| Tibet pig is plateau-breed, living in the Qinghai-Tibet plateau at an altitude of 2,500-3,000 meters. They are raised by grazing, mainly distributed in Tibet autonomous region of Sichuan, Yunnan, Tibet, Gansu. Because of geographic isolation and long-term inbreeding, Tibet pigs in different regions have some divergences. There is significant distinction between Tibetan pigs in Sichuan and Yunnan, for example size and the number of genes deviating from Hardy-Weinberg equilibration. It has the advantages of stronger resistance, better flavour, and the disadvantages of slow growth, poor reproductive performance. In order to improve the production of Tibet pig, many other native and foreign breeds are introduced to hybridize with them, which results in a sharp decline of the number of pure Tibet pigs. However, nowadays there are few studies about Tibet pig, and mainly focused on growth performance and special trait genes. The study of genetic diversity and phylogenetic of different groups of Tibet pig is almost blank.Based on different areas and production performance, Tibet pig was artificially divided into four groups:Tibetan pig, Sichuan Tibet pig, Gansu Hezuo pig and Yunnan Tibet pig, but this classification is lack of reliable genetic and evolutionary evidence. Based on the detail distribution analysis of the four areas, our study analyzed genetic diversity and phylogenetic position of four groups. We made a preliminary investigation on the classification, evolutionary relationship with other breeds in China and the world, and determine the taxonomic position. Our study will provide scientific basis for the conservation, utilization of Tibet pig genetic resources and producing new breed.In this study, we collected 183 ear tissue samples from Sichuan, Tibet, Yunnan and Gansu, and got the partial D-loop sequences of mtDNA. We analyzed the genetic diversity and phylogenetic relationship companied with the mtDNA D-loop sequences from other Chinese breeds using the software of BioEdit, MEGA, DnaSP, and Network.In the 183 Tibet pig mtDNA D-loop sequences (595bp/596bp/597bp),19 nucleotide polymorphism sites were detected, and they are all the transition sites. There are 29 haplotypes in the 183 sequences, the percentage of haplotype is 15.8%. Two clades were showed in the phylogenetic tree of the 29 haplotypes. The network relationship diagram devided 29 haplotypes into two regions. M district formed a complex network, while N district is a radiating shape. The phylogenetic tree and network relationship diagram constructed by comparing with five Chinese and five European pig sequences downloaded from GenBank showed that the Chinese and European pigs have different origin and domestication center, and the Tibet pig has a wild range of maternal lineages.Tibet Pig has less nucleotide diversity, while the haplotype diversity is more abundant. The pigs which are from Sichuan, Yunnan and Tibet all have closer relationship with the majority of Tibet pigs from Gansu Province. There is no obvious geographic differentiation. Although there are differences in size and Hardy-Weinberg equilibration deviations between Sichuan and Yunnan Tibet pig, the pigs from the two provinces belong to the same group and have a close relationship. Due to the insertion site, parts of Gansu’s Tibet pig got greater variation, and they formed a unique branch in the evolution tree. With geographical isolation and the persistence of inbreeding, Tibet pig will possess more differences and form unique local groups.In order to study the genetic diversity of Chinese pig breeds, this study collected 147 microsatellite markers from the literature and the database, at last selected 38 from them, two markers per autosome or sex chromosome. First, we detect the 147 microsatellite markers by agarose gel electrophoresis, then analysis by the polyacrylamide gel electrophoresis, finally we select 38 markers which can cover the whole genome with good polymorphic (?) characterization. The 38 microsatellite markers are as follows:SW780, S0008, SW1408, SW240, SW72, SW1315, SW2435, SW0107, S0005, SW1200, SW2415, SW2406, TNFB, S0101, S0225, SW268, SW539, SW174, SW1041, SW951, SW2008, SW486, S0143, SW957, SW1030, SW344, SW857, SW295, SW936, S0088, S0061, SW977, SW2427, SW1031, SW787, S0062, S0218, SW949. |
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