Genetic Diversity in Selected Cowpea Accessions Using Grain Protein, Iron and Zinc Contents

Cowpea is the most important grain legume grown in dry regions of Sub Saharan Africa. The objective of this study was to determine the genetic diversity of grain protein, iron and zinc contents of selected cowpea accessions. A collection of 45 cowpea accessions were evaluated under optimum and late planting dates during 2015/2016 summer cropping season, using 9 x 5 alpha lattice design with three replications. The mineral composition of the accessions was determined using standard Association of Official Analytical Chemists (AOAC) method. The results from combined data showed a wide genetic diversity in total grain protein, iron and zinc contents. The mean values of total protein content varied from 18.73% to 27.88% for combined data respectively. Iron content varied from 26.48 mg/kg to 140.89 mg/kg for the combined data, respectively. Zinc content varied from 36.83 mg/kg to 203.42 mg/kg in combined data, respectively. The correlation method revealed a positive correlated between protein and zinc contents. Results revealed values of phenotypic coefficient variation for most characters were close to the corresponding genotypic coefficient of variation values indicating little environmental effect on the expression of these characters. The highest estimates of broad sense heritability (H2) were obtained for protein, iron and zinc. High heritability estimates along with high genetic advance for iron and zinc contents indicating an additive gene action in its inheritance. Based on Principal Component Analysis (PCA), the first two components explained over 77.48% of genetic variation. The tested cowpea accessions are useful resources for nutritional quality improvement in South Africa.