Abstract:
Asian-cultivated rice (
Oryza sativa L.) consists of two subspecies, indica (
Oryza sativa L.
indica) and japonica (
Oryza sativa L.
japonica) subspecies. There are considerable differences between them in morphology, physiology and gene level. The stronger heterosis generated by the genetic differences between inter-subspecies could improve the yield potential of rice. However, the application of heterosis in indica-japonica subspecies is limited because of the serious hybrid sterility in F
1 hybrid. Hybrid sterility, a common form of postzygotic reproductive isolation, is universal and complex, controlled by multiple hybrid sterility loci. The discovery of wide-compatible varieties (WCVs) provides the possibility to overcome interspecific hybrid sterility as the F
1 hybrids show normal fertility whether WCVs crossed with indica or japonica rice. In this paper, we summarize the indica-japonica divergence, the genetic basis of hybrid sterility in indica-japonica subspecies, the identified hybrid sterility QTL and genes, and analyze the molecular mechanisms of the cloned hybrid sterility genes and the function of wide-compatible genes. On this basis, we propose four approaches to overcome inter-subspecific hybrid sterility, and improve the fertility of indica-japonica F
1 hybrids precisely, including breeding inter-subspecific introgression rice, developing indica-compatible japonica lines and wide-compatible lines, and creating wide-compatible genes by gene editing technology. The application of indica-japonica hybrid rice will promote a major change in rice industry.