PREDICTING SUCCESS OF INDICA JAPONICA CROSSES IN RICE, BASED ON A PCRMARKER FOR THE S-5(N) ALLELE AT A HYBRID-STERILITY LOCUS/

Exploitation of crosses between the japonica and indica subspecies of rice (Oryza sativa L.) is hindered by hybrid sterility. However, germp lasm containing the S-5(n) wide compatibility allele, derived from tro pical japonica (javanica), can be used as an intermediate in the trans fer of traits. A PCR-based DNA marker, STS213, was used to identify th e fraction of an F-3 population, segregating for S-5(n) and the japoni ca allele S-5(j), that was most likely to yield fertile progeny from c rosses with indica rice. Plants carrying the STS213 allele associated with wide compatibility, had significantly higher fertility than plant s containing the japonica allele. The ability to detect seedlings bear ing S-5(n), the wide-compatibility allele, will facilitate the introgr ession of this allele into temperate japonica cultivars while eliminat ing the need to test cross, self and score fur fertility a majority of the individuals during introgression.