study of genetic control of some yield related traits of bread wheat (triticum aestivum l.) under drought stress condition using generation mean analysis

breeding programs strategies depends on genetical mechanism of selection traits. in the present research, generation mean analysis with joint scaling test was performed to determine the gene action. f1, f2 and f3 generations, derived from roushan and kavir cross along with their parents were sown in a partial lattice design with two replications under stress condition at the research field of shahid bahonar university of kerman in 2012-2013. the traits including number of tillers, awn length, single plant weight, grain number per plant, flag leaf width, spike length and peduncle length were measured. genetic parameters including additive effect (d), dominance effect (h), additive×additive [i] and dominance×dominance effect [l] were evaluated for different traits. all traits were controlled by additive, dominance and epistatic gene effects. additive effect was more valuable than dominance for peduncle length. the degree of dominance for most of the traits was higher than one, which indicated the importance of dominance effect in genetic control of evaluated traits. in addition, the dominant×dominant [l] epistasis was more important than additive×additive [i] epistatic effect. the broad and narrow sense heritability of evaluated traits were 0.67 to 0.97 and 0.37 to 0.96, respectively. positive heterosis was observed for spike length, peduncle length and flag leaf width. the dominant gene effect was detected as the most important genetic effect in controlling several traits. therefore, selection should be made in later generations till desirable genes are fixed.