Overview of CIP Work in Sub-Saharan Africa
Peter T. Ewell1

Potato and Sweetpotato in Africa
Research in Partnership with National Institutions
Other Activities

Acronyms cited in this section can be found in the section Acronyms and Abbreviations

Sub-Saharan Africa is a large and diverse region. Of its 47 countries, 36 report potato and/or sweetpotato production to the FAO. In the aggregate, food production has failed to keep pace with population growth, and per capita production has declined. Chronic deficits are made up with imports and food aid. According to the World Bank, 21 of the 30 poorest countries in the world—with GNP per capita per year below $430—are in sub-Saharan Africa. Natural environments, cultures, and economic conditions vary markedly among countries. Vast regions are sparsely populated deserts and forests. Semiarid lands, subject to periodic droughts, account for large areas. Both potato and sweetpotato are grown primarily in densely populated, intensively cultivated highland and mid-elevation zones. They play important, contrasting roles in the food systems of the region.

Potato and Sweetpotato in Africa

Potato is a short-season, high-value crop, grown as a cash crop and for household consumption. According to the FAOSTAT database on the Internet, about 400,000 hectares are harvested in sub-Saharan Africa. Potato production reported in Africa as a whole has nearly tripled over the past 35 years, from 1.3 million tons in the early 1960s to 3.7 million tons in 1996. This growth has been consistently and significantly higher than that of the population. This reflects the crop’s growing importance as a food in rapidly growing urban areas.

Broadly speaking, there are three major potato systems:

1. In the densely populated, high-potential highland areas (1,800-2,750 m) of eastern and central Africa, potatoes are grown by small farmers (0.5-2 ha) both for the market and for home consumption. Yields vary between 5 and 20 t/ha, with a mean of 8-10 t/ha. Rates for chemical fertilizer and fungicide use vary widely among countries and production areas, but are generally low because farmers cannot afford chemicals and supplies are unreliable. Seed is obtained primarily from informal, local sources and average seed quality is low. Late blight and bacterial wilt, as well as viruses, cause chronic, significant yield losses.

2. In southern Africa, particularly in South Africa, potatoes are grown on a relatively large scale in the modern farming sector. Irrigation is becoming more important, good-quality seed is available, inputs are used intensively, and average yields are high—from 15 to over 25 t/ha in South Africa.

3. In Cameroon and Nigeria, potatoes are an important smallholder crop in higher areas. Elsewhere in West Africa, the crop is grown on a very small scale as a high-value vegetable, usually under irrigation.

Sweetpotato is an important food security crop grown in almost every country on the continent. Approximately 1.5 million hectares are planted, primarily in rural areas for home consumption. Although the overall growth rate in reported production has fallen behind total population growth, sweetpotato has significant potential for increased use.

Sweetpotato is a low-input crop, easily propagated from vine cuttings, that is grown under a wide variety of conditions, from intensive irrigation to commercial rainfed fields and to millions of small plots in and around fields of other crops, along roadsides, in backyard gardens, and in urban plots. The crop is most important in eastern and central Africa, including Cameroon, in densely populated, intensively cultivated mid-elevation (1,200-1,800 m) areas, slightly lower than where potatoes are grown in most of the same countries. Elsewhere in eastern and southern Africa, sweetpotato is an important secondary food in diets featuring maize and other cereals. The crop is important in certain regions and periods of the year, such as in the “hungry months” when stores are exhausted and the next grain crop awaits harvest. Diets in the lowlands of West Africa are dominated by cassava, yams, and other staples, and sweetpotato plays a minor role.

Research in Partnership with National Institutions

CIP set up its regional program in sub-Saharan Africa in the mid-1970s. The goal has been to work with national potato and sweetpotato research programs and other partner institutions on key issues facing increased production and use. In 1996, nine CIP international and regional scientists were working in the region: five in Kenya, three in Uganda, and one dividing time between Cameroon and Nigeria. These scientists were directly involved in core-funded, collaborative research with national scientists in Kenya, Uganda, Cameroon, Ethiopia, Tanzania, and Nigeria.

Strong links were maintained with other potato and sweetpotato programs through the PRAPACE network for central and eastern Africa and the SARRNET network for the SADC countries of southern Africa. These networks provided the context for CIP’s participation in seed relief and program rehabilitation projects in war-torn Rwanda and Angola. More limited contacts are maintained with countries that are not network members, for the distribution of information and germplasm.

Collaborative research is concentrated in six major project areas:

1. Potato late blight. Late blight is the single most important potato disease in the region, particularly in the tropical highland environment of central and eastern Africa. Temperatures in the major production zones (1,800-2,750 m) are relatively even. The rainfall pattern is bimodal, and inoculum is almost continuously present. Farmers do not have the income to spray fungicides regularly, and the disease causes serious yield reductions in most years. The disease is less significant in the drier areas of southern Africa.

Over the past 20 years, blight resistance has been the principal trait of new varieties adopted by farmers in countries throughout the region. Several advanced clones are near release and are expected to do well, although R genes are present and their resistance is likely to break down eventually. Sets of genotypes from population B, with better horizontal resistance, are in the early stages of selection in Kenya, Uganda, and Ethiopia. As the Global Initiative on Late Blight develops, CIP and its national partners will increase their investments in research, particularly to promote integrated disease management on-farm.

2. Farmer-based potato seed systems in Kenya, Uganda, Ethiopia, and Cameroon. Farmers need healthy seed, which is available on their farms at planting time, in the right physiological state, at a price they can afford. Centralized systems for seed multiplication and certification modeled on those in Europe and North America have proven difficult to implement and maintain in public-sector institutions in Africa. An alternative is to provide selected farmer-multipliers with clean starter seed stock, and support them to become specialized in the multiplication of seed for sale to other farmers in their area. This also provides a mechanism to get new varieties to farmers.

