GENETIC ANALYSIS OF NBS-LRR GENES AND THEIR ASSOCIATION WITH ASCOCHYTA BLIGHT RESISTANCE IN CHICKPEA (CICER ARIETINUM L.)
Sagi, Mandeep Singh 1992-
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Ascochyta blight is one of the major diseases of chickpea worldwide. Genetic control of resistance to ascochyta blight in chickpea is complex and governed by multiple quantitative trait loci (QTLs). The molecular mechanism of quantitative resistance to ascochyta blight and the genes underlying the QTLs are still unknown. The most predominant resistance (R)-genes in plants contain nucleotide binding site and leucine rich repeat (NBS-LRR) domains. One hundred twenty-one NBS-LRR genes were identified in the chickpea genome. Ninety-eight of these genes contained all essential conserved domains while 23 genes were truncated. These NBS-LRR genes were grouped into eight distinct classes based on their domain architecture. Phylogenetic analysis separated these genes into two major groups based on their structural variations, the first group with a toll or interleukin-1 like receptor (TIR) domain and the second group either with or without a coiled-coil (CC) domain. The NBS-LRR genes are unevenly distributed across the eight chickpea chromosomes and nearly 50% of the genes are present in clusters. The expression profiles of thirty NBS-LRR genes that were co-localized with nine previously reported ascochyta blight QTLs were evaluated for potential involvement in response to ascochyta blight infection. Expression patterns of these genes were studied in two moderately resistant (‘CDC Corinne’ and ‘CDC Luna’) and one susceptible (‘ICCV 96029’) genotypes at different time points after ascochyta blight infection using real-time quantitative PCR. Twenty-seven NBS-LRR genes showed differential expression in response to ascochyta blight infection in at least one genotype at one-time point. The majority of these NBS-LRR genes showed differential expressions after inoculation in the resistant and susceptible genotypes suggesting the potential involvement of these genes in response to Ascochyta rabiei infection. Five NBS-LRR genes showed genotype-specific expression. Eighteen QTLs for ascochyta blight resistance were identified in three recombinant inbred line populations (CPR-02, CPR-03, and CPR-04) under greenhouse and field conditions. These QTLs were distributed across linkage groups 2, 3, 4, 5, 6 and 8 explaining 6 to 33% of the phenotypic variations. The current study identified new and common genomic regions associated with ascochyta blight resistance. Thirty-one NBS-LRR genes were co-localized with the ascochyta blight resistance QTLs in four RIL populations. Eight NBS-LRR genes were common in at least two RIL populations. The co-localization of the NBS-LRR genes within the ascochyta blight resistance QTLs was further confirmed by genetic mapping of the NBS-LRR genes in two RIL populations.
DegreeMaster of Science (M.Sc.)
CommitteeBanniza, Sabine; Hucl, Pierre J.; Warkentin, Tom
Copyright DateJanuary 2018
Chickpea, Ascochyta Blight, NBS-LRR Genes, Candidate Genes, Physical Mapping, Gene Expression, QTL Mapping, Genetic Mapping