| Pig artificial insemination has become the main mating method for large-scale pig farms,which plays an important role in saving costs and accelerating genetic improvement.One of the key factors to the application of pig artificial insemination is that boars produce high quality boar semen.Therefore,the study of the genetic architecture of boar semen traits is conducive to a comprehensive understanding of the genetic characteristics of semen traits for the selection of boars with high quality semen.In this study,the computer-assisted sperm analysis system was used to evaluate semen volume,sperm concentration,sperm motility,abnormal sperm number,and total sperm number of Duroc boars,to ensure the accuracy of the data.First,the genetic parameters of boar semen traits were estimated,and then using genome-wide association analysis to search the molecular markers and important candidate genes that affecting the semen traits of boars.In order to better understand the genetic mechanism of boar semen traits.The results are as following:?1?Phenotypic data consisted of 105,201 ejaculates of 2,022 Duroc boars,including the semen volume,sperm concentration,sperm motility,abnormal sperm number and,total sperm number.The mean and standard deviation of these traits were 162.51±63.53mL,4.71±2.20×108/mL,88.62±7.11%,11.96±8.36%and,721.92±339.26×108,respectively.?2?The 105,201 ejaculates originated from 2,022 boars of the Duroc.Genetic parameters of semen traits were estimated by multiple-trait analysis using a animal model.The heritability of semen volume,sperm concentration,sperm motility,abnormal sperm and total sperm number were 0.22,0.20,0.14,0.25,and 0.10,respectively.The repeatability of semen traits were 0.40,0.37,0.25,0.39,and 0.26,respectively.The low heritability indicates that it is hard to improve semen traits by selection,but semen traits still have possible for genetic improvement through selection.There were strong negative genetic correlations between semen volume and sperm concentration and between sperm motility and abnormal sperm,which were-0.65 and-0.69,respectively.Moderate positive genetic correlations were found between sperm concentration and sperm motility?0.45?and between sperm concentration and total sperm number?0.40?.The genetic correlation between semen volume and total sperm number were 0.40.The genetic correlations about remaining traits were low.The phenotype of total sperm number was positively moderate correlated with semen volume?0.47?and sperm concentration?0.60?.The phenotype correlations for remaining traits were low.?3?The GeneSeek Porcine 50K SNP chip was used to obtain the genotype information.Missing genotype data were fully imputed by Beagle software.Data quality control was carried out using PLINK software before and after imputation.After quality control,1,440 individuals and 35,813 SNPs were used for following analysis.?4?A genome-wide association analysis was performed on semen volume,sperm concentration,sperm motility,abnormal sperm number and,total sperm number of 1440 Duroc boars by utilizing the FarmCPU algorithm.The significance threshold was determined using the Bonferroni method to be 1.40×10-6.A total of 23 SNPs had reached a significant threshold level.The SNP ALGA0001958 on chromosome 1 significantly associated with both sperm motility and total sperm number.?5?About 1Mb upstream and downstream of these significant SNPs,FGF10,PSPH1,MAP7,MTFR2,FKBP6,CNR1,UBE2J1,NME5,LHX9,GATA4,SPAG4 and,CNBD2 were found to be important candidate genes which according to the results reported in the published literature.The MAP7 near the SNP ALGA0001958 on chromosome 1 can be considered as an important candidate gene that affects both sperm motility and total sperm count.In this study,we found that the heritability of semen traits of Duroc boars was low or moderate,and there were different levels of genetic correlation among the traits.It was suggested that genetic improvement of semen traits of Duroc boars can be made through a reasonable selection.In addition,significant SNPs associated with semen traits and important candidate genes that influence semen traits were found.It provides a new molecular marker for genetic improvement of semen traits of Duroc boars and increases genetic research of boar semen traits. |
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