.

8. Fresh ear weight at harvest (g)

Ear weight was taken at harvest by weighing the individual ear in grams with the help of

weighing balance.

9. Grain moisture at harvest (%)

Moisture content of grains was determined at the time of harvest by grain moisture tester

after shelling of the middle rows in randomly selected ears.

10. Shelling percentage

Grains from 10 randomly selected ears of each treatment were shelled after drying and shelling

percentage was calculated following John (1991).

100cobs) of Weight + grains of(Weight

grains ofWeight =(%) Shelling

11. Ear diameter (cm)

53

Ear diameter was measured from 10 and 20 randomly selected ears, respectively for

parents and F1 and back crosses and F2 with the help of a verniercalliper for each plot and

average data were subjected to statistical analysis.

12. Ear length (cm)

Ear length of the above selected ears from each generation was measured with the help of

measuring tape and the average length was used for analysis.

13. Kernel rows ear-1

Ten ears in each plot were randomly chosen and the number of kernel rows ear-1 was

counted.

14. Kernels row-1

Grains on each of the randomly selected ears were counted and converted into average

kernels row-1 in each plot (John, 1991).

15. Kernels ear-1

Grains from randomly selected ear were shelled, counted and then averaged.

16. 100 Kernel weight (g)

Weight of 100 kernels from each of selected ear was weighed separately in each plot and

converted into average kernel weight 100-1 grains in grams.

17. Grain yield (Kg ha-1)

The grain yield of each plot was calculated in tones after harvesting and adjusting fresh

ear weight to 150 g kg-1 grain moisture (Carangal et al., 1971) using the following formula:

AreaPlot 15) - (100

10,000 efficient -Co Shelling FEW MC)-(100 ha Kg YieldGrain 1

-

Where,

54

MC = moisture content (%) in grains at harvest

FEW=Fresh ear weight (kg) at harvest

Shelling Co-efficient = Shelling percentage/100

18. Biological yield

Biological yield was measured by harvesting the whole plot and weighed at the time of harvest.

This data were utilized to calculate biological yield ha-1.

19. Harvest index

Harvest index was calculated by following Tollenaar et al. (2004).

100Yield Biological

YieldGrain = (%) HI

20. Expansion volume

Expansion volume = [Total popped volume (cm3)] / [Original sample weight (g)] (Ahmet and

Kapar, 2011).

21. Percentage of unpopped kernels

Percentage of unpopped kernels = (Number of total unpopped kernels/Original number of

kernels) x 100 (Ahmet and Kapar, 2011).

3.5 Statistical Analysis

Combined analysis of variance (Gomez and Gomez, 1983) procedure for randomized complete

block (RCB) design for two locations was used to estimate components of variance using computer

program SAS and to detect if significant variations existed among generations for the standard plant

parameters. The format of analysis of variance is given below in Table 3.8:

55

Table 3.8 Analysis of variance for generations combined across locations

Source of variation Degree of freedom

Locations l-1

Reps (Loc) l(r-1)

Genotypes g-1

Genotypes x Location (g-1)(l-1)

Pooled error l(g-1)(r-1)

Total rlg-1

To determine the mode of inheritance and magnitude of gene action for yield and

popping expansion in popcorn germplasm, generation mean analysis was applied on parameters

showing significant variations among generations. This analysis was accomplished in several

steps.

1) Generation mean for each trait, showing significant differences among generations in the

combined analysis of variance was calculated from the two locations data, using Microsoft Excel

computer program.

2) For a given trait, each generation mean was expressed in terms of its genetic effects, using the

following equation suggested by Hayman (1958).

Ḡ = m + αa + βd + α2aa + 2αβad + β2dd

Where Ḡ = observed mean for generation; m = mean effect; a = average additive effects; d =

average dominance effects; aa = average interactions between additive effects; ad = average

interactions between additive and dominance effects; dd = average interactions between

dominance effects, α and β are the coefficients of a and d which are listed in Table 3.9 below.

56

Table 3.9. Coefficients of and utilized for the construction of different models in

generation means analysis.

Generation

Genetic effects

m a d aa ad dd

P1 1 1 -0.5 1 -1 0.25

P2 1 -1 -0.5 1 1 0.25

F1 1 0 0.5 0 0 0.25

F2 1 0 0 0 0 0

BC1 1 0.5 0 0.25 0 0

BC2 1 -0.5 0 0.25 0 0

3) Weights were calculated for each generation; the appropriate weight being the reciprocals of

the squared standard errors of each mean (Mather and Jinks, 1971).

4) With the set of equations obtained in step 2 and considering the weights associated with each

generation, genetic effects were estimated by the method of weighted least squares (multiple

linear regressions) by utilizing matrix algebra as described by Rowe and Alexander (1980).

Briefly, these three matrices were defined as: W (weights matrix), X (matrix of coefficients of

genetic effects) and Y (column vector of observed generation means). The estimates of genetic

effects were derived from the column vector β, defined as: β = (X2WX)-1(X2WY).

5) Standard error associated to each estimate of a genetic effect was obtained as the diagonal

elements of the solution equation 2-1(XX) = )SE( , where σ2 is the error variance, estimated

by the mean square of the two years average (Frank and Hallauer, 1997).

6) Significance of each genetic effect estimate was evaluated as described by Snedecor and

Cochran (1989), utilizing a t-test.

7) In order to test the adequacy of the model, chi-square (χ2) tests was performed as outlined by

Rowe and Alexander (1980).

Steps 3 to 7 were accomplished utilizing the Microsoft Excel computer program.

The joint scaling test (Cavalli, 1952) was used to detect epistasis for both traits measured. In the

presence of epistasis, additive (a), dominance (d) effects and non-allelic interaction components

(aa, ad, and dd) of generation means were estimated to explain the inheritance of various traits,

57

using Mather and Jinks (1971) model. A three parameter model also known as additive-

dominance model was used to explain genetic variability for those traits which show non-

significant values for chi-square (χ2). By observing a significant χ2 value, a six parameter model

was used to accommodate the digenic epistatic interactions.

The parameters in the three and six models were:

a) Parameters used in both the models.

m = the mid-parent value of the F2 means.

d = amount of variation among the means resulting from the additive effects.

h = amount of variation among the means resulting from the dominance deviations.

b) Parameters used in model 2 in addition to m, a, and d.

i = amount of variation among the means due to the additive × additiveepistatic effects.

j = amount of variation among the means due to additive × dominanceepistasis.

l = amount of variation among the mean resulting from dominance × dominance epistasis.

Heritability estimates

Broad sense and narrow sense heritability were calculated from the variances of

segregating and non-segregating generations on average data from two locations, using the

formula suggested by Warner (1952).

2

31212

BS2

VF

))(VF)(VP(VP-VF=h

Where,

VF1, VP1 and VP2 = the variances of non-segregating generations i.e. parent 1, parent 2 and F1,

respectively.

VF2 = the variance of F2 generation.

58

Heritability in narrow sense

VF

)VBC + (VBC -2VF = h

2

212NS

2

Where,

VF2 = the variation of F2 generation

VBC1 = the variation of back cross with parent 1

VBC2 = the variation of back cross with parent 2

Estimation of heterosis

The estimates of heterosis over the mid parent and better parent heterosis (heterobeltiosis)

were calculated at each location using the procedures adopted by Fehr (1993) as under:

100BP

BP - F(BPH) Heterosisparent Better 1

Where,

MP = mid parent value of the particular F1 hybrid [(P1+P2)/2]

BP = better parent in a particular F1 hybrid (P1 or P2)

Correlation analysis

Variance and covariance components were estimated from analysis of variance and

analysis of covariance at individual location (Table 3.10 & 3.11), following Cochran and Cox

(1960) and Singh and Chaudhary (1985).

100MP

MP - F(MPH) HeterosisParent Mid 1

59

Table 3.10 Analysis of variance for generations on mean data of two locations

Source of variation Degree of freedom Expected mean squares

Reps (r-1) ….

Genotypes (g-1) δ2e+rδ2

g

Error (g-1)(r-1) δ2e

Total (rg-1) ….

Table 3.11 Analysis of covariance for generations on mean data of two locations

Source of variation Degree of freedom Sum Cross Product Mean Cross Product

Reps (r-1) RSCP RSCP/2

Genotypes (g-1) GSCP GSCP/5

Error (g-1)(r-1) ESCP ESCP/10

Total (rg-1) TSCP ….

i) genotypic and phenotypic correlation coefficients were calculated according to the

following equations using Microsoft Excel computer program.

Genotypic correlation

Genotypic correlations (rG) were calculated using the following relationship (Kwon and Torrie,

1964).

)(XV x )(XV

)X ,(XCov =

2G1G

21G

Gr

Where,

CovG(X1, X2) = genetic covariance X1, X2.

VG(X1) and VG(X2) = genetic variances for traits X1, X2.

60

Phenotypic correlation

Phenotypic correlation coefficient between two traits, X1 and X2 (rP) were calculated

using the following formula (Kwon and Torrie, 1964).

)(XV x )(XV

)X ,(XCov =

2P1P

21PPr

Where,

CovP(X1, X2) = phenotypic covariance X1, X2.

VP(X1) and VP(X2) = phenotypic variances for traits X1, X2.

61

Chapter 4

RESULTS

4.1 Generation mean analysis

Combined analysis of variance in all four crosses, revealed non-significant differences for

genotype × location interactions in days to tasseling, silking, anthesis, ear length, fresh ear

weight, kernel rows ear-1, grains row-1, grains ear-1 and % unpopped grains. Similarly,

genotype × location interactions in cross PS-1 × BD-1, were found significant in days to

maturity, expansion volume and ear diameter. In cross, PS-1 × BD-2 genotype × location

interaction was found significant for ear height, ear diameter, grain yield, biological yield,

harvest index, % shelling and expansion volume. Plant height, days to maturity, ear diameter,

100-grain weight, grain yield, % shelling and harvest index, exposed significant differences

among genotype × location interactions in PS-2 × BD-1. Like-wise, significant differences

among genotype × location interactions were observed for plant height, days to maturity, ear

diameter, grain yield, harvest index, % shelling and expansion volume in cross PS-2 × BD-2.

Mean data over locations was used for generation mean analysis in those traits, which exhibited

non-significant genotype × location interactions in respective crosses. Similarly, genetic effects

were studied at individual location in all other crosses, where genotype × location interactions

were significant for specific traits (Appendices 1-6).

Generation mean analysis was applied after observing significant differences among the

generations in combined analysis of variance as suggested by Gomez and Gomez (1983).

Significant differences were observed among various generations for all the plant traits studied.

The joint scaling test (Cavalli, 1952) was used to detect epistasis. In the presence of epistasis, the

additive (d) and the dominance (h) effects and non-allelic interaction components (additive ×

additive (i), additive × dominance (j) and dominance × dominance (l)) of generation means were

estimated according to Hayman (1958). The chi square (2) value was significant according to

joint scaling test (Cavalli, 1952) for all the traits in all four crosses studied, except for days to

tasseling and silking in cross III (PS-2 × BD-1) and grains per ear and 100 grain weight in cross I

(PS-1 × BD-1) which were not significant, showing the adequacy of three parameter model. The

significant value of chi square for all the plant traits in all crosses indicated that the three

parameter model did not adequately explain the genetic variability for these traits. The

62

inadequacy of the model also indicated the presence of epistasis (non-allelic interaction), which

is also inferred from the generation means. As the three parameter model did not satisfactorily

explain the genetic variability for all these traits, therefore, a six parameter model was applied to

accommodate epistatic interactions. Results obtained on different plant parameters given in

chapter 4 section 4.1 are briefly discussed in this section in the light of available literature and

research findings of the previous research workers.

4.1.1 Days to 50% tasseling

Six parameter model was adequate to explain the inheritance pattern of days to 50%

tasseling since 2 estimates were found significant for all the crosses except, PS-2 × BD-1 (Table

4.1). The dominance gene action and digenic non-allelic epistasis of additive × dominance were

found to be involved in governing the inheritance of days to tasseling in all crosses except, PS-2

× BD-1, having adequacy of three parameter model only. Similarly complementary type of non-

allelic interaction was observed for cross PS-1 × BD-2. The digenic non-allelic epistasis of

additive × dominance was considered the major contributor in the inheritance of this trait. In both

crosses (PS-1 × BD-2 and PS-2 × BD-2) additive gene action with negative magnitude was

found responsible for controlling days to tasseling.

4.1.2 Days to 50% anthesis

The significance of 2 estimates for all crosses revealed that six parameter model was

adequate to explain the inheritance pattern of days to 50% anthesis (Table 4.1). Additive and

dominance as well as additive × additive and dominance × dominance digenic non-allelic gene

interactions were important in governing the inheritance of days to anthesis in cross PS-1 x BD-

1. The presence of opposite and significant signs of h (dominance) and l (dominance ×

dominance) resulted in duplicate type of non-allelic interaction for the days to 50% anthesis in

cross PS-1 × BD-1, while h and l with similar and significant signs resulted in complementary

duplicate type of non-allelic interaction in cross PS-1 × BD-2. The digenic non-allelic epistasis

of dominance × dominance was considered the major contributing factor in the inheritance of

this trait in these two crosses. Similarly additive gene action as well as additive × dominance and

dominance × dominance type of non-allelic gene action with negative magnitude were found

responsible for controlling the inheritance of anthesis in cross PS-2 × BD-2. Similarly this trait

63

was controlled by dominance gene action with additive × dominance type of non-allelic

interaction in cross PS-2 × BD-1. Negative and significant values of h (dominance) showed a

major role of dominant gene action in the inheritance of this trait in all crosses except, PS-2 ×

BD-2.

4.1.3 Days to 50% silking

Results of generation mean analysis for flowering characters including days to 50%

silking are presented in Table 4.1. The best fit model indicated that both additive and non-

additive gene actions were responsible for the manifestation of days to 50% silking in all crosses,

except, PS-2 × BD-1. Analysis indicated that along with additive and dominance, duplicate type

of non-allelic gene action was found controlling days to silking in PS-1 × BD-1. Significant

value of d (additive), h (dominance), i (additive x additive) and l (dominance × dominance) in

this cross exhibited the involvement of both heritable and non-heritable gene actions. Similarly

in cross PS-1 × BD-2, a complementary duplicate type of non-allelic interaction with both

additive and dominance gene action was found to be responsible for controlling days to 50%

silking. In cross PS-2 × BD-2 along with dispersed type of digenic interaction, additive and

dominant type of gene action was prominent in the inheritance of days to silking.

4.1.4 Plant height

Six parameters model was adequate to explain the genetic constitution of plant height for

all crosses (Table 4.1). Highly significant value of 2 for plant height showed involvement of

both allelic and non-allelic gene actions for this trait. The inheritance pattern of plant height, also

involved duplicate type of epistasis in both crosses PS-1 × BD-2 and PS-2 × BD-1 since the

values of h and l were significant with opposite signs. Positive value of d (additive) and h

(dominance) in all crosses except, PS-2 × BD-2 at CCRI and PS-2 × BD-1 at UOA indicated

predominant role of additive and dominant gene action in the inheritance of plant height in these

crosses, respectively. Similarly in crosses, PS-1 × BD-1 significant and similar sign of h

(dominance) and l (dominance × dominance) revealed the involvement of complementary type of

di-genic non-allelic interaction for plant height. Positive and higher magnitude of h in all crosses,

except PS-2 × BD-1 at UOA entailed preponderant role of dominant gene action in the

inheritance of this trait. Additive × additive(i) interaction in both crosses PS-2 × BD-1 and PS-2

64

× BD-2 at UOA and CCRI were negative and significant except, PS-2 × BD-1 exhibited positive

and significant additive × additive(i) interaction at CCRI. Moreover, in non-allelic gene actions,

presence of i (additive × additive), j (additive × dominance) and l (dominance × dominance) with

both positive and negative but significant magnitude indicated that all the three types of digenic

non-allelic interactions played a leading role in the inheritance of this parameter.

4.1.5 Ear height

Estimates of genetic components and 2 values for ear height are presented Table 4.1.

The significant values of 2 revealed adequacy of six parameter model for the inheritance study

of ear height. From significant 2 value, both fixable and non-fixable gene interactions are

evident in the inheritance of this trait. Additive effects in cross PS-1 × BD-2 at both locations

were negative and non-significant for ear height, while, dominant effects were positive and

significant. It can be concluded from significant values of h (dominance) and l (dominance ×

dominance) with similar signs that digenic non-allelic interaction of complementary type

explained the inheritance of this trait in two crosses i.e. PS-2 × BD-1 and PS-2 × BD-2. The

presence of positive and significant values of d (additive) and h (dominance) in these two

crosses, disclosed the involvement of both additive and dominant gene actions in the inheritance

of ear height. Similarly in PS-1 × BD-1 and PS-1 × BD-2 dominance and duplicate type of non-

allelic gene action were found responsible in controlling inheritance of ear height. The

significant magnitudes of i (additive × additive), j (additive × dominance) and l (dominance ×

dominance) in all crosses except PS-2 × BD-1 and PS-2 × BD-2 indicated that digenic non-

allelic interactions also play governing role in the inheritance of this trait. Duplicate type of

digenic interaction was observed in cross PS-1 × BD-2 at UOA.

4.1.6 Ear weight

From estimates of genetic components presented in Table 4.1 after observing significant

values of 2 it is unveiled that six parameter model was found adequate for the interpretation of

inheritance of ear weight. It also disclosed that both heritable and non-heritable gene action were

responsible for the control of this trait. A dispersed type of non-allelic gene action was observed

in cross PS-1 × BD-1, with non-significant effects of both additive and dominance gene actions.

65

In cross PS-1 × BD-2, negative and positive significant nature of additive and dominance gene

actions as well as duplicate type of non-allelic gene actions were found as controlling factors in

the inheritance of ear weight. Similarly in cross PS-2 × BD-1 and PS-2 × BD-2, additive and

dominance gene action with positive magnitudes and complementary non-allelic interactions

were responsive agents for the inheritance of ear weight.

4.1.7 Grain yield

Gene actions presented in Table 4.2 revealed that six parameter model of both additive

and non-additive gen actions was adequate to explain the inheritance of grain yield. From the

table it is clear that 2 was significant for all the studied crosses. A dominance genetic effect of

positive and significant magnitude was found responsive in controlling inheritance of grain yield

in all crosses both at UOA and CCRI. Likewise additive gene action of negative sign was

observed in cross PS-1 × BD-1. Additive gene action was negative and non-significant in cross

PS-1 × BD-2 at CCRI, while negative but significant at UOA. PS-2 × BD-1 and PS-2 × BD-2

exhibited positive effects of additive effects at UOA and CCRI. Both complementary and

duplicate type of non-allelic gene action was observed to be involved in the inheritance of grain

yield. Significant values of additive and dominance gene actions as well as additive × additive

and dominance × dominance type of epistasis in cross PS-1 × BD-1, PS-2 × BD-1 and PS-2 ×

BD-2 revealed that the trait was under a complex control. In cross PS-1 × BD-1, with negative

and positive magnitudes of additive and dominance gene actions, complementary type of

epistasis was also observed. Similarly in cross PS-2 × BD-1 and PS-2 × BD-2, where the same

female (PS-2) parent was utilized both additive and dominance of positive magnitudes and

duplicate type of non-allelic gene actions were found responsible for controlling grain yield in

both UOA and CCRI.

4.1.8 Ear length

Generation mean analysis of ear length revealed significant 2 values in all four crosses

which indicate that six parameter model was adequate to explain the inheritance of this trait

(Table 4.2). In all crosses, dominant gene effects were positive and predominant. Additive gene

action of significant nature with positive and negative signs was observed in PS-1 × BD-2 and

PS-2 × BD-1. In cross PS-1 × BD-1, the effect of additive genes was negative with non-

66

significant nature, while dominance and dominance × dominance effects were significant with

positive and negative magnitude in nature, respectively. In cross PS-1 × BD-1 and PS-2 × BD-1

duplicate type of non-allelic interaction was found predominant in the inheritance study.

Additive × additive gene action was positive and significant in all the crosses except, PS-2 × BD-

2. In cross PS-2 × BD-1 and PS-1 × BD-2 additive × dominance effect was found negatively

significant. Similarly in cross PS-1 × BD-2 and PS-1 × BD-1, dominance × dominance was

predominant with negative magnitude.

4.1.9 Ear diameter

The genetic analysis revealed that complex six parameter model was adequate to explain

the inheritance pattern of ear diameter in all four crosses at both locations (Table 4.2). Additive

genetic effects were found positive and significant in cross PS-1 × BD-2 and PS-2 × BD-1 at

UOA, and cross PS-2 × BD-2 in CCRI. Dominant genetic effects were found positive and

significant except PS-1 × BD-2 at UOA. Dominant effects were predominant in all the crosses.

Among the non-allelic interactions, dominance × dominance interactions were non-significant in

all crosses at both locations, while additive × additive interactions were positively significant in

all crosses at CCRI, except PS-1 × BD-1. Genetic analysis for the inheritance of ear diameter

revealed that additive × dominance effects were significant in all crosses except PS-1 × BD-2

and PS-2 × BD-2. A dispersed duplicate type of non-allelic interaction was observed in all four

crosses at both locations.

67

Table 4.1 Estimates of genetic effects for some quantitative traits in 4 maize crosses evaluated at UOA and CCRI during

summer 2013.

m = mean, d = additive, h = dominance, i = additive x additive, j = additive x dominance, l = dominance × dominance

Parameter Cross Location m D h i j l 2

Type of non-

allelic

interaction

Days to Tasseling

PS-1 × BD-1 -------- 50.10** -0.92ns -8.22** -4.57* 1.03** 5.63ns 11.09* ----

PS-1 × BD-2 -------- 51.65** -2.53** -3.67* -1.07ns -1.00* -7.13** 73.55** Complementary

PS-2 × BD-1 -------- 49.55** -0.52ns -4.30* -- -- -- 6.56ns ----

PS-2 × BD-2 -------- 50.25** -2.68** -0.45ns 2.30ns -1.37* -7.70* 26.11** ----

Days to Anthesis

PS-1 × BD-1 -------- 53.47** -1.72** -8.92** -5.30** 0.30ns 7.70* 9.21* Duplicate

PS-1 × BD-2 -------- 55.35** -2.65** -4.70* -2.03ns -1.15* -6.53* 78.48** Complementary

PS-2 × BD-1 -------- 53.60** -0.67ns -6.20** -2.53ns 1.23* 2.00ns 8.38* ----

PS-2 × BD-2 -------- 53.73** -2.72** -0.22ns 2.23ns -1.33* -7.70* 25.40** ----

Days to Silking

PS-1 × BD-1 -------- 54.75** -1.93** -8.87** -5.33** 0.07ns 7.00* 7.88* Duplicate

PS-1 × BD-2 -------- 56.68** -2.47** -5.07* -2.07ns -0.70ns -7.13* 81.41** Complementary

PS-2 × BD-1 -------- 54.75** -0.72ns -5.65** -- -- -- 6.47ns ----

PS-2 × BD-2 -------- 55.85** -2.40** -4.25* -1.07ns -1.15* -3.83ns 25.25** ----

Plant Height

PS-1 × BD-1 -------- 148.79** 6.61** 9.22* -8.37* 0.17ns 26.94** 42.54** Complementary

PS-1 × BD-2 -------- 147.00** 1.63ns 14.58** 7.83** -3.35** -14.17** 13.01** Duplicate

PS-2 × BD-1 UOA 146.32** 1.41ns -9.16* -17.01** 4.81** 14.16** 48.82** Duplicate

CCRI 143.22** 9.2** 20.89** 8.58* 9.7** -10.74* 57.91** Duplicate

PS-2 × BD-2 UOA 149.88** 1.21ns 9.52** -7.28* 4.57** -1.78ns 43.9** ----

CCRI 146.81** -9.42** 1.84ns -18.64** -9.87** 41.91** 61.38** ----

Ear Height

PS-1 × BD-1 -------- 65.51** 1.03ns 18.12** 18.21** -3.68** -25.65** 119.15** Duplicate

PS-1 × BD-2 UOA 66.04** -0.80ns 11.79** 14.04** -1.58ns -8.06* 81.76** Duplicate

CCRI 67.51** -0.80ns 8.32** 10.58** -1.58ns -6.99ns 38.55** ----

PS-2 × BD-1 -------- 70.57** 1.47** 8.67** -1.02ns -2.66** 9.80** 82.36** Complementary

PS-2 × BD-2 -------- 70.69** 1.73** 5.52** -0.88ns 1.53** 18.84** 274.50** Complementary

Ear weight

PS-1 × BD-1 -------- 96.12** -4.47ns 15.05ns -26.13** 6.15* 3.30ns 58.0** ----

PS-1 × BD-2 -------- 96.05** -4.13* 30.42** -15.73* 0.48ns -31.30** 161.0** Duplicate

PS-2 × BD-1 -------- 99.27** 5.88** 20.85* -16.97* 4.20ns 14.83* 9.9* Complementary

PS-2 × BD-2 -------- 99.17** 4.60* 25.25** -18.20* -3.08ns 4.97ns 23.9** Complementary

68

4.1.10 Kernel rows ear-1

Estimates of genetic components and 2 values for kernel rows ear-1 presented in Table

4.2 revealed adequacy of six parameter model for the inheritance study of kernel rows ear-1.

Adequacy of six parameter model indicated the presence of both fixable and non-fixable gene

interactions in the inheritance of this trait. Additive genetic effects were positive and significant

in all crosses except, PS-1 × BD-1. Dominance and additive × additive effects were found

positive and significant in both cross PS-1 × BD-1 and PS-1 × BD-2, while dominance ×

dominance epistatic interaction was negatively significant which exhibited involvement of

duplicate type of non-allelic interaction in the inheritance of kernel rows ear-1. Additive ×

additive epistasis was significant in all crosses except, PS-1 × BD-2. Similarly additive ×

dominance (j) non-allelic interaction was non-significant in all crosses except, PS-2 × BD-2 in

which j was negative and significant.

4.1.11 Grains rows-1

Genetic estimates obtained through generation mean analysis revealed that six parameter

model was adequate in the inheritance of grains row-1 (Table 4.2). Additive genetic effects were

negatively significant in two crosses viz. PS-1 × BD-1 and PS-1 × BD-2, positively significant in

cross PS-2 × BD-1 and PS-2 × BD-2. Dominant effects were predominant with positive and

significant nature in all crosses. Maximum dominant effect was observed in cross PS-1 × BD-2

and PS-2 × BD-2. Additive × additive gene actions were positive and significant in cross PS-1 ×

BD-2 and PS-2 × BD-2 while, negatively significant in cross PS-1 × BD-1. Likewise, additive x

dominant effects were non-significant in all four crosses except, PS-1 × BD-1. Presence of

significant dominance and dominance × dominance nature resulted in complementary duplicate

type non-allelic interaction in cross PS-1 × BD-1, while duplicate type epistasis was observed in

cross PS-1 × BD-2 and PS-2 × BD-1.

4.1.12 Grains ear-1

Six parameters model was adequate to explain the inheritance pattern of grain ear-1 since

2 estimates were found significant for all crosses, except PS-1 × BD-1 (Table 4.2). Due to non-

significant value of 2 three parameter model was adequate for inheritance study of grains ear-1.

69

Significant effects of additive and dominance effects were observed with negative and positive

nature in cross PS-1 × BD-1, respectively. All epistatic effects in cross PS-1 × BD-1 were non-

significant. Dominant as well as dominant × dominant gene actions were significant with

opposite signs in cross PS-1 × BD-2 which resulted in duplicate type of non-allelic interaction.

Both additive and dominant effects were positive and significant in cross PS-2 × BD-1 and PS-2

× BD-2. Complementary type of epistasis was observed in cross PS-2 × BD-1. Additive ×

dominance effects were non-significant in all crosses.

4.1.13 Hundred grain weight

Genetic estimates obtained through generation mean analysis revealed that six parameter

model was adequate to explain the inheritance pattern of hundred grain weight since 2 estimates

were found significant for all crosses, except PS-1 × BD-1 (Table 4.3). The inheritance of

hundred grain weight seems to be controlled by major genes in the form of additive and

dominance gene effects in cross PS-1 × BD-1 as six parameters model was found inadequate

hence 2 value was non-significant. In cross PS-1 × BD-2 additive as well as additive ×

dominance effects were positive and significant with dispersed type of non-allelic interaction at

CCRI. Dominant genetic effects were negative in three crosses (PS-1 × BD-2, PS-2 × BD-1 and

PS-2 × BD-2) at CCRI. A complementary type of epistasis was observed in cross PS-2 × BD-2

as both dominant and dominant × dominant gene actions were positive and significant at CCRI.

Additive gene action along with additive × dominance effects were negatively significant in

cross PS-2 × BD-2 at UOA. In cross PS-1 × BD-2 at CCRI, both dominant and dominant ×

dominant gene actions were positive and significant which resulted in duplicate type of non-

allelic digenic interactions.

70


summer 2013.


Parameter Cross

Location

M d h i j l 2

Type of non-

allelic

interaction

Grain yield

PS-1 × BD-1 3806.68** -378.77** 651.31* -1181.20** 31.81ns 1204.11** 20.15** Complementary

PS-1 × BD-2 UOA 4274.7** -229.24** 791.94** -1764.03** 43.00ns 28.57ns 223.51** ----

CCRI 3865.17** -153.24ns 831.94** -588.03* 119.00ns -231.97ns 39.02** ----

PS-2 × BD-1 UOA 3775.15** 271.10** 2204.02** 661.48** 184.32** -2308.27** 88.27** Duplicate

CCRI 4184.69** 271.10** 2004.02** 661.48* 184.32* -1621.07** 43.66** Duplicate

PS-2 × BD-2 UOA 3979.92** 391.35** 1520.06** -234.38ns 166.23** -1465.17** 175.99** Duplicate

CCRI 4566.12** 391.35** 613.39* -941.05** 166.23* -71.29ns 129.56** ----

Ear length

PS-1 × BD-1 ------ 12.34** -0.33ns 8.96** 4.05** 0.40ns -6.15* 7.84* Duplicate

PS-1 × BD-2 ------ 12.86** 0.67* 8.71** 2.17* 0.46ns -4.92ns 8.44* ----

PS-2 × BD-1 ------ 13.16** -1.06** 6.73** 2.75* -1.02** -5.95* 14.34** Duplicate

PS-2 × BD-2 ------ 13.05** 0.17ns 3.79** -0.80ns -0.73* -0.92ns 7.96* ----

Ear diameter

PS-1 × BD-1 UOA 2.82** -0.17ns 1.81** 1.10** -0.07ns -1.39ns 12.59** ----

CCRI 3.44** -0.27** 0.52* -0.32ns -0.19ns 0.75ns 8.06* ----

PS-1 × BD-2 UOA 2.84** 0.28** -0.04ns -0.79** 0.06sn 1.10ns 3.69** ----

CCRI 3.06** -0.09ns 1.73** 1.14** -0.31** -2.31ns 41.08** ----

PS-2 × BD-1 UOA 2.74** 0.24** 0.68** 0.22ns 0.14ns 0.94ns 25.3** ----

CCRI 2.98** -0.04ns 1.57** 1.34** -0.10ns -1.35ns 24.23** ----

PS-2 × BD-2 UOA 2.56** -0.16* 1.02** 0.35ns -0.58** 0.54ns 52.74** ----

CCRI 2.87** 0.46** 1.78** 1.32** 0.10ns -1.62ns 21.51** ----

Kernel rows ear-1

PS-1 × BD-1 ------ 13.55** -0.55ns 7.32** 3.77** 0.17ns -8.17** 28.21** Duplicate

PS-1 × BD-2 ------ 14.12** 0.67* 5.32** 0.87ns 0.62* -5.90* 46.16** Duplicate

PS-2 × BD-1 ------ 13.07** 1.08** 5.30** 2.90** 0.48ns -1.53ns 18.38** ----

PS-2 × BD-2 ------ 12.87** 0.63** 4.33** 1.73* -0.73* -1.07ns 9.95** ----

Grains row-1

PS-1 × BD-1 ------ 28.33** -3.79** 6.65* -6.95* -2.04* 11.77** 11.50** Complementary

PS-1 × BD-2 ------ 27.32** -2.12** 14.38** 5.83* -0.44ns -20.15** 44.97** Duplicate

PS-2 × BD-1 ------ 27.83** 2.12** 5.64* -3.37ns -0.49ns 14.85** 25.60** Complementary

PS-2 × BD-2 ------ 26.07** 2.07** 14.65** 6.33* -0.62ns 0.83ns 27.65** ----

Grains ear-1

PS-1 × BD-1 ------ 384.03** -65.40** 282.70** --- --- --- 3.24ns ----

PS-1 × BD-2 ------ 387.32** -13.47ns 325.30** 100.87* 3.72ns -395.87** 63.08** Duplicate

PS-2 × BD-1 ------ 365.85** 59.81** 225.19** 28.18ns 11.33ns 195.82** 38.62** Complementary

PS-2 × BD-2 ------ 334.07** 44.80** 323.18** 138.63** -22.76ns 0.78ns 46.55** ----

71

4.1.14 Expansion volume

Generation mean analysis of expansion volume revealed that six parameter model was

adequate for the inheritance study of all crosses (Table 4.3). The 2 value obtained for expansion

volume were significant in all crosses both across locations and individual locations. Dominant

gene actions were negatively significant in both crosses PS-1 × BD-1 and PS-1 × BD-2 at both

locations. Similarly dominant effects at CCRI and UOA were positively significant in cross PS-2

× BD-2. In cross PS-2 × BD-1 along with both major gene effects (additive and dominant)

dominant × dominant digenic non-allelic interactions were positive and significant. Both

dominance effects and additive × dominance epistasis were negatively significant in cross PS-1 ×

BD-1 and PS-1 × BD-2 at both locations. In cross PS-1 × BD-2 both additive and dominant gene

actions were negatively significant while, epistatic interactions additive x dominant and

dominant × dominant were found negatively and positively significant at UOA and CCRI,

respectively. Due to presence of significant dominant effects and dominant × dominant epistasis

with contrasting signs resulted in duplicate type of non-allelic interaction for expansion volume

in all crosses except, PS-2 × BD-1. In cross PS-2 × BD-1 additive and dominant as well as all

three epistatic interactions were positive and significant. Complementary type of non-allelic

interaction was observed in cross PS-2 × BD-1.

