Combining Ability, Gene Action, Yield, and Quality in Half-Diallel Bread Wheat

The study conducted to improve bread wheat genotypes with high grain yield, yield related traits, and quality. A half diallel mating design involving seven bread wheat parents (Maroof, Aras, Hsad, Alaa, Tamuz-2, Adana and Sabr Beg) and their 21 progenies were used to study the combining ability in bread wheat. Seven bread wheat (Triticum aestivum L.) parents and 21 F1 crosses were evaluated using half-diallel analysis under RCBD with three replications. The parent Tamuz-2 emerged as the best general combiner for several yield attributes, whereas the cross 1x5 exhibited maximum for spike weight plant-1, biological yield, and protein content. Cross 5x2 recorded maximum for grain weight spike-1 and thousand grain weight, besides recording maximum grain yield. There is strong genetic diversity in many of these attributes. Though the additive and non-additive actions were significant, the latter predominated in many of the attributes. Suitable parent and cross combinations have been identified to be useful in future breeding work. The Analysis of variance reveal that the general combining ability (GCA) of the parents was significant for days to heading and spike length and highly significant for plant height, spike weight, grain number spike-1, grain weight spike-1, thousand grain weight, harvest index, biological weight plant-1, protein content, and grain yield plant-1, while
the specific combining ability (SCA) effects of the crosses were highly significant for almost all of the traits. In particular, for the sike length, (h_(b.s)^2) =0.503 and (h_(n.s)^2)= 0.154; for grain yield plant-1, (h_(b.s)^2)= 0.950 and (h_(n.s)^2)= 0.464. The high value of h_(b.s)^2 for biological yield per plant (0.981) pointed to the strong genetic influence, while the smaller (h_(n.s)^2) (0.474) indicated smaller additive variance, reducing selection efficiency.