Yield Potential and Stability of Some Early Promising Bread Wheat Genotypes Under Different Heat Stress Conditions

This study was conducted during the 2022/2023 and 2023/2024 growing seasons at Mallawy Agric. Res. Station, Egypt, to evaluate the effect of three sowing dates on the yield and earliness of five bread wheat genotypes and to identify the most stable genotypes under these conditions. Statistical analysis revealed highly significant differences due to seasons, sowing dates, genotypes, and their interactions for most of the studied traits in both seasons and across the combined analysis. Among the tested sowing dates, 15th November produced the highest values for all traits. Lines 1, 2, and 3 were the earliest in heading and maturity, showing the lowest mean values for grain filling rate and growing degree days, but the longest grain filling period. Line 1 outperformed all other genotypes in yield and its components across different sowing dates. Genotype Sids 14 was also early in heading and maturity and exhibited a high grain filling rate. When sown on 15th January, Lines 1 and 2 recorded the smallest reduction in grain yield and maintained significant superiority in earliness traits. These genotypes demonstrated broad adaptability across sowing dates (from 15th November to 15th January). Moreover, their early maturity and ability to maintain performance under late sowing conditions suggest they can be classified as heat-tolerant. This study recommends using these genotypes i.e. (Lines 1 and 2) to improve in breeding programs for early mature and heat tolerant.