Molecular characterization of latent fertility restorer loci for Honglian cytoplasmic male sterility in Oryza species

In Oryza species, several distinct cytoplasmic male sterility (CMS) systems have been identified. Honglian (HL) is one of the mainstream breeding CMS lines in large-scale commercial production in China and southern Asia. In order to increase restorer diversity, we screened 130 Oryza accessions to find new restorer loci for HL-CMS. We analyzed the restoring ability and the diversity of molecular markers cosegregated with Rf5 (Milyang23) and Rf6(t) (9311) for HL-CMS. Molecular and genetic analyses revealed that eight accessions, including one cultivar and seven wild rice, showed polymerase chain reaction (PCR) patterns different from Rf5 and Rf6(t), and each of them harbored a pair of Rf genes unallelic to Rf5 and Rf6(t) for HL-CMS. Furthermore, Northern blot revealed that the Rf loci in the eight accessions showed three types of processing manners of HL-CMS-related transcripts, including endonucleolytic cleavage, partial endonucleolytic cleavage, and degradation of dicistronic atp6-orfH79 messenger RNA (mRNA). The Rf genes for HL-CMS in AA-genome Oryza species elucidated by genetic and molecular analyses will be highly beneficial to sustainable development of hybrid rice.