Egypt. J. Plant Breed. 23(2):289 307 (2019) MAPPING QTL ... · Egypt. J. Plant Breed. 23(2):289–...
Transcript of Egypt. J. Plant Breed. 23(2):289 307 (2019) MAPPING QTL ... · Egypt. J. Plant Breed. 23(2):289–...
Egypt. J. Plant Breed. 23(2):289– 307 (2019)
MAPPING QTL AND EPISTATIC EFFECTS FOR
POWDERY MILDEW, LEAF RUST AND NET BLOTCH
RESISTANCE IN BARLEY M.A. Sayed1, M. Abo Zaid2 and M.B. Ali1
1. Agronomy Dept., Fac. of Agri., Assiut University, Assiut 71526, Egypt
2. Wheat Diseases Research, Plant Pathology Res. Inst., ARC, Giza, Egypt
ABSTRACT Powdery mildew, leaf rust and net blotch are major biotic stresses that affect
both the quality and quantity of the yield of barley. The current research was conducted
at Sids Research Station during 2016/17 and 2017/18 growing seasons in Egypt. We
aimed to identify the quantitative trait loci (QTL) and digenic epistatic interactions
controlling the resistance to the aforementioned diseases in a doubled haploid
population (S42) of barley derived from the cross between the exotic accession of H.
vulgare ssp. spontaneum ‘’ISR42-8’’ and the German spring barley cultivar ‘’Scarlett’’
(H. vulgare ssp. vulgare). Results indicated that the wild parent is more resistant to the
investigated diseases than the cultivated barley; in addition, a favorable transgressive
segregation was detected for all investigated diseases. The QTL analysis showed that the
alleles of the marker bPb-9668 (4H, 145.02 cM) displayed favorable performance of
decreasing powdery mildew severity in the S42 population. In addition, three QTL were
mapped to 2H, 3H and 5H, which associated with the resistance of leaf rust. The alleles
of the three detected QTLs showed favorable performance of decreasing leaf rust
severity in the S42 population by values ranging between -33.54 and -17.73 %. The locus
QTS.S42.3H that located on chromosome 3H, exhibited both marker main effect and
marker × environment interaction. Furthermore, the exotic alleles of this locus
exhibited favorable performance of decreasing net blotch severity in the S42 population.
Moreover, the epistasis analysis revealed nine desirable pairs of epistatic effects
responsible for reducing the severity of the previous mentioned diseases in the S42
population. Our study highlighted that additive × additive epistasis was significant in the
inheritance and breeding for the resistance of the investigated barley diseases.
Key words: Barley, Blumeria graminis hordei, Puccinia hordei , Pyrenophora teres,
QTL analysis.
INTRODUCTION
Today, barley (Hordeum vulgare L.) is a very important cereal crop
worldwide. In this regard, it occupies the fourth rank after wheat, maize,
and rice (FAOSTAT 2018). Diseases that affect the foliage of the barley
plants such as powdery mildew (Blumeria graminis f. sp. hordei), leaf rust
(Puccinia hordei ) and net blotch (Pyrenophora teres Drechs) can severely
reduce the photosynthetic capacity of the plants and may produce toxins.
Furthermore, these diseases often result in yield reduction and excessive
grain protein for malting due to decreased grain size, number of grains per
spike and 1000-grain weight (Mathre 1997 and Ma et al 2004).
Developing disease resistant cultivars is a sustainable way to control
diseases (Mathre 1997 and Bajgain et al 2016). The exotic germplasm
including land races, and wild barley accessions may possess the resistance
to most economically crucial biotic and abiotic stresses (Ullrich et al 1995).
These germplasms can be used to develop new disease-resistant varieties in
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barley breeding programs (Tanksley and Nelson 1996 and Gur and Zamir
2004). In this regard, molecular approaches will increase the economic
significance of breeding for diseases resistance (Parlevliet 1993). One of
the most vital cases for the introduction of favorable wild barley alleles into
elite barley cultivars is the mlo powdery mildew resistance (Von Korff et al
2005).
Numerous studies have extensively applied the QTL analysis in
barley and determined that the aforementioned diseases resistance genes are
present on various barley chromosomes (Ma et al 2004, Friesen et al 2006,
Abu-Qamar et al 2008, Hickey et al 2011, Liu et al 2011 and Li and Zhou
2011). The PI466197 is one of the powdery mildew resistance genes from
H. vulgare ssp. spontaneum, which was identified on the short arm of
chromosome 1H. The other gene for resistance was recognized on the short
arm of chromosome 2H (Teturova et al 2010). In addition, eleven
associated genes conferring resistance to the powdery mildew fungus
Blumeria graminis f.sp. hordei (Bgh) were detected by Spies et al (2012).