4.1.15 Percentage of unpopped grains

Six parameter model was adequate to explain the inheritance pattern of percentage of

unpopped grains since 2 estimates were significant in all four crosses (Table 4.3). Additive

effects for percentage of unpopped grains were positively significant in two of the four crosses

while, non-significant with positive and negative magnitudes in the other two crosses. In cross

PS-1 × BD-1, both dominant and additive × additive epistasis were negative and significant

while, additive × dominance and dominance × dominance non-allelic interactions were non-

significant with positive and negative magnitudes, respectively. Additive genetic effects were

positively significant in cross PS-1 × BD-2 and PS-2 × BD-1. Similarly in cross PS-1 × BD-2

effect of dominant genes on percentage of unpopped grains was negative and non-significant,

while additive x dominant and dominant × dominant epistatic effects were positively significant

and negatively significant, respectively. Both additive × additive and dominant × dominant

epistasis were negative and non-significant in cross PS-2 × BD-1. In cross PS-2 × BD-2 both

72

dominant and additive × additive gene actions were negatively significant. Both additive x

dominant and dominant × dominant non-allelic interactions were positively significant in the

same cross. Presence of significant dominant and dominant × dominant effects with opposite

magnitudes resulted in duplicate type of diallelic interaction in cross PS-2 × BD-2.

4.1.16 Days to maturity

It is disclosed from estimates of genetic components and 2 values that six parameters

model of complex genetic nature was found adequate for the interpretation of inheritance (Table

4.4). It is obvious that both heritable and non-heritable gene actions were responsible in the

control of maturity. Major gene effects in the form of additive effects were negatively and non-

significant in all crosses at both UOA and CCRI except, in cross PS-2 × BD-2 where the said

effect was negative but significant at both locations. Similarly dominant gene actions were

negatively significant in all crosses with predominant magnitude. Dominant gene effects were

also found negative but of significant nature in cross PS-1 × BD-1 both at UOA and CCRI, while

at UOA this effect was negatively non-significant in cross PS-2 × BD-1 and PS-2 × BD-2. In

epistatic effects, additive × additive effects were found negative and non-significant in three

crosses at both locations. Non-allelic interaction of additive x dominant were positively

significant at CCRI in both crosses, PS-1 × BD-1 and PS-2 × BD-1, on other-hand such epistatic

effects were positive but non-significant in cross PS-2 × BD-2 at both locations. Dominant ×

dominant non-allelic interactions were negative and non-significant in three of the four crosses

which resulted in a dispersed type digenic interaction in them at both UOA and CCRI.

Significant and opposite values of dominant effect and dominant × dominant epistasis in cross

PS-2 × BD-2 at CCRI resulted in duplicate type of digenic non-allelic interaction.

4.1.17 Biological yield

Generation mean analysis of biological yield presented in Table 4.4 unveiled that six

parameter was adequate for the inheritance study. From Table 4.4 it is clear that 2 values

calculated were significant for all crosses. As genotype × location interactions were non-

significant in all crosses except, PS-1 × BD-2 where, genetic effects were calculated at individual

location. Additive gene actions for biological yield were negative and non-significant in cross

PS-1 × BD-2 at both locations, while in both crosses, PS-2 × BD-1 and PS-2 × BD-2 these

73

effects were positively significant. Similarly major gene effects of dominant genes were

positively significant in all crosses. Additive × additive epistatic effects were negative and

significant in all crosses except, PS-1 × BD-2. Similarly additive × dominance gene effects were

positively significant in two crosses (PS-1 × BD-1 and PS-2 × BD-1) while, negative and non-

significant in cross PS-2 × BD-2. Dominance × dominance effects for biological yield were non-

significant in all crosses, except PS-1 × BD-2. Duplicate type of digenic non-allelic interactions

were observed in cross PS-1 × BD-2 both at UOA and CCRI.

4.1.18 Harvest index

Six parameter model was adequate to explain the inheritance pattern of harvest index

since 2 estimates were significant in all four crosses (Table 4.4). Additive genetic effects for

harvest index were positively significant in both crosses PS-2 × BD-1 and PS-2 × BD-2 at UOA,

while negative and significant in cross PS-1 × BD-1. Dominant gene effects were positively

significant at UOA in both crosses, PS-1 × BD-2 and PS-2 × BD-1, while at CCRI such effects

were negatively and positively significant in cross PS-2 × BD-2 and cross PS-2 × BD-2,

respectively. Additive × additive epistatic interactions were found negative and significant in all

crosses except, PS-2 × BD-1 where they were positively significant at both locations. Dominant

× dominant epistasis, of both positive and negative magnitudes were observed in all crosses.

Presence of significant dominant and dominant × dominant gene actions with positive magnitude

resulted in a complementary type of non-allelic gene action in cross PS-1 × BD-1. Both

dominant and dominant × dominant gene actions were significant with opposite magnitudes in

cross PS-1 × BD-2 at both, UOA and CCRI. Similarly pattern of inheritance for major genes

(dominant) and minor genes (dominant × dominant) was also observed in cross PS-2 × BD-1 at

both locations. A duplicate type digenic non-allelic interaction was observed in cross PS-2 × BD-

1. Both additive × additive and dominant × dominant epistasis were negative and significant,

while dominance and additive gene effects were positively significant which give a duplicate

type of epistasis in cross PS-2 × BD-2 at CCRI.

74


summer 2013.


Parameter Cross Location m D h i j l 2

Type of non-

allelic

interaction

100 grain weight

PS-1 × BD-1 ------ 16.90** -1.40* 6.57* --- --- --- 0.71ns ----

PS-1 × BD-2 UOA 18.7** 1.43ns -10.50** -19.80** 2.20** 30.47** 68.68** Duplicate

CCRI 14.1** 1.43* 16.7** 17.00** 2.20** -24.73** 49.42** Duplicate

PS-2 × BD-1 UOA 14.63** -0.133ns 2.73ns -2.27ns -1.53ns 12.27** 41.01** ----

CCRI 19.23** -0.13ns 7.07* -2.27ns 2.80** 4.40ns 16.01** ----

PS-2 × BD-2 UOA 14.23** -1.43* 1.20ns -3.67ns -2.90** 16.13** 72.79** ----

CCRI 18.83** -1.57* 6.13* -3.40ns 1.30ns 8.40* 12.55* Complementary

Expansion volume

PS-1 × BD-1 UOA 31.17** -0.30ns -25.07** -4.33ns -6.43** 42.8** 284.81** Duplicate

CCRI 36.87** -0.50ns -27.00** -4.60ns -7.30** 51.07** 483.59** Duplicate

PS-1 × BD-2 UOA 32.63** -10.37** -28.43** 2.87ns -14.73** 8.47* 225.14** Duplicate

CCRI 38.47** -10.40** -30.87** 2.27ns -15.34** 16.94** 359.97** Duplicate

PS-2 × BD-1 ------ 35.41** 1.68** 4.68* 5.86** 3.39** 28.93** 904.46** Complementary

PS-2 × BD-2 UOA 36.83** 5.30** 10.10* 23.00** 8.73** -43.00** 145.07** Duplicate

CCRI 42.76** 5.28** 9.38** 22.45** 8.88** -34.62** 185.84** Duplicate

%age unpoped grain

PS-1 × BD-1 ------ 23.07** -1.82ns -12.41* -10.78* 1.10ns -3.88ns 45.46** ----

PS-1 × BD-2 ------ 22.58** 4.70** -5.09ns 1.86ns 12.02** -20.25** 111.53** Complementary

PS-2 × BD-1 ------ 22.08** 2.72* -3.02ns -2.96ns 3.71* -4.69ns 15.21** ----

PS-2 × BD-2 ------ 23.85** 1.41ns -28.18** -20.91** 6.79** 27.29** 36.17** Duplicate

75

4.1.19 Percent shelling

Generation mean analysis of percent shelling revealed significant 2 values in all four

crosses which indicate that six parameter model of complex genetic nature was adequate to

explain the inheritance of this trait both at both locations, except in cross PS-2 × BD-1 at UOA

(Table 4.4). In cross PS-2 × BD-1 at UOA only major genes (additive and dominant) were found

to be involved in the inheritance of percent shelling. In all crosses dominant gene effects were

positive and significant while, effects due to additive genes were negative and non-significant in

all crosses at UOA and CCRI. Similarly, additive × additive gene actions were positively

significant in three crosses at both locations except, PS-1 × BD-2 at UOA. Additive × dominance

effects were positive in all crosses except, PS-2 × BD-2, where it was negative and non-

significant. Dominant × dominant non-allelic interactions were negatively significant in all

crosses except PS-1 × BD-2 at CCRI. Significant and opposite signs of dominant gene action and

dominant × dominant epistasis for percent shelling depicted a duplicate type of digenic non-

allelic interaction in three crosses except, PS-1 × BD-2 at CCRI.

76


summer 2013.

Parameter Cross Location m d h i j l Type of non-allelic interaction

Days to maturity

PS-1 × BD-1 UOA 93.8** -1.25ns -6.93* -4.37ns 1.18ns 1.07ns 13.89** ----

CCRI 97.87** -0.82ns -7.80** -5.23ns 1.62* 8.40* 8.96* Duplicate

PS-1 × BD-2 ------ 98.28** -2.33** -7.87** -5.07* 0.27ns -4.33ns 76.97** ----

PS-2 × BD-1 UOA 93.82** -0.68ns -4.73ns -2.5ns 1.82* -2.33ns 18.44** ----

CCRI 97.88** -0.68ns -4.73* -2.5ns 1.82* 3.27ns 7.99* ----

PS-2 × BD-2 UOA 94.97** -2.32** -4.09ns -1.97ns 0.35ns -7.13ns 40.03** ----

CCRI 99.03** -2.32** -4.90* -1.97ns 0.35ns -3.13ns 9.87** ----

Biological yield

PS-1 × BD-1 ------ 203.12** -5.00* 18.15* -25.47** 5.62* -1.17ns 71.02** ----

PS-1 × BD-2 UOA 206.33** -4.07ns 40.02** -15.53ns 1.55ns -46.83** 235.26** Duplicate

CCRI 199.13** -4.07ns 23.22** -15.53ns 1.55ns -18.03* 79.7** Duplicate

PS-2 × BD-1 ------ 206.90** 5.72** 20.98** -19.83* 5.03* 12.03ns 22.37** ----

PS-2 × BD-2 ------ 206.17** 4.60* 27.25** -18.20* -1.08ns 0.97ns 31.93** ----

Harvest index

PS-1 × BD-1 ------ 32.77** -2.60** 3.42* -6.32** -0.03ns 8.52** 14.67** Complementary

PS-1 × BD-2 UOA 38.38** -1.01ns 11.46** -7.64* 0.99ns -11.61** 181.05** Duplicate

CCRI 31.18** -1.01ns -5.33** -7.64** 0.99ns 17.19** 48.48** Duplicate

PS-2 × BD-1 UOA 29.72** 1.34* 10.75** 9.09** -3.61** -12.98** 83.58** Duplicate

CCRI 36.92** 1.34ns 19.15** 9.09** 4.79** -24.99** 115.01** Duplicate

PS-2 × BD-2 UOA 33.12** 2.63** -2.01ns -4.89** -2.89** 1.58ns 60.2** ----

CCRI 40.32** 2.58** 5.91* -5.37* 5.46** -9.46* 241.50** Duplicate

Percent Shelling

PS-1 × BD-1 ------ 77.56** -1.74ns 20.65** 13.14* 1.85ns -26.67** 11.97** Duplicate

PS-1 × BD-2 UOA 80.99** -1.08ns 29.13** 13.05ns 4.39** -32.39** 24.06** Duplicate

CCRI 73.80** -1.34ns 13.66* 13.59* 4.12* -3.06ns 24.56** ----

PS-2 × BD-1 UOA 74.43** -0.25ns 17.63* --- --- --- 5.92ns ----

CCRI 81.63** -0.25ns 26.03** 14.49* 5.75* -30.48** 20.06** Duplicate

PS-2 × BD-2 UOA 72.53** -0.47ns 18.83** 18.32* -0.99ns -16.24* 10.21* Duplicate

CCRI 79.73** -0.47ns 27.23** 18.32* 7.41** -28.24** 17.72** Duplicate


77

4.2 Heritability

The heredity and environmental factors are the two important factors effecting the genetic

composition and individual performance in the population. The genetic and environmental

variations are used in the estimation of heritability. Heritability estimates are used as a helping

tool in choosing a suitable breeding method, prediction of direct and correlated response to

selection, as well as in the estimation of genetic gain. This section include explanation about the

broad and narrow sense heritability estimates for four maize crosses (Cross-I = PS-1 × BD-1,

Cross-II = PS-1 × BD-2, Cross-III = PS-2 × BD-1, Cross-IV = PS-2 × BD-2) derived from two

contrasting groups of inbred lines, with two inbreds in each group.


It is exhibited from Table 4.5 that high broad sense heritability estimates were exhibited

by all four crosses for days to tasseling. Heritability estimates for tasseling ranged from 0.69 to

0.76. High broad sense heritability estimate (0.76) was observed for both PS-1 × BD-2 and PS-2

× BD-2, followed by cross PS-2 × BD-1 and PS-1 × BD-1 with h2BS of 0.75 and 0.69,

respectively. Moderate narrow sense heritability estimates were observed in four crosses for days

to tasseling. Narrow sense heritability ranged from 0.38 to 0.69 for cross PS-2 × BD-2 and PS-1

× BD-1, respectively.


Heritability estimates presented in Table 4.5 revealed high level of broad sense

heritability for days to 50% anthesis among the four crosses. Broad sense heritability estimate

ranged from 0.81 to 0.84 for cross PS-2 × BD-1 and PS-1 × BD-2, respectively. Similarly narrow

sense heritability estimates ranged from 0.46 to 0.67. Maximum narrow sense heritability of 0.67

was calculated for the cross PS-1 × BD-2, while minimum (0.46) was observed for cross PS-2 ×

BD-1.


Heritability estimates for days to 50% silking are presented in Table 4.5. Maximum broad

sense heritability estimate of 0.81 was reported for cross PS-1 × BD-1 and PS-1 × BD-2,

followed by 0.79 for PS-2 × BD-1, while minimum broad sense heritability of 0.75 was reported

78

for PS-2 × BD-2. Narrow sense heritability estimates ranged from 0.44 to 0.67 for cross PS-2 ×

BD-1 and PS-1 × BD-2, respectively.

4.2.4 Plant height

Estimates of heritability for plant height are provided in Table 4.5. High level of broad

sense heritability was observed for plant height in all four crosses. Broad sense heritability varied

from 0.73 to 0.84. Maximum broad sense heritability of 0.84 was found for cross PS-1 x BD-1,

followed by PS-2 × BD-2 with h2BS of 0.84. The narrow sense heritability estimates showed a

range of 0.52 to 0.69 for cross PS-1 × BD-1 and PS-2 × BD-1, respectively for this parameter.

Narrow sense heritability of 0.55 and 0.54 was observed for cross PS-1 × BD-2 and PS-2 × BD-

2, respectively.

4.2.5 Ear height

Broad sense heritability estimates in all four crosses were high for ear height, ranging

from 0.80 to 0.85 (Table 4.5) in cross PS-1 × BD-2 and PS-2 × BD-2, respectively. Similarly

narrow sense heritability estimates ranged from moderate to high for ear height. Maximum

(0.74) estimate of narrow sense heritability was observed for the cross PS-2 × BD-2 while,

minimum (0.43) estimates of heritability in narrow sense was noticed in the cross PS-1 × BD-2

for this trait.

4.2.6 Ear weight

Both broad sense and narrow sense heritability estimates for ear weight are provided in

Table 4.5. High broad sense heritability estimates were observed in all four crosses for ear

weight, ranging from 0.77 to 0.81 (Table 4.5) in cross PS-1 × BD-2 and PS-2 × BD-2,

respectively. Broad sense heritability estimate of 0.79 was observed for both PS-1 × BD-1 and

PS-2 × BD-1. Moderate level of narrow sense heritability estimates were calculated for ear

weight. Maximum (0.52) estimate of narrow sense heritability was observed for the cross PS-2 ×

BD-1 while, minimum (0.41) estimates of heritability in narrow sense was calculated for both

PS-1 × BD-1 and PS-2 × BD-2 crosses for ear weight parameter.

79

4.2.7 Grain yield

Broad and narrow sense heritability estimates for grain yield are provided in Table 4.5.

High level of broad sense heritability was calculated for grain yield in all four crosses. The range

of broad sense heritability for grain yield was 0.69 to 0.82. Maximum broad sense heritability of

0.82 was found for cross PS-2 × BD-1, followed by cross PS-2 × BD-2 with h2BS of 0.79.

Similarly narrow sense heritability estimates varied from moderate to high range. Maximum

(0.62) narrow sense heritability was reported for cross PS-1 × BD-1, followed by PS-2 × BD-1

with h2NS 0.58. Likewise, minimum narrow sense heritability estimates 0f 0.41 and 0.45 were

observed for PS-1 × BD-2 and PS-2 × BD-2, respectively.

4.2.8 Ear length

High estimates of both broad and narrow sense heritability were calculated for ear length

(Table 4.5). Broad sense heritability estimates in all four crosses varied from 0.71 to 0.76. High

values of h2BS was observed in cross PS-2 × BD-1 while, cross PS-1 × BD-2 exhibited low

heritability in broad sense. Moderate narrow sense heritability estimates was calculated for ear

length. Maximum (0.59) estimate of narrow sense heritability was observed for the cross PS-2 ×

BD-1 while, minimum (0.40) estimates of heritability in narrow sense was noticed in the cross

PS-2 × BD-2 for this trait.

4.2.9 Ear diameter

Both broad sense and narrow sense heritability estimates for ear diameter are presented in

Table 4.5. High broad sense heritability estimates were observed in all four crosses for ear

weight, ranging from 0.72 to 0.77 in cross PS-2 × BD-2 and PS-2 × BD-1, respectively. Broad

sense heritability estimate of 0.76 was observed for both PS-1 × BD-2. Moderate to high level of

narrow sense heritability estimates were calculated for ear diameter. Maximum (0.63) estimate of

narrow sense heritability was observed for the cross PS-1 × BD-2 while, minimum (0.47)

estimates of heritability in narrow sense was calculated for PS-2 × BD-2 crosses in ear weight.

4.2.10 Grains row-1

Broad and narrow sense heritability estimates for grains row-1 are provided in Table 4.5.

High level of broad sense heritability was calculated for grains row-1 in all four crosses. The

80

range of broad sense heritability for this parameter was 0.66 to 0.71. Maximum broad sense

heritability of 0.71 was found for cross PS-1 × BD-2, followed by cross PS-2 × BD-1 with h2BS

of 0.69. Similarly narrow sense heritability estimates varied from moderate to high range.

Maximum (0.63) narrow sense heritability was reported for cross PS-2 × BD-2, followed by PS-

1 × BD-2 with h2NS 0.61. Likewise, minimum narrow sense heritability estimate of 0.45 was

observed for grains row-1 in cross PS-1 × BD-1.

4.2.11 Grains ear-1


heritability for grains ear-1 in all four crosses. Broad sense heritability varied from 0.70 to 0.82.

Maximum broad sense heritability of 0.82 was found for cross PS-1 × BD-2, followed by PS-1 x

BD-1 with h2BS of 0.81. The narrow sense heritability estimates showed a range of 0.34 to 0.57

for cross PS-2 × BD-2, PS-1 × BD-1 and PS-1 × BD-2, respectively for this parameter. High

narrow sense heritability of 0.57 was observed for cross PS-1 × BD-1 and PS-1 × BD-2 followed

by PS-2 × BD-1 and PS-2 × BD-2 with 0.61 and 0.34, respectively.


Broad and narrow sense heritability estimates are demonstrated in Table 4.5. It is

obvious from the table that high broad sense heritability estimates were reported in all four

crosses for hundred grain weight. Broad sense heritability estimates for hundred grain weight

ranged from 0.86 to 0.89. High broad sense heritability estimate (0.89) was observed for cross

PS-2 × BD-1, followed by cross PS-2 × BD-2, PS-1 × BD-1 and PS-1 × BD-2 with h2BS of 0.88,

0.87 and 0.86, respectively. Moderate to high narrow sense heritability estimates were observed

in all four crosses for hundred grain weight. Narrow sense heritability ranged from 0.45 to 0.71

for cross PS-1 x BD-1 and PS-2 × BD-1, respectively.


Heritability estimates of percent shelling presented in Table 4.5 revealed high level of

broad sense heritability for percent shelling in the four crosses. Broad sense heritability estimates

varied from 0.70 to 0.75. Maximum h2BS for percent shelling was observed in cross PS-1 × BD-

1, followed by cross PS-2 × BD-1 with 0.73. Minimum narrow sense heritability of 0.70 was

81

calculated for cross PS-2 × BD-2. Similarly narrow sense heritability estimates occurred in

moderate range. Maximum narrow sense heritability of 0.56 was calculated for cross PS-1 × BD-

2, while minimum (0.46) was observed for cross PS-1 × BD-1.


Broad and narrow sense heritability estimates for expansion volume are provided in

Table 4.5. High levels of broad sense heritability were calculated for expansion volume in all

four crosses. The range of broad sense heritability for expansion volume was 0.64 to 0.76.

Maximum broad sense heritability of 0.76 was found for cross PS-1 x BD-1, followed by cross

PS-2 × BD-1 with h2BS of 0.68. Minimum broad sense heritability of 0.64 was reported for

expansion volume in PS-1 × BD-2. Similarly estimates of narrow sense heritability were of

moderate level for expansion volume. Maximum (0.50) narrow sense heritability was reported

for cross PS-1 × BD-2, followed by PS-2 × BD-2 with h2NS 0.49. Likewise, minimum narrow

sense heritability estimate of 0.41 was observed for both PS-1 × BD-1 and PS-2 × BD-1.

4.2.15 Percent unpopped grains


heritability for percent unpopped grains in all four crosses. Broad sense heritability varied from

0.83 to 0.87. Maximum broad sense heritability of 0.87 was found for cross PS-2 × BD-1,

followed by PS-1 × BD-2 with h2BS of 0.86. Minimum (0.83) h2

BS was calculated for cross PS-1

x BD-1. The narrow sense heritability estimates showed a range of 0.50 to 0.74 for cross PS-2 ×

BD-2 and PS-1 × BD-2, respectively for this parameter. High narrow sense heritability of 0.72

was observed for cross PS-2 × BD-1, followed by PS-1 × BD-1 with 0.51.

82

Table 4.5 Broad-sense (h2 (BS)) and narrow-sense (h2

(NS)) heritability estimates for four maize crosses evaluated at UOA

and CCRI during summer 2013.

Parameters Cross-I Cross-II Cross-III Cross-IV

(h2BS) (h2

NS) (h2BS) (h2

NS) (h2BS) (h2

NS) (h2BS) (h2

NS)

Days to tasseling 0.69 0.45 0.76 0.69 0.75 0.57 0.76 0.38

Days to anthesis 0.82 0.54 0.84 0.67 0.81 0.46 0.83 0.57

Days to silking 0.81 0.48 0.81 0.67 0.79 0.44 0.75 0.58

Plant height 0.84 0.52 0.73 0.55 0.79 0.69 0.80 0.54

Ear height 0.83 0.68 0.80 0.43 0.82 0.71 0.85 0.74

Ear weight 0.79 0.41 0.77 0.48 0.79 0.52 0.81 0.41

Ear diameter 0.77 0.57 0.76 0.47 0.72 0.65 0.75 0.55

Ear length 0.75 0.47 0.71 0.50 0.76 0.59 0.75 0.40

Kernel rows ear-1 0.75 0.50 0.76 0.63 0.77 0.53 0.72 0.47

Grains row-1 0.66 0.45 0.71 0.61 0.69 0.58 0.68 0.63

Grains ear-1 0.81 0.57 0.82 0.57 0.71 0.64 0.70 0.34

100-grain weight 0.86 0.45 0.87 0.53 0.89 0.71 0.88 0.55

Percent shelling 0.75 0.46 0.72 0.56 0.73 0.54 0.70 0.50

Grain yield 0.77 0.62 0.69 0.41 0.82 0.58 0.79 0.45

Expansion volume 0.76 0.41 0.64 0.50 0.68 0.41 0.66 0.49

Percent unpopped grains 0.83 0.51 0.86 0.74 0.87 0.72 0.84 0.50

Day to maturity 0.86 0.77 0.88 0.63 0.80 0.60 0.82 0.61

Biological yield 0.80 0.58 0.80 0.54 0.75 0.37 0.81 0.55

Harvest index 0.67 0.58 0.60 0.33 0.62 0.33 0.49 0.30

Cross-I = PS-1 × BD-1, Cross-II = PS-1 × BD-2, Cross-III = PS-2 × BD-1, Cross-IV = PS-2 × BD-2

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Broad and narrow sense heritability estimates for days to maturity are provided in Table

4.5. High levels of broad sense heritability were calculated for days to maturity in all four

crosses. Broad sense heritability varied from 0.80 to 0.88 for days to maturity. Maximum broad

sense heritability of 0.99 was found for cross PS-1 × BD-2, followed by cross PS-1 × BD-1 with

h2BS of 0.86. Minimum broad sense heritability of 0.80 was observed for days to maturity in

cross PS-2 × BD-1. Similarly narrow sense heritability estimates varied from moderate to high

range. Maximum (0.77) narrow sense heritability was noticed for cross PS-1 × BD-1, followed

by PS-1 × BD-2 with h2NS 0.63. Likewise, minimum narrow sense heritability estimates of 0.60

were observed for PS-2 × BD-1.


Broad and narrow sense heritability estimates for biological yield are provided in Table

4.5. High levels of broad sense heritability were calculated for biological yield in all four crosses.

The range of broad sense heritability for biological yield was 0.75 to 0.81. Maximum broad

sense heritability of 0.81 was found for cross PS-2 × BD-2, followed by cross PS-1 × BD-1 and

PS-1 × BD-2 with h2BS of 0.80. Minimum broad sense heritability of 0.75 was reported for

biological yield in cross PS-2 × BD-1. Similarly estimates of narrow sense heritability were of

moderate level for biological yield. Maximum (0.58) narrow sense heritability was reported for

cross PS-1 × BD-1, followed by PS-2 × BD-2 with h2NS 0.55. Likewise, minimum narrow sense

heritability estimate of 0.37 was observed in cross PS-2 × BD-1.


Broad and narrow sense heritability estimates for harvest index are provided in Table 4.5.

Moderate to high levels of broad sense heritability were calculated for harvest index in all four

crosses. Broad sense heritability estimates for harvest index varied from 0.49 to 0.67. Maximum

broad sense heritability of 0.67 was found for cross PS-1 x BD-1, followed by cross PS-2 × BD-

1 and PS-1 × BD-2 with h2BS of 0.62 and 0.60, respectively. Minimum broad sense heritability of

0.49 was reported for harvest index in cross PS-2 × BD-2. Similarly estimates of narrow sense

heritability were low to moderate level for harvest index. Maximum (0.58) narrow sense

heritability was reported for cross PS-1 × BD-1, followed by PS-1 × BD-2 and PS-1 × BD-1 with

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h2NS 0.33. Likewise, minimum narrow sense heritability estimate of 0.30 was observed in cross

PS-2 × BD-2.

4.2.19 kernel rows ear-1

Broad and narrow sense heritability estimates for kernel rows ear-1 are provided in Table

4.5. High levels of broad sense heritability were calculated for kernel rows ear-1 in all four

crosses. Broad sense heritability varied from 0.72 to 0.77 for kernel rows ear-1. Maximum broad

sense heritability of 0.77 was found in cross PS-2 × BD-1while, minimum broad sense

heritability of 0.72 was observed in cross PS-2 × BD-2. Similarly narrow sense heritability

estimates varied from moderate to high range. Maximum (0.63) narrow sense heritability was

reported for cross PS-1 × BD-2, followed by PS-2 × BD-1 with h2NS 0.53. Likewise, minimum

narrow sense heritability estimate of 0.47 was observed for PS-2 × BD-2.

4.3 Heterosis

Heterosis also known as hybrid vigor, has been the subject of intense research and

speculation for well over a century however, the basic mechanisms that cause or contribute to

heterosis remain unclear (Coors and Pandey, 1999). Being the lack of understanding, plant

breeders have quite successfully exploited heterosis to increase the vigor of many domesticated

species (Springer and Stupar, 2007). In maize, highly heterozygous crop the heterosis is reported

to cause an increase in yield by 15 % per year (Duvick, 1999). Maize breeders have been looking

for the possibility of predicting heterosis between inbred lines of maize based on physiological,

morphological, molecular marker and biochemical data during the past decades (Smith and

Smith, 1989; Smith et al., 1990 and Ramesh et al., 1995). The results obtained from four maize

crosses (PS-1 × BD-1, PS-1 × BD-2, PS-2 × BD-1 and PS-2 × BD-2) are explained here in detail

to elucidate heterotic pattern for 20 different plant parameters of quantitative nature.


Negative nature of mid and better-parent heterosis for days to tasseling was observed

(Table 4.6). Mid-parent showed that maximum heterosis (-7.15 %) of negative nature for days to

50% tasseling was observed in cross PS-1 × BD-1 while, minimum mid-parent heterosis of -5.13

was displayed for the cross PS-1 × BD-2. Similarly, better-parent heterosis for days to tasseling

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ranged from -3.77 to -2.17%. Maximum better-parent heterosis was calculated for cross PS-2 ×

BD-1, followed by cross PS-1 × BD-1 with negative heterosis of -3.46. Minimum better-parent

heterosis of -2.17 was exhibited by cross PS-1 × BD-2.

4.3.2Days to anthesis

Heterosis magnitudes of both mid and better-parent for days to 50% anthesis are

presented in Table 4.6. Maximum (-6.74 %) mid-parent heterosis of negative nature was

observed for days to 50% anthesis in cross PS-2 × BD-1 while, minimum mid-parent heterosis of

-4.67 was exhibited by the cross PS-2 × BD-2. Maximum (-3.65) better-parent heterosis of

negative magnitude for days to anthesis was expressed by cross PS-2 × BD-1, followed by PS-1

× BD-1 with -3.05. Minimum (-2.22 %) better-parent heterosis was calculated for cross PS-1 ×

BD-2.

4.3.3Days to 50% silking

Negative heterosis of both mid and better-parent was exhibited in all the studied crosses

(Table 4.6) for days to 50% silking. Mid-parent heterosis ranged from -6.48 to -5.07 for the

crosses PS-2 × BD-1 and PS-2 × BD-2, respectively. Better-parent heterosis was of negative

nature with a variant pattern. The maximum better-parent heterosis of -2.46 % was observed for

cross PS-1 × BD-1 while, minimum level of -2.30 was obvious for cross PS-1 × BD-2 with

respect to the parameter of days to silk.

