Overcoming inter-subspecific hybrid sterility in rice by developing indica -compatible japonica lines

Rice ( Oryza sativa L.) is an important staple crop. The exploitation of the great heterosis that exists in the inter-subspecific crosses between the indica and japonica rice has long been considered as a promising way to increase the yield potential. However, the male and female sterility frequently occurred in the inter-subspecific hybrids hampered the utilization of the heterosis. Here we report that the inter-subspecific hybrid sterility in rice is mainly affected by the genes at Sb , Sc , Sd and Se loci for F 1 male sterility and the gene at S5 locus for F 1 female sterility. The indica -compatible japonica lines (ICJLs) developed by pyramiding the indica allele ( S -i) at Sb , Sc , Sd and Se loci and the neutral allele ( S -n) at S5 locus in japonica genetic background through marker-assisted selection are compatible with indica rice in pollen fertility and in spikelet fertility. These results showed a great promise of overcoming the inter-subspecific hybrid sterility and exploiting the heterosis by developing ICJLs.