Abstract:
Objective By using molecular detection and genome editing, an efficient and rapid creation of artificial hybrid-compatible lines is carried out to provide a new paradigm for breaking the indica-japonica hybrid sterility and realizing the utilization of indica-japonica hybrid vigor.
Method In this study, an elite indica rice variety ‘Huanghuazhan’ (HHZ) and an elite japonica rice variety ‘Zhongjia 8’ (ZJ8) were used as test materials. The genotypes of the indica-japonica hybrid sterility loci in HHZ and ZJ8 were detected by molecular detection. Then, the genome editing was carried out to knock out the major hybrid sterility gene(s) conferring HHZ-ZJ8 hybrid fertility, thereby efficiently and rapidly creating indica-japonica hybrid F1 with high fertility.
Result The HHZ-ZJ8 hybrid F1 plants showed strong hybrid vigor, but exhibited spikelet semi-sterility. According to genetic mechanism of intersubspecific hybrid sterility in indica and japonica rice, molecular detection revealed that one known major HS locus S5 exists in the HHZ-ZJ8 hybrids. Then, genome editing was used to knockout S5-ORF5+ (killer gene) in HHZ and S5-ORF4+ (partner gene) in ZJ8. Compared with the wild type, several important agronomic traits of these edited materials were displayed with no significant changes. However, the spikelet fertility of the F1 plants derived from crossing these edited materials with wild type ZJ8 or HHZ were fully restored.
Conclusion Rational design of indica-japonica hybrid breeding can be achieved by using molecular detection and genome editing, enabling rapid cultivation of indica-japonica artificial hybrid-compatible lines and maximizing the retention of genetic diversity in indica and japonica rice. This study provides a new example for breaking the indica-japonica hybrid sterility and utilizing indica-japonica hybrid vigor.