A snp molecular marker related to pig backfat thickness and application thereof

Abstract

This invention discloses a SNP molecular marker associated with backfat thickness in pigs. This SNP marker is either a T>C mutation located at position 66885632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 version, or a T>C mutation represented by M at position 106 as shown in SEQ ID NO: 1. This molecular marker is significantly associated with the backfat thickness trait in pigs. Using this molecular marker, an efficient and accurate marker-assisted breeding technique can be established and applied to the genetic improvement of backfat thickness in breeding pigs, thereby improving the meat (lean meat) performance of the pig population, increasing enterprise economic profits, and enhancing core competitiveness. By optimizing the dominant allele of this SNP molecular marker, the frequency of the dominant allele can be increased generation by generation, reducing backfat thickness in the core breeding population, accelerating the improvement of related carcass traits in breeding pigs, and thus effectively improving the economic benefits of pig breeding.

Description

Technical Field

[0001] This invention relates to the field of animal genetics and breeding, and in particular to a SNP molecular marker related to backfat thickness in pigs and its application. Background Technology

[0002] In pig production, backfat thickness is a key indicator for evaluating fattening efficiency and fat deposition capacity. Reducing backfat thickness and increasing lean meat percentage are important breeding goals both domestically and internationally. Furthermore, backfat thickness also influences the onset of puberty and reproductive performance in sows; therefore, predicting other traits using backfat thickness is of significant importance. Backfat thickness in pigs is a moderately to highly heritable trait, with a heritability of approximately 0.45, and it is relatively easy to measure. Therefore, significant improvements can be achieved through conventional breeding methods.

[0003] Currently, with the publication of the complete pig genome sequence and the development of high-density microarrays, genome-wide association studies (GWAS) are widely used to identify molecular markers and candidate genes associated with economic traits in pigs. Therefore, GWAS analysis can identify molecular markers related to backfat thickness in pigs, thereby accelerating the genetic improvement of backfat traits and ultimately increasing the economic benefits of pig farms. Summary of the Invention

[0004] The purpose of this invention is to provide an SNP molecular marker related to backfat thickness in pigs and its application, in order to solve the above-mentioned problems.

[0005] According to a first aspect of the present invention, a SNP molecular marker associated with backfat thickness in pigs is provided. This molecular marker is located at a T>C base mutation at a site of 66885632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 version. This molecular marker is significantly associated with the backfat thickness trait in pigs. By using this molecular marker, an efficient and accurate marker-assisted breeding technology can be established and applied to the genetic improvement of backfat thickness in breeding pigs, thereby improving the meat (lean meat) performance of the pig population, increasing the economic profits of enterprises, and enhancing core competitiveness. By optimizing the dominant allele of this SNP molecular marker, the frequency of the dominant allele can be increased generation by generation, reducing the backfat thickness of core breeding pigs, accelerating the improvement of related carcass traits in breeding pigs, and thus effectively improving the economic benefits of breeding pigs.

[0006] In some embodiments, the upstream and downstream gene sequences of the SNP molecular marker site are shown in SEQ ID NO: 1, and the SNP molecular marker is located at the M-represented T>C base mutation at the 106th position shown in SEQ ID NO: 1.

[0007] According to a second aspect of the present invention, an application of an SNP molecular marker in breeding pig breeds with low backfat thickness is provided. This molecular marker is either a T>C mutation located at locus 66885632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 version, or a T>C mutation represented by M at locus 106 as shown in SEQ ID NO: 1. By screening the genotypes of replacement breeding pigs and selecting individuals with TT or TC for propagation, the frequency of allele T in the offspring pig population is increased generation by generation, thereby breeding pig breeds with low backfat thickness. This reduces the backfat thickness of breeding pigs, thereby improving the meat production performance of the offspring pig population, increasing enterprise economic profits, and enhancing core competitiveness.

[0008] In some implementations, the application includes the following steps:

[0009] 1) Detect the T>C mutation at the 66885632bp site on chromosome 5 or the T>C mutation represented by M at the 106th site as shown in SEQ ID NO: 1 in replacement breeding pigs;

[0010] 2) Select breeding pigs with the molecular marker genotype TT or TC from step 1), and cull individuals with the CC genotype;

[0011] 3) Use the individuals selected in step 2) as breeding pigs for breeding. In the offspring, continue to select breeding pigs with the molecular marker genotype TT or TC from step 1) and eliminate individuals with the CC genotype. This will increase the frequency of allele T in the offspring pig population generation by generation, thereby breeding a pig breed with low backfat.

