GRAIN-YIELD OF COMPOSITE CROSS POPULATIONS OF BARLEY - EFFECT OF NATURAL-SELECTION

The effects of natural selection on grain yield of composite cross population of barley (Hordeum vulgare L.) was investigated to determine the relationship between the amount of genetic diversity and yield and stability of yield. Yield test data for five commercial cultivars of spring barley and early, intermediate, and late generations of three composite cross populations were analyzed by regression methods. Deviations from regression were generally larger for the commercial cultivars. Deviations from regression were particularly large for the commercial cultivar Sutter, indicating instability, which was consistent with its ability to perform well in only one limited geographical area. Deviations from regression for the widely adapted cultivar Atlas 68 were small, and similar to those of the composite crosses. The composite crosses continued to show a marked yield increase over generations, perhaps as a result of increased adaptation. As indicated by cluster analyses, the commercial cultivars (with the exception of Sutter) were more similar to one another than they were to the composite crosses, and vice versa. Stability was associated with rainfall, evidently through the effect of rainfall on the prevalence of foliar diseases, especially scald [Rhynchosporium secalis (Oudem.) J.J. Davis] and net blotch (Pyrenophora teres Drechs.), and on lodging. It was concluded that the composite cross populations offer an opportunity to produce cultivars that show small or no genotype-environment interaction.