【Objective】The purposes of this study were to analyze the variation of teat number, to explore the quantitative trait locus (QTL) and candidate genes related to teat number, and to provide important molecular markers for the breeding of pig teat number.【Method】This study accurately measured left, right, total teat number of 709 Suhuai pigs (335 fattening pigs and 374 breeding pigs). Fattening pigs were selected for 80K chip genotyping and the heritability and genomic estimated breeding value (GEBV) of left, right and total teat number were calculated by chip data. Based on the rank of GEBV and phenotype of teat number, the top 10% individuals and the bottom 10% individuals were selected for Fixation Index (FST) analysis to detect highly differentiated loci. Then, the loci associated with teat number were identified by genome wide association analysis (GWAS) and loci which were highly differentiated and significantly associated with teat number were selected as candidate loci. Genes located near candidate loci and related to teat number after functional annotation were selected as candidate genes. Finally, the association analyses between the most significant candidate loci on each chromosome and teat number of 709 Suhuai pigs were performed to verify the significance of the above loci.【Result】The variation coefficients of left, right and total teat number of Suhuai fattening pigs were 10.20%, 9.26% and 8.50%, respectively, and the heritability were 0.212, 0.257 and 0.312, respectively. Based on FST and GWAS analyses, a total of 20 candidate loci on Sus scorfa chromosomes (SSC) 7, 13, 16 and 18 for teat number were identified and these candidate loci could explain 5.49%-8.03% of the phenotypic variance. Among them, locus rs80894106 on SSC7 associated with total teat number was consistent with the reported candidate locus of total teat number based on Large white and Duroc pig populations, but candidate loci rs81444134 (26.51 Mb, SSC13) and rs81233299 (8.13 Mb, SSC18) of left teat number were newly discovered loci related to teat number. Interestingly, candidate loci of left, right and total teat number were mainly concentrated in the 6.36-10.66 Mb interval on SSC16; Linkage disequilibrium (LD) analysis found that candidate loci in 7.47-8.27 Mb interval fit into a 795 kb haplotype block, and this haplotype block was a newly discovered candidate area that affected teat number; rs337606862 (7.47 Mb) in the haplotype block was the most significantly SNP associated with the left and total teat number, and three loci in the haplotype block were all located on the intron of cadherin 18 (CDH18) gene; CDH18 gene encoded type II cadherin, and cadherin was related to the identification, sorting, proliferation, apoptosis of cells in developing tissue and the occurrence of breast cancer. Thus, CDH18 might be a new candidate gene that affected pig teat number. In addition, the most significant loci rs81444134, rs80894106, rs337606862 and rs81233299 on 4 chromosomes were genotyped in 709 Suhuai pigs in this study. After association analysis, these loci were significantly associated with teat number, and could be used as potential molecular markers for the selection of teat number.【Conclusion】In this study, 20 loci significantly related to teat number were identified in Suhuai pig population by genome analysis. Among them, 26.51 Mb on SSC13 and 8.13 Mb on SSC18 were new candidate QTLs for teat number. The 7.47-8.27 Mb on SSC16 was also a newly discovered candidate QTL for teat number, and CDH18 gene in this interval might be a new candidate gene that affected the formation of pig teat.

The number of ribs (NR) and carcass length (CL) are important economic traits in pig breeding programs. Pigs with a higher NR and longer CL produce greater pork yields. In the present study, Suhuai pigs with NR and CL phenotypes were genotyped using the Neogen® GGP Porcine 80 K SNP array to identify the QTL affecting NR and CL and dissect the candidate genes for the two traits. The SNP-chip data was imputed to the whole-genome sequence (iWGS) to increase the probability of identifying causal variants. Through genome-wide association studies (GWAS) based on both chip and iWGS data, significant SNPs were detected on Sus scrofa chromosome (SSC) 1, SSC4 and SSC7 for NR and on SSC5, SSC16 and SSC17 for CL. Moreover, two SNPs (H3GA0022644 and WU_10.2_7_103460706) on SSC7 detected in chip-based GWAS were significantly associated with both NR and CL. Through Bayes fine mapping, one reported QTL for NR on SSC7 and two reported QTL for CL on SSC17 were verified, and two new QTL (SSC1: 14.05-15.84 Mb and SSC4: 64.83-66.59 Mb) affecting NR and two new QTL (SSC5: 58.31-59.84 Mb and SSC16: 22.98-23.43 Mb) affecting CL were detected. According to the biological functions of genes, MTHFD1L on SSC1 and SULF1 on SSC4 are novel functional candidate genes for NR, and EMP1 on SSC5 and EGFLAM on SSC16 are novel functional candidate genes for CL. Overall, our findings provide a basis for identifying new causal genes and mutations affecting NR and CL.

Vulvar size and angle are meaningful traits in pig production. Sows with abnormal vulva generally show reproductive disorders. In order to excavate candidate loci and genes associated with pig’s vulvar traits, 270 Suhuai pigs with vulvar phenotype were genotyped by a porcine single nucleotide polymorphisms (SNP) Chip. Then, Chip data were imputed using resequenced data of 30 Suhuai pigs as a reference panel. Next, we estimated the heritability and performed a genome-wide association study (GWAS) for vulvar traits. The heritabilities for the traits vulvar length (VL), vulvar width (VW) and vulvar angle (VA) in this pig population were 0.23, 0.32 and 0.22, respectively. GWAS based on Chip data identified nine significant SNPs on the Sus scrofa chromosomes (SSC) 2, 7, 9 and 13 for VL or VW. GWAS based on imputed data identified 11 new quantitative trait loci (QTL) on SSC1, 2, 7, 8, 9, 11, 13, 16 and 17 for VL or VW. The most significant QTL for VL on SSC2 were refined to a 3.48–3.97 Mb region using linkage disequilibrium and linkage analysis (LDLA). In this refined region, FGF19 and CCND1, involved in the development of the reproductive tract, cell growth and vulvar cancer, could be new candidate genes affecting VL. Our results provided potential genetic markers for the breeding of vulvar traits in pigs and deepened the understanding of the genetic mechanism of vulvar traits.

