Inheritance of Cool‐Temperature Seedling Vigor in Rice and Its Relationship with other Agronomic Characters1

Nature of gene action and inheritance of seedling vigor as measured by height of rice ( Oryza sativa L.) seedlings grown for 14 days at 18 C was determined in the F 1 and F 2 generations of a nine‐parent diallel cross. Additive and dominance effects were highly significant, with additive effects being consistent over both the F 1 and F 2 generations, while dominance effects were somewhat inconsistent over generations. In the F 1 and F 2 hybrids, varying degrees of dominance or overdominance were observed for high seedling vigor. The minimum number of dominant alleles controlling the overall parental differences was estimated to be five in the F 1 and four in the F 2 . A moderately high heritability for seedling vigor (57% and 70% for F 1 and F 2 , respectively) indicated that a major portidn of the phenotypic variability is controlled by genes with additive and/or additive × additive effects. High general combining ability for seedling vigor was found in high seedling vigor parents. Seedling vigor was highly correlated with earliness and larger seed size, but relatively low correlations were observed with mature plant height.