Intra- and interchromosomal rearrangements between cowpea [Vigna unguiculata (L.) Walp.] and common bean (Phaseolus vulgaris L.) revealed by BAC-FISH

摘要

Cowpea (Vigna unguiculata) is an annual legume grown in tropical and subtropical regions, which is economically relevant due to high protein content in dried beans, green pods, and leaves. In this work, a comparative cytogenetic study between Vigna unguiculata and Phaseolus vulgaris (common bean) was conducted using BAC-FISH. Sequences previously mapped in Phaseolus vulgaris chromosomes (Pv) were used as probes in Vigna unguiculata chromosomes (Vu), contributing to the analysis of macrosynteny between both legumes. Thirty-seven clones from Phaseolus vulgaris 'BAT93' BAC library, corresponding to its 11 linkage groups, were hybridized in situ. Several chromosomal rearrangements were identified, such as translocations (between BACs from Pv1 and Pv8; Pv2 and Pv3; as well as Pv2 and Pv11), duplications (BAC from Pv3), as well as paracentric and pericentric inversions (BACs from Pv3, and Pv4, respectively). Two BACs (from Pv2 and Pv7), which hybridized at terminal regions in almost all Phaseolus vulgaris chromosomes, showed single-copy signal in Vu. Additionally, 17 BACs showed no signal in Vigna unguiculata chromosomes. The present results demonstrate the feasibility of using BAC libraries in comparative chromosomal mapping and karyotype evolution studies between Phaseolus and Vigna species, and revealed several macrosynteny and collinearity breaks among both legumes.