4.3.4 Plant height

Mid-parent heterosis varied from 4.69 to 12.34 % for plant height (Table 4.6). The

maximum mid-parent heterosis of 12.34 % was exhibited in cross PS-1 × BD-1, followed by PS-

2 × BD-2 with mid-parent heterosis of 11.99 %. The least mid-parent heterosis (4.69 %) was

manifested for cross PS-1 × BD-2. The better-parent heterosis with maximum magnitude of

17.66 % was expressed in the cross PS-1 × BD-1, for the parameter of plant height. Similarly the

minimum better-parent heterosis (8.44 %) was recorded for PS-1 × BD-2.

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4.3.5 Ear height

Both negative and positive magnitudes of mid-parent heterosis were calculated for ear

height. Mid-parent heterosis varied from -0.13 to 14.31 % (Table 4.6). It was indicated that

maximum mid-parent heterosis of 14.31 % was exhibited by the cross PS-2 × BD-1, followed by

cross PS-2 × BD-2 with magnitude of 7.84 % having the same female parent (PS-2). The better-

parent heterosis observed in the present study revealed that maximum better-parent heterosis of

21.75 % was observed for the cross PS-2 × BD-1 while, minimum (-2.07 %) better-parent

heterosis of negative magnitude was exhibited by the cross PS-1 × BD-2 for ear height.

4.3.6 Ear weight

The mid and better parent heterosis values regarding ear weight are provided in Table

4.6. The maximum mid-parent heterosis of 80.56 % was calculated for cross PS-1 × BD-2,

followed by cross PS-1 × BD-1, PS-2 × BD-2 and PS-2 × BD-1 with 65.08, 62.44 and 50.3 %,

respectively. Similarly better parent heterosis for ear weight ranged from 67.10 to 41.36 % for

the cross PS-1 × BD-2 and PS-1 × BD-1, respectively.

4.3.7 Grain yield

Heterotic values for grain yield are presented in Table 4.6. It is revealed from the table

that maximum values of both mid and better-parent heterosis values were calculated for the

crosses having PS-1 as female parent. Maximum mid parent heterosis of 80.73 % was reported

for cross PS-1 × BD-2, followed by PS-1 × BD-1, PS-2 × BD-2 and PS-2 × BD-1 with mid-

parent heterosis of 70.46, 55.90 and 46.56 %, respectively. Better-parent heterosis for grain

yield varied from 62.74 to 42.57 %. Maximum better-parent heterosis of 62.74 % was exhibited

by cross PS-1 × BD-2, followed by 47.21 % for cross PS-1 × BD-1. The minimum better parent

heterosis of 42.57 % was calculated for the cross PS-2 × BD-1.


Both mid and better-parent heterotic values for days to maturity are presented in Table

4.6. Maximum (-2.91 %) mid-parent heterosis of negative nature was observed for days to

maturity in cross PS-1 × BD-2, followed by -2.68, -2.33 and -2.22 in cross PS-1 × BD-1, cross

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PS-2 × BD-1 and PS-2 × BD-2, respectively. Similarly better-parent heterosis of maximum (0.57

%) magnitude for days to maturity was expressed by cross PS-2 × BD-2, followed by PS-1 ×

BD-1 with 0.29 %. Minimum (-0.14 %) better-parent heterosis was calculated for cross PS-1 ×

BD-1.

4.3.9 Ear diameter

Positive heterosis of both mid and better-parent was exhibited in all the studied crosses

(Table 4.6) for ear diameter. Mid-parent heterosis ranged from 11.28 to 26.52 for the crosses PS-

1 × BD-2 and PS-2 × BD-1, respectively. Better-parent heterosis was of positive nature and

varied from 16.86 to 5.45 % for ear diameter. The maximum better-parent heterosis of 16.86 %

was observed for cross PS-1 × BD-1 while, minimum level of 5.45 was obvious for cross PS-2 ×

BD-2 with respect to the parameter of ear diameter.

4.3.10 Ear length

Heterotic values for yield related trait, ear length are presented in Table 4.6. It is revealed

from the table that maximum values of both mid and better-parent heterosis values were

calculated for the crosses having PS-1 as female parent and BD-2 as male parent. Maximum mid

and better-parent heterosis of 69.28 and 65.63 % were reported for cross PS-1 × BD-2, followed

by PS-1 × BD-1 with 47.31 and 37.69 % mid and better-parent heterosis, respectively. In better-

parent heterosis, minimum 33.59 % for ear diameter was observed for cross PS-2 × BD-2. Mid

parent heterosis of 45.34 and 35.95 % was calculated for cross PS-2 × BD-2 and PS-2 × BD-1,

respectively. Minimum better parent heterosis of 33.59 % was calculated for the cross PS-2 ×

BD-2.

4.3.11 Kernel rows per ear

Like other yield related traits both mid and better-parent heterosis were of positive nature

for kernel rows ear-1 are presented in Table 4.6. Maximum (41.01 %) mid-parent heterosis with

was observed for kernel rows ear-1 in cross PS-1 × BD-2, followed by 30.56, 21.37 and 18.56 in

cross PS-1 × BD-1, cross PS-2 × BD-2 and PS-2 × BD-1, respectively. Similarly in better-parent

heterosis maximum (40.37 %) magnitude for kernel rows ear-1 was expressed by cross PS-1 ×

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BD-2, followed by PS-1 × BD-1 with 22.97 %. Minimum (9.11 %) better-parent heterosis was

calculated for cross PS-2 × BD-2.

4.3.12 Grains row-1

Like other yield related traits both mid and better-parent heterosis for kernel rows ear-1

were of positive nature as presented in Table 4.6. Maximum (41.01 %) mid-parent heterosis with

was observed for kernel rows ear-1 in cross PS-1 × BD-2, followed by 30.56, 21.37 and 18.56 in

cross PS-1 × BD-1, cross PS-2 × BD-2 and PS-2 × BD-1, respectively. Similarly in better-parent

heterosis, maximum (40.37 %) magnitude for kernel rows ear-1 was expressed by cross PS-1 ×

BD-2, followed by PS-1 × BD-1 with 22.97 %. Minimum (9.11 %) better-parent heterosis was

calculated for cross PS-2 × BD-2.

4.3.13 Grains ear-1

The mid-parent heterosis varied from 59.28 to 113.86 % for grain ear-1 (Table 4.6). The

maximum mid-parent heterosis of 113.86 % was exhibited in cross PS-1 × BD-1, followed by

PS-1 × BD-2 and PS-2 × BD-1 with mid-parent heterosis of 99.06 and 59.59. The least mid-

parent heterosis (59.28 %) was manifested for cross PS-2 × BD-2. Better-parent heterosis with

maximum magnitude of 86.35 % was expressed in the cross PS-1 × BD-1, for grains ear-1.

Similarly the minimum better-parent heterosis (30.88 %) was recorded for PS-2 × BD-2.


Both mid and better-parent heterosis calculated for 100 grain weight were of positive

nature. Mid-parent heterosis for 100 grain weight varied from 31.76 to 50.12 % (Table 4.6). It

was indicated that maximum (50.12 %) mid-parent heterosis was exhibited by the cross PS-2 ×

BD-1, followed by cross PS-2 × BD-2 with magnitude of 49.41 % having the same female parent

(PS-2). This heterotic study revealed that maximum better-parent heterosis 57.14 % was

observed for the cross PS-2 × BD-2 while, minimum (31.86 %) better-parent heterosis of

positive nature was exhibited by the cross PS-1 × BD-1 for 100 grain weight.

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The mid and better parent heterosis values regarding expansion volume are provided in

Table 4.6. Both types of heterosis were of negative nature for expansion volume in all cross. The

maximum (-57.33 %) mid-parent heterosis of negative magnitude was calculated for expansion

volume in cross PS-1 × BD-2, followed by cross PS-1 × BD-1, PS-2 × BD-2 and PS-2 × BD-1

with -39.68, -26.99 and -2.56 %, respectively. Similarly better parent heterosis for ear weight

ranged from -60.59 to -6.03 % for the cross PS-1 × BD-2 and PS-1 × BD-1, respectively.


Heterotic values for percent unpopped grains are presented in Table 4.6. It is revealed

from the table that for percent unpopped grain maximum values of both mid and better-parent

heterosis values were calculated for the crosses having PS-1 as female parent. Maximum mid

parent heterosis of -31.72 % was reported for cross PS-1 × BD-2, followed by PS-2 × BD-2, PS-

1 × BD-1 and PS-2 × BD-2 with mid-parent heterosis -30.46, -9.28 and -0.31 %, respectively.

Better-parent heterosis for percent unpopped grains varied from -10.21 to 8.85 %. Maximum

better-parent heterosis of (-10.21 %) with negative magnitude was exhibited by cross PS-2 ×

BD-2, followed by cross PS-1 × BD-1 with 8.85 %. The minimum better parent heterosis of 2.25

% was calculated for the cross PS-1 × BD-2.

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Table 4.6 Mid- parent and best-parent heterosis for four maize crosses evaluated at UOA and CCRI during summer 2013.

Parameters Cross –I Cross-II Cross-III Cross-IV

MPH BPH MPH BPH MPH BPH MPH BPH

Days to tasseling -7.15 -3.46 -5.13 -2.17 -7.02 -3.77 -5.41 -2.89

Days to anthesis -6.52 -3.05 -4.94 -2.22 -6.74 -3.65 -4.67 -2.33

Days to silking -6.35 -2.86 -5.42 -2.30 -6.48 -3.40 -5.07 -2.34

Plant height 12.34 7.48 4.69 1.19 7.33 5.83 11.99 11.60

Ear height -0.13 7.27 -3.13 -2.07 14.31 21.75 8.94 9.24

Days to maturity -2.68 -0.14 -2.91 -0.22 -2.33 0.29 -2.22 0.57

Ear weight 65.08 41.36 80.56 67.10 50.03 46.76 62.44 46.29

Ear diameter 20.54 16.86 26.52 16.39 11.28 8.36 20.74 5.45

Ear length 47.31 37.69 69.28 65.63 35.95 35.44 45.34 33.59

Kernel rows ear-1 30.56 22.97 41.01 40.37 18.56 13.30 21.37 9.11

Grains row-1 64.76 52.09 40.82 30.38 35.52 22.88 32.89 20.14

Grains ear-1 113.86 86.35 99.06 85.03 59.59 36.17 59.28 30.88

100-grain weight 39.58 31.86 31.76 25.00 50.12 58.62 49.41 57.14

Grain yield 70.46 47.22 80.73 62.74 46.56 42.57 55.90 44.88

Expansion volume -39.68 -46.07 -57.33 -60.59 -2.56 -6.03 -26.99 -31.96

Percent unpoped grain -9.28 8.85 -31.72 2.26 -0.31 5.02 -30.46 -10.21

Biological yield 25.92 18.45 28.88 24.59 22.73 22.26 26.03 22.06

Percent shelling 10.19 5.08 10.15 2.73 9.72 7.16 6.09 1.27

Harvest index 36.25 24.35 40.71 30.74 19.41 16.52 23.90 18.63

Cross-I = PS-1 × BD-1, Cross-II = PS-1 × BD-2, Cross-III = PS-2 × BD-1, Cross-IV = PS-2 × BD-2

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Like other yield related traits both mid and better-parent heterosis were of positive

magnitudes for biological yield (Table 4.6). Maximum (28.88 %) mid-parent heterosis was

observed in cross PS-1 × BD-2 for biological yield, followed by cross PS-2 × BD-2, cross PS-1 ×

BD-1 and PS-2 × BD-1 with 26.03, 25.92 and 22.73, respectively. Similarly in better-parent

heterosis maximum (24.59 %) magnitude for biological yield was expressed by cross PS-1 ×

BD-2 while, minimum (18.45 %) better-parent heterosis was calculated for cross PS-1 × BD-1.


The mid-parent heterosis varied from 10.19 to 6.09 % for percent shelling (Table 4.6).

The maximum mid-parent heterosis of 10.19 % was exhibited in cross PS-1 × BD-1, followed by

PS-1 × BD-2 and PS-2 × BD-1 with mid-parent heterosis of 10.15 and 9.72, respectively. The

least mid-parent heterosis (6.09 %) was manifested for cross PS-2 × BD-2. Similarly better-

parent heterosis with maximum magnitude of 7.16 % was expressed in the cross PS-2 × BD-1,

for percent shelling. Likewise, minimum better-parent heterosis (1.27 %) was recorded for PS-2

× BD-2.


Both mid and better-parent heterosis of positive magnitude were observed for harvest

index (Table 4.6). Mid-parent heterosis for harvest index varied from 36.25 to 40.71 %. It was

indicated that maximum (40.71 %) mid-parent heterosis was exhibited by the cross PS-1 × BD-2,

followed by cross PS-1 x BD-1 with magnitude of 36.25 % having the same female parent (PS-

1). Heterotic study revealed that maximum better-parent heterosis of 30.74 % was observed for

the cross PS-1 × BD-2 while, minimum (16.52 %) better-parent heterosis of positive magnitude

was exhibited by the cross PS-2 × BD-1 for harvest index.

4.4Genotypic and phenotypic association among traits

The genetic and phenotypic correlation coefficients among quantitative parameters

determine the efficiency of a breeding program. The knowledge of correlation provide assistance

in the choice of direct or indirect selection (Joshi, 2005; Bocanski et al., 2009).Genetic and

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phenotypic coefficients results obtained in the present study among different flowering, plant,

yield associated and popping characters for four maize crosses i.e., PS-1 × BD-1, PS-1 × BD-2,

PS-2 × BD-1 and PS-2 × BD-2 derived from two diverse groups of contrasting inbred lines are

presented in Table 4.7 through Table 4.10.

4.4.1 Days to tasseling

Positive and significant correlations were observed among the flowering characters both

at genetic and phenotypic level (Table 4.7-4.10). In three crosses i.e., PS-1 × BD-1, PS-1 × BD-2

and PS-2 × BD-2, the magnitude of genetic correlation of days to tasseling was negatively non-

significant with ear weight and grain yield, except PS-2 × BD-1 with magnitude of -0.82 for each

ear weight and grain yield with tasseling (Table 4.9). In cross PS-2 × BD-1 negative and

significant correlation of days to tasseling with ear weight and grain yield with values of -0.78

and -0.79 at phenotypic level (Table 4.9). Similarly in cross PS-2 × BD-2, the phenotypic

association of days to tasseling was of negative nature with significant magnitude (rp= -0.62 and

rP= -0.56). The genotypic correlation of days to tasseling was found negatively significant with

plant height only in two of the four crosses i.e., PS-1 × BD-1 (rg= -0.92) and PS-2 × BD-1 (rg = -

0.93). Genetic correlation was negatively non-significant with all other characters except

expansion volume and number of unpopped grains. Phenotypic correlation of days to tasseling

with ear diameter, ear length, kernels per row, and number of grains per cob in cross. Likewise in

cross PS-1 × BD-2 phenotypic correlation of days tasseling with ear diameter and unpopped

grains was negatively and positively significant, respectively. Genetic correlation of days to

tasseling with grains per row and grains per ear was negatively significant in both cross PS-2 ×

BD-1 and PS-2 × BD-2. In cross PS-2 × BD-1 days to tasseling was significantly correlated with

kernels per row and harvest index at genetic level. Phenotypic correlation of days to tasseling

with ear diameter, ear length, kernel rows, grains per row, grain per cob biological yield and

harvest index was found negatively significant in both crosses i.e. PS-2 × BD-1 and PS-2 × BD-2

days to tasseling was non-significantly correlated with ear height in all the crosses, except PS-1 ×

BD-1 with rg = -0.98. Phenotypic association of days to tasseling with plant height was of

negative nature with significant magnitude in all the crosses. Tasseling was negatively and

significantly correlated at phenotypic level with ear height in the three crosses i.e. PS-1 × BD-1,

PS-2 × BD-1 and PS-2 × BD-2 with magnitudes of -0.65, -0.91 and -0.70, respectively.

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4.4.2 Days to anthesis

Positive and significant correlation was calculated among days to anthesis, silking and

maturity both at genetic and phenotypic level in all crosses (Table 4.7-4.10). Days to anthesis,

number of kernel rows, grains per row and grains per cob were negatively and significantly

correlated at genetic level in cross PS-2 × BD-1 and PS-2 × BD-2. Negatively significant genetic

correlation (rg= -0.84) was observed between days to anthesis and ear diameter in cross PS-2 ×

BD-2. Days to anthesis was negatively and non-significantly correlated with ear weight and grain

yield in all crosses at genetic level. Negatively significant genetic correlation was observed

between days to anthesis and plant height in both crosses i.e. PS-1 × BD-1 (rg = -0.90) and PS-2

× BD-1 (-0.89). In both cross PS-2 × BD-1 and PS-2 × BD-2 phenotypic correlation of days to

anthesis with ear diameter, ear length, kernel rows, grains per row, grains per cob biological

yield and harvest index was negatively significant. A phenotypic correlation of negative nature

with significant magnitude was observed between days to anthesis, plant and ear height in all

four crosses, except PS-1 × BD-2. Negatively phenotypic association of days to anthesis with ear

weight and grain yield was exhibited in both crosses PS-2 × BD-1 (rp = -0.75, -0.76) and PS-2 ×

BD-2 (rp = -0.60, -0.55) having the same female parent. The other two crosses having PS-1 as

female parent showed also negative association but with non-significant magnitude at phenotypic

level among days to anthesis, ear weight and grain yield. Days to anthesis was found positively

and significantly correlated with percent unpopped grains in all crosses except PS-2 × BD-1.

Phenotypic correlation (rp = 0.52) of days to anthesis was positively significant with expansion

volume in cross PS-2 × BD-2.

4.4.3 Days to silking

Association between days to silking and maturity was positively significant both at

genetic and phenotypic level in all crosses (Table 4.7-4.10). Negative and significant association

was calculated between days to silking and plant height in cross PS-1 × BD-1 and PS-2 × BD-1

both, having BD-1 as male parent. Days to silking was negatively but non-significantly

correlated with ear weight and grain yield at genetic level. Phenotypic correlation of days to

silking with plant height, ear height, ear weight and grain yield was negatively significant in

cross PS-2 × BD-1 (rp = -0.78, -0.93, -0.73 and -0.73) and PS-2 × BD-2 (-0.51, -0.71, -0.56 and -

0.48). Similarly in cross PS-1 × BD-1, phenotypic association of days to silking with plant and

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ear height was negative and significant, while in cross PS-1 × BD-2 only plant height was

negatively but significantly correlated with silking. Genetic correlation of days to silking with

kernel rows, grains per row and grains per cob was negatively significant in both crosses PS-2 ×

BD-1 and PS-2 × BD-2. Ear diameter was also found negatively correlated (-0.93) with days to

silking at genetic level in cross PS-2 × BD-2. Both ear weight and grain yield were negatively

but non-significantly correlated with days to silking in cross PS-1 × BD-1 and PS-1 × BD-2.

Phenotypic correlation of days to silking with ear length and unpopped grains was significantly

negative in cross PS-1 × BD-1. Likewise, phenotypic association of days to silking with percent

unpopped grains was positively significant in all crosses except, PS-2 × BD-1. In cross PS-2 ×

BD-1 and PS-2 × BD-2, days to silking was negatively associated with ear diameter, ear length,

kernel rows, grains per row and grains per cob at phenotypic level. Similarly expansion volume

was positively correlated with days to silking in cross PS-2 × BD-2.

4.4.4 Plant height

Genetic correlation of plant height with days to maturity was negative and non-significant

in all crosses except, PS-1 × BD-1 (Table 4.7). Plant height was positively and significantly

correlated with ear weight and grain yield at genotypic level in both crosses i.e. PS-2 × BD-1and

PS-2 × BD-2 with magnitude of (0.97 & 0.89) and (0.97 & 0.96), respectively. Similarly, genetic

correlation between plant and ear height was positive but non-significant in all crosses, except

PS-2 × BD-2 (rg = 0.90). Phenotypic correlation ranging from 0.46 to 0.91 between plant height

and grain yield was of significant nature in all the crosses except, PS-1 × BD-2, where a positive

but non-significant correlation of 0.41 was observed. Genetic association of plant height with all

other traits was positively non-significant except, expansion volume and unpopped grains. In

cross PS-1 × BD-1 phenotypic association of plant height with ear length, grains per row, grains

per cob and hundred grain weight was significant (rp = 0.54, 0.52, 0.52 and 0.48). Plant height

and unpopped grains were negatively correlated at phenotypic level in all crosses except, PS-2 ×

BD-2. Positively significant phenotypic correlation of plant height with ear height and ear weight

is obvious from Table 4.9 in cross PS-2 × BD-1and PS-2 × BD-2. Similarly in cross PS-1 × BD-

2 also showed positive and significant correlation of 0.46 between plant height and ear weight at

phenotypic level. Phenotypic association of plant height with ear characters was positively

significant in cross PS-1 × BD-2 while, negatively significant with unpopped grains (rp = -0.67).

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Genetic correlation of plant height and ear diameter (rg = 0.94) was positively significant in cross

PS-1 × BD-2. Correlation of plant height with ear characteristics, hundred grain weight and

biological yield was positively significant at genotypic level both in cross PS-2 × BD-1 and PS-2

× BD-2. Genetic correlation of plant height with kernels per row and harvest index was also

found positively significant in cross PS-2 × BD-1 and PS-2 × BD-2, respectively. Phenotypic

correlation of plant height with ear length, kernel rows, grains per row, grains per cob, hundred

grain weight, biological yield and harvest index was positively significant in both cross PS-2 ×

BD-1 and PS-2 × BD-2. Plant height was negatively and significantly correlated with expansion

volume and unpopped grains in cross PS-2 × BD-2.

4.4.5 Ear height

Genetic correlation of ear height with days to maturity was negatively significant (rg = -

0.84, -0.90) in cross PS-1 × BD-1 and PS-2 × BD-1 while, in the other two crosses the

association was negative but non-significant (Table 4.7-4.10). Genetic correlation of ear height

with ear weight was non-significant in all the crosses, while positively significant in cross PS-2 ×

BD-2 at phenotypic level. Likewise, phenotypic correlation of ear height with ear weight and

grain yield was positive and significant in cross PS-1 × BD-2 (rp =0.77, 0.71) while, negatively

significant in cross PS-2 × BD-1 (rp = -0.75, -0.74). Genetic association among ear height, kernel

rows, grains per row and grains per cob was positively significant in cross PS-2 × BD-1. Similar

association was also calculated for ear height with grains per row and hundred grain weight in

cross PS-2 × BD-2. Phenotypic correlation of ear height with days to maturity was negative but

significant in all crosses except, PS-1 × BD-2. Correlation between ear height and unpopped

grains was also negative but significant in cross PS-1 × BD-1 at phenotypic level. Phenotypic

correlation of ear height with ear length, kernel rows, grains per row and grains per cob was

significant but of negative nature in cross PS-1 × BD-2 while, positively significant in both cross

PS-2 × BD-1 and PS-2 × BD-2. In cross PS-2 × BD-1 positively significant correlation was

observed among ear height, ear diameter, biological yield and harvest index. Phenotypic

correlation of ear height with biological yield and harvest index was negative but significant in

cross PS-1 × BD-2 while, positively correlated with expansion volume in the same cross. In

contrast association of ear height and expansion volume (rp = -0.51) was negatively significant in

96

cross PS-2 × BD-2. Phenotypic correlation of ear height with unpopped grains was negatively

significant (rp = 0.56) in cross PS-1 × BD-1.

4.4.6 Ear weight

Ear weight was positively and significantly correlated with ear characteristics, grain

yield, biological yield and harvest index in all crosses at genetic level. Genetic correlation of ear

weight with expansion volume was negatively significant in all crosses except, PS-2 × BD-1

where the association was only negative in nature (Table 4.9). Phenotypic association of ear

weight with percent shelling was positive and significant in three of the four crosses. High

magnitude of positive and significant correlation was observed in all the crosses between ear

weight and grain yield both at genetic (rg = 0.98, 0.99, 0.96 and 0.99, respectively) and

phenotypic (rp = 0.98, 0.99, 0.95 and 0.97, respectively) level. Likewise phenotypic association

of ear weight with expansion volume was negatively significant in all crosses except PS-2 × BD-

1. Ear weight was significantly correlated (rp = -0.66) with unpopped grain in cross PS-2 × BD-2

at phenotypic level. Correlation of ear weight with yield related traits ranged from 0.68 to 0.99.

Highly positive and significant correlation of ear weight was observed with ear length, ear

diameter, kernel rows, grains per row, grains per cob, biological yield and harvest index in all

four studied crosses at phenotypic level.

97

Table 4.7 Phenotypic (above diagonal) and genotypic (below diagonal) correlation among flowering, plan and yield

parameters in Cross I (PS-1 × BD-1).

Traits DT DA DS PH EH DM FWT %Shell ED EL NKR NGPR NGPC HGWT GYLD BYLD HI Exp.Vol %Unpop

DT 1 0.98** 0.97** -.82** -.65** .93** -0.35 -0.18 -.48* -.49* -.47* -0.44 -.49* -0.43 -0.36 -0.35 -0.31 0.34 0.44

DA 0.99** 1 0.99** -.83** -.66** .92** -0.33 -0.16 -0.43 -.48* -0.45 -0.39 -0.45 -0.4 -0.32 -0.34 -0.26 0.35 0.42

DS 0.99** 0.99** 1 -.85** -.67** .93** -0.29 -0.12 -0.4 -.46* -0.41 -0.36 -0.42 -0.37 -0.29 -0.3 -0.23 0.31 0.46*

PH -0.93** -0.90** -0.90** 1 0.41 -.80** 0.39 0.07 0.38 .54* 0.36 .52* .52* .48* 0.43 0.39 0.37 -0.25 -.49*

EH -0.69 -0.70 -0.71 0.41 1 -.81** -0.36 -0.28 -0.05 -0.09 -0.12 -0.25 -0.19 -0.17 -0.36 -0.34 -0.41 0.24 -.56*

DM 0.95** 0.94** 0.95** -0.86* -0.84* 1 -0.04 0.13 -0.2 -0.24 -0.16 -0.18 -0.22 -0.22 -0.05 -0.04 -0.01 0.02 .64**

FWT -0.36 -0.34 -0.31 0.44 -0.37 -0.05 1 .81** .81** .87** .93** .89** .93** .86** 0.97** .99** .94** -.94** 0.4

%Shell -0.23 -0.23 -0.2 0.17 -0.33 0.08 0.92** 1 .81** .77** .87** .71** .77** .71** 0.78** .82** .77** -.86** .46*

ED -0.52 -0.47 -0.44 0.45 -0.07 -0.26 0.86* 0.94** 1 .90** .89** .84** .90** .76** 0.85** .81** .83** -.78** 0.14

EL -0.58 -0.56 -0.53 0.56 -0.12 -0.3 0.94** 0.95** 0.98** 1 .89** .90** .94** .87** 0.89** .89** .85** -.82** 0.09

NKR -0.48 -0.47 -0.44 0.43 -0.14 -0.18 0.94** 0.99** 0.96** 0.99** 1 .84** .91** .86** 0.89** .92** .87** -.93** 0.28

NGPR -0.49 -0.43 -0.41 0.59 -0.26 -0.22 0.94** 0.80* 0.92** 0.94** 0.89* 1 .98** .89** 0.96** .91** .95** -.77** 0.14

NGPC -0.53 -0.48 -0.45 0.58 -0.2 -0.25 0.94** 0.87* 0.96** 0.98** 0.94** 0.99** 1 .91** 0.97** .94** .95** -.83** 0.14

HGWT -0.53 -0.49 -0.45 0.57 -0.22 -0.23 0.98** 0.92** 0.99** 0.99** 0.98** 0.99** 0.99** 1 0.87** .87** .84** -.74** 0.07

GYLD -0.38 -0.34 -0.31 0.49 -0.37 -0.09 0.98** 0.88* 0.89* 0.95** 0.92** 0.98** 0.97** 0.99** 1 .97** .99** -.87** 0.3

BYLD -0.38 -0.37 -0.33 0.44 -0.35 -0.07 0.99** 0.91** 0.86* 0.94** 0.95** 0.93** 0.94** 0.97** 0.98** 1 .94** -.93** 0.4

HI -0.32 -0.27 -0.24 0.45 -0.43 -0.03 0.97** 0.88* 0.89* 0.94** 0.90* 0.98** 0.97** 0.99** 0.99** 0.97** 1 -.83** 0.29

Exp.Vol 0.35 0.36 0.33 -0.32 0.25 0.04 -0.94** -0.94** -0.80* -0.89* -0.95** -0.79 -0.83* -0.88* -0.87* -0.95** -0.84* 1 -.54*

%Unpop 0.5 0.46 0.51 -0.51 -0.63 0.7 0.44 0.46 0.07 0.13 0.32 0.14 0.15 0.20 0.32 0.43 0.31 -0.55 1

DT = days to tasseling, DA = days to anthesis, DS = days to silking, PH = plant height, EH = ear height, DM = days to maturity, FWT

= fresh ear weight, %Shell = % shelling, ED = ear diameter, EL = ear length, NKR = kernel rows ear-1, NGPR = grains per row,

NGPC = grains per ear, HGWT = hundred grain weight, GYLD = grain yield, BYLD = biological yield, HI = harvest index, Exp. Vol

= expansion volume and %Unpop = % unpopped grains

98


Genetic correlation of days to maturity was negatively non-significant in nature with all

traits except, percent shelling, expansion volume and unpopped grains in cross PS-1 × BD-1

(Table 4.7). In cross PS-1 × BD-2 genetic association of days to maturity with percent unpopped

grains was positively significant (0.80) in nature while, positive but non-significantly correlated

with percent shelling, grains per row, grains per cob, grain yield, biological yield, harvest index

and popping expansion. Phenotypic correlation of days to maturity was non-significant with

most of the studied traits except, expansion volume in cross PS-1 × BD-1 and PS-1 × BD-2.

Genetic correlation of days to maturity was negatively significant with grains per row and grains

per cob in cross PS-2 × BD-1 while positively non-significant with expansion volume and

unpopped grains. Similarly in cross PS-2 × BD-2 genetic correlation of days to maturity was also

negative and significant with ear diameter, kernel rows, grains per row and grains per cob.

Phenotypic correlation of days to maturity was negatively significant with ear diameter, kernel

rows, grains per row and grains per cob in both crosses PS-2 × BD-1and PS-2 × BD-2. Days to

maturity was positively and significantly correlated with unpopped grains at phenotypic level in

cross PS-2 × BD-2.


Both genetic and phenotypic associations are presented in Table 4.7-4.10. Shelling

percentage was positive and significantly correlated with ear diameter, ear length, kernel rows,

grains per row, grains per cob, hundred grain weight, grain yield, biological yield and harvest

index at genetic level while, genetic correlation with expansion volume was negatively

significant in cross PS-1 × BD-1. In both cross PS-2 × BD-2 and PS-1 × BD-2, genetic

correlation of shelling percentage with all other traits was positive but non-significant except,

expansion volume in both crosses and unpopped grains in later one. Genetic correlation was

positively significant among shelling percentage, ear length, hundred grain weight, grain yield,

biological yield and harvest index in cross PS-2 × BD-1. Like all other crosses genetic

association between shelling percentage and expansion volume was negative and non-significant.

Phenotypic correlation of shelling percentage with expansion volume was negative but

significant in two crosses (PS-1 × BD-1 and PS-1 × BD-2) while, negative but non-significant in

other two crosses (PS-2 × BD-1 and PS-2 × BD-2). Phenotypically shelling percentage was

99

positively and significantly correlated with ear diameter, ear length, number of kernel rows,

grains per row, grains per cob, hundred grain weight, grain yield, biological yield, harvest index

and unpopped grains in cross PS-1 × BD-1. Similar positive and significant correlation of

shelling percentage with yield, yield related and ear related traits was observed in cross PS-1 ×

BD-2. In cross PS-2 × BD-2 phenotypic correlation of shelling percentage with other traits was

non-significant. Positive and significant correlation was observed among shelling percentage, ear

length, hundred grain weight, grain yield, biological yield, harvest index and percent unpopped

grains in cross PS-2 × BD-1.

