Vigna umbellata

Vigna umbellata, previously Phaseolus calcaratus, is a warm-season annual vine legume with yellow flowers and small edible beans. It is commonly called ricebean or rice bean. To date, it is little known, little researched and little exploited.[1][2] It is regarded as a minor food and fodder crop and is often grown as intercrop or mixed crop with maize (Zea mays), sorghum (Sorghum bicolor) or cowpea (V. unguiculata), as well as a sole crop in the uplands, on a very limited area. Like the other Asiatic Vigna species, ricebean is a fairly short-lived warm-season annual. Grown mainly as a dried pulse, it is also important as a fodder, a green manure and a vegetable. Ricebean is most widely grown as an intercrop, particularly of maize, throughout Indo-China and extending into southern China, India, Nepal and Bangladesh. In the past it was widely grown as lowland crop on residual soil water after the harvest of long-season rice, but it has been displaced to a great extent where shorter duration rice varieties are grown. Ricebean grows well on a range of soils. It establishes rapidly and has the potential to produce large amounts of nutritious animal fodder and high quality grain.

The cultivated Asiatic Vigna species belong to the sub-genus Ceratotropis, a fairly distinct and homogeneous group, largely restricted to Asia, which has a chromosome number of 2n = 22 (except V. glabrescens, 2n = 44). There are seven cultivated species within the sub-genus, including mung bean or green gram (V. radiata), black gram or urad bean (V. mungo), adzuki bean (V. angularis) and moth bean (V. aconitifolia) as well as a number of wild species. Artificial crosses have been made between V. mungo and V. umbellata to produce improved mung bean varieties (e.g. Singh et al., 2006).

There are three more or less secondary gene pools within the group: ricebean is closer to V. angularis than to the other species, being in the Angulares group (Kaga et al., 1996, Tomooka et al., 2003).