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Chapter 5 - Yams
- Edited by Dominic Fuccillo, University of Arkansas, Linda Sears, International Plant Genetic Resources Institute, Rome, Paul Stapleton, International Plant Genetic Resources Institute, Rome
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- Book:
- Biodiversity in Trust
- Published online:
- 22 September 2009
- Print publication:
- 28 August 1997, pp 57-66
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Summary
BOTANY AND DISTRIBUTION
Several sections have been described under the genus Dioscorea of family Dioscoreaceae. The main food yams have been grouped as follows:
Section Enantiophyllum
This is the largest section with respect to number of species and food importance (Degras 1993). Members may be further grouped in terms of geography as: Asian - Oceanian species, e.g. D. alata L. (water yam, greater yam, white yam), D. glabra Roxb., D. nummularia Lam., D. transversa Br.; Sino-Japanese species (or species complex), e.g. D. japonica Thumb, (igname de Chine, Chinese yam), D. opposita Thumb., and African species or species complex, e.g. D. cayenensis Lam. (yellow yam), D. rotundata Poir. (white Guinea yam, white yam).
Section Lasiophyton
D. pentaphylla L., D. hispida Dennsdest, D. dumetorum (Knuth) Pax (bitter yam)
Section Opsophyton
D. bulbifera L. (aerial yam)
Section Combilium
D. esculenta (Lour.) Burk. (Chinese yam, lesser yam)
Section Macrogynodium
D. trifida L. (cush-cush yam)
The many species of yams (Dioscorea sp.) have various unique or peculiar characteristics that distinguish them from each other. The principal food species have been described in a series of monographs (Martin 1974a, 1974b, 1976; Martin and Degras 1978a, 1978b; Martin and Sadik 1977). Generally the yam plant comprises a shoot portion made up of a vine with branches, leaves and sometimes bulbils in the axils of the leaves, fibrous roots and an underground storage organ, the tuber. The vine twines clockwise or anticlockwise depending on the species.
Chapter 1 - Cassava
- Edited by Dominic Fuccillo, University of Arkansas, Linda Sears, International Plant Genetic Resources Institute, Rome, Paul Stapleton, International Plant Genetic Resources Institute, Rome
-
- Book:
- Biodiversity in Trust
- Published online:
- 22 September 2009
- Print publication:
- 28 August 1997, pp 1-20
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Summary
Cassava (Manihot esculenta Crantz) is a major food source for more than 500 million people in Africa, Latin America and Asia. Cultivated for its starchy roots, this New World native species claims a world production of 152 million t (FAO 1995), ranking seventh in yield production among all crops and fourth as an important source of calories in the tropics (Cock 1985; Balogapalan et al. 1988). The storage roots form the basic carbohydrate component of the diet and the leaves are consumed as a preferred green vegetable in many parts of Africa, providing protein, mineral and vitamins (Hahn 1989). Two CGIAR Centres, CIAT and IITA, share the mandate for cassava. Genetic diversity of the Manihot genus is eroding in the face of expansion of agriculture in the American tropical lowlands, while in important cassava-growing regions of Africa, hundreds of traditional varieties have been abandoned during the 20th century (Nweke and Polson 1990; Nweke et al. 1994), and newer production regions in Asia tend to rely on single-cultivar plantations.
BOTANY AND DISTRIBUTION
Cassava is a member of the Euphorbiaceae, subfamily Crotonoideae and tribe Manihotae. The genus Manihot contains nearly 100 species of herbs, shrubs and trees among which the production of latex and cyanogenic glucosides is common (Rogers and Fleming 1973; Bailey 1976) and these are grouped into 19 taxonomic sections (Rogers and Appan 1973).
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