Drought stress is one of the most important factors reducing crop production in the world. Understanding the type and relative amount of genetic components is essential for determining the breeding methods for genetic improvement of drought tolerance related traits. In the present study, generation means and variances analyses were employed to estimate additive, dominance and epistatic effects as well as additive, dominance and environmental variances based on mixed linear model method. The results of generation mean analysis through six generations (P1, P2, F1, F2, BC1, BC2) revealed significant epistasis for flag leaf length, flag leaf width, spike weight, harvest index, weight of 100 grains and grain yield per plant under normal and water deficit conditions, and for plant height, peduncle length, effective tiller number, spike length and straw weight under water deficit condition. The nature and value of gene effects for majority of traits were different under normal and stress conditions. Broad-sense heritability values for flag leaf width, spike length, effective tiller number, harvest index and weight of 100 grains were higher in stress than in normal conditions, (>0.4), whereas the narrow-sense heritability values for most traits (except flag leaf width, spike length, effective tiller number and harvest index) were lower in stress than normal conditions.