Fine genetic mapping of the nuclear gene, Rf-1, that restores the BT-type cytoplasmic male sterility in rice (Oryza sativa L.) by PCR-based markers

The Rf-1 gene restores the pollenfertility disturbed by the BT-type malesterile cytoplasm. Nine restrictionfragment length polymorphism (RFLP) markerson chromosome 10, where the Rf-1 geneis located, were converted to PCR-basedmarkers. Genetic analysis was conductedusing the nine markers and a segregatingpopulation consisting of 1042 plants. As aresult, the Rf-1 gene was mappedbetween S12564 Tsp509I and C1361 MwoI. The genetic distance of the twomarker loci was estimated as 0.3 cM. Basedon the map information of the Rf-1gene, it will be possible to introduce alimited chromosomal segment of the Rf-1 region derived from a donor intojaponica rice varieties efficiently andeffectively by marker-assisted selection(MAS). Also, examination of seed purity ofhybrid rice varieties and their parentallines will be facilitated. Furthermore,judging from the genetic distance from theRf-1 locus to S12564 Tsp509Iand C1361 MwoI loci, it seems thatthe Rf-1 gene could be isolated bychromosomal walking from either or both ofthe two marker loci.