Dioscorea

Dioscorea is a genus of flowering plants in the family Dioscoreaceae. It includes hundreds of species of perennial, twining vines that are native to tropical regions of the Old World and the Americas. The plants are best known for their large, starchy tubers, which are commonly referred to as yams.

Many Dioscorea species produce edible tubers that are important staple foods in parts of Africa, the Caribbean, and Asia. Widely grown edible yams include D. alata (purple yam), D. rotundata (white yam), D. esculenta (lesser yam), and D. cayennensis (yellow yam); D. polystachya (Chinese yam) is also widely cultivated in East Asia.

Morphology varies by species, but most are climbing perennials with twining stems and alternating leaves. The tubers may be large and irregular in shape, forming in the soil or, in some species such as D. bulbifera, as aerial bulbils. Propagation is typically by tubers or bulbils rather than seeds.

The genus is notable for steroidal sapogenins such as diosgenin, which has been used in the manufacture of steroid hormones; this has given certain Dioscorea species economic importance beyond nutrition. In food use, proper processing is usually required to reduce anti-nutritional factors and toxicity in some wild species.

Dioscorea is cultivated across tropical regions and has also become invasive in some non-native habitats due to its vigorous growth and tuber production. The taxonomy and species delimitation within the genus are complex, with ongoing research to resolve relationships among wild and cultivated forms.