Phylogenetic Relationship to Study the Ploidy Status and Resistance to Karnal Bunt in Indian Wheat Cultivars Using RAPD Technique
Anil K. Gupta,
Eyasu Tekie Teshale,
Vijay K. Khanna
Tetraploid and hexaploid Indian wheat accessions were
analyzed for genetic polymorphism using RAPD-PCR in order to study the
gene rearrangements during polyploidization. Ten RAPD primers were employed
to establish the evolutionary relationship amongst 10 tetraploid and 17
hexaploid wheat accessions. Tetraploid accession showed 75.7% polymorphism
whereas hexaploid accessions showed 65.3% polymorphism. The Genetic Distance
(GD) value of the tetraploid accessions ranged 0.400 to 0.966 was significantly
higher than the GD values of the hexaploid accessions (0.630 to 0.952).
RAPD primers clearly categorized tetraploid to hexaploid accessions in
different groups according to similarity coefficient. Nearly all tetraploid
accessions were grouped together. The same set of primers was also able
enough to establish polymorphism amongst 20 Karnal bunt susceptible and
resistant tetra and hexaploid wheat varieties. Like tetraploid accessions,
susceptible varieties showed low genetic relationship. Some of the primers
gave a distinct RAPD pattern for the discrimination between resistant
and susceptible varieties but none of the primer was able to discriminate
the resistant, susceptible and moderately susceptible wheat varieties.
The phylogenetic polymorphism according to ploidy level and resistant
status to KB is interpreted as the result of alteration in gene loci during
polyploidization, genetic drift during inter and intra specific breeding
and/or selection pressure for improved fertility.
Wheat (Triticum spp.) is the world`s leading cereal grain
and the most important food crop. Its diverse uses, nutritive content
and storage qualities have made wheat as a staple food for more than one
third of the world population. It has been cultivated in southwestern
Asia, its geographic centre of origin, for more than 10,000 years. Related
wild species still grow in Lebanon, Syria, Northern Israel, Iraq and Eastern
Turkey. Man began breeding wheat in the early 1800s. Since then, there
have been improvements in yield and grain quality, modifications in the
plant architecture and increased resistance to drought, lodging, insect
pests and pathogens (Poehlman and Sleper, 1995). Polyploidization has
played a major role in higher plant evolution. Over the last century,
important information has been generated on many aspects of population
biology, speciation and polyploid genetics (Hancock, 2005). Plant evolutionary
theory has been greatly enriched by studies on crop species and a majority
of angiosperms (70-80%) (Masterson, 1994) including some of the most important
crops (wheat, maize, potato, cotton, sugarcane) are polyploid. Polyploidization
allows novel genetic interactions and its role in plant genome evolution
is highly relevant (Wendel, 2000). The genetic origin of wheat is a classic
example of how closely related species combine in nature to form a polyploid
The species of Triticum are grouped into three ploidy classes;
diploid (2n = 14), tetraploid (2n = 28) and hexaploid (2n = 42). Currently,
11 diploid, 12 tetraploid and 6 hexaploid species of Triticum are
recognized. Only two species of Triticum are commercially important,
the tetraploid T. turgidum and the hexaploid T. aestivum.
T. turgidum evolved as an alloploid combing genomes from the diploid
species, T. uratu thum ex gandil (AA) and an unknown species (BB)
related to Aegilops speltoides (SS). Bread wheat (T. aestivum)
is hexaploid (2n = 42) with three (A, B and D) sub genome each containing
seven pair of homologous chromosomes. Hexaploid wheat, which arose approximately
10,000 years ago (Feldman et al., 1995) is a classical example
of allopolyploidization. It originated from the hybridization of tetraploid
wheat T. turgidum (AABB) and Aegilops tauschii (DD) (Kihara,
1944; McFadden and Sears, 1946; Poehlman and Sleper, 1995; Friebe and
Gill, 1996). Recent studies have shown that allopolyploidization triggers
rapid genome changes (revolutionary changes) through the instantaneous
generation of a variety of cardinal genetic and epigenetic alterations
and the allopolyploid condition also facilitates sporadic genomic changes
during the life of the species (evolutionary changes) that are not attainable
at the diploid level. These phenomena, emphasizing the plasticity of the
genome with regards to both structure and function, might improve the
adaptability of the newly formed allopolyploids and facilitate their rapid
and successful establishment in nature (Feldman and Levy, 2005).
