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 F-1-derived doubl ed-haploid populations of Brassica oleracea are compared and the first inte grated map described. The F-1 crosses were: Chinese kalexcalabrese (var, al boglabraxvar. italica) and cauliflowerxBrussels sprout (var. botrytisxvar. gemmifera). Integration of the two component maps using Joinmap v.2.0 was b ased on 105 common loci including RFLPs, AFLPs and microsatellites. This pr ovided an effective method of producing a high-density consensus linkage ma p of the B. oleracea genome. Based on 547 markers mapping to nine linkage g roups, the integrated map covers a total map length of 893 cM, with an aver age locus interval of 2.6 cM. Comparisons back to the component linkage map s revealed similar sequences of common markers, although significant differ ences in recombination frequency were observed between some pairs of homolo gous markers. Map integration resulted in an increased locus density and ef fective population size, providing a stronger framework for subsequent phys ical mapping and for precision mapping of QTLs using substitution lines.