Genotype ✕ Environment Interactions for Leaf Area Parameters and Yield Components and Their Effects on Wheat Yields

Genotype × environment interactions for parameters characterizing source and sink capacity and their effects on grain yield of three divergent wheat (Triticum aestivum L.) cultivars were studied over a 10-year period. The mean square in the number of spikes/m² due to genotype × year interaction (g × y) was greater than the mean squares due to years or genotypes alone. The mean square for leaf area index (LAI) and leaf area duration (LAD) due to years was greater than the mean squares due to genotypes and g × y interactions. The mean squares due to genotypes were greater than the mean squares for years and g × y interactions for number of kernels/spike, 1,000- kernel weight, disease and lodging resistance, as well as for grain yield. Environmental factors exhibited greater effects on the parameters of source capacity than on the parameters of sink capacity. The LAD showed the highest positive relative contribution to grain yield for each cultivar over the 10-year period. Direct effects of other variables differed among the cultivars; some exhibited positive and some negative direct effects on grain yield. Using seven variables, 83% of variation of grain yield could be “explained” for the cultivar ‘Sava,’ 75% for ‘Bezostaia,’ but only 34% for ‘Bankut,’ as shown by the coefficient of determination. For climatic variables the only significant relation was a positive association between grain yield and hours of sunshine in May and June, i.e., during gamete formation, fertilization, and the grain filling period. Bezostaia showed the greatest stability in yield performance, but Sava gave the highest grain yield in all years. Since a grain producer is interested in having high grain yields at his location, the preference in the choice of cultivars should be given to the meangrain yield rather than to the other stability parameters.