MAGIC population-based genetic dissection of yield-related traits under heat stress in wheat (Triticum aestivum L.)

Heat stress poses a significant challenge to wheat productivity, necessitating the identification of genetic loci conferring yield stability and resilience. This study evaluated a multi-parent advanced generation intercross (MAGIC) population for biomass (BM), grain weight per spike (GWPS), thousand grain weight (TGW), yield per plot (YLD), and heat susceptibility indices (HSI_BM, HSI_GWPS, HSI_TGW, HSI_YLD) under timely-sown irrigated (TSIR) and late-sown irrigated (LSIR) conditions across Delhi, Dharwad, and Pune. The population exhibited substantial phenotypic variation and yield and biomass positively correlated and inversely related to heat susceptibility, highlighting potential for selection under stress conditions. Genome-wide association studies identified SNPs across nearly all wheat chromosomes associated with BM, GWPS, TGW, YLD and their corresponding heat susceptibility indices (HSIs), with phenotypic variance explained (PVE) ranging from 3-15%. Major-effect loci (e.g., AX-94529210, AX-95104040 and AX-95204353 for GWPS; AX-95210025 for TGW, AX-94496657 for BM; AX-94877518, AX-94942005 and AX-95118494 for YLD) and numerous minor-effect SNPs contributed to trait variation, reflecting a polygenic architecture. Allelic effect analysis demonstrated consistent enhancement of yield and reduction of heat susceptibility across environments. Collectively, this study underscores the MAGIC population as a valuable resource for dissecting complex traits and provides genomic insights for marker-assisted breeding of high-yielding, heat-tolerant wheat varieties.