Rust-resistant QTL effective at seedling and adult plant stages have been
mapped on chromosome 6H (Marcel et al 2007 and Varshney et al 2007)
and, on the short arm of chromosome 5H by Hickey et al (2011) and Li and
Zahou (2011). The QTL analysis of the doubled haploid (DH) population
that originated from the cross between SM89010 and Q21861 identified
major position for net blotch resistance on chromosome 6H (Friesen et al
2006). This gene was mapped using the simple sequence repeat markers
and was found on a similar location (Cakir et al 2003). Our main objective
in the current study was to identify the beneficial and valuable exotic
alleles, which are vital in the expression of the resistance to powdery
mildew, leaf rust and net blotch in DH population of barley under Egypt
conditions using QTL mapping and epistasis analysis.
MATERIALS AND METHODS
Plant materials
An advanced backcross doubled-haploid mapping population (AB-
DH) containing 301 doubled haploid lines (DHs) derived from crossing
between the exotic accession of H. vulgare ssp. spontaneum ‘’ISR42-8’’
and the German spring barley cultivar ‘’Scarlett’’ (H. vulgare ssp. vulgare
L.) was used to detect QTLs controlling resistance for three diseases i.e.
powdery mildew, leaf rust and net blotch. The population was assigned as
S42 and utilized for QTL analysis and epistasis in current study. The elite
German cultivar Scarlett was used as the recurrent parent whereas the
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exotic one ISR42-8, which was utilized as the donor. Further details about
the development of S42 population and the proportion of exotic parent
genome can be found in von Korff et al (2004).
Molecular characterization of S42 population
A set of 371 doubled haploid lines was genotyped by using DNA
markers comprising 106 SSRs as per Von Korff et al (2004), 255 DArT
according to Sayed et al (2012) and ten gene-specific DNA markers as per
Wang et al (2010) to perform QTL analysis. The genetic map of current
population was drawn by MapChart ver.2.2 (Voorrips 2002).
Pathogen material
The S42 population and its parents were screened in Egypt against
three diseases i.e. powdery mildew (Blumeria graminis f. sp. hordei), leaf
rust ((Puccinia hordei) and net blotch at Sids Research Station during
2016/17 and 2017/2018 growing seasons. Net blotch is a seed-borne and a
foliar disease of barley (Douglas and Gordon 1985) caused by the fungus
Drechslera teres (Sacc.) Shoem. (Syn. Helminthosporium teres Sacc.), the
conidial state of Pyrenophora teres (Died) Drechslera. Each barley
genotype was sown in two rows of 1m length with two replicates using a
randomized complete blocks design. Recommended agricultural barley
practices were applied and the plots were surrounded by spreader area
planted with a mixture of highly susceptible barley varieties to spread
inoculum for infection rows to increase the disease pressure inoculum. For
field inoculation with leaf rust, the spreader plants were sprayed with a mist
of water and dusted with a mixture of urediniospores of the prevalent rust
races mixed with talcum powder at a rate of 1 (spores): 20 (talcum powder).
The inoculation of all barley plants was carried out at booting stage
according to the method of Tervet and Cassell (1951).
Diseases assessment
Diseases assessment of three barley diseases was covered out
through two growing seasons as follows: leaf rust assessment was
preformed when the susceptible check variety of barley expressed 50% rust
severity. The leaf rust severity (%) was recorded based on the modified
Cobb’s scale on a 0-100% scale (Peterson et al. 1948). The powdery
mildew was evaluated using a visual scoring scale with 9 classes. The first
class corresponds to an absence of symptoms, and the ninth indicates to an
attack similar to the ones observed on the susceptible control variety.
The reaction of barley plants to net blotch disease was recorded at
start of flowering stage (Larg 1954), according to double-digit scale 00-99.
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The first digit gives the relative height of disease (Sarri and Prescott 1975)
whereas the second digit shows the disease severity as percentage of leaf
area affected in terms of 0-9, where: 0 = 0% severity, 2 = 20%, 3 = 30%
and so on (Eyal et al 1987).
Analysis of variance
To detect the variation among the tested DH lines and between
ISR42-8 and Scarlett for the investigated traits, the analysis of variance was
conducted using the Statistical Analysis System SAS software (SAS
Institute v. 9.2 2008), PROC GLM procedure. To meet the assumption
underlying the analysis of variance model, the data set of the three diseases
was transformed by calculating the square root of each value after adding 2.
Broad-sense heritability estimation
Heritability in broad-sense (H2) as percentage was estimated as H2=
[δ 2G/(δ2G + δ2
e/r)]×100, where δ2G and δ2
e were the estimates of genetic and
error variances, respectively, derived from the expected mean squares of
the separate analysis for each season. For estimation of broad-sense
heritability (H2) as percentage from combined analysis of variance, the H2
was computed as H2= [δ 2G / (δ2
G + δ 2G×Y/y + δ2
e/yr)]×100, where δ2G,
δ2G×Y and δ2
e were the estimates of genetic, genotype × years interaction
and error variances, respectively. Where, y and r were the number of years
and replications, respectively.
Relative performance of the wild accession RP[Hsp]
The relative performance of the wild parent was calculated using the
following equation:
RP[Hsp] = ([Hsp]- [Hv]) × 100/ [Hv]
where Hsp denotes LS-means of the homozygous wild genotype and Hv
symbolizes LS-means of the elite genotype.
