Genome‐wide association analysis and gene set enrichment analysis with SNP data identify genes associated with 305‐day milk yield in Holstein dairy cows

Milk production traits, such as 305‐day milk yield (305MY), have been under direct selection to improve production in dairy cows. Over the past 50 years, the average milk yield has nearly doubled, and over 56% of the increase is attributable to genetic improvement. As such, additional improvements in milk yield are still possible as new loci are identified. The objectives of this study were to detect SNPs and gene sets associated with 305MY in order to identify new candidate genes contributing to variation in milk production. A population of 781 primiparous Holstein cows from six central Washington dairies with records of 305MY and energy corrected milk were used to perform a genome‐wide association analysis (GWAA) using the Illumina BovineHD BeadChip (777 962 SNPs) to identify QTL associated with 305MY (P < 1.0 × 10^?5). A gene set enrichment analysis with SNP data (GSEA‐SNP) was performed to identify gene sets (normalized enrichment score > 3.0) and leading edge genes (LEGs) influencing 305MY. The GWAA identified three QTL comprising 34 SNPs and 30 positional candidate genes. In the GSEA‐SNP, five gene sets with 58 unique and 24 shared LEGs contributed to 305MY. Identification of QTL and LEGs associated with 305MY can provide additional targets for genomic selection to continue to improve 305MY in dairy cattle.     

The easy road to genome‐wide medium density SNP screening in a non‐model species: development and application of a 10 K SNP‐chip for the house sparrow (Passer domesticus)

With the advent of next generation sequencing, new avenues have opened to study genomics in wild populations of non‐model species. Here, we describe a successful approach to a genome‐wide medium density Single Nucleotide Polymorphism (SNP) panel in a non‐model species, the house sparrow (Passer domesticus), through the development of a 10 K Illumina iSelect HD BeadChip. Genomic DNA and cDNA derived from six individuals were sequenced on a 454 GS FLX system and generated a total of 1.2 million sequences, in which SNPs were detected. As no reference genome exists for the house sparrow, we used the zebra finch (Taeniopygia guttata) reference genome to determine the most likely position of each SNP. The 10 000 SNPs on the SNP‐chip were selected to be distributed evenly across 31 chromosomes, giving on average one SNP per 100 000 bp. The SNP‐chip was screened across 1968 individual house sparrows from four island populations. Of the original 10 000 SNPs, 7413 were found to be variable, and 99% of these SNPs were successfully called in at least 93% of all individuals. We used the SNP‐chip to demonstrate the ability of such genome‐wide marker data to detect population sub‐division, and compared these results to similar analyses using microsatellites. The SNP‐chip will be used to map Quantitative Trait Loci (QTL) for fitness‐related phenotypic traits in natural populations.     

New resources for genetic studies in Populus nigra: genome‐wide SNP discovery and development of a 12k Infinium array

Whole genome resequencing of 51 Populus nigra (L.) individuals from across Western Europe was performed using Illumina platforms. A total number of 1 878 727 SNPs distributed along the P. nigra reference sequence were identified. The SNP calling accuracy was validated with Sanger sequencing. SNPs were selected within 14 previously identified QTL regions, 2916 expressional candidate genes related to rust resistance, wood properties, water‐use efficiency and bud phenology and 1732 genes randomly spread across the genome. Over 10 000 SNPs were selected for the construction of a 12k Infinium Bead‐Chip array dedicated to association mapping. The SNP genotyping assay was performed with 888 P. nigra individuals. The genotyping success rate was 91%. Our high success rate was due to the discovery panel design and the stringent parameters applied for SNP calling and selection. In the same set of P. nigra genotypes, linkage disequilibrium throughout the genome decayed on average within 5–7 kb to half of its maximum value. As an application test, ADMIXTURE analysis was performed with a selection of 600 SNPs spread throughout the genome and 706 individuals collected along 12 river basins. The admixture pattern was consistent with genetic diversity revealed by neutral markers and the geographical distribution of the populations. These newly developed SNP resources and genotyping array provide a valuable tool for population genetic studies and identification of QTLs through natural‐population based genetic association studies in P. nigra.     

