A molecular marker related to carnosine content in duck meat and its application

Abstract

The present invention discloses a molecular marker related to the content of carnosine in duck meat and its application. The present invention relates to a molecular marker-assisted selection technology in the field of animal genetic breeding technology, and in particular to a molecular marker related to the content of carnosine in duck meat and its application. By detecting the polymorphism or genotype of two SNPs, SNP1 and SNP2, it is found that SNP1 is a site on duck chromosome 2, its nucleotide type is T or C, and it is the 511th nucleotide of sequence 1 in the sequence list, and the SNP2 site is a site on duck chromosome 7, its nucleotide type is T or C, and it is the 74th nucleotide of sequence 4 in the sequence list. When breeding duck breeds with high carnosine content in breast muscle, it is best to select ducks with SNP1 genotype of TT and SNP2 genotype of TT as parents for breeding. The present invention can be used to assist in identifying the content of carnosine in duck meat and perform early screening and auxiliary breeding of duck breeds.

Description

Technical Field

[0001] The present invention relates to a molecular marker-assisted selection technology in the technical field of animal genetic breeding, and in particular to a molecular marker related to the carnosine content in duck meat and an application thereof. Background Art

[0002] With the improvement of living standards, people's demand for meat products is no longer limited to quantity. They also have higher and higher requirements for the nutritional and health benefits of meat quality. Meat products contain some metabolites that are highly related to maintaining health functions, such as carnosine.

[0003] Carnosine is a functional dipeptide synthesized from L-histidine and β-alanine by carnosine synthetase, primarily found in skeletal muscle and the brain. As an endogenous functional substance, carnosine exhibits antioxidant, anti-aging, anti-fatigue, muscle buffering, and pH-stabilizing properties. As an over-the-counter dietary supplement, it holds great promise in the prevention and adjunctive treatment of chronic conditions such as type 2 diabetes, cardiovascular disease, and neurodegeneration.

[0004] Traditional breeding methods have been ineffective in selecting for increased carnosine content in duck meat, so there is still significant room for improvement. Molecular marker-assisted breeding, a recently developed breeding technology, has been widely used in the development of new animal and plant varieties. Genome-wide association analysis can identify molecular markers closely associated with target traits. Using these markers for early selection can significantly reduce breeding costs and accelerate genetic progress. However, there are currently no molecular markers associated with increased carnosine content in duck meat, significantly hindering the development of the meat duck industry. Summary of the Invention

[0005] The problem to be solved by the present invention is how to perform high-throughput identification or auxiliary identification of the carnosine content in duck meat.

[0006] In order to solve the above technical problems, the present invention first provides the use of a substance for detecting the polymorphism or genotype of two SNPs, SNP1 and / or SNP2, in the duck genome.

[0007] The use of the material for detecting the polymorphism or genotype of the two SNPs SNP1 and / or SNP2 in the duck genome provided by the present invention in any of the following:

[0008] (1) Identify or assist in identifying the content of carnosine in duck meat;

[0009] (2) Screening or breeding duck breeds with high carnosine content in duck meat;

[0010] (3) duck breeding;

[0011] (4) preparing products for identifying or assisting in identifying the content of carnosine in duck meat;

[0012] (5) preparing products by screening or breeding duck breeds with high carnosine content in duck meat;

[0013] (6) preparing duck breeding products;

[0014] The SNP1 is a site on duck chromosome 2, the nucleotide type of which is T or C, and is the 511th nucleotide of sequence 1 in the sequence list.

[0015] The SNP2 is a site on duck chromosome 7, the nucleotide type of which is T or C, and is the 74th nucleotide of sequence 4 in the sequence list.

