Genome-Wide Analysis and Expression Profiling of NBS-LRR Genes in Chickpea Against Ascochyta rabiei

Plant disease resistance genes are key components of genetic interactions between plant and fungal pathogen and among them a sub-class; Nucleotide binding site and leucine rich repeat (NBS-LRR) is the most common domain involved in governing resistance against a wide range of pathogens. This study tested the hypothesis that NBS-LRR genes are involved in resistance to ascochyta blight in chickpea. Genome-wide analysis identified 121 NBS-LRR genes in the chickpea genome that comprises of 0.4 % of total annotated genes. The NBS-LRR genes are not evenly distributed across the chickpea genome and inclined to form clusters. Chromosome 5 has the highest number of the NBS-LRR genes (27% of mapped genes) while chromosome 8 has the lowest number of NBS-LRR genes (4%). A total of 26 NBS-LRR genes were co-localized with the previously reported QTLs for ascochyta blight resistance. Real-time PCR was used to measure relative expression of these 26 genes in three chickpea cultivars (two resistant and one susceptible) at different time points (12, 24, 48 and 72 hours) after inoculation with isolate AR170-3. Differential expression as early as 12 h post inoculation between the moderately resistant cultivars (CDC Luna, CDC Corinne) and the susceptible (ICCV 96029) cultivars was observed. Differential expression observed among the resistant cultivars (CDC Luna and CDC Corinne) at different time points indicating the potential of these cultivars as different sources of resistance. Further efforts to examine the association between NBS-LRR genes with reaction to ascochyta blight infection were done using four recombinant inbred line (RIL) populations derived from crosses between resistant by susceptible and resistant by resistant genotypes under field and greenhouse conditions.