Predicting Success of Indica/Japonica Crosses in Rice, Based on a PCR Marker for the S‐5n Allele at a Hybrid‐Sterility Locus

Abstract

Exploitation of crosses between the japonica and indica subspecies of rice (Oryza sativa L.) is hindered by hybrid sterility. However, germplasm containing the S‐5n wide compatibility allele, derived from tropical japonica (javanica), can be used as an intermediate in the transfer of traits. A PCR‐based DNA marker, STS213, was used to identify the fraction of an F3 population, segregating for S‐5n and the japonica allele S‐5j, that was most likely to yield fertile progeny from crosses with indica rice. Plants carrying the STS213 allele associated with wide compatibility, had significantly higher fertility than plants containing the japonica allele. The ability to detect seedlings bearing S‐5n, the wide‐compatibility allele, will facilitate the introgression of this allele into temperate japonica cultivars while eliminating the need to test cross, self and score for ferlility a majority of the individuals during introgression.