[0016] The present invention also provides a method for identifying or assisting in identifying the content of carnosine in duck meat, comprising detecting the genotypes of the two SNPs, SNP1 and SNP2, described above, in the genome of the duck to be tested, and identifying or assisting in identifying the content of carnosine in the duck meat based on the genotypes of the two SNPs in the duck to be tested:

[0017] The SNP1 is a site on duck chromosome 2, the nucleotide type of which is T or C, and is the 511th nucleotide of sequence 1 in the sequence list; the genotype is TT, TC or CC, the TT is the homozygous type of the SNP1 being T, the CC is the homozygous type of the SNP1 being C, and the TC is the heterozygous type of the SNP1 being T and C;

[0018] The SNP2 is a site on duck chromosome 7, the nucleotide type of which is T or C, and is the 74th nucleotide of sequence 4 in the sequence list; the genotype is TT, TC or CC, the TT is the homozygous type of the SNP2 being T, the CC is the homozygous type of the SNP site being C, and the TC is the heterozygous type of the SNP2 being T and C;

[0019] The method for identifying or assisting in identifying the content of carnosine in duck meat is specifically method M, method N or method Q:

[0020] The method M may be as follows:

[0021] 1) The duck to be tested whose SNP1 genotype is TT is or is a candidate for a breed with a high carnosine content in duck meat;

[0022] 2) The duck to be tested whose SNP1 genotype is CC or TC is or is a candidate for a breed with low carnosine content in duck meat;

[0023] 3) The carnosine content in the duck meat of the duck to be tested whose genotype of the SNP1 is TT is higher than that of the duck to be tested whose genotype of the SNP1 is CC or TC, and the carnosine content in the duck meat of the duck to be tested whose genotype of the SNP1 is TC is higher than that of the duck to be tested whose genotype of the SNP1 is CC;

[0024] The method N may be as follows:

[0025] 1) The duck to be tested whose SNP2 genotype is TT is or is a candidate for a breed with a high carnosine content in duck meat;

[0026] 2) The duck to be tested whose SNP2 genotype is CC or TC is or is a candidate for a breed with low carnosine content in duck meat;

[0027] 3) the carnosine content in the duck meat of the duck to be tested whose genotype of the SNP2 is TT is higher than that of the duck to be tested whose genotype of the SNP2 is CC or TC, and the carnosine content in the duck meat of the duck to be tested whose genotype of the SNP2 is TC is higher than that of the duck to be tested whose genotype of the SNP2 is CC;

[0028] The method Q may be as follows:

[0029] 1) The duck to be tested whose SNP1 genotype is TT and whose SNP2 genotype is TT is or is a candidate for a breed with a high carnosine content in duck meat;

[0030] 2) the duck to be tested whose SNP1 genotype is TC genotype or CC genotype, or / and the duck to be tested whose SNP2 genotype is TC genotype or CC genotype is or is a candidate for a breed with low carnosine content in duck meat;

[0031] 3) The carnosine content of the duck to be tested whose SNP1 genotype is TT and whose SNP2 genotype is TT is higher than that of the duck to be tested whose SNP1 genotype is TC genotype or CC genotype, and / or whose SNP2 genotype is TC genotype and CC genotype.

[0032] Herein, the duck to be tested can be a duck breed, or a hybrid offspring of two duck breeds, such as a hybrid offspring of a Beijing duck and a Liancheng white duck.

[0033] The Beijing duck is the female parent, and the Liancheng white duck is the male parent.

[0034] In the above applications, the substance may be a reagent and / or instrument required for determining the polymorphism or genotype of the SNP site by at least one of the following methods: DNA sequencing, restriction fragment length polymorphism, single-strand conformation polymorphism, denaturing high-performance liquid chromatography, and SNP chip. Among them, SNP chips include chips based on nucleic acid hybridization reactions, chips based on single-base extension reactions, chips based on allele-specific primer extension reactions, chips based on "one-step" reactions, chips based on primer ligation reactions, chips based on restriction endonuclease reactions, chips based on protein-DNA binding reactions, and chips based on fluorescent molecule DNA binding reactions.

[0035] The present invention also provides application of the method for identifying or assisting in identifying the content of carnosine in duck meat in duck breeding.

