Genetic mapping of nuclear fertility restorer genes for the 'Polima' cytoplasmic male sterility in canola (Brassica napus L.) using DNA markers

Co-segregation of male fertility with DNA markers selected by targeted mapping approaches as being potentially linked to the Rfp1 restorer gene for the pol cytoplasmic male sterility (CMS) was analyzed using two canola (Brassica napus L.) backcross populations. Eleven DNA markers (10 RFLP markers and one RAPD marker) directly linked to the Rfp1 locus were identified. The linkage group containing the Rfp1 locus was found to correspond to B. napus linkage group 18 of Landry et al. (1991). A similar pattern of co-segregation between DNA markers and male fertility was observed in a backcross population segregating for the pol restorer gene Rfp2 from line 'UM2383'; one RFLP marker, cRF1b, showed perfect linkage with both Rfp1 and Rfp2 and detected identical polymorphic fragments in both the Rfp1 and Rfp2 restorer lines. Our findings indicate that restoration of pol CMS is controlled by a single nuclear genetic locus on linkage group 18 and that Rfp1 and Rfp2 are likely allelic.