Evaluation of some bread wheat genotypes for heat tolerance under terminal heat stress conditions

Terminal heat stress leads to significant yield reduction in wheat. Thus, the determination of heat tolerant genotypes is of major importance in wheat breeding program. The present study was conducted at Shandaweel agricultural research station, Sohag, Egypt during 2019/2020 and 2020/2021 growing seasons, to evaluate twelve bread wheat genotypes under normal sowing (20 November) and late sowing (30 December) dates, the experiment set up as a randomized complete block design with three replications. Results revealed that late sowing (terminal heat stress) had a significant adverse impact on agronomic, physiological traits and grain carbohydrate content. The genotype Shandaweel 2, followed by Giza 171 and Sids 14 performed better than other genotypes for grain yield under the normal sowing. On the other side, Shandaweel 2 outperformed the tested genotypes under the late sowing. Based on heat susceptibility index (HSI), the cultivars Sids 12, Misr 2, Sakha 95 and genotype Shandaweel 2 showed HSI<1 and they can be labeled as heat tolerant genotypes, while Sids 14, Misr 1, Giza 171 and Misr 3 showed HSI>1 and they can be considered as heat sensitive cultivars. GGE biplot analysis and ranking of genotypes revealed that the new line Shandaweel 2 was the an ideal genotype in terms of yielding ability and stability and it was suitable for planting under normal and late sowing conditions, while Giza 171 was suitable for planting under the normal sowing. The GYT biplot and superiority index showed that Shandaweel 2 and Giza 171 had the best traits profile.