Evaluation of Grain Yield and its Attributes in Bread Wheat Cultivars Under Heat Stress Conditions

This study was conducted at Al-Ghuraira Village, Esna Center, Luxor Governorate, Egypt to evaluate the performance of twelve bread wheat cultivars under heat stress (late planting dates) in newly reclaimed soil during 2017/2018 and 2018/2019. Twelve bread wheat cultivars (Giza 168, Giza 171, Sids 1, Sids 12, Sids 14, Gemmeiza 9, Gemmeiza 11, Misr 1, Misr 2, Misr 3, Shandwell 1 and Sakh 94) were grown at three planting dates (November 20, December10 and December 30). Each planting date in each season was considered as a separate experiment. The experimental design for each sowing date was a randomized complete block design (RCBD) with three replications. The obtained result show that the tested sowing dates, bread wheat cultivars and their interaction had a highly significant effect on height of height and spike length, spikes number m-2, number of kernels spike-1, 1000-kernel weight and grain yield fed.-1 in both seasons. Moreover, sowing Sids 12 bread wheat cultivar on 20 November recorded the high average values of grain yield (3.03 and 3.11 ton/fed. in the two respective seasons). As for the heat sensitivity index (H.S.I), 6 out of 12 cultivars showed H.S.I values ​​less than unity for the second planting date and 5 cultivars for the late planting date in both seasons, which indicates that these varieties were more tolerant to heat stress. Moreover, it appears that the Misr 1 cultivar was more tolerant to heat stress, as it showed heat sensitivity index values ​​less than unity at the two late planting dates.