Wild-weed-crop complexes of common bean (Phaseolus vulgaris L., Fabaceae) in the Andes of Peru and Colombia, and their implications for conservation and breeding

During germplasm explorations carried out in Peru and Colombia, interbreeding complexes of wild and cultivated common bean were observed in both countries, eight in Apurimac and Cusco departments of Peru and eight in Cundinamarca and Boyaca´ departments of Colombia. The existence of complexes was evidenced both by segregation of wild and cultivated morphological traits in certain populations, and by the presence of genetically stabilized weedy types which were assumed to have arisen from past hybridization. Observations on phaseolin seed protein confirmed that genetic exchange was occurring. Phaseolin types introduced from other regions were in incipient stages of introgression into local populations. On the other hand, local phaseolin types were observed in all phases of the complexes from totally wild to fully cultivated beans, suggesting that the complexes had undergone a long evolution. Complexes could be an effective means to generate genetic variability, introgressing genes from wild populations into cultivated types and complementing modern plant breeding programs. The conservation of such complexes depends on the continued existence of the wild, weedy and cultivated beans in close proximity; on the maintenance of a semi-domesticated environment; and on the willingness of farmers to leave weedy types in the field.