Application Of Mitochondrial DNA Marker On Phylogeny Among Some Native Populations Of Chinese Yellow Cattle

Maternally inherited mitochondrial DNA(mt DNA) has been used extensively to determine origin and evolution, genetic structure among populations, genetic diversity and phylogeny, all of which can guide genetic resource conservationin both domesticated animals and wildlife. Samples from a Qinchuan cattle population in Baoji(SQB, n=158), a Zaosheng cattle population in Zaosheng(GZZ, n=148), a Zaosheng cattle population in Hesheng(GZH, n=36), a Pingliang native cattle population in Pingliang(GPL, n=112), a Guyuan native cattle population in Guyuan(NGY, n=75), and a Linxia yellow cattle population in Linxia(GLX, n=24) were used in this study. Additionally, mt DNA D-loop sequences from 49 native populations(611 individuals) of Chinese Yellow Cattle from Gen Bank were included in this study. The PCR products from the six cattle populations were sequenced and 417 bp nucleotide sequences containing the hypervariable region were analyzed for the 55 native populations of Chinese Yellow Cattle by using mt DNA D-loop analytical techniques. The objective of this study was to systematically evaluate genetic diversity and phylogeny among 55 native populations of Chinese Yellow Cattle. The resultant information will contribute to the genetic characterization and provide a scientific basis for future genetic resource evaluation, conservation and sustainable utilization of native Chinese Yellow Cattle. The results and conclusions which obtained in this study were as follows:1. A total of 316 variable sites in the 417 bp length of the mt DNA D-loop region were detected among the 55 native populations(1164 individuals) of Chinese Yellow Cattle. The percentage of nucleotide variation in this study was 75.78%, which contained 199 singleton variable sites and 117 parsimony informative sites. There were three types of mutations that transition, transversion, transition and transversion coexist were identified without considering insertion and deletion in this study, and the main type of mutations was transition. The results indicated that there was a significant genetic variation among the 55 native populations of Chinese Yellow Cattle;2. The analysis of base composition showed that the average percentage of A+T was 61.3%, which was much greater than G+C(38.7%), which inferred that mt DNA D-loop region among the 55 native populations of Chinese Yellow Cattle was rich in A and T;3. A total of 356 haplotypes(H1~H356) were identified at the 316 variable sites identified in the 55 native populations of Chinese Yellow Cattle. There were 236 unique haplotypes and 120 shared haplotypes identified in this study, which indicated both genetic uniqueness among the populations as well as some genetic commonality among the 55 native populations of Chinese Yellow Cattle, or there was a wide range of haplotypes sharing among the populations and a widespread gene flow among 55 native populations of Chinese Yellow Cattle;4. The diversity of haplotypes(Hd±SD), the average number of nucleotide differences(k), and nucleotide diversity(Pi) among the 55 native populations of Chinese Yellow Cattle were estimated. Pairwise comparisons for diversity of haplotypes(Hd±SD), average number of nucleotide differences(k) and nucleotide diversity(Pi) were made between populations and between populations and the average of all populations. Results showed that genetic diversity among native populations of Chinese Yellow Cattle was very rich;5. Phylogenetic and intermediary network relationship analysis of the 55 native populations of Chinese Yellow Cattle indicated that they were clearly divided into two branches in the Neighbor-Joining tree and intermediary network relationship. Results suggested that there were two major types of maternal origins among native populations of Chinese Yellow Cattle, namely Bos taurus and Bos indicus maternal lines.