Yield Stability of Sorghum Hybrids and Random‐Mating Populations in Early and Late Planting Dates1

Abstract

Yield stability is an important characteristic for commercial hybrids with a wide range of adaptation. Measurement of stability may be confounded by the diversity of genotypes included or the planting conditions in which the tests are conducted. The effect of early and late planting time on yield stability was studied for 16 grain sorghum [Sorghum bicolor (L.) Moench] hybrids and four random mating populations in eight diverse environments in Nebraska. One stability analysis was performed for all genotypes in each planting time and another over planting times. Genotype yields showed less interaction with environments when planted late than when planted early, perhaps due to more rapid development and less exposure to stress conditions. When genotype means were regressed on environment means, the magnitudes of genotype × environment interactions were found largely due to nonlinear responses of genotypes to environments. Stability of individual genotypes varied between planting times. There were few hybrids that seemed equally stable and desirable in early and late planting. Some hybrids that were not stable in early planting were identified as stable in late planting and vice versa. Hybrids and populations were relatively more stable in late planting than in early planting. The stable populations in late planting did not produce yields higher than the average yield of all genotypes. Hybrids were more stable than populations in early planting, but the reverse was true in late planting. The influence of planting date cannot be ignored in evaluating yield stability in grain sorghum, and a useful guideline would be to plant all nurseries at the same time as commercial plantings in each area.