Phylogenetic Analysis Based On MtDNA Cytb Gene In Nine Domestic Horses

All31mtDNA Cytb complete sequences of9Chinese domestic horse breeds (Yili, Jilin, Zhangbei, Yiwu, Bohai, Kazak, Yanqi, Baise and Keerkezi) were sequenced and the other243sequences were downloaded from GenBank, thus a total of274sequences were analyzed to reveal their genetic diversity and origin. PCR-RFLP was used to analyze the different genotypes of partial mtDNA Cytb. The results were showed as follows.(1) All31mtDNA Cytb complete sequences of9Chinese domestic horse breeds were1140bp by DNA sequencing. Among all31Cytb gene sequences, the average nucleotide content were:28.14%for A(26.3%-26.5%),26.44%for T (26.3%-26.5%),32.22%for C (32.1%-32.3%) and13.2%for G (13.1%-13.3%). Average (A+T) content was54.6%and45.4%for (G+C), it was apparent that the former was higher than the latter.(2) Polymorphic sites and haplotypes of mitochondrial DNA Cytb gene were analyzed from31horses of9breeds. In this study,33polymorphic sites were observed, including20parsimony informative polymorphic sites and13singleton sites, and21haplotypes were detected. All274Cytb gene sequences observed85haplotypes and84variable sites, which40of them were Parsimony informative polymorphic sites and44of variable sites were singleton sites.(3) The nucleotide diversity and haplotype diversity of four geographical areas were0.00322-0.00461and0.894-0.927respectively, among of which North American horses showed the lowest level, while Europen horses displayed the highest. A phylogenetic network of85haplotypes from274horses in four Geographical Areas was constructed by Network4.6software, which showed that most of the85haplotypes grouped into7distinct phylogenetic clusters. The Chinese horses were distributed to the7phylogenetic clusters, which suggested the multiple maternal origins of Chinese horses.(4) Genotypes data in A630G and C684T loci were obtained from369horses9breeds. Results indicated that A630G locus contained3genotypes AA, AG and GG by using BamH Ⅰ-RFLP, which haplotype frequencies of them were0.897,0.098and0.005respectively. The C684T locus contained3genotypes CC, CT and TT by using EcoRV-RFLP, which haplotype frequencies of them were0.986,0.011and0.003respectively. In all, there are six genotypes were defected and sorted into5haplotypes, of which haplotypes I was the basic haplotypes. Because of Yiwu horses detected4haplotypes, we inferred that many breeds horses involved in the breeding of the Yiwu horses.