Molecular Markers for Identifying Salt-Tolerant Genotypes of Tomato and Their Applications

Abstract

The present invention relates to the technical field of tomato salt tolerance, and specifically relates to a molecular marker for identifying tomato salt-tolerant genotypes and its application. The molecular marker is a 6-bp deletion at position 5101860 of SL2.50ch07 or an 18-bp deletion at position 5090520 of SL2.50ch07. Among them, the 6-bp deletion at position 5101860 of SL2.50ch07 is the major locus for salt tolerance. This molecular marker is a co-dominant marker related to tomato salt tolerance, which can be used to distinguish whether the material is homozygous at the salt tolerance-related InDel locus. Without the need for enzyme digestion, only one PCR reaction and gel electrophoresis are required to identify the salt tolerance of tomato plants, and it can effectively assist in the breeding of tomato salt-tolerant germplasm resources.

Description

Technical Field

[0001] The present invention relates to the technical field of tomato salt tolerance, and specifically relates to a molecular marker for identifying tomato salt-tolerant genotypes and its application. Background Art

[0002] Soil salinization is one of the important reasons affecting tomato growth and yield. The ionic toxicity caused by salt stress is mainly the imbalance of sodium and potassium ion ratios in cells. As the main ion in saline-alkali soil, sodium is mainly absorbed from plant roots and accumulated in photosynthetic tissues. The imbalance of sodium ions will cause cytotoxicity, thereby reducing plant productivity. Therefore, creating salt-tolerant germplasm resources that can adapt to saline-alkali soil, breeding new salt-tolerant varieties, and increasing the yield of tomatoes in saline-alkali soil are of great significance for promoting sustainable development. Summary of the Invention

[0003] Through genome-wide association analysis, the present invention identified genetic loci InDel_18 and InDel_6 related to tomato salt tolerance. Through analysis, it was found that these two InDels are located in the strongest association signals on chromosome 7 and include members of the potassium ion transport family, SlHKT1; 1 and SlHKT1; 2, which are involved in tomato salt stress loci. Further research found that the InDel 6 locus at SL2.50ch07:5101860 is the main functional locus for salt tolerance. One of the purposes of the present invention is to protect the above-mentioned molecular marker for identifying tomato salt-tolerant genotypes, specifically the 6bp deletion at SL2.50ch07:5101860 or the 18bp deletion at SL2.50ch07:5090520.

[0004] This molecular marker is a co-dominant marker related to tomato salt tolerance, which can distinguish whether the material is homozygous at the salt tolerance-related InDel locus. In addition, this molecular marker does not require enzyme digestion, and only one PCR reaction and gel electrophoresis are needed to identify whether a tomato plant has salt tolerance resistance. Using this marker, salt-tolerant resources in current tomato resources can be effectively screened. At the same time, the main salt-tolerant control gene of tomatoes can be quickly and accurately introduced into excellent tomato parents by combining conventional breeding methods, creating salt-tolerant germplasm resources that can adapt to saline-alkali soil, breeding new salt-tolerant varieties, and increasing the yield of tomatoes in saline-alkali soil.

[0005] Another purpose of the present invention is also to protect the primers for amplifying the above-mentioned molecular marker.

[0006] As a preferred embodiment, the primers at least include a forward outer primer as shown in SEQ ID NO.3, a reverse outer primer as shown in SEQ ID NO.4, a forward inner primer as shown in SEQ ID NO.5, and a reverse inner primer as shown in SEQ ID NO.6.

[0007] A third object of the present invention is also to protect a kit for identifying salt-tolerant genotypes of tomatoes, which comprises the above primers.

[0008] A fourth object of the present invention is also to protect a method for identifying salt-tolerant genotypes of tomatoes, which comprises the following steps: extracting the total DNA of a tomato sample to be tested, using the total DNA of the tomato to be tested as a template, and performing amplification with primers having sequences as shown in SEQ ID NOs. 3 to 6, and making a determination based on the length of the amplified fragment; wherein, those with amplified band patterns of 486 bp and 191 bp are salt-tolerant genotypes, those with amplified band patterns of 480 bp and 332 bp are salt-intolerant genotypes, and those with both 191 bp and 332 bp amplified are heterozygous genotypes.

[0009] As a preferred embodiment, the amplification system is: 9.6 μL of 2*Tag mix, 0.4 μL of each outer primer, 0.6 μL of each inner primer, 1 μL of DNA template, and 7.4 μL of ddH2O.

[0010] As a preferred embodiment, the amplification program is: pre-denaturation at 94 °C for 3 min, denaturation at 94 °C for 30 s, annealing at 55 °C for 30 s, extension at 72 °C for 30 s for 39 cycles, extension at 72 °C for 5 min, and cooling to 15 °C.

[0011] The present invention also aims to protect the application of the above molecular markers and primers in identifying salt-tolerant genotypes of tomatoes.

[0012] The present invention also aims to protect the application of the above molecular markers and primers in breeding salt-tolerant tomato varieties.