[0036] The present invention also provides a method for duck breeding, which includes detecting the genotype of the SNP site described above in the duck genome, selecting ducks whose SNP1 genotype is TT and whose SNP2 genotype is TT as parents for breeding, wherein in the ducks whose SNP1 genotype is TT, the TT is a homozygous type of the SNP1 being T, and in the ducks whose SNP2 genotype is TT, the TT is a homozygous type of the SNP2 being T. The breeding purpose of the method includes breeding ducks with a high carnosine content in duck meat.

[0037] As an implementation method, the duck breeding method may include the following steps:

[0038] (1) Using the genomic DNA of the duck to be tested as a template, PCR amplification was performed using a primer set;

[0039] (2) After completing step (1), sequencing is performed to determine the genotypes of the aforementioned SNP1 and SNP2 of the duck to be tested;

[0040] (3) Select ducks with the genotype of SNP1 as described above being TT and ducks with the genotype of SNP2 as described above being TT as parents for breeding.

[0041] In the above application or method, the duck breeding is to cultivate a duck breed with a high carnosine content in duck meat.

[0042] The present invention provides a product, which is a product containing the substance for detecting the polymorphism or genotype of the two SNPs SNP1 and SNP2 in the duck genome as described above, and can be any of the following:

[0043] G1) Products for detecting single nucleotide polymorphisms or genotypes related to carnosine content in duck meat;

[0044] G2) Products that identify or assist in identifying the content of carnosine in duck meat;

[0045] G3) Products for duck breeding.

[0046] G4) Products of screening or breeding duck breeds for carnosine content in duck meat;

[0047] G5) Prepare products for screening or breeding duck breeds with high carnosine content in duck meat.

[0048] In the above applications or products, the substance may be the following D1), D2) or D3):

[0049] D1) the substance is a primer composition for amplifying a duck genomic DNA fragment including the SNP1 and SNP2;

[0050] D2) the substance is a PCR reagent containing the primer combination described in D1);

[0051] D3) The substance is a kit containing the primer composition described in D1) or the PCR reagent described in D2).

[0052] In the above application or product, the primer composition comprises primer set 1 and primer set 2, wherein primer set 1 comprises F1 and R1, and primer set 2 comprises F2 and R2:

[0053] The F1 is as follows (a1) or (a2):

[0054] (a1) DNA molecule shown in sequence 2;

[0055] (a2) a DNA molecule having the same function as sequence 2 after one or more nucleotides are substituted in sequence 2;

[0056] The R1 is as follows (b1) or (b2):

[0057] (b1) DNA molecule shown in Sequence 3;

[0058] (b2) a DNA molecule having the same function as sequence 3 after one or more nucleotides are substituted in sequence 3;

[0059] The F2 is as follows (c1) or (c2):

[0060] (c1) DNA molecule shown in Sequence No. 5;

[0061] (c2) a DNA molecule having the same function as sequence 5 after one or more nucleotides are substituted in sequence 5;

[0062] The R2 is as follows (d1) or (d2):

[0063] (d1) DNA molecule shown in Sequence No. 6;

[0064] (d2) A DNA molecule in which sequence 6 is replaced by one or several nucleotides and has the same function as sequence 6.

[0065] In the above-mentioned applications, methods and products, the primer composition may be labeled or not labeled with a marker. The marker refers to any atom or molecule that can be used to provide a detectable effect and can be attached to a nucleic acid. Markers include but are not limited to dyes; radioactive labels, such as 32P; binding moieties, such as biotin; haptens, such as digoxigenin (DIG); luminescent, phosphorescent or fluorescent moieties; and fluorescent dyes alone or in combination with moieties that can inhibit or shift the emission spectrum by fluorescence resonance energy transfer (FRET). The marker can provide a signal that can be detected by fluorescence, radioactivity, colorimetry, weight determination, X-ray diffraction or absorption, magnetism, enzyme activity, etc. The marker can be a charged moiety (positive or negative charge) or alternatively, it can be charge neutral. The marker can include a nucleic acid or protein sequence or a combination thereof, as long as the sequence comprising the marker is detectable. In some embodiments, the nucleic acid is directly detected (e.g., directly reading the sequence) without a marker.

