The genetic structure of cattle populations (Bos taurus) in northern Eurasia and the neighbouring Near Eastern regions: implications for breeding strategies and conservation

We investigated the genetic structure and variation of 21 populations of cattle (Bos taurus) in northern Eurasia and the neighbouring Near Eastern regions of the Balkan, the Caucasus and Ukraine employing 30 microsatellite markers. By analyses of population relationships, as well as by a Bayesian-based clustering approach, we identified a genetic distinctness between populations of modern commercial origin and those of native origin. Our data suggested that northern European Russia represents the most heavily colonized area by modern commercial cattle. Further genetic mixture analyses based on individual assignment tests found that native Red Steppe cattle were also employed in the historical breeding practices in Eastern Europe, most probably for incorporating their strong and extensive adaptability. In analysis of molecular variance, within-population differences accounted for approximately 90% of the genetic variation. Despite some correspondence between geographical proximity and genetic similarity, genetic differentiation was observed to be significantly associated with the difference in breeding purpose among the European populations (percentage of variance among groups and significance: 2.99%, P = 0.02). Our findings give unique genetic insight into the historical patterns of cattle breeding practices in the former Soviet Union. The results identify the neighbouring Near Eastern regions such as the Balkan, the Caucasus and Ukraine, and the isolated Far Eastern Siberia as areas of 'genetic endemism', where cattle populations should be given conservation priority. The results will also be of importance for cost-effective management of their future utilization.     

Genetic differentiation between the Old and New types of Serbian Tsigai sheep

Two Tsigai sheep populations exist in Serbia: the Old type, called Čokan, and the New type. It is assumed that the New type results from upgrading Tsigai sheep with exotic genetic material. We investigated genetic diversity and differentiation of these types by analysing 23 autosomal microsatellites. Tests for Hardy-Weinberg proportions, linkage equilibrium between genotypes across loci and the calculation of inbreeding coefficients were performed and the deficiency in the number of alleles within the Tsigai types was examined using a Wilcoxon sign-rank test. The New type displayed a higher level of genetic variability than the Čokan in terms of allele numbers, but the New Tsigai showed a pattern of heterozygosity deficiency. The positive f value for the Čokan suggests the occurrence of inbreeding in this type. The proportion of linkage disequilibrium was below that expected by chance. Exclusion of two loci in Hardy-Weinberg disequilibrium did not alter our conclusions based on the entire data set i.e. the two Tsigai types are clearly differentiated and the New Tsigai type has been influenced by crossbreeding. Therefore, the Čokan Tsigai should be considered as a distinct endangered breed in the FAO classification.     

The characteristics of the genetic relations between different breeds and crossbreeds of sheep

Frequency of occurrence of antigens belonging to 7 systems of blood groups in four breeds of sheep as well as two crosses of the first generation Tsigai X Ostfrisian; Ostfrisian X Tsigai) has been studied. A phylogenetic affinity between them is presented. Indices of genetic distances between breeds and crosses are calculated. The dendrogram demonstrates the existence of two clusters: the first has been formed with the Caucasian, Ostfrisian, Tsigai breeds and both crosses of the first generation: the second--with Astrakhan breed. The analysis of the results obtained shows that dendrogram constructed with regard for the frequency of blood antigens reflects real relations of the investigated sheep breeds according to the adopted systems.     

