Genetic Diversity And Origin Of Mitochondrial DNA D-Loop Regionfor Domestic Goat Breeds In China

Breed resource is the basis of sustainable development for animal production industry. Presently,the status of herbivorous animal is becoming more important than before.China is the country,which has the most goats and the most goat breeds.But we have little knowledge of the origin, migration,evolution and breeds genetic status of Chinese indigenous goat breeds.On the other hand,the goat breeds are endangered because of the introduction of exotic commercial goat breeds and the influence of economies interests. The research of livestock genetic diversity helps to the conservation and utilization of breeds resource.The sequence of mtDNA is one of the most common and trust worth molecular markers in the study on animal molecular evolution and genetic diversity.In this study, 140 mtDNA D-loop sequences in 10 Chinese domestic goat breeds were analized, and two sequences(Capra falconeri and Capra aegagrus) of wild goat were downloaded from NCBI, we get the results as follows:1. There were 84 different haplotypes and 171 polymorphic sites. The mean nucleotide diversity(π) was 0.02063±0.00225, the haplotype diversity(Hd) was 0.988±0.003, and the average number of nucleotide differences was 24.896. These results showed an abundant genetic diversity in domestic goat breeds of China.2. 77 kinds various varieties unique single time and 7 kinds single time which share for the variety in the 84 kinds of haplotypes.There were two clades of 84 haplotypes: clade A and B. A clade included 62 haplotypes,which existed in all goat breeds, and clade B,which included 22 haplotype, existed in all varieties except Daiyun goat, though frequency was low.3. Tajima′s D test of selective neutrality in all sequences was not significant(p>0.01), ranged from -1.31219 to 1.71696 . It revealed that all sequences of domestic goat were selective neutrality and the goat population did not undergo expansion.4. Genetic distance among 10 domestic goat breeds was from 0.010 to 0.026, of which, it was smallest between Chuandong white and Daiyun goat,which was 0.010.And it was biggest between Gulin and Longlin gaot,which was 0.026. Of 10 breeds, genetic distance within each breed was from 0.002 to 0.025.And it was smallest within Daiyun , 0.002, on the other hand, it was biggest within Longlin ,0.025. All above revealed that variance of genetic diatance among domestic goat breeds of China was small, and gene exchange was frequent. 5. The NJ tree indicated that there were two main branches in those 10 domestic goat breeds, thereinto,one was clustered with Capra aegagrus,and Capra falconeri was clustered alone, which indicated that Capra aegagrus had more contribution to Chinese domestic goat breeds.