[0066] The present invention also provides a DNA molecule, the nucleotide sequence of which is Sequence 1 and / or Sequence 4 in the sequence list.

[0067] The present invention also provides the use of the above DNA molecule in any of the following:

[0068] (1) Identify or assist in identifying the content of carnosine in duck meat;

[0069] (2) Screening or breeding duck breeds with high carnosine content in duck meat;

[0070] (3) duck breeding;

[0071] (4) preparing products for identifying or assisting in identifying the content of carnosine in duck meat;

[0072] (5) preparing products by screening or breeding duck breeds with high carnosine content in duck meat;

[0073] (6) Prepare duck breeding products.

[0074] The present invention discloses a molecular marker associated with the carnosine content in duck meat and its application, belonging to the molecular marker-assisted selection technology in the field of animal genetic breeding technology. The molecular marker described in the present invention was obtained through genome-wide association study (GWAS) analysis. A single nucleotide base mutation (C>T) at bp 42453756 of chromosome 2 of the duck genome and a single nucleotide base mutation (T>C) at bp 37483773 of chromosome 7 of the duck genome were found. These two mutations significantly affected the carnosine content in duck meat. By detecting the genotype of the duck to be tested at these two SNP sites, early selection for carnosine content in duck meat can be achieved, which can save production costs and accelerate genetic progress, thus having great economic application value and scientific research value. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 This is the result diagram of the whole gene association analysis in Example 1. DETAILED DESCRIPTION

[0076] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0077] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0078] The quantitative experiments in the following examples were performed in triplicate unless otherwise specified.

[0079] Experimental animals: Peking ducks and Liancheng white ducks were hybridized to obtain groups with different blood relationship ratios (Peking duck: Liancheng white duck = 100%:0; 75%:25%; 75%:25%; 50%:50%; 50%:50%; 25%:75%; 0:100%, i.e., R1-R7 individuals). The ducks were raised under the same environmental and dietary conditions until 6 weeks of age, then slaughtered under the same environmental conditions and 381 breast muscle samples were collected.

[0080] In the embodiment, the carnosine content in duck meat is used as a marker.

[0081] The composition of the feed used in the examples is shown in Table 1. The nutritional levels in the feed are (% represents mass percentage): crude protein 17.59%, metabolizable energy 12.64 MJ, lysine 0.91%, methionine 0.4%, calcium 0.99%, and phosphorus 0.42%.

[0082] Table 1. Raw material composition of feed

[0083]

[0084]

[0085] The premix provides per kilogram of feed: vitamin A 8000IU, vitamin D3 3000IU, vitamin E 20IU, vitamin K3 2mg, vitamin B1 0.65mg, vitamin B2 2.21mg, pantothenic acid 3.51mg, niacin 19.8mg, pyridoxine 3.25mg, biotin 0.20mg, folic acid 0.28mg, vitamin B12 0.02mg, manganese 80mg, iron 60mg, copper 10mg, zinc 60mg, iodine 1.0mg, and selenium 0.3mg.

[0086] Example 1: Determination of the correlation between specific SNP and pectoral muscle carnosine content

[0087] Experimental materials: Peking ducks and Liancheng white ducks were hybridized to obtain groups with different blood relationship ratios (Peking duck: Liancheng white duck = 100%:0, 75%:25%, 75%:25%, 50%:50%, 50%:50%, 25%:75%, 0:100%, i.e., R1-R7 individuals). The ducks were raised under the same environmental and dietary conditions until 6 weeks of age, then slaughtered under the same environmental conditions and 381 breast muscle samples were collected.

[0088] 1. Detection of carnosine content in duck meat

[0089] The experimental animals were maintained under the same feed and conditions, with free access to food and water. Carnosine content in the breast muscle of each individual was measured by LC-MS at 42 days of age. During this period, the feed used was the same as the feed for the growing period of broiler ducks (Table 1). Carnosine content was analyzed using Analyst 1.6.3 software (ABSciex).