Validating genome‐wide associated signals for clinical mastitis in German Holstein cattle

A validation study for six genomic regions previously identified by a genome‐wide association study for somatic cell score was conducted with data of clinical mastitis in German Holstein cattle. Out of 10 tested SNPs, five on chromosomes 6, 13 and 19 were significantly associated with clinical mastitis (P < 0.05). Three SNPs on chromosomes 6 and 19 had the same direction of effect as those previously reported in the initial genome‐wide association study for somatic cell score. The other two SNPs on chromosome 13 had opposite effects. As well as validating associations within known QTL from previous studies, e.g. chromosomes 6 and 19, novel loci on chromosome 13 were confirmed. Promising candidate genes are, for example: deoxycytidine kinase, immunoglobulin J chain, vitamin D binding protein, forkhead box K2, sodium/hydrogen exchanger 8 and cytoplasmic nuclear factor of activated T‐cells 2. Our confirmation study provides additional evidence for the functional role of the linked genomic regions to immune response. This information can be used as a basis for further functional studies for those potential genes.     

Effect of swine leukocyte antigen‐DQA gene variation on diarrhea in Large White,Landrace, and Duroc piglets

Piglet diarrhea is one of the most common factors that affects the benefits of the swine industry. Although recent studies have shown that exon 2 of SLA‐DQA is associated with piglet resistance to diarrhea, contributions of genetic variation in the additional exon coding regions of this gene remain unclear. Here, we investigated variation in exons 1, 3 and 4 of the SLA‐DQA gene and evaluated their effects on diarrheal infection in 425 suckling piglets. No variation was identified in exon 1. In exon 3, there were eight alleles detected, generated by 14 single nucleotide polymorphisms (SNPs) and three nucleotide deletions, eight SNPs being newly identified. Four allele sequences and three SNPs were identified in exon 4, only one SNP being newly identified. Statistical analysis showed that the genotypes of exon 3 are significantly associated with piglet diarrhea; indeed, genotypes DQA*wb01/wb02 and wb04/wb05 are clearly associated with resistance to piglet diarrhea, as they have the lowest probabilities of infection (P < 0.05). However, no significant association was found between the genotypes of exon 4 and diarrhea (P > 0.05). These results provide important new information concerning the level of genetic diversity at the SLA‐DQA locus and suggest that further genetic association studies of piglet diarrhea resistance should include analyses of both exons 2 and 3 of this locus.     

Genome‐wide association analysis for quantitative trait loci influencing Warner–Bratzler shear force in five taurine cattle breeds

We performed a genome‐wide association study for Warner–Bratzler shear force (WBSF), a measure of meat tenderness, by genotyping 3360 animals from five breeds with 54 790 BovineSNP50 and 96 putative single‐nucleotide polymorphisms (SNPs) within μ‐calpain [HUGO nomenclature calpain 1, (mu/I) large subunit; CAPN1] and calpastatin (CAST). Within‐ and across‐breed analyses estimated SNP allele substitution effects (ASEs) by genomic best linear unbiased prediction (GBLUP) and variance components by restricted maximum likelihood under an animal model incorporating a genomic relationship matrix. GBLUP estimates of ASEs from the across‐breed analysis were moderately correlated (0.31–0.66) with those from the individual within‐breed analyses, indicating that prediction equations for molecular estimates of breeding value developed from across‐breed analyses should be effective for genomic selection within breeds. We identified 79 genomic regions associated with WBSF in at least three breeds, but only eight were detected in all five breeds, suggesting that the within‐breed analyses were underpowered, that different quantitative trait loci (QTL) underlie variation between breeds or that the BovineSNP50 SNP density is insufficient to detect common QTL among breeds. In the across‐breed analysis, CAPN1 was followed by CAST as the most strongly associated WBSF QTL genome‐wide, and associations with both were detected in all five breeds. We show that none of the four commercialized CAST and CAPN1 SNP diagnostics are causal for associations with WBSF, and we putatively fine‐map the CAPN1 causal mutation to a 4581‐bp region. We estimate that variation in CAST and CAPN1 explains 1.02 and 1.85% of the phenotypic variation in WBSF respectively.     

