Correlations between grain yield, its components and nutritional traits for cowpea (Vigna unguiculata L. Walp) f1 progenies and their parental genotypes

• Balanced cowpea breeding depends on correlating yield with nutrition. • There was a positive correlation between grain yield and most yield components. • Significant positive correlation between grain yield components and starch content. • Parental genotype IT96D-602 and TVU13953 had progenies with high-yield. • Parental genotype 98K-5301 and Kisumi-mix had progenies with high protein and iron content. Understanding the relationship between grain yield, its components and nutritional characteristics through correlation studies is important for developing cowpea cultivars with improved grain yield and desired nutritional characteristics. The objective of this study was to determine the phenotypic correlations between grain yield, yield components and nutritional characteristics. The yield components and nutritional data were subjected to correlation coefficient analysis, principal component analysis (PCA), and heat map clustering. The results observed a positive correlation between grain yield and all yield components except leaf length, leaf width and days to 50 % flowering, for protein with Fe content and negative correlations of phytic acid with Fe and Zn content. The results indicated that indirect selection of yield can be done through the selection of characteristics highly related to yield. The first two principal components (PC-1 and PC-2) explained 65.85 % of the total variation in the dataset and PCA biplots further grouped the genotypes into four quadrants based on association with measured characteristics. Genotypes IT96D-602 x Glenda, IT96D-602×98K-5301, ITOOK-1060 x TVU13953 and IT96D-602 x TVU13953 were associated with higher grain yield. Genotypes 98K-5301 x Kisumi-mix, Kisumi-mix x Glenda, 98K-5301 x TVU7778 and Kisumi-mix x TVU13953 were associated with high protein content and Fe concentration. The selection of genotypes with a combination of good yield and desirable nutritional characteristics can be beneficial for future breeding activities in South Africa.