The current research for the study of gene action for days to heading was applied under water stress at South Valley Univ., Exp. Farm, Qena, Egypt in 2022/2023 and 2023/2024 seasons. The materials consisted of 28 F₂-generations and their 8 parents. Mean squares due to additive and non-additive genetic variances were highly significant under both environments in the two seasons. The additive component accounted for a greater proportion than the non-additive component in the F₂-generations under all conditions, this highlights that additive gene effects played the most significant role in the inheritance of earliness. High narrow sense heritability for heading date under both environments in both seasons was observed. The differences between environments, among genotypes and genotypes × environments interaction were significant (p<0.01) for all the studied traits. Comparing the correlated traits under water stress conditions with normal irrigation illustrated that these traits under first condition were lower than under second condition. The response to selection for earliness as percentage of deviation from the F₂-populations ranged from -15.58 (P₃ × P₄) to 1.38 % (P₃ × P₈) and from -15.49 (P₃× P₄) to 9.68% (P₂ × P₈) under normal and water stress environments, respectively. The correlated response in grain weight/spike, 100-grain weight and grain yield was decreased under both conditions. Direct selection for early maturity under water stress conditions is anticipated to be more efficient compared to indirect selection.