Evaluation of genetic diversity in agronomic traits among dual-purpose cowpea genotypes in Kenya

Abstract

Availability of diverse genetic materials is central in any plant breeding programme. Genetic diversity is important in ensuring survival of a species; and buffering of crops from climate change effects through crop improvement programmes. The objective of this study was to determine the genetic diversity among a panel of dual purpose cowpea (Vigna unguiculata L.) genotypes to inform crop breeding programmes in Kenya. The study was conducted at the Jomo Kenyata University of Agriculture and Technology (JKUAT) Demonstration Farm in Kenya; during four cropping seasons (2021-2022). A total of 224 dual-purpose cowpea (Vigna unguiculata L.) genotypes were evaluated using an alpha lattice design with two replications. Data were recorded on agronomic traits, and were subsequently subjected to correlation and principal component analysis (PCA), biplot and hierarchical cluster analyses. Total grain yields positively correlated (P<0.05) with grain yield per row and pods plant-1. Principal component analysis dissected total variation into three components, namely PC1, PC2 and PC3. The first three PCs (with eigenvalues >1), accounted for 71.6% of the total variability among the accessions. PCA and Bi-plots showed that pods plant-1, grain yield plant-1 and per row were the best (farthest from the origin indicating largest divulgence) agronomic traits for selection towards improvement of Kenyan dual- purpose cowpea genotypes. The dendrogram also grouped the genotypes into three clusters, namely I (101), II (53) and III (70). There was congruence between the PC and hierarchical cluster in grouping the accessions, based on the Euclidean distance; with the highest values to be used for genetic improvement. The genotypic and phenotypic differences among the accessions could be leveraged as a basis for genetic improvement, through selection and crossing of parents with desired phenotypic traits in future breeding programmes.