Cowpea

Cowpea (Vigna unguiculata L. Walp.), an annual legume, is one of the most ancient crops known to man. Its origin and subsequent domestication is associated with pearl millet and sorghum in Africa. Cowpea is also commonly referred to as southern pea, blackeye pea, crowder pea, lubia, niébé, caupi or frijole. However, they are all of the species Vigna unguiculata (L.) Walp., which in older references may be identified as Vigna sinensis (L.). The largest production is in Africa, with Nigeria and Niger predominating, while Brazil, Haiti, India, Myanmar, Sri Lanka, Australia, the U.S., Bosnia, and Herzegovina all have significant production. Worldwide, area of production of cowpeas is approximately 10.1 million hectares. Annual global cowpea grain production is now approximately 4.99 million tons (FAO 2008). The largest areas under cultivation are in Central and West Africa.

 

Cowpea is a drought-tolerant crop and thrives in warm weather. It is well-adapted to the drier regions of the tropics, where other food legumes do not perform well. It also has the useful ability to fix atmospheric nitrogen through its root nodules, and it grows well in poor soils with more than 85% sand and with less than 0.2% organic matter and low levels of phosphorus. In addition, it is shade tolerant, and therefore, compatible as an intercrop with maize, millet, sorghum, sugarcane, and cotton. This makes cowpea an important component of traditional intercropping systems, especially in the complex, subsistence farming systems of the dry savannas in sub-Saharan Africa.

 

All parts of the plant that are used for food are nutritious, providing protein, vitamins (notably vitamin B) and minerals. The protein in cowpea seed is rich in the amino acids, lysine and tryptophan, compared to cereal grains; however, it is deficient in methionine and cystine when compared to animal proteins. Therefore, cowpea seed is valued as a nutritional supplement to cereals and as an extender of animal proteins.

 

It is now a broadly adapted and highly variable crop, cultivated around the world primarily for seed, but also as a vegetable (for leafy greens, green pods, fresh shelled green peas, and shelled dried peas), a cover crop, and fodder. The cowpea haulm is also a great source of livestock feed, and therefore of great value to farmers. It also is used as a green manure crop, a nitrogen-fixing crop, or for soil erosion control.

 

Improved cowpea varieties are being cultivated in 63 countries, some of which have been given popular local names such as ‘Vijaya’ (victory) and ‘Varuni’ (breeze) in Sri Lanka; ‘Akash’ (sky) and Prakash (light) in Nepal; ‘Big Buff’ in Australia; ‘Fahari’ (hope) and ‘Tumaini’ (pride) in Tanzania; ‘Bubebe’ (fast growing) in Zambia; ‘Umtilane’ in Swaziland; ‘Dahab El goz’ (gold from the sand) in Sudan; "Dan ITA’ (son of IITA) and ‘Wake Rani’ (dry season beans) in Nigeria; "Asontem’ and ‘Bengpla’ in Ghana; ‘Korobalen’ and ‘Sangaraka’ in Mali; ‘Epace’ in Brazil, and ‘Cubinata’ and ‘Mulatina’ in Cuba.

 

Cowpea research

Every stage in the life cycle of cowpea has at least one major insect pest. Aphids (Aphis craccivora) attack cowpea especially in the seedling stage, flower thrips (Megalurothrips sjostedti) at flowering, pod borer (Maruca vitrata) at flowering and pod formation, a complex of pod-sucking bugs at podding, and the weevil (Callosobruchus maculatus) during seed storage. Cowpea is susceptible to several fungal, bacterial, and viral diseases such as Cercospora leaf spot, ashy stem blight, bacterial blight, blackeye cowpea mosaic potyvirus (BICMV), cowpea aphid-borne mosaic potyvirus (CABMV), and cowpea mosaic comovirus (CPMV). Cowpea plants are also attacked by the parasitic flowering plants Striga gesnerioides and Alectra vogelii. Since cowpea is grown mainly in the dry savanna areas with no irrigation facilities, irregular rainfall, especially early in the season, have adverse effects on the productivity of the crop.

 

Since 1970, the International Institute of Tropical Agriculture (IITA) in collaboration with national agricultural research systems in developing countries and advanced research institutions, has worked on developing and distributing improved cowpea materials and new germplasm lines to over 60 countries. IITA maintains a collection of about 15,000 accessions of cultivated cowpea and 1,500 accessions of wild cowpea relatives in its gene bank. Considerable progress has been made in cowpea breeding, and a range of varieties has been developed, combining diverse plant types and maturity with resistance to several diseases, insect pests, and parasitic weeds. Improved varieties have also been developed for grain and fodder. In addition, varieties have been selected for for intercropping with maize, cassava, yam, millet, and sorghum to benefit smallholder farmers who practice intercropping and use little or no inputs. Among the most promising technologies developed are varieties resistant to Striga, Alectra, aphids, and bruchids, improved storage techniques using solar drying, and the use of botanical pesticides in the field and in storage.