Molecular Characterization of Common Bean (Phaseolus vulgaris L.) Genotypes Using Microsatellite Markers

Common bean (Phaseolus vulgaris) is one of the most important legume crops, but the knowledge on genetic diversity of the genotypes grown in Kenya is limited. The objective of this study was to determine the genetic diversity of common bean genotypes from different growing regions (Eastern, Central, Rift Valley, Nyanza and Western) in Kenya using simple sequence repeat (SSR; microsatellites) markers. Using five SSR primers across 40 genotypes, a total of 366 alleles were amplified, with an average of 4.5 alleles per locus. The polymorphism information content (PIC) of the SSR markers ranged from 0.48 to 0.74 with an average of 0.60. The pair wise genetic similarity between common bean genotypes ranged from 0.15 to 1.0 with an average of 0.54. A dendrogram based on the unweighted pair-group method with arithmetic mean (UPGMA) grouped the 40 genotypes into two major clusters. It was notable that the first major cluster was further divided into two-separate sub-clusters, representing genotypes from each of the regions. Principal component analysis (PCA) of the SSR markers showed that the first two principal components (PCs) explained a total of 28.79% of the genetic variation and failed to distinguish significant groupings among the 40 bean genotypes. Analysis of molecular variance (AMOVA) revealed high levels of genetic variation (87%) within population, compared to the variation that exists among the populations. This study demonstrated the existence of considerable genetic diversity in common bean genotypes cultivated in Kenya and can be used as a foundation for future breeding programs to produce hybrids of desirable traits. The wider genetic diversity is important for future generations so that it copes with unpredictable climate changes and human needs.