Molecular characterization and genetic divergence analysis in cowpea (Vigna unguiculata L. Walp.) using RAPD markers
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Date
2007
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CCSHAU
Abstract
Cowpea (Vigna unguiculata) is a legume crop growing in almost all parts of world
including tropics and subtropics. This study was thus undertaken for the molecular
characterization of selected varieties of Vigna unguiculata and to assess genetic diversity
among them using randomly amplified polymorphic DNA (RAPD) markers. Thirty five
RAPD primers were used to assess molecular polymorphism in twenty four Vigna
unguiculata genotypes. A total of 182 amplified products were obtained out of which 2
were monomorphic and 180 were polymorphic. Average polymorphism across twenty four
genotypes was found out to be 99.35%. For the genotypes tested, 2 to 14 bands were obtained, with an average of 8.27 bands per primer. The size of amplified fragments ranged
from150-2000 bp. Some primers also produced unique alleles in specific cowpea
genotypes which could be used to distinguish them. Analysis of this polymorphism profile,
generated using suitable statistical programmes, grouped the twenty four genotypes into
two major clusters at a similarity coefficient of 0.50. The cluster-I was divided into 2 sub
clusters involving 8 genotypes. Genotype CP-23 was out grouped and formed the 1st sub
cluster of cluster I. The second cluster was again divided into two minor clusters.
Subcluster-I involved two varieties CP-20 and FS68. The next large sub-cluster contained
all the other genotypes. Genetic similarity matrices of the genotypes ranged from 0.3462 to
0.8681, indicating a high genetic variability among the genotypes. Genotypes CP-6 and
CP-7 were genetically most similar with genetic similarity value of 0.8681 while the
genotypes CP-3 and CP-11 were found out to be genetically most diverse, at a value of
0.3462. Similarity value for all other genotypes varied between these two extreme values.
The results indicated that RAPD markers are efficient for identification of Vigna
unguiculata genotypes and for determination of the genetic relationships among them.
Fingerprint data obtained in this study can be further utilized in identification and
development of improved cowpea varieties.
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Keywords
RAPD, Genetic diversity, Vigna unguiculata