Genetic diversity of mtDNA D-loop and origin of the Chinese cattle

Complete mitochondrial D-loop sequences of 140 samples obtained from 15 Chinese local cattle breeds were analyzed.The result showed 67 different haplotypes with 113 polymorphic sites.The haplotype diversity and nucleotide diversity were 0.608-1.000 and 0.002-0.028,respectively,indicating abundant genetic diversity in Chinese cattle.The constructed Neighbor-Joining(NJ) tree revealed that there were two maternal origins of Bos taurus and Bos indicus in Chinese cattle.Among them,the Bos taurus lineage had rich mtDNA genetic diversity,while Bos indicus lineage had poor mtDNA genetic diversity,respectively.It can be concluded that the cattle in Northern China originated from the Bos taurus lineage,while the cattle in Central China and Southern China originated from Bos taurus and Bos indicus lineages.In our study,two mtDNA haplotypes belonging to African cattle were detected,thus providing molecular evidence for an African lineage in Chinese cattle.