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Background Information on Cowpea
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Xylocopa caffra
(carpenter bee) on wild cowpea |
Cowpea (Vigna
unguiculata) is a tropical legume crop of African origin. The species
includes a dozen of infraspecific taxa (all African), either from forest
or savanna ecologies. One of them, Vigna unguiculata var. spontanea
(also known as subsp. dekindtiana sensu Verdc.) is the progenitor of the
domesticated cowpea. Domestication occurred in the savanna regions of
Africa north of the Equator, and cowpea seed remains dating to 1500 BC
have been discovered in Ghana.
 Whether
domestication occurred in the central or eastern part of this savanna belt
is not yet clearly established. Greatest morphological diversity of
domesticated cowpea is indeed in West Africa, while molecular diversity
seems to be higher in North-east Africa. With the help of carpenter bees
(genus Xylocopa) and leaf-cutter bees (Megachilids), cultivated cowpea has
been shown to cross regularly with wild cowpea growing on the periphery or
within fields, especially in West Africa where cowpea is often cultivated
primarily for fodder. As a result of hybridization, almost continuous
variation exists in West Africa between the more elite, large-seeded
varieties of cultivated cowpea, the small-seeded, more weedy varieties,
and true wild species of cowpea.
 Cowpea
is an extremely resilient crop, and is cultivated under some of the most
extreme agricultural conditions in the world.
Cowpea varieties grown in the Sahel and on the fringes of the
Sahara are drought and heat tolerant.
Other cultivars are tolerant to acid soils, extremely poor soil
fertility, and shading from other crops.
Cowpea’s highly diverse plant architecture has allowed farmers to
development varieties which fill a wide range of unique niches:
highly determinate cowpea varieties are grown for grain in
monoculture situations, while spreading types are grown as a dual-purpose
(grain/fodder) crop inter-planted with cereals, and as a relay crop using
residual moisture.
Cowpea
is cultivated for its leaves, green pods, grain and stover.
While all parts of the plant are used to some degree in each region
of the continent, in west Africa cowpea is primarily grown for its grain
and stover (cowpea haulms contain 20% protein and are highly sought after
as cattle feed), while in eastern and southern Africa it is cultivated
primarily for its leaves. Cowpea
grain is consumed directly following boiling, as a component of meals
which also include porridge made from cereals or root crops.
Cowpea grain cakes (made from mashed and fried seed) are also sold
as a fast food along roadsides in Nigeria.
In eastern and southern Africa, cowpea leaves are commonly added to
sauces and served with porridge, or boiled and consumed in a manner
similar to spinach.
Current
estimates place annual world cowpea grain production at 3 million MT
(Singh et. al., 1997). Approximately 64% of this is grown in west and central
Africa, which accounts for 80% of total production in Africa. Nigeria, in turn, accounts for upwards of 75% of production
in west and central Africa (FAO, 1999). However, it is also an important
crop in marginal areas of eastern and southern Africa in Sudan, Somalia,
Mozambique and southern Zimbabwe. Most
cowpea is grown as an intercrop with cereals, and little of the harvest
reaches regional markets. The
sole important export market for cowpea is believed to be from Niger to
Nigeria, which is the world’s largest consumer of cowpea.
The
central challenge to increasing cowpea yields in Africa is most probably
insect resistance. Cowpea
suffers from a wide range of insect pests, including bruchids, Maruca pod
borers, and thrips.
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