[0012] According to a third aspect of the invention, an application of an SNP molecular marker in screening piglets for the genetic trait of low backfat thickness is provided. This SNP molecular marker is a T>C mutation located at the 66885632 bp site on chromosome 5 of the international pig genome Sscrofa 11.1 version. By screening the genotype of the molecular marker in the piglets to be tested, piglets with the genetic trait of low backfat thickness can be selected for rearing at the piglet stage. This allows for sorting of the pig herd at the piglet stage, and piglets with the TT or TC gene can be raised as replacement gilts, which can efficiently reduce the backfat thickness of the replacement gilt population and achieve better economic value.

[0013] In some implementations, the application includes the following steps:

[0014] 1) Detect the T>C mutation at the 66885632bp site on chromosome 5 or the T>C mutation represented by M at the 106th site as shown in SEQ ID NO: 1 in the piglets to be screened;

[0015] 2) When the genotype of the molecular marker detected in step 1) is TT or TC, the piglet to be screened has the genetic trait of low backfat thickness and should be retained; when the genotype is CC, the piglet to be screened has the genetic trait of high backfat thickness and should be culled.

[0016] According to a fourth aspect of the present invention, a genetic improvement method for reducing backfat thickness in pigs is provided, wherein the method comprises the following steps:

[0017] 1) Detect the T>C mutation at the 66885632bp site on chromosome 5 or the T>C mutation represented by M at the 106th site as shown in SEQ ID NO: 1 in replacement breeding pigs;

[0018] 2) Select breeding pigs with the molecular marker genotype TT or TC from step 1), and cull individuals with the CC genotype;

[0019] 3) Use the individuals selected in step 2) as breeding pigs for breeding. In the offspring, continue to select breeding pigs with the molecular marker genotype TT or TC from step 1) and eliminate individuals with the CC genotype. This will increase the frequency of allele T in the offspring pig population generation by generation, thereby reducing the backfat thickness of the offspring pigs.

[0020] This method can effectively reduce backfat thickness in pigs, increase lean meat percentage, and enhance the market competitiveness and economic value of pig breeds.

[0021] According to a fifth aspect of the invention, a primer pair is provided for detecting a T>C mutation located at position 66885632 bp on chromosome 5 in pigs or a T>C mutation represented by M at position 106 as shown in SEQ ID NO: 1, wherein the nucleotide sequence of the primer pair is as follows:

[0022] P001-F: 5'-CGCAGGCACAGAGAAGCACAAG-3',

[0023] P002-R: 5'-CCATCATCTCGCTTGCAGGAATCC-3'.

[0024] This primer pair enables efficient detection of SNP molecular markers related to backfat thickness in pigs, allowing for the establishment of efficient and accurate marker-assisted breeding technology. This facilitates rapid and accurate selective breeding to improve the backfat thickness of breeding pigs, thus accelerating breeding progress.

[0025] According to a sixth aspect of the present invention, a kit is provided for detecting SNP molecular markers of T>C mutations located at locus 66885632 bp on chromosome 5 in pigs or T>C mutations represented by M at locus 106 as shown in SEQ ID NO: 1, wherein the kit contains the following primer pair:

[0026] P001-F: 5'-CGCAGGCACAGAGAAGCACAAG-3',

[0027] P002-R: 5'-CCATCATCTCGCTTGCAGGAATCC-3'.

[0028] This kit can efficiently detect SNP molecular markers related to backfat thickness in pigs, enabling the establishment of efficient and accurate molecular marker-assisted breeding technology. It can also quickly and accurately improve the breeding of pigs with low backfat thickness through selective breeding, thus accelerating breeding progress.

[0029] According to a seventh aspect of the present invention, an application of a primer pair in identifying the backfat thickness trait in pigs is provided, wherein the application comprises the following steps:

[0030] 1) PCR was performed on the pigs to be tested using a primer pair, and then the PCR products were used for genotyping. The primer pair was:

[0031] P001-F: 5'-CGCAGGCACAGAGAAGCACAAG-3',

[0032] P002-R: 5'-CCATCATCTCGCTTGCAGGAATCC-3';

[0033] 2) When the genotype detected in step 1) is TT or TC, the pig to be tested has the hereditary trait of low backfat thickness; when the genotype detected is CC, the pig to be tested has the hereditary trait of high backfat thickness.