A genome‐wide association study to detect genetic variation for postpartum dysgalactia syndrome in five commercial pig breeding lines

Postpartum dysgalactia syndrome (PDS) in sows is an important disease after parturition with a relevant economic impact, affecting the health and welfare of both sows and piglets. The genetic background of this disease has been discussed and its heritability estimated, but further genetic analyses are lacking in detail. The aim of the current study was to detect loci affecting the susceptibility to PDS through a genome‐wide association approach. The study was designed as a family‐based association study with matched sampling of affected sows and healthy half‐ or full‐sib control sows on six farms. For the study, 597 sows (322 affected vs. 275 healthy control sows) were genotyped on 62 163 single nucleotide polymorphisms (SNPs) using the Illumina PorcineSNP60 BeadChip. After quality control, 585 sows (314 affected vs. 271 healthy control sows) and 49 740 SNPs remained for further analysis. Statistics were performed mainly with the r package genabel and included a principal component analysis. A statistically significant genome‐wide associated SNP was identified on porcine chromosome (SSC) 17. Further promising results with moderate significance were detected on SSC 13 and on an unplaced scaffold with an older annotation on SSC 15. The PRICKLE2 and NRP2 genes were identified as candidate genes near associated SNPs. Several quantitative trait loci (QTL) have been previously described in these genomic regions, including QTL for mammary gland condition, as teat number and non‐functional nipples QTL, as well as QTL for body temperature and gestation length.     

Whole‐genome resequencing‐based QTL‐seq identified candidate genes and molecular markers for fresh seed dormancy in groundnut

The subspecies fastigiata of cultivated groundnut lost fresh seed dormancy (FSD) during domestication and human‐made selection. Groundnut varieties lacking FSD experience precocious seed germination during harvest imposing severe losses. Development of easy‐to‐use genetic markers enables early‐generation selection in different molecular breeding approaches. In this context, one recombinant inbred lines (RIL) population (ICGV 00350 × ICGV 97045) segregating for FSD was used for deploying QTL‐seq approach for identification of key genomic regions and candidate genes. Whole‐genome sequencing (WGS) data (87.93 Gbp) were generated and analysed for the dormant parent (ICGV 97045) and two DNA pools (dormant and nondormant). After analysis of resequenced data from the pooled samples with dormant parent (reference genome), we calculated delta‐SNP index and identified a total of 10,759 genomewide high‐confidence SNPs. Two candidate genomic regions spanning 2.4 Mb and 0.74 Mb on the B05 and A09 pseudomolecules, respectively, were identified controlling FSD. Two candidate genes—RING‐H2 finger protein and zeaxanthin epoxidase—were identified in these two regions, which significantly express during seed development and control abscisic acid (ABA) accumulation. QTL‐seq study presented here laid out development of a marker, GMFSD1, which was validated on a diverse panel and could be used in molecular breeding to improve dormancy in groundnut.     

Development of an integrated 200K SNP genotyping array and application for genetic mapping,genome assembly improvement and genome wide association studies in pear (Pyrus)

Pear (Pyrus; 2n = 34), the third most important temperate fruit crop, has great nutritional and economic value. Despite the availability of many genomic resources in pear, it is challenging to genotype novel germplasm resources and breeding progeny in a timely and cost‐effective manner. Genotyping arrays can provide fast, efficient and high‐throughput genetic characterization of diverse germplasm, genetic mapping and breeding populations. We present here 200K AXIOM^® PyrSNP, a large‐scale single nucleotide polymorphism (SNP) genotyping array to facilitate genotyping of Pyrus species. A diverse panel of 113 re‐sequenced pear genotypes was used to discover SNPs to promote increased adoption of the array. A set of 188 diverse accessions and an F₁ population of 98 individuals from ‘Cuiguan’ × ‘Starkrimson’ was genotyped with the array to assess its effectiveness. A large majority of SNPs (166 335 or 83%) are of high quality. The high density and uniform distribution of the array SNPs facilitated prediction of centromeric regions on 17 pear chromosomes, and significantly improved the genome assembly from 75.5% to 81.4% based on genetic mapping. Identification of a gene associated with flowering time and candidate genes linked to size of fruit core via genome wide association studies showed the usefulness of the array in pear genetic research. The newly developed high‐density SNP array presents an important tool for rapid and high‐throughput genotyping in pear for genetic map construction, QTL identification and genomic selection.     

