A consensus linkage map for rapeseed (Brassica napus L.): construction andintegration of three individual maps from DH populations

A framework consensus map for rapeseed (Brassica napus L.) was constructed from the integration of three DH mapping populations derived from crosses b etween or within spring- and winter-type parents. Several sources of geneti c markers were used: isozymes, RFLPs, RAPDs, and AFLPs. A total of 992 diff erent markers were mapped to at least one population, of which 540 were inc luded in the consensus map and 253 were common to at least two populations. Markers were distributed over 19 linkage groups, thus reflecting the basic chromosome number of rapeseed and covered 2,429 cM, which was in the mean confidence-interval estimates of genome length (2,127-2,480) cM. Markers we re evenly spaced on the entire genome even if, for several linkage groups, both RAPID and AFLP markers were not uniformly distributed. In the populati on resulting from a cross between two spring lines, a higher recombination rate was observed and a translocation was identified. The consensus approac h allowed to map a larger number of markers, to obtain a near-complete cove rage of the rapeseed genome, to fill the number of gaps, and to consolidate the linkage groups of the individual maps.