QTL Analysis of Grain Yield-Related Traits for Terminal Heat Stress Tolerance in Wheat Using SSR Markers.

<b>Background and Objective:</b> Late sowing of wheat exposes the anthesis and grain filling stages of the crop to a terminal heat temperature stress Therefore, detecting putative QTL associated with grain yield and its attributes and identifying the most tolerant genotypes to terminal drought and heat stress across environments will be beneficial in wheat breeding programs. <b>Materials and Methods:</b> In the present study, among 49 CIMMYT wheat lines evaluated for yield and stability in eight environments, we selected the highest ten high-yielding (HYL) and the lowest ten low yielding lines (LYL) along with three wheat check cultivars (CC) for screening with eighteen previously published SSR molecular markers associated with drought and heat stress tolerance. <b>Results:</b> Two SSR markers (BARC126 and BARC11) on 7D were associated with delay heading dates under normal and late sowing dates. Likewise, the SSR markers WMC396, GWM537 and XGWM577 which were mapped on 7B, were significantly linked with grain yield-related traits under one/or both sowing dates, most of them showed desirable effects, indicating terminal heat stress tolerance. Different SSR markers viz., BARC11, XGWM132 and GWM537 showed pleiotropic effects. <b>Conclusion:</b> The SSR markers BARC186-5A, XGWM132-6B, WMC396-7B, XGWM577-7B and GWM165-4B were more prominently associated with heat tolerance by showing a desirable performance of grain yield-related traits under late sowing or across environments, some of these desirable alleles were corresponding to previously QTL in various genotypes that could be valuable in breeding for high-yield in wheat.