High-resolution physical mapping in Phaseolus vulgaris (common bean) by fluorescence in situ hybridization

Common bean is the major food legume, especially in Latin America and Africa. Despite its economic importance, relatively little is known regarding its genomic composition and organisation. Few genetic maps have been established to facilitate the isolation of genes of interest, mainly disease resistance genes, but no physical map is available for the species. The first step towards the development of a physical map was the integration of linkage groups to chromosomes. This analysis revealed a lack of correlation between linkage group sizes and chromosome sizes, reinforcing the need of establishing a physical map of common bean. This map would also assist in isolating genes of agricultural importance, as well as genes involved in nitrogen fixation, symbiosis and other biological processes. In the proposed research project, a high-resolution cytogenetic-based physical map will be constructed by hybridizing in situ large insert genomic clones (BACs, bacterial artificial chromosomes), selected with genetically mapped DNA markers, to pachytene chromosomes of the species. This will enable the evaluation of recombination frequencies along each bean chromosome and offer anchoring points for future contig maps. Furthermore, chromosomal markers will be available for comparative studies among species of this genus and closely related genus, such as Vigna (cowpea and mungbean) and Glycine (soybean).