Globally dispersed Y chromosomal haplotypes in wild and domestic sheep

To date, investigations of genetic diversity and the origins of domestication in sheep have utilised autosomal microsatellites and variation in the mitochondrial genome. We present the first analysis of both domestic and wild sheep using genetic markers residing on the ovine Y chromosome. Analysis of a single nucleotide polymorphism (oY1) in the SRY promoter region revealed that allele A-oY1 was present in all wild bighorn sheep (Ovis canadensis), two subspecies of thinhorn sheep (Ovis dalli), European Mouflon (Ovis musimon) and the Barbary (Ammontragis lervia). A-oY1 also had the highest frequency (71.4%) within 458 domestic sheep drawn from 65 breeds sampled from Africa, Asia, Australia, the Caribbean, Europe, the Middle East and Central Asia. Sequence analysis of a second locus, microsatellite SRYM18, revealed a compound repeat array displaying fixed differences, which identified bighorn and thinhorn sheep as distinct from the European Mouflon and domestic animals. Combined genotypic data identified 11 male-specific haplotypes that represented at least two separate lineages. Investigation of the geographical distribution of each haplotype revealed that one (H6) was both very common and widespread in the global sample of domestic breeds. The remaining haplotypes each displayed more restricted and informative distributions. For example, H5 was likely founded following the domestication of European breeds and was used to trace the recent transportation of animals to both the Caribbean and Australia. A high rate of Y chromosomal dispersal appears to have taken place during the development of domestic sheep as only 12.9% of the total observed variation was partitioned between major geographical regions.     

Sheep mitochondrial DNA variation in European, Caucasian, and Central Asian areas

Three distinct mitochondrial maternal lineages (haplotype Groups A, B, and C) have been found in the domestic sheep. Group B has been observed primarily in European domestic sheep. The European mouflon carries this haplotype group. This could suggest that European mouflon was independently domesticated in Europe, although archaeological evidence supports sheep domestication in the central part of the Fertile Crescent. To investigate this question, we sequenced a highly variable segment of mitochondrial DNA (mtDNA) in 406 unrelated animals from 48 breeds or local varieties. They originated from a wide area spanning northern Europe and the Balkans to the Altay Mountains in south Siberia. The sample included a representative cross-section of sheep breeds from areas close to the postulated Near Eastern domestication center and breeds from more distant northern areas. Four (A, B, C, and D) highly diverged sheep lineages were observed in Caucasus, 3 (A, B and C) in Central Asia, and 2 (A and B) in the eastern fringe of Europe, which included the area north and west of the Black Sea and the Ural Mountains. Only one example of Group D was detected. The other haplotype groups demonstrated signs of population expansion. Sequence variation within the lineages implied Group A to have expanded first. This group was the most frequent type only in Caucasian and Central Asian breeds. Expansion of Group C appeared most recently. The expansion of Group B involving Caucasian sheep took place at nearly the same time as the expansion of Group A. Group B expansion for the eastern European area started approximately 3,000 years after the earliest inferred expansion. An independent European domestication of sheep is unlikely. The distribution of Group A variation as well as other results are compatible with the Near East being the domestication site. Groups C and D may have been introgressed later into a domestic stock, but larger samples are needed to infer their geographical origin. The results suggest that some mitochondrial lineages arrived in northern Europe from the Near East across Russia.     

Y chromosome haplotype diversity of domestic sheep (Ovis aries) in northern Eurasia

Variation in two SNPs and one microsatellite on the Y chromosome was analyzed in a total of 663 rams representing 59 breeds from a large geographic range in northern Eurasia. SNPA‐oY1 showed the highest allele frequency (91.55%) across the breeds, whereas SNPG‐oY1 was present in only 56 samples. Combined genotypes established seven haplotypes (H4, H5, H6, H7, H8, H12 and H19). H6 dominated in northern Eurasia, and H8 showed the second‐highest frequency. H4, which had been earlier reported to be absent in European breeds, was detected in one European breed (Swiniarka), whereas H7, which had been previously identified to be unique to European breeds, was present in two Chinese breeds (Ninglang Black and Large‐tailed Han), one Buryatian (Transbaikal Finewool) and two Russian breeds (North Caucasus Mutton‐Wool and Kuibyshev). H12, which had been detected only in Turkish breeds, was also found in Chinese breeds in this work. An overall low level of haplotype diversity (median h = 0.1288) was observed across the breeds with relatively higher median values in breeds from the regions neighboring the Near Eastern domestication center of sheep. H6 is the dominant haplotype in northwestern and eastern China, in which the haplotype distribution could be explained by the historical translocations of the H4 and H8 Y chromosomes to China via the Mongol invasions followed by expansions to northwestern and eastern China. Our findings extend previous results of sheep Y chromosomal genetic variability and indicate probably recent paternal gene flows between sheep breeds from distinct major geographic regions.