Effect of polymorphisms in the CAMKMT gene on growth traits in Ujumqin sheep

Our previous genome‐wide association study in sheep revealed that OAR3‐84073899.1 (SNP31) in intron 8 of the CAMKMT gene was significantly associated with post‐weaning gain at the genomic level. Herein, we performed a replication study to investigate single nucleotide polymorphisms (SNPs) within the CAMKMT gene exons, and 1000 bp of the 5′‐ and 3′‐intranslated regions (UTRs) and their associations with growth traits in Ujumqin sheep. Five SNPs were identified through DNA pool sequencing technology: SNP26 in the 5′‐UTR, SNP06 in exon 5, SNP07 in exon 8 and SNP27 and SNP28 in the 3′‐UTR. Six SNPs, including SNP31 in intron 8, were genotyped in the validation group of 343 Ujumqin sheep, and each SNP was classified into three genotypes. The chi‐square test suggested that all the variations were in Hardy–Weinberg equilibrium (P > 0.05) except for SNP28 and SNP31. Linkage disequilibrium analysis showed that SNP07 and SNP31 were strongly linked. An association analysis suggested that SNP06 was significantly associated with chest girth at 6 months of age (P < 0.05). SNP07 exhibited significant correlation with body weight and chest girth at 4 months of age and with body weight, chest girth and chest width at 6 months of age (P < 0.05). SNP27 was highly associated with body weight and chest girth at 4 months of age (P < 0.05), and SNP28 was extremely significantly associated with body weight and chest girth at 4 months of age and with chest girth at 6 months of age (P < 0.01). SNP31 was significantly associated with body weight and shin circumference at 4 months of age and with post‐weaning gain (P < 0.05). Association analysis of the combined effect of SNP07 and SNP31 showed significant correlation with body weight and chest girth at four of months of age (P < 0.05) and with body weight and chest girth at 6 months of age (P < 0.05). These results indicate that the SNPs could be used as meritorious and available genetic markers in growth traits breeding and that the CAMKMT gene may be one of the key candidate genes that affect Ujumqin economic traits.     

Single nucleotide polymorphisms in the insulin‐like growth factor 1 (IGF1) gene are associated with growth‐related traits in farmed Atlantic salmon

Understanding the genetic basis of variation in traits related to growth and fillet quality in Atlantic salmon is of importance to the aquaculture industry. Several growth‐related QTL have been identified via the application of genetic markers. The IGF1 gene is considered a highly conserved and crucial growth‐regulating gene in salmonid species. However, the association between polymorphisms in the IGF1 gene and growth‐related traits in Atlantic salmon is unknown. Therefore, in this study, regions of the Atlantic salmon IGF1 gene were sequenced, aligned and compared across individuals. Three SNPs were identified in the putative promoter (SNP1, g.5763G>T; GenBank no. AGKD01012745 ), intron 1 (SNP2, g.7292C>T; GenBank no. AGKD01012745 ) and intron 3 (SNP3, g.4671A>C; GenBank no. AGKD01133398 ) regions respectively. These SNPs were genotyped in a population of 4800 commercial Atlantic salmon with data on several weight and fillet traits measured at harvest (at approximately 3 years of age). In a mixed model, association analysis of individual SNPs, SNP1 and SNP3 were both significantly associated with several weight traits (P < 0.05). The estimated additive effect on overall harvest weight was approximately 35 and 110 g for SNPs 1 and 3 respectively. A haplotype analysis confirmed the association between genetic variation in the IGF1 gene with overall body weight (P < 0.05) and fillet component traits (P < 0.05). Our findings suggest the identified nucleotide polymorphisms of the IGF1 gene may either affect farmed Atlantic salmon growth directly or be in population‐wide linkage disequilibrium with causal variation, highlighting their possible utility as candidates for marker‐assisted selection in the aquaculture industry.     

