220 Mitochondrial DNA polymorphism as a measure of genetic diversity in African tilapia fish

Abstract This study focused on the assessment of genetic diversity in African tilapia fish (Oreochromis niloticus) obtained from two populations (Domita in South-South and Odeda in South-West, Nigeria) using the displacement loop (D-loop) and cytochrome B region of the mitochondrial deoxyribonucleic acid (mtDNA). A total of 28 samples (15 from South-South and 13 from South-West) were used for the genetic analysis. DNA was extracted from the tissue of all the samples using Quik-gDNATM miniPrep kit. The D-loop region was sequenced for all samples from the two populations, while cytochrome b (cyt b) region of mtDNA was only sequenced for samples from South-South population Multiple sequence alignment was carried out using molecular evolutionary genetic analysis (MEGA) software before subsequent genetic analyses. There were 176, 162 and 144 polymorphic sites for D-loop of South-South, South-West and cyt b of South-South populations, respectively. Haplotype diversities (Hd) were 1.00 ± 0.024 and 1.00 ± 0.030 while nucleotide diversities were 0.168 ± 0.086 and 0.161 ± 0.084 for D-loop of South-South and South-West populations, respectively. For the cyt b, haplotype and nucleotide diversities were 0.91 ± 0.003 and 0.051 ± 0.016. The genetic distance inferred between D-loop regions of South-South and South-West populations was 0.243. Phylogenetic analysis grouped the samples into two clusters based on population. Analysis of molecular variance (AMOVA) revealed 37.32% variation within population and 62.68% variation among population with a significant fixation index of 0.627 (P < 0.05). The findings of this study revealed high level of genetic diversity among the tilapia populations and may serve as pivot information for the genetic improvement of this important species.