[0034] This primer pair can efficiently detect SNP molecular markers related to backfat thickness in pigs, enabling the establishment of efficient and accurate molecular marker-assisted breeding technology. This allows for rapid and accurate selection and improvement of breeding pigs with low backfat thickness, thus accelerating breeding progress.

[0035] According to an eighth aspect of the present invention, an application is provided of a molecular marker, a primer pair for detecting the molecular marker, or a kit containing the primer pair in screening for backfat thickness in pigs, identifying backfat thickness in pigs, breeding pigs with low backfat thickness, reducing backfat thickness in pigs, and genetically improving meat quality traits in pigs. Thus, by using this SNP molecular marker, the primer pair for detecting the molecular marker, or a kit containing the primer pair, a highly efficient and accurate marker-assisted breeding technology can be established, enabling rapid and accurate selective breeding to improve low backfat thickness in breeding pigs, thereby accelerating breeding progress.

[0036] Beneficial effects of this invention:

[0037] 1. A novel SNP molecular marker associated with backfat thickness in pigs is disclosed. This SNP molecular marker is either a T>C mutation located at position 66885632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 or a T>C mutation represented by M at position 106 as shown in SEQ ID NO: 1. This molecular marker is significantly associated with the backfat thickness trait in pigs. By using this molecular marker, an efficient and accurate marker-assisted breeding technology can be established and applied to the genetic improvement of backfat thickness in breeding pigs, thereby improving the meat (lean meat) performance of the pig population, increasing the economic profit of enterprises, and enhancing core competitiveness. By optimizing the dominant allele of this SNP molecular marker, the frequency of the dominant allele can be increased generation by generation, reducing the backfat thickness of core breeding pigs, accelerating the improvement of related carcass traits in breeding pigs, and thus effectively improving the economic benefits of breeding pigs.

[0038] 2. The application of this SNP molecular marker in breeding pig breeds with low backfat thickness was disclosed. By screening the genotypes of replacement breeding pigs and selecting TT or TC individuals for propagation, the frequency of the allele T in the offspring pig population is increased generation by generation, thereby breeding pig breeds with low backfat thickness. This reduces the backfat thickness of breeding pigs, thereby improving the meat production performance of the offspring pig population, increasing enterprise economic profits, and enhancing core competitiveness.

[0039] 3. The application of this SNP molecular marker in screening piglets with the genetic trait of low backfat thickness was disclosed. By screening the genotype of the molecular marker in the piglets to be tested, piglets with the genetic trait of low backfat thickness can be selected for rearing at the piglet stage. This allows for sorting of the pig herd at the piglet stage, and piglets with the TT or TC gene can be raised as replacement pigs, which can effectively reduce the backfat thickness of the replacement pig population and achieve better economic value.

[0040] 4. A genetic improvement method for reducing backfat thickness in pigs is disclosed. This method can effectively reduce the backfat thickness trait in pigs, increase the lean meat percentage of the carcass, and improve the market competitiveness and market economic value of the pig breed.

[0041] 5. A primer pair for detecting SNP molecular markers related to backfat thickness in pigs is disclosed. This primer pair can efficiently detect SNP molecular markers related to backfat thickness in pigs, establish an efficient and accurate molecular marker-assisted breeding technology, and quickly and accurately improve the breeding of pigs with low backfat thickness through selective breeding, thereby accelerating the breeding progress.

[0042] 6. A kit for detecting SNP molecular markers related to backfat thickness in pigs is disclosed. This kit can efficiently detect SNP molecular markers related to backfat thickness in pigs, establish an efficient and accurate molecular marker-assisted breeding technology, and quickly and accurately improve the breeding of pigs with low backfat thickness through selective breeding, thereby accelerating the breeding progress.

[0043] 7. The application of primer pairs for detecting SNP molecular markers related to backfat thickness in pigs is disclosed. These primer pairs can efficiently detect SNP molecular markers related to backfat thickness in pigs, enabling the establishment of efficient and accurate molecular marker-assisted breeding technology. This allows for rapid and accurate selection and improvement of low backfat thickness in breeding pigs, thus accelerating breeding progress.

