Induced Variation for Combining Ability in Wheat

Estimates of combining ability variances and effects for grain yield per plant, grains per spike and 1000-grain weight were obtained from diallel, F₁ and F₂ populations derived from normal and EMS treated (0⋅4%) nine diverse, elite wheat (Triticum aestivum L.) cultivars. GGA and SGA variances were highly significant for yield and 1000-grain weight, whereas for grains per spike only the GCA variance was significant. The estimates of GGA variances were higher than those of SCA. The EMS treatment caused increase in additive effects for grain yield and 1000-grain weight and in nonadditive effects for number of grains per spike. For grain yield, per se performance of the parents was not related with their GCA effects, whereas for grain number and grain weight the two estimates were related. Breeding plans which may effectively exploit both fixable and nonfixable components of genetic variance for evolving superior breeding populations of spring wheat have been suggested.