Evaluation of cowpea germplasm lines for protein and mineral concentrations in grains Ousmane Boukar*, Festo Massawe, Satoru Muranaka, Jorge Franco, Bussie Maziya-Dixon, Bir Singh and Christian Fatokun International Institute of Tropical Agriculture (IITA), PMB 5320, Ibadan, Oyo State, Nigeria Received 24 April 2011; Accepted 20 June 2011 – First published online 22 July 2011 Abstract Cowpea, an indigenous crop to sub-Saharan Africa, is found mainly in the dry savanna regions along with cereals such as millets and sorghum. Cowpea is grown primarily for human consumption of the grains, which are rich in protein, carbohydrates and contain some minerals. The development and deployment of cowpea varieties with higher nutritional value will be of immense benefit to consumers. As a first step in the enhancement of mineral content in cowpea grains, several germplasm lines (1541) of different origins and obtained from the genetic resources unit at IITA were sown in the experimental field in Minjibir, Kano State, Nigeria. The grains were analysed for protein and nine mineral contents. However, in this study, we shall report data on crude protein, Fe, Zn, Ca, Mg, K and P. The data generated from the chemical analysis were subjected to the ‘mixture of normal distributions’ clustering method, which distributed the cowpea lines into nine groups. Groups G7 and G9 contained 174 genotypes and these were characterized by high mineral concentrations. The mean nutri- tional content values for group G9 were 24.7% for protein, and 58.9, 41.5, 1107, 2132, 15,282 and 5664mg/kg for Fe, Zn, Ca, Mg, K and P, respectively. On the other hand, the 363 lines making up groups G2, G3 and G6 showed low amounts of nutrients in their grains. Some of the lines in G7 and G9 would be good as parents to use in breeding programmes that aimed at developing nutrient-dense cowpea varieties. Keywords: cowpea; diversity; mineral composition; nutritional value; Vigna unguiculata Introduction Cowpea is an important grain legume found mainly in the savanna regions of sub-Saharan Africa, where it is grown in intercropping system with cereals such as millets and sor- ghum. This indigenous crop to sub-Saharan Africa thrives relatively better than other crops in the drought-prone areas of the region. The average grain yield of cowpea in the region is estimated to be about 470 kg/ha (FAO, 2008) and the potential yield is up to 2.3 t/ha. Nigeria and Niger Republic are the two highest cowpea producers worldwide at 3.04 million and 0.69 million tons with average yield of 0.69 and 0.17 t/ha, respectively. Cowpea is grown primarily for human consumption of the grains, which are rich in protein, carbohydrates and contain some minerals as well. In many homes in sub-Saharan Africa, cowpea, being a legume, is a major source of dietary protein. Most cowpea varieties being grown contain between 22 and 25% protein in their grains. Following evaluation of eight lines, Bressani (1985) and Elias et al. (1964) reported that cowpea contains 24% protein and about 62% soluble carbohydrates and small amounts of other nutrients. Bliss (1975), however, reported that depending on the geno- type, cowpea grains may contain between 23 and 30% protein. In a study involving 100 improved cowpea breed- ing and germplasm lines, protein content in grains ranged from 22 to 30% (Fatokun, unpublished IITA data). These latter reports reveal genetic differences in protein content *Corresponding author. E-mail: o.boukar@cgiar.org q NIAB 2011 ISSN 1479-2621 Plant Genetic Resources: Characterization and Utilization (2011) 9(4); 515–522 doi:10.1017/S1479262111000815