Variability among Accessions of Cowpea (Vigna Unguiculata L. Walp): From Qualitative Scoring to Quantitative Analyses

Genetic variability and inter-character association in 25 accessions of cowpea were studied through their expression of qualitative morphological traits. Accessions were collected from the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan and assessed in the field in a Randomized Complete Block Design (RCBD) with three (3) replications. Twelve (12) qualitative traits were evaluated utilizing 10 plants for each accession per replication. Heritability and Genotypic correlations were estimated with Plant Breeding Tools (PB-Tools) version 1.4. The information were exposed to cluster and Principal Component (PC) analyses utilizing Palaeontological Statistics Software Package for Education and Data Analysis (PAST). All the 12 qualitative traits separated accessions successfully. Heritability for all traits was 100 percent, which showed that in cowpea, the effect of environment on manifestation of qualitative traits is insignificant. The most variable trait was immature pigmentation (84.24%) and the trait with the least variability was leaf colour (20.92%). In the bi-plots, accessions in group I and II which differed to accessions in group IV in important traits such as growth pattern, plant hairiness, pod attachment to peduncle and leaf colour are recommended together with these important traits in cowpea improvement programmes. Conclusively, combination of PCA, bi-plot, cluster analysis and genotypic correlations were efficient in revealing significant relationships among characteristics of cowpea accessions for selection purposes, and are therefore recommended