Biparental Mating

Lokesh Gour

DEPARTMENT OF PLANT BREEDING & GENETICS JAWAHARLAL NEHRU KRISHI VISHWA VIDYALAYA

JABALPUR , MADHYA PRADESH (INDIA)

Guided by:-Dr. S.K. Singh, Assistant Professor

IntroductionComstock R.E. and Robinson H.F. (1948,1952)

Commonly F2 generation of pure lines strains are selected and crossed

in definite fashion

The paper of them were been cited in over 105 publications since 1961.

Three deigns of biparental

mating

☺ It involves F2, P1 and P2 generations of a single cross.

☺ It requires 3 crop season for generating material and fourth season for

evaluation

☺ It provides information about additive and dominance components of

genetic variance

☺ It helps in choice of breeding procedure for genetic improvement of

polygenic characters

☺ Analysis is based on second order statistics

Characteristics

Genetical assumptions of biparental cross

Random distribution of genotypes in relation to variation

Random choice of plants for mating

Regular diploid segregation

Absence of epistasis

Absence of linkage

Equal survival of all genotypes

Absence of maternal effects

Lack of multiple allelismAll these assumptions are seldom fulfilled

North Carolina Design 1

North Carolina Design 2

North Carolina Design 3

Biparental Mating

Nested Design&

Hierarchical design

Factorial Design

-

Material used for Biparental Mating

Population Parent 1

Parent 2

F2

Progenies

Half sib (male group)

Full sib (females/males)

Steps of biparental mating

1. Selection of parents Hmm !!!Having

contrasting characters

2. Making Original Cross

F1 seed

P1 P2

3. Growing F1 and F2 Progeny

F2 seed

F1 F1

4. Making Cross in F2

F2 Population now crossing done in definite fashion

F2 Seed

5. Evaluation of Crosses

Replicated Trial For

Observations

Randomly selecting

6. Biometrical Analysis

Computation of Sum of Squares

Genetical Interpretations

Analysis of Variance (ANOVA)

Component of Variances

Crossing Pattern

Nested Design

Males Females

3

4

910

1112

1314

1516

Males Females

1

2

12

34

56

78

Factorial Design

Males Females

F1 F2 F3 F4

M1 X X X X

M2 X X X X

M3 X X X X

M4 X X X x

North Carolina Design 3

Males Females

P1 P2

Set I

M1 X X

M2 X X

M3 X X

M4 X X

Set II

M5 X X

M6 X X

M7 X X

M8 X X

Variances analysed in NCD

The variance among single crosses is divided into

Two fractions

Three fractions

Two fractions

(i) Variance among males - which is equal to ¼ VA(ii) Variance due to females – which is equal to ¼ VA + ¼ VD

(i) Variance due males - equals to ¼ VA(ii) Variance due to females - equals to ¼ VA (iii) Variance due to male x female - equals to ¼ VD

(i) Variance among males - equals to ½ VA(ii) Variance due to male x female - equals to ½ VD

Evaluated Features of NCD Design

1. Each male is mated to a different set of females2. Equal to the number of females used in set x number of

sets3. Total number of crosses is equal to ns4. Presence of maternal effect

1. Each male is mated to the same set of females 2. Total number of cross is equal to mf3. Evaluation is equal to mns4. Presence of maternal effect

1. Each male is mated to the same set of females2. Each sat consists of 2m crosses3. Evaluation is equal to 2ns4. Absence of maternal effect

NCD I

NCD II

NCD III

Resulting Features of NCD Design

1. Maternal effect

NCD I NCD II NCD III

?

2. Area requirement

NCD I

NCD II

NCD III

More

Medium

Least

Use of North Carolina Design

1. Effective in breaking undesirable linkages- mating randomly selected

plants in segregating population

2. Selection of suitable breeding procedure- for polygenic characters

3. Can be used for self as well as cross pollinated species

4. Creation of variability- creating heterozygosity

5. Biparental mating permits evaluation of segregating (F2 or later

generation) population of an individual cross made between two inbred

lines

6. It provides information about two components of genetic variance i.e

additive and dominance variance

7. This technique helps in the selection of suitable breeding procedures

Problems of North Carolina Design

1. Not applicable to the segregating populations of three way, double and multiple

crosses

2. Not permit several segregating crosses simultaneously

3. Does not provide information about the epistatic variance

4. Analysis is difficult as it based on second order statistics

Comparison of biparental designs

S.NO NCD 1 NCD 2 NCD 3

1. Each male is mated to a different group of females

Each male is mated to a same group of females

Each male is mated to both inbred parents of original cross.

2. ‘f’ crosses were obtained ‘mf’ crosses were obtained ‘2m’crosses were obtained

3. Variance is divided into 2 fractions , due to males and due to females.

Variance is divided into 3 fractions, due to males, due to females and due to male x female

Variance is divided into 2 fractions due to male and due to male x female

4. Variance due to male provide an estimate of additive variance (D)

Variance due to male and female provide an esimate of additive variance (D)

Variance due to male provide an estimate of additive variance (D)

5. Variance due to female provide an estimate of additive (D) and dominance variance (H)

Variance due male x female provide an estimate of dominance variance (H)

Variance due to male x female provide an estimate of dominance variance(H)

NCD 1 NCD 2 NCD 3

6. Requires 10 – 12 times more area than design 3.

Requires 2-4 times more area than design 3.

Requires much less area than design 1 and 2.

7. Influenced by the presence of maternal effects.

Influenced by the presence of maternal effects.

Not affected by the presence of maternal effects.

8 Involves F2 Plants in crossing

Involves F2 Plants in crossing

Involves F2, P1 and P2 Plants in crossing

9. This is least powerful design

This is intermediate design This is most powerful design