Isoenzyme variation in the generaPhaseolus andVigna (Fabaceae) in relation to their systematics: Aspartate aminotransferase and superoxide dismutase

Evolutionary variation of aspartate aminotransferase and superoxide dismutase isoenzymes in 14 wild and cultivated species ofPhaseolus andVigna has been studied by electrophoresis and isoelectric focusing in polyacrylamide gel. The American cultivated beans of the genusPhaseolus s. str.,P. vulgaris, P. coccineus, P. lunatus andP. acutifolius, form a homogeneous group with only minor isoenzyme variation. The genusVigna, on the contrary, proves to be heterogeneous in isozyme characters. Several clusters of taxa can be distinguished in close correspondence with modern treatments of the genus. The isoenzyme data support the inclusion of the Asian Azuki beans of subg.Ceratotropis inVigna, but argue against the transfer of the S. American speciesP. adenantha. The cowpea complexV. unguiculata s. lato of sect.Catiang forms an uniform and isolated group, distinct from other sections of subg.Vigna, and shows affinity toPhaseolus s. str. by some isoenzymes. It is suggested to removeV. unguiculata s. lato from subg.Vigna and to recognize it as a separate subg.Catiang (DC.)Jaaska & Jaaska, stat. nov.