Taxonomic history, morphology, evolution, gene pool and stress tolerances of azuki bean and its related wild genetic resources.

This review compiles information on the morphology, historical taxonomic treatments, species origin, gene pool concept, geographical and ecological habitats, and stress tolerance of the azuki bean () and related species. Willdenow (1802) first described the azuki bean in the genus , and Ohwi and Ohashi (1969) finally transferred it to the genus . The genus is currently divided into five subgenera: , , , , and . The subgenus includes the moth bean in section ; the mungbean and black gram in section ; and the azuki bean, rice bean, and creole bean in section . The wild species in section generally possess larger standard petal with more prominent appendage, keel petal with longer pocket, pistil with longer style beak compared with those of species in sections and , and characterized by glabrous mature pod, smooth seed coat, hypogeal germination seed, and cordate primary leaves with petiole. Section currently consists of 13 species. The taxa that cross readily with the azuki beans included in the primary genepool are the wild azuki bean var. , , , , , , and . These wild species are expected to be used as breeding material against biotic and abiotic stresses.