Combining Ability and Gene Action Controlling Grain Yield and Its Related Traits in Bread Wheat under Heat Stress and Normal Conditions

High temperature is a major environmental stress that devastatingly affects wheat production. Thenceforth, developing heat-tolerant and high-yielding genotypes has become more critical to sustaining production particularly under abrupt climate change fast-growing global population. The present study aimed evaluate parental their cross combinations normal heat conditions, exploring diversity based on dehydration-responsive element-binding 2 gene (DREB, tolerance in response abiotic stress) genotypes, determining action controlling yield traits through half-diallel analysis. Six diverse bread (local exotic) 15 F1 hybrids were evaluated at two different locations timely late sowing dates. Sowing date, location, genotype, interactions significantly impacted the studied traits; days heading, chlorophyll content, plant height, grain yield, its attributes. Cluster analysis classified parents crosses into four groups varying from heat-sensitive indices. P2 P4 identified as an excellent source of beneficial alleles for earliness high yielding stress. This was corroborated by DNA sequence DREB transcription factors. They highest homologies dehydrin with species. hybrid P1 × P5, P6, P4, P3 P5 detected be good specific combiners attributes conditions. These designated could used breeding climate-resilient cultivars. non-additive genetic variances preponderant over additive most both narrow-sense heritability ranged low moderate traits. Strong positive associations between each number grains/spike, thousand-grain weights, which suggest importance indirect selection stress, especially early generations, due effortlessness measurement.