Gene Action For Certain Quantitative Characters in Common Wheat in Optimal and Suboptimal Environments

The parental, F2 and F3 generations of two crosses, hd 1593 × HD 1553 and hd 1949 X C.591, parental and F2 generation of the cross Mex CB 116 × HD 1917 were evaluated for five quantitative characters in two different environments represented by irrigated and un-irrigated conditions. The estimates of various genetic parameters using both means and variances showed that the estimates of both gene effects and genetic variances were dependent upon the genetic material, character and the environment. Over-all in the cross Mex CB 116 × HD 1917 the variability in grain yield, ear number and 100 grain weight was due to additive gene effects. in the cross HD 1949 × C 591, additive-dominance model was adequate for all characters, except plant height. in the cross HD 1593 X HD 1553, non-allelic interactions involving additive × additive effects were important for grain yield, plant height, ear number and grain number in either one or both environments. The estimates of [d] were relatively stable across the two environments, whereas those of [h] showed sensitivity, with positive, negative or zero values in different environments. There was a trend of dominant/partially dominant genes conditioning lower expression of the character under sub-optimal environment and higher expression in optimal environment. The magnitude of genetic, and environmental variancess was also influenced by the environment resulting in increased or decreased variation depending on the character and the cross under study, consequently affecting the heritability of some characters such grain number/ear. The results suggested the need for estimation of different genetic parameters in multi-environments.