Ecogeographic distribution ofPhaseolus spp. (Fabaceae) in Bolivia

Abstract

WildPhaseolus vulgaris is distributed between northern Mexico and northern Argentina. Analysis of phaseolin and molecular markers (isozymes, Restriction Fragment Length Polymorphisms or RFLPs) indicate that this gene pool consists of two major groups, Mesoamerican and Andean, and a third intermediate group found in northwestern South America. Previous to this study, only four accessions of wildP. vulgaris beans from Bolivia had been collected and their genetic relationship with other wild beans from Latin America was not known. Due to the problem of intense erosion in some areas of Bolivia, it was our objective to survey and documentPhaseolus spp. in this area before their extinction. We conducted a collection expedition in May 1994 in the departments of Cochabamba, Chuquisaca and Tarija. This resulted in collections of four populations ofP. augusti, two of cultivatedP. lunatus and two mixtures of cultivatedP. vulgaris. The first mixture was made of “k’opurus” or beans consumed after toasting, and represented an addition of 17 accessions to the Bolivian collection. The second mixture was made of “porotos” and resulted in the addition of 10 new accessions. Seven germplasm collections of wildP. vulgaris were found, which allowed us to increase the number of known populations of wild common bean for Bolivia. Another accession was found as a wild-weed-crop complex. Seven of these wildP. vulgaris accessions along with another accession from Bolivia collected previously, and a number of P. vulgaris accessions from Mexico (17), Guatemala (3), Colombia (10), Ecuador (6), Peru (17) and Argentina (16) were analyzed with RAPDs. The use of 14 random primers and one SCAR (Sequence Characterized Amplified Region) resulted in 90 bands, of which 83 were polymorphic. This data was used to construct a dendrogram which shows clear separation into three clusters, corresponding to each of the gene pools and an intermediate group. The Bolivian wild P. vulgaris beans grouped with the accessions of southern Peru and Argentina into the Andean gene pool. RAPD analysis of genetic diversity correlated well with genetic diversity obtained with other markers. Moreover, the ease of analysis allowed us to obtain a large number of bands which was conducive to greater sensitivity and identification of geographic subgroups and accessions of hybrid origin.