广东养殖尼罗罗非鱼3个不同群体MHC ⅡB基因序列多态性和遗传分化

利用一对特异性引物MHC 2b-snp-sf和MHC 2b-snp-sr,从广东省3个不同罗非鱼养殖地区（以下分别称高要群体,茂名群体,惠州群体）采集的137尾尼罗罗非鱼（Oreochromis niloticus,GIFT strain）的个体基因组中扩增出长度为775-796 bp的片段。克隆后测序,序列分析结果显示：775-796 bp的核苷酸序列中共检测出62个简约信息位点,49个单碱基突变位点。112个多态位点中,增添/缺失位点34个,转换位点44个,颠换位点33个,另外一个位点既出现转换（C/T）又出现颠换（A/T）。137尾个体的751个阳性克隆的测序结果分析表明,751条序列分属于4个等位基因。其中,等位基因Orni-DAB＊0101在3个群体中所占比例最高（85.2%）。等位基因的分布及群体内遗传多样性参数分析表明：高要、茂名群体遗传多样性较丰富,惠州群体遗传多样性较低。群体间的分化指数（FST值）、平均基因流（Nm）、分子方差分析（AMOVA）和平均K2-P遗传距离均表明3个养殖群体间存在广泛的基因交流,未发生群体间的遗传分化。该研究结果提供了广东地区养殖尼罗罗非鱼MHCⅡB基因的部分遗传信息,为尼罗罗非鱼抗病品系的选育提供理论依据。

MHC ⅡB Gene Polymorphism and Genetic Diversity of Nile Tilapia（Oreochromis niloticus） Farmed in Guangdong Province

The MHC class Ⅱ B gene fragment was amplified from 137 individuals which were sampled from three different cultured nile tilapia stocks（namely Gaoyao, Maoming and Huizhou stocks） farmed in Guangdong province, using primer pairs of 2b-snp-sf and 2b-snp-sr. Sequence analysis showed that the fragments were 775-796 bp in length. And there were 62 parsim-info sites, 49 singleton sites in all 112 mutations sites, which was including 34 insert/lacuna sites, 44 transition sites and 33 transversion,and one transition（C/T） and transversion（A/T） site. Four different MHC class ⅡB alleles which encoded 4 different amino acid sequences were identified among 751 clones from 137 individuals. The percentage of allele Orni-DAB＊0101 was 85.2%, higher than that of other alleles. The FSTvalue, Nmvalue, AMOVA analysis and average Kimura 2-parameter distances revealed there existed broad gene exchange among the 3 cultured stocks, but there was no genetic differentiation among the 3 cultured stocks. This study has provided the genetic information for MHC class Ⅱ B gene of nile tilapia farmed in Guangdong province and identified potential candidates for further investigation into the breeding of disease-resistant strain of nile tilapia.