Inheritance of drought tolerance in bread wheat using generation mean analysis

Generation mean analysis with joint scaling test was performed to determine the type of gene action. Generations of F1, F2, BC1 and BC2 were derived from crosses between Shiraz (drought susceptibility) cultivar with Ws-82-14 line (drought tolerance) and Shiraz cultivar with Shole (drought tolerance) along with their parents were sown in a randomized complete block design with three replications under stress and non-stress moisture conditions. Traits evaluated in this experiment included plant height, peduncle length, spike length, number of grains per spike, grain yield per plant, 1000- seed weight, flowering date and plant weight. Genetic parameters including mean (m), gene effects additive (d), dominance (h), epistasis effects additive × additive [i], additive× dominance [j], and dominance× dominance[l] were evaluated for different traits. The dominant gene effect was found the most important genetic effect in controlling many traits evaluated. In addition the additive× additive [i] epistasis was more important than dominant× dominant[l] epistasis. The average of broad sense and narrow sense heritabilities were obtained for grain yield in Ws-82-14×Shiraz cross in normal condition, 78% and 44%, in stress condition, 69% and 57%, while in Shole×Shiraz cross in normal condition were 52% and 29%, and in stress condition, 78% and 56%, respectively. The average degree of dominance in most of the traits was larger than 1which indicated the importance of dominance and it was in agreement with the low value of narrow sense heritability. Transgressive segregation for the whole traits showed that these crosses can result into recombinant progenies for drought tolerance.