Comparative study of cowpea germplasm from Ghana and Mali using morphological and molecular markers

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Cowpea improvement can be enhanced by knowledge of the genetic diversity available between and within local and regional genebanks. Genetic diversity in the available gene pool is the foundation of all plant improvement programs. A total 94 accessions (47 from Ghana and 47 from Mali) were used for this study. CRD design was used to evaluate accessions; all stages of the study were done at CSIR-CRI, Kumasi (Ghana). Twelve qualitative and twenty quantitative traits were used to assess the collections on the basis of IBPGR cowpea descriptors. A total of 20 SSRs markers were used to assess polymorphism of the germplasm. The morphological data, results showed a relatively low level of genetic diversity between and within both germplasms (Ghana and Mali) which ranged from 1 to 0.82 and 0.99 to 0.84 for qualitative and quantitative traits respectively. Principal component analysis, similarity matrix, scatter plot matrix and clustering separated the accessions according to some qualitative and quantitative traits. Among the 20 SSRs markers screened, only 6 primer pairs were polymorphic. Seven to twenty-seven alleles per primer were detected with polymorphic information content (PIC) varying from 0.61 to 0.92 with a mean of 0.83; allele frequency from 0.17 to 0.45 with a mean of 0.28; genetic diversity from 0.66 to 0.92 with a mean of 0.84; heterozygosity from 0.00 to 0.97 with 0.47 as a mean. The diversity observed can be exploited by breeders from the two countries for cowpea improvement.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Agronomy (Plant Breeding), August-2012