QTL Mapping for Traits Associated with Drought Tolerance and Combined Drought and Heat Tolerance in Seedling Winter Wheat

Drought and heat stresses are major constrains for wheat growth. As a climate change occurs, both stresses can occur singly or in a combination. The main objective of this study was to identify QTL associated with drought tolerance (D) and combined drought and heat (D+H) tolerance in winter wheat at seedling stage. A set of 140 recombinant inbred lines (F₉) derived from crossing Harry (drought tolerant) and Wesley (drought susceptible) was evaluated in the greenhouses under D and D+H. In both treatments, the experiments were designed based on randomized complete block design with three replications each. Four traits were scored in each treatment: plant height (PH), stay-green (SG), leaf wilting (LW), and recovery after irrigation (RAI). The results revealed that high genetic variation was found among genotypes for all traits in both treatments. The heritability ranged from 0.53 (PH) to 0.80 (RAI) under D, while, it ranged from 0.48 (LW) to 0.90 (PH) under D+H. Harry was tolerant to both stresses. Low phenotypic and genotypic correlations were found among traits in each treatment. The QTL analysis was performed using 3556 SNPs derived from genotyped-by-sequencing method. The results of QTL analysis identified two and three QTL for SG, three and two for LW, two and three for PH under D and D+H, respectively. Three QTL were detected for RAI only under D+H. Most of QTL were located on 4AL chromosome. All detected QTL were individual QTL and no pleiotropic effects were observed for any QTL.