Assessing the Genetic Diversity in Cowpea (Vigna unguiculata L. Walp) Accessions Obtained from IITA, Nigeria Using Random Amplified Polymorphic DNA (RAPD)

The aim was to assess genetic diversity in cowpea using Random Amplified Polymorphic DNA (RAPD). Twenty cowpea accessions were obtained from International Institute of Tropical Agriculture (IITA), Nigeria and planted in the screening house of the same institute. The seeds were planted in pots filled with top rich soil, arranged in a Complete Randomized Design (CRD). DNA extraction and quantification and RAPD analysis of the DNA was carried out. A dendrogram was constructed using Unweighted Pair Group Method Arithmetic Mean (UPGMA). Analysis of molecular variance (AMOVA) was done. Result revealed 87.03% polymorphism. The major allele frequency ranged from 0.3875-1.0000 while, genetic diversity was from 0.000-0.7313. Polymorphic Information Content (PIC) ranged from 0.0000-0.6934. The result further revealed that the genetic distance across countries ranged from 0.6620-0.9423 showing that the widest distance was cowpea accessions obtained from Nigeria and Benin. The UPGMA based cluster analysis generated dendrogram with six clusters. The dendrogram revealed that accessions obtained from the same continent were clustered together, which was corroborated by the PCoA and AMOVA results. Generally, genetic diversity parameters were higher in the cowpea accessions obtained from the Asian continent when compared with accessions from African origin. It is therefore, reasonable to conclude that there is a wide genetic diversity of the cowpea accessions adopted from the Asian continent by International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria. However, from the UPGMA-based dendrogram, it could be suggested that selection be made on accession Tvu 9696 adopted from Egypt as stock for introgression.