Rice bean (Vigna umbellata) was domesticated in Southeast Asia and is a scientifically neglected crop with under-exploited potential. Isemura et al. compare its domestication QTLs with those of azuki bean (V. angularis) of East Asian origin. The inheritance of domestication-related traits is found to be so simple that a few major QTLs explain the phenotypic variation between cultivated and wild rice bean. Interchange of major QTLs between rice bean and azuki bean might be useful for broadening the genetic variation of both species.