Compared with other allopolyploids, wheat is considered to be a young
polyploid. The identity, organization and the evolution of different genomes
constituting wheat have been intensively studied in last decades (Flavell
et al., 1987; Kimber and Sears, 1987; Feldman et al., 1995;
Feldman and Levy, 2005). These studies were performed using a number of
techniques such as cytogenetics, protein and isozyme electrophoresis,
comparative mapping and molecular markers or DNA sequence comparisons.
In addition, several tools that allow quick and efficient chromosomal
localization in hexaploid wheat were developed, including a series of
aneuploid lines (deletion, addition or substitution lines) of the variety
Chinese spring (Sears, 1966; Endo and Gill, 1996). These features, combined
with the possibility of producing synthetic polyploids (Feldman et
al., 1997), make wheat a model plant to study the mechanism of evolution
in polyploid species.
Polyploidization events can have many consequences on genome evolution,
particularly on gene expression and gene organization (Wendel, 2000).
In wheat, studies with synthetic polyploids have indicated that genome
reorganization probably occurs rapidly after the polyploidization event
and the coding and non-coding regions might be differentially affected
(Liu et al., 1998a, b). So far, few studies have been performed
to follow the rate and type of changes of individual loci after polyploid
formation. The timing and rate of genomic variation induced by allopolyploidization
in the intergeneric wheat-rye (Triticum spp.- Secale cereale
L.) hybrid triticale (x Triticosecale Wittmack) was studied using Amplified
Fragment Length Polymorphism (AFLP) analyses (Ma and Gustafson, 2006).
Their result showed that allopolyploidization induced genome sequence
variation in triticale and a great degree of the genome variation occurred
immediately following wide hybridization. The data suggested that the
cytoplasm and the degree of relationship between parental genomes were
key factors in determining the direction, amount, timing and rate of genomic
sequence variation occurring during intergeneric allopolyploidization.
Seventy-two Xinjiang Triticum and Triticum polonicum accessions
were subjected to AFLP analyses to discuss the origin of Triticum
petropavlovskyi by Akond et al. (2007) and findings of their
study reduced the probability of an independent allopolyploidization event
in the origin of T. petropavlovskyi and indicated a greater degree
of gene flow between T. aestivum and T. polonicum leading
to T. petropavlovskyi.
A key question in studying gene evolution arises whether the genes have
evolved independently or there was a concerted evolution (Doyle and Gaut,
2000). The identification of resistant genes in several wheat cultivars,
having different ploidy levels, will provide an insight to understand
the impact of polyploidization in altering these resistant loci. Demeke
et al. (1996) have characterized the Bt-10 gene in the resistant
European wheat lines. The STS markers J13, Gb and J09 were used for screening
wheat accessions for leaf rust resistance genes (Tyryshkin et al.,
2006) and a leaf rust resistance gene Lr19 on the chromosome 7DL of wheat
was tagged with random amplified polymorphic DNA (RAPD) (Gupta et al.,
2006). RAPD based gene loci allow us to analyze the evolutionary relationship
between wheat genotypes of different ploidy and identify resistance of
genotypes against Karnal Bunt (KB).
Knowledge of genetic diversity and relationship among a set of germplasm
and the potential merits of genetic diversity would be beneficial to all
the phases of crop improvement. Assessment of genetic diversity of the
elite germplasm have been sought and used by plant breeding for numerous
reasons e.g., genetic relationships, parent selection, germplasm management
and protection among others (Lee, 1995). To date, no information is available
on variation in Indian tetraploid and hexaploid wheat genotypes at the
molecular level. There is an urgent need that the germplasm should be
well maintained and efforts should be made to organize research programs
on germplasm characterization, utilization and enhancement including molecular
characterization. The investigation presented here, therefore, was undertaken
with the objective to evaluate and compare genetic diversity between and
within tetraploid and hexaploid wheat genotypes.
MATERIALS AND METHODS
Collection of wheat lines: Seventeen accessions of bread wheat
(Triticum aestivum) and ten of durum wheat (T. durum) (Table
1), used to study genetic diversity, were
||The place of collection of the accessions used to study
of genetic divergence during polyploidization
collected from National Bureau of Plant Genetic Resources (NBPGR), New
Delhi, India. Eighteen varieties of bread wheat (T. aestivum) and
two varieties of durum wheat (T. durum) were collected from CRC,
Pantnagar and Department of Plant Breeding, Punjab Agricultural University,
Ludhiana, India for the study of Karnal bunt resistance RAPD loci. Out
of these 20 genotypes of hexaploid and tetraploid wheat, 6 were highly
susceptible to KB, 10 were moderately susceptible and 4 were resistant
to KB (Table 2).