Genomic regions affecting backfat thickness and cannon bone circumference identified by genome‐wide association study in a Duroc pig population

We performed a genome‐wide association study using the porcine 60K SNP array to detect QTL regions for nine traits in a three‐generational Duroc samples (n = 651), viz. generations 1, 2 and 3 from a population selected over five generations using a closed nucleus breeding scheme. We applied a linear mixed model for association mapping to detect SNP effects, adjusting for fixed effects (sex and season) and random polygenic effects (reflecting genetic relatedness), and derived a likelihood ratio statistic for each SNP using the efficient mixed‐model association method. We detected a region on SSC6 for backfat thickness (BFT) and on SSC7 for cannon bone circumference (CANNON), with a genome‐wide significance of P < 0.01 after Bonferroni correction. These regions had been detected previously in other pig populations. Six genes are located in the BFT‐associated region, while the CANNON‐associated region includes 66 genes. In the future, significantly associated SNPs, derived by sequencing the coding regions of the six genes in the BFT region, can be used in marker‐assisted selection of BFT, whereas haplotypes constructed from the SSC7 region with strong LD can be used to select for the CANNON trait in our resource family.     

Identification of genetic associations of ECHS1 gene with milk fatty acid traits in dairy cattle

Our previous genome‐wide association study identified 83 genome‐wide significant SNPs and 20 novel promising candidate genes for milk fatty acids in Chinese Holstein. Among them, the enoyl‐CoA hydratase, short chain 1 (ECHS1) and enoyl‐CoA hydratase and 3‐hydroxyacyl CoA dehydrogenase (EHHADH) genes were located near two SNPs and one SNP respectively, and they play important roles in fatty acid metabolism pathways. We herein validated whether the two genes have genetic effects on milk fatty acid traits in dairy cattle. By re‐sequencing the full‐length coding region, partially adjacent introns and 3000 bp up/downstream flanking sequences, we identified 12 SNPs in ECHS1: two in exons, four in the 3′ flanking region and six in introns. The g.25858322C>T SNP results in an amino acid replacement from leucine to phenylalanine and changes the secondary structure of the ECHS1 protein, and single‐locus association analysis showed that it was significantly associated with three milk fatty acids (P = 0.0002–0.0013). The remaining 11 SNPs were found to be significantly associated with at least one milk fatty acid (P = <0.0001–0.0040). Also, we found that two haplotype blocks, consisting of nine and two SNPs respectively, were significantly associated with eight milk fatty acids (P = <0.0001–0.0125). However, none of polymorphisms was observed in the EHHADH gene. In conclusion, our findings are the first to indicate that the ECHS1 gene has a significant genetic impact on long‐chain unsaturated and medium‐chain saturated fatty acid traits in dairy cattle, although the biological mechanism is still undetermined and requires further in‐depth validation.     

Validation of SNP associations with bovine ovulation and twinning rate

Previous work identified SNP associations with twinning rate in the US Holstein population and developed a model for genomic prediction. The current study was conducted to assess the association of these SNPs with twinning rate and ovulation rate in a genetically diverse, outbred population selected for twinning and ovulation rate. A total of 18 SNPs that were components of a prediction equation for twinning rate in Holstein cattle were genotyped on 731 animals from the USDA Meat Animal Research Center production efficiency or twinning population. These 731 individuals were sires and dams well represented in the pedigrees of animals from the twinner population, and their genotypes were used in predicting genotypes for animals in the larger population (n = 16 035). Twinning rate and ovulation rate were analyzed in a two‐trait repeated records analysis with marker associations analyzed individually as fixed effects. Criteria for marker validation were effect estimate with a sign consistent with previous estimates and significance at a nominal P < 0.01. Of the 14 SNPs passing quality control assessments, only one was validated. A SNP in the 5′ flanking region of the IGF1 gene, discovered previously in a positional candidate gene analysis, was significantly associated with twinning rate in the USDA twinning population (P < 0.0002). This SNP may have utility in genomic prediction of twinning rate beyond the Holstein population.     

