Selection for Test Weight and Kernel Weight in High Yielding Wheat Using a Safety-First Index


Abstract: Five breeding lines and 4 cultivars were grown in replicated trials at 1 location in 1999-2000 and 2 locations in 2000-2001 cropping seasons in İzmir in order to determine the usefulness of a safety-first selection index in making selection among high yielding wheat genotypes for test weight and thousand-kernel weight. Genotype × environment interactions were significant for these 2 quality traits. The regression coefficient (b_i) of genotypes, variance (Si_i^2) of a genotype across environments, and a safety-first index (I_i) were calculated to evaluate the stability of genotypes for test weight and thousand-kernel weights. Wheat genotypes with lower bi values and small variance (S_i^2) across environments (the most stable ones) tended also to have lower means for these 2 traits. However, those genotypes with the largest value of index (I_i), which is considered desirable, were found to have the highest mean values for both test weight and thousand-kernel weight. The rank-correlation coefficient between (I_i) and (Y_i) values was significant for thousand-kernel weight. The ranking from I_i was significantly correlated with the rankings from the stability parameters bi and S_i^2 for test weight. The rank-correlation coefficients between bi and S_i^2 for the 2 physical quality traits were highly significant and of similar magnitude (r = 0.983). It was concluded that a safety-first selection index can be useful in plant breeding for the improvement of wheat cultivars with enhanced stability and consistency of quality characteristics when genotype × environment interaction is present.

Keywords: Bread wheat, yield, safety-first index, physical quality traits, rank correlation

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