*Presenting authors (sourabhkumar7669@gmail.com)

Wheat is a vital staple food world-wide, but its grain production is adversely impacted by rising global temperatures, posing a serious threat to food security. To unravel the genetic basis of key spike traits under heat stress conditions, a study was conducted using a doubled-haploid (DH) mapping population of 177 lines, developed from a cross between a heat-sensitive cultivar (PBW343) and a heat-tolerant genotype (KSG1203).

This population was phenotyped for six spike-related traits in 15 different environments, including timely, late, and very late sowing conditions, over three years and two locations within Indo-Gangetic plains. Composite interval mapping was performed using the best linear unbiased estimates for each trait and a sequencing-based genotyping (SBG) SNP physical map containing 5,710 markers, spanning a genomic distance of 14,263.4 Mb. In total, 52 QTLs (17 for timely, 11 for late, 18 for very late sown conditions, and six common) with PVE (%) ranging from 7.1% to 23.6%, were identified and integrated into the wheat physical map.

These included 12 stable QTLs displaying high PVE (%). These QTLs were recommended for marker-assisted recurrent selection (MARS) for wheat improvement in both optimal and heat stress conditions. These QTLs were validated in high yielding DH lines. A number of QTLs overlapped the known genes (TaHsfC2a-B, TaCol-B5, WAPO1, starch synthase I, TaGW2-B1, TaGW2-B1 and PI1-1B/WPI-1-1B0).

These genes are involved in heat shock response, starch synthesis, spikelet number per spike, spike architecture (including spikelets and floret development) grain weight, grain yield, and other aspects of spike and grain development. Moreover, 74 candidate genes (CGs) linked to heat tolerance, encoding 37 distinct proteins, were also identified.

The important QTLs recommended for MARS and the identified CGs constitute important genomic resources which may prove useful in breeding for heat-tolerant wheat varieties/germplasm enhancing the crop’s resilience under adverse climatic conditions.

Keywords: Wheat, doubled haploid population, heat stress tolerance, SBG-SNPs, quantitative trait loci, candidate genes