Genetic variations among the recent selected generations F_(10)-F_(13) of NEW GIFT strain Nile tilapia (Oreochromis niloticus) by SSR analysis

Simple Sequence Repeats(SSR)marker analysis was used to measure the genetic structure and genetic differentiation of four successively selected generations(F10,F11,F12,F13)of NEW GIFT strain Nile tilapia(Oreochromis niloticus).The results showed that: total of 78 alleles(100-295 bp)were found among the four populations of 120 individuals with 13 polymorphic microsatellite loci.The mean number of effective alleles of four generations ranged from 2.84 to 3.27,the average polymorphism information content and the expected value of mean heterozygosity varied from 0.567 6 to 0.622 9 and from 0.627 1 to 0.676 2 in four selected generations,respectively.Three genetic parameters all indicated the same tendency that they have been steadily decreasing with the increasing of selected generations,which proved that the purifying experience of NEW GIFT strain Nile tilapia(Oreochromis niloticus)was still continuing in the course of long-term selective breeding.On the other hand,pair-wise FST values between the two arbitrary generations ranged from 0.019 07 to 0.133 54,which indicated that the selective breeding generations also generated moderate genetic differentiation.The above results showed that our applied breeding technique strategy(synchronized selection at Yellow River,Yangtze River and Pearl River ecosystems,exchange periodically,keep effective breeding number,as well as strict super-fish four-steps selection proceeding)for the NEW GIFT strain Nile tilapia(Oreochromis niloticus)could enable the selective breeding populations to maintain abundant genetic variation,which would be beneficial to the sustainable development of long-term selective breeding.