Root and tuber crops like yam, have long served as a source of staple crops to humans. In this post, we will be looking at interesting yam varieties. Besides the well-researched and well-developed members of these crops, that is, potato (Solanum tuberosum), sweet potato (Ipomoea batatas), and cassava (Manihot esculenta), which are consumed in large quantities at a national and at an international level, there are also regionally important root and tuber crops that form the basis of nutrition to some indigenous people. One such example is yam (Dioscorea spp).
It is native to Africa and Asia with tubers that vary in size ranging from the size of a potato to over a meter in length and several kilograms in weight. There are over 600 varieties of yams and 95 percent of these crops are grown in Africa.
| Plant Family | Yam(Dioscorea) |
| Origin | West Africa, Asia |
| Edible Part | Tuber |
| Appearance | Rough and Scaly |
| Shape | Long and cylindrical |
| Propagation | Tuber pieces, vine cuttings |
Cultivated Species of Yam
There are many cultivated species of yam varieties throughout the tropics. They include:
- Dioscorea rotundata
- Dioscorea cayenensis
- Dioscorea alata
- Dioscorea bulbifera
- Dioscorea esculenta
- Dioscorea dumetorum
Discorera Rotundata/Discorera Cayenensis
Dioscorea rotundata and Dioscorea Cayenensis: also known as white yam and yellow yam varieties respectively. These are the most important varieties of yam especially in the western and central parts of Africa. They can grow quite large with vines reaching lengths of up to 12 m. The tubers usually weigh between 2.5 and 5 kg each but can attain weights of as much as 25 kg or even more
Yellow Yam
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White Yam
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Discorera Alata
Dioscorea alata: these yam varieties are believed to originate from Asia and they are also known as winged yam or purple yam. It has the largest distribution worldwide of any cultivated yam. Although it is not grown in the same quantities as African varieties. It is grown in Asia, the Pacific islands, Africa, and the West Indies. Even in Africa, the popularity of water yam is second only to white yam. The vines grow to 10 m or more in length and are freely branching. The tubers are large with purple flesh. The plants normally grow for 8–10 months, and then go dormant for 2–4 months. During dormancy, the aerial stems dieback
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Discorera Bulbifera
Dioscorea Bulbifera: it is appreciated for its bulbils, which form at the base of the leaves and are about the size of potatoes, hence the name ‘air potato’ and weighing from about 0.5 to 2.0 kilograms. It is not grown much commercially since its flavor pales in comparison to that of other yams. However, it is popular in home vegetable gardens because it produces a crop after only four months of growth and continues producing for the life of the vine, as long as two years. The bulbils are however more important food products compared to the yam tubers.
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Discorera Esculenta
Dioscorea esculenta: it is also known as the lesser yam and is arguably one of the first yam species cultivated. It is native to Southeast Asia and not cultivated in large quantities in other parts of the world. Its vines rarely reach more than 3 meters (10 feet) in length and the tubers are fairly small. Because of the small size of the tubers, mechanical cultivation is possible; which, along with its easy preparation and good flavor, could increase the popularity of the ‘lesser yam’ in the future
Discorera Dumetorum
Discorea dumetorum: it is popular in the western parts of Africa and is known as bitter yam for its bitter taste. Its cultivation requires less labour than other yams. Its wild forms may be highly toxic
REFERENCES
http://www.appropedia.org/Root_Crops_37 – General Information on Yam from Appropedia.
http://www.iita.org/yam – General Information on Yam from IITA (Holder of Global Mandate for Yam).
http://www.botanical-online.com/english/yam_dioscorea_alata.htm – Information on D. Alata.