Isoenzyme diversity and phylogenetic affinities among the Phaseolus beans (Fabaceae)

Polyacrylamide gel electrophoretic study of 8 isoenzyme systems encoded by 16 putative gene loci in 23 species of American beans of the genus Phaseolus s. str. and in the Asian moth bean Vigna aconitifolia revealed in total 98 allozymes, including 34 taxon-specific and unique, 14 rare-unique and 50 shared allozymes. - P. xanthotrichus var. xanthotrichus and var. zimapanensis differed in allozymes of AAT-A, AAT-D and ADH-C. P. xanthotrichus var. zimapanensis and P. hintonii shared same allozymes of AAT-A and AAT-D, but differed in allozymes of ADH-A and ADH-C. It is proposed to recognize P. xanthotrichus var. zimapanensis in species rank as P. zimapanensis. - P. acutifolius var. acutifolius and var. tenuifolius, except one accession of the latter, differed in allozymes of AAT-D, ADH-C and FDH-A. - Cladistic analysis of the allozymic data as unordered absence-presence characters disclosed in the genus two major monophyletic species clusters: (1)P. polystachyus, P. ritensis, P. maculatus, P. marechalii, P. jaliscanus, P. salicifolius, P. lunatus, P. filiformis, P. angustissimus, P. acutifolius, P. coccineus, P. vulgaris, P. parvulus, P. pauciflorus, and P. pluriflorus; (2) P. grayanus, P. neglectus, P. pedicel latus, P. microcarpus, P. hintonii, and P. zimapanensis. P. xanthotrichus s. str. and P. zimapanensis are discriminated as paraphyletic, supporting their specific delimitation. Phenetic analysis of the allozyme data with the UPGMA clustering revealed essentially the same pattern of genetic affinities between the species and additionally clarified the extent of allozymic divergence by taking into account species-specific and unique allozymes.