阿坝藏族羌族自治州若尔盖地区藏猪mtDNA D-Loop的遗传多样性分析

旨在通过获得和对比若尔盖地区藏猪mtDNA D-Loop高变区的部分序列，为该地区藏猪遗传资源的保护与利用提供参考。本试验收集了若尔盖地区9个乡镇共80头藏猪耳组织，以甘南州藏猪mtDNA D-Loop基因序列为模板设计引物，采用PCR扩增测序技术获得了80条核苷酸序列，并采用生物信息学的数据处理方法进行分析。结果表明，若尔盖地区藏猪mtDNA D-Loop高变区（435 bp）的A+T含量（56.46%）明显高于G+C含量（43.54%），存在碱基偏倚性现象；在80条长度为435 bp的序列中，共检测到14个变异位点，鉴定了17个单倍型，单倍型多样度（Hd）、核苷酸多样度（Pi）和平均核苷酸差异数（k）分别为0.881、0.004 66和2.028，其中Hd、Pi和k在降扎乡藏猪群体中最高，Pi和k在占哇乡藏猪中最低；共享单倍型8个，特有单倍型9个，且若尔盖地区不同藏猪群体间特有单倍型数差异较大，其中，降扎乡藏猪的特有单倍型数量最多，占单倍型总数的17.65%（3/17）；Hap_1和Hap_15单倍型是4个乡镇（降扎乡、益哇乡、热尔乡和冻列乡）群体的共享单倍型，表明这4个乡镇藏猪群体存在两个共同的母系祖先单倍型。若尔盖地区藏猪的平均遗传距离为0.004 66，其中降扎乡和冻列乡藏猪间的遗传距离最大为0.006 90，包座乡和益哇乡藏猪间的遗传距离最小为0.002 16；构建的NJ分子系统进化树将若尔盖地区藏猪分为2支，而加入中国地方家猪、野猪和引种猪后，若尔盖地区藏猪在进化树中比较分散，说明该地区藏猪母源血统遗传复杂，彼此之间基因交流多。本研究进一步证实了若尔盖地区藏猪比西藏林芝、山南、日喀则、甘孜州、阿坝州藏猪的遗传多样性程度高，受到人工选择强度低，应强化对若尔盖地区藏猪遗传资源的保护与利用。

Genetic Diversity of Tibetan Pig Mitochondrial DNA D-Loop in Ruoergai Area of A'ba Tibetan and Qiang Autonomous Prefecture

The purpose of this study was to obtain and compare partial sequences of mtDNA D-Loop high variable region of Tibetan pig in Ruoergai area,so as to provide reference for the protection and utilization of Tibetan pig genetic resources. In this experiment,the ear samples of 80 Tibetan pig from 9 towns in Ruoergai area were collected. The primers were designed based on the sequence of mtDNA D-Loop region of Tibetan pig in Gannan. Eighty nucleotide sequences were obtained by PCR amplification and sequencing technology,and the data processing method of bioinformatics were used to analyze the sequences. The results showed that the A+T content (56.46%) of mtDNA D-Loop high variable region (435 bp) was obviously higher than G+C content (43.54%) of Tibetan pig in Ruoergai area,and representing base bias. Among the 80 sequences of 435 bp length,14 mutation sites and 17 haplotypes were identified. Haplotype diversity (Hd),nucleotide diversity (Pi) and average number of nucleotide difference (k) were 0.881,0.004 66 and 2.028,respectively. Hd,Pi and k were the highest in Tibetan pig populations from Jiangzha, and Pi and k were the lowest in Tibetan pig population from Zhanwa. There were 8 shared haplotypes and 9 specific haplotypes,and there was big difference in specific haplotype number among different Tibetan pig populations in Ruoergai area. The highest number of specific haplotypes were found in Tibetan pig population from Jiangzha,accounting for 17.65% (3/17) of the total haplotype number. The haplotypes of Hap_1 and Hap_15 were shared haplotypes by Tibetan pig populations from 4 townships (Jiangzha,Yiwa,Re'er and Donglie),indicating that there were two common maternal ancestry haplotypes in Tibetan pig populations from the 4 towns. The average genetic distance of Tibetan pigs in Ruoergai area was 0.004 66. The genetic distance between Tibetan pig populations from Jiangzha and Donglie was the highest of 0.006 90,and the genetic distance between Tibetan pig populations from Baozuo and Yiwa was the lowest of 0.002 16. The NJ molecular phylogenetic tree was constructed to divide the Tibetan pigs into two branches. After Chinese domestic pigs, wild boars and introduced pig breeds were introduced,the Tibetan pigs in Ruoergai area were more dispersed in the evolutionary tree,indicating that the maternal lineage of Tibetan pigs in this area was genetically complex and had many genetic exchanges. This study further confirmed that the Tibetan pigs in Ruoergai area had higher genetic diversity than that in Tibet Nyingchi,Shannan,Shigatse,Ganzi and A'ba Prefecture,and the intensity of artificial selection was lower, and the protection and utilization of Tibetan pig genetic resources should be strengthened in Ruoergai area.