Allozyme evidence supporting southwestern Europe as a secondary center of genetic diversity for the common bean

Genetic diversity within a common bean (Phaseolus vulgaris L.) collection, comprising 343 accessions from the Iberian Peninsula, was examined using six allozyme markers. Two major clusters corresponding to the Andean and Mesoamerican gene pools were identified. Both gene pools were characterized by specific alleles, with the former exhibiting Skdh(100), Me-100, Rbcs(100) or 98 and Diap-1(100), and the latter exhibiting Skdh(103), Me-100, Rbcs(100) and Diap-1(95). Some accessions from both clusters, deviating from these allozyme patterns, exhibited Skdh(100), Me-100, Rbcs(100) and Diap-1(95) or Skdh(103), Me100, Rbcs100 and Diap-1100 allozyme profiles and were considered as putative hybrids. The levels of genetic variation has not been eroded since the introduction of the common bean from the American centers of domestication to the Iberian Peninsula. Instead, obvious signs of introgression between the two gene pools were observed, mainly among white-seeded genotypes. The intermediate forms adapted to the Iberian Peninsula could have emerged from initial recombination between Mesoamerican and Andean gene pools. The Iberian common bean germplasm is therefore more complex than previously thought, and contains additional diversity that remains to be explored for genetic and breeding purposes. The Iberian Peninsula could be considered as a secondary center of genetic diversity of the common bean, especially the large white-seeded genotypes.