Inheritance of resistance to four cucurbit viruses in Cucurbita moschata

The Rf-1 gene restores the pollen fertility disturbed by the BT-type male sterile cytoplasm. Nine restriction fragment length polymorphism (RFLP) markers on chromosome 10, where the Rf-1 gene is located, were converted to PCR-based markers. Genetic analysis was conducted using the nine markers and a segregating population consisting of 1042 plants. As a result, the Rf-1 gene was mapped between S12564 Tsp509I and C1361 MwoI. The genetic distance of the two marker loci was estimated as 0.3 cM. Based on the map information of the Rf-1gene, it will be possible to introduce a limited chromosomal segment of the Rf-1 region derived from a donor into japonica rice varieties efficiently and effectively by marker-assisted selection (MAS). Also, examination of seed purity of hybrid rice varieties and their parental lines will be facilitated. Furthermore, judging from the genetic distance from the Rf-1 locus to S12564 Tsp509I and C1361 MwoI loci, it seems that the Rf-1 gene could be isolated by chromosomal walking from either or both of the two marker loci.