Characterization of mutant cowpea [Vigna unguiculata (L) Walp] lines using random amplified polymorphic DNAs (RAPDs) and amplified fragment length polymorphism (AFLP) markers

Abstract

Phylogenetic relationship and polymorphism was detected in 10 cowpea lines comprising of leaf, flower and stem mutants, their putative parents and an exotic accession using 10 random amplified polymorphic DNAs (RAPDs) and three primer combinations of amplified fragment length polymorphism (AFLP) markers. These mutants were earlier obtained through the probable activities of transposable elements. The RAPD and AFLP markers revealed a genetic diversity of 47 and 31%, respectively, within the cowpea lines used. Genetic distance ranged from 0.05 to 0.30 based on AFLP markers, while it ranged between 0.13 and 0.44 for RAPD markers. Cluster analysis indicated that there are differences in RAPD markers between the various mutants and it grouped an exotic genotype separately. OPC-14 primer had the highest discriminatory capacity (11 polymorphic fragments). The AFLP analysis was able to group two of the flower mutants, leaf mutants and wild types separately. A combined analysis of the two markers gave a similar grouping as was obtained from the AFLP analysis. AFLP was more discriminatory in grouping the plant samples and the exotic line was distinguished based on both markers. Useful heterotic prediction can be done based on the genetic distance between the mutants and their parents. This will further broaden the genetic base of cowpea and enhance the use of these mutants which have some evolutionary significance. In addition, unique allele RAPD_OPC15-500bp can be harnessed in genetic identification of reduced petal mutant. This study further corroborates the discriminatory power of AFLP over RAPDs.

Key words: Vigna unguiculata, amplified fragment length polymorphism (AFLP), randomly amplified polymorphic DNA (RAPD), mutants, transposable elements.