Genetic diversity in Tyva horses derived from polymorphism of blood systems and microsatellite DNA

Tuva horse breed is one of the most promising local breeds of universal use. Tuva horses are well adapted to year-round pasture grazing, resistant to disease, and, therefore, suitable for low-cost meat production. Due to relatively isolated location of the population which has ancient origin uva horses are undoubtedly of interest both genetically and evolutionarily. For allele pool study we sampled blood ( n = 32) and hair ( n = 35) specimens from Tyva horses reared at two farms of Tuva Research Institute of Agriculture in 2009-2016. Genetic analysis was carried out according to the authority certified by ISAG (International Society of Animal Genetics). The study of polymorphic blood system and microsatellite DNA loci showed the Tyva horses to be fairly high genetically diverse on structural genes and microsatellite DNA. High polymorphism was found in Tf, Al, Es loci and especially in D system of blood groups. Dcgm, Dbcm and Dd alleles were comparatively high-frequent, while Dad, Dde and Ddk were relatively rare. As to microsatellite DNA polymorphism, there were 113 alleles in 17 loci (6.65 alleles per locus on average), indicating high genetic diversity in the Tyva horse breed. Amon the microsatellite DNA loci found, VHLP, АНТ4P, HMS7J, ASB23L, ASB2B, HMS3N, ASB17Q, LEX3K, LEX3P, HMS1I, HMS1N and HMS1R were rare, of which HMS1R was unique as not found in horses of European origin (L.H.P. Van de Goor et al., 2010). There were from 4 to 9 alleles in the studied microsatellite loci, and the average number of effective allele per locus (Ae) made 4.20 being rather high even for local breeds. Loci ASB17 (10 alleles), АНТ4 (9 alleles), VHL20 (9 alleles), ASB2 (9 alleles) and ASB23 (8 alleles) were the most diverse. The genetic population analysis demonstrated good correspondence between the observed (Ho = 0.748) and the expected (He = 0.742) heterozygosis level and the absence of inbreeding (FIS = -0.008) in the Tyva horses. The highest similarity was found out between Ttva horse and Khakass horse (0.823), and also between Tuva horse and Mongolian horse (0.822) which areas border on the South and South-East. The data of whole genome association analysis (J.R. Mickelsn et al., 2012) are also in line with genetic distance that we calculated based on 17 microsatellite loci polymorphism. The visualized dendrogramm indicated common origin of the Tyva and Mongolian horses, which make a common branch in the evolutionary tree of horse breeds. Our findings indicate a high level of genetic plasticity of Tyva horses promising for breeding. In general, we can conclude that the studied population of Tyva horses is characterized by the original allele pool, including a number of rare alleles that must be preserved in the breed at rearing and genetic improvement.