[0044] 8. The application of SNP molecular markers related to backfat thickness in pigs, or primer pairs for detecting these molecular markers, or kits containing these primer pairs, in screening for backfat thickness traits in pigs, identifying backfat thickness traits in pigs, breeding pigs with low backfat thickness traits, reducing backfat thickness traits in pigs, and genetically improving meat quality traits in pigs is disclosed. Using these SNP molecular markers, or primer pairs for detecting these molecular markers, or kits containing these primer pairs, an efficient and accurate marker-assisted breeding technology can be established, enabling rapid and accurate selective breeding to improve low backfat thickness in breeding pigs and accelerating breeding progress. Attached Figure Description

[0045] Figure 1 A GWAS Manhattan plot representing the genome-wide association analysis of backfat thickness on chromosome 5 in Large White, Landrace, and Duroc pigs; where: the horizontal axis represents the chromosome position of the pig; and the vertical axis represents the -logP value. Detailed Implementation

[0046] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0047] Example 1

[0048] (1) Laboratory animals

[0049] The experimental pig population used in this invention consists of 1,131 purebred Large White, Landrace, and Duroc pigs from Guangdong Guangken Livestock Group Co., Ltd., which is the company's core population.

[0050] This experiment selected Large White, Landrace, and Duroc pigs from this resource population. The pigs had free access to feed and water, and the feeding methods and rearing conditions remained consistent throughout the experiment, which was a conventional approach.

[0051] (2) Sample collection

[0052] Collect the above-mentioned piglet tail or ear tissues, soak them in a 75% ethanol solution, and store them in a -20°C refrigerator for later use.

[0053] (3) Pig genome 50k SNP chip genotyping

[0054] Ear or tail tissues were collected from each of the 1131 Large White, Landrace, and Duroc pigs in the aforementioned resource population. Whole-genome DNA was extracted using the standard phenol-chloroform method. The concentration and OD ratio (OD260 / 280, OD260 / 230) of each sample were accurately determined using a NanoDrop 2000 / 2000C nucleic acid and protein analyzer. DNA samples that passed the NanoDrop 2000 / 2000C nucleic acid and protein analyzer were diluted to approximately 50 ng / μL. 6 μL of the extracted DNA sample was then mixed with 2 μL of loading buffer and loaded onto a 1% (w / v) agarose gel. Electrophoresis was performed at 150 V for 25 min. The DNA integrity was observed and photographed using a UV spectrophotometer and gel imaging device.

[0055] DNA samples were sent to Beijing Compson Biotechnology Co., Ltd. for genotyping using a 50kSNP microarray (Zhongxin No. 1 breeding chip, Beijing Compson Biotechnology Co., Ltd.). Following strict quality control standards, individuals with a detection rate below 90%, a family Mendelian error rate above 0.1, a minimum allele frequency below 0.05, and a Hardy-Weinberg equilibrium significance level above 10 were excluded. -6 The SNPs were analyzed, and finally, 24,435 valid genotype data for SNPs were obtained.

[0056] (4) Genome-wide association analysis (GWAS)

[0057] To eliminate population stratification effects, this invention uses GCTA software to calculate principal component characteristics of all individuals based on whole-genome sequence information, and uses the first five principal components as covariates to correct for the influence of potential population stratification on the results. This invention uses a linear mixture model in GEMMA software for GWAS analysis of the backfat thickness trait. The Bonferrini method is used to determine the significance threshold of the association between SNPs and the backfat thickness trait. The genomic significance threshold is 0.05 divided by the number of effective SNP loci, i.e., the genomic significance threshold is 2.05E-06, or 0.05 / 24435 (number of effective SNPs); the chromosomal significance threshold is 1 divided by the number of effective SNP loci, i.e., the chromosomal significance threshold is 4.09E-05, or 1 / 24435 (number of effective SNPs).

