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Cassava Research Project: Improvement of cassava for social and economic benefits |
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“Cassava: A powerful poverty fighter in Africa”
A conference jointly organised by NEPAD and the International Food Policy and Research Institute (IFPRI) in November 2003, strongly recommended that cassava be promoted as a poverty fighter across Africa and was facilitated by a Pan African Cassava Initiative, based on a transformation strategy which emphasizes better markets, better organization of producers for collective action, better increased private sector investment.
NEPAD’s Pan African Cassava Initiative has adopted the theme “CASSAVA - A Poverty Fighter in Africa” because the goal of the initiative is to tap the enormous potential of cassava to work for food security and income generation. The vision of the NEPAD Pan African Cassava Initiative is ‘Increased contribution of cassava as a food security crop and a major source of industrial raw materials for income generation in Africa by 2015’
This initiative is exciting because for the first time there is a shift to the potential economic benefits and income generation with regard to the industrial uses of cassava starch in addition to poverty alleviation.
Cassava, a tropical plant with tuberous roots of the genus Manihot, is not only a valuable source of food in many parts of Africa, but the starch obtained from the tuber has wide industrial applications. However, good crop production is threatened by virus diseases which have proved untreatable through chemical treatment. One of the most important constraints to cassava production in sub-Saharan Africa is virus diseases caused by begomoviruses. These viruses cause Cassava Mosaic Disease (CMD) and result in enormous yield losses. Consequently, farmers are severely affected and it is thus important that approaches are developed to try to control this disease. Cassava is grown as a primary staple food in Africa and a secondary crop in South Africa by smallholders in Mpumalanga, Limpopo and KwaZulu-Natal. It is sold within South Africa or to traders from Swaziland and Mozambique. Starch extracted from cassava tubers (the starch content is 21% to 30%) has many industrial applications, including food processing and in the paper, wood, textile, pharmaceutical, chemical and feed industries. Currently in South Africa 20 000 tonnes of cassava starch is produced commercially. This potentially could be applied in the manufacturing of ethanol. Other advantages of growing cassava are that it can be grown on marginal soils without interfering with land utilised for maize production and cassava starch has a much lower amylose content (17%) than other sources such as the amylopectin waxy starches of maize and wheat. At present, most glucose is produced from maize starch. But if cassava could be introduced successfully, it could become the preferred source for raw material as a result of its higher yield per unit area. In addition, cassava starch is slightly easier to hydrolyse because of its low protein content.
My research involves studying several begomoviruses involved in CMD, including a novel virus (South African cassava mosaic virus) which was isolated in South Africa, in order to understand their biodiversity and evolution. The aim is also to understand how these viruses are transmitted in nature by their whitefly vectors and I am also working with Prof. Judy Brown at the University of Arizona to establish the genetic variation of these whitefly haplotypes in different geographical areas. The work is also critical in trying to develop strategies to control the viruses affecting cassava production.
Another significant aspect of my research is developing genetic engineering strategies to produce transgenic plants that are virus-resistant and with a high starch yield. This project has attracted the interest of Plantbio who have identified cassava as one of their commercial developments in their plant biotechnology portfolio. Another aspect that we are studying is the interaction between begomoviruses and resistant or susceptible host plants (cassava and Arabidopsis) using microarray technology. This project is partially funded by Biopad who awarded us R114 000 for 2005 and 2006.
My cassava research is also sponsored by the Cassava Starch Manufacturing Company, the National Research Foundation. Recently I was awarded a $200 000 from CDR-USAID and $40 000 from USAID through CIAT (Biotechnology for southern Africa) to work on cassava mosaic disease in Mozambique. This project is looking at various epidemiological aspects of CMD as well as selection of potentially virus resistant cassava varieties for field trials. This involves collaboration between me and the University of Arizona, CIAT, University of Jerusalem, and INIA and University of Eduardo Mondlane in Mozambique.
Two of my postgraduate students, Claudia Rossin (MSc.) and Erica Pierce (PhD) will be sponsored for 3-4 months at CIAT in Columbia in 2006 to work on cassava transformation and microarrays, respectively.
More recently, cassava brown streak virus has been found to be critically important in many of the coastal regions of East Africa and northern provinces of Mozambique. I have two students from Tanzania & Kenya who are registered for PhDs with me and will be working in collaborative projects (Dr James Legg and Dr Caroline Herron) on epidemiology and molecular characterization/diversity of cassava brown streak in Tanzania, sponsored by IITA. Another project funded by the Kirkhouse Trust (awarded R360 000 for 3 years) will involve a PhD student from Tanzania and will be co-supervised by myself and Dr. Martin Fregene from CIAT, to work on satellite viruses of cassava begomoviruses. These are important as they can modify disease and therefore need to be examined in light of CMD control strategies.
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