Full Length Research Paper

Genetic variability of cultivated cowpea in Benin assessed by random amplified polymorphic DNA

A. Zannou^1,2,3*, D. K. Kossou¹, A. Ahanchédé¹, J. Zoundjihékpon⁴, E. Agbicodo⁵, P.C. Struik³ and A. Sanni⁵

¹Faculté des Sciences Agronomiques, Université d’Abomey-Calavi, 01 BP 526 Cotonou, Benin.

²Technology and Agrarian Development Group, Wageningen University, Wageningen, the Netherlands.

³Centre for Crop Systems Analysis, Wageningen University, Wageningen, the Netherlands.

⁴Laboratoire d’Ecologie Appliquée, Faculté des Sciences Agronomiques, Université d’Abomey-Calavi, 01 BP 526, Cotonou, Benin.

⁵Laboratoire de Biochimie et de Biologie Moléculaire, Faculté des Sciences et Techniques, Université d’Abomey-Calavi, 01 BP 526, Cotonou, Benin.

*Corresponding author. E-mail: afiozannou@yahoo.com. Tel.: +229.97.44.92.55.

Abbreviations: AMOVA, analysis of molecular variance; C, central; CTAB, cetyl trimethyl ammonium bromide; NE, North East; NW, North West; SE, South East; UPGMA, unweighted pair-group method using arithmetic averages.

Accepted 24 October, 2008

Characterization of genetic diversity among cultivated cowpea [Vigna unguiculata (L.) Walp.] varieties is important to optimize the use of available genetic resources by farmers, local communities, researchers and breeders. Random amplified polymorphic DNA (RAPD) markers were used to evaluate the genetic diversity in 70 cowpea accessions collected throughout Benin. Nine random primers were screened on 24 accessions to assess their ability to reveal polymorphisms in cowpea and four of them were selected for use in characterizing the total sample. A total of 32 amplified bands were generated by the four primers. The number of loci detected varied from 5 to 11. RAPD profiles were analysed and amplified polymorphic DNA fragments were used to construct a dendrogram, clustering the accessions into nine groups at a similarity index of 71% based on the Unweighted Pair-Group Method using Arithmetic Averages. The genetic diversity among the cowpea cultivars investigated was large and the RAPD proved to be a useful technique to characterise it. Based on the molecular variance, the fixation index suggests a large differentiation of cowpea cultivars in Benin.

Key words: Cowpea germplasm, farmers, local communities, genetic diversity, RAPD, Vigna unguiculata.