High-density genotyping reveals signatures of selection related to acclimation and economically important traits in 15 local sheep breeds from Russia

Domestication and centuries of selective breeding have changed genomes of sheep breeds to respond to environmental challenges and human needs. The genomes of local breeds, therefore, are valuable sources of genomic variants to be used to understand mechanisms of response to adaptation and artificial selection. As a step toward this we performed a high-density genotyping and comprehensive scans for signatures of selection in the genomes from 15 local sheep breeds reared across Russia

Genomic assessment and phenotypic characteristics of F2 resource sheep population

The article presents the results of assessment of genetic diversity and Principal Component Analysis (PCA) in the re-source sheep population, originated from crossing of fast-growing (Katahdin) and slow growing (Romanov) breeds for QTL mapping and search for candidate genes associated with growth rate. The study was conducted on 88 sheep from the resource population, including two unrelated families that have been reared in the Moscow region since 2017. Each family consists of a Katahdin ram (founder), Romanov’s ewes (mothers), F1 hybrids, and two groups of backcrosses. All sheep were genotyped using a high-density DNA chip Illumina Ovine Infinium® HD SNP BeadChip (~ 600 thousand SNP markers). SNP markers were filtered in the PLINK v.1.90. PCA was performed in PLINK v.1.90 and visualized in R package ggplot2. The genetic diversity indices (Ho, uHe, Ar, FIS) were calculated in R package “diveRsity”. It was established that both crosses had higher level of genetic diversity in comparison with the mother breed. F1 hybrids were characterized by the highest level of observed heterozygosity (Ho = 0.409-0.407), while Ho ranged from 0.382 to 0.396 for the backcrosses, respectively. The expected heterozygosity ranged from 0.329 to 0.356 in the groups from the resource population. Allelic richness was high in all studied groups (more than 1.849). PCA showed that the mated parent breeds were highly differentiated, as it should be in successful establishment of the resource population. The phenotypic characteristic of the backcrosses on live weight and nine body measurements at 9, 42 and 90 days is given. The coefficients of variation were the highest by live weight (17.0-19.0%), body length (15.5-22.3%) and oblique body length (16.2% and 22.7%) at 90 days. The results are intermediate and create a geno-typic and phenotypic base to perform GWAS at the next stage of our study

A comprehensive analysis of the genetic diversity and environmental adaptability in worldwide Merino and Merino-derived sheep breeds

BACKGROUND: To enhance and extend the knowledge about the global historical and phylogenetic relationships between Merino and Merino-derived breeds, 19 populations were genotyped with the OvineSNP50 BeadChip specifically for this study, while an additional 23 populations from the publicly available genotypes were retrieved. Three complementary statistical tests, Rsb (extended haplotype homozygosity between-populations), XP-EHH (cross-population extended haplotype homozygosity), and runs of homozygosity (ROH) islands were applied to identify genomic variants with potential impact on the adaptability of Merino genetic type in two contrasting climate zones. RESULTS: The results indicate that a large part of the Merino's genetic relatedness and admixture patterns are explained by their genetic background and/or geographic origin, followed by local admixture. Multi-dimensional scaling, Neighbor-Net, Admixture, and TREEMIX analyses consistently provided evidence of the role of Australian, Rambouillet and German strains in the extensive gene introgression into the other Merino and Merino-derived breeds. The close relationship between Iberian Merinos and other South-western European breeds is consistent with the Iberian origin of the Merino genetic type, with traces from previous contributions of other Mediterranean stocks. Using Rsb and XP-EHH approaches, signatures of selection were detected spanning four genomic regions located on Ovis aries chromosomes (OAR) 1, 6 and 16, whereas two genomic regions on OAR6, that partially overlapped with the previous ones, were highlighted by ROH islands. Overall, the three approaches identified 106 candidate genes putatively under selection. Among them, genes related to immune response were identified via the gene interaction network. In addition, several candidate genes were found, such as LEKR1, LCORL, GHR, RBPJ, BMPR1B, PPARGC1A, and PRKAA1, related to morphological, growth and reproductive traits, adaptive thermogenesis, and hypoxia responses. CONCLUSIONS: To the best of our knowledge, this is the first comprehensive dataset that includes most of the Merino and Merino-derived sheep breeds raised in different regions of the world. The results provide an in-depth picture of the genetic makeup of the current Merino and Merino-derived breeds, highlighting the possible selection pressures associated with the combined effect of anthropic and environmental factors. The study underlines the importance of Merino genetic types as invaluable resources of possible adaptive diversity in the context of the occurring climate changes

