尼罗罗非鱼不同品系间mtDNA D-loop差异分析

Genetic Variation of Mitochondrial DNA D-loop Sequences from Different Strains of Nile tilapia,Oreochromis niloticus

通过PCR扩增获得尼罗罗非鱼＂88品系＂（XH）、＂99品系＂（AN）和吉富品系（GF）3个主要养殖品系共95尾鱼的mt DNA D-loop序列,并进行碱基测序及对比分析,探究3个品系在遗传结构信息、保种现状和选育潜力的差异。结果表明：13个品系个体序列片段长度为550-556 bp,包括111个变异位点,其中转换、颠换、插入/缺失数依次为65、34、12,多态位点比例为18.64%。23个品系共有27个单倍型,XH、AN、GF单倍型数依次为12、7、10,其中GF、AN共享1个单倍型,XH、GF共享1个单倍型,其他为各品系独有。3个品系的单倍型在NJ系统树上互相交叉,GF有2个单倍型在变异水平上形成独有的进化枝。33个品系间遗传分化指数均大于0.05,存在中等程度的遗传分化,其中XH与AN、XH与GF之间遗传漂变起主要作用,AN与GF之间基因流起主要作用。研究结果表明,目前选育的3个尼罗罗非鱼品系内遗传多样性水平较高;品系间存在中等程度的遗传分化,并具备高比例的独有单倍型,3个品系目前仍具备较高的选育潜力。

The mitoehondrial DNA D-loop sequences of ninety-five individuals from three dominated tilapia culture strains [ Nile tilapia ＇88 strain＇ （XH）, ＇99 strain＇ （AN） and GIFT strain （GF） ] were studied to understand the differences of the genetic strueture, breeding effect and genetic potential of the three strain populations. The results showed that ： （i） The length of their region sequences from three populations was 550-556 bp, including 111 variable sites, of which the transition, transversion and insert/deletion sites number were 65,34 and 12, re- spectively, polymorphie loci occupying 18.64 % in total sites. （ii）There were 27 haplotypes in three strain populations, which was 12 for XH strain, 7 for AN strain and 10 for GF strain, respectively, of which GF and AN shared a haplotype, XH and GF shared another haplotype, and others were exclusive to each strain. The haplotypes of three strains crossed each other in the NJ tree but two special haplotypes of GF formed a unique clade. （iii） The Fst values among three strain populations were all more than 0.05, which indicated that the genetic differentiation among them was moderate, of which the genetic drift played a major role between XH and AN, XH and GF, otherwise the gene flow played a main role between AN and GF. It was concluded that there was a high level of genetic diversity in three Nile tilapia strain populations, and there were moderate genetic differentiation and a high proportion of unique haplotypes among three strain populations, which indicated that the three tilapia strains still had a full potentiality in breeding selection.