Validation of genetic polymorphisms on BTA14 associated with carcass trait in a commercial Hanwoo population

The objective of this study was to validate the association of significant SNPs identified from a previous genome‐wide association study with carcass weight (CWT) in a commercial Hanwoo population. We genotyped 13 SNPs located on BTA14 in 867 steers from Korea Hanwoo feedlot bulls. Of these 13 SNPs, five SNPs, namely rs29021868, rs110061498, rs109546980, rs42404006 and rs42303720, were found to be significantly associated (P < 0.001) with CWT. These five significant markers spanned the 24.3 to 29.4 Mb region of BTA14. The most significant marker (rs29021868) for CWT in this study had a 13.07 kg allele substitution effect and accounted for 2.4% of the additive genetic variance in the commercial Hanwoo population. The SNP marker rs109546980 was found to be significantly associated with both CWT (P < 0.001) and eye muscle area (P < 0.001) and could potentially be exploited for marker‐assisted selection in Hanwoo cattle. We also genotyped the ss319607402 variation, which maps to intron2 of PLAG1 gene and which is already reported to be associated with height, to identify any significant association with carcass weight; however, no such association was observed in this Hanwoo commercial population.     

Time‐specific and pleiotropic quantitative trait loci coordinately modulate stem growth in Populus

In perennial woody plants, the coordinated increase of stem height and diameter during juvenile growth improves competitiveness (i.e. access to light); however, the factors underlying variation in stem growth remain unknown in trees. Here, we used linkage‐linkage disequilibrium (linkage‐LD) mapping to decipher the genetic architecture underlying three growth traits during juvenile stem growth. We used two Populus populations: a linkage mapping population comprising a full‐sib family of 1,200 progeny and an association mapping panel comprising 435 unrelated individuals from nearly the entire natural range of Populus tomentosa. We mapped 311 quantitative trait loci (QTL) for three growth traits at 12 timepoints to 42 regions in 17 linkage groups. Of these, 28 regions encompassing 233 QTL were annotated as 27 segmental homology regions (SHRs). Using SNPs identified by whole‐genome re‐sequencing of the 435‐member association mapping panel, we identified significant SNPs (P ≤ 9.4 × 10^?7) within 27 SHRs that affect stem growth at nine timepoints with diverse additive and dominance patterns, and these SNPs exhibited complex allelic epistasis over the juvenile growth period. Nineteen genes linked to potential causative alleles that have time‐specific or pleiotropic effects, and mostly overlapped with significant signatures of selection within SHRs between climatic regions represented by the association mapping panel. Five genes with potential time‐specific effects showed species‐specific temporal expression profiles during the juvenile stages of stem growth in five representative Populus species. Our observations revealed the importance of considering temporal genetic basis of complex traits, which will facilitate the molecular design of tree ideotypes.     

Genetic markers that influence feed efficiency phenotypes also affect cattle temperament as measured by flight speed

Flight speed is a predictive indicator of cattle temperament and is associated with feed efficiency phenotypes. Genetic markers associated with both traits may assist with selection of calmer animals with improved economic value. A preliminary genome‐wide association study determined chromosomal regions on BTA9, and 17 were associated with flight speed. The genes quaking (QKI), glutamate receptor, ionotropic, AMPA 2 (GRIA2) and glycine receptor β (GLRB) were identified in these regions as potential functional candidates. Beef steers (n = 1057) were genotyped with SNPs located within and flanking these genes. One SNP located near QKI and one near GRIA2 were nominally associated with flight speed (P ≤ 0.05) although neither was significant after Bonferroni correction. Several studies have shown a correlation between flight speed and feed intake or gain; therefore, we also analyzed SNPs on BTA6:38–39 Mb known to be associated with average daily gain (ADG) and average daily feed intake (ADFI) for association with flight speed. Several SNPs on BTA6 were associated with flight speed (P ≤ 0.005), and three were significant after Bonferroni correction. These results suggest that the genes tested are unlikely to contribute to flight speed variation for our cattle population, but SNPs on BTA6 associated with ADG and ADFI may influence temperament. Use of these markers to select for economically important feed efficiency phenotypes may produce cattle with more desirable temperaments.     

