Cowpea (Vigna unguiculata)
Cowpea is a food and animal feed crop grown in the semi-arid tropics covering Africa, Asia, Europe, the United States, and Central and South America. It originated and was domesticated in Southern Africa and was later moved to East and West Africa and Asia.
The grains contain 25% protein and several vitamins and minerals. The plant tolerates drought, performs well in a wide variety of soils, and being a legume replenishes low fertility soils when the roots are left to decay. It is grown mainly by small-scale farmers in developing regions where it is often cultivated with other crops as it tolerates shade. It also grows and covers the ground quickly, preventing erosion.
The name “cowpea” probably derives from when it was an important livestock feed for cows in the United States.
Cowpea’s high protein content, its adaptability to different types of soil and intercropping systems, its resistance to drought, and its ability to improve soil fertility and prevent erosion makes it an important economic crop in many developing regions. The sale of the stems and leaves as animal feed during the dry season also provides a vital income for farmers.
More than 7.4 million tons of dried cowpeas are produced worldwide (2017), with Africa producing nearly 7.1 million. Nigeria, the largest producer and consumer, accounts for 48% of production in Africa and 46% worldwide. Africa exports and imports negligible amounts.
More than 12.5 million hectares are harvested worldwide, 98% of which is in Africa. Nigeria harvests 3.7 million hectares annually. The crop can be harvested in three stages: while the pods are young and green, mature and green, and dry.
All parts of the cowpea crop are used as all are rich in nutrients and fiber. In Africa, humans consume the young leaves, immature pods, immature seeds, and the mature dried seeds. The stems, leaves, and vines serve as animal feed and are often stored for use during the dry season. Fifty-two percent of Africa’s production is used for food, 13% as animal feed, 10% for seeds, 9% for other uses, and 16% is wasted.
Regional preferences occur for the different seed size, color texture of seed coat. For example, Ghanaians are willing to pay a premium for black-eyed peas, while Cameroonians would lower their prices for them.
More than 4 million tons of peas of all sorts are consumed worldwide, with 387,000 tons consumed in Africa.
The cowpea plant is attacked by pests during every stage of its life cycle. Aphids extract juice from its leaves and stems while the crop is still a seedling and also spread the cowpea mosaic virus. Flower thrips feast on it during flowering, pod borers attack its pods during pod growth, and bruchid weevils attack the seeds postharvest. The plants are also attacked by diseases caused by fungi, bacteria and viruses. Parasitic weeds—Striga and Alectra—choke the plants growth at all stages and nematodes prevent the roots from absorbing nutrients and water from the soil.
Most cowpea crops are rain fed and although it is drought tolerant, cowpea farmers in the dry savanna areas of sub-Saharan Africa obtain low yields, estimated at about 350 kg per hectare.
IITA scientists have developed high yielding varieties that are early or medium maturing and have consumer-preferred traits such as large seeds, seed coat texture and color. A number of the varieties have resistance to some of the major diseases, pests, nematodes, and parasitic weeds. They are also well-adapted to sole or intercropping.
Following more than two decades of research, field trials, and risk assessment by multiple organizations, on 29 January 2019, the Nigerian Biosafety Management Agency (NBMA) approved the commercial release of genetically modified cowpea to farmers in Nigeria. NBMA’s approval allows the Institute for Agricultural Research (IAR) to commercially release Pod Borer-Resistant Cowpea (PBR Cowpea)-event AAT709A, genetically improved to resist the pod borer (Maruca vitrata).
Improved varieties have been released to 68 countries in all of the world’s regions. Additionally, IITA’s Farmer Field School (FFS) projects, in collaboration with partners, have trained farmers in improved pest management practices of cowpea crops.
The IITA genebank holds the world’s largest and most diverse collection of cowpeas, with 15,122 unique samples from 88 countries, representing 70% of African cultivars and nearly half of the global diversity.
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Effect of drought and plant density on radiation interception, radiation use efficiency and patitioning of dry matter to seeds in cowpea
Craufurd, P.Q. & Wheeler, T.R. (1999). Effect of drought and plant density on radiation interception, radiation-use efficiency and partitioning of dry matter to seeds in cowpea. Experimental Agriculture, 35(3), 309-325.
Nematode attack on cowpeas in Nigeria
Caveness, F.E. (1973). Nematode attack on cowpeas in Nigeria: proceedings of the First IITA Grain Legume Improvement Workshop, 29 October-2 November, 1973. Ibadan, Nigeria: IITA, (302p.).
Epidemiology and control of cowpea mosaic in Western Nigeria
Glimer, R. (1973). Epidemiology and control of cowpea mosaic in Western Nigeria: proceedings of the First IITA Grain Legume Improvement Workshop, 29 October-2 November, 1973. Ibadan, Nigeria: IITA, (1p.).