Interrelationship between grain yield components and nutritional quality traits in cowpea genotypes

Correlations and path coefficient analysis provide knowledge on trait interrelationships and potential for simultaneous, direct, or indirect selection in plant breeding. The objective of this study was to determine the genetic and phenotypic correlations as well as the path coefficient analysis among grain yield components and nutritional quality traits in cowpea genotypes. Data for grain yield components and mineral elements were collected from 70 cowpea genotypes planted at two environments in 2017/18 and 2018/19 seasons in South Africa. Grain yield had significant (P<0.05) positive phenotypic correlations with number of seeds per pod (SPP), indicating that selection of cowpea genotypes based on SPP could be effective in maximizing grain yield. The heat map showed that grain yield was strongly associated with number of branches (NB), SPP and number of pods per plant. Among the yield components, only SPP showed significant (P<0.05) positive phenotypic correlations with Zn, Mn, and Mg. Grain yield showed no genetic correlations with yield components and nutritional quality traits. Significant (P<0.05) positive genetic correlations were observed between yield components and most of the nutritional quality traits, indicating inherent association among the traits. Path coefficient analysis identified SPP and NB as major contributors to grain yield. The PCA identified cowpea genotypes such as ARC030, ARC011, ARC016, ARC024, NGOII, ARC032, IT90K59, and ARC047 with high grain yield and good nutritional quality traits that can be used further as potential parents for crop improvement through biofortification. The clustered heat map distingished five groups of cowpea genotypes and three of those were associated with good grain yield and nutritional quality traits which could make cowpea a good choice to combat food security and malnutrition in the world.