Genetic Diversity And Origin Of Tibet Pig In Gannan

Genetic diversity is an important element of biodiversity, it’s also the basis ofenvironment adaptation and the premise of evolution. Livestock genetic diversity is thelong-term stanchion for improving animal production efficiency. The knowledge ofgenetic diversity and genetic character of local pig breeds is not comprehensive andsystematic, so normally we use the local breeds as the maternal and the other breeds as thefathers to mate. This leads to inadequate use of the good characteristics of many pigbreeds and the decline of the genetic diversity of pig gradually in China and even somegenetic resource of pig on the edge of dying out. Tibet pig is an unique breed locate in theeast of Tibetan Plateau and southwest of Gansu province. At the moment, the geneticstatus of Tibet pig remains unclear, the files about cladistics and origin of Tibet pig remaingot from the geographical distribution and the phenotype. In order to clarify the geneticdiversity and origins of Tibet pig, to provide the genetic diversity and origin of Tibet pig ingannan, the characterization of microsatellite DNA markers and mtDNA D-loop sequencesof7Tibet pig populations were carried out. The7populations with281Tibet pigs weregot from Kajiadao, Kajiaman, Xiahe, Zhuoni, Ruoergai, Dala, Minxian of Gannan. All the7populations were assessed for genetic diversity and origins using12microsatellite lociand mtDNA D-loop sequences. A wide range of statistical analyses were performed on thedata to answer the questions on populations’ genetic diversity, origin, relationship anddifferentiation. The results are as follows:1. A total of180alleles were detected at12microsatellite locus in281pigs individualsof7populations. The mobility scale of alleles is between141~180. The average of allelesat12microsatellite locus of7populations is13.80.2. The expected heterozygote (HE) values for the7populations are0.9056±0.0117～0.9176±0.0061, the highest value is0.9176in Xiahe Tibet pig, and the lowest value is0.9056in Kajiaman Tibet pig. The observed heterozygote (HO) values for the7populations are0.7628±0.0245～0.8399±0.0229, and the highest value is0.8399in XiaheTibet pig, the lowest value is0.7628in Zhuoni Tibet pig. 3. The PIC of7Tibet pig populations in12microsatellite DNA locus is abundant. Thehighest PIC is0.9178in loci S0227and the lowest PIC is0.8552in loci CGA. In the7populations, the highest PIC is0.9014in Ruoergai Tibet pig and the lowest is0.867inKajiadao Tibet pig.4. The result of single locus exact test indicated a total number of86locus-populationcombinations deviated significantly from Hardy-Weinberg equilibrium (HWE) proportions.Zhuoni Tibet pig and Minxian Tibet pig respectively have12locus-populationcombinations deviated significantly from Hardy-Weinberg equilibrium proportions, andKajiaman Tibet pig has the lowest of6locus-populations combinations deviatedsignificantly from Hardy-Weinberg equilibrium proportions.5. Phylogenetic analysis showed that Nei’s genetic distance (D_A) value is short betweenRuoergai Tibet pig and Dala Tibet pig (0.0659), and it’s large between Kajiadao Tibet pigand Xiahe Tibet pig (0.2426). Nei’s standard genetic distance (D_S) value is short betweenDala Tibet pig and Minxian Tibet pig (0.0771). It indicated that Ruoergai Tibet pig, DalaTibet pig and Minxian Tibet pig are very closely related to each other. Their parents haverather close genetic background indeed.Phylogenetic tree illustrated the same conclusion.6. Principal component analyses (PCA) indicated that7populations have no clearlydifference in comparison of PC1-PC2, PC1-PC3and PC2-PC3. The inference ofpopulation structure showed7populations have a similar genetic structure.7. By sequencing the mitochondrial DNA D-Loop of134Tibet pigs to study the originand genetic diversity, it found that there are4sequences with1199bp long,127sequenceswith1219bp long and3sequences with1319bp long.127sequences were studied and75polymorphic sates of83haplotypes were found. The analysis of the phylogenesis showsthat it takes on2obvious branches, therefore, the7populations of Tibet pigs might have2maternal origins.8. The phylogenesis tree with Tibet pigs’ sequences and13other pig breeds’ sequencesand15wild pigs’ sequences showed that Tibet pigs had the same origin with wild pigs ofsoutheastern coast and no connection with wild pigs of East and Southeast Asia.