Genetic variability and heritability estimates of nutritional composition in the leaves of selected cowpea genotypes [Vigna unguiculata (L.) Walp.]

Abstract

Cowpea is indigenous to the African continent and is grown for its leaves and grain in different countries of the world. The objective of this study was to determine the variability and heritability of mineral and crude protein contents in the leaves of selected cowpea genotypes grown in South Africa. The trials consisted of twenty five cowpea genotypes evaluated for two cropping seasons. The combined mean values showed wide genetic variation in the mineral elements evaluated. The mean values of calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), sodium (Na), phosphorus (P), and zinc (Zn) varied from 2.23 to 3.69 mg·kg−1; 6.96 to 14.15 mg·kg−1; 311.30 to 1049.95 mg·kg−1; 1.13 to 1.74 mg·kg−1; 0.36 to 0.70 mg·kg−1; 130.08 to 186.42 mg·kg−1; 126.62 to 307.87 mg·kg−1; 0.27 to 0.39 mg·kg−1; and 27.76 to 43.55 mg·kg−1, respectively. The total protein content varied from 21.39% to 33.45%. The correlation analysis revealed significant degree of association between and among mineral elements and total protein content. Biometrical analysis revealed that the phenotypic variances were higher than the genotypic variances. High values of heritability estimates were also recorded for most of the evaluated traits. The principal component analysis (PCA) showed that the first three principal components contributed 71.93% of total variation among the genotypes. The study revealed that there is an ample genetic variability that can be exploited for use in breeding for nutritional quality in cowpea leaves.