Spatial Distribution and Genetic Differentiation of Common Bean in Brazil.

Brazil is the leading producer of common bean (Phaseolus vulgaris) in the world. Beans play an important role in the every day nutrition of the country. The Brazilian collection is one of the largest in the world. Furthermore previous research has shown that the two major gene pools - Andean and Mesoamerican - are present in the country. To gain a better understanding of the organization of genetic diversity in domesticated common bean for conservation and breeding purposes, a georeferenced sample of 279 bean landraces from the different bean production regions was evaluated by three main approaches: molecular marker diversity (mainly microsatellites), field phenotypic evaluation of descriptors, and environmental distribution using Geographic Information System (GIS) analysis. Molecular marker diversity analyzed by the STRUCTURE model-based algorithm clearly distinguished the Andean and Mesoamerican gene pools. A further four sub-populations could be identified in the Mesoamerican gene pool based on molecular diversity, morphological descriptors, market types, eco-geographic conditions. A landscape genomics approach identified several markers that were correlated with environmental variables, mainly related to precipitation rather than temperature. The “mulatinho’ market type appeared to be the potentially most drought tolerant among market types. This three-pronged approach towards the characterization of genetic diversity appears to be a very fruitful way of identifying genetic diversity not only for conservation but also for breeding purposes as it leads to testable hypotheses about adaptation to biotic and abiotic factors.