Genetic Characterization of Four Strains of Oreochromis Niloticus Using the Rapidly Amplified Polymorphic DNA (Rapd).

Abstract

The genetic characterization of four strains of Oreochromis niloticus was carried out using Randomly Amplified Polymorphic DNA (RAPD). Three samples each of four strains of grown O. niloticus in Nigeria, viz; local mixed sex strain, commercially available mixed sex strains from China and a farm in Ibadan, and hormonal sex reversed all male population were used. Genomic DNA was isolated from the flesh tissues of the strains of O. niloticus using the Cetyl Trimethyl Ammonium Bromide (CTAB) method. The banding pattern was transformed into numerical values and statistical analysis was done using Unweighted Pair-Group Method Using Arithmetic Averages (UPGMA) to calculate the Nei’s similarity coefficients. Canonical classification was also carried out.Out of the twenty five RAPD
markers used, 10 were informative on agarose gel, of with 58% polymorphisms. A total of seventy seven
bands were amplified. From the cluster analyses, the local strains were shown to be genetically distinct
but the other 3 showed various levels of similarities. The Nei’s genetic distance among the populations
was 47%. Apart from the local strain, others showed greater similarities with variability of 37% among
themselves. Within strain diversity were 15%, 32%, 25% and 33% for the local strain, tilapia from
commercial farm, China strain and the hormonal sex reversed respectively. The distinctness of the local
strain and the narrow variability within its membership showed that the population is not as genetically
divers as the other three strains. The future of tilapia stock improvement will rely on appropriate stock
choice, development of sound management techniques and selective breeding.