Genetic Diversity within Ghanaian Cowpea Germplasm Based on SDS-PAGE of Seed Proteins

Cowpea (Vigna unguiculata (L.) Walp is an important legume crop in Ghana and is, thus, among the candidate crops for the national crop improvement programme. However, utilisation of germplasm collections (largely local landraces) for crop improvement has been hampered by the existence of duplicates and genetically redundant accessions that are not noticeable by morphological markers. This study examined the genetic diversity within 60 Ghanaian cowpea germplasm on the basis of stored seed protein banding patterns by the sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) techniques. Protein banding patterns were scored for presence and analysed for percent genetic similarities between pairs of accessions. Similarity index and simple matching coefficient indicated a high degree of homogeneity in banding patterns. A dendrogram constructed on the basis of a genetic distance matrix and by unweighted paired group method with arithmetic averages (UPGMA), using the NTSYS-pc programme, resolved the germplasm into three distinct clusters. With the exception of the BTB collections, accession collected by different collecting teams were similar. The seed protein data could be used, together with other data, for the elimination of duplicate accessions and for the setting up of a core collection, to reduce maintenance cost and ensure efficiency in the use of the germplasm.