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Dioscorea alataalso called ube (), ubi, purple yam, or greater yam, among many other namesis a species of yam (a tuber). The tubers are usually a vivid violet-purple to bright lavender (hence the common name), but some range from creamy-white to plain white. It is sometimes confused with taro and the Okinawa sweet potato 紅芋 ( Ipomoea batatas 'Ayamurasaki'), however D. alata is also grown in Okinawa. Its origins are in the Asian and Oceanian tropics. Some varieties attain to great size. A "Mambatap" greater yam grown in Maprik, East Sepik District, Papua New Guinea around 1939 was in length.
D. alata and D. esculenta were the most suitable for long transport in Austronesian ships and were carried through all or most of the range of the Austronesian expansion. D. alata in particular were introduced into the Pacific Islands and New Zealand. They were also carried by Austronesian voyagers into Madagascar and the Comoros. The center of origin of purple yam is in Philippines, but archaeological evidence suggests that it was exploited in Island Southeast Asia and New Guinea before the Austronesian expansion. Purple yam is believed to be a true cultigen, only known from its cultivated forms. The vast majority of cultivars are sterile, which restricts its introduction into islands purely by human agency, making them a good indicator of human movement. Some authors have proposed, without evidence, an origin in Mainland Southeast Asia, but it shows the greatest phenotypic variability in the Philippines and New Guinea.
Based on archaeological evidence of early farming plots and plant remains in the Kuk Swamp site, authors have suggested that it was first domesticated in the highlands of New Guinea from around 10,000 Before Present and spread into Island Southeast Asia via the Lapita culture at around c. 4,000 Before Present, along with D. nummularia and D. bulbifera. In turn, D. esculenta is believed to have been introduced by the Lapita culture into New Guinea. There is also evidence of an agricultural revolution during this period brought by innovations from contact with Austronesians, including the development of Paddy field. (2025). 9781760461164, ANU Press. ISBN 9781760461164
However, much older remains identified as being probably D. alata have also been recovered from the Niah Caves of Borneo (Late Pleistocene, <40,000 Before Present) and the Ille Cave of Palawan (c. 11,000 Before Present), along with remains of the toxic ubi gadung ( D. hispida) which requires processing before it can be edible. Although it doesn't prove cultivation, it does show that humans already had the knowledge to exploit starchy plants and that D. alata were native to Island Southeast Asia. Furthermore, it opens the question on whether D. alata is a true species or cultivated much older than believed. (2025). 9781902937588, McDonald Institute for Archaeological Research. ISBN 9781902937588 (2025). 9781902937540, McDonald Institute for Archaeological Research. ISBN 9781902937540
Purple yam remains an important crop in Southeast Asia, particularly in the Philippines where the vividly purple variety is widely used in various traditional and modern desserts. It also remains important in Melanesia, where it is also grown for ceremonial purposes tied to the size of the tubers at harvest time. Its importance in eastern Polynesia and New Zealand, however, has waned after the introduction of other crops, most notably the sweet potato.
Purple yam is commonly confused with purple/violet varieties of because of their similarities in color, taste, and culinary uses. However, like other yams, purple yam tends to have a moister texture than sweet potatoes. Purple yams also have higher anthocyanin content than sweet potatoes. They can otherwise be used interchangeably in most recipes.
D. alata has relatively high levels of (486–781 mg/100 g dry matter), which are associated with antinutrient and kidney stone formation.
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