The sweet potato (Ipomoea batatas) is a dicotyledonous plant which belongs to the family Convolvulaceae. Amongst the approximately 50 genera and more than 1000 species of this family, only I. batatas is a crop plant whose large, starchy, sweet tasting tuberous roots are an important root vegetable (Purseglove, 1991; Woolfe, 1992). The young leaves and shoots are sometimes eaten as greens. The sweet potato is only distantly related to the potato (Solanum tuberosum). It is commonly called a yam in parts of North America, although they are only very distantly related to the other plant widely known as yams (in the Dioscoreaceae family), which is native to Africa and Asia.

The genus Ipomoea that contains the sweet potato also includes several garden flowers called morning glories, though that term is not usually extended to Ipomoea batatas. Some cultivars of Ipomoea batatas are grown as ornamental plants.

This plant is a herbaceous perennial vine, bearing alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose color ranges between red, purple, brown and white. Its flesh ranges from white through yellow, orange, and purple.

Origin, distribution and diversity

Sweet potatoes are native to the tropical parts of the South America, and were domesticated there at least 5000 years ago.Sweet Potato, Consultative Group on International Agricultural Research They spread very early throughout the region, including the Caribbean. They were also known before western exploration in Polynesia. How exactly they arrived there is a subject of ongoing research and discussion of various hypotheses involving archaeological, linguistic and genetic evidence.

Austin (1988) postulated that the centre of origin of I. batatas was between the Yucatán Peninsula of Mexico and the mouth of the Orinoco River in Venezuela. The 'cultigen' had most likely been spread by local people to South America by 2500 BC. Zhang et al. (1998) provided strong supporting evidence that the geographical zone postulated by Austin is the primary centre of diversity. The much lower molecular diversity found in Peru-Ecuador suggests that this region be considered as secondary centre of sweet potato diversity.

Sweet potatoes are now cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth.

According to the Food and Agriculture Organization (FAO) statistics world production in 2004 was 127,000,000 tons. The majority comes from China with a production of 105,000,000 tonnes from 49,000 km². About half of the Chinese crop is used for livestock feed.