The Origin And Evolution Of Chinese Goat And Cattle Based On MtDNA Genetic Diversity

Breed resource is the basis of sustaining development of animal production industry. Presently, the status of herbivorous animals is becoming more and more important than before. China is one of the countries in the world which has the richest goat and cattle breed resources. But we have little knowledge on the origin, migration, evolution and breeds genetic status of Chinese indigenous goat and cattle breeds. On the other hand, the goat and cattle breeds are endangered because of the introduction of exotic commercial goat and cattle breeds and the influence of economies interests. The research of livestock genetic diversity helps the conservation and utilization of animal breed resources .The sequencing of mtDNA is one of the most common and reliable molecular markers in detecting animal molecular evolution and genetic diversity. In order to understand the phylogenetic relationship of goat and cattle in China, the mtDNA D-loop complete sequences of 183 individuals from 13 Chinese indigenous goat breeds and 82 individuals from 4 Guizhou indigenous cattle breeds, collecting 242 D-loop sequences from 29 Chinese cattle breeds from GenBank were carried out. The results will provid scientific basis for resource protection and utilization. The conclusions are as follows in this study.1. The complete mtDNA D-loop sequences, 1212-1213 bp in length were determined for 183 animals in 13 Chinese goat breeds. 135 D-loop haplotypes with 144 polymorphism loci from 183 samples of 13 Chinese goat breeds were determined. The haplotype diversity and nucleotide diversity in 13 Chinese goat breeds were 0.9333-1.0000 and 0.6337%-2.5194%, respectively. The results indicate that the genetic diversity of Chinese goats is very abundant.2. Phylogenetic analysis and a reduced median network analysis revealed two highly divergent goat mtDNA lineages A and B mainly. The frequency of the lineage A and B was 76.50% and 20.77%, respectively. Two additional lineages C and D were observed only in Tiban goat breed. These two lineages are present in China at low frequency (1.64% and1.09%) respectively.3. Many haplotypes were shared by individuals of 13 different breeds from different geographical regions of China. AMOVA analyses indicated that the variation within breeds and the variation among breeds were 92.13% and 7.87% respectively. There was no significant geographical structure in Chinese goat populations.4. The mean pairwise difference observed and nucleotide diversity between haplotypes from the Chinese goats are 6.22 + 3.20, and 0.0111 ±0.0064, respectively;while those from the five Asian countries (i.e. India, Pakistan, Mongolia, Malaysia and Laos) are 4.11 ±2.20 and 0.0082 ±0.0049, respectively. All above evidence first indicated that mtDNA lineage B of goats probably originated from China.5. The complete mitochondrial D-loop sequences, 910 bp in length, in 82 individuals from 4 cattle breeds in Guizhou province were first analyzed. The nucleotide diversity (71 value) and haplotype diversity (H) estimated from mtDNA D-loop region in 4 cattle breeds in Guizhou varied from 2.16% ~ 2.61% and 0.695 ~ 0.909, respectively, showing that abundant mitochondrial genetic diversity exists in Guizhou cattle breeds. The NJ tree indicated that the origin of cattle breeds were from Bos taurus and Bos indicus which had the nearly same influence on cattle breeds in Guizhou.6. The complete mtDNA D-loop sequences of 324 individuals including 82 cattle from 4 breeds in Guizhou province and 242 cattle sequences available in GenBank database were analyzed in the paper. The results showed that the Chinese cattle were converged into two maternal origins of Bos taurus and Bos indicus. The ratio was 59.3% and 40.7%, respectively.7. Among the 324 animals from 33 cattle breeds, 132 individuals came from B. indicus type. Only 27 haplotypes were clustered into two lineages (IA and IB). Lineage IA existed in all B. indicus groups of Chinese cattle, and lineage IB only existed in B. indicus groups of cattle in Yunnan-Guizhou plateau.8. Lineage T2, T3, T4 and absent African cattle specific lineage Tl of the B. taurus haplotypes in Chinese cattle were found firstly. Among the lineages, the ratio of T3 from European cattle, T2 from Near-Eastern cattle and Northeastern Asia cattle was 66.7%, 18.2% and 15.1%, respectively.9. The abundant genetic diversity and complicated population genetic structure of Chinese cattle originated from B. taurus were detected firstly;the poor genetic diversity of Chinese cattle originated from B. indicus was detected.10. The results further proved that the Chinese cattle originated from Bos taurus (including taurine and Mongolian cattle) and Bos indicus. No evidence of Chinese cattle originating from yak, Banteng and African cattle was found. The point of Chinese zebu probably domesticated in Yunnan-Guizhou plateau was supported. The point of Chinese zebu probably domesticated in Hainan island was not supported in this paper.