[0058] GWAS analysis results are as follows Figure 1 As shown. From Figure 1 It was found that a site significantly affecting backfat thickness exists on chromosome 5 of Large White, Landrace, and Duroc pigs (this site is located at 66885632 bp on chromosome 5 of the international pig genome Sscrofa 11.1, representing a T>C mutation). The gene sequences upstream and downstream of this significantly associated SNP site are shown in SEQ ID No:1. The SNP site is located at position 106 of the sequence shown in SEQ ID No:1, where M represents a T>C mutation. This molecular marker can be abbreviated as g.106T>C (P value 3.58e-07) mutation in this paper. The gene sequences upstream and downstream of this SNP are shown in SEQ ID No:1.

[0059]

[0060] Note: M marked in the sequence listing is the mutation site. M site is a T>C mutation, which is displayed in bold font (the mutated base in parentheses is the allele mutation). The positions of the designed primer sequences are indicated by underscores and italics at the beginning and end of the sequence.

[0061] (5) Association analysis between different genotypes and backfat phenotype

[0062] Table 1 shows that the molecular marker g.106T>C is highly significantly correlated with backfat thickness (P<0.001), indicating that this molecular marker significantly affects backfat thickness in pigs. Selection at this SNP locus can reduce backfat thickness in the pig population, thereby accelerating the breeding process. Furthermore, Table 1 shows that individuals with the TT genotype have lower backfat thickness than those with the CT and CC genotypes, and the two traits exhibit synergistic changes. The phenotypic mean of TT individuals is 0.53 and 2.06 lower than that of CT and CC individuals, respectively. Additionally, the ANOVA results for the two phenotypes show highly significant differences in the distribution of the three genotypes in the backfat thickness phenotype (P<0.01). Therefore, gradually retaining the TT genotype in breeding pigs to increase the frequency of the T allele at this locus through successive generations can significantly reduce backfat thickness in breeding pigs, bringing greater economic benefits to pig farms.

[0063] Table 1. Statistical analysis of the mutation site at chromosome 5, position 66885632, and backfat thickness trait.

[0064]

[0065]

[0066] Note: *** indicates a highly significant difference.

[0067] Example 2: Target DNA Sequence Amplification and Sequencing

[0068] (1) Primer design

[0069] The DNA sequence of pig chromosome 5, such as SEQ ID NO:1, was downloaded from the Ensembl website (http: / / asia.ensembl.org / index.html), and primers were designed using the primer design software Oligo 7. The DNA sequences of the designed primers are shown below:

[0070] P001-F: 5'-CGCAGGCACAGAGAAGCACAAG-3' (SEQ IDNO: 2),

[0071] P002-R: 5'-CCATCATCTCGCTTGCAGGAATCC-3' (SEQ IDNO: 3);

[0072] (2) PCR amplification

[0073] To a 10 μL reaction mixture, add 1 μL of DNA template, 3.4 μL of double-distilled water, 5 μL of 2×Tag PCR StanMix with Loading Dye, and 0.3 μL each of primers P001-F and P002-R. The PCR reaction conditions were: 94℃ pre-denaturation for 5 min, followed by 35 cycles of 94℃ denaturation for 30 s, 57.6℃ annealing for 30 s, and 72℃ extension for 45 s, with a final extension at 72℃ for 5 min.

[0074] (3) DNA sequencing

[0075] DNA sequence sequencing and identification: Performed at BGI Genomics Co., Ltd. in Shenzhen, the gene fragments were sequenced using both forward and reverse reactions. The obtained sequences were compared with the NCBI genome sequence to identify mutations at corresponding SNP sites. The sequencing results were consistent with the SEQ ID NO:1 sequence.

[0076] Example 3: Analysis of the effect of molecular marker g.106T>C

[0077] Table 1 shows that the dominant allele TT (g.106T>C) reduces backfat thickness by 2.06 mm compared to the inferior allele CC. Therefore, by using marker-assisted selection or genomic selection to gradually retain TT-type pigs within a population, the frequency of the dominant T allele can be significantly increased, thus contributing to a reduction in backfat thickness in breeding pigs, accelerating the breeding improvement process, and ultimately effectively improving the economic benefits of pig breeding.