[0090] 2. Discovery of SNP Molecular Markers

[0091] 1. Blood sample collection: When the experimental animals grow to 42 days old, collect the duck wing venous blood to be tested using sodium heparin anticoagulation blood collection tubes and store at -20℃ for later use.

[0092] 2. Whole blood genomic DNA extraction: The specific operation method refers to the instructions of the blood genomic DNA extraction kit (Tiangen, DP319).

[0093] 3. Genotyping: Genomic DNA from each duck was collected and whole-genome resequencing was performed using the Illumina HiSeq X-Ten sequencing platform. The sequencing depth for each individual was approximately 5×, following the Illumina standard operating procedures. After quality control, the off-machine data were aligned and genotypes extracted using the bioinformatics software packages BWA and GATK.

[0094] 3. Genome-wide association analysis of carnosine content in pectoral muscle

[0095] The genome-wide association analysis between carnosine content and genotype in pectoral muscle was performed using the compressed mixed linear model of EMMAX software. Figure 1 , the horizontal axis represents the chromosome number, and the vertical axis represents -log 10 (P).

[0096] Two SNPs were found to be significantly associated with the carnosine content in duck meat, namely nucleotide position 42453756 on chromosome 2 and nucleotide position 37483773 on chromosome 7. For the sake of simplicity, the former will be referred to as specific SNP1 and the latter as specific SNP2.

[0097] A pair of primers, consisting of F1 and R1, was designed based on the specific SNP1. The target sequence of F1 and R1 in duck genomic DNA is 580 bp. The specific SNP1 is located at position 511 of the target sequence (SEQ ID NO: 1 in the sequence listing), and its nucleotide type is C or T. The nucleotide sequence of SEQ ID NO: 1 is the sequence from physical position 42453246 to 42453855 on duck chromosome 2. In the sequence listing, the "y" in SEQ ID NO: 1 represents C or T.

[0098] F1 (sequence 2 of the sequence listing): 5'-CTGGCGGAAGAAGTTGA-3';

[0099] R1 (sequence 3 in the sequence listing): 5'-AAGGTTCGCAGGGTTTT-3'.

[0100] A pair of primers, consisting of F2 and R2, was designed based on the specific SNP2. The target sequence of F2 and R2 in duck genomic DNA is 664 bp. The specific SNP is located at position 74 of the target sequence (SEQ ID NO: 4 in the sequence listing), and its nucleotide type is T or C. The nucleotide sequence of SEQ ID NO: 4 is the sequence from physical position 37483700 bp to 37484363 bp on duck chromosome 2. In the sequence listing, the "y" in SEQ ID NO: 4 represents C or T.

[0101] F2 (sequence 5 of the sequence listing): 5'-GTTGAGGGCTGCTTACCG-3';

[0102] R2 (Sequence 6 in the Sequence Listing): 5'-TCTGAGATGTGCCGTGGA-3'.

[0103] Example 2: Application of specific SNP1 and SNP2 in identifying carnosine content in duck meat

[0104] Experimental animals: Peking ducks and Liancheng white ducks were hybridized to obtain groups with different blood relationship ratios (Peking duck: Liancheng white duck = 100%:0; 75%:25%; 75%:25%; 50%:50%; 50%:50%; 25%:75%; 0:100%, i.e., R1-R7 individuals). The ducks were raised under the same environmental and dietary conditions until 6 weeks of age. 381 ducks were slaughtered under the same environmental conditions and breast muscle samples were collected.

[0105] 1. Detection based on specific SNP genotype

[0106] 1. Blood sample collection

[0107] The wing vein blood of the experimental animals was collected using a sodium heparin anticoagulant blood collection tube and stored at -20℃ for later use.

[0108] 2. Extraction of genomic DNA

[0109] Take the venous blood obtained in step 1 and extract genomic DNA.

[0110] 3. Genotype detection

[0111] Using the genomic DNA obtained in step 2 as a template, PCR amplification was performed using the primer pair consisting of F1 and R1 in Example 1, and the PCR amplification product was sequenced. Using the genomic DNA obtained in step 2 as a template, PCR amplification was performed using the primer pair consisting of F2 and R2 in Example 2, and the PCR amplification product was sequenced.

