Dioscorea alata, known as purple yam, ube or many other names, is a species of yam, a tuberous root vegetable. The tubers are usually vivid violet to bright lavender in colour, hence the common name, but they may sometimes be plain white. It is sometimes confused with taro and the Okinawa sweet potato (Ipomoea batatas cv. Ayamurasaki), although D. alata is also grown in Okinawa where it is known as Template:Nihongo. With its origins in the Asian tropics, D. alata has been known to humans since ancient times.<ref name=grin>Template:GRIN</ref>
Because it has become naturalized throughout tropical South America, Africa, Australia, the southeastern U.S., D. alata has many different common names from these regions. In English alone, aside from purple yam, other common names include greater yam, Guyana arrowroot, ten-months yam, water yam, white yam, winged yam, or simply yam.<ref name=grin/> In other cultures and languages it is known variously as ratalu or violet yam in India, rasa valli kilangu (இராசவள்ளிக்கிழங்கு) in Tamil, dandila (දන්දිල) in Sinhala, ube in the Philippines, thuppa genasu (ತುಪ್ಪ ಗೆಣಸು) in Kannada, thoona or soona kerungu (ತೂ/ಸೂಣ ಕೆರುಂಗು) in Tulu, kondfal (कोंदफळ) in Marathi, kachil (കാച്ചില്) in Malayalam, and khoai mỡ in Vietnam. For the Igbo people of southern Nigeria, it is called ji or ji abana; while for the Yoruba people of the southwestern Nigeria, it is called isu ewura.<ref name="ogundele">Template:Cite journal</ref>
*qube / *ʔube can be reconstructed as the Proto-Malayo-Polynesian word for D. alata,<ref>Template:Cite web</ref> and words descended from it are found throughout the geographic range of this widespread language family, though in some daughter languages they are generalized or transferred to other root crops. Examples include Tagalog and Visayan ube or ubi, Malaysian and Indonesian ubi**, Malagasy ovy**, Fijian uvi, Tongan Template:Okinaufi, Samoan ufi**, as well as Māori and Hawaiian uhi. D. alata was one of the canoe plants that the Polynesians brought with them when they settled new islands.
** Not specific to D.alata
Purple yam is used in a variety of desserts, as well as a flavor for ice cream, milk, Swiss rolls, tarts, cookies, cupcakes, cakes and other types of pastries. In the Philippines, it is known as ube and is often eaten boiled, baked, or as a sweetened pudding called ube halayá; the latter is a popular ingredient in the iced dessert called halo-halo. In Maharashtra, the stir-fried chips are eaten during religious fasting.Template:Citation needed Purple yam is an essential ingredient in Undhiyu.<ref>Degras, L. 1993. The Yam: A Tropical Root Crop. London, New York, and Wageningen</ref> Purple yam is a popular dessert in Jaffna, Sri Lanka. Ube has more recently appeared in American restaurants as well. It is being used to make truffles, leche, flan, donuts,<ref>Template:Cite web</ref> cupcakes, and other pastries.
D. alata is valued for the starch that can be processed from it.<ref name=grin/>
In folk medicine, D. alata has been used as a moderate laxative and vermifuge, and for fever, gonorrhea, leprosy, tumors, and inflamed hemorrhoids.<ref name=jad>Template:Cite web</ref> D. alata has relatively high levels of oxalates (486–781 mg/100 g dry matter).<ref name="pmid7971785">Template:Cite journal</ref>
The color of purple varieties is due to various anthocyanin pigments.<ref name="mori">Template:Cite journal</ref> The pigments are water-soluble, and have been proposed as possible food coloring agents.<ref name="LiZhang">Jinwei Li, Lianfu Zhang, and Yuanfa Liu (2013) "Optimization of Extraction of Natural Pigment from Purple Sweet Potato by Response Surface Methodology and Its Stability" Journal of Chemistry, volume 2013, article ID 590512, 5 pages Template:Doi</ref>
D. alata is sometimes grown in gardens for its ornamental value.<ref name=grin/>
As an invasive species
Dioscorea alata is native to Southeast Asia, as well as surrounding areas (Taiwan, Ryukyu Islands of Japan, Assam, lowland areas of Nepal, New Guinea, Christmas Island). It has escaped from its native growth area and into the wild in many other places, becoming naturalized in parts of southern and east-central China, Africa and Madagascar, the Western Hemisphere, and various islands in the Indian and Pacific oceans.<ref>
- Kew World Checklist of Selected Plant Families
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- Demissew, S. & Nordal, I. (2010). Aloes and other Lilies of Ethiopia and Eritrea, ed, 2: 1-351. Shama Books, Addis Ababa, Ethiopia.</ref> It persists in the wild in the United States in Louisiana, Georgia, Alabama, Florida, Puerto Rico, Haiti, and the U.S. Virgin Islands. It is considered an invasive species, at least in Florida.<ref name=plants>Template:Cite web</ref><ref>Biota of North America Program, 2013 county distribution map</ref>
- Sri Lanka Rasa Valli Pudding
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- Images from Forestry Images (webpages from the University of Georgia's Center for Invasive Species and Ecosystem Health)