Abstract:

The aim of this study was to analyze the genetically structural differences of different geographical domestic horses and provide some molecular biology evidences for the maternal origins and domestication of the horses. The better knowledge about it was helpful for the evaluation of the genetic resources of the horses. We investigated the complete mitochondrial Cytb sequence of 36 samples from four horse breeds, Mongolian horse, Xinihe horse, Sanhe horse and Thoroughbred by amplification and direct sequencing. Combining with all the horse Cytb sequences deposited in GenBank, a total of 219 horse Cytb sequences were collected. 86 different haplotypes with 80 polymorphic sites were revealed with the analysis of the total Cytb sequences, and the haplotype diversity and the nucleotide diversity were 0.946 and 0.00454, respectively, indicating abundant genetic diversity in domestic horses. For the first time, we analyzed the differences of horse maternal structure in different geographic areas based on Cytb sequences, by dividing the total samples into North American, West European, East European, Middle East, Central Asian and East Asian groups. It was shown that the significant differences were only observed between North American group and three Asian groups. On the one hand, it indicated that the ingression within the horses in the Eurasian continent was great; on the other hand, it supported the assertion that the domesticated horses of North America originated from Europe to some extent. Seven distinct haplogroups (A-G) were revealed in the founded Median Joining network, supporting the multiple maternal origins of the horses. Moreover, all the seven horse haplogroups were composed of horses from several different geographic regions. Besides, there was no obvious correspondence between the geographic regions, maternal structure, and maternal origins among all the domesticated horses around the world.