Genomic DNA isolation: Genomic DNA of all 47 wheat samples (27
accessions and 20 varieties of wheat) was isolated using SDS method (Dellaporta
et al., 1983). Isolated genomic DNA was purified (Sambrook et
al., 1989) and quantified by both UV spectrophotometer (DU640B spectrophotometer,
Beckman) and DyNA Quant 2000 flourimeter (Hoefer).
Polymerase chain reaction (RAPD): Ten decamer primers (Table
3) were selected (Teshale et al., 2003) for the PCR (RAPD)
which was carried out in 25 μL of a reaction mixture containing 20
ng of genomic DNA, 200 μM each dNTPs, 1.25 U Taq DNA polymerase,
10 mM Tris-Cl, 1.5 mM MgCl2, 50 mM KCl, 0.01% gelatin and 0.2
μM random decamer primer. The PCR amplification was conducted in
Biometra thermal cycler programmed as initial denaturation at 94 °C
for 5 min; remaining 45 cycles with 94 °C denaturation for 1 min.,
37 °C annealing for 2 min and 72 °C extension for 2 min. Final
||Wheat varieties used for the study of RAPD loci of the
KB resistance gene
||Arbitrary decamers primary used for divergence study
given at 72 °C for 5 min. PCR amplified products were analyzed on
1.5% agarose gel in TAE (pH 8.0) buffer (Sambrook et al., 1989).
Data analysis: All gels were scored twice, independently and manually.
Presence of bands has been indicated by 1 and absence by 0. All monomorphic
bands were also scored and included in the analysis. Presence or absence
of unique and shared polymorphic as well as monomorphic products was used
to generate a similarity coefficient. These data matrices were submitted
to NTSYS-PC (Numerical Taxonomy and Multivariate system programme) (Rohlf,
1992) and were analyzed using SIMUQAL program to generate Jaccard`s similarity
coefficients (Sokal and Sneath, 1963). These similarity coefficients were
used to construct dendrogram using the unweighted pair-group method with
arithmetic average (UPGMA) using NTSYS programme.
The genomic DNA band of all the accessions and wheat varieties were
intact and showed good quality that was preferable for RAPD analysis as
the OD260/280 ratio of purified genomic DNA was approximately
1.8 for each sample and the concentration ranged between 880 to 1585 ng
μL-1. The template DNA concentration for the optimum amplification
was found to be 20 ng per 25 μL reaction for all the primers. The
optimized amplification protocol for all 10 primers was the same.
RAPD based study of genetic divergence during polyploidization: The
numbers of RAPD loci generated by ten primers with 27 wheat accessions
(genotypes) were 103 (Table 4). Out of 103 loci, 82 (79.6%)
were polymorphic for one or more genotypes and remaining 21 (20.4%) were
monomorphic for all the genotypes. The size of amplified products ranged
between 0.3 to 3.0 kb. All the ten primers used, were informative and
gave polymorphic bands for one or more genotypes. The results gave an
average of 8.2 polymorphic and 2.1 monomorphic bands per primer. Primer
UBC 552 gave highest 14 RAPD loci, of which 11 were polymorphic and rest
were monomorphic. Primer UBC 535 and UBC 534, both gave 13 RAPD loci,
out of which 12 and 10 were polymorphic, respectively. UBC 535 was able
to distinguish accession IC-99785, IC-35161-D, IC-35177-D and IC-35720-D
by giving unique bands, while UBC 534 gave unique bands with accession
IC-35161-D and IC-35177-D only. 12 RAPD loci were observed with primer
UBC 600, out of which 10 were polymorphic and a unique band of size 1.5
kb was obtained with accession IC-35616-D only.
Primer UBC 572 and UBC 386, both gave 11 RAPD loci in which only 4 polymorphic
bands were obtained with UBC 572 while second primer gave 10 polymorphic
bands but a unique band of size 0.5 kb was observed in primer UBC 572
only with accession IC-35720-D. 10 RAPD loci with 9 polymorphic bands
were obtained with primer UBC 18 beside this a unique band of size 0.7
kb was also observed in accession IC-35177-D. Primer UBC 337, UBC 532
and UBC 350 gave 8, 6 and 5 RAPD loci, respectively. Primer UBC 532 gave
50% (i.e., 3) polymorphic bands while 100% polymorphic bands were observed
with the rest two primers despite of, a unique band of size 0.85 kb was
also observed in accession IC-82233 with primer UBC 337.
