Evaluation of Wheat Chromosome Translocation Lines for High Temperature Stress Tolerance At Grain Filling Stage.

High temperature (HT) stress is detrimental to wheat (Triticum aestivum L.) production. Wild relatives of bread wheat may be the sources of HT stress tolerant genes as they grow in stressed habitats. Wheat chromosome translocation lines, produced by transgressing a small segment of chromosome from wild relatives to bread wheats, were evaluated for HT stress tolerance at grain filling stage. Sixteen translocation lines and four wheat cultivars were grown at optimum temperature (OT) of 22/14°C day/night. Ten days after anthesis, half of the plants were exposed to HT stress of 34/26°C for 16 d, and other half remained at OT. High temperature stress decreased leaf chlorophyll, Fv/Fm, individual grain weight (IGW), and grain yield by 22, 39, 44 and 45% respectively, when averaged across the genotypes. Effect of HT stress was not evident in TAs 5594, 5617, and ‘HUW 206’ for leaf chlorophyll, which decreased by 44% in TA 5639. Effect of HT stress was not evident in TAs 5594, 5617, 5599, 5088, and ‘HUW 206’ for F_v/F_m, which decreased by 66% in TA 5639. High temperature stress decreased IGW ranging from 30% in TAs 5594, 5088, and 5608 to 71% in TA 5640.  Effect of HT stress was not evident in several genotypes including TAs 5594, 5088, and 5608 for grain yield, which decreased by 77% in TA 5640. The heat susceptibility index (HSI) calculated for grain yield was ≤0.5 in TA5608, and >0.5–≤1.0 in several genotypes including TAs 5594 and 5088. The HSI of TA 5640 was >1.0. The results showed genetic variability in chromosome translocation lines with TA 5608 as highly tolerant, TAs 5594 and 5088 moderately tolerant, and TA 5640 as extremely susceptible of HT stress at grain filling stage. The tolerant lines thus identified may be utilized in improving HT stress tolerance of wheat cultivars.