旨在鉴定影响猪群体滴水损失变异的相关候选基因,为猪肉质选育奠定基础.本研究利用478头体质健康,平均日龄为237.95 d的苏淮猪个体,其中阉公猪290头,母猪188头.采集所有个体的背最长肌样本后,采用吊袋法测定滴水损失(drip loss,DL)表型,计算群体滴水损失估计育种值(estimated breeding value,EBV),选择其中EBV极高(N=48)和极低(N=48)各10％的个体进行猪80K芯片基因分型.借助群体分化指数(fixation in-dex,Fst)和基于单倍型信息的单倍型积分值(integrated haplotype score,iHS)方法对苏淮猪进行全基因组选择信号检测,选择| iHS|值在前5％,同时Fst值≥0.15的SNP位点作为受选择的位点,接着对受选择SNP上、下游各50 kb的区域进行基因注释,并对所有基因进行KEGG和GO富集分析,鉴别与猪滴水损失相关的候选基因.通过对芯片分型数据质控后,96个样本的51 705个有效SNPs用于后续分析.通过Fst和iHS选择信号合并分析,共筛选出175个受选择的SNPs,主要位于1、6、7、11号染色体上,其中仅有27个SNPs位于已报道的影响猪滴水损失的QTL区域上.对受选择SNP位点附近区域进行基因注释显示,175个SNPs涉及到73个基因,其中多个基因被报道与肌肉发育以及细胞氧化应激等功能相关,包括PACRG、EZR、MRTFA、LCP1和VKORC1L1基因,这5个基因都是新发现的功能上与猪滴水损失有关的候选基因.选择3个位于功能候选基因上,同时又位于QTL区域内的SNPs进行苏淮猪全群分型,并与滴水损失进行关联性分析.结果发现,位于MRTFA基因上的rs340037952位点与苏淮猪群体滴水损失存在显著关联(P＜0.05),位于VKORC1L1基因上的rs320624660与苏淮猪群体滴水损失存在极显著关联(P＜0.01).本研究通过选择信号分析找到175个受选择的SNPs,基因功能注释鉴别到5个影响滴水损失的候选基因,还分别在MRTFA和VKORC1L1基因上鉴别到与苏淮猪群体的滴水损失存在显著关联的位点:rs340037952和rs320624660,为后续猪滴水损失性状的选育提供了前期基础.

旨在解析太湖流域地方猪品种内部遗传结构,鉴定梅山猪亚群间、二花脸群体间和米猪群体间体重体尺性状差异的候选基因.试验采集440头猪样本(代表太湖流域地方猪最全面血统)进行基因芯片分型,并使用该基因分型数据集进行多种群体遗传学分析,明确太湖流域地方猪品种内部的遗传结构,并鉴定梅山猪亚群间、以及二花脸和米猪群体间体重体尺性状差异的候选SNP位点和候选基因.结果 显示:在太湖流域地方猪种内部,二花脸猪与米猪间的亲缘关系最接近,其遗传距离小于梅山猪两个亚群间的遗传距离,并且拥有最为一致的进化路线.太湖流域地方猪各品种及梅山猪品种内两个亚群间都达到高度分化水平,Fst值均大于0.25,ADMIXTURE分析表明,包括梅山猪两个亚群在内的8个群体的群体结构不完全一致,在K=8时,各自展现出完全不同的祖先血统组成.通过梅山猪亚群间Fst分析、以及米猪和二花脸猪间Fst分析,在猪1、3和6号等染色体上,共鉴定到24个位点在两个分析中都表现出受选择状态,并在这些位点上下游50 kb范围注释到20个基因,其中有8个基因被报道与体重体尺性状相关.此外,受选择位点形成的选择区域与多个猪体重体尺相关QTLs重叠.试验确定了太湖流域地方猪种内部遗传结构,初步解析了这些猪种体重体尺性状差异的遗传基础,为进一步保护和利用这些种群奠定了良好的理论基础.

Chinese indigenous pig breeds in the Taihu Lake (TL) region of Eastern China are well documented by their exceptional prolificacy. There are seven breeds in this region including Meishan (MS), Erhualian (EHL), Jiaxing Black (JXB), Fengjing (FJ), Shawutou (SWT), Mi (MI), and Hongdenglong (HDL). At present, these breeds are facing a great threat of population decline, inbreeding depression and lineage admixture since Western commercial pigs have dominated in Chinese pig industry. To provide better conservation strategies and identify candidate genes under selection for these breeds, we explored genome-wide single nucleotide polymorphism (SNP) markers to uncover genetic variability and relatedness, population structure, historical admixture and genomic signature of selection of 440 pigs representing the most comprehensive lineages of these breeds in TL region in a context of 1228 pigs from 45 Eurasian breeds. We showed that these breeds were more closely related to each other as compared to other Eurasian breeds, defining one of the main ancestral lineages of Chinese indigenous pigs. These breeds can be divided into two subgroups, one including JXB and FJ, and the other comprising of EHL, MI, HDL, MS, and SWT. In addition, HDL was highly inbred whereas EHL and MS had more abundant genetic diversity owing to their multiple conservation populations. Moreover, we identified a list of candidate genes under selection for body size and prolificacy. Our results would benefit the conservation of these valuable breeds and improve our understanding of the genetic mechanisms of body size and fecundity in pigs.