Abstract
Heritability of white-core (shinpaku) expression was estimated based on F2 variance and selection response in the F2 for high and low frequency using reciprocal crosses of a sake-brewing rice (Oryza sativa L.) cultivar Yamadanishiki and an eating-rice cultivar Reihou. The mean white-core frequency in the F1s and the frequency distribution in the F2s suggested that two or more genes were involved, which were dominant for the reduction of the white-core frequency. A broad-sense heritability estimate based on the F2 variance was high (0.825 - 0.869), while the heritability estimate based on selection for both high and low frequency was much lower (0.309 - 0.447). It was noted, however, that the heritability estimate based on the selection for a higher white-core frequency (0.588 - 0.897) was much higher than that for a lower frequency (−0.037 - −0.093). This observation suggests that the selection for a higher white-core frequency is effective and suitable for the early-generation selection process. On the other hand, only a very few F2 plants showed a white-core frequency as high as that of Yamadanishiki, suggesting that a larger population and/or additional backcrosses to Yamadanishiki are required for the early-generation selection of individuals in which effective alleles are accumulated. Since no adverse effects of the semi-dwarf gene (sd-1) on the white-core frequency were detected, it is suggested that the gene could be useful for breeding programs of sake-brewing rice.