A genome‐wide association study for a proxy of intermuscular fat level in the Italian Large White breed identifies genomic regions affecting an important quality parameter for dry‐cured hams

Intermuscular fat content in protected designations of origin dry‐cured hams is a very important meat quality trait that affects the acceptability of the product by the consumers. An excess in intermuscular fat (defined as the level of fat deposition between leg muscles) is a defect that depreciates the final product. In this study we carried out a genome‐wide association study for visible intermuscular fat (VIF) of hams in the Italian Large White pig breed. This trait was evaluated on the exposed muscles of green legs in 1122 performance‐tested gilts by trained personnel, according to a classification scale useful for routine and cheap evaluation. All animals were genotyped with the Illumina PorcineSNP60 BeadChip. The genome‐wide association study identified three QTL regions on porcine chromosome 1 (SSC1; accounting for ~79% of the SNPs below the 5.0E?04 threshold) and SSC2, two on SSC7 and one each on SSC3, SSC6, SSC9, SSC11, SSC13, SSC15, SSC16 and SSC17. The most significant SNP (ALGA0004143 on SSC1 at 77.3 Mb; P_FDR < 0.05), included in the largest QTL region which spanned about 6.8 Mb on SSC1, is located within the glutamate ionotropic receptor kainate type subunit 2 (GRIK2) gene. Functional annotation of all genes included in QTL regions for VIF suggested that intermuscular fat in the Italian Large White breed is a complex trait apparently influenced by complex biological mechanisms also involving obesity‐related processes. These QTL target mainly chromosome regions different from those affecting subcutaneous and intramuscular fat deposition.     

Genomewide single nucleotide polymorphism discovery in Atlantic salmon (Salmo salar): validation in wild and farmed American and European populations

A considerable number of single nucleotide polymorphisms (SNPs) are required to elucidate genotype–phenotype associations and determine the molecular basis of important traits. In this work, we carried out de novo SNP discovery accounting for both genome duplication and genetic variation from American and European salmon populations. A total of 9 736 473 nonredundant SNPs were identified across a set of 20 fish by whole‐genome sequencing. After applying six bioinformatic filtering steps, 200 K SNPs were selected to develop an Affymetrix Axiom^® myDesign Custom Array. This array was used to genotype 480 fish representing wild and farmed salmon from Europe, North America and Chile. A total of 159 099 (79.6%) SNPs were validated as high quality based on clustering properties. A total of 151 509 validated SNPs showed a unique position in the genome. When comparing these SNPs against 238 572 markers currently available in two other Atlantic salmon arrays, only 4.6% of the SNP overlapped with the panel developed in this study. This novel high‐density SNP panel will be very useful for the dissection of economically and ecologically relevant traits, enhancing breeding programmes through genomic selection as well as supporting genetic studies in both wild and farmed populations of Atlantic salmon using high‐resolution genomewide information.     

Genome‐wide association and genomic prediction for biomass yield in a genetically diverse Miscanthus sinensis germplasm panel phenotyped at five locations in Asia and North America

To improve the efficiency of breeding of Miscanthus for biomass yield, there is a need to develop genomics‐assisted selection for this long‐lived perennial crop by relating genotype to phenotype and breeding value across a broad range of environments. We present the first genome‐wide association (GWA) and genomic prediction study of Miscanthus that utilizes multilocation phenotypic data. A panel of 568 Miscanthus sinensis accessions was genotyped with 46,177 single nucleotide polymorphisms (SNPs) and evaluated at one subtropical and five temperate locations over 3 years for biomass yield and 14 yield‐component traits. GWA and genomic prediction were performed separately for different years of data in order to assess reproducibility. The analyses were also performed for individual field trial locations, as well as combined phenotypic data across groups of locations. GWA analyses identified 27 significant SNPs for yield, and a total of 504 associations across 298 unique SNPs across all traits, sites, and years. For yield, the greatest number of significant SNPs was identified by combining phenotypic data across all six locations. For some of the other yield‐component traits, greater numbers of significant SNPs were obtained from single site data, although the number of significant SNPs varied greatly from site to site. Candidate genes were identified. Accounting for population structure, genomic prediction accuracies for biomass yield ranged from 0.31 to 0.35 across five northern sites and from 0.13 to 0.18 for the subtropical location, depending on the estimation method. Genomic prediction accuracies of all traits were similar for single‐location and multilocation data, suggesting that genomic selection will be useful for breeding broadly adapted M. sinensis as well as M. sinensis optimized for specific climates. All of our data, including DNA sequences flanking each SNP, are publicly available. By facilitating genomic selection in M. sinensis and Miscanthus × giganteus, our results will accelerate the breeding of these species for biomass in diverse environments.