Study of genetic diversity and differentiation of regional populations of Romanov sheep using micro satellite markers

The Romanov breed is the most interesting local Russian sheep breed with unique biological traits (out-ofseason breeding ability, prolificacy). Conservation of genetic resources of the breed requires constant careful monitoring using DNA markers. In this regard, the aim of our work was to compare the parameters of the allele pool and genetic diversity, as well as to assess genetic similarity of regional populations of the Romanov breed in comparison with archetypal animals. Tissue samples were selected in different regions of Russia (Yaroslavl, Ryazan and Tula regions, Republics of Khakassia and Komi). Polymorphism of 11 microsatellites was studied with the genetic analyzer АВІЗ 130x1. We estimated an average number of alleles (Na), effective number of alleles (Ne), number of informative alleles (Na>5%), observed (Ho) and expected heterozygosity (He), fixation index (FIS), constructed Neighbour-Net and carried out PCoA and cluster analyzes. The Khakass population was characterized by the greatest allelic diversity: Na = 11.30; Ne = 5.99 and Na>5% = 5.50 alleles, while minimal Ne (3.95) and Na>5% (4.30) were detected for the first and second Yaroslavl populations, respectively. Deficiency of heterozygotes from 6 to 19.5% was observed in all groups, except for the Tula population. Based on the results of Neighbour-Net, PCoA and cluster analysis, genetic isolation of three Yaroslavl populations was found. Also, a certain genetic detachment of the Ryazan population (Fst from 0.038 to 0.059) was revealed. Thus, we demonstrated that the parameters of allele pool and the indices of genetic diversity can vary greatly within the breed. In addition, it has been established that the Yaroslavl populations of the Romanov breed still represent a separate group

Polymorphism of microsatellite loci OarCP549, CSRD247, FCB20 and MAF65 in sheep

Rostov Region is one of the most important regions of sheep breeding in Russia. The Salsk breed of sheep is created as a result of many years work of breeders in the Rostov region. Studies on the genetic diversity of domestic breeds of sheep are a prerequisite for their conservation, further improvement and use for the needs of the modern agro-industrial complex of the Russian Federation. The aim of the work is to study polymorphism of microsatellite loci OarCP549, CSRD247, FCB20, and MAF65 in sheep of Salsk breed. Studies were carried out on sheep of the Salsk breed (n = 95, PZ «Belozernoe», Rostov Region). Analysis of microsatellites was performed on sixteen-capillary genetic analyzer ABI3130xl Genetic Analyzer. To estimate polymorphism of loci it was taken into account: the Number of Alleles per locus (NA); Observed (Ho) and the Expected (He) Heterozygosity, the Effective Number of Alleles per locus (Ae). The highest Number of Alleles (NA = 17) and the Effective Number of Alleles (Ae = 7) was determined from the locus OarCP49 in the sheep of the Salsk breed. At other loci, the Number of Alleles was 15, 12 and 9, and the Effective Number of Alleles was 5.56, 5.33 and 3.85 respectively for CSRD247, FCB20 and MAF65. The heterozygote deficiency in the population is noted at the loci CSRD247 and MAF65. Average index of fixation for four loci was 0.094. The results of the work showed the polymorphism of microsatellite loci OarCP49, CSRD247, FCB20 and MAF65 and the expediency of their inclusion in the panel of DNA markers for assessing the genetic diversity and authenticity of the origin for the sheep of Salsk breed