A high-density genetic map of Sorghum bicolor (L.) Moench based on 2926 AFLP, RFLP and SSR markers

Using AFLP technology and a recombinant inbred line population derived from the sorghum cross of BTx623 x IS3620C, a high-density genetic map of the sorghum genome was constructed. The 1713 cM map encompassed 2926 loci distributed on ten linkage groups; 2454 of those loci are AFLP products generated from either the EcoRI/MseI or PstI/MseI enzyme combinations. Among the non-AFLP markers, 136 are SSRs previously mapped in sorghum, and 203 are cDNA and genomic clones from rice, barley, oat, and maize. This latter group of markers has been mapped in various grass species and, as such, can serve as reference markers in comparative mapping. Of the nearly 3000 markers mapped, 692 comprised a LOD >3.0 framework map on which the remaining markers were placed with lower resolution (LOD <3.0). By comparing the map positions of the common grass markers in all sorghum maps reported to date, it was determined that these reference markers were essentially collinear in all published maps. Some clustering of the EcoRI/MseI AFLP markers was observed, possibly in centromeric regions. In general, however, the AFLP markers filled most of the gaps left by the RFLP/SSR markers demonstrating that AFLP technology is effective in providing excellent genome coverage. A web site, http://SorghumGenome.tamu.edu, has been created to provide all the necessary information to facilitate the use of this map and the 2590 PCR-based markers. Finally, we discuss how the information contained in this map is being integrated into a sorghum physical map for map-based gene isolation, comparative genome analysis, and as a source of sequence-ready clones for genome sequencing projects.