Common bean (Phaseolus vulgaris L) is the most important and widely cultivated among four other Phaseolus species (scarlet runner, tepary, Lima, year-long bean) following a process of agricultural domestication and adaptation, and is the most important grain legume species in Eastern and Southern Africa.  Common bean originated in Latin America but is now cultivated worldwide in diverse environments. Two major gene pools are recognized: the large-seeded Andean and small-seeded Middle American, which correspond to the crop’s two centers of origin and diversity. Over time, selection of desirable plant and seed types have resulted in a rich diversity of landraces.  A short season crop usually maturing from 65-110 days after planting, common bean exhibits a rich diversity in seed characteristics (size, shape and color), growth habits and adaptation traits.

Introduced to the eastern Africa coast by Portuguese traders in the sixteenth century, common bean quickly became established as a food crop in many environments of Africa. Presently, it is the second most important source of human dietary protein, and the third most important source of calories for over 100 million people in rural and poor urban communities in Africa.  Its protein is cheaper than the animal form, making it highly competitive and important in dietary regimes of poor people in Africa. Many plant parts are cooked -- leaves, green pods, green seed -- but dry grain is the most important product. Per capita bean consumption is highest in Africa, reaching 55 kg /yr in Rwanda and 66 kg/yr in western Kenya. Consumer preferences for seed types, color, shape, and brilliance or seed coat luster of dry bean vary greatly even within a country. However, many consumers also place value upon sweet taste and fast cooking attributes, and varieties that excel in these respects sometimes obtain higher prices than those having the most attractive seed appearance.

Over 4 million hectares of beans are sown each year in Africa.  The two main environments are  the cool highlands of East and Central African countries (including Kenya, Uganda, Tanzania, Rwanda and  Burundi) and the warmer mid-elevation areas of DR Congo, Ethiopia, and several countries of Southern Africa. Production tends to be more intensive where human population density is high, although a significant proportion of production occurs in areas of moderately low populations.  Sole crop, maize-bean, banana-beans and root or tuber crop-bean intercrops are important among the many bean cropping systems in Africa and for which the crop’s rapid maturity and shade tolerance make it particularly suitable.  Production is primarily by smallholder farmers, and especially by women (bean is commonly referred to as a woman’s crop), traditionally for home consumption and now increasingly for income generation. Often, women and men often have different aims in producing the crop, and therefore seek varieties having different sets of characteristics.

Variation in growth habit appears to be continuous from determinate bush, indeterminate and vigorous climbing bean types.  Bush beans are the most predominant types grown in Africa. However, climbing beans, originally restricted to small pockets of higher and more fertile soil in northern Rwanda, northeast DR Congo and Malawi are now spreading to other areas and countries, particularly those where land is limiting and human population density is high.

Of about 9 commercial seed types grown in Africa, the Calima (Rosecoco or mottled red) and the reds (large and small) account for about 50% of the production, primarily because of their high market demand. Other market classes include the navy beans, cream-colored, brown tan, yellow types, purples, white and blacks. Typically, three to six easily distinguished cultivars account for 95% of production in a bean producing community. Diversity is greatest in the Great Lakes Region where beans are produced, marketed and consumed as complex varietal mixtures.  In Rwanda, mixtures average 11 components and may contain as many as 27. Farmers maintain and adjust the mixtures according to growing conditions.

The common bean suffers from several biotic and abiotic production constraints. Biotic constraints in order of descending importance in Africa include angular leaf spot, anthracnose, bean stem maggot, bruchids, and root rots among others.  Major abiotic constraints include nitrogen and phosphorus deficiency, low pH complex and drought. Severity of root rots and bean stem maggot is aggravated by certain abiotic stresses.  Many of the preferred landraces and popular commercial varieties are susceptible to many of these constraints and are targets of the breeding efforts carried out in Africa, and which often draw upon the wider range of germplasm and traits available from Latin America.