Combining ability of harvest index and grain yield in spring wheat

Six spring wheat (Triticum aestivum L.) cultivars were crossed in diallel and the F1, F2, and parents evaluated in replicated design in the field to determine the nature of combining ability governing harvest index and grain yield. General combining ability (GCA) effects were of major importance for grain yield and harvest index while specific combining ability (SCA) effects were of little or no consequence. Correlations of GCA effects for F1 and F2 grain yield and harvest index were significant and both the grain yield and harvest index were controlled by additive effects of genes. Grain yield was associated with non-grain yield and height, but harvest index was not. These findings suggest that the use of harvest index as a selection criterion for grain yield would be beneficial when utilized in conjunction with non-grain yield and height.