Heat stress effect on the inheritance of yield, its components and associated traits in two bread wheat crosses

The six-population model supports the development of strategies for selecting genotypes with enhanced heat tolerance and yield stability, which are crucial for wheat improvement programs targeting adverse climate conditions. This study was dedicated to exploring the genetic control and heterosis of earliness, physiological, and yield traits under optimum and late sowing dates. The used plant material was six populations (P₁, P₂, F₁, F₂, BC_1, and BC₂) derived from two crosses of bread wheat; Cross І (Line 606 × Sakha 95) and Cross П (Cham 8 × Masr 3). The results displayed highly significant mean squares due to generations. Heterosis estimates were negative and significant for earliness traits and positively significant for the remaining traits, with a few exceptions. Moreover, at least one of the non-allelic interactions is significant or highly significant, proving the appropriateness of the six parameters model to estimate the different gene effect types governing most studied characters. However, the simple additive-dominance genetic model clarified the inheritance of the number of spikes/plant and days to maturity in cross І (Line 606 × Sakha 95), and number of spikes/plant and number of grains/spike in cross П (Cham 8 × Masr 3) at late sowing. Heritability estimates are labeled as very high to moderately high in the broad sense and, in the meantime, varied as low, medium, and high in the narrow sense. The expected genetic advance had varied values, which ranged from 4.55% days to maturity at the recommended sowing in the cross П (Cham 8 × Masr 3) to 76.07% for the weight of 100-kernel at the late date in the cross І (Line 606 × Sakha 95). Our findings provide valuable insights for wheat breeding programs targeting enhanced yield and heat tolerance.