Abstract

This study was carried out to determine the relative importance of additive, dominance and epistatic effects of six agronomic traits evaluated in two crosses under irrigated and rainfed conditions. Separate generations mean analyses revealed that gene effects were dependent upon water regime. Under irrigated regime, only additive and dominance effects were implicated in inheritance of all traits, except plant height in the two crosses and grains per spike in the cross Razzek × Chili. However, under rainfed condition, additive, dominance and epistasis effects were induced in the genetic control of these traits. Thus, epistasis effect was water regime depended and seems to play a significant role in the genetic adaptability of populations. The variation of inheritance and the presence of genetic interactions complicate the procedure of breeding. Under irrigated regime, selection would be simpler because only additive and dominance effects were implicated in the genetic control of all traits. Consequently, the genetic mechanism would not be stable when plants are grown in environment with lower water availability. However, for the stability of suitable cultivars, selection under rainfed condition (lower water availability) was suggested. The moderate to high narrow-sense heritability estimates for the majority of traits indicate that selection would be efficient.

Key words: Durum wheat, epistatic effect, genetic adaptability, heritability, water regime.