| With the large-scale and intensive development of the breeding industry,artificial insemination has become a powerful tool in countries where pig production is highly intensive.In recent years,large domestic commercial artificial insemination（AI）stations have been put into operation,and advanced measurement equipment and professional technicians are more systematic and accurate in accumulating semen data.Therefore,phenotypic to molecular studies on more boar populations can be achieved.In this study,a total of 143,814 semen traits of 1179 Landrace and 952 Yorkshire boars were collected from 3 pig artificial insemination centers affiliated to a group in Guangxi,China from 2016 to 2020.The GLM function of R was used to perform the least square method to analyze the station,season,month and semen collection month of age on semen traits of Yorkshire and Landrace boars.Asreml-R software was used to analyze the genetic parameters of semen traits.Farm-CPU method was used for genome-wide association analysis to explore the molecular markers and important candidate genes affecting semen traits in boars.It provides a theoretical basis for revealing the genetic mechanism of semen traits in boars.The results are as following:1.Landrace boars significantly better than Yorkshire boars in terms of Semen volume,Abnormal sperm number,Total sperm count,and Functional sperm number.Yorkshire sperm motility was better than Landrace（p<0.01）.The effect of station on the semen characteristics of Landrace and Yorkshire boars was significantly different（p<0.01）.2.The Semen volume and Total sperm number were the best in autumn,and the sperm motility was the best in winter.The Abnormal sperm number and Functional sperm number were significantly higher in autumn and winter than in spring and summer（p<0.05）.In general,the quality of semen in autumn and winter is better than spring and summer.Months with large temperature changes such as April,August and November have a greater impact on boar semen quality.3.The boar semen collection month of age has a significant effect on semen quality.The Semen volume,Total sperm number,Functional sperm number are better at 31 to 36 months.The Semen density is better at 13 to 18 months.Sperm motility is better at 36 to 42 months of age,and the Abnormal sperm number is best at 26 to 30months of age.All in all,boars aged 1～3 have better performance.4.Descriptive statistics were collected on semen phenotypic traits,and the coefficient of variation of each trait ranged from 10.01%to 87.88%,with the smallest Sperm motility and the largest Abnormal sperm number.The heritability of boar semen traits was estimated using the single-trait repeatability model.The Sperm volume,Sperm motility,and Abnormal sperm number of Landrace and Yorkshire boars were medium heritability,which were 0.213～0.231,0.283～0.286,and0.403～0.491,respectively.The genetic correlation between Semen volume and Semen density was-0.75 and-0.62,respectively.The genetic correlation between Sperm motility and Abnormal sperm number was-0.80 and-0.93,respectively.In conclusion,boar Semen volume,Sperm motility and Abnormal sperm number have good selection potential and can be used as breeding traits.5.Based on the Gene Seek Porcine 50K SNP chip to obtain the individual’s genotype information,use Plink software to quality control the genotype data,and use Beagle5.0 software to fill the missing genotype data.After quality control,257Landrace boars 37838 SNPs and 493 Yorkshire boars 36935 SNPs were used for following analysis.Farm-CPU algorithm was used for GWAS analysis of 6 semen traits of Landrace and Yorkshire boars,and Bonferroni method was used to determine the significance threshold of 1.32×10-6and 1.35×10-6,respectively.Potentially significant threshold of 2.64×10-5and 2.70×10-5.A total of 12 SNP significant sites were found in this study,and 23 potential significant SNP sites were selected.6.Candidate genes are searched in the 1Mb region upstream and downstream of significant SNPs.According to published literature reports,A total of 12 genes from FOXA2,CSTL1,CST11,CST3,CST9L,RSPH1,WNT3,WNT9B,PRDM14,SULF1,SPPL2C and LYZL6 are considered as candidate genes for semen traits in Landrace and Yorkshire boars.Among them,the FOXA2,CSTL1,CST11,CST3,and CST9L genes near the M1GA0021799 locus on the 17th stain can be considered as important candidate genes for the Semen volume,Abnormal sperm number and Total sperm count of Yorkshire boars.This study analyzes the influencing factors of sperm traits of Landrace and Yorkshire boars,which has certain guiding significance for boar production management.It was found that the semen traits were low to medium heritability,moderate repetitive traits,and there were different degrees of genetic correlation,phenotypic correlation and environmental correlation among various traits,which enriched the genetic content of boar semen traits.SNP loci and important candidate genes that affect the significant association of boar semen-related traits were found,which provided a theoretical basis for the molecular marker breeding of Landrace and Yorkshire boars in China. |
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