QTL and epistasis analyses
The marker main effect (QTL), its genetic effect and the digenic
epistatic interactions among DNA marker pairs were examined using
stepwise regression approach using QTL mapper software version 1.60
(Wang et al 1999).
RESULTS AND DISCUSSION
Diseases performance and heritability estimates
The analysis of variance means and range between ISR42-8 and
Scarlett for powdery mildew, leaf rust and net blotch diseases compared to
their progeny are shown in Table (1).
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Table 1. Mean squares, coefficient of determination (R2), heritability
estimates (H2), means and range of powdery mildew, leaf
rust and net blotch diseases for ISR42-8 and Scarlett the
compared to their S42 population.
Traits
LS-means ± SE Range
MS R2 H2
S42 population
ISR 42-8 Scarlett ISR 42-8 Scarlett LS-mean ±
SE Range
Powdery
mildew 1.41 ± 0.01 4.21 ± 0.75 1.41-1.41 3.46-6.48 15.73* 84.87 92.77 1.84 ± 0.14 1.41 - 7.21
Leaf rust 1.57 ± 0.14 7.69 ± 0.31 1.41 - 2.00 7.21 - 8.48 74.85** 98.68 99.55 2.95 ± 0.19 1.41 - 9.05
Net blotch 1.41 ± 0.01 7.70 ± 0.16 1.41-1.41 7.21 - 7.87 79.23** 99.79 99.93 3.18 ± 0.16 1.41 - 9.59
*, ** Indicate the significance level at 0.05 and 0.01, respectively.
Highly significant differences between both parents for the
resistance to the three studied diseases were observed in this sudy. The wild
accession ISR 42-8 showed low values of mean disease severity and
recorded 1.41, 1.57 and 1.41 for powdery mildew, leaf rust and net blotch,
respectively. On the other hand, the cultivated parent Scarlett showed high
mean values of the disease severity and recorded 4.21, 7.69 and 7.70,
respectively. This result indicates that the wild parent is more resistant to
the investigated diseases than the cultivated one. Cherif et al (2008)
reported that the mean value of the DH lines was significantly higher than
the mid-parent for net blotch disease studied in three environments.
High estimates of both coefficient of determination and heritability
in broad sense that calculated from both parents were detected for all
investigated diseases. In comparison of their parents, the S42 population
showed wide range of the disease severity of the three diseases. Moreover,
based on extreme values of the S42 population, favorable transgressive
segregation was detected for all investigated diseases, since the DH lines
showing better performance than Scarlett (Table 1 and Figures 1, 2 and 3).
For the S42 population, the analysis of variance showed highly significant
differences among DH lines for all investigated diseases (Table 2),
indicating the suitability of this population to the QTL analysis. Both
seasons differed significantly only in powdery mildew disease case and
there was no interaction between years and DH lines for all investigated
diseases. Furthermore, net blotch disease showed the minimum values of
the coefficient of variation in both seasons and overall ones, while powdery
mildew, exhibited the maximum values of the coefficient of variation.
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Table 2. Separate and combined analysis of variance, coefficient of
determination (R2) and heritability estimates (H2) of powdery
mildew, leaf rust and net blotch diseases in the S42 barley
population.
Source DF
Powdery mildew Leaf rust Net blotch
MS C.V. R2 H2 MS C.V. R2 H2 MS C.V. R2 H2
Separate analysis of 2016/2017 season
Rep 1 1.84* 38.12 83.04 79.52 1.74 24.67 90.04 88.93 4.30** 22.81 95.84 95.65
Lines 300 2.21** 4.84** 11.96**
Error 300 0.45 0.54 0.52
Separate analysis of 2017/2018 season
Rep 1 0.13 20.98 95.97 95.81 0.03 28.06 88.05 86.43 0.03 17.44 97.54 97.48
Lines 300 3.87** 4.99** 12.34**
Error 300 0.16 0.68 0.31
Combined analysis
Year 1 7.38* 30.09 90.86 93.46 0.32 26.40 89.02 92.74 0.40 20.27 96.69 97.88
Year(Rep) 2 0.99 0.89 2.17
Lines 300 5.77** 9.57** 24.14**
Year×Lines 300 0.34 0.65 0.47
Error 600 0.31 0.61 0.42
*, ** Indicate the significance level at 0.05 and 0.01, respectively.
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0 2 4 6 8 10
0
50
100
150
200First season
Scarlett
ISR 42-8
Powdery mildew scalePowdery mildew scale
2 4 6 8
0
50
100
150
200
250
300
Num
ber
of D
H l
ines
Second season
Scarlett
ISR 42-8
Num
ber
of D
H l
ines
Fig. 1. Frequency distribution of population S42 for powdery mildew
severity scale at the first and second season. The vertical lines
represent mean trait value of Scarlett and ISR42-8.
