Gene Effects of Resistance to Septoria tritici in Durum Wheat under Water Stress Level

Gene effects and narrow-sense heritability estimates for components of resistance to Septoria tritici Blotch (STB) assessed under three water stress levels were evaluated using two populations derived from crossing partial-resistant durum wheat inbred lines Agili and Jneh Kottifa and susceptible inbred lines Karim 80 and Razzek by the generation mean analysis. Populations included the resistant parents, susceptible parents, F1 and F2 generations and backcrossed BC1Pr and BC1Ps generations. The presence of an epistatic effect was dependent upon water stress level. In the absence of water stress, only additive and dominance effects were induced for the two populations and the two STB isolates. Therefore, in the presence of water stress levels, the variation of generation means was adequately explained by additive, dominance and digenetic epistatic effects for the two populations. The change in the mode of the gene effect of STB resistance inheritance depending upon water stress level complicated the procedure of incorporating genes of resistance in rentably cultivars Karim 80 and Razzek. In the absence of water stress, selection would be simpler, because only additive and dominance effects were implicated. However, the genetic mechanism will not be stable when the plant experiences water stress. For cultivars designed for exploitation in a wide range of environmental conditions, selection under water stress is suggested for the stability of resistance to STB. Narrow-sense heritability estimates varied between combinations of crosses–isolates–water stress levels and ranged from 51 to 72%.