Targeted mapping approaches to identify DNA markers linked to the Rfp1 restorer gene for the ‘Polima’ CMS of canola (Brassica napus L.)

 We have used two targeting approaches pairs of nearly isogenic lines (NILs) and bulked segregant analysis] to identify DNA markers linked to the Rfp1 restorer gene for the pol CMS of canola (Brassica napus L.). We were able to target the Rfp1 locus as efficiently by comparing NILs as by bulked segregant analysis, and it was demonstrated in this instance that double-screening strategies could significantly improve the overall targeting efficiency. The chance occurrence of shared homozygosity at specific unlinked chromosomal regions in the bulks was found to limit the efficiency of bulked segregant analysis, while the efficiency of NIL comparison was limited by residual DNA from the donor cultivar at scattered sites throughout the genome of the NILs. Received: 6 June 1997 / Accepted: 12 February 1998