0 2 4 6 8 10
0
20
40
60
80
100
First season
Scarlett
ISR 42-8
Num
ber
of D
H li
nes
0 2 4 6 8 10
0
20
40
60
80
100
Second season
Scarlett
ISR 42-8
Num
ber
of D
H li
nes
Leaf rust scale Leaf rust scale
Fig. 2. Frequency distribution of population S42 for leaf rust severity
scale at the first and second season. The vertical lines represent
mean trait value of Scarlett and ISR42-8.
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0 2 4 6 8 10
0
50
100
150
200 First season
Scarlett
ISR 42-8
Num
ber of D
H lines
Num
ber of D
H lines
Net blotch scale Net blotch scale
0 2 4 6 8 10
0
50
100
150
200 Second season
ScarlettISR 42-8
Fig. 3. Frequency distribution of population S42 for net blotch severity
scale at the first and second season. The vertical lines represent mean
trait value of Scarlett and ISR42-8.
In contrast, net blotch disease exhibited high estimates of broad
sense heritability in both seasons and as combined overall seasons (Table
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2). The frequency distribution of the S42 population for the investigated
diseases in both seasons are shown in Figures 1, 2 and 3. These data
revealed skewed distribution for the three diseases. The large amount of
variation among barley DH lines in their reactions for the disease has also
observed by several researchers such as Von Korff et al (2005) and Cherif
et al (2008). Moreover, the transgressive segregation for both resistance
and susceptibility of the three diseases in separate and combined
environments were reported in several researches in barley (Von Korff et al
2005 and Hickey et al 2011).
Detection of QTL
Altogether, nine putative QTLs and marker × environment
interaction were detected for the investigated diseases in current study.
These QTL were distributed as four QTL detected in the first season and
five QTL were detected for the second season. As main effect overall
seasons, seven QTL were identified for the three diseases (Table 3 and
Figure 4). Among these loci, two QTL were detected for powdery mildew
and mapped on chromosomes 1H and 4H. The locus, QPM.S42.1H
exhibited significant marker main effects and marker × environment
interaction. Based on the relative performance of the exotic allele (RP[Hsp]),
the alleles of the marker bPb-5198 exhibited unfavorable performance of
increasing powdery mildew severity in the S42 population by values 21.88
and 31.73% in the first and second season, respectively. Whereas the
marker locus QPM.S42.4H showed marker × environment interaction and
the alleles of the marker bPb-9668 (4H, 145.02 cM) exhibited favorable
performance of decreasing powdery mildew severity in the S42 population
by values -1.37%. Von Korff et al (2005) detected nine putative QTLs for
powdery mildew covered the whole genome of the same population used in
current study. They found that six QTL out of nine, the exotic parent
contributed the favorable allele to the powdery mildew. Our results are in
accordance with those obtained by Von Korff et al (2005), since the marker
locus bPb-9668 (4H, 145.02 cM) is very near to the DNA region which
detected by Von Korff et al (2005) and also corresponds to the Mlg locus.
Furthermore, Wei et al (1999) identified a race-specific locus Mla on
choromosome 1H encodes 32 different Bgh-resistant genes. Smilar results
were obtained by Teturova et al (2010).
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Table 3. Detected QTLs for powdery mildew, leaf rust and net blotch
diseases in the S42 barley population at two seasons.
1)QTL 2)Season 3)Marker 4)Ch 5)Range 6)F
Value 7)Prob.
8)R2
(%) 9)Effect
10)Hv
effect
11)Hsp
effect 12)RP[Hsp] 13)Additive
Powdery mildew
QPM.S42.1
H 1 bPb-5198 1H
116.46-
123.07 8.94** < 0.003 2.83 M, M×E 1.68 2.05 21.88 0.184
QPM.S42.4
H 1 bPb-9668 4H
145.02-
145.10 7.2** < 0.007 2.28 M×E 1.91 1.88 -1.37 -0.013
QPM.S42.1
H 2 bPb-5198 1H
116.46-
123.07 12.25** < 0.0005 3.93 M, M×E 1.79 2.36 31.73 0.284
Leaf rust
QLR.S42.2
H 2 bPb-1815 2H
146.58-
146.63 9.99** < 0.0017 3.17 M, M×E 3.96 2.82 -28.82 -0.571
QLR.S42.3
H 2 bPb-8419 3H 153.55 8.08** < 0.0048 2.56 M, M×E 3.42 2.81 -17.73 -0.303
QLR.S42.5
H 1 bPb-0837 5H
18.03-
20.0 8.27** < 0.0044 2.69 M, M×E 3.05 2.03 -33.54 -0.511
Net blotch
QNB.S42.3
H 1 MGB410 3H 65-66 6.67* < 0.0104 2.18 M, M×E 4.40 3.06 -30.50 -0.670
QNB.S42.3
H 2 MGB410 3H 65-66 8.97** < 0.0039 2.91 M, M×E 4.43 3.09 -30.26 -0.671
QNB.S42.1
H 2 bPb-2240 1H
123.08 –
125.0 4.19* < 0.029 1.15 M×E 2.99 3.68 22.93 0.343
1) Description of quantitative trait locus. 2) Season. 3) Linked DNA marker
revealing strongest F-value. 4) Chromosome. 5) The QTL region associated to
the significant DNA markers in centiMorgan positions. 6) F-value. 7)
Probability of F test at P < 0.01. 8) Genetic variance explained by DNA
markers. 9) M Marker main effect, M × E marker × environment interaction.
