Cowpea is native to central Africa. It is widespread throughout the tropics and in most tropical areas between 40°N to 30°S and below an altitude of 2000 m (Ecocrop, 2009). Cowpea is grown in more than two-thirds of the developing world as a companion or relay crop with major cereals crop (Tarawali et al., 1997). In 1996, the total world area was about 12 million ha, and Africa alone accounted for over 8 million ha, of which about 70% were in West and Central Africa (Singh et al., 1996). In other regions, notably in Australia and Asia, cowpea is primarily a fodder crop, but is also used for green manure or as a cover