Analysis of genetic diversity of tilapia during selection processing based on D-loop sequence

The mtDNA control region of GIFT strain Oreochromis niloticus in F0,F6-9 generation were amplified and sequenced.225 loci were polymorphic and accounted for 24.94% in 902 base pairs of 47 samples.The ratio of polymorphic loci was highest in F0,and decreased with selection proccessing.Nucleotide diversity index were 0.074 02,0.068 72,0.064 15,0.049 52,0.044 55 for F0,F6,F7,F8,F9,respectively.The ratio of polymorphic loci,nucleotide diversity index among these five generations showed that the selected populations were getting purer after selection procession.Genetic distances between F0 and these four selected populations were increased with selection procession,which suggested that selection could result in genetic differentiation just as caused by long-term geographical isolation.