10) Trait value of homozygous cultivated genotypes (Hv). 11) Trait value of
homozygous exotic genotypes (Hsp). 12) Relative performance of the
homozygous exotic allele, RP [Hsp] and 13) The additive effect is half the
difference between the phenotypic means of the homozygous elite and exotic
marker genotypes. *, ** Indicate the significance level at 0.05 and 0.01,
respectively
299
MGB4020.0bPb-28624.3bPb-63184.8bPb-04057.2bPb-62387.5bPb-377610.5bPb-960811.5bPb-713711.7bPb-131813.1GMS2114.0S5370718.0GBM100719.0bPb-730619.1bPb-441536.6Mla1238.5GBM104239.0bPb-321740.5bPb-048255.4bPb-160455.8bPb-971758.7bPb-453160.2bPb-360562.2HVALAAT62.5HVM2062.6Bmag21162.7MGB32562.9Bmag14963.2Bmag10563.5HVGLUEND64.0bPb-529064.9bPb-533467.9bPb-533976.8Bmac3280.0bPb-760982.1bPb-789986.3bPb-691194.9bPb-121395.0bPb-136695.1bPb-4515106.2HvFT3115.0HVABAIP116.0bPb-5014bPb-5198
116.5
bPb-2240123.1GBM1061125.0bPb-1882133.1bPb-6200133.7GBMS12134.0bPb-1940135.1bPb-6502139.6bPb-8112140.9bPb-0589141.2bPb-5201141.3bPb-0699144.2bPb-1487147.3GBMS143162.0
QP
M.S
42
.1H
QN
B.S
42
.1H
1H
x0.0bPb-42853.5bPb-51915.0bPb-96815.3bPb-64667.6bPb-975714.4bPb-8399bPb-0003
25.7
bPb-612826.2HVM3626.5GBM103527.0bPb-829227.1bPb-305030.2bPb-482135.8bPb-803839.0PpdH141.1GBM105242.0bPb-426144.8bPb-790647.4bPb-223060.4MGB39164.0HvGOGAT65.0HvFT466.0bPb-222567.3bPb-107270.0bPb-305670.8bPb-877977.4EBmac68480.0GMS381.0bPb-608881.7bPb-404082.1bPb-975482.8bPb-089087.0HvNAM290.0HVTUB92.0Bmag38197.0Bmag12598.0bPb-814398.2bPb-7991101.3bPb-1926102.1bPb-3563102.4bPb-4577108.7bPb-8464138.2bPb-7816139.0bPb-4768139.6bPb-1066139.8GBM1016140.0HVM54143.0EBmac415144.0HvCNX1145.0bPb-1815bPb-4092
146.6
bPb-8255149.4MGB334150.0bPb-5558150.1bPb-0299157.1bPb-3102160.4bPb-8698161.1bPb-7723163.3
QL
R.S
42
.2H
2H
x0.0bPb-44721.5bPb-95836.0bPb-36897.6bPb-30259.9bPb-994510.2bPb-107720.0HVLTPPB25.0EBmac70530.0HVITR135.0bPb-798950.4bPb-793851.4bPb-299351.6bPb-727353.2bPb-0158bPb-9746
54.8
bPb-634755.6HvGI63.0HvFT264.0MGB41065.0Bmag60366.0bPb-204066.5bPb-5771bPb-0094
69.3
bPb-828369.6bPb-501269.8bPb-832170.4HVM3383.0bPb-035384.4bPb-168187.8GMS116100.0HVM60100.1GBM1043100.7bPb-3278100.8bPb-4616105.9bPb-4209111.7bPb-1579115.5bPb-9110118.7bPb-1609140.3bPb-9111141.9bPb-4564142.8bPb-1481145.4bPb-5129146.8bPb-2420147.0bPb-6228bPb-8557
147.9
bPb-7827148.3bPb-0789148.8bPb-2888149.8HV13GEIII150.0HVM62151.0MGB358152.0bPb-8419153.5bPb-7164158.0bPb-1411160.2bPb-0361165.5bPb-5864170.7bPb-4628175.2Bmac29176.0bPb-7247178.5bPb-8962178.6bPb-7724179.5bPb-0136181.3
QL
R.S
42
.3H
QN
B.S
42
.3H
3H
x0.0
bPb-930412.7bPb-693813.0HVM4014.0bPb-146914.6bPb-469917.3HVOLE21.0HVB23D25.0HVKNOX331.0
HVPAZXG44.0
HVM1355.0GMS8957.0bPb-1408bPb-8437
60.0
bPb-664060.5bPb-351267.9bPb-421669.7bPb-548072.2bPb-798772.3EBmac77580.0bPb-801386.7bPb-870193.6MGB39695.0bPb-373996.3bPb-771996.8
bPb-9859123.2TACMD125.0Mlo127.5EBmac701130.0EBmac635131.0EBmac679132.0EBmac788138.0GBM1015140.0VrnH2140.2HVJASIP141.0HVM67141.1bPb-9820142.1bPb-9668145.0bPb-5265145.1HDAMYB146.0bPb-3717148.6
QP
M.S
42
.4H
4H
x0.0
bPb-083718.0BMS220.0Bmac16324.0
MGB38433.0bPb-932734.7bPb-636336.1
bPb-413543.5
bPb-728758.4Bmag33765.0Bmag35768.0bPb-961870.7bPb-776371.0bPb-785273.6bPb-667681.4bPb-237882.9bPb-2497bPb-4721
84.2
Bmag22387.0bPb-6967MGB338
95.0
bPb-124199.9bPb-5596101.3bPb-6126106.9
VrnH1125.1GMS61126.0bPb-4758126.5bPb-0071126.8bPb-3910133.5bPb-3945136.2bPb-5845139.0MGB318150.0AF043094A156.0bPb-6367157.4bPb-5238159.4bPb-0171159.9Bmag222162.0MGB357165.0bPb-3138166.6bPb-1719173.7bPb-0799174.0bPb-8754183.0bPb-1217184.4bPb-9660187.0
QL
R.S
42
.5H
5H
Fig. 4. Genetic map of the detected QTL for powdery mildew, leaf rust
and net blotch in barley. Linkage map was drawn using
MapChart ver.2.2 where the markers and genetic positions are
presented on right and left of the chromosome, respectively.
300
For leaf rust disease, the QTL analysis identified three QTL and