4.4.9 Ear diameter

The genetic correlation of ear diameter in cross PS-1 × BD-1 with ear length, kernel

rows, grains per row, grains per cob, hundred grain weight, grain yield, biological yield and

harvest index was significantly positive as 0.98, 0.96, 0.92, 0.96, 0.98, 89, 0.86 and 0.89,

respectively Table 4.7-4.10. Ear diameter and expansion volume were negatively significant (rg =

-0.80) at genetic level in cross PS-1 × BD-1. Both in cross PS-2 × BD-1 and PS-2 × BD-2

genetic correlation of ear diameter with kernel rows, grains per row and grains per cob were

positively significant (rg = 0.94, 0.91, 0.92 and 0. 97, 0.98, 0.96). In cross PS-2 × BD-2 ear

diameter and unpopped grains were negatively and significantly correlated with each other,

similar negative association with non-significant nature between these traits was also observed in

cross PS-2 × BD-1. Genetic association among ear diameter, ear length, kernel rows and grains

per cob was positively significant in cross PS-1 × BD-2. Phenotypic correlation in both cross PS-

1 × BD-1 and PS-1 × BD-2 of ear diameter was positively significant with traits except,

expansion volume where that association was negative and significant. Ear diameter and percent

unpopped grains were negatively significant at phenotypic level (rp = -0.54) in cross PS-1 × BD-

2. In cross PS-2 × BD-1 ear diameter was positively and significantly correlated with kernel

rows, grains per row, grains per cob and hundred grain weight while, negatively associated with

unpopped grains. Similarly in cross PS-2 × BD-2 phenotypic correlation among ear diameter, ear

length, kernel rows, grains per row, grains per cob, grain yield, biological yield and harvest index

was positively significant. Both expansion volume and percent unpopped grains were negatively

correlated (rp = -0.62, -0.89) with ear diameter in cross PS-2 × BD-1.

100


parameters in Cross II (PS-1 × BD-2).


DT 1 0.99** 0.99** -0.55* -0.24 0.09** -0.03 0.2 -0.47* -0.34 -0.19 0.13 -0.04 -0.35 -0.05 -0.02 -0.02 0.23 0.68**

DA 0.99** 1 0.99** -0.53* -0.28 0.95** -0.01 0.18 -0.45 -0.33 -0.17 0.135 -0.03 -0.35 -0.03 0.01 -0.01 0.22 0.66**

DS 0.99** 0.99** 1 -0.57* -0.28 0.96** -0.03 0.19 -0.48* -0.36 -0.19 0.12 -0.05 -0.34 -0.05 -0.02 -0.02 0.22 0.72**

PH -0.65 -0.62 -0.66 1 -0.11 -0.60** 0.46 -0.07 0.88** 0.67** 0.59** 0.37 0.51* 0.33 0.404 0.44 0.33 -0.44 -0.67**

EH -0.25 -0.28 -0.28 -0.18 1 -0.4 -0.74** -0.36 -0.42 -0.52* -0.68** -0.64** -0.66** -0.54* -0.74** -0.75** -0.75** 0.68** -0.23

DM 0.97** 0.97** 0.98** -0.69 -0.42 1 0.07 0.3 -0.46 -0.27 -0.1 0.19 0.03 -0.21 0.06 0.08 0.1 0.08 0.76**

FWT -0.04 -0.02 -0.04 0.51 -0.77 0.07 1 0.66** 0.77** 0.91** 0.94** 0.92** 0.96** 0.81** 0.98** 0.99** 0.96** -0.93** -0.08

%Shell 0.21 0.18 0.19 -0.13 -0.42 0.33 0.69 1 0.23 0.58* 0.56* 0.75** 0.67** 0.66** 0.68** 0.67** 0.71** -0.69** 0.37

ED -0.52 -0.5 -0.53 0.94** -0.43 -0.50 0.78 0.23 1 0.88** 0.87** 0.67** 0.81** 0.62** 0.72** 0.75** 0.66** -0.74** -0.54*

EL -0.38 -0.37 -0.39 0.7 -0.57 -0.29 0.94** 0.61 0.92** 1 0.92** 0.82** 0.90** 0.82** 0.89** 0.90** 0.86** -0.91** -0.3

NKR -0.22 -0.2 -0.21 0.68 -0.69 -0.12 0.97** 0.60 0.89* 0.99** 1 0.87** 0.96** 0.77** 0.93** 0.94** 0.91** -0.93** -0.17

NGPR 0.11 0.12 0.10 0.41 -0.68 0.19 0.98** 0.79 0.70 0.90** 0.94** 1 0.97** 0.71** 0.90** 0.92** 0.88** -0.83** 0.03

NGPC -0.07 -0.06 -0.08 0.56 -0.69 0.01 0.99** 0.71 0.81* 0.96** 0.98** 0.98** 1 0.76** 0.94** 0.96** 0.92** -0.91** -0.1

HGWT -0.36 -0.36 -0.35 0.42 -0.63 -0.17 0.87* 0.76 0.71 0.94** 0.90** 0.80* 0.87* 1 0.84** 0.82** 0.84** -0.92** -0.06

GYLD -0.05 -0.03 -0.05 0.45 -0.77 0.08 0.99** 0.73 0.75 0.93** 0.94** 0.96** 0.97** 0.91** 1 0.98** 0.99** -0.92** -0.07

BYLD -0.02 -0.01 -0.02 0.48 -0.77 0.09 0.99** 0.71 0.76 0.93** 0.96** 0.98** 0.99** 0.87* 0.99** 1 0.97** -0.93** -0.06

HI -0.01 0.01 -0.01 0.39 -0.79 0.12 0.99** 0.76 0.70 0.91** 0.92** 0.96** 0.96** 0.92** 0.99** 0.99** 1 -0.93** -0.02

Exp.Vol 0.23 0.22 0.22 -0.48 0.71 0.07 -0.93** -0.74 -0.76 -0.95** -0.96** -0.89* -0.94** -0.98** -0.94** -0.94** -0.94** 1 0.02

%Unpop 0.7 0.67 0.73 -0.76 -0.25 0.80* -0.10 0.38 -0.58 -0.33 -0.18 0.02 -0.11 -0.08 -0.09 -0.07 -0.03 0.02 1



NGPC = grains per cob, HGWT = hundred grain weight, GYLD = grain yield, BYLD = biological yield, HI = harvest index, Exp. Vol


101

4.4.10 Ear length

Both the genetic and phenotypic correlations are presented in Table 4.7-4.10 for four

studied crosses. Genetic correlation of ear length was positively high and significant with

number of kernel rows, grains per row, grains per cob, hundred grain weight, grain yield,

biological yield and harvest index in cross PS-1 × BD-1 and PS-1 × BD-2, while negative and

significant correlation was obvious between ear length and expansion volume in the same two

crosses. Similarly phenotypic correlation of ear length with other traits was also of the same

pattern in these two crosses (PS-1 × BD-1 and PS-1 × BD-2). Phenotypic correlation of ear

length with percent unpopped grains was negative and non-significant in both crosses (PS-1 ×

BD-1 and PS-1 × BD-2). Genetic correlation of ear length was positively significant with

hundred grain weight, grain yield, biological yield and harvest index in cross PS-2 × BD-1.

Similarly phenotypic correlation in cross PS-2 × BD-1 was also positive and significant among

ear length, kernel rows, grains per row, grains per cob, hundred grin weight, grain yield,

biological yield and harvest index. Both genotypic and phenotypic correlations of ear length with

kernel rows, grains per row, grains per cob, grain yield, biological yield and harvest index were

positively significant in cross PS-2 × BD-2 while, negatively and significantly correlated with

expansion volume. Phenotypic correlation of ear length with percent unpopped grains was also

negatively significant in cross PS-2 × BD-2.

4.4.11 Kernel rows-1

Associations, both at genetic and phenotypic level among number of kernel rows, number

of grains per row, number of grains per cob, hundred grain weight, grain yield, biological yield

and harvest index were positively high and significant in cross PS-1 × BD-1 and PS-1 × BD-2

(Table 4.7-4.10). Genetic and phenotypic association between number of kernel rows and

expansion volume were negatively significant in both these crosses PS-1 × BD-1 and PS-1 ×

BD-2, having female parent in common. In cross PS-2 × BD-1 genetic correlation of number of

kernel rows was positively significant only with number of grains per row and number of grains

per row while, phenotypic correlation was positively significant with all yield related traits

except, expansion volume and unpopped grains. Genetic correlation of number of kernel rows

with number of grains per row, number of grains per cob and biological yield was quite high

with positive and significant nature in cross PS-2 × BD-2. Genetic and phenotypic correlations

102

between number of kernel rows and percent unpopped grains were negatively significant in cross

PS-2 × BD-2. Number of kernel rows per ear was also negatively and significantly correlated

with expansion volume in cross PS-2 × BD-2 at phenotypic level while, positively and

significantly correlated with number of grains per row, number of grains per cob, hundred grain

weight, grain yield, biological yield and harvest index in the same cross.

4.4.12 Grains row-1

Genetic correlation of number of grains per row was positive and significant with number

of grains per cob, hundred grain weight, grain yield, biological yield and harvest index in cross

PS-1 × BD-1 and PS-1 × BD-2 (Table 4.7-4.10). Number of grains per row was negatively and

significantly correlated with expansion volume in cross PS-1 × BD-2 while, genetic correlation

between same traits in cross PS-1 × BD-1 was negative but non-significant. Similarly phenotypic

association among number of grains per row, grains per cob, hundred grain weight, grain yield,

biological yield and harvest index was high and positively significant in both cross PS-1 × BD-1

and PS-1 × BD-2. Number of grains per row was negatively and non-significantly correlated

with expansion volume in both cross PS-1 × BD-1 and PS-1 × BD-2. Genetic association of

number of grains per row with number of grains per cob and biological yield in cross PS-2 ×

BD-1 and PS-2 × BD-2 was positive and significant in nature. Phenotypic correlation among

number of grains per row, number of grains per cob, hundred grain weight, grain yield,

biological yield and harvest index was positive in magnitude and significant in nature in both

cross PS-2 × BD-1 and PS-2 × BD-2. Genetic correlation of grains per row and percent

unpopped grains was negatively significant while, phenotypic correlation among number of

grains per row, expansion volume and percent unpopped grains was also negative and significant

in cross PS-2 × BD-2.

103


parameters in Cross III (PS-2 × BD-1).


DT 1 0.98** 0.98** -0.80** -0.91** 0.86** -0.78** -0.3 -0.56* -0.66** -0.83** -0.75** -0.80** -0.53* -0.78** -0.74** -0.76** 0.36 0.12

DA 0.99** 1 0.99** -0.79** -0.93** 0.89** -0.75** -0.3 -0.65** -0.63** -0.87** -0.79** -0.84** -0.55* -0.76** -0.71** -0.75** 0.24 0.18

DS 0.99** 0.99** 1 -0.78** -0.93** 0.89** -0.73** -0.27 -0.64** -0.61** -0.86** -0.78** -0.84** -0.53* -0.74** -0.69** -0.73** 0.23 0.18

PH -0.93** -0.89* -0.89* 1 0.88** -0.57* 0.91** 0.44 0.44 0.70** 0.76** 0.85** 0.86** 0.77** 0.85** 0.91** 0.73** -0.29 0.07

EH -0.98** -0.99** -0.99** 0.90* 1 -0.86** 0.77** 0.27 0.67** 0.59** 0.87** 0.90** 0.93** 0.65** 0.72** 0.73** 0.65** -0.11 -0.2

DM 0.88* 0.90** 0.92** -0.64 -0.90** 1 -0.44 -0.04 -0.63** -0.33 -0.73** -0.65** -0.70** -0.23 -0.45 -0.39 -0.46 0.09 0.32

FWT -0.83** -0.79 -0.78 0.97** 0.79 -0.45 1 0.63** 0.43 0.86** 0.77** 0.74** 0.79** 0.85** 0.94** 0.98** 0.82** -0.37 0.22

%Shell -0.56 -0.54 -0.51 0.64 0.44 -0.07 0.86* 1 0.25 0.74** 0.44 0.24 0.33 0.57* 0.69** 0.64** 0.68** -0.28 0.47*

ED -0.63 -0.73 -0.75 0.58 0.80 -0.68 0.52 0.32 1 0.38 0.75** 0.66** 0.75** 0.55* 0.39 0.38 0.34 0.42 -0.3

EL -0.73 -0.70 -0.67 0.82* 0.65 -0.33 0.92** 0.99** 0.36 1 0.62** 0.53* 0.59** 0.79** 0.88** 0.86** 0.82** -0.45 0.09

NKR -0.88* -0.94** -0.93** 0.83* 0.93** -0.78 0.79 0.63 0.94** 0.66 1 0.78** 0.90** 0.64** 0.75** 0.74** 0.68** -0.01 -0.07

NGPR -0.97** -0.99** -0.99** 0.94** 0.99** -0.86* 0.86* 0.52 0.91** 0.70 0.99** 1 0.97** 0.73** 0.64** 0.68** 0.55* 0.04 -0.08

NGPC -0.91** -0.94** -0.95** 0.89* 0.97** -0.80* 0.83* 0.56 0.92** 0.68 0.99** 0.99** 1 0.76** 0.71** 0.74** 0.61** 0.06 -0.1

HGWT -0.64 -0.64 -0.63 0.86* 0.68 -0.29 0.92** 0.87* 0.62 0.87* 0.76 0.80 0.80 1 0.77** 0.85** 0.61** -0.01 0.04

GYLD -0.82* -0.78 -0.77 0.89* 0.73 -0.45 0.97** 0.96** 0.45 0.94** 0.79 0.77 0.77 0.82** 1 0.95** 0.96** -0.50* 0.23

BYLD -0.79 -0.75 -0.74 0.95** 0.74 -0.40 0.99** 0.88* 0.45 0.92** 0.75 0.83* 0.79 0.91* 0.97** 1 0.84** -0.42 0.22

HI -0.80* -0.77 -0.75 0.77 0.66 -0.47 0.88* 0.96** 0.39 0.91* 0.77 0.66 0.68 0.67 0.96** 0.88* 1 -0.57* 0.24

Exp.Vol 0.36 0.24 0.22 -0.34 -0.12 0.08 -0.38 -0.44 0.47 -0.47 0.01 -0.02 0.04 -0.03 -0.51 -0.42 -0.60 1 -0.39

%Unpop 0.03 0.13 0.14 0.15 -0.24 0.42 0.30 0.25 -0.48 0.20 -0.11 -0.27 -0.21 0.04 0.43 0.38 0.47 -0.75 1





104

4.4.13 Grains ear-1

Genetic correlation of grains per cob was positive and significant in nature with hundred

grain weight, grain yield, biological yield and harvest index in cross PS-1 × BD-1. Number of

grains per cob and expansion were negatively and significantly correlated with each other at

genetic level in cross PS-1 × BD-1 (Table 4.9). Phenotypic correlation among number of grains

per cob, hundred grain weight, grain yield, biological yield and harvest index in cross PS-1 ×

BD-2 was highly positive in magnitude with significant nature, phenotypic association between

number of grains per cob and expansion volume was negative and significant in the same cross.

Genetically grains per cob was positively and significantly correlated with ear weight, ear

diameter, ear length, number of kernel rows and number of grains per row in three of the four

crosses. Number of grains per cob was found to have a negatively significant correlation with

days to tasseling, silking, anthesis and maturity both at genetic and phenotypic level in cross PS-

2 × BD-1 and PS-2 × BD-2. Genetic correlation of number of grains per cob was non-significant

with yield, yield related traits, expansion volume and percent unpopped grains in cross PS-2 ×

BD-1. Similarly in cross PS-2 × BD-2 genetic and phenotypic correlations between number of

grains per cob and percent unpopped grains was negatively significant. Phenotypic correlation

among number of grains per cob, hundred grain weight, grain yield, biological yield and harvest

index was positive and significant in nature in cross PS-2 × BD-2.


Association of hundred grain weight with all other studied traits in four crosses is

presented in Tables 5.4.1-4.9. Genetic correlation of hundred grain weight was positive and

significant with grain yield, biological yield and harvest index in cross PS-1 × BD-1 and PS-1 ×

BD-2. Similar genetic correlation of hundred grain weight was also exhibited with fresh ear

weigh, percent shelling, ear diameter, ear length, number of kernel rows, number of grains per

row and number of grains per cob in cross PS-1 × BD-1. Hundred grain weight was positively

and significantly correlated with grain yield, biological yield, harvest index, grains per row,

grains per cob, number of kernel rows, ear length, ear diameter, percent shelling and fresh weight

in cross PS-1 × BD-1. Genetic association of hundred grain weight with ear weight, ear length,

number of kernel rows, number of grains per row and number of grains per cob was also found

positive and significant in cross PS-1 × BD-2. Phenotypic correlation of hundred grain weight

105

was negatively significant in nature with days to maturity and expansion volume in cross PS-1 ×

BD-2. In cross PS-2 × BD-1 genetic correlation among hundred grain weight, grain yield and

biological yield was positively significant in nature. Phenotypic association in both cross PS-2 ×

BD-1 and PS-2 × BD-2 was positive and significant among hundred grain weight, grain yield,

biological yield and harvest index.

4.4.15 Grain yield

Genetic and phenotypic correlation of grain yield with biological yield and harvest index

was positive and significant in all crosses (Table 4.7-4.10). Grain yield was negatively and

significantly correlated with expansion volume in all crosses except, PS-2 × BD-1 and PS-2 ×

BD-2 where the association was although negative in magnitude but non-significant in nature.

Similarly phenotypic association between grain yield and expansion volume was negatively

significant in all crosses. In cross PS-2 × BD-2 phenotypic association between grain yield and

percent unpopped grains was negatively significant. Genetic correlation among grain yield, fresh

ear weight, percent shelling, ear diameter, ear length, number of kernel rows, number of grains

per row, number of grains per cob and hundred grain weight was positive and significant in cross

PS-1 × BD-1. Same pattern of genetic correlation was also manifested among grain yield, fresh

ear weight, ear length, number of kernel rows, number of grains per row, number of grains per

cob and hundred grain weight in cross PS-1 × BD-2. Positive and significant correlation was

present among grain yield, fresh ear weight, percent shelling, ear diameter, ear length, number of

kernel rows, number of grains per row, number of grains per cob and hundred grain weight in

cross PS-1 × BD-2. Both genetic and phenotypic correlation of grain yield with days to tasseling,

silking and anthesis was negative in nature in all crosses. Genetic and phenotypic association of

grain yield with other grain yield related traits was positive.

106


parameters in Cross IV (PS-2 × BD-2).


DT 1 0.99** 0.97** -0.57* -0.70** 0.87** -0.63** 0.18 -0.77** -0.61** -0.81** -0.78** -0.83** -0.43 -0.56* -0.59* -0.51* 0.55* 0.56*

DA 0.99** 1 0.97** -0.54* -0.69** 0.88** -0.59** 0.2 -0.76** -0.58* -0.79** -0.77** -0.82** -0.4 -0.54* -0.56* -0.48* 0.52* 0.55*

DS 0.97** 0.97** 1 -0.51* -0.71** 0.92** -0.56* 0.15 -0.82** -0.57* -0.81** -0.81** -0.85** -0.4 -0.47* -0.51* -0.41 0.51* 0.65**

PH -0.62 -0.59 -0.58 1 0.60** -0.31 0.94** 0.41 0.61** 0.93** 0.73** 0.73** 0.77** 0.80** 0.92** 0.94** 0.85** -0.73** -0.57*

EH -0.76 -0.75 -0.79 0.59 1 -0.54* 0.47* 0.22 0.55* 0.47* 0.57* 0.72** 0.73** 0.73** 0.35 0.46 0.2 -0.51* -0.36

DM 0.89* 0.89* 0.95** -0.33 -0.60 1 -0.41 0.34 -0.86** -0.43 -0.79** -0.71** -0.77** -0.18 -0.31 -0.34 -0.26 0.43 0.69**

FWT -0.66 -0.63 -0.60 0.97** 0.49 -0.42 1 0.23 0.68** 0.97** 0.79** 0.72** 0.77** 0.73** 0.97** 0.97** 0.92** -0.83** -0.66**

%Shell 0.13 0.16 0.09 0.47 0.30 0.37 0.25 1 -0.11 0.19 -0.11 0.09 0.04 0.45 0.23 0.25 0.18 0.02 0.03

ED -0.84 -0.84* -0.93** 0.61 0.58 -0.92* 0.70 -0.11 1 0.70** 0.96** 0.82** 0.91** 0.41 0.59* 0.62** 0.54* -0.62** -0.89**

EL -0.64 -0.61 -0.60 0.97** 0.48 -0.43 0.99** 0.27 0.73 1 0.81** 0.77** 0.81** 0.70** 0.94** 0.96** 0.88** -0.83** -0.71**

NKR -0.85 -0.84* -0.89* 0.76 0.59 -0.83* 0.84* -0.01 0.97** 0.87* 1 0.83** 0.93** 0.51* 0.73** 0.76** 0.67** -0.71** -0.87**

NGPR -0.91* -0.89* -0.95** 0.83* 0.81* -0.84* 0.84* 0.17 0.99** 0.85* 0.99** 1 0.97** 0.62** 0.64** 0.72** 0.53* -0.65** -0.73**

NGPC -0.88* -0.86* -0.93** 0.81* 0.75 -0.83* 0.83* 0.13 0.96** 0.84* 0.99** 0.99** 1 0.63** 0.69** 0.76** 0.59** -0.70** -0.80**

HGWT -0.48 -0.45 -0.46 0.87* 0.81* -0.20 0.75 0.56 0.42 0.76 0.54 0.72 0.67 1 0.65** 0.75** 0.50* -0.77** -0.32

GYLD -0.59 -0.56 -0.50 0.95** 0.36 -0.31 0.98** 0.26 0.59 0.97** 0.75 0.74 0.72 0.66 1 0.97** 0.97** -0.75** -0.58*

BYLD -0.62 -0.59 -0.56 0.99** 0.47 -0.35 0.99** 0.32 0.65 0.99** 0.81* 0.81* 0.79 0.77 0.99** 1 0.90** -0.81** -0.62**

HI -0.55 -0.52 -0.45 0.88* 0.21 -0.28 0.94** 0.18 0.55 0.94** 0.71 0.66 0.65 0.53 0.98** 0.96** 1 -0.65** -0.55*

Exp.Vol 0.58 0.55 0.54 -0.79 -0.57 0.44 -0.85* -0.01 -0.65 -0.86* -0.75 -0.76 -0.75 -0.79 -0.75 -0.83* -0.67 1 0.59**

%Unpop 0.59 0.57 0.69 -0.59 -0.35 0.73 -0.69 -0.01 -0.95** -0.73 -0.93** -0.88* -0.87* -0.38 -0.59 -0.64 -0.56 0.62 1





107


The association of biological yield was positive and significant with harvest index in all

crosses at genetic level (Table 4.7-4.10). Genetic correlation of biological yield with expansion

volume was negatively significant in all crosses except, PS-2 × BD-1 where the association was

also negative but non-significant in nature. Phenotypic correlation of biological yield with

harvest index was positively significant in four studied crosses while, negative and significant

with expansion volume in all crosses except, cross PS-2 × BD-1. In cross PS-2 × BD-2

phenotypic correlation between biological yield and percent unpopped grains was also negatively

significant. Phenotypic correlation of biological yield was positively significant with fresh ear

weight, ear diameter, eat length, number of kernel rows, number of grains per row, number of

grains per cob, hundred grain weight, grain yield and biological yield in all crosses. Phenotypic

correlation among biological yield, days to tasseling, silking and anthesis was negatively

significant in both cross PS-2 × BD-1 and PS-2 × BD-2 while, in other two crosses the

association was although negative but non-significant in nature.


The genetic association of harvest index with expansion volume was negative and

significant in both cross PS-1 × BD-1 and PS-1 × BD-2, having female parent in common.

Similarly the genetic correlation of harvest index with percent unpopped grains in all crosses was

negative but non-significant in nature (Table 4.7-4.10). Phenotypic correlation of harvest index

and expansion volume was negative and significant in all crosses while, negative and non-

significant with percent unpopped grains. Phenotypic and genotypic correlation of harvest index

and maturity traits was negative in nature in all crosses while, positive with yield related traits.

Genetic association of harvest index with fresh ear weight, ear length, number of kernel rows,

number of grains per row, number of grains per cob, hundred grain weight, grain yield and

biological yield was positive and significant in cross PS-1 × BD-1 and PS-1 × BD-2. Similarly in

cross PS-2 × BD-1 and PS-2 × BD-2 genetic association among harvest index, fresh ear weight,

ear length, grain yield and biological yield was positive and significant. Phenotypic association

of harvest index with yield related traits like fresh ear weight, percent shelling, ear diameter, ear

length, hundred grain weight, grain yield and biological yield was positive and significant in all

crosses.

108


Both genetic and phenotypic associations of expansion volume with all other studied

characters are presented in Table 4.7-4.10. Genetic correlation of expansion volume was

negatively significant with fresh ear weight, percent shelling, ear diameter, ear length, number of

kernel rows, number of grains per cob, hundred grain weight, grain yield, biological yield and

harvest index in cross PS-1 × BD-1. Similarly, negative and significant pattern of genetic

correlation was also observed in cross PS-1 × BD-2 expansion volume and all yield related traits

except percent shelling and ear diameter where the association was negative but non-significant.

In cross PS-2 × BD-1, genetic correlation of expansion volume with all other traits was non-

significant in nature while, phenotypic correlation of expansion volume with grain yield and

harvest index was negative and non-significant in the same cross. In cross PS-2 × BD-2, genetic

correlation of expansion volume with fresh ear weight, ear length and biological yield was

negative and significant in nature. Phenotypic correlation among all yield related traits and

expansion volume was negative and significant in all crosses except, PS-2 × BD-1. Although

both genetic and phenotypic correlations of expansion volume with days to tasseling, silking and

anthesis were positive, but only significant in cross PS-2 × BD-2 at phenotypic level.


A variable nature of genetic correlation of percent unpopped grains was observed with

yield and related traits in all crosses (Table 4.7-4.10). Genetic correlation of percent unpopped

grains was non-significant with all studied traits in all crosses except, PS-2 × BD-2. In cross PS-

2 × BD-2 genetic association among percent unpopped grains, ear diameter, number of kernel

rows per ear, number of grains per row and number of grains per cob was negative and

significant in nature (Table 4.7-4.10). Phenotypic correlation of percent unpopped grains was

non-significant with all studied characters except, percent shelling (rp = 0.47) in cross PS-2 ×

BD-1. In cross PS-1 × BD-1 phenotypic correlation of percent unpopped grains was negative and

significant with plant height, ear height and expansion volume while, positively significant with

days to silking (rp = 0.46) and maturity (rp = 0.64). Positive and significant correlation was

observed among unpopped grains, days to tasseling, silking, anthesis and maturity at phenotypic

level in cross PS-1 × BD-2 and PS-2 × BD-2. Phenotypic association of unpopped grains with

plant height, fresh ear weight, ear diameter, ear length, number of kernel rows, number of grains

109

per row, number of grains per cob, biological yield and harvest index was negative and

significant in nature.

110

Chapter 5

DISCUSSION

5.1 Gene action

Generation mean analysis is a genetic model developed to measure the genetic estimates

including additive, dominance and epistasis effects in breeding populations (Kearsey and Pooni,

2004). Though generation mean analysis is useful in measuring the genetic effects quantitative

traits but, its ability to calculate the epistatic genetic effects including additive × additive (aa),

dominance × dominance (dd) and additive × dominance (ad) effects make it superior over other

methods (Singh and Singh, 1992). Generation mean analysis makes the breeder able to choose an

appropriate breeding method by disclosing information of additive, dominance and epistasis

effects. Along with genetic information of a trait plant breeder is also interested to have

knowledge genetic and environmental variations, because selection mainly depends on additive

genetic variance, influence of the environment and interaction between genotype and

environment. It is the information obtained through generation mean analysis which allows the

breeder to optimize their breeding programs (Melchinger et al., 1986). The choice of selection

and breeding procedures for genetic improvement of maize or any other crop depends largely on

the knowledge of type of gene action for different characters in the plant materials under

investigation. Mather and Jinks (1982) developed generation mean analysis to determine the

genetic effects for polygenic traits. Breeding for improved varieties requires a thorough

understanding of the genetic mechanisms governing yield and yield components (Unay et al.,

2004). The present study was therefore, designed to estimate the magnitude of different genetic

effects (additive, dominance and epistatic) in six generations (P1, P2, F1, F2, BC1 and BC2),

derived from four maize inbred lines of divergent nature. The results are explained for different

plant parameters according to the following analysis procedure for three parameter and six

parameter models.


111

As explained in results that six parameter model was adequate to explain the inheritance

pattern of days to 50% tasseling, showing that the trait is not only controlled by additive and

dominance gene actions but also some contribution from the epistasis as well. Similar results of

epistasis involvement in days to tasseling were also observed by Dawod et al. (2012) and

Hemalatha et al. (2014), who revealed that inheritance of tasseling in maize was controlled by

simple as well as complex gene actions. This indicates that improvement of studied trait will be

more difficult as compared to more simple models (additive-dominance and digenic epistatic

model) of inheritance. Such pattern of gene action is least favorable from a breeder’s point of

view, suggesting that revised breeding strategy is needed due to complexity of gene effects

occurring in these generations (Kathiria and Sherma, 1996). The dominant gene action and

digenic non-allelic epistasis of additive × dominance were found to be involved in governing the

inheritance of days to tasseling in all crosses except, PS-2 × BD-1, having adequacy of three

parameter model only. Dominant values in these three crosses were negative in nature but higher

in magnitude than additive. This shows that dominant genes have a pre-dominant role in the

inheritance so selection should be delayed to the later generations till the dominant gene effect is

diminished. About the dominance gene involvement, our results are in line with Saleem et al.

(2002) and Kumar et al. (2005) who also stated that for days to tasselling in maize, dominance

(incomplete to over dominance) effects played major role in its inheritance. Similarly

complementary type of non-allelic interaction was observed for cross PS-1 × BD-2. The digenic

non-allelic epistasis of additive × dominance was considered the major contributor in the

inheritance of this trait. In both crosses i.e. PS-1 × BD-2 and PS-2 × BD-2, additive gene action

with negative magnitude was found responsible for controlling days to tasseling. Presence of

additive gene action with negative pattern for days to tasseling in maize exhibited that this trait

can be fixed through selection in early generations producing an F1 hybrids with reduced days to

tasseling if dominance is of least value. Similar results of fixable gene action for tasseling were

also reported by Prakash and Ganguli (2004) and Atanaw et al. (2006), who revealed that

additive type of gene action was involved in the control of days to tasseling in their maize

germplasm. Moradi (2014) also reported similar results of both additive and dominance gene

actions for controlling the inheritance of days to tasseling in maize.

5.1.2 Days to 50 % anthesis

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A greater genetic diversity in the parents involved in the studied crosses was inferred

from 2 estimates. It is revealed that six model of complex inheritance was adequate to explain

the inheritance pattern of days to 50% anthesis rather than simple additive-dominance model.

Negative and significant magnitude of both additive and dominance gene actions in cross PS-1 ×

BD-1 was indicative of these type of gene actions in the inheritance of days to anthesis. The role

of dominance was pre-dominant due to its higher value than additive, showing that selection

should be delayed to later generations. Similarly in the same cross additive × additive and

dominance × dominance digenic non-allelic interactions were important in governing the

inheritance of days to anthesis. Azizi et al. (2006) also reported negative and significant effect of

dominance gene action for days to anthesis in cross B73 x Mo17. Presence of both dominance

and additive × additive epistasis will be helpful in promoting earliness in this material. Dorri et

al. (2014) reported a major role of dominant genes in the inheritance of days to anthesis. Similar

results of gene action for days to 50 % anthesis were also observed by Sujiprihati et al. (2003)

and Singh and Roy (2007), who reported that non-additive epistasis was among the most

important gene action for days to mid anthesis in maize. The presence of opposite and significant

signs of h (dominance) and l (dominance × dominance) resulted in duplicate type of non-allelic

interaction for the days to 50% anthesis in cross PS-1 × BD-1, while h and l with similar and

significant signs resulted in complementary duplicate type of non-allelic interaction in cross PS-1

× BD-2. From the presence of opposite signs of h and l, it is concluded that no complementary

type of interaction was present in the genetic control of this trait. The digenic non-allelic

epistasis of dominance × dominance was considered the major contributors in the inheritance of

this trait in these two crosses. In cross PS-2 × BD-2, additive gene action as well as additive ×

dominance and dominance × dominance type of non-allelic gene action with negative magnitude

were found responsible for controlling the inheritance of anthesis. Mhike et al. (2011) also

observed a predominant role of non-additive genes for days to anthesis in their study. Similarly

in cross PS-2 × BD-1, this trait was controlled by dominance gene action with additive x

dominant type of non-allelic interaction. This shows that with greater magnitude of dominant

genes selection needs to be delayed till later generations. In the same cross significance of j

(additive x dominance) exhibited that improvement for this trait is not expected through selfing,

because among the digenic interactions, additive × additive type is more fixable and more useful

for plant breeders (Farshadfar et al., 2001; Sharifi, 2005). Negative and significant values of h

113

(dominance) showed a major role of dominant gene action in the inheritance of this trait in all the

crosses except, PS-2 × BD-2.

