| Boar reproductive traits are economically important for the pig industry. However, these traits are quantitative complex ones with low heritabilities, and are greatly influenced by environmental factors. Thus, it is difficult to perform direct selection for these traits. In recent years, with the development of molecular biology, a number of researchers started to identify the genetic mechanisms controlling boar reproductive traits by molecular assays for identification of causative genes. These studies not only provide molecular basis for boar genetic improvement but also offer valuable references for man reproductive failure.We previously constructed a White Duroc × Erhualian resource population. Two hundred and five F2 boars were recorded for several reproductive traits including semen volume(SV), sperm concentration(SC), total sperm per ejaculate(TSE), sperm motility(SM), testis weight(TW), epididymal weight(EW) and serum testosterone concentration(STC), etc. In addition, our formerly imputation-based GWS(genome-wide association) study identified QTL affecting boar SC and TSE on SSC7, and the same peak SNP(INRA0026647) was found for these two traits.In this study, we collected phenotypic data of SV, SC, TSE and SM of totally 356 Duroc, Landrace and Large White commercial boars. TEP1, PARP2 and CCNB1IP1 harboring or approaching INRA0026647 were chosen as positional candidate genes, and the association between the polymorphisms of these three genes and reproductive traits of F2/commercial boars was investigated.In F2 population, association analyses revealed that TEP1, PARP2 and CCNB1IP1 genes had 9, 11 and 10 SNPs significantly associated with boar reproductive traits(P<0.05 or P<0.01), respectively. For TEP1 gene, TEP1 –g.654 C>A showed the strongest association with SC(P=6.56E-8), and was also significantly associated with SV, TSE and SM(P<0.05). In PARP2 gene, PARP2 g.107 A>G(5 SNPs are complete linkage with it) displayed the most significant association with SC(P=4.82E-06), and was also significantly associated with SM and TSE(P<0.05). PARP2 g.10568 A>G was significantly associated with left and right EW(the P value was 8.92E-04 and 6.14E-04, respectively). For CCNB1IP1 gene, CCNB1IP1 g.14 C>A(5 SNPs are complete linkage with it) displayed the strongest association with SC(P=1.11E-06), and was also significantly associated with SV, TSE and STC(P<0.05). Haplotype analyses revealed that 3 haplotypes of TEP1 were significantly associated with SV, SC and SM(P<0.05 or P<0.01); 5 haplotypes of PARP2 showed significant association with SC, SV, EW and STC(P<0.05 or P<0.01); 2 haplotypes of CCNB1IP1 displayed significant association with SC(P<0.05).Partly selected significant SNPs in F2 population were all displayed low minor allele frequencies in commercial boar populations. No significant association was found between these SNPs and reproductive traits of commercial boars(P>0.05). This may be due to small sample size, inconsistent genetic background of commercial populations and different management for these boars.q RT-PCR showed that the three genes were expressed in all selected 14 tissues, and TEP1 and PARP2 genes displayed relatively higher expression level in testis.This study provides valuable reference for identification of causative genes or exploiting molecular markers for boar reproductive traits. |
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