American Research Journal of Agriculture

Developing high-yielding wheat varieties under low-N requires adequate information on the nature of combining ability of available genotypes and the types of gene actions involved in the expression of grain yield and quality traits under such low-N stress. The objective of present study was to get information about performance and general (GCA) and specific (SCA) combining ability variances and effects for grain yield and quality traits of wheat to help its improvement under low-N environment. Two experiments were conducted during two seasons, the 1st under high-N (75 kg N/fed) and the 2nd under low-N (0 kg N/fed) using a randomized complete block design with three replications. The entries included six Egyptian wheat genotypes differing in low-N tolerance and their F2 diallel crosses (without reciprocals). Data analyzed across seasons indicated that L25, L26 and L27 had high values of grain yield and quality traits and showed the best GCA effects for these traits. Under low-N, the best F2 crosses in per se performance and in SCA effects were L25 x L27, L25 x L26 and L26 x G168. Mean squares due to both GCA and SCA were significant under both low-N and high-N for all studied traits, but the magnitude of GCA was greater than SCA, indicating that additive is more important than non-additive genetic variance in controlling the inheritance of all studied grain yield and quality traits. The results indicated that under low-N and high-N, the mean performance of a given parent is an indication of its general combining ability and the mean performance of a given F2 cross is an indication of its specific combining ability effects for all studied grain yield and quality traits.