5.1.3 Days to 50 % silking

As revealed from the best fit model, both additive and non-additive gene actions were

responsible for controlling the inheritance of days to 50% silking in all crosses, except, PS-2 ×

BD-1. This shows that inheritance of silking can be explained only by simple additive-

dominance model in cross PS-2 × BD-1. Our findings are in consonance with Ishfaq (2011),

based on generation mean analysis results for reproductive and yield characters in maize.

Although both additive and dominance gene action were found significant in cross PS-1 × BD-1

but the magnitude of dominance was higher than additive genes, showing that trait can be

exploited for hybrid production effectively. Dominance nature of inheritance for days to silking

have been reported by some earlier breeders like Saleem et al. (2002) and Kumar et al. (2005).

Haq et al. (2010) also revealed both additive and non-additive gene actions for days to silking,

while studying gene action of different quantitative traits in maize. In non-allelic, duplicate type

of gene action was observed in cross PS-1 × BD-1. Duplicate type of epistasis generally delay

the improvement through selection and hence, a higher magnitude of h (dominance) and l

(dominance × dominance) type of interaction effects would not be expected (Sabolu et al., 2014).

Since none of signs of (h) were similar to the (l) type of epistasis, it could be envisaged that no

complementary type of interaction was present in the genetic control of the studied traits. It also

indicated that selection should be delayed to latter generations of until a reasonable level of gene

fixation is attained. Significant value of d (additive), h (dominance), i (additive × additive) and l

(dominance × dominance) in the cross PS-1 × BD-1 exhibited the involvement of both heritable

and non-heritable gene actions. Complementary duplicate type of non-allelic interaction with

both additive and dominance gene actions was found to be responsible for controlling days to

50% silking in cross PS-1 × BD-2. In cross PS-2 × BD-2 along with dispersed type of digenic

interaction, additive and dominant type of gene actions were predominant in the inheritance of

days to silking. Shahrokhi et al. (2013) observed that epistasis plays a considerable role in the

inheritance of days to anthesis in maize. Such type of gene actions combined with some

dominance can be effectively utilized in hybrid breeding.

114

5.1.4 Plant height

In all crosses six parameter model of complex genetics was sufficient to explain the

genetic constitution of plant height, which disclosed the involvement of both allelic and non-

allelic gene actions for this trait. A duplicate type of non-allelic interaction in crosses PS-1 ×

BD-2 and PS-2 × BD-2 was found controlling the genetic control of plant height, suggesting that

it will increase the variation between generations and in the segregating populations. Presence of

duplicate type non-allelic gene action represents that selection intensity makes progress from

earlier to late generations. In such situation it is advisable to use breeding methods that deal

effectively with non-allelic interactions. In this regard genetic improvement could be achieved

through restricted recurrent selection of intermating among desirable segregates, followed by

selection or diallel selective mating or multiple crosses or biparental mating in early segregating

generations. Positive value of d (additive) and h (dominance) along with, additive × additive

gene effects in most of the crosses indicated predominant role of dominant gene action in the

inheritance of plant height. Our results match with some of the findings in literature including

those of Singh and Roy (2007), Iqbal et al. (2010) and Zare et al. (2011) who also reported

additive and additive × additive effects for plant height. Presence of additive genes explain that

selection based on this trait can be fixed easily in coming generation, similarly existence of

dominance genetic effects will be helpful in hybrid breeding program. These findings are in line

with Hallauer and Miranda (1988), Kumar et al. (2005). Likewise, a complementary type of non-

allelic gene action was involved in cross PS-1 × BD-1 with significant and similar sign of h

(dominance) and l (dominance × dominance) for plant height. Moreover, in non-allelic gene

actions, presence of i (additive × additive), j (additive × dominance) and l (dominance ×

dominance) with both positively significant and negatively significant magnitude indicating that

all the three types of digenic non-allelic interactions played a leading role in the inheritance of

this parameter. Mousa (2004), Leon et al. (2005) and Iqbal et al. (2010) also detected similar

results of non-additive nature of plant height while studying inheritance of maize germplasm

through generation mean analysis.

5.1.5 Ear height

Like other important traits ear height has been reported to be one of the most important

selection criteria in most breeding programs especially the root and stock lodging (Esechie et al.,

115

2004; Olawuyi et al., 2013). For yield purpose, high ear position could be susceptible to both

root and stock lodging, therefore selection for lower ear position is preferred in maize (Salami et

al., 2007).Both fixable and non-fixable gene actions were found to be responsible for controlling

the inheritance of ear height in all the crosses. This presence of epistasis is an indicative of great

genetic diversity among the parents for ear height while, the additive and dominance effects

reflects that selection in this material will be effective as well as it can be used in hybrid

programs. Similar findings regarding the predominant role of non-additive genetic effects were

also reported by Rezaei and Roohi (2004) and Alam et al. (2008) for ear height. In contrast to our

findings Zare et al. (2011) and Wannows et al. (2015) reported that only additive and dominance

genes were controlling inheritance for ear height. It can be concluded from significant values of

h (dominance) and l (dominance × dominance) with similar signs that digenic non-allelic

interaction of complementary type explained the inheritance of this trait in two crosses of PS-2 ×

BD-1 and PS-2 × BD-2. The presence of positive and significant values of d (additive) and h

(dominance) in these two crosses, disclosed the involvement of both additive and dominant gene

actions in the inheritance of ear height. Similarly in PS-1 × BD-1 and PS-1 × BD-2 dominance

and duplicate type of non-allelic gene action were found responsible in controlling inheritance of

ear height. It means that improvement will be low through selection because a higher magnitude

would not be expected for dominance (h) as well as dominance × dominance (l). Our results of

duplicate type non-allelic gene action are in line with Ishfaq (2011) and Wannows et al. (2015)

studies of determining genetic effects for some quantitative traits in maize. The significant

magnitudes of i (additive x additive), j (additive x dominance) and l (dominance × dominance) in

all crosses except PS-2 × BD-1 and PS-2 × BD-2 indicated that digenic non-allelic interactions

also play governing role in the inheritance of this trait.

5.1.6 Ear weight

Both additive and dominance effects were found prominent in controlling inheritance of

ear weight. The role of dominance was more comparing to additive gene actions in all the

crosses. Similarly, in digenic effects additive × additive was more predominant. This shows that

effective role of both additive (d) and additive × additive (i) can be successfully utilized for the

improvement of ear weight through selection. Ojo et al. (2006) also reported similar results of

additive effects for ear weight in their study. Likewise in crosses where dominance and dominance ×

116

dominance genetic effects are prevailing, could be utilized in hybrid programs efficiently.

Mendes-Moreira et al. (2015) also reported the prevalence of digenic effects in the inheritance of

ear weight at harvest in the QTL analysis of PB260 × PB266 progeny. A dispersed type of non-

allelic gene action was observed in cross PS-1 × BD-1 with non-significant effects of both

additive and dominance gene actions. In cross PS-1 × BD-2, negative and positive significant

nature of additive and dominance gene actions as well as duplicate type of non-allelic gene

actions were found in the inheritance of ear weight. Similarly in cross PS-2 × BD-1 and PS-2 ×

BD-2, additive and dominance gene action with positive magnitudes, and complementary non-

allelic interactions were preponderant for the inheritance of ear weight. Similar findings

regarding the presence of non-additive effects for ear weight in maize were also reported by

Sujiprihati et al. (2003).

5.1.7 Grain yield

The presence of both additive and non-additive gene effects revealed the complex genetic

nature of grain yield. Along with additive and dominance gene actions, all types of epistasis were

also observed, showing presence of greater genetic diversity among the parents involved in the

crosses. Presence of such genetic diversity is of prime importance for traits like yield and it must

be exploited by plant breeders to achieve their goals (Idahosa et al., 2010). According to Iqbal et

al. (2009) selection of desirable parents and information about the nature and magnitude of gene

action for a quantitative trait is of paramount importance for a plant breeder. In all crosses due to

higher magnitude, dominant genes were having predominant effects for grain yield, whereas,

additive gene action and additive × additive type of epistasis, was also found having its

proportion in the inheritance of this trait. Due to fixable nature of selection from additive effects,

gain from selection could be possible for grain yield. Wannows et al. (2010) also observed

similar results of additive effects for grain yield while studying genetic variability through path

coefficient analysis in maize. Our results corroborates the findings of Ojo et al. (2007), Musila et

al. (2010) and Ofori et al. (2015) who also observed additive gene action for grain yield in maize

and proposed that simple selection would be effective to make desirable improvement in the

studied genotypes for grain yield. Similarly due to predominance of additive gene to non-

additive gene, Mhike et al. (2011) hinted the possibility of exploring early testing of genotypes.

Crosses dominant nature of inheritance, could be judiciously utilized for hybrid development in

117

maize breeding programs. Kanagarasu et al. (2010) reported that dominance effects were

controlling inheritance of grain yield. The predominant nature of non-additive gene effects in the

inheritance of grain yield were also reported by previous reviewers like, Mhike et al. (2011),

Abuali et al. (2012) and Dawod et al. (2012). Similarly Khalil et al. (2010) also observed that

along with non-additive effects additive gene action was responsible in controlling the

inheritance of grain yield.


High grain yield and early maturity are two important parameters for efficient and

economically viable maize hybrids. Both allelic and non-allelic interactions were found involved

in the inheritance days to maturity in all crosses as 2 values obtained were significant. It is

obvious that both heritable and non-heritable gene action were responsible in the control of this

trait. Both additive and dominant gene action were negatively significant in all crosses except,

PS-2 × BD-1 in which said effect was non-significant. Negative sign of both additive and

dominant genetic effects indicated that maturity will be earlier if selection is made for it.

Dominant gene effects in all crosses were negative and higher in magnitude than the additive one

which reveal that these parents can be efficiently utilized in hybrid breeding programs aiming at

reduced maturity. In maize crop with excessive water requirements at critical stages, earliness in

maturity offers opportunity to utilize cropping season where the short rainy period can be

efficiently used for maize cultivation (Ofori et al., 2015). Similar results of negative but

significant additive genetic effects were also obtained by Sofi et al. (2006), Singh and Roy

(2007), Shahrokhi et al. (2013), Hemalatha et al. (2014) and Ahamed et al. (2015). Presence of

additive genes explain that selection based on early maturity can be realized easily in coming

generation. Similarly existence of dominance genetic effects will also be helpful in hybrid

breeding program. Our findings of negative dominance effects for days to maturity are in

concord with that of Ishfaq (2011) and Shahrokhi et al. (2013). Dispersed types of non-allelic

interactions were observed in all four crosses. In epistatic effects, additive × additive and

additive x dominant effects were significant with negative and positive in two of the four crosses,

respectively. Presence of non-allelic interaction is an indication of greater genetic diversity in the

parental lines and also have a role in the inheritance of this trait. Therefore, methods which

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exploits non-additive gene effects and take care of non-allelic interactions like restricted

recurrent selection would be promising for improvement of maturity in this germplasm. Our

results of di-genic interactions are in line with that obtained by Ishfaq (2011) and Shahrokhi et

al. (2013).

5.1.9 Ear length

Being an important yield component, ear length was revealed to be controlled by a

combination of additive and non-additive gene actions. In all crosses, dominant gene effects

were positive and predominant over other allelic and non-allelic interactions. Based on

prominent dominant gene action, ear length could be considered as important character in the

selection of inbred lines for development of maize hybrids. Similar results of dominant genetic

effects have been reported by Hallauer and Miranda (1988), Dorri et al. (2014) and Wannows et

al. (2015). Like dominant genes, additive gene action also exerted a role in the inheritance of ear

length in two of the four crosses which is an indication of improvement for this trait. Our results

of additive effects for ear length are in conformity with Zare et al (2011), Chandal & Mankotia

(2014) and Alamerew & Warsi (2015). Non-allelic interaction of dominance × dominance was

higher in magnitude with negative nature than other epistatic interactions. Similarly additive ×

additive interactions were positively significant in three crosses, which resulted in a duplicate

type of non-allelic interaction in two crosses. Similar results of greater genetic diversity in maize

inbred lines for ear length have also been reviewed by Ali et al. (2007) and Singh and Roy

(2007) and Wannows et al. (2015).

5.1.10 Ear diameter

Generation mean analysis of ear diameter revealed that both additive and non-additive

gene actions were involved in the inheritance of this trait. This indicates that both selection of

inbred lines in early generations and their exploitation in hybrid breeding program will lead to

the production of useful hybrids. Additive effects observed in all the crosses were positively

significant except, PS-1 × BD-1. This indicates that selection based on ear diameter will be

effective in early generations. Our results are corroborated by Singhal et al. (2006), Kumar et al.

(2011), Haddadi et al. (2012) and Nataraj et al. (2014). Muraya et al. (2006) also suggested the

existence of both additive and non-additive gene action for ear diameter. Positively significant

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and predominant nature of dominant gene actions observed in all crosses can be effectively

utilized in hybrid breeding programs. Zivanovic et al. (2010) also reported involvement of

dominant genes in the inheritance of ear diameter. Epistatic interactions including additive ×

additive and additive x dominant were found to have a significant role in the control of ear

diameter, while dominance × dominance epistatic interactions were negative and non-significant

in all crosses. A dispersed duplicate type of non-allelic interaction was observed in all four

crosses. Similar findings of non-allelic interactions for ear diameter were also confirmed by

Sujiprihati et al. (2003), Kumar et al. (2006), Ali et al. (2007) and Singh and Roy (2007).


As reported in results that along with additive and dominant gene action, epistatic

interaction, additive x additive, additive × dominanceand dominance × dominance were found to

have major contribution in the inheritance of kernel rows per ear. Similar results of equal

involvement of additive and dominant genes in the inheritance of kernel rows per ear have been

reported by Hallauer and Miranda (1988). Other researchers like Mousa (2004), Prakash and

Ganguli (2004), Bujak (2006) and Srdic et al. (2007), Nataraj et al. (2014) also suggested

exploitation of additive genes for improvement of kernel rows per ear. The contribution of

dominant genes was higher than additive and epistatic genes which indicate that kernel rows per

ear could be efficiently utilized in hybrids development. In literature similar results can be

viewed from Saleem et al. (2002), Kumar et al. (2005), Shahrokhi et al. (2013) and Ofori et al.

(2015). Dominance and additive × additive effects were found positive and significant in two of

the four crosses which represent that they could be handled in hybrid programs. Significant

presence of dominance and dominance × dominance epistatic interaction with opposite signs

exhibited involvement of duplicate type of digenic interactions in the inheritance of kernel rows

per ear. Such results of duplicate genes will slower improvement through selection for kernel

rows per ear. Our results of non-allelic interactions are were in agreement with that reported by

Saeed et al. (2000), Vidal-Martinez et al. (2001), Sujiprihati et al. (2003), Kumar et al. (2006),

Srdic et al. (2007) and Singh & Roy (2007) in their maize populations.

5.1.12 Grains row-1

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Generation mean analysis revealed that grains per row was not only controlled by

additive and dominance gene actions but had some contribution from the non-allelic interactions

as well. Similar results of both additive and dominance effects for grains per row were also

observed by Rezaei and Roohi (2004), Zare et al. (2011) and Wannow et al. (2015), who

revealed that inheritance of grains per row was controlled by simple as well as complex gene

actions. This indicates that improvement of this trait will be more difficult as compared to those

controlled by simple genetic model of inheritance. Such situation of inheritance is least favorable

from a breeder’s point of view, and suggests a revised breeding strategy for such traits of

complex genetic inheritance (Kathiria and Sherma, 1996 and Hussain et al., 2014). Presence of

additive and dominant gene actions for grains per row demonstrated that this trait can be fixed

through selection of inbred lines in early generations producing F1 hybrids having more number

of grains per row. Our results of additive gene involvement are in line with Perez-Velasquez et

al. (1996), Wasif (2008), Zivanovic et al., (2010), Ahamed et al. (2015). The dominance gene

action and digenic non-allelic epistasis of additive × dominance were found to be involved in

governing the inheritance of grains per row. Dominant effects were higher in magnitude than

additive effects. This represent that dominant genes has a pre-dominant role in the inheritance so

selection should be delayed to the later generations till the dominant gene effect is diminished to

considerable extent. Similarly, inbred lines with prominent dominant genes could be efficiently

used in hybrid development. Our results of dominant nature of genes for grains per row are in

line with Saeed et al. (2000), Malik et al. (2004), Srdic et al. (2007), Dawod et al. (2012),

Abualiet al. (2012), who suggested that dominant (incomplete to over-dominance) effects played

major role in its inheritance. Both complementary and duplicate type of non-allelic interactions

were observed for grains per row. Equal importance of additive and epistatic genetic effects for

grains per row was also reported by Debnath et al. (1989), Hamid et al. (1995), Kumar et al.

(1998), Wannow et al. (2015) and Ofori et al. (2015). Beside the additive and dominance genetic

effects, non-allelic interactions also contributed significantly to genetic variations for grains per

row. In such situations when additive, dominance and epistatic interactions are operating, an

appropriate breeding method should be adopted that can effectively exploit these three types of

gene effects simultaneously.

5.1.13 Grains ear-1

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Genetic variability observed through generation mean analysis exhibited that not only

additive and dominant genetic effects but also non-allelic interactions were found responsible in

the inheritance of grains per ear. Presence of dominance genes exhibited that the trait could be

efficiently utilized in hybrid breeding programs for high grain yield, while the additive nature of

trait represent a potential for improvement of grains per ear. Our results about dominantly

control of grains per ear are in similarity with that reported by Darrah and Hallauer (1972),

Khodarahmpour et al. (2011a) and Nzuve (2014). A prevalence of duplicate type non-allelic

interactions in the inheritance control of grains per ear suggest that variation between generations

and in the segregation populations would be increased. Presence of duplicate type non-allelic

gene action represents that selection intensity makes progress from earlier to late generations. In

such situation it is advisable to use breeding methods that deal effectively with non-allelic

interactions. In this regard genetic improvement could be achieved through restricted recurrent

selection of intermating among desirable segregates, followed by selection or diallel selective

mating or multiple crosses or biparental mating in early segregating generations. Likewise, a

complementary type of non-allelic gene action was involved with significant and similar sign of

h (dominance) and l (dominance × dominance) for grains per ear. Moreover, in non-allelic gene

actions presence of i (additive x additive), j (additive × dominance) and l (dominance ×

dominance) with both positive significant and negative significant magnitude indicated that all

the three types of digenic non-allelic interactions played a leading role in the inheritance of this

parameter. Azizi et al. (2006) and Haq et al. (2010) also detected similar results of non-additive

nature of grains per ear while, studying inheritance of various parameters in maize germplasm

through generation mean analysis. The results of additive and non-additive genetic effects

observed in this study are in agreement with Bujak et al. (2006), Ali et al. (2007), Alam et al.

(2008), Khodarahmpour et al. (2011b) and Aslam et al. (2015) who also reported similar genetic

effects responsible in controlling the inheritance of number of grains per ear in maize.


Generation mean analysis revealed that both additive and non-additive genes were

involved in the inheritance of hundred grain weight in three of the four crosses while, in a single

cross simple additive dominant model of inheritance was operative. Among the non-allelic

interactions a complementary type of epistasis was also observed in which both dominant and

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dominant × dominant gene action were positively significant. Presence of significant additive

effects with negative magnitude indicate that selection in early generations will reduce grain

weight, while with positive magnitude selection would be efficient for increased grain weight.

Similar results for significant contribution of additive genes to the inheritance of hundred grain

weight are in line with Chen et al. (1996), Mahmood et al. (2004), Amer (2004), Sofi et al.

(2006) and Aslam et al. (2015). Hence, dominance effects of hundred grain weight could be

utilized in hybrid development. Non-allelic interactions present in the studied material exhibited

considerable amount of genetic diversity in the parents. Non-additive epistatic interactions were

positive and prominent over the additive epistasis. Same results of predominant effects from

dominant genes for hundred grain weight were also reported by Azizi et al. (2006), Akbar et al.

(2008), Fan et al. (2009), Khodarahmpour (2011b), Hussain et al. (2014) and Dorri et al. (2014)

while, evaluating their maize germplasm under desired objectives. Alamerw and Warsi (2015)

reported both positive and negative effects of dominant genes for hundred kernel weight in their

experiment of combining ability of yield related traits in maize. Mousa (2004), Prakash and

Ganguli (2004), Azizi et al. (2006) and Ali et al. (2007) also reported some contribution of non-

allelic interactions for hundred grain weight in their experiments.


As an important contributor to economic yield, biological yield is of great importance for

plant breeders aiming at high grain yield. Biological yield represents weight of net

photosynthates and in maize, it includes both the cob and stover weights. Both additive and

dominant genes as well as epistatic interactions were found operative in the inheritance of

biological yield. As indicated the effect of dominant genes was higher to that of additive,

representing predominant role in biological yield. Similar results of inheritance control through

additive gene action were also reported by Jatav et al. (2014) for biological yield in wheat crop.

The dominant genetic effects could be successfully exploited for biological yield in hybrids

development. Similarly the positive natured additive effects could be significantly utilized in the

development of synthetic varieties following an effective selection in early generations.

Dominance effects for biological yield in wheat were also observed by Kumar et al. (2011), Jain

and Sastry (2012) and Jaiswal et al. (2013). The genetic diversity in the parental populations

revealed through non-allelic interactions could also be used in the synthetic variety development

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if epistasis is of fixable type, otherwise it could be utilized in hybrid breeding programs for

increased biological yield. One of the previous researcher, Mehla et al. (2000) has also

experienced the involvement of epistasis in the inheritance of biological yield.


A complex genetic nature of harvest index was obvious through generation mean

analysis. Although additive and dominant gene effects as well as non-allelic interactions were

involved in controlling harvest index but dominant genes were prominent. Non-allelic

interactions are indicative of greater genetic diversity in the parental material. The desired

additive effects could be efficiently utilized in selection of superior parents for obtaining a

significant gain from selection. Moradi (2014) reported both additive and dominant effects for

harvest index while, determining genetic variances and heritability estimates in maize. Seboka et

al. (2009), Saeed et al. (2010) and Singh et al. (2013) also reported that harvest index was

controlled by both additive and non-additive effects in wheat. The dominant genetic effects of

positive magnitude need to be exploited in hybrid development programs for high grain yield.

Our results of dominant inheritance of harvest index are confirmed by Jain and Sastry (2012) in

wheat crop. The non-allelic interaction dominance × dominance and dominant genetic effects

were significant with similar signs which disclosed the complimentary type of gene action.

Similarly significant and opposite signs of these components indicated duplicate gene action.

The crosses having complimentary type of epistasis could be exploited through heterosis

breeding for harvest index, while in duplicate epistasis bi-parental meeting and recurrent

selection would be most beneficial. Similar results of additive, dominance and epistatic effects

were also reported by Mahdy (1988), Pandey et al. (1999) and Shekhawat et al. (2000) for

harvest index in wheat.


The most important contributor to the inheritance of shelling percentage was dominant

gene action although some of the non-allelic interactions like additive × additive and dominance

× dominance also played their role. This indicates that these inbred parents could be effectively

exploited for superior hybrids. Similar results of non-additive effects for shelling percentage

were reported by Mathuret al. (1998), Sujiprihati et al. (2003), Sah et al. (2014) and Pérez-López

et al. (2014). Niyonzima et al. (2015) reported that inheritance of percent shelling was under

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control of additive, dominance and epistatic gene actions. In all crosses, additive × additive and

dominant × dominant non-allelic interactions were significantly positive and negative,

respectively. Such occurrence of non-allelic interactions represented duplicate type of digenic

interactions which is an indication of greater genetic diversity. The fixable heritable epistasis

could be effectively used in the selection of superior inbred lines. Our results of duplicate

epistasis for shelling percentage in maize are corroborated by previous researchers like Ravikant

et al. (2006). Similar results of epistatic effects for percent shelling were also reported by

Niyonzima et al. (2015) in their maize populations.


High grain yield and popping expansion are the two importance strategies in hybrid

development programs of popcorn. Expansion volume is a quality trait of great importance to

consumers, as unpopped kernels are sold by weight and popcorn flakes are sold by volume

(Shimoni et al., 2002; Borras, 2006). All the three type of gene actions including additive,

dominance and epistasis were found responsible in the inheritance of expansion volume of maize

grain. This indicated that the trait was under a complex genetic mechanism. The additive portion

of genetic control was comparatively low than that of dominance one, indicating its

predominance. Such dominant genes could be effectively utilized in hybrid breeding. On the

other hand, the additive portion need to be exploited in the selection of superior inbred parent as

it represents fixable variation. Pinto et al. (2001), Andrade et al. (2002), Rangel et al. (2008) and

Silva et al. (2010), Jele et al. (2014) and Cabrel et al. (2015) also reported similar results of both

additive and non-additive genetic effects for expansion volume with a high proportion from

additive genes. In non-allelic interactions, duplicate type of digenic inheritance was prominent.

Lu et al. (2003) and Pinto et al. (2004) also obtained additive component as controlling factor in

the inheritance of expansion volume, while studying the genetic mechanism and heritability of

grain yield and expansion volume in popcorn top crosses. Based on their studies previous

researchers like Pajic and Babic (1991), Pereira and Amaral (2001) and Miranda et al. (2008)

also emphasized on early generation selection of superior inbred lines for popping expansion

volume.

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Number of unpopped grains and grain moisture content at popping are the main

indicators for popcorn expansion. A desired popcorn variety should have a low number of non-

popping kernels and grain moisture content between 13 and 14.5 % at the time of popping

(Ziegler, 2001). Consumers prefer popping expansion and less number of unpopped grains in

soft popcorn (Aguiar et al., 2008, Rangel et al., 2008, Freitas Jr. et al., 2009 and Munhoz et al.,

2009). Both additive and dominant genes were found responsible in the genetic control of

percent unpopped grains with a greater contribution from dominant genes. In most of the crosses

the negatively significant values of dominant genetic effects represented that they will reduce the

number of unpopped grains. A similar trend of both additive and non-additive genetic effects

with a greater portion from additive effects was observed by Jele et al. (2014). The additive

genetic components of percent unpopped grains need to be used in the identification of parents

with reduced unpopped grains which could be exploited in hybrid breeding scheme for their

desired dominant gene. Among the epistatic interactions dominant × dominant gene action were

important revealing the importance of dominance gene to be utilized in hybrid development

effectively. Both complementary and duplicate type of digenic interactions were involved in the

inheritance of percent unpopped grains. Presence of duplicate type non-allelic gene action

represents that selection intensity makes progress from earlier to late generations. In such

situation it is advisable to use breeding methods that deal effectively with non-allelic

interactions. In this regard genetic improvement could be achieved through restricted recurrent

selection of intermating among desirable segregates, followed by selection or diallel selective

mating or multiple crosses or biparental mating in early segregating generations.

5.2 Heritability

Heritability estimates are of tremendous importance as they influence the choice of

procedures for selection of genotypes by plant breeders. Based on heritability, plant breeders

decide which method would be most effective to improve a character and to predict gain from

selection as well as determine the relative importance of genetic effects (Falconer and Mackay,

1997). The concept of heritability is important for breeders since it is an important factor in the

rate of genetic change possible in a trait (Wilcox, 1992). Selection of character with high

heritability results into a meaningful gain from selection. Selections for quantitative characters

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like grain yield in maize produce very little or no gain. The failure of yield response to selection

is most likely due to low heritability of this trait. Low heritability makes it very difficult to

identify the superior genotypes. Therefore, the superiority of plants selected on the basis of

phenotype would be due to factors other than their genotype. This would limit the progress under

selection. Heritability of a character provides reliable information about the inheritance of that

trait into the next generation, so helps in making desirable selection. The higher the heritability,

the simpler and less time consuming the selection procedure and the greater will be the genetic

improvement (Allard, 1960). Heritability in broad-sense (h2BS) is the ratio of total genetic

variance to the phenotypic variance, while the ratio of additive genetic variance to the

phenotypic variance is termed as narrow sense heritability usually denoted as h2NS (Sujiprihati et

al., 2003). Plant breeders can exploit the narrow sense heritability in an efficient way for

selection because of its additive genetic constitution (Falconer and Mackay, 1997). High estimate

of narrow sense heritability for a trait indicates that the character investigated is simply inherited,

while low estimate shows that the character is less heritable because high number of genes are

involved in the control of that character (Suzuki et al., 1981).Characters with high heritability

(narrow sense) can easily be fixed with simple selection resulting in quick progress, as they

would be under additive genetic effects. According to Fehr (1993) the presence of additive

genetic effects for a trait could be exploited in selection due to its fixable variation. Fry (2004)

reported that heritability of a trait approaches its maximum in successive generations following

hybridization. Heritability estimates of both types i.e., broad sense (h2BS) and narrow sense

(h2NS), are discussed here for the studies of plant parameters in four maize crosses to elucidate

the pattern of heritability and to compare the results obtained in the present study with those

reported by earlier researchers.


High heritability estimates of broad sense were observed for days to 50% tasseling in all

the four crosses, showing that selection in these crosses for this trait will be effective due to high

genetic variances. Our result of high broad sense heritability were in line with those observed by

Bello et al. (2012), Sharma et al. (2014), Moradi (2014) and Al-Falahy (2015) while, Abdelmula

and Sabeil (2007), Nigussie& Saleh (2007) and Bekele & Rao (2014) reported moderate

heritability of broad sense in their studies for days to tasseling in maize. Narrow sense

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heritability estimates ranged from moderate to high in all four studied crosses for days to

tasseling. This exhibit that parents could be easily utilized for both direct selection and hybrid

development. Similar results of low narrow sense heritability were also observed by Moradi

(2014), while Al-Falahy (2015) calculated moderate estimates for days to tasseling.


High estimates of broad sense heritability were calculated for days to anthesis in all four

crosses. On the other hand, moderate level of narrow sense heritability was estimated for days to

anthesis in three of the four crosses, while high level of narrow sense heritability was calculated

for only one cross. As moderate to high level of narrow sense heritability is indication of the

predominant role of additive gene action which means that these parents can be effectively

utilized for enhancing early maturity through selection. High heritability estimate is an indication

of relative small environmental effect on phenotype as well as a close resemblance between

genotype and the phenotype. High broad sense heritability was also estimated by Majidi et al.

(2009) and Shukla et al. (2014) for days to anthesis in maize. In contrast low broad sense

heritability estimates were observed by Bello et al. (2012), Bekele& Rao (2014) and Dorri et al.

(2014) for days to anthesis. Our results of high and low estimates of narrow sense heritability are

in line with Majidi et al. (2009) and Dorri et al. (2014), respectively.


Days to silking showed high broad sense heritability estimates in all the four crosses,

while narrow sense heritability ranged from moderate to high in these crosses for this maturity

character. Due to high estimates of heritability phenotype will be a clear picture of genotype and

hence selection will be more effective for earliness in silking. Earlier researchers like Beyene

(2005), Sumathi et al. (2005), Nigussie & Saleh (2005) and Bello et al. (2012) also observed high

broad sense heritability estimates for days to silking in their studies while estimating heritability

and other genetic parameters in maize. Moderate to high narrow sense heritability can easily be

utilized for promoting earliness in these germplasm. Our high heritability estimates for broad

sense and moderate for narrow sense are in conformity with those of Abadi et al. (2011).

5.2.4 Plant height

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Broad sense heritability estimates calculated for plant height in all four crosses were of

high magnitude, while narrow sense heritability estimated for plant height were of moderate

level. Estimates of both broad and narrow sense heritabilities indicated that plant height was least

affected by environment. This represent that selection in these genotypes for plant height would

be meaningful in further breeding approaches. Similar results of high heritability have been

reported by Mehmood et al. (2004), Sumathi et al., (2005), Tengan et al. (2012), Nataraj et al.

2014 and Shukla et al. (2014). Majidi et al. (2009) and Abadi et al. (2011) observed high

estimates for both broad and narrow sense heritability in their studies, while Tengan et al. (2012)

also reported low narrow sense heritability.

