IS AN EGG-KILLER PRESENT IN RICE

The genetic model for hybrid sterility that an allelic interaction at the S5 locus induces the abortion of megaspores has been proposed as partial clarification of the wide compatibility in Asian rice cultivars; this model predicts the presence of an egg-killer. The present study was carried out in order to confirm that the proposed S5i allele acts as an egg-killer against its counterpart, the S5j allele, in the Indica-Japonica hybrid. A conspicuous feature of an egg-killer is the high rate of its transmission into the progeny through the egg. Backcrossing experiments were conducted using the Indica-Japonica hybrid in which the S5i and S5j alleles were assumed to be involved. Although an egg-killer was easily identified by these backcross experiments, it was not detected in the Indica-Japonica hybrid, which suggests that the proposed genetic mechanism for hybrid sterility in Asian rice should be viewed with caution.