Evaluation of Genetic Diversity in Strychnos henningsii Selected from Nine Populations in Kenya Based on RAPD Markers

Abstract

Strychnos henningsii is a traditional medicinal plant distributed throughout the tropical and subtropical areas. It belongs to the family Strychnaceae but formally in the family Loganiaceae. In order to understand the genetic variation across the populations and geographical regions of this plant, RAPD markers were used to assess the genetic diversity in nine populations of this species in Kenya. Two hundred and seventy samples were randomly selected from the nine populations, each comprising thirty individuals. The genetic variation within and among populations was evaluated using RAPD Primers. RAPD markers detected an average of 38.97% polymorphism in all populations studied. The most polymorphic population revealed was Kitui with 75 (55.15 %) polymorphic loci, while Baringo was the least polymorphic population with 25 (25.74%) polymorphic loci detected. The markers also revealed twenty-five specific population loci, which could be responsible for specific population traits. A higher molecular variance was revealed among the population (54%; p<0.001) than within populations 46%; p<0.001). According to Nei’s unbiased genetic matrix, the most genetically close populations were Taita-Taveta and Kitui with the highest genetic identity of 0.955, while Ngong and Baringo populations were the most genetically distant populations with a genetic identity of 0.836. Clustering analysis grouped the nine populations into two groups. Cluster I comprised Kitui, Taveta, Karura, Marsabit, Ngong, Nyeri and Narok. Cluster II consisted of Jirore and Baringo. These results were supported by the principal Coordinate Analysis. However, the clustering analysis did not correlate to the geographical areas of plant collection. The values for genetic diversity (H) and Shannon index (I) obtained from this study ranged from 0.0867-0.1483 and 0.1289 -0.2337, respectively, indicating that a low genetic diversity exists among the S. henningsii genotypes. It is recommended that all existing populations be conserved and further studied conducted using codominance markers to provide more insight into the genetic variation that exists within and among S. henningsii genotypes