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    Genome wide association studies for flowering time, shelling percentage, harvest index and related traits in chickpea (Cicer arietinum L.)
    (Springer Nature Publishing AG, 2024) Patil, N. Shivanagouda; Hegde, Venkatraman; Vinod, K. K.; Parida, Swarup K.; Jain, Pradeep Kumar
    Grain yield is a product of biomass (BM) and harvest index (HI). HI, not BM, is the major constraint of chickpea productivity in the long season environments of northern Indian plains. This is the first genome wide association study (GWAS) of shelling percentage (Sh.%), HI and related traits in chickpea using genotyping by sequencing approach. Genotyping of 178 germplasm lines involving varieties, trait specific genotypes and advance breeding lines found 35,795 high-throughput single nucleotide polymorphisms (SNPs). The objectives of the study were to unravelling the genomic regions responsible for variation in flowering time, shelling percentage, HI and related traits in chickpea. The phenotypic analysis across three environments showed high variability and connections among HI and related traits. Population structure analysis revealed two sub-populations (k = 2). Linkage disequilibrium (LD) was extensive, and LD decay was relatively low. A total of 172 marker-trait associations (MTAs) were identified for HI and related traits using FarmCPU model, of which days to 50% flowering (DAF), HI and shelling percentage showed significant associations. The current study has identified consistent pleiotropic MTAs, SNC_021165.1_57891716 and SNC_021165.1_57917493, SNC_021164.1_6073633 and SNC_021165.1_33405826 for biomass, pod and seed yield/plant, pod and seed number/plant HI and Sh.%, respectively. All the MTAs observed for SYPL, PYPL and maximum number of MTAs for HI and BM were located on the same chromosome number 6. Further maximum number of MTAs for PPL and SN were distributed on chromosome 5. One of the important findings is that most of the MTAs for SYPL, PYPL, BM, and 100SW are distributed within 25 kb genomic region of chromosome 6. A total of 16 MTAs were retained for Insilco analysis (− log10(p) > 4.0) and searched for their candidate genes in a 100-kb flanking region against the reference genome. The maximum number of genes noticed for DAF (50), followed by Sh.% (48), HI (16), SYPL (13), BM (10), and PYPL (8). The transcripts for DAF, Arabinogalactan proteins and pentatricopeptide repeat were involved in flowering of Arabidopsis. For both PYPL and SYPL, MTA found linked to the genes coding for pentatricopeptide repeat, serine/threonine-protein kinase and E3 ubiquitin-protein ligase. These transcripts played role mainly in pollen maturation, fertilization and flowering time. Chaperone protein DnaJ linked to HI, and receptor-like protein kinase (RLK) for Sh.% were involved in improving yield in Arabidopsis and rice, respectively. The present study also validated one of the MTA linked to DAF which showed r2 value of 12.62%.
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    Unraveling the genetics of heat tolerance in chickpea landraces (Cicer arietinum L.) using genome-wide association studies
    (Frontiers Media S.A., 2024) Danakumara, Thippeswamy; Kumar, Neeraj; Patil, Basavanagouda Siddanagouda; Kumar, Tapan; Bharadwaj, Chellapilla; Jain, Pradeep Kumar; Nimmy, Manduparambil Subramanian; Joshi, Nilesh; Parida, Swarup Kumar; Bindra, Shayla; Kole, Chittaranjan; Varshney, Rajeev K.
    Chickpea, being an important grain legume crop, is often confronted with the adverse effects of high temperatures at the reproductive stage of crop growth, drastically affecting yield and overall productivity. The current study deals with an extensive evaluation of chickpea genotypes, focusing on the traits associated with yield and their response to heat stress. Notably, we observed significant variations for these traits under both normal and high-temperature conditions, forming a robust basis for genetic research and breeding initiatives. Furthermore, the study revealed that yield-related traits exhibited high heritability, suggesting their potential suitability for marker-assisted selection. We carried out single-nucleotide polymorphism (SNP) genotyping using the genotyping-by-sequencing (GBS) method for a genome-wide association study (GWAS). Overall, 27 marker-trait associations (MTAs) linked to yield-related traits, among which we identified five common MTAs displaying pleiotropic effects after applying a stringent Bonferroni-corrected p-value threshold of <0.05 [-log10(p) > 4.95] using the BLINK (Bayesian-information and linkage-disequilibrium iteratively nested keyway) model. Through an in-depth in silico analysis of these markers against the CDC Frontier v1 reference genome, we discovered that the majority of the SNPs were located at or in proximity to gene-coding regions. We further explored candidate genes situated near these MTAs, shedding light on the molecular mechanisms governing heat stress tolerance and yield enhancement in chickpeas such as indole-3-acetic acid-amido synthetase GH3.1 with GH3 auxin-responsive promoter and pentatricopeptide repeat-containing protein, etc. The harvest index (HI) trait was associated with marker Ca3:37444451 encoding aspartic proteinase ortholog sequence of Oryza sativa subsp. japonica and Medicago truncatula, which is known for contributing to heat stress tolerance. These identified MTAs and associated candidate genes may serve as valuable assets for breeding programs dedicated to tailoring chickpea varieties resilient to heat stress and climate change.