Mapping QTLs for yield and related traits in bread wheat under terminal heat stress

To identify chromosomal regions and candidate genes controlling important wheat (Triticum aestivum L.) traits under heat stress, a doubled haploid population was developed from a cross between KSG0057, a selection out of PBW343 and KSG1190, a heat stress tolerant line. The population was evaluated for grain yield, 100-grain weight, grain weight of main spike, number of grains per main spike, number of spikelets per main spike, spike length, and plant height during 2016-2017 and 2017-2018 at two locations in India. Heat stress was applied by conducting trials under normal, late, and very late sown conditions. The mapping population was genotyped using sequencing-based genotyping to target the genic fraction of the genome. A 3875.3 cM linkage map was constructed via 674 high-quality single nucleotide polymorphisms. Composite interval mapping was done for individual environments and for reduction percentage due to late and very late planting. With 38 regions common between the two types of analysis, 66 genomic regions containing 155 quantitative trait loci (QTLs) for individual environments and 100 containing 152 QTLs for the reduction percentage analysis were identified. Of the 155 QTLs, 82 were found only under very late sown conditions. Of the 152 QTLs, 40 were for heat stress and 45 for severe heat stress. The QTL-containing regions ranged from 1.5 kb to 684.9 Mb in size, with 35 being <1 Mb and 30 being <5 Mb. Number of genes in these 35 regions ranged from 1 to 19. Candidate genes for 16 of the regions were identified as the underlying region of 1.5-287.5 kb contained only one gene each.