Biodiversity assessment in interspecies hybrids of the genus Ovis using STR and SNP markers

Introgression of wild and domestic species is regarded as a promising way to improve genetic diversity in populations of farm animals. The aim of our study was to investigate the influence of introgression of the wild species (argali) on genetic diversity of interspecific hybrids with domestic sheep using STR and SNP markers. Samples included original parental forms: Romanov sheep (ROM, n = 35), representing the «domestic» form ( Ovis aries ), and argali (OAM, n = 10), characterizing the «wild» form ( O. ammon polii ), male hybrid F1, obtained by surgical insemination of Romanov ewe by argali sperm (F1, n = 1), and back crosses obtained by crossing Romanov ewes with hybrid F1 ram (BC1, n = 38) and hybrid BC1 rams (BC2, n = 14). The analysis of 11 STR loci (BLT001B, CSRD247, FCB20, CSAP36, MAF65, McM147, OarCP49, D5S2, HSC, BMS2213 and INRA23) was carried out on the ABI PRISM 3130xl genetic analyzer. For SNP genotyping we used Ovine SNP50K BeadChip. After quality control, 9 STR loci and 8591 SNPs were left for the analysis. Statistical calculations were performed in GenAIEx 6.5, PLINK v1.07, HP-Rare 1.1, GENETIX 4.05 and STRUCTURE 2.3.4. Regardless the type of DNA marker, ROM, compared with OAM, was characterized by a higher level of genetic diversity, assessed by observed heterozygosity (Ho) and allelic richness (Ar). Hybridization resulted in an increase in this parameter in the F1 hybrid. In groups BC1 and BC2, the Ho values, calculated per STR and SNP, were higher than similar in the parental forms. In BC1 and BC2 groups the Ar values, estimated by SNP-markers, were reducing in comparison with F1 and were intermediate in comparison with the same in the parental forms. The changes in the Ar values, based on STR data, had the character of a trend in groups BC1 and BC2. Principal component analysis (PCA), performed by using SNP-markers, showed a more objective distribution pattern of the studied animals according to their origin in the coordinates space. In case of SNP data, PC1 was sufficient for clearly differentiation of groups OAM, ROM, F1 and BC1 + BC2. In summary, the first two components (PC1 and PC2) were responsible for 25.87 % of the SNP variability and for only 12.46 % of the STR variability. Principal component 3 (PC3), which was responsible for 6.16 % of SNP variability, made it possible to differentiate BC1 and BC2 groups, whereas at the application of STR these groups were localized as a common cluster. The results of STRUCTURE analysis showed that association of the investigated individuals into clusters, based on STR-profiles, did not match their origin, while the formation of clusters by SNP-markers was corresponded to the actual origin of animals. We found that both types of tested DNA markers were suitable for detecting changes in genetic diversity through hybrids generation. Nevertheless, a significant advantage of using multiple SNP-markers for the differentiation of hybrids from the parental forms was shown.