文摘
In indica rice, the HongLian (HL)-type combination of cytoplasmic male sterility (CMS) and fertility restoration (Rf) is widely used for the production of commercial hybrid seeds in China, Laos, Vietnam and other Southeast Asian countries. Generally, any member of the gametophytic fertility restoration system, 50% of the pollen in hybrid F1 plants displays recovered sterility. In this study, however, a HL-type hybrid variety named HongLian You6 had approximately 75% normal (viable) pollen rather than the expected 50%. To resolve this discrepancy, several fertility segregation populations, including F2 and BC1F1 derived from the HL-CMS line Yuetai A crossed with the restorer line 9311, were constructed and subjected to genetic analysis. A gametophytic restoration model was discovered to involve two non-allelic nuclear restorer genes, Rf5 and Rf6. The Rf5 had been previously identified using a positional clone strategy. The Rf6 gene represents a new restorer gene locus, which was mapped to the short arm of chromosome 8. The hybrid F1 plants containing one restorer gene, either Rf5 or Rf6, displayed 50% normal pollen grains with I2-KI solution; however, those with both Rf5 and Rf6 displayed 75% normal pollens. We also established that the hybrid F1 plants including both non-allelic restorer genes exhibited an increased stable seed setting when subjected to stress versus the F1 plants with only one restorer gene. Finally, we discuss the breeding scheme for the plant gametophytic CMS/Rf system.