Mapping of Rice Fertility-Restoring Genes for ID-Type Cytoplasmic Male Sterility in a Restorer Line R68

An F-2 population derived from the cross Zhong 9A/R68 was used to map the fertility-restoring (Rf) gene for ID-type cytoplasmic male sterility (CMS). Two bulks (a fertile bulk and a sterile bulk) were constructed by pooling equal amount of ten highly fertile lines and ten highly sterile lines, respectively. Four hundred and thirteen pairs of simple sequence repeat (SSR) primers, which evenly distributed on 12 chromosomes of rice, were selected for analyzing polymorphisms between the parents and between the two bulks. The primer RM283 on chromosome 1 and the primers RM5756, RM258, RM6100 and RM171 on chromosome 10 were found to be polymorphic between the parents and between the two bulks. These five SSR markers were linked to fertility-restoring genes. A total of 82 excessive sterile lines were selected from Zhong 9A/R68 F-2 population to estimate the genetic distance between five SSR markers and fertility-restoring genes respectively. The results indicated that one Rf gene was linked to RM283 located on chromosome 1 at a distance of 6.7 cM, and the other Rf gene was mapped to the long arm of chromosome 10 flanked by RM258 and RM6100 at the distances of 8.0 cM and 2.4 cM, respectively.