Study On MtDNA Genetic Diversity Of Xinjiang Native Horse Breeds And Przewalski's Horse And Their Genetic Relationship

Xinjiang is one of the regions with rich domestic horse resource in China. Domestic horses in Xinjiang experienced long evolutionary process of genetic variation and natural selection, and gradually differentiated into select horse breeds such as Kazakh horse, Balikun horse, Yanqi horse. The native horse breeds in Xinjiang pocess excellent qualities as anti-cold, rough feeding tolerance, strong disease resistance, high endurance and adaptability. In the mean time Xinjinag is also one of the regions with Przewalski's horse origin.The Przewalski's horse became extinct in wild by the middle of last century. Currently, there are approximatety1300 Przewalski's horses in 112 wild animal breeding centers and zoos which are distributed in 5 continents in the world, and Xinjiang wild horse breeding center has 278 such horses. In this study, mt DNA D-loop region sequence polymorphisms of Przewalski's horses from Jimusaer Wild Horse Breeding Center in and three other domestic horse breeds in Xinjiang were measured and analyzed comparatively. Scientific evidence was provided for identifying genetic diversity of Przewalski's horses and native horse breeds of Xinjiang and phylogenetic relationships between them.The result showes that:(1)The mt DNA D-loop region 402bp sequence(15464～15866) of 25 individuals in three native horse breeds in Xinjiang province, China was sequenced; 22 haplotypes were investigated. The average haplotype diversity(h) was 0.969; the average nucleotide diversity was 2.53%. The results indicate that the mt DNA D-loop partial sequence of native horse breeds in Xinjiang.have high genetic diversity.(2)The Kimura 2-parameter genetic distance of partial sequence of mt DNA D-loop of native horse breeds in Xinjiang province, China was examined; it was discovered that the genetic relationship between Kazakh horse and Balikun horse is the closest; the average nucleotide difference was 0.027; the genetic relationship between Kazakh horse and Yanqi horse is closer; the avarage nucleotide difference was 0.029; the genetic relationship between Balikun horse and Yanqi horse is comparatively far; the average nucleotide difference was 0.030. The NJ tree analysis of mt DNA D-loop partial sequence in different haplotypes showed that the position of each native horse breed mixed on different branches; not each breed clustered separately. This result also defined the close genetic relationships between native horse breeds in Xinjiang. (3)The same parts of mt DNA D-loop sequence of Przewalski's wild horse from Jimusaer Wild Horse Breeding Center, Xinjiang province, China was also sequenced and 12 haplotypes were detected. The avarage genetic distance was 0.030; the average haplotype diversity(h) was 1±0.00116; the avarage nucleotide diversity was 2.53%. The results indicate that the mt DNA D-loop partial sequence of captive Przewalski's horses in Jimusaer Wild Horse Breeding Center, Xinjiang province, China.(4)The Kimura 2-parameter genetic distance of partial sequence of mt DNA D-loop of native horse breeds in Xinjiang province, China and Przewalski's horses in Jimusaer Wild Horse Breeding Center, Xinjiang province, China. were examined; it was discovered that the genetic relationship between Przewalski's horse and Kazakh horse is the furthest; the average nucleotide difference was 0.037; the genetic relationship between Przewalski's horse and Balikun horse is closer; the average nucleotide difference was 0.036; the genetic relationship between Przewalski's horse and Yanqi horse is the closest; the average nucleotide difference was 0.034; The NJ tree analysis showed that the native horse breeds and Przewalski's horses were clustered on different branches mixedly. This result indicated that Przewalski's horses and native horse breeds in Xinjiang has close genetic relationship.(5)The phylogenetic tree of mt DNA D-loop partial sequence in 10 Przewalski's horses, 22 haplotypes of Xinjiang native horse breeds which are measured in this study and homologous sequence of some other domestic horses from Gen Bank was constructed using Mega software package. It was discovered that the 22 haplotypes sequence of Xinjiang native horses were clustered on different branches in the phylogenetic tree, there for, we conclude that Xinjiang native horses were originated from multiple maternal ancestor.