mapped to 2H, 3H and 5H. All detected QTL showed marker main effect
and marker × environment interaction. The alleles of the three detected
QTL exhibited favorable performance of decreasing leaf rust severity in the
S42 population by values ranging between -33.54and -17.73%. These QTLs
showed negative additive effects (Table 3). The strongest QTL was QLR.
S42. 2H (146.58 cM) and explained 3.17% of the genetic variance. This
DNA region maps to the same bin as a gene, which encodes chalcone
synthase, the chalcone synthase is responsible of the defense response
genes and was accumulated in barley leaves upon inoculation with powdery
mildew (Christensen et al 1998 and Karakousis et al 2003). Von Korff et al
(2005) identified six putative QTL for leaf rust resistance in the S42
population. One of them (EBmac415) was located on chromosome 2H (146
cM) and led to reduce the severity of leaf rust in the S42 population.
Furthermore, the detected QTL QLR.S42.3H which located on 3H (153.55
cM) was corresponding to the marker HVM62 (3H, 155 cM) which was
identified by Vvon Korff et al (2005). Several race-specific resistance
genes for leaf rust were reported in barley (Franckowiak et al 1997), some
of these genes were identified in H. vulgare ssp. Spontaneum. Many studies
detected resistance genes to leaf rust in barley on chromosomes 2H and 3H
such as Feuerstein et al (1990), who detected two resistance genes, Rph10
and Rph11, on chromosomes 3H and 6H, and Ivandic et al (1998) who
mapped Rph16 at the centromeric region of 2H. Hickey et al (2011)
detected genomic regions associated to leaf rust resistance in barley using
DArT markers. Remarkably, one of the important result of current study
that the marker locus bPb-0837 which was mapped on 5H was the same
marker which was detected by Hickey et al (2011) for leaf rust resistance.
Sandhu et al (2016) characterized some international barley nurseries in
Australia for leaf rust resistance and detected the resistance genes.
Barley net form net blotch is a significant foliar malady of barley
(Ilyas et al 2014). Two QTL were detected for net blotch disease (Table 3).
The locus QTS.S42.3H that located on chromosome 3H, showed marker
main effect and marker × environment interaction. In addition, the exotic
alleles of this locus exhibited favorable performance of decreasing net
blotch severity in the S42 population by values -30.50 and -30.26% in the
first and second season, respectively. The other locus, QTS.S42.1H, which
was mapped on chromosome 1H showed marker × environment interaction.
The exotic alleles of this locus exhibited unfavorable performance of
301
increasing net blotch severity in the S42 population by value of 22.93%. In
addition, the exotic alleles explain small percentage (1.15%) of the genetic
variance. Tajinder et al (2012) identified one spot blotch QTL on
chromosome 1H. In addition, the chromosome 6H has been reported to
contain multiple independent resistance genes against this disease (Friesen
et al 2006, Abu Qamar et al 2008 and Liu et al 2012).
Detection of Epistasis
Using the doubled haploid lines can provide valuable information
on additive and epistatic interaction effects that are maximized, since all
polymorphisms can be explained by dominant and co-dominant allele
expression (Choo et al 1985). Altogether, 18 pairs of epistatic QTLs as
additive-by-additive effects were identified for three investigated diseases
in both seasons in the S42 population (Table 4). Among the QTL detected,
only the marker locus bPb-2240 (1H) was involved in epistatic interaction
effects. The result indicates that several loci that involved in the epistatic
interactions may not have significant effects for the investigated diseases
and may affect the trait expression by epistatic interactions with other loci.
