Abstract:

The aims of this study were to explore the genetic diversity,phylogenetic evolution and genetic relationship from six yak groups of Tibetan yaks by mtDNA ND1.To provide a theoretical basis for the genetic diversity,historical evolution,the protection and utilization of genetic resources of Tibetan yaks.The sequences of ND1 gene protein coding region(CDS)in 95 individuals of Pali yak,Jiali yak,Gongbujiangda yak,Sibu yak,Jiangda yak and Leiwuqi yak were analyzed by PCR and direct sequencing.DNAMAN,DNASP 5.1,Mega 7.0,Arlequin 3.5.2 and other software were used to analyze the sequence polymorphism,haplotype diversity,genetic distance and constructed the haplotype network map and phylogenetic tree.The result showed that the sequence length of CDS region of ND1 gene of Tibetan yaks population were 956 bp,and a total of 78 mutation loci and 16 haplotypes were detected and the average haplotype diversity(Hd)and nucleotide diversity(Pi)were 0.670 and 0.004 21,Tajima's D was all negative.According to the molecular variance analysis of population genetic differences,the degree of variation within Tibetan yaks was greater than among populations;the degree of differentiation between Sibu yak and Jiali yak was large,and the degree of differentiation among most other groups was medium or weak.In addition,cluster analysis found that Leiwuqi yak was grouped into a single group,Jiali yak,Gongbujiangda yak,Sibu yak and Jiangda yak were first grouped into one group,and then grouped with Pali yak;the 16 haplotypes were divided into two clusters,suggesting that there may be two maternal origins in Tibetan yaks.The cluster analysis with other cattle breeds showed that Bos grunniens,Bos taurus and Bos javanicus may be the mixed maternal origin of Tibetan yaks.The genetic diversity of Tibetan yaks was very rich,among which the genetic diversity of Leiwuqi yaks was the most abundant,six yak populations had two maternal origins.

Key words: Tibetan yak, ND1 gene, Genetic diversity, System evolution, Genetic differentiation