Bean Germplasm

Since the mid-1980s, CIAT scientists have introduced improved bean seeds from tropical America—where the crop has its two natural centers of genetic diversity—into the midaltitude and highland areas of central, eastern, and southern Africa.

This work takes place through the national R&D programs that make up the Pan-African Bean Research Alliance (PABRA). The alliance encompasses the Eastern and Central Africa Bean Research Network (ECABREN) and the Southern Africa Bean Research Network (SABRN). These networks, in turn, belong to two regional organisations—the Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) and the Southern Africa Development Council (SADC). The networks receive financial support through a donor consortium that includes the Canadian, Swiss, and US governments.

Nutritionists characterize the common bean as a nearly perfect food because of its high protein content and generous amounts of fiber, complex carbohydrates, and other dietary necessities. New varieties thus offer a powerful means of combating malnutrition in the region. Moreover, as Africa's cities expand, market demand for beans is rising rapidly, creating opportunities for farmers to increase their incomes by producing both grain and high-quality seed. And since the crop is grown mainly by small women farmers, they reap most of the benefits.

Among the first improved beans to win African farmers' allegiance were climbing types of Mexican origin. Introduced in Rwanda during the mid-1980s, the new seeds had been adopted a decade later by about half of Rwandan farmers. High yielding and resistant to disease, climbing beans offered the ideal food solution for a densely populated, land-scarce country.

By means of the regional bean networks, which feature innovative seed systems, climbing bean varieties have since spread to Burundi, Congo, Ethiopia, Kenya, Tanzania, Uganda, and Zambia. Elsewhere in the region, new bush-type bean varieties are also strengthening food security and helping farmers cater to markets.

To provide African partners with new options for helping farmers, CIAT scientists are developing beans with tolerance to drought and low soil fertility. They are also identifying bean germplasm with higher iron and zinc content, as part of a new multi-institutional program of the CGIAR to reduce micronutrient deficiency, which mainly afflicts women and children. If, as bean geneticists expect, the content of these micronutrients can be increased by 50 percent, the nearly perfect food will do even more to improve human nutrition in Africa and elsewhere.

To also help farmers become more competitive, the African bean networks have adopted a new market-driven strategy for bean breeding. Through partnerships between national research institutes, universities, farmer associations, private companies, and NGOs, the networks are tailoring new varieties more closely to the diverse demands of local food markets, inter-African trade, and more distant export markets.

Participatory Plant Breeding

Participatory plant breeding is rapidly becoming the norm in bean research programs across Africa. The shift in thinking began in Rwanda during the late 1980s, when CIAT and Rwanda’s Institute of Agricultural Sciences (ISAR) had major success working with women farmers on the selection and introduction of new bean lines. Since then, gender-sensitive participatory methods have gained wide acceptance in agricultural research across the developing world.

University of Nairobi professor and CIAT bean breeder Paul Kimani, who coordinates this work in the Eastern and Central Africa Bean Research Network (ECABREN), describes the underlying problem with earlier scientist-centered approaches to research: “You think you know exactly what everyone needs. But then farmers don’t take up the new varieties.” What is much better understood and accepted now, he says, is that the breeder must have “intimate knowledge of the customer.”

That shift has paid off. Over the past 16 years, CIAT’s collaborative bean research for Africa has produced a wealth of high-yielding, stress-resistant bean varieties. These products are known to be effective and relevant for small-scale farming, because participating farmers at pilot sites have enthusiastically tested, adopted, and shared them with neighboring farmers.

Malawi is one of several countries that have institutionalized participatory research in bean improvement work during recent years. Farmer evaluations are key ingredients in the complex process of moving from experimental breeding lines to officially released varieties.

Research Impact

Improved Varieties Give Kenyan Farmers more Food and Cash

Farmers in western Kenya have enthusiastically adopted several new varieties of beans that resist root rots and whose yield is more than double that of the commonly grown local varieties susceptible to these diseases. A recent impact study shows one of the new bush beans, called KK 15, was being grown by 80 percent of farmers surveyed in one district and by 42 percent in another. Two other varieties had almost identical adoption rates in both districts, roughly 35 percent and 70 percent. The rate of adoption was highest in Vihiga District, which is one of Africa’s most densely populated regions, with 850 persons per square kilometer. (more information)

Research Highlights

Management of Pythium Root Rots in Intensive Bean Systems in Africa

An intensive effort has been undertaken to solve the problem of Pythium root rots in Africa. As population pressure increases and cultivation becomes more intensive, soil fertility drops and inoculum accumulates. This combination of factors results in serious epiphytotics of Pythium root rots. An integrated approach is being implemented including studies on pathogen diversity; genetic studies on inheritance of resistance; breeding; agronomic practices and soil fertility in an IDM-ISFM context; and farmer schools to promote awareness of the problem and adoption of solutions. A dilution plating method was developed to quantify total inoculum of Pythium spp. in the soil, but this method still requires species classification by colony identification. Twelve species of Pythium were identified and of these, the most prevalent species was P. ultimum var. ultimum followed closely by P. salpingophorum, P. torulosum, and P. vexans. Further screening of advanced lines revealed more resistant materials. Only four climbing beans presented intermediate resistance, but 8 and 10 red mottled types were resistant and intermediate, respectively. Eighteen crosses for multiple traits were initiated to combine the Pythium resistance of MLB-49-89A and RWR 719 with other traits and in a range of grain types. Progeny of another 26 crosses are advancing. Farmyard manure and Calliandra green manure both reduced symptoms of Pythium root rots.

Inheritance of Resistance to Pythium Root Rot

There are extremely few sources of resistant to Pythium root rot with most of the commercial varieties being susceptible. The most affected genotypes are the large seeded of the Andean gene pool. Success in managing the disease, depends on the transfer of resistance into a wide range of commercial and non-commercial market class backgrounds. In studies to determine inheritance of resistance we demonstrated for the first time that resistance to Pythium root rot in five genotypes (RWR 719, MLB-49-89A, SCAM80-CM/15, AND 1055, and AND 1062) was simply inherited, and conditioned by single dominant genes. The resistance genes identified have broader activities as demonstrated by the resistance reactions of the five genotypes across major Pythium species occurring in the region. The populations developed will be used to identify markers that are linked to resistance genes.