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Cassava, the king crop
21 May 2007

The International Institute of Tropical Agriculture (IITA) is an Africa-based international research-for-development organization, established in 1967, and governed by a board of trustees. Our vision is to be one of Africa‚Äôs leading research partners in finding solutions for hunger and poverty. We have more than 100 international scientists based in various IITA stations across Africa. This network of scientists is dedicated to the development of technologies that reduce producer and consumer risk, increase local production, and generate wealth. We are supported primarily by the Consultative Group for International Agricultural Research (CGIAR, www.cgiar.org).

The Institute's research and related activities are centred on increasing agricultural production, improving food systems, and sustainably managing natural resources together with stakeholders. Research at lITA covers crop improvement, plant health, and resource management of cassava, cowpea, soybean, maize, banana, and yam within a food systems framework.

In Tanzania, lITA works in collaboration with the Ministry of Agriculture, Food Security and Cooperatives, the Tanzania Food and Nutrition Centre, Sokoine University of Agriculture, nongovernmental organizations (NGOs), farmers groups, and the private sector. The main focus of lITA is on cassava. Tanzania is one of the top five producers of cassava on the continent. FAO estimated Tanzania's cassava production at about 7 million tonnes in 2005. This crop comes after maize in terms of number of households, area planted, and production volume in the country.

Cassava is mostly grown for home consumption because of its usefulness in making several safe food and ability to grow in harsh environments (diseases, drought, or flood). Cassava is rich in carbohydrates. In order to have a balanced diet cassava-based products have to be eaten with other foods, as it is the case for other crops. The perishable crop, if processed safely can be preserved for up to a year. To preserve cassava better and still retain most of its nutritional value, it has to be processed with the right materials and using methods that make it safe for human consumption. IITA has developed modern processing methods and equipment to produce safe cassava products.

Looking beyond cassava as a product for direct human consumption, the resilient crop has a high potential as a money earner. Once processed further, cassava products can profitably be used as a vital ingredient in many industries; more than most crops grown by resource poor farmers in Africa. Cassava is a widely used ingredient in the animal-feed industry (in Europe and Latin America). Its starch is well accepted in the food industry, in the making of adhesives for corrugated cardboard, cartons, and other packing materials, such as fermentable substrates for the production of ethanol or alcohol, and used by pharmaceutical industries as fillers in pills and tablets. In the textile industry, cassava starches are used during warp sizing and cloth finishing altering the "feel" of the fabric. Perhaps the most important of these is the suitability of high quality cassava flour developed by lITA for use in the food manufacturing industry where an estimated US$ 20 million could be saved annually from the imports of substitutes in Taniania. Half of this would be paid directly to resource-poor farmers, processors, and other people that would be involved in the whole value chain including packaging, transportation, distribution, wholesale, retail markets, etc. lITA's interventions aim at empowering farmers with the knowledge skills and equipment as well as markets for the processed cassava products. There is no point in having all these value-added products with no one to buy them. It is for this reason that lITA is facilitating the linkages of farmers to food processing companies and the Institute has been sensitising and training them on how best they can make use of cassava products (e.g,. high quality cassava flour) in the industries.

Cassava is unfortunately threatened by pests and diseases. The most common diseases that affect the growth focus on development of cassava in this region are the cassava brown streak disease (CBSD) and the cassava mosaic disease (CMD). CBSD alone is a serious threat to food security of the country, in particular for the coastal lowlands of Tanzania where yield losses range between 49 and 74% in some districts such as Muheza and Pangani. The estimated economic loss caused by this disease amounts to US$ 16,500,000 per annum for the country. The main symptoms of the disease are first seen in the discoloration of the cassava plant leaves along the leaves veins. In severe cases, the whole leaf takes on a blotchy look. It is usually the lower leaves of the plant that are affected. The symptom on the root maybe external or internal and in some cases both. External symptoms may look like radial constrictions and or pits in the surface bark. Underneath the bark the cortex is necrotic. The internal symptoms are yellow/brown corky patches of the stage tissue and in some cases blue/black streaks. In other cases, the root actually looks healthy on the outside until cut open, revealing the streaks. CBSD was discovered way back in the 1920s under UK's overseas development department which funded research on cassava at the Amani Research Centre in Tanga. Over the years, what was considered a problem of the coastal region has been spreading into the Great Lakes region far west as the Democratic Republic of Congo reaching as far down south as Lake Malawi. It was not until recently that it was discovered that the white fly Bemisia tabaci is a vector of CBSD. The transportation of the cassava cuttings from one location to another accelerates the spreading of the diseases to far flung destinations.

To be competitive, the yields must increase beyond the current averages of 10 tonnes of fresh cassava roots per ha. Hand in hand with adding value to the cassava crop research at IITA in Tanzania also covers the plant seeding development. IITA has contributed focus on developing cassava flour for various uses to the development of new varieties of cassava that are more resilient to major diseases that attack cassava along the coastal areas of Kenya, Mozambique and Tanzania. Currently the seven cassava varieties highly recommended for cultivation in CBSD/CMD affected areas of Tanzania are Kiroba, Kigoma Mafia, Nachinyaya, Kalulu, Kitumbua, Namikonga and Naliendele. Zanzibar recently (15 March 2007) released another four new cassava varieties that are tolerant to CBSD, resistant to CMD, and that meet the preferences of consumers in markets. In addition to roots, cassava leaves are a valuable source of proteins, vitamins, and minerals as a tasty vegetable for human consumption. They can be used in the animal feed industry as well. The new varieties have yield potentials as high as 35 tonnes of fresh roots per ha. IITA applied the community participatory approach in its breeding programs, which is likely to facilitate the spread of the cultivars because farmers' views and needs have been incorporated in the development of new cassava breeds. Working together with development partners (NGOs, farmers' organizations, the private sector) also facilitates the spread of new varieties.

By developing new varieties, information systems and innovative processes in value addition to improve the quality of processed products and reduce losses for cassava, IITA is contributing to the improvement of the cassava subsector in Tanzania. However, those science-based technologies to boost primary production and value addition also require an improved institutional arrangement that would create favorable conditions for the achievement of cassava's commercial potentials. All the stakeholders in the cassava subsector (government officials, members of parliament, industrialists, bankers, development investors, producers, processors, fabricators, bakers, agricultural researchers, media, etc.) must work together to develop the cassava industry. In West Africa, Ghana and Nigeria referred to that institutional arrangement as the Presidential Special Initiatives on Cassava. These programs focus on the simultaneous improvement of the farm productivity through the maximization of agronomic efficiency at the farmers' level, promotion of private sector participation in the production, value addition, commercialization, agroenterprise development, export and import substitution.

A special initiative on cassava sector development in Tanzania adopting a market-oriented strategy, with the necessary policy and institutional support could be used to demonstrate how this crop-based agricultural strategy could lead to improving the economy of a subsector, creating new jobs, and reducing food insecurity. The same strategy could then be applied to other commodities resulting in an overall sustainable economic growth for the country. In line with the vision of the Tanzania's National Strategy for Growth and Reduction of Poverty, IITA is willing to join the Government and its partners in the design and implementation of a new strategy and programs for cassava to play its role as an engine for economic growth, job creation, and food security.

Drs V.M. Manyong, A. Abass, E.
Published by Focus on development, Development News, Vol. 1, Issue 1, 2007