Abstract
The pattern of intra-varietal differentiation were studied by diallel cross analysis with seven local strains of a rice variety "Taichung 65". Genetic differences between strains were corroborated in several agronomic characters, though they were small in magnitude. In grain yield, the strains which had been cultivafed over an extended period in Japan, appeared to have accumulated alleles showing dominance in positive direction here in Japan.
