Vigna is a genus of ca. 100-150 species native in tropical regions (mostly from the Old World). Several species are cultivated for fodder (beans) or, more rarely, as green manure.
Vigna is rather closely related to Phaseolus and many species have names in the latter genus as well. Glycine is also very similar in general appearance. See under these genera for their separation.
Alonso C. & Herrera C.M. (2001) rbcL and legume phylogeny, with particular reference to Phaseoleae, Millettieae, and allies. Syst. Bot. 26: 515-536.
Hanelt P. & Mettin D. (1989) Biosystematics of the genus Vicia L. (Leguminosae).