Genetic variation: Data of RAPD markers scanned from 27 genotypes
of wheat with ten RAPD (decamer) primers was used to generate similarity
coefficients. The similarity coefficient among hexaploid and tetraploid
wheat ranged from 0.361 to 0.828. The results of pair-wise combinations
indicated that two different accessions of tetraploid wheat (IC-35107-D
and IC-35144-D) were highly related with highest value of similarity coefficient
(0.966), followed by two different accessions of hexaploid wheat (IC-82280
and IC-82526) with 0.952 similarity coefficient. None of the two accessions
had identical patterns. Accession IC-35177-D (tetraploid) and IC-78868
(hexaploid) were highly unrelated, showing the lowest similarity coefficient
value of 0.361.
As the similarity matrix showed, the tetraploid genotypes had more wider
genetic distance value (0.4 to 0.966) than hexaploid genotypes which showed
a relatively narrow genetic distance value, 0.630 to 0.952. An association
among the 27 wheat accessions (genotypes) revealed by Unweighted Pair
Group Method with Arithmetic Mean (UPGMA) cluster analysis (Fig.
1). The dendrogram puts these 27 genotypes into two clusters (Cluster
I and II).
Cluster I comprised of 2 sub-clusters, of which sub-cluster I consisted
of 6 hexaploid accessions with similarity percentage of 75. In this sub-cluster
accession IC-82199 and IC-82202 showed higher genetic similarity followed
by accessions IC-78754 and IC-78868. Sub-cluster II could be classified
into 2 groups. Group 1 is further divided into two sub-groups of hexaploid
wheat accessions having 3 and 8 accessions per sub-group, respectively.
Group 2 included 7 tetraploid wheat accessions and in turn it could be
divided into two
||RAPD based study of genetic divergence of different
wheat accessions (genotypes)
||Dendrogram of wheat genotypes constructed using UPGMA
based on Jaccard`s similarity coefficients. (Scale on top is Jaccard`s
coefficient of Similarity; 1 to 17 are hexaploids and 18-27 are tetraploids)
||RAPD pattern in the context of Karnal Bunt
sub-groups having 2 and 5 accessions per sub-group, respectively. Cluster
II comprised of 3 unique tetraploid wheat accessions, which could be divided
into 2 sub-clusters. Accession IC-35720-D is one sub-cluster and the rest
two accessions (IC-35177-D and IC-35720) were in other cluster.
Genetics relationship with KB resistance: The RAPD pattern with
seven primers (3 primers not gave informative RAPD pattern), among resistant,
moderately susceptible and highly susceptible genotypes, showed high polymorphism
(Table 5). Total 45 RAPD loci were observed with KB resistant
varieties, out of which, 24 (53.3%) were polymorphic and 21 (46.7%) were
monomorphic. Nine RAPD loci with 6 (66.6%) polymorphic bands were obtained
with primer UBC 337. 9 RAPD loci but with 4 (44.4%) polymorphic bands
were also observed with UBC 386 primer. Eight RAPD loci with 50% polymorphism,
6 RAPD loci with 66.6% polymorphism and 5 RAPD loci with 60% polymorphism
were recorded with primer UBC 552, UBC 572 and UBC 350, respectively.
Primer UBC 535 and UBC 600, both gave 4 RAPD loci but with 25 and 50%
polymorphic bands, respectively. In terms of average, 6.4 RAPD loci with
3.4 polymorphic and 3.0 monomorphic loci were generated for each primer.
The RAPD amplification for 10 moderately susceptible wheat varieties
for KB gave a total of 52 RAPD loci (Table 5). Out of
which, 35 (67.3%) were polymorphic and 17 loci (32%) were monomorphic.
The highest number of RAPD loci, 11 was generated from the primer UBC
386, UBC 572 and UBC 337, while the highest number of the polymorphic
loci, 10 was generated from the primer UBC 386 again. Lowest number of
RAPD loci, 4 (with 50% polymorphic bands) were generated from the primer
UBC 600, while 5 RAPD loci were obtained by primer UBC 350, UBC 535 and
UBC 552 with 60, 40 and 60% polymorphic bands. Thus, an average of 7.4
RAPD loci was generated for each primer. In terms of average, 3.5 loci
were polymorphic and 2.4 loci were monomorphic for each primer. Wheat
varieties from different genetic lineage were included in the moderately
susceptible group, therefore they display greater polymorphism.