The facilities that CIP developed over many years in collaboration with the Plant Quarantine Station in Kenya for the introduction and testing of germplasm for regional distribution have been converted into a seed unit. The best available varieties are multiplied in vitro as “starter stocks” for seed programs in target countries. Linkages have been developed with NGOs with contacts in pilot potato-producing communities to facilitate selection of suitable farmers, training in seed techniques, and support for constructing diffused-light stores.

3. Integrated disease management for potato. IDM is the only practical approach to bacterial wilt, as the disease organism persists in the soil, is carried by infected seed tubers, and cannot be controlled with chemicals. In Uganda, CIP is collaborating with NARO, the national research institute, in the African Highlands Initiative, an ecoregional program linked with the Global Mountain Initiative. Its purpose is to take a multi-institutional, multicommodity approach to improving resource management in the intensively cultivated high-potential areas of the highlands.

One project is the integrated management of diseases associated with increasing land use intensity and decreasing soil fertility. Bacterial wilt is one of four diseases being investigated. A full-time regional scientist attached to CIP to work on the project has shown that a package of improved rotation, clean seed, tolerant varieties, and improved on-farm sanitation reduces losses, even on very small farms. Strategies for improved management provide an entry point, to encourage farmers to improve their land use management, with immediate payoff in increased potato yields and longer-term payoffs in stable soil fertility.

4. Sweetpotato improvement. From the late 1980s, CIP’s regional program has imported advanced sweetpotato cultivars from throughout the world for distribution and evaluation. At the same time, true seeds produced from crosses made by Uganda’s national program and from elsewhere are being tested at a few locations.

Farmers grow diverse combinations of locally adapted varieties, which tend to be late-maturing and low-yielding. Planting material is exchanged informally among relatives and neighbors, and only a few introduced varieties have become established in sub-Saharan Africa over the past 25-30 years. African farmers are interested in new varieties if they meet certain criteria: high yield, earliness, and persistence of plants in fields so that planting material is available for the next season. Drought-tolerant varieties would permit the expansion of sweetpotato cultivation in drier areas and drier periods in the year. Good taste is very important both for home consumption and for sale in the market. Consumers like roots with high dry matter (usually at least 27-28%) and moderately sweet taste. Resistance to or tolerance of viruses, weevils, and other pests and diseases could help expand the range of the crop and increase yields.

New varieties for new or expanded uses also have significant potential. Most African consumers prefer roots with white or cream-colored flesh. Orange-fleshed varieties can provide significant quantities of vitamin A, which is critically short in the diets of many rural people, particularly children. Preliminary evidence shows that mothers will grow, prepare, and serve new varieties, if they understand the implications for the health of their families. Sweetpotato vines are high in protein and are an excellent forage for animals, particularly for weaning calves and kids. They are currently fed as a by-product, but dairy farmers will plant new varieties with high forage yields specifically for this purpose. Varieties for processing will be planted if secure markets become available.

5. Integrated sweetpotato crop management. The most widespread and damaging pest in eastern and southern Africa, particularly in dry areas and in dry years, is sweetpotato weevil (Cylas spp.), a focus of CIP’s collaborative research. A number of other insects, viruses, and fungal diseases are important in certain areas. Collaborative research in Uganda and Tanzania, with assistance from the Natural Resources Institute, has isolated sex pheromones of all three species found in Africa, and is testing their use for monitoring and possibly mass-trapping. Several cultural practices, such as maintaining an adequate separation between sweetpotato fields, careful hilling, and removal of all residues from plots after harvest, have been shown to reduce damage.

Pilot projects are being established in Uganda to work with farmers to see how these components can be adjusted and combined to provide effective protection against weevil damage. Most successful IPM programs have been adopted by farmers because they help to reduce pesticide applications, thereby reducing costs. As pesticides are not used on sweetpotato except by a small minority of farmers, the challenge is to develop packages that increase yields sufficiently to justify the increased labor, cash costs, and management attention. Broadening the approach to include additional key constraints in an integrated crop management package is a key to success.

6. Expanded postharvest use of sweetpotato. In Africa, sweetpotato roots are consumed almost exclusively in fresh form; most are usually just boiled. In other parts of the world, particularly in Asia, use of sweetpotato as a raw material in the production of processed foods, feed, and industrial products has increased significantly over the past 40 years. The adaptation of known products and processes to African conditions could open up new markets for farmers. The use of a locally grown, low-input crop in processed products could also reduce the countries’ need for food imports to meet the needs of rapidly growing cities.

Collaborative research in Kenya and Uganda has demonstrated that a ready market exists for homemade products such as flat bread (chapatis) and doughnuts (mandazis), which substitute cooked and mashed sweetpotato for a certain proportion of the usual wheat flour. Farmers in some areas cut roots into chips and dry them in the sun to preserve them. These processes are being improved so that the dried chips can be ground into a high-quality flour, which can be easily stored and transported, and used in mixtures with wheat and other flours in baked goods.

Other Activities

CIP’s regional office provides a link between scientists working in national institutions and research throughout the world. Courses, short-term attachments, and study tours provide training in research and analytical techniques. CIP scientists act as advisors for many student thesis projects. Support for networks and a number of bilateral, regional, and multi-institutional projects help ensure that research responds to the needs of potato and sweetpotato farmers in Africa.

1 Regional Representative, Nairobi, Kenya.