Since an allele S_5~n was identified and used to overcome the sterility in hybrid rice breeding, many intersubspecific hybrids harbored the S_5~n allele had been tested for their yield potential. Such hybrids showed pronounced heterosis and high yield potential, but some of them had an unstable or low seed set. The reason for the low seed set was attributed to the partial pollen sterility. Since an allele S_5 ~ n was identified and used to overcome the sterility in hybrid rice breeding, many intersubspecific hybrids harbored the S_5 ~ n allele had been tested for their yield potential. Such hybrids showed pronounced heterosis and high yield potential, but some of them had an unstable or low seed set. The reason for the low seed set was attributed to the partial pollen sterility.