ABSTRACT
Fifteen inbred lines and three testers were crossed in line x tester scheme to study the combining ability effects for earliness, grain yield and yield components. A yield trial included the 45 top crosses, 15 inbred lines and 3 testers. The experiment was conducted for three years at the Agricultural Research Station of the Faculty of Agriculture, Moshtohor, Benha University. The experimental design was randomized complete blocks with three replications. Mean squares due to crosses (C) inbred lines (L), testers (T) and line x tester (LxT) were significant for most studied traits for the combined analysis of two evaluation seasons. Significance of interaction variance for C, L, T and LxT with sowing dates on most studied traits was detected. δ2SCA played the major role in determining inheritance of all traits, revealing that the largest part of the total genetic variability associated with these traits was a result of non- additive gene action. The magnitude of the interaction of δ2SCA x years (SY) was generally higher than for δ2 GCA x SY. This indicates that non-additive type of gene action is more affected by SY than additive and additive x additive types of gene action. Inbred lines M L4, L8, L9, L10, L11 and L12 were reliable general combiners for earliness and M L3, L4, L5, L6, and L13 for grain yield plant-1. For earliness the top-cross M 212D x Sc (M 201 x M 204) gave the best effects. Regarding grain yield plant -1 , crosses M 242A x L M 204, M 236B x SC (201x204), M 250C x M pop. and M 236B x L M 204 appeared efficient and promising in raising grain yield.
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