Classification of cassava into ‘bitter’ and ‘cool’ in Malawi: From farmers' perception to characterisation by molecular markers |
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Authors: | Jonathan Mkumbira Linley Chiwona-Karltun Ulf Lagercrantz Nzola Meso Mahungu John Saka Albert Mhone Mpoko Bokanga Leon Brimer Urban Gullberg Hans Rosling |
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Affiliation: | 1. Bvumbwe Agricultural Research Station, P.O. Box 5748, Limbe, Malawi 2. Department of Plant Biology, Swedish University of Agricultural Sciences, Box 7080, SE-750 05, Uppsala, Sweden 3. Division of International Health, Department of Public Health Sciences, Karolinska Institute, SE-171 76, Stockholm, Sweden 4. Nutrition Unit, Department of Medical Sciences, Uppsala University, Dag Hammarskj?lds v?g 21, SE-752 37, Uppsala, Sweden 5. IITA/SARRNET, Chitedze Research Station, Box 30258, Lilongwe, 3, Malawi 6. Department of Chemistry, Chancellor College, University of Malawi, Box 280, Zomba, Malawi 7. International Institute for Tropical Agriculture, Oyo Road, P.M.B, 5320, Ibadan, Nigeria 8. Department of Pharmacology and Pathobiology, The Royal Veterinary and Agricultural University, 13 Bülowsvej, DK-1870, Frederiksberg C., Denmark
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Abstract: | Cassava roots, a major food in Africa, contain cyanogenic glucosides that may cause toxic effects. Malawian women farmers considered fields of seemingly similar cassava plants to be mixes of both ‘cool’ and ‘bitter’ cultivars. They regard roots from ‘cool’ cultivars as non-toxic. Roots of ‘bitter’ were considered to require extensive traditional processing done by women to be safe for consumption. But curiously, these women farmers preferred ‘bitter’ cultivars since toxicity confers protection against theft, which was a serious threat to the food security of their families. We studied how well these farmers comprehend the effects of genetic variations in cassava when dealing with cyanogenesis in this complex system. Using molecular markers we show that most plants farmers identified as belonging to a particular named cultivar had a genotype typical of that cultivar. Farmers' ethno-classification into ‘cool’ and ‘bitter’ cultivars corresponded to a genetic sub-division of the typical genotypes of the most common cultivars, with four-fold higher cyanogenic glucoside levels in the bitter cultivars. Examining morphology, farmers distinguished genotypes better than did the investigators when using a standard botanical key. Undoubtedly, these women farmers grasp sufficiently the genetic diversity of cassava with regard to cyanogenesis to simultaneously benefit from it and avoid its dangers. Consequently, acyanogenic cassava – the breeding of which is an announced good of some cassava genetic improvement programmes – is not a priority to these farmers. Advances in molecular genetics can help improve food supply in Africa by rapid micropropagation, marker assisted breeding and introduction of transgenic varieties, but can also help to elucidate tropical small-scale farmers' needs and skills. This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | cassava cultivars cyanogenic glucosides molecular markers farmers'perception genotype Manihot esculenta |
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