[0112] The results showed that PCR amplification products of 580 bp were obtained from 381 experimental animals using F1 and R1, and their nucleotide sequences were all Sequence 1 in the sequence listing; PCR amplification products of 664 bp were obtained from F2 and R2, and their nucleotide sequences were all Sequence 4 in the sequence listing.

[0113] Based on the specific SNP1, 381 experimental animals were divided into three genotypes: TT, CC, and TC. The TT genotype indicates that the 511th nucleotide of sequence 1 in the sequence listing of the duck genome is homozygous for T; the CC genotype indicates that the 511th nucleotide of sequence 1 in the sequence listing of the duck genome is homozygous for C; and the TC genotype indicates that the 511th nucleotide of sequence 1 in the sequence listing of the duck genome is heterozygous for T and C. Among the 381 experimental animals, 6 had the TT genotype, 324 had the CC genotype, and 51 had the TC genotype. The carnosine content in the pectoral muscle of the experimental animals of different genotypes is shown in Tables 2, 3, and 4.

[0114] Based on the specific SNP 2, 381 experimental animals were divided into three genotypes: TT, CC, and TC. The TT genotype indicates homozygous T at nucleotide position 74 of sequence 4 in the sequence listing of the duck genome; the CC genotype indicates homozygous C at nucleotide position 74 of sequence 4 in the sequence listing of the duck genome; and the TC genotype indicates heterozygous T and C at nucleotide position 74 of sequence 4 in the sequence listing of the duck genome. Of the 381 experimental animals, 95 had the CC genotype, 120 had the TC genotype, and 166 had the TT genotype. The carnosine content in the pectoral muscle of the experimental animals of different genotypes is shown in Tables 2, 3, and 5.

[0115] Table 2. Carnosine content in duck breast muscle and SNP1 and SNP2 genotype detection results

[0116]

[0117]

[0118]

[0119]

[0120]

[0121] Table 3. Statistical results of carnosine content in duck breast muscle and SNP1 and SNP2 genotype detection

[0122]

[0123] Table 4. SNP1 genotype and carnosine content

[0124]

[0125] Table 5. SNP2 genotype and carnosine content

[0126]

[0127] 3. Correlation analysis between genotype and carnosine content in pectoral muscle

[0128] Statistical analysis was performed using the GLM procedure of the SAS statistical analysis software package. Variance statistical analysis was performed on the genotypes of the test duck groups and the carnosine content in the breast muscle based on the generalized linear model. P-value < 0.05 indicated a significant difference.

[0129] Statistical analysis model: y = μ + G + e

[0130] Where: y represents the individual phenotypic value; μ represents the population mean; G represents the genotype effect; and e represents the residual effect.

[0131] The results showed that the carnosine content in breast muscle of three genotype ducks at 42453756bp on chromosome 2 (specific SNP1) was significantly different (P-value = 3.54 × 10 -16 ); The carnosine content in breast muscle of ducks with three genotypes at 37483773bp on chromosome 7 (specific SNP2) was extremely significant (P-value = 0.002). The carnosine content of experimental animals with TT genotype at 42453756bp on chromosome 2 was significantly higher than that of TC genotype (P-value = 0.0004) and CC genotype (P-value = 7.84 × 10 -5 ); and the carnosine content of TC genotype was significantly higher than that of CC genotype (P-value = 7.66 × 10 -15 The carnosine content of experimental animals with TT genotype at 37483773bp on chromosome 7 was significantly higher than that of TC genotype (P-value=0.025) and CC genotype (P-value=8.45×10 -9 ), the carnosine content of TC genotype was significantly higher than that of CC genotype (P-value=0.001).

[0132] In summary, when breeding duck breeds with high carnosine content in breast muscle, it is best to select ducks with TT genotype at SNP1 as parents for breeding, and ducks with TT genotype at SNP2 as parents for breeding. During breeding, individuals with TC and CC genotypes at SNP1 are eliminated; individuals with TC and CC genotypes at SNP2 are eliminated.

