An integrated AFLP and RFLP Brassica oleracea linkage map from two morphologically distinct doubled-haploid mapping populations

Genetical maps of molecular markers in two very different F1-derived doubled-haploid populations of Brassica oleracea are compared and the first integrated map described. The F1 crosses were: Chinese kale×calab- rese (var. alboglabra×var. italica) and cauliflower×Brus- sels sprout (var. botrytis×var. gemmifera). Integration of the two component maps using Joinmap v.2.0 was based on 105 common loci including RFLPs, AFLPs and mi- crosatellites. This provided an effective method of pro- ducing a high-density consensus linkage map of the B. ol- eracea genome. Based on 547 markers mapping to nine linkage groups, the integrated map covers a total map length of 893 cM, with an average locus interval of 2.6 cM. Comparisons back to the component linkage maps revealed similar sequences of common markers, al- though significant differences in recombination frequen- cy were observed between some pairs of homologous markers. Map integration resulted in an increased locus density and effective population size, providing a strong- er framework for subsequent physical mapping and for precision mapping of QTLs using substitution lines.