Yams are starchy staples in the form of large tubers produced by annual and perennial vines grown in Africa, the Americas, the Caribbean, South Pacific and Asia. There are hundreds of wild and domesticated Dioscorea species. White Guinea yam, D. rotundata, is the most important species especially in the dominant yam production zone in West and Central Africa. It is indigenous to West Africa, as is the Yellow yam, D. cayenensis. Water yam, D. alata, the second most cultivated species, originated from Asia and is the most widely distributed species in the world.