5.2.5 Ear height

Estimates of broad sense heritability were high for ear height in all the crosses, whereas

heritability estimates in narrow sense were also high in most crosses while, in one cross

moderate level of heritability (h2NS) was calculated. High levels of heritability shows that ear

height was least affected by environment, which provide the evidence that ear height was the

under control of additive genetic effects. Similarly crosses with moderate heritability estimates is

indicative of smaller environmental influence which suggests that improvement of this trait in

this material could be made easily through selection. The present results about high heritability

got support from Sumathi et al. (2005), Lorenzana and Bernardo (2008), Shukla et al. (2014), Al-

Falahy (2015). Abadi et al. (2011) also reported high estimates of both broad and narrow sense

heritability for ear height.

5.2.6 Ear weight

Broad sense heritability estimates observed for ear weight were high in magnitude in all

four crosses. High heritability is an indication of predominant role of genetic effects compared to

environmental one. Based on high role from genetic portion, improvement in ear weight and

ultimately grain yield could be made easily through selection. Heritability estimates of narrow

sense were of moderate level in all crosses. Similar results of high broad sense heritability were

also reported by El-Badawy (2012), Gnanamurthy et al. (2013) and Nzuve et al. (2014). In

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contrast Berilli et al. (2013) observed moderate broad sense heritability for ear weight. These

findings exhibit that additive gene action is responsible for controlling ear weight, which also

manifests that selection in early generations would be fruitful. Similar results of moderate

heritability in narrow sense have also been reported by Sujiprihati et al. (2003). Azizi et al.

(2006) and El-Badawy (2012) reported low and high estimates of narrow sense heritability for

ear weight in their study.

5.2.7 Grain yield

All the four crosses disclosed high estimates of heritability in broad sense for grain yield.

On other hand moderate heritability in narrow sense was estimated for three of the four crosses

while, only one cross exhibited high level of narrow sense heritability for grain yield. Such

presence of high heritability estimates evoke the existence of enough amount of

genetic variability for improvement of this trait and also indicates that

grain yield is more amenable to selection and could be improved easily. Similar

results of high heritability for grain yield were also reported by previous researchers like Ali et

al. (2012), Bello et al. (2012), El-Badawy (2012), Noor et al. (2013), Hussain and Hassan (2014),

Hussain and Ali (2014), Shukla et al. (2014), Al-Naggar et al. (2015) and Mukambi et al. (2015).

Our findings of heritability in narrow sense with moderate levels observed for most of the

crosses in this study are in consensus with those of Presterl et al. (2003), Abdelmullah and Sabiel

(2007), Majidi et al. (2009), El-Badawy (2012) and Hussain and Ali (2014). Azizi et al (2006)

also reported narrow sense heritability of low to moderate level in a study of gene action for two

crosses. Dorri et al. (2014) also reported high narrow sense heritability for grain yield.

Inconsistently low estimates of narrow sense heritability were reported by some early researchers

like Lorenzana& Bernardo (2008), Zare et al. (2011), Hussain et al. (2014) and Al-Naggar et al.

(2015).

5.2.8 Ear diameter

High broad sense heritability estimates calculated for ear diameter projects low

environmental influence with high genetic effects on this trait. On the other hand narrow sense

heritabilities were of moderate to high level. As moderate to high level of narrow sense

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heritability is indication of predominant role of additive gene action which means that these

parents can be effectively utilized in recurrent selection programs for enhancing ear diameter.

Moderate level of narrow sense heritability is also an indication of influence of both genetic and

environmental factor on ear diameter. High heritability estimate is an indication of relative small

environmental effect on phenotype as well as a close resemblance between genotype and the

phenotype. Similar results of high broad sense and moderate narrow sense heritability were also

reported by Nigussie and Saleh (2007), Rafiq et al. (2010), Kashiani et al. (2010), Shukla et al.

(2014) and Sharma et al. (2014). Low narrow sense heritability estimates were reported by

Tengan et al. (2012) for ear diameter.

5.2.9 Ear length

Broad sense heritability estimates calculated for ear length were representing greater

portion of genetic components including both additive and non-additive. Such genetic effects

could be utilized in hybrid development if the gene actions are non-additive in nature otherwise,

effectively exploited in the selection of superior inbred parents for future breeding programs.

Estimates of narrow sense heritability were moderate in magnitude exhibiting that both genetic

and environmental factors are affecting ear length. Similar results of heritability estimates have

been reported by Nigussie and Saleh (2007), Rafiq et al. (2010), Kashiani et al. (2010), Sharma

et al. (2014) and Ishaq et al. (2014). In contrast to our findings Idris and Abuali (2011) and

Shukla et al. (2014) revealed moderate broad sense heritability estimates for ear length. Similarly

low narrow heritability estimates have been reported by Tengan et al. (2012) for ear length.


Broad sense heritability estimates observed for kernel rows per ear were high in

magnitude in all four crosses. High heritability is an indication of predominant role of genetic

effects compared to environmental one. Based on high role from genetic portion improvement in

kernel rows per ear could be made easily through selection as well as using desired selected

parents in hybrid breeding programs. Heritability estimates of narrow sense varied from

moderate to high level for this trait. Similar results of high broad sense heritability were also

reported by Alake et al. (2008), Tengan et al. (2012) and Nataraj et al. (2014) while, Noor et al.

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(2013) revealed moderate estimates of broad sense heritability. Olakojo and Olaoye (2011),

Shahrokhi et al. (2013) and Shukla et al. (2014) calculated low broad sense heritability estimates

for kernel rows per ear while, evaluating their maize germplasm. Nigussie and Saleh (2007)

reported negative heritability for kernel rows per ear, indicating very low contribution of genetic

effects. Our findings of moderate narrow sense heritability estimates for kernel rows per ear were

in conformity to those of Moradi (2014). Our results of moderate to high narrow sense

heritability were contrary to Amer et al. (2004) and Tengan et al. (2012) who reported low

positive and high negative estimates for kernel rows per ear, respectively. Similarly Shahrokhi et

al. (2013) also observed low narrow sense heritability for kernel rows per ear.

5.2.11 Grains row-1

All the crosses exhibited high estimates of heritability in broad sense for grains per row.

Likewise moderate heritability in narrow sense was estimated for three of the four crosses while,

only one cross exhibited low level of narrow sense heritability for this trait. Such presence of

high heritability estimates evoke the existence of enough amount of genetic variability for

improvement of this trait and also indicates that grains per row is more amenable to selection and

could be improved easily. Similar results of high heritability for grains per row were in

consensus to that reported by previous researchers like Moradi (2014, Aslam et al. (2015) and

Wannows et al. (2015). Shahrokhi et al. (2013) and Dorri et al. (2014) reported moderate broad

sense heritability estimates in their experiments on maize crop. Our findings of heritability in

narrow sense with moderate levels observed for most of the crosses in this study were in

consensus with those of Moradi (2014), Aslam et al. (2015) and Wannows et al. (2015).

Inconsistently low estimates of narrow sense heritability for grains per row were reported by

some early researchers like Shahrokhi et al. (2013), Hussain and Ali (2014) and Dorri et al.

(2014).

5.2.12 Grains ear-1

Like other grain characters high broad sense heritability estimates were calculated for

grains per ear. Moderate heritability in narrow sense was estimated for two of the four crosses

while, other two crosses exhibited low and high estimates of narrow sense heritability for this

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trait. Presence of such high heritability estimates indicated sufficient amount of genetic

variability for improvement of grains per ear and also revealed that grains per ear was more

accessible to selection and could be improved easily. Our reports of high broad sense heritability

are corroborated with Bello et al. (2012), Anshuman et al. (2013), Rezaei et al. (2005), Aslam et

al. (2015) and Rahman et al. (2015). Khodarahmpour (2011a) reported moderate heritability

estimates for grains per ear. Our findings of heritability in narrow sense with moderate levels

observed for most of the crosses in this study were in consensus with those of Moradi (2014) and

Aslam et al. (2015). Rezaei et al. (2005) and Khodarahmpour (2011b) reported low estimates of

narrow sense heritability contradicted our reported results.


Hundred grain weight showed high broad sense heritability estimates in all four crosses,

while narrow sense heritability ranged from moderate to high for this trait. Due to high estimates

of heritability phenotype will be a clear picture of genotype and hence selection will be more

effective for hundred grain weight. Earlier researchers like Chohan et al. (2012), Moradi (2014),

Hussain et al. (2014) and Wannows et al. (2015) also experienced high broad sense heritability

estimates for hundred grain weight in their studies while estimating heritability and other genetic

parameters in maize crop. Moderate to high narrow sense heritability can easily be utilized for

improving hundred grain weight in their studied germplasm. Our results of high to moderate

heritability estimates of narrow sense are in conformity with Moradi (2014) and Wannows et al.

(2015). Hussain et al. (2014) calculated low narrow sense heritability estimates for hundred grain

weight both under normal and stressed conditions.


High broad sense heritability estimates calculated for percent shelling was a

manifestation that a greater portion of genetic components (additive and non-additive) were

affecting this trait. Such genetic effects could be utilized in hybrid development if the gene

actions are non-additive in nature otherwise, could be effectively exploited in the selection of

superior inbred parents for future breeding programs. Estimates of narrow sense heritability were

moderate in magnitude exhibiting that both genetic and environmental factors are affecting

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percent shelling. Our results of broad sense heritability estimates were in consensus with that

reported by Hussain et al. (2014) and Atta & Marsi (2015). In contrast to our findings, Idris &

Abuali (2011) and Shukla et al. (2014) revealed moderate broad sense heritability estimates for

ear length. Similarly moderate narrow heritability estimates for percent shelling were also

reported by Hussain et al. (2014).


Early and medium-maturing maize hybrids and open pollinated varieties are desirable in

the areas where early and cold autumn affect the production due to early autumn cold stress.

Heritability estimates of both broad and narrow sense for days to maturity were high in

magnitude indicating a predominant role of additive gene action which means that these parents

can be effectively utilized for enhancing early maturity through selection. High heritability

estimate is an indication of relatively small environmental effect on phenotype as well as a close

resemblance between genotype and the phenotype. Our results of high heritability estimates were

also in conformity with those of Dorri et al. (2014), Sharma et al. (2014) and Kumar et al.

(2014a) for days to maturity in maize. In contrast to our findings Khanmohammadi et al. (2013)

and Tesfaye et al. (2014) reported low broad sense heritability for days to maturity.


High broad sense heritability estimates were operative in all crosses of the present study

for biological yield. Narrow sense heritability was of moderate level in all crosses. Such presence

of high heritability estimates revealed the existence of enough amount of genetic variability for

improvement of this trait and also indicates that biological yield could be improved easily

through selection. A minimal difference in high magnitude of both broad and narrow sense

heritabilities, revealed predominancy of additive genetic effects over dominance genetic effects

for this trait. Our results of high broad sense heritability estimates similar to previous researchers

including, Aastiveit and Aastiveit (1990), Kanapeckas et al. (2005) and Majidi et al. (2009).

Abadi et al. (2011) reported moderate level of h2BS for biological yield. Our findings of moderate

narrow sense heritability are in consensus with those of Piano et al. (2008), Majidi et al. (2009)

and Abadi et al. (2011).

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High broad sense heritability estimates calculated for harvest index revealed low

environmental influence with high genetic effects on this trait. Heritability estimates of narrow

sense reported for harvest index were of moderate level, indicating a predominant role of

additive gene action which means that studied germplasm could be passed through recurrent

selection programs for enhancing harvest index. Moderate level of narrow sense heritability is

also an indication of influence of both genetic and environmental factors on this trait. Such

results of high heritability estimates are indication of relative small environmental effect on

phenotype as well as a close resemblance between genotype and the phenotype. Similar results

of high broad sense and moderate narrow sense heritability were in consensus with reports of

previous scientists including Chohan et al. (2012), Moradi (2014) and Moradi et al. (2014).


In popcorn breeding, not only yield and agronomic traits are important, but quality

characters like, popcorn texture and softness are also considered. Farmers are interested in high

yields and other features of normal maize, whereas consumers care about a high expansion

volume, which improves the popcorn texture and softness (Miranda et al., 2008). Broad sense

heritability estimates calculated for expansion volume were of high level in all crosses evaluated

in this study, while narrow sense heritability estimates were of moderate level. As moderate to

high level of narrow sense heritability is indication of predominant role of additive gene action

which means that these parents can be effectively utilized for enhancing early maturity through

selection. This is because there would be a close correspondence between the genotype and the

phenotype due to the relatively small contribution of the environment to the phenotype. Our high

broad sense heritability results were in consistency with that estimated by Ribeiro et al. (2012),

Freitas et al. (2014) and pinto et al. (2014) for expansion volume in maize. In contrast, low and

moderate broad sense heritability estimates for expansion volume were observed by Amaral Jr et

al. (2010) and Rodovalho et al. (2014), respectively. Our results of high and low estimates of

narrow sense heritability are also supported by Majidi et al. (2009) and Dorri et al. (2014),

respectively.

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Broad sense heritability estimates observed for percent unpopped grains were high in

magnitude in all crosses. High heritability is an indication of predominant role of genetic effects

compared to environmental one. Based on high role from genetic portion, improvement in

percent unpopped grains could be made easily through selection. Heritability estimates of narrow

sense were of moderate to high level. Similar results of high broad sense heritability were also

reported by Jele et al. (2014). These findings exhibit that additive gene action was responsible

for controlling percent unpopped grains, which also shows that selection in early generations

would be fruitful.

5.3 Heterosis

The phenomenon of heterosis or hybrid vigor has been extensively used in cross

pollinated crops like maize, where mating of two homozygous inbred lines results in an F1 hybrid

which is more productive than its parents. In these crops, heterosis is widely exploited as a basic

tool for improved production in the form of F1 hybrids. According to Valerio et al. (2009) using

best parent combination in hybrid program we can expect elite F1 hybrids. Superiority, of hybrids

over pure line mid-parents and better-parents is associated with manifestation of heterotic effects

of major yield traits (Alghamdi, 2009). Heterosis of both nature, mid-parent and better-parent is

an important parameter for plant breeders especially while dealing with cross pollinated crops

like maize. Generally, heterosis has been studied in populations with different genetic

backgrounds, which confound the relationships among heterosis, dominance and gene frequency.

It is the heterotic studies that provide a base for fully exploiting the valuable hybrid

combinations in breeding programs and their commercial utilization. Therefore, any breeding

material that lacks the sufficient amount of inbuilt hybrid vigor as a prerequisite can’t develop

successful hybrid varieties. It is due to heterotic studies that hybrid maize production has been

successfully used by growers around the world. Being a complex quantitative character grain

yield and its components were reported by previous research scientists to have a variable range

of heterotic values in various F1 maize populations. Both mid-parents and better parent heterotic

effects were investigated for 20 plant parameters in four maize crosses in the present study.

These results are discussed in the following paragraphs in light of observations of the previous

investigators.

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Heterotic study revealed that negative values were calculated for both mid parent and

better parent heterosis. Being an important trait of maturity such observed reduction in days to

tasseling is desirable for developing early maize hybrids. Negative heterosis in all the crosses

represents that parental lines used in the study could be effectively utilized in hybrid breeding

programs for development of hybrid with early maturity. Similar results of negative heterosis

were also reported by Aminu et al. (2014), Kumar et al. (2014c), Solalinde et al (2014) and Al-

Falahy (2015) for days to tasseling in their used maize germplasm.


All the crosses studied revealed negative magnitude of both mid and better parent

heterosis for days to 50% anthesis. Negative nature of both mid and better parent heterosis for

day to anthesis exhibited that in all the crosses maturity has been decreased which is a prime

objective in areas where maize crop has short growing season with multiple cropping system.

Such negative heterosis along with dominance genetic effects of this germplasm could be

successfully exploited for hybrid development with early maturity. Similar findings of negative

heterosis for days to anthesis has been reported by Malik et al. (2004), Ali et al. (2013) and

Solalinde et al (2014).


Like other maturity characters mid parent and better parent heterosis for days to silking

were negative in nature in all crosses. Negative values of heterosis in all the crosses represent a

decline in the total days to silking and hence early maturity. It is obvious from such negative

heterosis in days to silking that these inbred lines can be significantly used in formation of early

maturing hybrids in future maize breeding programs. Our results of negative heterosis for days to

silking were in consensus to the findings of some earliest researchers including Iqbal et al.

(2010), Ali et al. (2013), Hussain and Ali (2014) and Al-Falahy (2015).

5.3.4 Plant height

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Both mid parent and better parent heterosis observed for plant height in the studied

crosses were positive in nature ranging from low to moderate in magnitude. This represents that

dominant and dominant × dominant gene action are involved in the inheritance of plant height.

Due to dominant control of the trait these parental lines could be effectively utilized in maize

hybrid breeding programs for short stature hybrids. Our findings of positive heterosis for plant

height are in conformity with Iqbal et al. (2010), Amanullah et al. (2011), Ali et al. (2012),

Aminu et al. (2014) and Ofori et al. (2015) in their studies. Amanullah et al. (2011) and Ali et al.

(2012) also reported positive hetrobeltiosis for plant height in their heterotic studies.

5.3.5 Ear height

In the heterotic study low level with negative nature of both mid parent and better parent

heterosis were exhibited by two of the four crosses, while, the other two crosses revealed

moderate levels of heterosis both as mid parent and better parent for ear height. Negative

heterosis for ear height represents that inbred lines would be used to develop hybrids with

reduced ear height which is desired for reducing incidence of stem and root lodging, and also in

stress condition. The positive magnitude of heterosis for ear height is expected due to dominance

and non-fixable epistasis. Similar results of heterosis with positive and negative magnitudes are

in harmony with the findings reported by Amanullah et al. (2011), Ali et al. (2012), Aminu et al.

(2014) and Ofori et al. (2015).

5.3.6 Ear weight

High heterotic values of positive mid and better parent were observed for ear weight in

all the crosses under study. Such high heterosis in the present study for ear weight might be due

to the presence of high genetic diverse inbred lines used as parents. To fully exploit the heterosis,

these inbred lines can be utilized effectively in the hybridization program for the improvement of

grain yield and related traits. These results of high heritably for ear weight are in agreement with

those reported by Saleh et al. (2002),Kustanto et al (2012), Aminu et al. (2014) and Jain

&Bharadwaj (2014) in most of their crosses.

5.3.7 Grain yield

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Although being a complex character of many contributing traits, high mid parent and

better parent heterosis was observed for grain yield. This study represents that inbred lines used

as parents in these crosses were having high genetic diversity. It also explains that inheritance of

grain yield was under control of dominance, over dominance and dominance type of non-allelic

interactions along with some pleotropic effects of various alleles in the hybrid combinations of

diverse inbred lines. As a premium goal of all breeding programs the high nature of heterosis for

grain yield could be effectively exploited in the production of maize hybrids with improved grain

yield. As an ideal crop for hybrid breeding maize has the ability to play an important role in the

food security due to its high yield potential and greater genetic diversity. It has been reported that

in future maize crop will be the main source of staple food and no other staple crop exhibits

enough hybrid vigor like maize (Ali et al., 2012). Similar results of high mid and better parent

heterosis have been reported by several researchers in their heterotic studies for grain yield Ali et

al. (2013), Kumar et al. (2014c) and Solalinde et al. (2014). In contrast Bekele et al.

(2013), Ali et al. (2014), Ofori et al. (2015) and Shadlou et al. (2015) observed negative

heterosis for grain yield in most of their maize crosses.


Mid parent heterosis observed for days to maturity in all crosses were negative in nature

ranging from -2.91 to -2.22 days in magnitude. Best parent heterosis was of positive and negative

nature with low values each in two crosses. This represents that dominant and dominant ×

dominant gene actions are involved in the inheritance of days to maturity. Due to dominant

control of the trait, these parental lines could be effectively utilized in maize hybrid breeding

programs for early maturing hybrids. Negative heterosis indicated the earliness of resultant

popcorn hybrids developed in this study. Earliness is desirable because of reasonable efficiency

under multiple cropping system, drought stress and land use efficiency. Our findings of negative

heterosis are similar to Appunu et al. (2007), Jabeen et al. (2007), Reddy et al. (2011), Jawaharlal

et al. (2012) and Jain and Baharadwaj (2014) in their studies for some of the crosses.

5.3.9 Ear diameter

Both mid and better parent heterotic values were positive in nature and of high magnitude

for ear diameter in all crosses used in this study. These findings disclosed that inbreds used in

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this study as parents in these crosses were having high genetic diversity. It also explains that

inheritance of ear length was under control of dominance, over dominance and dominance type

of non-allelic interactions along with some pleotropic effects of various alleles in the hybrid

combinations of diverse inbred lines. To fully exploit the heterosis these inbred lines should be

utilized effectively in the hybridization program for the improvement of ear diameter and other

yield related traits. These results of high heterosis for ear length were in agreement with those

reported by Bekele and Rao (2013), Kapoor et al. (2014), Kumar et al. (2014c) and Ofori et al.

(2015) in most of their crosses.

5.3.10Ear length

Both mid and better parent heterotic values were positive in nature with high magnitude

for ear diameter in all crosses used in this study. These findings disclosed that inbred parents

used in this study as parents in these crosses were having high genetic diversity. It also explains

that inheritance of ear length was under control of dominance, over dominance and dominance

type of non-allelic interactions along with some pleotropic effects of various alleles in the hybrid

combinations of diverse inbred lines. To fully exploit the heterosis, these inbred lines should be

utilized effectively in the hybridization program for the improvement of ear diameter and other

yield related traits. These results of high heterosis for ear length were in agreement with those

reported by Kapoor et al. (2014), Ali et al. (2014), and Ofori et al. (2015). In contrast Bekele&

Rao (2013) and Ofori et al. (2015) obtained negative heterosis in some of their crosses.


Being an important yield related trait hundred grain weight revealed high values for both

mid and better heterosis. High heterotic values were due to presence of non-additive gene action

in the form of dominance, dominance × dominance and some-what additive × dominance for

hundred grain weight. The better exploitation of the non-additive gene actions should be hybrid

development with increased grain weight. Similar results of positive heterosis were also reported

by Yosuf et al. (2014), Kumar et al. (2014c) and Ofori et al. (2015).


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In all crosses mid parent heterosis was positive in nature with high magnitude except PS-

2 × BD-1 in which its value was of moderate level. Similarly better parent heterosis calculated

for all crosses was positive in nature. Such presence of high heterotic values both for mid and

better parent indicated that non-additive gene action in the form of dominance and dominance ×

dominance for kernel rows per ear were involved in the genetic control this trait. These non-

additive gene actions could be efficiently utilized in the hybrid development with an increase in

kernel rows per ear. Our results of positive heterosis were supported by Aghaei et al. (2012),

Hussain (2013), Guerrero et al. (2014) and Ofori et al. (2015) who also found similar results of

positive heterosis for kernel rows per ear in their studies for some of the crosses. Guerrero et al.

(2014) and Kumar et al. (2014c) reported negative heterosis for kernel rows per ear.

5.3.13 Kernels row-1

Kernel per row is an important component of maize grain yield. Both mid and better

parent heterosis were positive with high magnitudes. Such presence of high heterotic values both

for mid and better parent indicated that non-additive gene action in the form of dominance and

dominance × dominance for kernel rows per ear were involved in the genetic control this trait.

These non-additive gene actions could be efficiently utilized in the hybrid development with

increased kernel rows per ear. Our results of positive heterosis are similar to Muraya et al.

(2006), Jain et al. (2014), Kumar et al. (2014c), Shadlo et al. (2015) and Ofori et al. (2015)

observing similar results of positive heterosis for kernels per row in their studies.

5.3.14 Kernels ear-1

Kernels per ear is an important grain yield parameter in maize. In all crosses mid parent

heterosis was positive in nature with high magnitude. Similarly better parent heterosis calculated

for all crosses was also high with positive nature. Such presence of high heterotic values both for

mid and better parent indicated that non-additive gene action in the form of dominance and

dominance × dominance for kernels per ear were involved in the genetic control this trait. These

non-additive gene actions could be efficiently utilized in the hybrid development with an

increase in kernels per ear. Our results of positive heterosis were confirmed by Amanullah et al.

(2011), who also observed positive mid and better parent heterosis in their study. The present

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results of mid and better parent heterosis are also corroborated by some previous researchers

including Tollenaar et al. (2004), Frascaroli et al. (2007) and Alam et al. (2008). They observed a

varying level of heterotic values for kernels per ear in F1 hybrids.


Both mid parent and better parent heterosis observed for biological yield in the studied

crosses were positive in nature with high magnitude. Such results of high heterosis is an

indication of greater genetic diversity among the parental inbred lines and non-allelic control in

the inheritance of biological yield. Due to dominant control of this trait these parental lines could

be effectively utilized in maize hybrid breeding programs for short stature hybrids. Our findings

of positive heterosis for biological yield are corroborated by Hussain et al. (2004) and Iqbal

(2009).


Like other grain yield related traits both mid and better parent heterotic values were

positive for percent shelling in all crosses used in this study. These findings disclosed a greater

genetic diversity among the inbred lines used as parents in these crosses. It also explains that

inheritance of percent shelling was under control of dominance, over dominance and dominance

type of non-allelic interactions along with some pleotropic effects of various alleles in the hybrid

combinations of diverse inbred lines. To fully exploit the dominant gene effects of percent

shelling, these inbred lines should be utilized in heterosis breeding program for the improvement

of grain yield and related traits. These results of positive heterosis for percent shelling were in

agreement with those reported by Jawaharlal et al. (2012), Abdel-Moneam et al. (2014) and

Kumar et al. (2014c).


Both mid parent and better parent heterosis observed for harvest index in the studied

crosses were positive in nature with high magnitude. Such results of high heterosis is an

indication of greater genetic diversity among the parental inbred lines and non-allelic control in

the inheritance of harvest index. To fully exploit the heterosis these inbred lines should be

utilized effectively in the hybridization program for the improvement of grain yield and other

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yield related traits. These results of positive heterosis for harvest index were in close conformity

with those reported by Tollenaar et al. (2004), Kapoor et al. (2014).

5.3.18 Popping volume

Popcorn expansion volume mainly rely on percent of unpopped grains and grain moisture

content at harvest. Ideal popcorn varieties should have low number of unpopped grains and grain

moisture of 13 to 14.5% at the time of popping (Ziegler, 2001). Being an important trait, popping

volume revealed high values for both at mid and better heterosis. High heterotic values were due

to presence of non-additive gene action in the form of dominance, dominance × dominance and

some-what additive × dominance for popping volume. The better exploitation of the non-additive

gene actions should be aimed at hybrid development with increased popping volume. Similar

results of positive heterosis were reported by Rangel et al. (2008) who also found similar results

of negative heterosis for popping volume while, estimating genetic parameters through diallel

analysis in popcorn. Miranda et al. (2008) also experienced reduced heterosis for popping

volume in Brazilian popcorn populations in relation to commercial cultivars.


Being an important quality character in popcorn, percent unpopped grains revealed

negative values of mid parent heterosis. Better parent heterosis was positive in all crosses except

one for percent unpopped grains. Negative heterotic values were indication of non-additive gene

action in the form of dominance and dominance × dominance with a negative impact on the

inheritance of unpopped grains. Such negative non-additive genes could be effectively utilized in

reducing the number of unpopped grains of popcorn hybrids. Our results of negative heterosis for

percent unpopped grains are also supported by Jele et al. (2014).

5.4 Genotypic and phenotypic association among traits

The correlation coefficients provide sufficient information about the level of relationship

and help plant breeders to exploit these information in an efficient way (Bocanski et al., 2009;

Nagabhushan et al., 2011). According to Hallauer and Miranda (1995) genetic correlation among

quantitative characters is due to pleiotropy and/or linkage disequilibrium. Correlation

analysis in plant breeding is mainly used to quantify the mutual relationship

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between various plant characters and identify the component characters on

which selection can be based for genetic improvement in yield (Singh and

Narayanan, 1993). For plant breeder the genotypic correlation coefficient is

more important because it represents the heritable association between two

variables (Falconer and Mackey, 1997). Correlation among traits generally indicate two

important factors viz. genetic (pleiotropic effects, linked genes) and environmental factors. As

indicated phenotypic correlation is measured from the phenotype and is the result of genetic as

well as environmental factors, while genetic correlations is the result of genetic factors (additive)

and provide crucial information about effective selection (Bocanski, et al., 2009). As

phenotypic correlation includes both phenotypic and environmental effects,

therefore significant phenotypic correlations without significant genotypic

correlation practical implications value. The reason of association among traits is an

essential tool for breeders to decide strategy for future breeding programs. Therefore, plausible

physiological, ecological, biochemical, molecular or genetic reasons of genotypic and

phenotypic associations among physiological traits and grain yield traits are discussed in detail in

the following paragraphs.

5.4.1 Genetic and phenotypic association among physiological traits

5.4.1.1 Day to 50 % tasseling

Both genetic and phenotypic association among days to tasseling, silking and anthesis

was positive and significant in all crosses. Such a positive significant association among

flowering traits is an indication for direct selection of promoting early maturity in maize crops.

Similar results of positive correlation were also reported by Abdulkhaleq and Tawfiq (2014),

Bekeleand Rao (2014), Azam et al. (2014) and Halidu et al. (2015).

Genetic association of days to tasseling with plant height was negative in all crosses

while, negatively significant in only two of the four crosses. Similarly phenotypic association

among days to tasseling, plant and ear height was negatively significant in all crosses. The

presence of positive relationships among these traits is an indication that desirable genes

controlling their inheritance could be effectively exploited in further breeding programs for

varietal improvement (Sujiprihati et al., 2003). Presence of genetic correlations indicated that the

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association among flowering traits is a true association as they exclude the environmental

variances. Our results of negative association between days to tasseling and plant height are

supported by Abdulkhaleq and Tawfiq (2014), who also observed negative association between

days to tasseling and plant height in maize in their study. Bekele and Rao (2014), Azam et al.

(2014) and Halidu et al. (2015) also reported negative association both at genetic and phenotypic

level of days to tasseling with plant height and ear height in their study under striga infested

environment. Contrasting results of positive association between days to tasseling and ear height

were observed by Abdulkhaleq and Tawfiq (2014) and Halidu et al. (2015) under striga free

environment.

Days to tasseling was positively and significantly correlated with days to maturity in all

crosses at both genetic and phenotypic level. Based on observed association one can say that

delay in tasseling is directly correlated with maturity, therefore a similar response could be found

from selection. Genetic correlation indicated that the association is a true one as it excludes the

environmental variances. Positive correlation also indicated that the genes controlling these traits

are highly linked or they might be under pleiotropic effects of some genes (Bocanski et al.,

2009). Our results of positive association between days to tasseling and maturity traits are in line

with that reported by Bekele and Rao (2014). They also observed significant association of

positive nature between days to tasseling and days to maturity.

5.4.1.2 Day to 50 % anthesis

In all crosses both genetic and phenotypic correlations between days to anthesis and

silking were positively significant. Such a positive significant association between flowering

traits is an indication of direct selection of early flowering in maize crop. Similar results of

positive correlation were also reported by Nzuve et al. (2014), Kinfe et al. (2015), Halidu et al.

(2015) and Mehri (2015). Genetic association between days to anthesis and plant height was

negative in all crosses but significant in only two of the four crosses. The presence of positive

relationships among these traits is an indication that desirable genes controlling their inheritance

could be effectively exploited in further breeding programs for varietal improvement (Sujiprihati

et al., 2003). Phenotypic correlation of days to anthesis with plant height was also negatively

significant in all crosses. Both genetic and phenotypic correlations of days to anthesis with ear

height were negative in nature in all crosses. Our results of negative association between days to

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anthesis, plant height and ear height are also confirmed by Oloyede-Kamiyo (2015), Halidu et al.

(2015) and Mehri (2015) who also reported negative association of days to anthesis with plant

and ear height in maize. Similarly our non-significant correlation of days to anthesis with plant

and ear height are also supported by Oloyede-Kamiyo (2015) who, observed positive association

between these traits. On other hand, contrasting results of positively significant association

between these traits were reported by Kinfe et al. (2015) while, dealing with different breeding

populations of maize crop. Days to anthesis was positively and significantly associated with days

to maturity in all crosses both at genetic and phenotypic level. Based on observed association one

can say that delay in any of these flowering characters is directly correlated with maturity,

therefore a similar response could be found from selection. It also indicates that selection based

on such genetic association would be inherited in the next generation. Or results of positive

association between days to anthesis and maturity traits are in line with that reported by Kinfe et

al. (2015). They also observed significant association of positive nature between days to silking

and days to maturity.