Results revealed seven pairs of epistatic QTLs (one for the first
season and six for the second season) were associated significantly with
powdery mildew and covered the whole genome except chromosome 5H.
Among these positions, two pairs of epistatic effects reduced powdery
mildew severity in the S42 population. The most desirable pair of epistatic
QTL for reducing powdery mildew severity was (bPb-3278* bPb-0432)
and mapped to chromosomes 3H (100.76 cM) and 6H (91.99 cM) and had
the highest F value and accounted for 5.21% of genetic variation (Table 4).
At this locus, the BC2DH lines carrying the Hsp/Hsp genotype were
resistant to the powdery mildew with an average of 1.63 of disease scale
compared to the other the allelic combinations. Using scaling test, Fazeli et
al (2013) indicated the importance role of additive × additive effect in
controlling of powdery mildew resistance in barley.
302
Table 4. Estimation of LS-means of 17 pairs of digenic interactions and
epistatic effects (additive × additive) for powdery mildew,
leaf rust and net blotch diseases in each season.
Marker 1 Marker 2 F Value Prob. F R2
LS means of digenic interactions
Name Chr. Pos. Name Chr. Pos. Hv/Hv Hv/Hsp Hsp/Hv Hsp/Hsp
Powdery mildew, season 1
bPb-1366 1H 95.08 bPb-3512 4H 67.92 10.25** <
0.0015 3.15 1.68 1.76 1.72 1.79
Powdery mildew, season 2
MGB391 2H 64.00 bPb-7247 3H 178.50 9.57** <
0.0022 2.91 1.83 2.01 2.01 2.08
bPb-7609 1H 82.15 HVPAZXG 4H 44.00 9.67** <
0.0021 2.59 1.69 2.22 1.76 2.29
HvCO1 7H 82.00 bPb-8690 7H 87.39 15.72** <
0.0001 4.21 1.86 1.96 1.87 1.97
S53707 1H 18.00 HVM60 3H 100.10 8.41** < 0.004 2.25 1.93 1.92 1.93 1.92
bPb-3278 3H 100.76 bPb-0432 6H 91.99 19.47** <
0.0001 5.21 2.04 1.76 1.92 1.63
bPb-5201 1H 141.29 bPb-3895 6H 98.71 14.56** <
0.0002 3.9 1.84 1.89 2.08 2.12
Leaf rust, season 1
bPb-3217 1H 40.53 HVPAZXG 4H 44.00 9.73** < 0.002 2.74 3.17 3.33 2.49 2.65
bPb-2230 2H 60.45 bPb-4216 4H 69.66 5.02* < 0.025 1.42 3.04 2.73 2.67 2.36
bPb-1815 2H 146.58 HVPAZXG 4H 44.00 22.00** <
0.0001 6.2 2.81 3.05 3.35 3.63
bPb-9681 2H 5.27 AF043094A 5H 156.00 10.48** <
0.0014 2.95 2.99 2.69 2.91 2.61
HVKNOX3 4H 31.00 HVCHI26A 7H 159.20 16.17** <
0.0001 4.56 3.00 2.48 3.01 2.48
Leaf rust, season 2
bPb-9681 2H 5.27 AF043094A 5H 156.00 12.09** <
0.0012 2.97 3.01 2.47 2.66 2.32
Net blotch, season 1
bPb-2240 1H 123.09 bPb-9304 4H 12.67 12.74** <
0.0004 3.94 3.13 4.09 3.44 4.40
Bmag357 5H 68.00 bPb-6967 5H 94.96 9.48** <
0.0023 2.93 3.10 3.07 3.42 3.39
Net blotch, season 2
bPb-1604 1H 55.77 bPb-9820 4H 142.09 6.89* <
0.0107 2.06 3.20 4.26 3.49 4.55
bPb-6727 6H 134.08 bPb-6706 7H 58.17 10.64** <
0.0017 3.18 3.73 2.78 2.60 1.65
EBmac635 4H 131.00 HvCO1 7H 82.00 8.41** <
0.0051 2.52 3.39 2.98 3.11 2.70
*, ** indicate the significance level at 0.05 and 0.01, respectively to declare the
putative epistatic QTL positions.
303
For leaf rust, the analysis revealed six pairs of epistatic QTL (five
for the first season and one for the second season) were associated
significantly with leaf rust disease. These QTL were located on
chromosomes 1H, 2H, 4H, 5H and 7H. Among these locations, five pairs of
epistatic effects reduced leaf rust severity in the S42 population. The most
desirable pair of epistatic QTL for reducing leaf rust severity was
(HVKNOX3 × HVCHI26A) located on chromosomes 4H (31.00 cM) and
7H (159.20 cM) and had the highest F value and accounted for 4.56% of
genetic variation (Table 4). At this locus, the BC2DH lines carrying the
Hsp/Hsp genotype were resistant to the leaf rust with an average of 2.48 of
disease scale compared to the other the allelic combinations. In addition,
the epistatic pair bPb-9681 × AF043094A was observed in both seasons
and led to reducing leaf rust severity and had high F value and R2. Qi et al
(1998) detected an additive effect QTL and a significant interaction
between two QTL, i.e. Rphq1 and Rphq2.
