African Legumes—A Vital but Under-Utilized Resource

In recent years, African agriculture and forestry has become more reliant on non-native species. However, indigenous plants are arguably better suited for Africa’s environment. The ability to fix gaseous nitrogen makes nodulated legumes especially well-adapted to drought and low soil nutrients. Sprent et al. (2009) review selected case studies of native African legumes in an effort to analyze ways in which modern methods can improve plant productivity. In particular, the review focuses on cowpea (Vigna unguiculata), rooibos (Aspalathus linearis), and several honeybush (Cyclopia sp.), as well as, additive gum arabic (Acacia senegal). The range of products derived from these plants can be used to alleviate poverty in Africa through food and income generation. Anastasia Kostioukova
Sprent, J., Odee, D., Dakora, F., 2009. African legumes: a vital but under-utilized resource. Journal of Experimental Biology 61, 1257–1265.

Traditionally, cowpea (Vigna unguiculata) is used as a human food crop, and has uses in medicine and animal feed. On the African continent, there are many different lines of nodulating cowpeas along a wide-range of nitrogen fixation ability. Some types are more efficient than others, and therefore breeding programs should extract germplasm from the best performers. Cowpea is especially rich in iron, and can be used to alleviate malnutrition in Africa. The protein rich Bambara groundnut (Vigna subterranea), similar to the peanut, is a balanced source of food as well. Some legumes in this genus have other special qualities. Beach pea (Vigna marina) grows in saline coastal areas. Salinity is, like drought, an increasingly global problem. Germplasm resistant to salinity could provide salinity tolerance in same subgenus crops. Further, some species in Vigna have tubes facilitating storage of nutrients and water. These organs are a useful trait in an increasingly dry and infertile world. Africa has a vast array of indigenous legumes, ranging from large rainforest trees to small annual herbs. The authors suggest that further studies done on the plants in the Vigna genus will be beneficial for targeting issues of malnutrition and food insecurity.
Gum arabic (Acacia senegal) is important for a wide variety of uses in the food industry, as well as for medicine and paper production. The authors only considered the variety senegal in detail as it produces the bulk of current gum production. Traits of the plant such as gum quality and amount produced should be improved if Africa hopes to sustainably grow and export gum arabic however. Further, Sprent et al. suggest reducing dependence on nitrogen fertilizers by identifying species most efficient in nitrogen fixation. However, this will be a daunting task without technological advances. Besides gum for food additives, growers should focus on health beverages for export. Important for the South African economy are unfermented legume teas made of rooibos (Aspalathus linearis) and several honeybrush (Cyclopia) species. Legume teas are low in tannins, but high in anti-oxidants. Unlike fermented tea, unfermented tea retains most nutrients and satisfies the increasing global market demand for healthy products.

Legume teas, adapted to growing in unfavorable conditions, are also used for cosmetics and pharmacological products. Breeding programs should breed in accordance to best quality and quantity of tea produced. Only ‘red type’ rooibos is used for the commercial production of tea. While having nitrogen-fixating nodules, this species can also grow in extremely poor acid soils, and has cluster roots and mycorrhizas that help nutrient uptake. Further, wild honeybrush fixes up to 90% of own nitrogen, while commercial cultivators fix less. The authors suggest focusing on taking wild germplasm and transforming it into acceptable agronomic variety for export. Africa’s Cape Floristic Region (CFR) is a biodiversity hot spot, perfectly suited for recruitment of wild materials. Varying climate and geomorphology results in numerous small areas with unique combinations of character, such as soil pH and nutrient content. CFR has a high level of endemism, and has evolved families with genera and species found only in this region. Diversity of host legumes is accompanied with a diversity of nodulating bacteria found on the roots of such plants. These can be developed further by breeding programs into legumes adapted to drought, contributing both to future climate instability management and growing efficiency. 

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