5.4.1.3 Day to 50 % silking

In all crosses both genetic and phenotypic correlations between days to silking and

anthesis were positive and significant in all crosses. Such a positive significant association

between traits is an indication for direct selection of early flowering in maize. Such positive

relationships among these traits is an indication that desirable genes controlling their inheritance

could be effectively exploited in further breeding programs for varietal improvement (Sujiprihati

et al., 2003). Similar results of positive correlation between flowering traits were also reported

by Bekele and Rao (2014), Azam et al. (2014), Halidu et al. (2015), Kinfe et al. (2015) and

Mehri (2015) in their maize populations.

Genetic association between days to silking and plant height was also negative in all

crosses but significant only for two of the four crosses. Similarly genotypic association between

days to silking and ear height was negative in all crosses but significant in one cross only.

Phenotypic correlation of both days to silking and anthesis with plant and ear height was

negatively significant in all crosses. Our results of negative association of days to silking with

plant and ear height are also supported by Bekele and Rao (2014), Halidu et al. (2015) and Mehri

(2015) who also found significant negative association between days to silking and plant height

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in maize. Negative but non-significant genetic correlation between days to silking and plant

height was also reported by Halidu et al. (2015). Similarly our results of non-significant

correlation are also supported by Abdelmula and Sabiel (2007), Sumathi et al. (2005) and

Haliduet al. (2015) who, observed positive association between these traits. On the other hand,

contrasting results of positively significant association between these traits were reported by

Beyene (2005), Sumathi et al. (2005) and Kinfe et al. (2015) while dealing with different

breeding maize populations.

Days to silking and anthesis were positively and significantly associated with days to

maturity in all crosses both at genetic and phenotypic level. Based on observed association one

can say that delay in any of these flowering characters is directly correlated with maturity,

therefore a similar response of positive or negative magnitude could be found based on selection

criteria. Our results of positive association between days to silking and maturity traits were in

line with that reported by Bekele& Rao (2014) and Kinfe et al. (2015). They also observed

significant association of positive nature between days to silking and days to maturity both at

genetic and phenotypic level.

5.4.1.4 Day to maturity

As maturity is an important character being extensively utilized in maize breeding

programs. Days to maturity was positively and significantly correlated with flowering characters

in all crosses both at genetic and phenotypic level. Such results of positive association between

maturity and flowering characters is an indication that desirable genes controlling maturity

inheritance could be effectively exploited in further breeding programs for varietal improvement

(Sujiprihati et al., 2003). Presence of both genetic and phenotypic correlations indicated that

environmental effect was not too much on these traits. Similarly genetic correlation of days to

maturity with plant and ear height was negative in all crosses but only one cross and two crosses

in this relation reached to a significant level for plant and ear height, respectively. Days to

maturity was negatively and significantly correlated in three of crosses with plant and ear height

at phenotypic level. Such a negative association represented that delay in maturity was inversely

correlated with plant and ear height. These negative correlations have also been reported by

earlier scientists like Bekele and Rao (2014) and Kinfe et al. (2015). Shukla and Mishra (2013)

reported a contrasting relationship of days to maturity with plant and ear height.

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5.4.1.5 Plant height

Plant and ear height were positively and significantly correlated in three of the four

crosses in which only one cross showed significant level of genetic correlation, while in one

cross the genetic association between plant height and ear height was negatively non-significant.

Phenotypic correlation of plant height was negative and significant with all flowering traits

including days to tasseling, silking and anthesis. Sujiprihati et al. (2003) also reported similar

results of positive relationships between plant and ear height, and suggested its exploitation in

varietal improvement programs. The association of plant and ear height at genetic and

phenotypic level implies the presence of a strong genetic relationship (Zeeshan et al., 2013).

Bekele and Rao (2014), Azam et al. (2014), Oloyede-Kamiyo (2015) and Kinfe et al. (2015)

findings, also support our results of positive and significant correlation between plant and ear

height both at genetic and phenotypic level.

5.4.2 Association among flowering and plant characters

5.4.2.1 Days to 50% tasseling

Days to tasseling was positively and significantly correlated with days to anthesis and

silking both at genetic and phenotypic level in all the crosses, showing that early tasseling will

result into early anthesis as well as silking. These results of high association among these

flowering attributes both at genetic and phenotypic level are in line with that reported by Bekele

and Rao et al. (2014). Genetic and phenotypic association of days to tasseling with plant and ear

height was found negative in all the crosses. Phenotypic correlation of days to tasseling with

plant and ear height was significant while, at genetic level it was significant with plant and ear

height only in two and one crosses, respectively. Such negative relation of tasseling with plant

and ear height might be due to the diversion of nutrient to pollen and grain formation, the

potential sink that might deplete supply to others and thus cause a reduction in both plant and ear

height. Azam et al. (2014), Bekele and Rao et al. (2014) and Kwaga (2014) also obtained similar

results of negative and significant correlations for these traits in their studies. Azam et al. (2014)

also reported negative genetic and phenotypic correlation of non-significant nature of days

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tasseling with plant and ear height. In contrast positive correlations of days to tasseling with

plant and ear height were also observed by Dugje et al. (2014). Days to tasseling was negatively

correlated with ear weight and grain yield. The nature of correlation among days to tasseling, ear

weight and grain yield was significant only in one cross at genetic level and two crosses at

phenotypic level. Delay in tasseling will reduce the time allocated for grain formation and filling

which results into an antagonistic relation among tasseling, ear weight and grain yield. Such a

negative association between flowering and yield characters is the main cause of reduced yield in

late flowering varieties in maize. Our results of negative relationship among these traits were in

consistence with that reported by Azam et al. (2014) and Kwaga (2014). Dugje et al. (2014)

observed positive and significant correlation between days to tasseling and grain yield.

5.4.2.2 Days to 50% anthesis

Days to anthesis was positively and significantly correlated with days to silking both at

genetic and phenotypic level in all four crosses. This indicates that positive association among

maturity characters is genetically controlled in all the studied crosses. In such case selection for

early male flower initiation will also lead to early female flowering. Similar results of positive

association at genetic and phenotypic level were also observed by some early researchers

including Nzuve et al (2014) and Ohunakin & Adebisi (2015). Genetic association of days to

anthesis with plant and ear height was negatively significant in two crosses for plant height and

one cross for ear height, while phenotypic association was negative and significant in all crosses.

These observations exhibit that early silking would result into the partitioning of photosynthates

for plant growth as well as grain formation and due to such competition reduction in plant and

ear height occur. These negative associations of days to anthesis with plant and ear height are

genetically controlled only in two and one crosses, respectively. Such a negative association of

flowering with plant characters was also reported by Bello et al. (2014). Nzuve et al. (2014)

observed completely opposite results of positive and significant association at genetic and

phenotypic level for days to anthesis, plant and ear height. Bello et al. (2014) also reported

positive correlation between days to anthesis and plant height. Negative and significant

phenotypic correlation was found among days to anthesis and ear weight and grain yield in two

of the four crosses, while genetic correlation was negative but non-significant in all the four

crosses. From the results it is clear that the negative association of days to anthesis with ear

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weight and grain yield was mostly affected by environment with low genetic control. Similar

results of negative and significant correlation among days to anthesis, cob weight and grain yield

has been reported by Ohunakin and Adebisi (2015) and Richard et al. (2015). Inconsistent

reports of positively significant, genetic and phenotypic association of days to anthesis with ear

weigh and grain yield have been reported by Bello et al. (2014) and Nzuve et al. (2014).

5.4.2.3 Days to 50% silking

Days to silking was negatively and significantly correlated with plant and ear height at

phenotypic level in all the crosses, except one for ear height with non-significant correlation.

Similarly genetic correlation between days to silking and plant height was negatively significant

in two of the four crosses, while days to silking was negatively and significantly correlated at

genetic level only in one cross. In one single cross non-significant association of negative nature

was observed between days to silking and ear height. Such negative associations of days to

silking with plant and ear height may be due to the portioning of dry matter yield and might be

an indication for stunted plant growth due to late maturity. Similar finding of negative

correlations were also reported by earlier scientists like, Bekele and Rao et al. (2014), Hadidi et

al. (2014) and Kumar et al. (2014b). Azam et al. (2014) also reported similar results of negative

correlation both at genetic and phenotypic level but with non-significant nature. Dugje et al.

(2014) findings about association of days to silking, plant and ear height were inconsistent to our

reports. Phenotypically days to silking was negatively and significantly correlated with ear

weight and grain yield only in two crosses. Likewise genetic correlation of days to silking with

ear weight and grain yield was negative but non-significant in all the crosses. It is indicated from

these results that early silking provide more time for the transportation of photosynthates to grain

formation due to which earliness in silking was related to high grain weight and grain yield.

Dugje et al. (2014) also reported negative but significant correlation between days to silking and

ear weight, while their findings regarding correlation of days to silking and grain yield were

quite opposite to our results. Our results of negative non-significant correlation both at genetic

and phenotypic level were in line with that reported by Azam et al. (2014), Bekele and Rao et al.

(2014), Kumar et al. (2014b).


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Plant height was positively and significantly correlated at phenotypic level with ear

height in two of the four crosses, while in one cross it couldn’t reach significance level. Negative

phenotypic correlation was also observed in one cross but it was non-significant in nature.

Similarly genetic correlation of positive and significant nature was found only in one cross

between plant and ear height. This shows that correlation between plant and ear height is

environmentally influenced in most of the crosses. Positive association of plant height with ear

height was also reported by Azam et al. (2014), Kumar et al. (2014b) and Rahman et al. (2015).

Negative association between plant and ear height, reported by Bello et al. (2014) was in

agreement to that observed in one of our cross. Positive and significant correlation of plant

height both at genetic and phenotypic level was obvious with ear weight and grain yield in two

and three crosses, respectively. Due to the positive and significant nature of correlation, the

parental inbred line could be used for improvement of these traits. Positive and significant

association means taller plants will give high grain yield and should be utilized in selection for

yield improvement. From such findings of positive correlations among plant height, ear height,

ear weight and grain yield we can conclude that selection for any of these correlated traits, may

lead to selecting high yielding inbred lines. Our results of positive association between plant

height and grain yield are also supported by Malik et al. (2005), Bello et al. (2014), Kumar et al.

(2014b) and Rahman et al. (2015). In contrast, Azam et al. (2014) reported negative genetic and

phenotypic correlation between plant height and grain yield with non-significant nature.

5.4.2.5 Ear height

Strong positive phenotypic correlation was recorded between ear height and ear weight in

two crosses, while opposite results of negatively significant correlation were observed between

the same traits in another single cross. Genetic correlations of ear height with ear weight and

grain yield were non-significant in all the crosses with positive and negative magnitudes equally.

Non-significant nature of association represents that influence of environmental effect was

comparatively high than genetic effects. Positive and negative significant association between

ear height and grain yield was reported in one cross each. Our results of positive correlation were

in close conformity with that of Malik et al. (2005), Bekele and Rao (2014) and Kumar et al.

(2014b), while results of negative correlation are supported by Azam et al. (2014).

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5.4.3 Genetic and phenotypic association among physiological and yield related traits

5.4.3.1 Days to 50 % tasseling

Genetic correlation of days to tasseling was negative with all grain yield related traits in

two of the four studied crosses except, number of grains per row. Although association of days to

tasseling with fresh ear weight was negative in all crosses at genetic level but in only one cross it

reached to significance level. Similarly phenotypic correlation between these traits was also

negative and significant in two crosses only. Based on the results obtained it can be assumed

that, transportation of metabolic assimilates was high and was for longer time in the later

reproductive stages compared to earlier stages due to which grain formation and grain filling

received maximum in early flowering plant. Shukla and Mishra (2013) reported positive

association of days to tasseling with ear weight in their maize germplasm.

Genetic association of days to tasseling with number of kernel rows, number of grains per

row and number of grains per cob was negative and significant in two crosses. Phenotypic

correlation of days to tasseling with number of kernel rows per ear was negatively significant in

nature in three crosses while, this association of days to tasseling with grains per row and grains

per cob was negative and significant in two crosses only. A positive and non-significant

association was also observed between tasseling and grains per row in a cross. Such results of

negative association indicated that early tasseling will promote number of kernel rows, grain per

row and grains per cob in maize crop. Similar negative association of days to flowering with

number of kernels in maize has been observed by Dhliwayo (2008).

Genetic correlation of days to tasseling with grain yield and harvest index was negatively

significant in one cross only. On the other-hand phenotypic correlation of these traits was also

negative in all crosses but significant in two crosses. The presence of such negative and

significant relationship indicated that early maturing genotypes will produce high yield and this

association will also be inherited in some cross. It means that in production of high yielding

hybrids, days to flowering will be effectively utilized via indirect selection. Shukla and Mishra

(2013) reported positive association of days to tasseling with grain yield. Both genetic and

phenotypic correlations of days to tasseling and harvest index were found negative by Shukla

and Mishra (2013).

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The genetic correlation between days to tasseling and biological yield was negative and

non-significant in all crosses. Phenotypic correlation between days to tasseling and biological

yield was of negative nature in all crosses but significant in two crosses only. Such a negative

association of days to tasseling with grain, biological yield and its related attributes indicate that

delay in maturity will lead to a reduction in biological yield. Negative association of days to

tasseling with biological yield indicated that in late flowering genotypes, the biological yield will

be low resulting a low grain yield. Association of days to tasseling with hundred grain weight

was negative both at genetic and phenotypic level, while significant at phenotypic level in a

cross. Shukla and Mishra (2013) reported positive association of days to tasseling with biological

yield.

5.4.3.2 Days to 50 % anthesis

The genetic and phenotypic correlations of days to anthesis were negatively significant

with yield and related traits in all crosses except, number of grains per row in a cross where the

phenotypic association was positively non-significant. In first two crosses having common

female parent the association of days to anthesis was negative and non-significant in nature with

all yield related traits both at genetic and phenotypic level. Similarly anthesis was significantly

associated at phenotypic level with ear length in 1st cross. Shukla and Mishra (2013) reported

positive association of days to tasseling with grain yield and ear length.

Days to anthesis was negatively and significantly correlated with ear diameter only in one

cross. Similarly the phenotypic correlation between days to anthesis and ear diameter was also

negative and significant in all crosses. Such results of negative association indicated that

transportation of assimilates occurred more frequently and for longer time in the later

reproductive stages compared to earlier stages due to which earliness in anthesis was related to

high ear diameter. Our findings of negative correlation are contradictory to the findings of

Shukla and Mishra (2013) regarding association of days to anthesis and ear diameter.

The genetic correlation of days to anthesis with number of kernel rows per ear and

number of grains per row was significant with high negative magnitude in two crosses, while

such association of negative and significant nature was also observed between days to anthesis

and number of grains per cob in one cross only. At phenotypic level, the association among days

to anthesis, number of kernel rows, number of grains per row and number of grains per cob was

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negative and significant in two of the four crosses, only one cross revealed a positive non-

significant correlation between days to anthesis and number of grains per row. Such results of

negative association have also been cited by Dhliwayo (2008).

Association both genetic and phenotypic was negative and non-significant between days

to anthesis and hundred grain weight except, in a cross where the association was significant. As

the relation was negative, therefore early anthesis will provide extended time for grain filling due

to which grain weight will be high. Similar results of negative association between days to

anthesis and hundred grain weight were also reported by Dhliwayo (2008).

5.4.3.3 Days to 50 % silking

Genetic correlation of days to silking was negative and non-significant with yield and all

its related characters in first two crosses. The phenotypic correlation of days to anthesis was

negative and significant with fresh ear weight in two crosses while, the genetic correlation was

negative in all crosses but could not reach to significance level. The positive and non-significant

correlation between days to silking and ear weight was reported by Shukla and Mishra (2013).

Days to mid silking showed negative association of non-significant nature with shelling

percentage both at genotypic and phenotypic levels in two crosses, while association between

these traits was positive and non-significant in other two crosses. These results were in line with

the results obtained by Sujiprihati et al. (2003). They have also reported negative relationship

between these traits but their results were significant which might be due to differences in the

climatic conditions in the testing sites as well as in the genetic make-up of the material studied.

The phenotypic association of days to silking with ear diameter and ear length was

negative and significant in all crosses except one where the association was negative in nature.

Similarly genetic correlation between days to silking and ear diameter was of negative

magnitude in all crosses but only one cross revealed significant nature of that association. These

findings indicated that long ears size is inversely correlated to the silking days. In later

reproductive stages transportation of assimilates is too frequent and for longer time than early

stages due to which earliness in silking resulted in longer ears. Similar results of negative

correlation were also reported by Sujiprihati et al. (2003), who also reported significant

association of negative nature between days to silking and ear length in their study on maize. In

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contrast positive and significant association has been reported in literature for these two traits by

Beyene (2005) and Shukla and Mishra (2013).

Both genetic and phenotypic correlations of days to silking were negative with cob

characters like kernel rows per ear, number of grains per row and number of grains per cob in all

crosses. The association of days to silking with number of kernel rows, number of grains per row

and number of grains per cob was negative and significant in two of the four crosses at genetic

level. Similarly phenotypic correlation of kernel rows per ear, grains per row and days to silking

were negative and significant in three of the four studied crosses. Phenotypic correlation of days

to silking was positive and non-significant in a cross. Our results of negative association are also

confirmed by Sujiprihati et al. (2003) and Dhliwayo (2008). Sumathi et al. (2005) and Shukla

and Mishra (2013) observed non-significant relationship of negative nature between days to

silking and number of kernel rows ear-1 in their studies on maize.

Genetic association of days to anthesis and hundred grain yield was negative and non-

significant in all crosses. Similarly phenotypic correlation between these traits was also negative

in all crosses but only one cross reached to a significant level. Non-significant positive

association between these traits are in close conformity with the results reported by Sujiprihati et

al. (2003) and Beyene (2005), while Sumathi et al. (2005) reported positive association between

days to silking and 100-grain weight with significant magnitude.

Days to mid silking was negatively and non-significantly correlated with grain yield,

biological yield and harvest index at genetic level in all crosses. Similarly phenotypic association

among these traits was also negative in nature in which only two crosses reached to a significant

level. Similar reports of negative association between days to silking and grain yield have also

been cited by Umakanth et al. ( 2000), Sujiprihati et al. (2003), Sumathi et al. (2005), Sadek et

al. (2006) and Abdelmula and Sabiel (2007).

5.4.3.4 Days to maturity

Maturity is an important character being utilized in breeding programs of maize. Genetic

and phenotypic association of maturity and all yield related characters was negative and non-

significant in nature in first cross. In second cross correlation of days to maturity was positive

and non-significant with fresh ear weight, grains per row, grains per cob, grain yield, biological

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yield and harvest index both at genetic and phenotypic level. Shukla and Mishra (2013) observed

positive correlation of days to maturity with grain yield attributes.

In third cross genetic correlation of days to maturity was of negative and non-significant

nature with fresh ear weight, ear diameter, ear length, number of kernel rows, hundred grain

weight, grain yield, biological yield and harvest index. Such association of days to maturity was

negatively and significantly correlated with number of grains per row and number of grains per

cob. Phenotypic association of days to maturity was negative and significant with ear diameter,

number of kernel rows, number of grains per row and number of grains per cob in the same

cross. Association of days to maturity with grain yield, biological yield and harvest index was

although negative but non-significant in nature. Both genetic and phenotypic correlations of

maturity with ear diameter, number of kernel rows, grains per row and grains per cob were

negative and significant in forth cross. Similarly phenotypic and genetic association of days to

maturity with grain yield, biological yield and harvest index was although negative but non-

significant in nature. Shukla and Mishra (2013) also confirmed non-significant association of

days to maturity and ear weight, ear length, ear diameter and grain yield at genetic level.


Both genetic and phenotypic correlations of plant height with fresh ear weight were

positive in all crosses in which two reached to a significant level. This indicated that selection for

plant height would also increase fresh ear weight. In such association, plants of high stature

would probably have more number of leaves that will trap more sun light and lead to an

increased amount of photosynthates in plant. Our results of positive association between plant

height and ear weight were in line with that reported by Shukla and Mishra (2013). Dhliwayo

(2008) reported contrary results between plant height and kernel weight of negative correlation

both at genetic and phenotypic level.

Genetic correlation of plant height and ear diameter was positive in all crosses in which

only one cross revealed significant level. Similarly phenotypic correlation of plant height and ear

diameter was positively significant in two of the four crosses. The genetic association of ear

length and plant height was positively significant in two crosses while, in other two crosses the

relationship was positive and non-significant. Correlation between plant height and ear length

was positive and significant in all crosses at phenotypic level. Shukla and Mishra (2013), Kumar

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et al. (2014b) and Haddadi et al. (2014) also reported positive association of plant height with

these yield related traits.

Genetic and phenotypic correlation of plant height and number of kernel rows per ear was

positive in nature in all crosses. Positive and significant association both at genetic and

phenotypic level between plant height and kernel rows was found only in one and three cross,

respectively. Such results indicated that an increase in plant height will cause an increase in ear

kernel rows. Similar results of positive correlation between plant height and kernel rows have

been reported by Kumar et al. (2014b) and Abdullah et al. (2015) in their trial during 2011.

Genetic correlations of plant height with number of grains per row and number of grains

per cob were positive and significant in two of the four crosses. Similarly phenotypic correlation

of plant height with number of grains per cob was positively significant in all crosses while, with

number of grains per row the association was positively significant in three crosses. From such

results we can predict that if we are making selection for plant height ultimately we are selecting

genotypes with high grains per row and grains per cob as well. We could say that in high plants

the ability of trapping sunlight will be more compared to the dwarf one, that’s why they perform

better in yield characters also. Our results of positive association were in also in close conformity

with that reported by Kumar et al. (2014b) and Abdullah et al. (2015).

Phenotypic correlation of plant height with hundred grain weight was positive and

significant in three crosses while, the genetic association between these traits was although

positive in all crosses but significance level was achieved by only two of them. Such results

indicated that association of plant height and hundred grain weight is positive which will lead to

the selection of genotypes superior both in plant height and grain weight. Our results of positive

association were in contrast with that reported by Kumar et al. (2014b), Haddadi et al. (2014)

and Abdullah et al. (2015).

Both genetic and phenotypic correlations of plant height with grain yield and biological

yield were positive and significant in two crosses. The association of these characters was

positive in all crosses indicating an increase in plant height will not only increase biological yield

but grain yield will also be enhanced. Haddadi et al. (2014) and Abdulla et al. (2015) reported

both positive and negative association of grain yield and plant height in their trials conducted in

two different seasons. Kumar et al. (2014b) also obtained positively significant association of

plant height with grain yield.

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Genetic correlation of plant height with harvest index was positive and significant in one

of the four crosses. Similarly the phenotypic correlation was also positive between plant height

and harvest index. Shukla and Mishra (2013) reported negative association between plant height

and harvest index.

5.4.3.6 Ear height

The genetic and phenotypic associations of ear height and fresh ear weight were positive

in two crosses while, other two crosses expressed negative and non-significant association

between these traits. Association of ear height and fresh ear weight was positive and significant

only at phenotypic level in two crosses. This indicated that selection for ear height would also

increase fresh ear weight in case of positive association. In contrary there will be a reduction in

fresh ear weight if selection is practiced for higher ear height. Similar results of positive but non-

significant correlation have been reported by Haddadi et al. (2014).

Genetic correlation of ear height with both ear diameter and ear length was non-

significant but positive and negative in nature, respectively in two crosses each. Similarly

phenotypic correlation of ear height with ear diameter and ear length was positively significant in

two of the four crosses. In two crosses, phenotypic association of these traits was negative in

nature. Presence of such contrasting results of ear height with yield related traits that while

making selection on this relation we must be too curios. Kumar et al. (2014b) and Haddadi et al.

(2014) also reported similar results of positive association of ear height with ear length and ear

diameter.

Genetic and phenotypic correlation of ear height and number of kernel rows per ear was

positive and significant in only one cross. Two of the four crosses revealed negative and non-

significant correlation between ear height and kernel rows. Phenotypic correlation between ear

height and kernel rows per ear was positive and significant in two crosses while, one cross

represented negative and significant association between these traits. Such results indicated that

an increase in ear height will cause an increase in ear kernel rows in two crosses while, a

concomitant decrease in number of kernel rows in other two crosses. Similar results of positive

correlation between ear height and kernel rows have been reported by Shukla and Mishra (2013),

Kumar et al. (2014b) and Haddadi et al. (2014).

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Genetic correlation of ear height with number of grains per row was positive and

significant in two of the four crosses. Likewise genetic correlation between ear height and

number of grains per cob was positively significant only in one cross. Similarly in other two

crosses such genetic correlation was negative. Phenotypic correlation of ear height with number

of grains per row and number of grains per cob was positively significant in three crosses. From

such results it is concluded that in case of positive correlation if we are making selection for ear

height, ultimately we are selecting for higher grains per row and higher grains per cob as well,

otherwise the results will be opposite in negative association. We could say that in plants with

low or medium ear height the performance will be better in yield characters. Our results of

positive association were in also in close conformity with that reported by Shukla and Mishra

(2013) and Kumar et al. (2014b).

Genetic correlation of ear height with hundred grain weight was positive and significant

in only one cross while, two crosses expressed negative association at genetic level. Phenotypic

correlation of ear height and hundred grain weight was positive and significant in two crosses

while, negative and significant in one cross. Such results indicated that association of ear height

and hundred grain weight is positive which will lead to the selection of genotypes superior in

both with higher ear height and grain weight. Similarly in case of negative association the

hundred grain weight will reduce if selection is made for ear height. Such negative results might

be due to easy lodging of plants with high ear height compared to optimum one. Our results of

positive association were in also in close conformity with that reported by Kumar et al. (2014b)

and Haddadi et al. (2014).

Phenotypic correlation of ear height with grain yield, biological yield and harvest index

was negative and of significant nature in one cross, while positively significant in other single

cross. One cross each represented negative non-significant and positive non-significant

correlation of ear height with these three traits. The genetic correlation association of ear height

was positive and non-significant in two crosses. The positive association of these characters in

some crosses indicated that an increase in ear height will not only increase biological yield but

grain yield as well. Similarly in case of negative association the plant with high ear height would

produce low grain and biological yield. Our results of association among plant height, grain

yield, biological yield and harvest index were in line with that reported by Kumar et al. (2014b)

and Haddadi et al. (2014).

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5.4.4 Genetic and phenotypic association of physiological traits with popping characters

5.4.4.1 Flowering characters

Genetic correlation of days to tasseling, silking and anthesis was positively and non-

significantly correlated with expansion volume. Similarly phenotypic correlation of expansion

volume was also positive with days to tasseling, silking and anthesis in all crosses but one cross

revealed significant level of that association. Our results of positive correlation between

expansion volume and flowering character were confirmed by Dhliwayo (2008).

Genetic correlation of days to tasseling, silking and anthesis was positively and non-

significantly correlated with percent unpopped grains. Similarly phenotypic correlation of

percent unpopped grains was positive with days to silking in three crosses while, days to

tasseling and anthesis were positively and significantly correlated with unpopped grains in two

crosses only.

5.4.4.2 Plant characters

Genetic correlation between plant height and expansion volume was negative and non-

significant in all crosses. Similarly phenotypic correlation of expansion volume and plant height

was also negative in all crosses but only one cross revealed significant level of this relation.

Genetic correlation between ear height and expansion volume was negatively non-significant and

positively non-significant in two crosses each. Phenotypic association was negatively and

positively significant in one cross each. Our results of negative correlation between plant

characters and expansion volume were in line with Dhliwayo (2008).

Genetic correlation between plant height and percent unpopped grains was negative and

non-significant in three of the four crosses. Similarly phenotypic correlation of percent unpopped

grains and plant height was also negative but significant in three crosses. Genetic correlation

between ear height and percent unpopped grains was negatively non-significant all crosses.

Similarly phenotypic association between ear height and percent unpopped grains was also

negative in all crosses but significant level was obvious in only one cross.

5.4.4.3 Days to maturity

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Both genetic and phenotypic associations of days to maturity and expansion were positive

and non-significant in all crosses, while genetic correlation of days to maturity with percent

unpopped grains was positive in all crosses but only one cross attained significant level of this

correlation. Phenotypic correlation between days to maturity and percent unpopped grains was

positively significant in three crosses. Results indicated that as the days to maturity increase the

number of unpopped grains will be high. Such positive association between these traits is also

supported by Dhliwayo (2008).

5.4.5 Genetic and phenotypic association among yield related traits

5.4.5.1 Fresh ear weight

The genetic correlation of fresh ear weight and percent shelling was positive and

significant in two crosses. Likewise the phenotypic correlation of fresh ear weight and percent

shelling was positively significant in three crosses. Such a positive correlation between these

traits could be effectively utilized in improvement of grain yield. Our results of positive

association between fresh ear weight and percent shelling were reported by Shukla and Mishra

(2013).

The genetic correlation of fresh ear weight with ear diameter was although positive in all

crosses but significant in only one cross. Likewise the phenotypic correlation of fresh ear weight

and ear diameter was positively significant in three crosses. Such a positive correlation between

ear diameter and ear weight is an indication of improved grain yield. Our results of positive

association between ear weight and ear diameter were in close conformity with that reported by

Shukla and Mishra (2013).

Both genetic and phenotypic correlations between fresh ear weight and ear length were

highly positive and significant in all crosses. Such a strongly positive relationship between these

important yield related traits would certainly improve the yield to its maximum level. Such a

positive correlation between fresh ear weight and ear length was also reported by some previous

researchers like Shukla and Mishra (2013).

Both genetic and phenotypic correlation of fresh ear weight with all cob characters like

number of kernel rows per ear, number of grains per row and number of grains per cob was

positive and significant in all crosses. Significantly positive association of these important yield

characters indicated that selection for any one of them will increase grain yield. Such results of

162

positive correlation among these traits have also been reported by some previous researchers like

Dhliwayo (2008).

Both genetic and phenotypic correlation of fresh ear weight with grain yield, biological

yield and harvest index was highly positive and significant in all crosses. Significantly positive

association of these important yield and yield related traits indicated that while making selection

based on fresh ear weight will increase grain yield as well. This also suggested that indirect

selection would be fruitful for increasing grain yield. Positive and significant association of fresh

ear weight with grain yield have also been reported by Henfy (2011) and Oktem (2008).

5.4.5.2 Percent shelling

The association of percent shelling with ear diameter was positively significant only in

one cross, while one cross exhibited negative and non-significant correlation both at genetic and

phenotypic level. Such association of shelling percentage with ear diameter was also reported by

Kumar et al. (2014b).

Association between percent shelling and ear length was positively significant at genetic

level in two crosses, while in other crosses, this association was positive but non-significant in

nature. Phenotypic correlation of percent shelling with ear length was positively significant in

three crosses. Such association of shelling percentage with ear diameter was also reported by


Genetic association of percent shelling with number of kernel rows, number of grains per

row and number of grains per cob was positively significant in one cross only. In one cross both

genetic and phenotypic correlation between percent shelling and number of kernel rows was

negative and non-significant. Similarly phenotypic correlation of percent shelling with number of

kernel rows, number of grains per row and number of grains per cob was positively significant in

two crosses. Such association of shelling percentage with ear diameter was also reported by


Correlation of percent shelling with yield and related traits was positive in all crosses.

Genetic correlation of percent shelling with hundred grain weight, grain yield, biological yield

and harvest index was positively significant in two of the four crosses. Phenotypic correlation of

percent shelling with hundred grain weight, grain yield, biological yield and harvest index was

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found positive and significant in three crosses. Positive and significant association between grain

yield and shelling percentage have been reported by Kumar et al. (2014b).

5.4.5.3 Ear diameter

Genetic association of ear diameter with ear length was positive in all crosses in which

only two crosses achieved a significant level. Similarly phenotypic correlation of ear diameter

with ear length was positively significant in three crosses. Our results of positive were in

consensus with that reported by Kumar et al. (2014b).

Both genetic and phenotypic correlation of ear diameter and number of kernel rows,

number of grains per row and number of grains per cob were positive and significant in all

crosses. This indicated that an increase in ear diameter will also increase kernel rows, grain per

row and grains per cob which are important grain yield characters. Our results of positive

association are in line with that reported by Kumar et al. (2014b).

Association between ear diameter with grain yield, biological yield and harvest index was

positively significant at genetic level in one cross, while in other crosses this association of ear

diameter with these traits was positive but non-significant in nature. Phenotypic correlation of

ear diameter with grain yield, biological yield and harvest index was also positive in all crosses

in which three crosses attained significant level. It is obvious from the results that making

selection for ear diameter will also have a positive impact on grain yield. Similar results were

also obtained by some earlier researchers like Broccoli &Burak (2004) and Kumar et al. (2014b).