For net blotch, the analysis revealed five pairs of epistatic QTL (two
for the first season and three for the second season) were associated
significantly with net blotch disease. These QTL were mapped on
chromosomes 1H, 4H, 5H, 6H and 7H. Among these loci, two pairs of
epistatic effects reduced net blotch severity in the S42 population. The most
favorable pair of epistatic QTL for reducing leaf rust severity was (bPb-
6727 × bPb-6706) and located on chromosomes 6H (134.08 cM) and 7H
(58.17 cM) and had the highest F value and accounted for 3.18% of genetic
variation (Table 4). At this locus, the BC2DH lines carrying the Hsp/Hsp
genotype were resistant to the net blotch with an average of 1.65 of disease
scale compared to the other the allelic combinations. Cherif et al (2008)
concluded that net blotch resistance is quantitative and additive × additive
epistasic effect plays an important in the inheritance of net blotch.
component of this resistance.
In conclusion, our results revealed that five favorable QTLs were
responsible of decreasing powdery mildew, leaf rust and net blotch severity
in the S42 population due to the presence of the exotic alleles of the wild
parent ISR 42-8. These multiple disease resistance regions were considered
as prime candidates for further investigation and validation of their broad
resistance. Further, the epistasis analysis revealed nine desirable pairs of
epistatic effects of reducing the severity of the abovementioned diseases in
the S42 population. Since, the DHs lines carrying the Hsp/Hsp genotype
were resistant to these diseases. Thus, the study highlighted that additive ×
304
additive epistasis was significant in the inheritance and breeding for the
resistance of the investigated diseases in barley.
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التفوقي للمقاومة ألمراض البياض الدقيقي, تحليل مواقع الصفات الكمية والتأثير صدأ األوراق و التبقع الشبكي في الشعير
1, محمد بدري محمد علي2, محمد أبوزيد1محمد عبدالعزيز عبدالحليم سيد قسم المحاصيل، كلية الزراعة، جامعة أسيوط . 1
بات، مركز البحوث الزراعية، الجيزةراض القمح، معهد أمراض النأم قسم. 2
, والتبقع الشبكي من اإلجهادات الحيوية الرئيسية التي تؤثر على يعتبر البياض الدقيقي, وصدأ األوراقو 2016/17جودة وكمية محصول الشعير. تم إجراء هذا البحث في محطة بحوث سدس خالل موسمي
( ودراسة التأثيرات التفاعلية QTLان الهدف من البحث, تحديد مواقع الصفات الكمّية )في مصر. ك 2017/18في المقاومة لألمراض الثالث في عشيرة من الشعير )مضاعفة العدد الكروموسومي األحادي(. المضيفة المتحكمة
وصنف ’’ H. vulgare ssp. spontaneum’’ ISR42-8هذه العشيرة ناتجة من التهجين بين األب البري كثر مقاومة النتائج إلى أن األب البري أ أشارت H. Vulgare ssp vulgare’’ Scarlett’’.شعير ألماني منزرع
لألمراض الثالثة من الشعير المنزرع. كما لوحظ وجود انعزاالت فائقة الحدود لمقاومة األمراض المذكورة. كشف أظهرت سنتيمورجانH4 (145.02 )روموسوم الك علي bPb-9668 أن أليالت الواسم الوراثي QTLتحليل
. باإلضافة إلى ذلك , تم تحديد ثالثة S42عشيرة أداء مرغوبًا لخفض شدة االصابة بمرض البياض الدقيقي في الQTL مواقع وراثية على الكروموسوماتH2 ,H3 ,H5 والتي ترتبط بمقاومة صدأ األوراق. أظهرت أليالت الـ ,QTL لتقليل شدة االصابة بصدأ األوراق في العشيرة ة أداًء مرغوبًا الثالثة المكتشفS42 بقيم تراوحت بين-
كال من التأثير الرئيسي H3الموجود على الكروموسوم QTS.S42.3Hكما أظهر الموقع ٪.17.73-و 33.54والتأثير التفاعلي بين الواسم والبيئة. عالوة على ذلك, أظهرت األليالت البرية لهذا الموقع أداًء مواتيًا لخفض شدة
عالت األليلية المرغوب فيها و تسعة أزواج من التفا Epistasis. كشف تحليل S42التبقع الشبكي في العشيرة ألصابة باألمراض المذكورة أعاله في العشيرة موضع الدراسة. تسلط هذه الدراسة المسؤولة عن الحد من شدة ا
المضيف في الوراثة والتربية للمقاومة لألمراض الثالثة التي تم دراستها في -الضوء على أهمية التفاعل المضيف هذه التجربة في الشعير.
(2019) 307 -289( : 2)23لمجلة المصرية لتربية النبات ا