The RAPD amplification with 6 highly susceptible wheat varieties for
KB with all 7 primers gave 48 RAPD loci, in which 30 loci (62.5%) were
polymorphic and 18 loci (37.5%) were monomorphic, giving an average of
||Analysis of amplicons defining Karnal bunt resistance
6.8 RAPD loci for each primer with 4.2 polymorphic and 2.58 monomorphic
loci (Table 5). The highest number of RAPD loci, 11 and
polymorphic loci, 7 was generated by UBC 386 while primer UBC 337 gave
8 RAPD loci with 62.5% polymorphism. Three primers, UBC 350, UBC 535 and
UBC 552, gave 7 RAPD loci with 71.4% polymorphic bands. Primers UBC 572
and UBC 600 gave 5 and 4 RAPD loci with 40 and 50% polymorphic bands,
respectively. Maximum number of monomorphic RAPD loci was present in the
resistant group, if compared with susceptible and moderately susceptible
Although, PCR amplification data showed a greater polymorphism but nearly
all major bands were monomorphic. Two unique bands of sizes 0.7 and 0.6
kb were obtained with primer UBC 350 that can distinguish highly susceptible
wheat variety HD 2687 and moderately susceptible variety Raj 3077, respectively
(Table 6). Primer UBC 337 and UBC 552 gave single unique
band of sizes 0.4 kb and 3.5 kb with highly susceptible UP 1109 and resistant
HD 29 wheat variety, respectively. Primer UBC 535 differentiated HD 2687
and UP 2003 (both highly susceptible) by giving unique band of sizes 1.2
and 2.0 kb, respectively. Primer UBC 600 gave unique band of sizes 0.7
and 3.5 kb and able to discriminate moderately susceptible HD 2329 and
resistant HD 30. Highest 5 number of unique bands were observed with primer
UBC 386, out of which 3 bands of sizes 2.5, 0.8 and 0.7 kb were obtained
with moderately susceptible variety Sonalika, rest two unique bands of
sizes 0.4 and 1.0 kb were observed with moderately susceptible variety
Raj 3765 and highly susceptible variety C-306. Primer UBC 572 gave two
unique bands of sizes 0.8 and 1.0 kb with moderately susceptible wheat
variety UP 2338.
In this investigation, the genetic analysis of 17 hexaploid and
10 tetraploid Indian wheat varieties was done. Besides this, RAPD based
gene loci were also studied to analyze the evolutionary relationship among
20 wheat varieties having different levels of Karnal bunt resistance,
using the same set of primers. Although investigations on diversity analysis
of tetraploid and hexaploid wheat have been reported (Joshi and Nguyen,
1993; Sun et al., 1998; Pujar et al., 1999) to assess the
phylogenetic divergence amongst wheat according to ploidy status. However,
study of changes in resistance loci during polyploidization is an interesting
area to investigate the consequences on genome evolution.
Of the total amplification products scored in the RAPD analysis of this
study, 82% were polymorphic and detect various levels of polymorphism
between tetraploid and hexaploid Indian wheat accessions. Tetraploid accessions
showed 75.7% polymorphism whereas hexaploid accessions showed 65.3% polymorphism
with 10 RAPD primers, which is consistent with the findings of Joshi and
Nguyen (1993) and Pujar et al. (1999). Low levels of polymorphism
in genotypes could be attributed to a narrow genetic base and the frequent
inbreeding involved in breeding programmes. Lower genetic variation was
found in improved durum cultivars than in durum landraces. Genetic variation
in landraces could be attributed to the considerable amount of natural
outbreeding that occurs in these genotypes. The very low level of genetic
diversity among cultivars could be due to limited selection pressure.
Significant genetic variation within tetraploid wheat existed as revealed
by RAPD analysis although only ten accessions were used in this study.
