Integration of A6 in B. rapa and B. napus using SSR markers derived from the same sequenced BACs. Cumulative recombination distances in cM are shown to the left and marker loci to the right of the linkage group. SSR markers developed from sequenced BACs are indicated in boldface. The correspondence between the SSR markers and the BAC clones is given in Additional file 1. The map was constructed using 88 DH plants derived from No. 2127 and ZY821 using BrGMS (boldface) markers and public SSRs as anchors . Markers from the same BAC are connected by lines to indicate the collinearity between B. napus and B. rapa. The B. rapa BraJWF3P and BraVCS-DH linkage maps were redrawn from http://www.brassica-rapa.org. The dotted lines indicated the assignments of previously unassigned BACs.