Analysis of genetic diversity of GIFT strain Nile tilapia (Oreochromis niloticus) during selection processing by microsatellites

19 microsatellites were used to observe and analyse the genetic variation of selected generations of GIFT tilapia(Oreochromis niloticus).During selection processing,19 polymorphic microsatellite loci were used.Total of 115 alleles were found among the five generations of 100 individuals.The number of alleles per locus ranged from 3 to 11,with allele size ranging from 70 to 270 bp.The average gene diversity indices of the base population F0,and selected generations,F6,F7,F8,F9 were(0.3083±0.1834),(0.2982±0.1889),(0.2923±0.1898),(0.2572±0.1923),(0.2743±0.1597),respectively,which suggested that the selected populations were getting pure generation by generation.AMOVA analysis showed that there were 93.24% of total genetic variation derived from genetic diversities within population,6.67% from among populations.Nei's(1978)genetic identity between F0 and F6,F7 was 0.943 5 and 0.942 2,between F0 and F8,F9 was 0.933 2 and 0.930 3,respectively,which was relatively lower.Nei's(1978)genetic distance between F0 and F6,F7 was 0.058 1 and 0.059 5,between F0 and F8,F9 was 0.069 1 and 0.072 2,which was relatively larger.Pairwise Fst values were 0.037 68,0.064 370 between F0 and F6,F7,respectively,averaged 0.051 03;and 0.060 93,0.075 87 between F0 and F8,F9,respectively,averaged 0.068 40.These results showed that there were a minimal,but could be monitored genetic differentiation caused by nine generation of selection in Nile tilapia,the genetic structure of the “New GIFT tilapia” F8-9 was more stabler than F6-7.