为研究广西主养区域逃逸罗非鱼的遗传多样性, 本研究对广西玉林、南宁、钦州、贵港、防城港、北海的六个地理群体的尼罗罗非鱼线粒体D-loop序列进行了分析比较。通过聚合酶链式反应(PCR)和测序, 获得了广西玉林、南宁、钦州、贵港、防城港、北海等六个地理群体的尼罗罗非鱼线粒体D-loop序列, 采用序列比对和构建系统进化树等生物信息学分析方法探讨了不同地区尼罗罗非鱼线粒体D-loop的多样性。测序结果表明, 在得到的线粒体D-loop区序列中, 四种碱基A、G、T、C的平均比例分别为32.05%、20.79%、33.19%和13.97%, 其中碱基C含量最低, 碱基T含量最高。C+G(34.75%)的含量明显低于A+T(65.25%)的含量。共检测到140个变异位点, 其中转换为79个, 颠换为42个, 19个插入(缺失)位点。碱基替换与插入(缺失)的比为6.39。在所测得的罗非鱼D-loop序列中成功识别保守序列CSB-2, CSB-3和相似序列CSB-1。系统进化分析表明, 南宁地区罗非鱼的遗传距离值相对其它地区的遗传距离值较小, 序列与参考序列最为接近, 说明该区域罗非鱼的遗传分化程度最低; 钦州地区逃逸尼罗罗非鱼的遗传距离相对其它地区间遗传距离值较远, 在系统发育树中钦州地区罗非鱼也聚为整一小枝, 说明钦州地区罗非鱼较其它区域有明显的遗传分化。

To investigate the genetic diversity of escaped tilapia in main aquaculture area of Guangxi, the present study compared and analyzed mitochondrial D-loop control region sequences from Yulin, Nanning, Qinzhou, Guigang, Fangchengang, and Beihai. Using polymerase chain reaction(PCR)and sequencing, the D-loop sequences of tilapia from Yulin, Nanning, Qinzhou, Guigang, Fangchengang and Beihai were obtained. By sequence comparison, construction of phylogenetic tree and other bioinformatics analysis, the genetic diversity of D-loop was discussed in different area of tilapia. The sequence results showed that the A, G, T, C ratios were 32.05%, 20.79%, 33.19%, and 13.97% respectively in D-loop from tilapia. Among them, the C ratio was the lowest and T ratio was the highest. The C+G ratio of 34.75% was lower than the A+T ratio of 65.25%. In total, 140 mutation sites were found including 79 transitions, 42 transversions and 19 inserts(deletions). The ratio of substitution and inserts(deletions)were 6.39. The conserved sequences of CSB-2, CSB-3 and CSB-1 were identified from the D-loop sequences from tilapia. Phylogenetic analysis shows that the value of genetic distance were smaller than other comparisons in Nanning and the distance between Nanning and reference sequences was the smallest indicating the low degree of differentiation in this area. High genetic distance was found in escaped tilapia in Qinzhou and the fish in Qinzhou were clustered in one twig indicating the tilapia in Qinzhou had significant genetic differentiation compared with the tilapia in other areas