[0078] Example 4: Application of the molecular marker g.106T>C in breeding pig breeds with low backfat and thick backfat

[0079] 1) Detect the molecular marker g.106T>C genotype in replacement breeding pigs;

[0080] 2) Select breeding pigs with the molecular marker genotype TT or TC from step 1), and cull individuals with the CC genotype;

[0081] 3) Use the individuals selected in step 2) as breeding pigs for breeding. In the offspring, continue to select breeding pigs with the molecular marker genotype TT or TC from step 1) and eliminate individuals with the CC genotype. This will increase the frequency of allele T in the offspring pig population generation by generation, thereby breeding a pig breed with low backfat.

[0082] Example 5: Application of the molecular marker g.106T>C in screening piglets for the genetic trait of low backfat thickness.

[0083] 1) Detection of the molecular marker g.106T>C in the pigs to be screened;

[0084] 2) When the genotype of the molecular marker detected in step 1) is TT or TC, the pig to be screened has the genetic trait of low backfat thickness and should be retained; when the genotype is CC, the pig to be screened has the genetic trait of high backfat thickness and should be culled.

[0085] Example 6: A genetic improvement method for reducing backfat thickness in pigs

[0086] 1) Detect the molecular marker g.106T>C in replacement breeding pigs;

[0087] 2) Select breeding pigs with the molecular marker genotype TT or TC from step 1), and cull individuals with the CC genotype;

[0088] 3) Use the individuals selected in step 2) as breeding pigs for breeding. In the offspring, continue to select breeding pigs with the molecular marker genotype TT or TC from step 1) and eliminate individuals with the CC genotype. This will increase the frequency of allele T in the offspring pig population generation by generation, thereby reducing the backfat thickness of the offspring pigs.

[0089] Example 7: Application of primer pairs for detecting the molecular marker g.106T>C in identifying the backfat thickness trait in pigs.

[0090] 1) PCR was performed on the pigs to be tested using primer pairs with the sequences shown in SEQ ID NO:2 / SEQ ID NO:3, and then the PCR products were used for genotyping.

[0091] 2) When the genotype detected in step 1) is TT or TC, the pig to be tested has the hereditary trait of low backfat thickness; when the genotype detected is CC, the pig to be tested has the hereditary trait of high backfat thickness.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. The application of products containing SNP molecular markers in the breeding of low-backfat, thick-fat pig breeds, among which, The SNP molecular marker has an SNP site located at 66,885,632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 version, with a base polymorphism of T or C. The pig breed is a purebred Large White, Landrace, or Duroc pig. The application includes the following steps: 1) Detect the SNP molecular markers mentioned above in replacement breeding pigs; 2) Select breeding pigs with the SNP molecular marker genotype TT or TC from step 1), and cull individuals with the CC genotype; 3) Use the individuals selected in step 2) as breeding pigs for breeding. In the offspring, continue to select breeding pigs with the SNP molecular marker genotype TT or TC in step 1) and eliminate individuals with the CC genotype. This will increase the frequency of allele T in the offspring pig population generation by generation, thereby breeding a pig breed with low backfat.

2. Application of products containing SNP molecular markers in screening piglets for the genetic trait of low backfat thickness, among which, The SNP molecular marker has an SNP site located at 66,885,632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 version, with a base polymorphism of T or C. The pig breed is a purebred Large White, Landrace, or Duroc pig. The application includes the following steps: 1) Detect the SNP molecular markers described above in the piglets to be screened; 2) When the genotype of the SNP molecular marker detected in step 1) is TT or TC, the piglet to be screened has the genetic trait of low backfat thickness and should be retained; when the genotype is CC, the piglet to be screened has the genetic trait of high backfat thickness and should be culled.

3. A genetic improvement method for reducing backfat thickness in pigs, wherein, The pig breed is a purebred Large White, Landrace, or Duroc pig, and the method includes the following steps: 1) Detect SNP molecular markers in replacement breeding pigs. The SNP sites of the SNP molecular markers are located at 66885632 bp on chromosome 5 of the international pig genome Sscrofa 11.1 version, and the base polymorphism is T or C. 2) Select breeding pigs with the SNP molecular marker genotype TT or TC from step 1), and cull individuals with the CC genotype; 3) Use the individuals selected in step 2) as breeding pigs for breeding. In the offspring, continue to select breeding pigs with the SNP molecular marker genotype TT or TC in step 1) and eliminate individuals with the CC genotype. This is to increase the frequency of allele T in the offspring pig population generation by generation, thereby reducing the backfat thickness of the offspring pigs.

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