Genetic variations among different generations and cultured populations of Nile Tilapia (Oreochromis niloticus) in Ghana: Application of microsatellite markers

Genetic diversity between and within breeds and populations of fish provides valuable information on the probable response to selection, and towards sustainable aquaculture production. However, due to the widespread introductions of O. niloticus to many regions in Africa, the genetic diversity of wild and cultured populations is now threatened. In the present study, microsatellite (SSRs) markers were used to assess genetic diversity among different Generations and cultured populations of O. niloticus in Ghana. Five Generations of a particular improved strain of O. niloticus, together with three different aquaculture populations were screened with 5sets of microsatellite primers, which produced stable and reproducible amplification and polymorphic patterns. Shannon's information index (I) values provided evidence of high genetic diversity among the Generations and the 3 cultured populations. Whereas no significant genetic differentiation (FST = 0.005), thus, structuring existed among the different Generations of the Akosombo strain, moderate genetic structuring (FST = 0.082) was found among the three different cultured population. Nei's D, phylogenetic tree analysis, also placed the AK and the two other cultured populations of O. niloticus into two different clusters, suggestive of high mixing of stocks and sharing of different genetic backgrounds. Analysis of Molecular variance (AMOVA), showed more genetic divergence existing within populations (95%), than among populations (5%). The microsatellite marker technique employed in this study was found to be a simple and efficient method for genetic diversity studies. The present study thus provides valuable base information regarding the population structure of cultured populations of O. niloticus in Ghana, which would enhance further fish population genetic studies.