5.4.5.4 Ear length

Genetic association of ear length with number of kernel rows was positively significant in

three of the four studied crosses. Similarly phenotypic correlation of ear length with number of

kernel rows was positively significant in all crosses. Positive and significant association between

these grain yield characters indicated that selection practiced for improvement of one character

will not only have direct impact on other but also will be heritable in nature. Our results of

positive were in consensus with that reported by Kumar et al. (2014b). Seyedzavar et al. (2015)

obtained negative correlation between ear length and number of kernel rows per ear.

Genetic correlation of ear length with number of grains per row and number of grains per

cob were positive and significant in three of the four crosses. Similarly phenotypic correlation of

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ear length with grains per row and grains per cob were positively significant in all crosses. This

indicated that an increase in ear length will also increase grain per row and grains per cob which

are important grain yield characters. Our results of positive association were in consensus with

that reported by Kumar et al. (2014b) and Seyedzavar et al. (2015).

Association between ear length with grain yield biological yield and harvest index was

positively significant at genetic level in one cross only, while in other crosses thus association of

ear length with these traits was positive but non-significant in nature. Phenotypic correlation of

ear length with grain yield, biological yield and harvest index was also positive and significant in

all crosses. Such a positive association of ear length with grain yield is of utmost importance

because selection made on such association will improve grain yield to a significant level.

Similar results of positive association have been reported in literature including Broccoli and

Burak (2004), Kumar et al. (2014b) and Seyedzavar et al. (2015).

5.4.5.5 Kernel rows ear-1

Genetic association of number of kernel rows per ear with number of grains per row and

number of grains per cob was high and positively significant with number of grains per row and

number of grains per cob in all crosses. Similarly phenotypic correlation of kernel rows per ear

with number of grains per row and number of grains per cob was also positively significant in all

crosses. Such a positive and significant association of kernel rows per ear, grain per row and

grains per cob could be effectively utilized in selection process for improved grain yield. Our

results of positive association were in consensus with that reported by Kumar et al. (2014b),

Seyedzavar et al. (2015) and Abdullah et al. (2015). Erazo-barradas (2009) also observed

positively significant association between number of kernel rows and grains per row.

The genetic association of kernel rows per ear with hundred grain weight was positively

significant in two of the four studied crosses. Similarly phenotypic correlation between number

of kernel rows per ear and hundred grain weight was positively significant in all crosses. Our

results of positive correlation were confirmed by Seyedzavar et al. (2015) and Abdullah et al.

(2015). Kumar et al. (2014b) obtained negative and non-significant association between kernel

rows and hundred grain weight both at genetic and phenotypic level.

Genetic association of number of kernel rows per ear with grain yield and harvest index

was positively significant in all crosses, while with biological yield genetic association was

165

positive and significant in three crosses. Similarly phenotypic correlation of kernel rows per ear

with grain yield, biological yield and harvest index was also positively significant in all crosses.

Such a positive and significant association of kernel rows per ear grain yield, biological yield and

harvest index could be effectively utilized in selection process for improved grain yield.

Mohammadi et al. (2003), Jamshidian et al. (2013),Kumar et al. (2014b), Seyedzavar et al.

(2015) and Abdullah et al. (2015) also reported results of positive and significant association

between grain yield and number of kernel rows per ear.

5.4.5.6 Grains row-1

Both the genetic and phenotypic associations of number of grains per row was positively

significant with grains per cob in all crosses. Similarly genetic correlation of grains per row was

positive and significant with hundred grain weight in three crosses while, phenotypic correlation

was positive and significant in four crosses. Similar results have also been cited in literature by

some previous researchers like Seyedzavar et al. (2015) and Abdullah et al. (2015).

Number of grains per row was positively correlated with grain yield in all crosses, in

which only two crosses exhibited a significant at genetic level. Phenotypic correlation of grains

per row was positively and significantly correlated with all crosses. Such a positive association

indicated that grains per row would significantly affect grain yield in a desired direction. Mohan

et al. (2002), Kumar et al. (2014b), Seyedzavar et al. (2015) and Abdullah et al. (2015) also

reported similar results between these traits.

Both the genetic and phenotypic correlations of number of grains per row were positively

and significantly correlated with biological yield in all crosses. These results indicated that as a

part of plant, an increase in grains per row will also increase biological yield. According to

obtained results one can predict an inherited positive selection for both number of grains per row

and biological yield. Our results of positive association between biological yield and number of

grains per row were also in consistence with that reported by Shukla and Mishra (2013).

The association at genetic level between number of grains per row and harvest index was

positive in all crosses, in which only two crosses exhibited significance at genetic level.

Similarly phenotypic correlation of grains per row was positively and significantly correlated

with harvest index in all crosses. Such a positive association indicated that grains per row would

166

significantly affect grain yield as harvest index has grain yield in its numerator. Similar results of

positive association between these characters have been reported by Shukla and Mishra (2013).

5.4.5.7 Grains ear-1

The genetic correlation of grains per cob with hundred grain weight was positively

significant in three crosses. Likewise phenotypic correlation of number of grains per cob with

hundred grain weight was also positive and significant in all crosses. It is obvious from the

results obtained that indirect selection will be practiced for improving grain yield through

hundred grain weight. Similar results of grains per cob and hundred grain weight were also

reported by Shukla and Mishra (2013). In contrast Dhliwayo (2008) reported negative correlation

between number of kernels and kernel weight.

Phenotypic correlation of number of grains per cob with grain yield was positive and

significant in two of the four studied crosses. The genetic correlation of grains per cob was

positive and significant with grain yield in two crosses. Such a positive association indicated that

grains per cob would significantly affect grain yield. Ghassemi-Golezan and Tajbakhsh (2012)

also reported similar results between these traits.

Both the genetic and phenotypic correlations of number of grains per cob were positively

correlated with biological yield in all crosses. The genetic and phenotypic associations of grains

per cob with biological yield were found significant in two and four crosses, respectively. These

results indicated that as a part of plant, an increase in grains per cob ultimately cause an increase

in biological yield. Our results of positive association between grains per cob and biological

yield were also in consistence with that reported by Ghassemi-Golezan and Tajbakhsh (2012).

The genetic association between number of grains per cob and harvest index was

positively significant in two crosses. Similarly phenotypic correlation of grains per cob was

positively and significantly correlated with harvest index in all crosses. Such a positive

association indicated that grains per cob would significantly affect grain yield as mathematical

formula of harvest index has grain yield in its numerator. Similar results of positive association

between these characters have been reported by Ghassemi-Golezan and Tajbakhsh (2012).

5.4.5.8 Hundred grain weight

167

Genetic association of hundred grain weight and grain yield was positive and significant

in three crosses while, one cross exhibited positive non-significant correlation. The phenotypic

correlation of hundred grain weight and grain yield was also positive and significant in all

crosses. Such a positive association is of prime importance for improving grain yield. Our results

of positive association between grain yield and hundred grain weight are supported by

Venugopalet al. (2003), Khayatnezhadet al. (2010), Ghassemi-Golezan and Tajbakhsh (2012),

Kumar et al. (2014b) and Seyedzavar et al. (2015).

The genetic correlation of hundred grain weight with biological yield was positive in all

crosses while, significant level was achieved by three crosses. The phenotypic correlation of

hundred grain weight and biological yield was positive and significant in all crosses. The results

obtained indicated that selection for hundred grain weight will also increase biological yield.

Similar results of positive association between hundred grain weight and biological yield have

been reported by Shukla and Mishra (2013). In contrast to our results Ghassemi-Golezan and

Tajbakhsh (2012) obtained negative and non-significant correlation between grain weight and

biological yield.

Both genetic and phenotypic correlation between hundred grain weight and harvest index

were positive in nature. Genetic association between hundred grain weight and harvest index was

positive and significant in three crosses while, one cross exhibited positive non-significant

correlation. The phenotypic correlation of hundred grain weight and harvest index was also

positive and significant in all crosses. Positive association of hundred grain weight and harvest

index represented that increase in grain weight will increase grain yield, which is a numerator

component in the mathematical formula of harvest index. Our results of positive association

between hundred grain weight and harvest index have been in conformity with Ghassemi-

Golezan and Tajbakhsh (2012).

5.4.5.9 Grain yield

Both genetic and phenotypic correlations of grain yield were positive and significant in

all crosses. An increase in biological yield indicates a robust and vegetatively progressive crop.

In such case the photosynthetic activities will be at maximum level. Results of positive

association between grain yield and biological yield has been reported in literature including

Ghassemi-Golezan and Tajbakhsh (2012), Seyedzavar et al. (2015).

168

Genetic association of grain yield with harvest index was positive and significant in all

crosses. Similarly the phenotypic correlation of grain yield and harvest index was also positive

and significant in four studied crosses. Positive association of grain yield and harvest index

represented that increase in grain yield will increase harvest index as well, because harvest index

has grain yield as numerator component in its calculation. Our results of positive association

between grain yield and harvest index have been similar to those reported by Mousavi et al.

(2013). In contrast to our results, Ghassemi-Golezan and Tajbakhsh (2012) reported negative and

non-significant association between grain yield and harvest index.

5.4.5.10 Biological yield

Both genetic and phenotypic correlations between biological yield and harvest index

were positive and significant in all crosses. Positive association of biological yield and harvest

index represented that increase in biological yield will increase harvest index also. Our results of

positive association between hundred grain weight and harvest index have been reported by

Mousavi et al. (2013). Contrarily negative and significant association between biological yield

and harvest index were reported by Ghassemi-Golezan and Tajbakhsh (2012).

5.4.5.11 Harvest index

Association of harvest index and maturity characters was negative in nature. Ghassemi-

Golezan and Tajbakhsh (2012) also reported similar results of negative association between har

vest index and days to grain filling. Genetic correlation of harvest index was positively

correlated with all grain yield related traits. Similarly phenotypic correlation was also positively

correlated with grain yield characters in all crosses. As harvest index is calculated from grain

yield and biological yield, therefore, in increase in harvest index indicate increase in grain yield.

Similar results of positive association have been reported by Mousavi et al. (2013) and

Ghassemi-Golezan &Tajbakhsh (2012).

5.4.6 Genetic and phenotypic associations among yield and popping characters

Both genetic and phenotypic correlations of fresh ear weight and expansion volume were

negatively correlated with expansion volume in three crosses, the forth cross exhibited negative

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and non-significant association between these traits. Such negative association represented that

an increase in fresh ear weight will reduce expansion volume or popping volume. Similar results

of negative association were also obtained by Dhliwayo (2008). Genetic correlation of fresh ear

weight with percent unpopped grains was positive and non-significant in two crosses, while in

other two crosses that association was negatively non-significant. Likewise, phenotypic

correlation of fresh ear weight and unpopped grains was negative and significant in only one

cross. In two other crosses phenotypic association of unpopped grains and fresh ear weight was

positive and non-significant. The results indicated that when we have maximum fresh ear weight

the unpopped grains will be reduced. Dhliwayo (2008) and also revealed same type of

relationship between ear weight and expansion volume.

Genetic correlation of shelling percentage with expansion volume was negative in three

of the four crosses in which only one cross attained a significant level. Phenotypic correlation of

shelling percentage and expansion volume was also negative and non-significant in two crosses.

Phenotypic correlation of shelling percentage and unpopped grains was positive in all crosses,

only two crosses revealed a significant level. Genetic correlation of shelling percentage and

harvest index was non-significant in all crosses.

Ear diameter was negatively and significantly correlated with expansion volume in one

cross at significant level. Similarly phenotypic correlation between ear diameter and expansion

volume was negative and significantly correlated in three crosses. Our results are corroborated

with that reported by Broccoli and Burak (2004). Ear diameter was negatively and significantly

correlated with unpopped grains at genetic level. Similarly phenotypic correlation of ear

diameter was also negatively and significantly correlated with unpopped grains in two crosses

only. In one cross both genetic and phenotypic associations between ear diameter and unpopped

grains were positively correlated. Our results of positive association ear diameter and expansion

volume are also confirmed by Broccoli and Burak (2004).

Both genetic and phenotypic correlations of ear length were negative and significant with

expansion volume in three of the four studied crosses. This indicated that an increase in ear

length will decrease the expansion volume. Our results of negative associations were also

reported by Broccoli and Burak (2004). Genetic correlation of ear length was negatively and

positively, non-significant with unpopped grains in two crosses each. Similarly phenotypic

correlation of ear length was also negatively and significantly correlated with unpopped grains in

170

one cross only. Similar results of association between ear length and unpopped grains have been

reported by Broccoli and Burak (2004).

Genetic correlation of expansion volume was negatively significant with number of

kernel rows and number of grains per cob while, one cross exhibited negatively significant

association between expansion volume and number of grains per row. Phenotypic correlation of

expansion volume with number of kernel rows, number of grains per row and number of grains

per cob was negatively significant in two of the four crosses. Similar results of negative

association indicated that expansion volume will decrease kernel rows, number of grains per row

and grains per cob. Our results of negative correlation between expansion volume and grains per

row are also corroborated by Jele et al. (2014).

The genetic association of hundred grain weight and expansion volume was negative in

all crosses but was significant in only two crosses. Phenotypic correlation of hundred grain

weight and expansion volume was negatively significant in three crosses. From these results it

can be concluded that selection practiced for hundred grain weight will reduce expansion

volume. Similar results have been cited in literature by Dhliwayo (2008).

Grain yield and biological yield were found negatively correlated with expansion volume

both at genetic and phenotypic level. Genetic correlation of expansion volume with grain yield

was found negatively significant in two crosses, and in three crosses with biological yield.

Phenotypic correlation of grain yield and biological yield with expansion volume was found

negatively significant in four and three crosses, respectively. It is obvious from the results that

selection both for grain and biological yield will affect expansion volume negatively. Our results

of negative association have been reported by Broccoli and Burak (2004), Arnhold et al. (2006)

and Mora & Scapim (2007). Both genetic and phenotypic correlations of percent unpopped

grains with grain yield and biological yield were positive and non-significant in two crosses.

Phenotypic correlation of percent unpopped grains with grain and biological yield was negatively

significant only in one cross. It can be guessed that both traits are controlled by distinct genes.

Genetic correlation of harvest index with expansion volume was negative and significant

in two of the four studied crosses while, phenotypic correlation between these traits was

negatively significant in all crosses. Harvest index and percent unpopped grains were non-

significantly correlated in all crosses. Phenotypic correlation of unpopped grains and harvest

index was negative and significant only in one cross.

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5.4.7 Genetic and phenotypic associations among popping characters

Genetic correlation of expansion volume with percent unpopped grains was positive in

two crosses while, negative in other two crosses. Similarly phenotypic correlation of expansion

volume and unpopped grains was also positive and negative in two crosses each. Positively

significant phenotypic correlation was obtained in one cross only while negative significant

association was also observed in one cross. These results indicated that expansion volume and

percent unpopped grains are negatively correlated in which one can obtain less number of

unpopped grain for high expansion volume. Similar results of negative and significant

association between expansion volume and number of unpopped grains have also been reported

by Jele et al. (2014).

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SUMMARY

This study was conducted at Cereal Crops Research Institute Pirsabak, Nowshera and

The Agriculture University Peshawar, Pakistan. The plant material used in this experiment

comprised a set of four inbred lines of popcorn. Two of the four inbred line were of Bangladeshi

origin and the other two were developed in Cereal Crops Research Institute, Pirsabak. Six

generations including two Parents, F1, F2, BC1 and BC2 were developed in two growing seasons

for each cross by using manual pollination procedure of crossing and selfing. Quantification of

genetic attributes including gene action, heterotic behavior, heritability estimates, phenotypic and

genotypic associations among quantitative parameters are important statistical tools in maize

breeding programs. Parental germplasm used in this study was synthesized from two diverse

popcorn populations. Total genetic materials used in this study included four parents, F1s, F2s,

BC1s and BC2s. These generations were evaluated at two locations i.e. Cereal Crops Research

Institute (CCRI), Pirsabak, Nowshehra and The University of Agriculture, Peshawar. At both

locations the experimental material was replicated thrice in randomized complete block design.

The results indicated that in all crosses dominant gene action was predominantly important in the

inheritance of both days to anthesis and silking. In the studied crosses, additive gene effect was

found negative but significant except, in cross PS-2 × BD-2 for anthesis. The digenic non-allelic

epistasis of additive × dominance and dominance × dominance was considered the major

contributor in the inheritance of days to anthesis in cross PS-1 × BD-2 and PS-2 × BD-2.

Duplicate type of epistasis was observed in cross PS-1 x BD-1 for days to anthesis and silking,

while complementary epistasis was observed in cross PS-1 × BD-2. Similarly for plant and ear

height, dominant gene action was positive and significant in all crosses except, PS-2 × BD-1for

plant height. Duplicate type of epistasis was observed for ear height in two crosses (PS-1 x BD-1

and PS-1 × BD-2), while in cross PS-2 × BD-1 and PS-2 × BD-2 complementary epistasis was

found. It is concluded that crosses with high additive gene effects, could be improved effectively

for studied characters in subsequent generations. For grain yield and related traits dominant gene

action was positively significant in all crosses, indicating that the parental populations could be

effectively utilized in hybrid development programs. Both popping expansion and percent of

unpopped grains was positively and significantly controlled by dominant genes in two of the four

173

crosses, while in the other two crosses dominant gene actions were negative in nature. Broad

sense heritability estimates for grain yield and related attributes were high in all crosses, while

narrow sense heritability estimates for these traits varied from moderate to high levels, which

indicate greater contribution of the genetic portion in the inheritance. Heterotic levels, both mid

parent and better parent were positive and high in magnitude for grain yield and all related

attributes. Both genetic and phenotypic association among yield related attributes were positive

in nature. Based on obtained results it would be wise to use those parents in hybrid crosses which

exhibited both additive and dominant gene actions coupled with high narrow sense heritability

estimates and having strong relationship along with high heterotic levels for most of the grain

yield related traits. Although all the F1 hybrids were superior but PS-2 × BD-2 was outstanding

for grain yield and can therefore be recommended for commercial cultivation.

174

CONCLUSION

Keeping in view our objectives, the following conclusions were drawn from this study. Both

additive and dominance gene effects were observed for 100-grain weight and grain yield, grains

per row, ear diameter. Maturity characters were under control of dominance gene actions and

epistasis of non-allelic digenic interactions. Yield contributing traits were seen under the control

of dominance gene actions. Additive, dominance and epistasis of digenic non-allelic interactions

were equally responsible in controlling the inheritance of plant and ear characters.

High estimates of broad sense heritability were observed for all the traits studied except

harvest index which showed moderate levels of heritability in broad sense. Narrow sense

heritability calculated for most of the traits was in moderate range.

Ear weight, number of grains ear-1, grain yield, grain yield efficiency and biological yield

exhibited high levels of both mid-parent and better parent heterosis. Moderate levels of mid-

parent and better heterosis were observed in leaf area, leaf area index, plant height, ear height,

ear length, number of grains row-1 and 100-grain weight. Low levels of both mid-parent and

better parent heterosis were manifested for days to 50% pollen shedding and silk, days to

maturity, ear diameter, kernel rows ear-1, shelling percentage and harvest index in most crosses.

Among physiological traits, association of days to silking and maturity was negative in

magnitude. Mid silking was positively correlated with days to maturity and similar association

was observed between plant height and ear height. Grain yield and related traits were found

negatively correlated with flowering traits. Similarly grain yield related traits were positively and

significantly associated with each other.

175

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APPENDICES

Appendix 1 Mean square values for days to tasseling, anthesis and silking

SOV DF Days to tasseling Days to anthesis Days to silking

Cross-1 Cross-2 Cross-3 Cross-4 Cross-1 Cross-2 Cross-3 Cross-4 Cross-1 Cross-2 Cross-3 Cross-4

Loc 1 144.00 144.00 144.00 144.00 144.00 144.00 144.00 144.00 144.00 144.00 144.00 144.00

Rep/Loc 4 0.41 0.22 0.24 0.03 0.28 0.11 0.13 0.07 0.42 0.24 0.22 0.05

Gen 5 21.77** 20.19** 18.49** 15.68** 24.44** 21.78** 20.14** 15.15** 23.82** 25.56** 18.68** 17.53**

G × L 5 0.02 ns 0.02 ns 0.01 ns 0.02 ns 0.02 ns 0.01 ns 0.02 ns 0.02 ns 0.03 ns 0.02 ns 0.02 ns 0.02 ns

Error 20 0.17 0.08 0.31 0.25 0.12 0.10 0.26 0.21 0.14 0.10 0.36 0.37

Total 35

** = Significant at 1 % probability level, * = Significant at 5 % probability level, ns = Non-significant

Appendix 2 Mean square values for days to maturity plant height and ear height

SOV DF Days to maturity Plant height Ear height


Loc 1 204.49 204.49 204.49 204.49 1.88 48.77 33.98 26.35 1.78 1.78 0.54 0.22

Rep/Loc 4 1.38 1.48 1.25 1.32 1.60 1.44 1.92 1.61 0.05 1.09 0.25 0.76

Gen 5 21.38** 36.61** 19.80** 27.57** 287.39** 108.14** 120.96** 312.02** 42.87** 25.63** 117.80** 128.38**

G × L 5 0.88* 0.88 ns 0.88* 0.88* 10.01 ns 3.71 ns 27.42** 49.11** 0.51 ns 0.51* 0.13 ns 0.19 ns

Error 20 0.24 0.33 0.25 0.24 3.74 2.98 1.86 3.40 0.48 0.18 0.58 1.04

Total 35


203

Appendix 3 Mean square values fresh ear weight, ear length and ear diameter

SOV DF Fresh ear weight Ear length Ear diameter


Loc 1 38.96 17.08 35.50 28.36 82.36 88.83 96.04 99.83 1.52 1.82 1.03 1.29

Rep/Loc 4 24.59 14.46 9.34 16.19 0.49 0.51 0.50 0.21 0.00 0.01 0.01 0.01

Gen 5 2248.71** 2605.63** 1356.30** 2026.55** 23.22** 39.48** 16.09** 21.50** 0.55** 0.57** 0.19** 0.68**

G × L 5 6.48 ns 5.85 ns 11.11 ns 8.90 ns 0.32 ns 0.42 ns 0.22 ns 0.27 ns 0.03** 0.07** 0.05** 0.10**

Error 20 6.19 6.17 5.86 9.53 0.40 0.55 0.24 0.20 0.01 0.01 0.01 0.01

Total 35


Appendix 4 Mean square values kernel rows ear-1, grains row-1 and grains ear-1

SOV DF Kernel rows ear-1 Grains row-1 Grains ear-1


Loc 1 4.62 4.27 4.34 5.14 16.20 20.33 18.35 21.78 12827.45 14290.21 14125.32 15775.36

Rep/Loc 4 0.16 0.44 0.27 0.91 3.95 7.06 3.69 7.09 751.42 2521.46 536.95 3291.37

Gen 5 15.74** 22.69** 6.65** 10.13** 171.21** 106.14** 86.64** 78.75** 72217.04** 60797.90** 39967.98** 40541.69**

G × L 5 0.11 ns 0.06 ns 0.05 ns 0.05 ns 0.42 ns 0.09 ns 0.19 ns 0.00 ns 366.65 ns 218.67 ns 183.49 ns 166.32 ns

Error 20 0.21 0.23 0.17 0.15 0.78 1.59 4.16 3.02 212.02 442.70 844.12 455.60

Total 35


204

Appendix 5 Mean square values hundred grains weight, grain yield and biological

yield

SOV DF 100-grain weight Grain yield Biological yield


Loc 1 198.81 22.09 95.39 95.39 2356122.67 17875.69 2360217.69 2360217.69 547.56 43.56 547.56 547.56

Rep/Loc 4 1.53 0.21 0.90 0.45 9320.60 2963.23 13973.54 3757.56 7.36 1.31 18.56 14.26

Gen 5 29.88** 19.39** 42.80** 43.43** 3532204.91** 4439761.09** 2218996.41** 3312388.98** 2286.38** 2680.96** 1557.02** 2068.24**

G × L 5 0.02ns 35.36** 18.28** 18.28** 26986.86ns 396160.90** 26935.86** 26935.86** 0.65ns 101.45** 0.65ns 0.65ns

Error 20 1.19 0.53 0.73 0.52 14237.49 10058.84 4545.21 5006.64 8.86 5.38 2.62 6.92

Total 35


Appendix 6 Mean square values harvest index, expansion volume, % unpopped

grains and % shelling

SOV DF Harvest index Expansion volume % unpopped grains % shelling

Cross-1 Cross-2 Cross-3 Cross-4 Cross-1 Cross-2 Cross-3 Cross-4 Cross-1 Cross-2 Cross-3 Cross-4 Cross-1 Cross-2 Cross-3 Cross-4

Loc 1 547.56 43.56 225.00 225.00 414.20 421.73 411.41 417.05 56.88 53.53 57.76 55.75 547.56 41.82 225.00 225.00

Rep/Loc 4 0.92 1.13 1.48 0.89 3.66 2.54 1.49 2.18 2.82 1.85 1.46 2.39 2.72 0.65 1.33 8.81

Gen 5 100.85** 128.69** 47.10** 77.21** 818.43** 1106.42** 149.35** 207.19** 63.56** 199.88** 15.63** 139.16** 105.29** 132.50** 72.82** 67.40**

G × L 5 0.65ns 101.45** 65.16** 65.16** 3.13* 3.10** 1.79ns 1.72* 1.28ns 1.33ns 1.33 ns 1.07ns 0.65 ns 100.67** 65.16** 65.16**

Error 20 0.78 0.69 0.71 0.80 1.09 0.35 0.68 0.52 0.94 0.84 3.00 1.78 3.29 3.33 9.35 2.44

Total 35


205

Appendix 7 Generation means from the combined analysis for days to

tasseling, anthesis and silking evaluated at UOA and

CCRI during summer, 2013.

Generation

Days to 50% tasseling Days to 50% anthesis Days to 50% silking Day to maturity

Cross Cross Cross Cross

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

P1 49.10 49.10 49.53 49.53 52.53 52.53 52.77 52.77 53.60 53.60 54.03 54.70 93.47 93.47 93.33 93.33

P2 53.00 52.17 53.00 52.17 56.57 55.53 56.57 55.53 57.60 57.13 57.60 57.20 98.33 98.67 98.33 98.67

F1 47.40 48.03 47.67 48.10 50.93 51.37 51.00 51.70 52.07 52.37 52.20 52.77 93.33 93.27 93.60 93.87

F2 50.10 51.65 49.55 50.25 53.47 55.35 53.60 53.73 54.75 56.68 54.75 55.85 95.93 98.28 95.85 97.07

BC1 48.50 50.12 49.12 49.48 51.28 53.52 52.63 52.93 52.45 54.93 53.88 54.38 94.12 95.85 94.88 95.35

BC2 49.42 52.65 49.63 52.17 53.00 56.17 53.30 55.65 54.38 57.40 54.60 56.78 95.37 98.18 95.57 97.67

Cross-1 = PS-1 × BD-1, Cross-2 = PS-1 × BD-2, Cross-3 = PS-2 × BD-1, Cross-4

= PS-2 × BD-2

Appendix 8 Generation means from the combined analysis for plant height,

ear height and ear weight evaluated at UOA and CCRI

during summer, 2013.

Generation

Plant height (cm) Ear height (cm) Ear weight (g)

Cross Cross Cross

1 2 3 4 1 2 3 4 1 2 3 4

P1 148.98 148.98 140.00 140.00 72.95 72.95 71.80 71.80 52.67 52.67 77.27 77.27

P2 136.10 139.02 135.55 139.02 63.53 71.40 63.53 71.40 73.90 61.90 73.90 61.90

F1 160.13 150.75 148.17 156.23 68.15 69.92 77.35 78.00 104.47 103.43 113.40 113.03

F2 148.79 147.00 144.77 148.33 65.51 66.77 70.57 70.53 96.12 96.05 99.27 99.17

BC1 150.00 149.78 142.68 151.41 70.58 69.45 71.05 71.18 87.35 90.05 97.97 96.92

BC2 143.39 148.14 141.07 147.16 69.54 70.25 69.58 69.44 91.82 94.18 92.08 92.32


= PS-2 × BD-2

Appendix 9 Generation means from the combined analysis for grain yield,

ear length and ear diameter evaluated at UOA and CCRI

during summer, 2013.

Generation

Grain yield (Kg ha-1) Ear length (cm) Ear diameter (cm)

Cross Cross Cross

1 2 3 4 1 2 3 4 1 2 3 4

P1 2190.27 2190.27 3185.00 3185.00 9.65 9.65 11.02 11.02 2.77 2.77 3.11 3.11

P2 3011.44 2734.76 3011.44 2734.76 11.10 9.23 11.10 9.23 2.95 2.32 2.95 2.32

206

F1 4433.36 4450.48 4540.76 4614.33 15.28 15.98 15.03 14.72 3.44 3.22 3.37 3.28

F2 3806.68 4069.94 3979.92 4361.35 12.34 12.86 13.16 13.05 3.01 2.93 2.86 2.72

BC1 3321.99 3680.31 4280.84 4321.77 13.19 13.73 13.32 12.93 3.12 3.06 3.10 3.00

BC2 3700.77 3871.55 4009.74 3930.41 13.52 13.07 14.38 12.77 3.34 2.96 2.93 2.85


= PS-2 × BD-2

Appendix 10 Generation means from the combined analysis for kernel rows

ear-1, grains row-1 and grains ear-1 evaluated at

UOA and CCRI during summer, 2013.

Generation

Kernel rows ear-1 Grains row-1 Grains ear-1

Cross Cross Cross

1 2 3 4 1 2 3 4 1 2 3 4

P1 10.90 10.90 13.53 13.53 19.25 19.25 27.97 27.97 209.38 209.38 378.87 378.87

P2 12.33 10.80 12.33 10.80 22.75 22.60 22.75 22.60 281.92 243.75 281.92 243.75

F1 15.17 15.30 15.33 14.77 34.60 29.47 34.37 33.60 525.35 451.00 527.40 495.85

F2 13.55 14.12 13.07 12.87 28.33 27.32 27.83 26.07 384.03 387.32 365.85 334.07

BC1 14.22 14.67 14.33 13.62 24.70 27.72 28.05 28.68 352.08 405.80 402.80 391.13

BC2 14.77 14.00 13.25 12.98 28.49 29.83 25.93 26.62 417.48 419.27 342.99 346.33


= PS-2 × BD-2

Appendix 11 Generation means from the combined analysis for 100 grain

weight, days to maturity and % shelling evaluated at UOA

and CCRI during summer, 2013.

Generation

100 grain weight (g) Harvest index % shelling

Cross Cross Cross

1 2 3 4 1 2 3 4 1 2 3 4

P1 13.40 13.40 13.53 13.53 24.30 24.30 30.94 30.94 70.12 70.12 73.68 73.68

P2 15.07 14.93 15.07 14.93 29.44 28.31 29.44 28.31 77.29 81.05 77.29 81.05

F1 19.87 18.67 21.47 21.27 36.61 37.01 36.05 36.70 81.21 83.26 82.83 82.08

F2 16.90 16.40 16.70 16.53 32.77 35.08 33.62 37.02 77.56 77.70 78.33 76.43

BC1 16.43 16.77 16.30 14.90 29.89 32.67 36.57 37.11 79.97 80.42 81.83 80.77

BC2 17.83 15.33 16.43 16.33 32.49 33.67 35.22 34.48 81.71 81.63 82.08 81.24


= PS-2 × BD-2

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Appendix 12 Generation means from the combined analysis for expansion

volume, % unpopped grains and biological yield

evaluated at UOA and CCRI during summer, 2013.

Generation

Expansion volume (cm3 g-1) % unpopped grains Biological yield (g plant-1)

Cross Cross Cross

1 2 3 4 1 2 3 4 1 2 3 4

P1 60.75 60.75 44.46 44.46 14.61 14.61 18.47 18.47 157.67 157.67 180.27 180.27

P2 47.87 51.48 47.87 51.48 20.45 29.23 20.45 29.23 178.90 168.90 178.90 168.90

F1 32.76 23.94 44.98 35.02 15.90 14.97 19.40 16.59 211.90 210.43 220.40 220.03

F2 33.35 34.98 35.41 39.17 23.07 22.58 22.08 23.85 203.12 203.03 206.90 206.17

BC1 32.04 30.35 37.72 47.44 19.47 25.39 22.70 19.33 194.25 197.12 204.80 203.92

BC2 32.42 40.73 36.03 42.18 21.29 20.69 19.98 17.92 199.25 201.18 199.08 199.32


= PS-2 × BD-2

GENETIC ANALYSIS FOR DESIRABLE ATTRIBUTES IN POPCORN …

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