The Genetic Distance (GD) values of tetraploid accessions ranged from
0.400 to 0.966, which was significantly higher than the GD values of hexaploid
accessions which ranged from 0.630 to 0.952. The narrowness of genetic
basis in the modern improved wheat cultivars is widely accepted and demonstrated
by both pedigree (Cox et al., 1986) and molecular analysis
(Sun et al., 1996). The availability of high levels of genetic
variation could be useful to diversify the genetic basis of the genotype
of interest. The pair-wise comparisons indicated that within hexaploids
(accession IC-104522 and IC-82199), within tetraploids (accessions IC-35161-D
and IC-35102-D) and between hexaploids and tetraploids, accessions IC-35177-D
and IC-78868 showed least similarity. On the other hand, within hexaploids,
accession IC-82526 and IC-82280, within tetraploids, accessions IC-35107-D
and IC-35144-D and between hexaploids and tetraploids, both IC-35149-D
and IC-104637 and IC-35144-D and IC-I04637 were highly associated, as
indicated by the large value of the similarity coefficient.
The six hexaploid accessions grouped together in the dendrogram formed
one cluster, while the rest 11 accessions stood out and grouped with the
7 tetraploid accessions. This may probably be because of interspecific
hybridization of different tetraploid and hexaploid accessions due to
out crossing or because of the majority of the BB genome portion of these
11 hexaploid accessions might largely come from these tetraploids or their
ancestors or due to use of small number of RAPD primers for outgrouping
of tetraploids and hexaploids. Wheat genome is too large and extremely
complex in nature besides having different ploidy levels, so, scanning
this large and complex genome and differentiating one genotype from the
other is too complex. Even though information on single-nucleotide polymorphisms
(SNPs) in hexaploid bread wheat is still scarce. Ravel et al. (2006)
detected 64 single-base polymorphisms in approximately 21.5 kb (i.e.,
1 SNP every 335 bp) using 26 bread wheat line. The level of polymorphism
is highly variable among the different genes studied. Fifty percent of
the genes studied contained no sequence polymorphism, whereas most SNPs
detected were located in only 2 genes and concluded that the genome size
of hexaploid wheat and its low level of polymorphism complicate SNP discovery
in this species.
In present study 6 highly susceptible wheat varieties from distinct genetic
lineages for KB were analyzed. In this case also polymorphism is not particularly
high. Lowest number of RAPDs were produced for the susceptible varieties.
For the primer UBC 337, UBC 572 and UBC 386 maximum numbers (3, 3 and
4, respectively) of monomorphic RAPD loci were present. Not all major
bands were monomorphic. For the primer UBC 572, above trend was contradictory.
The RAPD pattern of primer UBC 572 showed a good contrast between RAPD
pattern for susceptible and resistant varieties. Several unique bands
were present that could identify the several susceptible varieties from
the rest of the twenty genotypes. With some primers, a distinctive RAPD
pattern for resistant, susceptible and moderately susceptible was obtained.
Primer UBC 572 gave a distinct RAPD pattern for discrimination between
resistant and susceptible varieties.
Primer UBC 336 also gave distinct RAPD patterns that distinguish between
moderately susceptible and susceptible varieties. However, distinction
between susceptible and resistant varieties was not observed by this primer.
None of the primers, used in the present study, were able to discriminate
the resistant, susceptible and moderately susceptible genotypes. Therefore,
in present study none of the molecular markers was identified for differentiation
between the resistant, moderately susceptible and susceptible varieties.
However, RAPD pattern using one primer (UBC 572) was successfully employed
for differentiation between the resistant and susceptible varieties. In
an earlier study, few molecular markers were developed for the differentiation
between the resistant and susceptible verities for common Bunt (Demeke
et al., 1996). After screening 672 primers, one primer was
detected that gave one band of size 550 bp which was present in all the
resistant varieties and the other primer resulted in a band of 1.0 kb
which was found in all susceptible varieties and absent in resistant varieties.
The results were reproducible and primers gave the same results in other
wheat varieties, resistant/susceptible to common bunt. However, screening
of a very large number of decamer may be a tedious method. Other methods
like AFLP and analysis based on microsatellite etc. can prove as good
tools for developing the DNA markers for the resistant and susceptible
varieties. Moreover, analysis of the near isogenic lines in the course
of the investigation can further develop reproducible DNA markers. However,
Poole et al. (2007) described the comparison of the Affymatrix
GeneChip wheat genome array and analysis of the data generated revealed
little concordance and suggested that global comparison is not possible.
Authors are thankful to Dr. Dinesh Kumar, NBPGR, New Delhi, India
for providing wheat accessions, Dr. T.S. Mahapatra, NRCPB, IARI, New Delhi,
India for computational data analysis and Chetna Mishra for critical reviewing
of the manuscript.
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