Biochemical Evidence Bearing on the Domestication of Phaseolus (Fabaceae) Beans I

The genus Phaseolus (Fabaceae) consists of some 50 species, all of which are distributed in the Americas. Four of these contain cultigens. P. vulgaris (common bean), P. lunatus (lima bean), P. acutifolius (tepary bean), P. coccineus subsp. coccineus (runner bean); and P. coccineus subsp, polyanthus (no English vernacular name). Biochemical markers--phaseolin seed storage protein and isozymes--have provided new evidence on the organization of the first three species. Domestication has possibly caused a strong reduction in genetic diversity in P. vulgaris and P. acutifolius. Both P. vulgaris and P. lunatus cultivars result from at least two independent domestications, in Mesoamerica and in the Andes. These two species consist of two gene pools, each of which includes wiM ancestors and their respective cultivated descendants. Our findings suggest the need for additional emphasis on genetic conservation of wild ancestors and their use in breeding programs and for a comparison ofinter-gene pool vs. intra-gene pool crosses in breeding programs.