[0133] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that further improvements can be made to the present invention. In short, according to the principles of the present invention, this application is intended to include any changes, uses or improvements to the present invention, including changes that depart from the disclosed scope in this application and are made using conventional techniques known in the art.

Claims

1. Use of a substance for detecting the genotypes of two SNPs, SNP1 and SNP2, in a duck genome in any of the following: (1) Identify or assist in identifying the content of carnosine in duck meat; (2) Screening or breeding duck breeds with high carnosine content in duck meat; (3) Duck breeding; (4) Prepare products for identifying or assisting in identifying the content of carnosine in duck meat; (5) Preparation of products for screening or breeding duck breeds with high carnosine content in duck meat; (6) Preparation of duck breeding products; The SNP1 is a site on duck chromosome 2, the nucleotide type of which is T or C, and is the 511th nucleotide of sequence 1 in the sequence list. The SNP2 is a site on duck chromosome 7, the nucleotide type of which is T or C, and is the 74th nucleotide of sequence 4 in the sequence list; The duck breeding is to cultivate duck breeds with high carnosine content in duck meat; The substance is as follows D1), D2) or D3): D1) the substance is a primer composition for amplifying a duck genomic DNA fragment including the SNP1 and SNP2; D2) the substance is a PCR reagent containing the primer combination described in D1); D3) the substance is a kit containing the primer composition described in D1) or the PCR reagent described in D2); The primer composition comprises primer set 1 and primer set 2, wherein primer set 1 comprises F1 and R1, and primer set 2 comprises F2 and R2: Said F1 is the DNA molecule shown in sequence 2; Said R1 is the DNA molecule shown in sequence 3; Said F2 is the DNA molecule shown in Sequence 5; The R2 is a DNA molecule shown in Sequence 6.

2. A method for identifying or assisting in identifying the content of carnosine in duck meat, characterized in that: The method comprises detecting the genotypes of the two SNPs, SNP1 and SNP2, in the genome of the duck to be tested, and identifying or assisting in identifying the carnosine content in duck meat according to the genotypes of the two SNPs in the duck to be tested: The SNP1 is a site on duck chromosome 2, the nucleotide type of which is T or C, and is the 511th nucleotide of sequence 1 in the sequence list; the genotype is TT, TC or CC, the TT is the homozygous type of the SNP1 being T, the CC is the homozygous type of the SNP1 being C, and the TC is the heterozygous type of the SNP1 being T and C; The SNP2 is a site on duck chromosome 7, the nucleotide type of which is T or C, and is the 74th nucleotide of sequence 4 in the sequence list; the genotype is TT, TC or CC, the TT is the homozygous type of the SNP2 being T, the CC is the homozygous type of the SNP site being C, and the TC is the heterozygous type of the SNP2 being T and C; Wherein, 1) the duck to be tested whose genotype of SNP1 is TT and the duck to be tested whose genotype of SNP2 is TT is or is a candidate for a variety with high carnosine content in duck meat; 2) The duck to be tested whose SNP1 genotype is TC genotype or CC genotype, and / or the duck to be tested whose SNP2 genotype is TC genotype or CC genotype is or is a candidate for a breed with low carnosine content in duck meat; 3) The carnosine content of the ducks whose SNP1 genotype is TT and whose SNP2 genotype is TT is higher than that of the ducks whose SNP1 genotype is TC or CC, and / or whose SNP2 genotype is TC and CC.

3. Application of the method according to claim 2 in duck breeding.

4. A method for duck breeding, characterized in that: The method comprises detecting the genotype of the SNP site described in claim 1 in the duck genome, selecting ducks whose SNP1 genotype is TT and ducks whose SNP2 genotype is TT as parents for breeding, wherein in the ducks whose SNP1 genotype is TT, the TT is a homozygous type of the SNP1 being T, and in the ducks whose SNP2 genotype is TT, the TT is a homozygous type of the SNP2 being T. The breeding purpose of the method comprises breeding ducks with a high carnosine content in duck meat.

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