Molecular analysis of the parallel domestication of the common bean (Phaseolus vulgaris) in Mesoamerica and the Andes.
Dissemination pathways of common bean (Phaseolus vulgaris) cultivars from their areas of domestication to other parts of the Americas were determined using phaseolin type, as determined by 1-dimensional SDS/PAGE. Common bean cultivars of lowland South America exhibited approximately equal numbers of 'S' and "T' phaseolin types. "S" cultivars of that region may have been introduced along a route starting in Middle America and leading into Colombia, Venezuela, and eventually Brazil. "T'phaseolin cultivars in lowland South America may have been introduced directly from the Andes or indirectly by European immigrants. In the southwestern U.S.A., most of the cultivars showed an 'S'phaseolin, confirming the Middle American origin of these cultivars, as suggested previously by the archaeological record. In northeastern U.S.A. and Canada, the 'T" and 'C" phaseolin types were more frequent than the "S" phaseolin cultivars. While most of the former were possibly introduced into that region by European immigrants, most of the latter may have been introduced by the pre-Columbian Indian populations. Seed size analysis revealed that 'T" or "C" phaseolin cultivars had significantly larger seeds than 'S" phaseolin cultivars, as had been observed previously in Middle America and the Andes. The phaseolin types of commercial seed types and of early northeastern U.S. cultivars are discussed.