[0013] The present invention also aims to protect the application of the above molecular markers and primers in cultivating salt-tolerant tomatoes. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It shows the detection results of the core germplasm materials and their sodium and potassium ions in Example 1, where A is the classification ratio of 508 germplasm materials, B is the detection results of Na + , K + and Na + / K + ratio in the above-ground part at the seedling stage, and C is the detection results of Na + , K + and Na + / K + ratio in the underground part at the seedling stage;

[0015] Figure 2 It shows the results of genome-wide association analysis, where A is the association result of Na + content in the above-ground part at the seedling stage, and B is the association result of Na + / K+ Ratio correlation results. C is the gene analysis result of four haplotype materials at InDel_18, and D is the gene analysis result of four haploid materials at InDel_6;

[0016] Figure 3 For the further genome-wide association analysis results, where A is the schematic diagram of the total association analysis, B is the haploid typing analysis, C is the four haplotype materials, and D is the Na in the four haplotype materials + / K + Ratio analysis;

[0017] Figure 4 For the phenotypic inhibition of the four haplotype materials in Example 2 under 0 and 200 mM salt treatments, where A is the statistical results of plant height, root length, above-ground fresh weight, and below-ground fresh weight, and B is the phenotypic observation results;

[0018] Figure 5 For some electrophoresis detection results in the development of molecular markers in Example 3;

[0019] Figure 6 For the gel electrophoresis results when some materials involved in Examples 1 and 2 are detected with the NTC7 molecular marker;

[0020] Figure 7 For the ratio results of Na + / K + in the above-ground parts of some verification materials in Example 4. Specific implementation manners

[0021] The following further elaborates on the present invention in conjunction with specific embodiments, so that those skilled in the art can understand the present invention more clearly.

[0022] Example 1 Obtaining InDel loci closely related to tomato salt tolerance

[0023] When plants are subjected to salt stress, some tolerance mechanisms will be induced, including inhibiting the absorption of Na + , promoting the efflux of Na + , redistributing Na + in leaves, and maintaining cellular ion balance (especially the ratio of Na + / K + ). Select 508 tomato re-sequenced core germplasm materials for planting, including 287 large-fruited tomatoes (BIG), 187 cherry tomatoes (CER), and 46 currant tomatoes (PIM) ( Figure 1 A).

[0024] Samples of tomato plants at the seedling stage were taken, digested, dried, ground, and the sodium and potassium ions were measured, and the ratio of sodium to potassium ions was calculated. Through evolutionary analysis, it was found that in the aboveground parts, the Na + content and the Na + / K + ratio in large-fruited tomatoes were significantly lower than those in cherry tomatoes and currant tomatoes. The K + content in large-fruited tomatoes and cherry tomatoes was relatively higher than that in currant tomatoes, but the difference among the three groups was not significant ( Figure 1 B). In the underground parts of tomato seedlings, the Na + content and the Na + / K + ratio in large-fruited tomatoes were significantly higher than those in cherry tomatoes and currant tomatoes. The K + content in large-fruited tomatoes and cherry tomatoes was significantly higher than that in currant tomatoes ( Figure 1 C). These data indicate that the domestication and improvement process of large-fruited tomatoes led to a decrease in the Na + content and the Na + / K + ratio in the aboveground parts.

[0025] To reveal the natural variation in Na + and K + accumulation and the genetic loci related to salt tolerance in tomatoes, genome-wide association analysis was further used to analyze the genetic basis of the variation in Na + content, K + content, and Na + / K + ratio in tomatoes. Through analysis, it was found that the Na + content and the Na + / K + ratio in this set of data were associated with the same position on chromosome 7, and multiple significant loci were detected at this chromosomal position ( Figure 2 A, B). SNPs and InDels were analyzed for 200 kb upstream and downstream of this significant locus, and multiple significant InDels and SNPs were found in this interval. In addition, the analysis also found that the associated loci on chromosome 7 included members of the potassium ion transport family, SlHKT1;1 and SlHKT1;2 ( Figure 3 A), which are involved in tomato salt stress tolerance. Further analysis found that the natural variation site InDel_6 on the promoter of SlHKT1;1 and the natural variation site InDel 18 on the promoter of SlHKT1;2 were highly associated with the Na + content and the Na + / K + ratio in the aboveground parts of tomatoes ( Figure 3 A).

[0026] Among them, InDel_6 is located at SL2.50ch07:5101860, and its sequence is: 5’-TACCAATTAATTGAATGCAATGTATTATTCAGCCACGGAATCAACACACAATTGCATTTGTTATATATGGAAATGTGGCATGCCACAAGTTAAAATAGTATTGGTTAGTCTAGTTATAACTTAATAGTAAATGATTCAAACATGTTATTGTAGGCCTAGCACTATAAAAACAGCGTGAATTACTGTAAAAATTCACAGGTTACTTATTATTTTTGTAAATTTTCATACTGATTCGCAGGAAAAAATTTCTACATAATTTACAGTTTTCTTATATTGTAGGTTGCATATCGATCGATTTGATTCATTACTTATCAATTTATAGACATATTAAATCGTTTTAGAAT CATATG As shown in CATATGCAGTACTGTTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGCCACGTGTTGCTTCCTAATTTGACCATGTGTCAAGCACGGTTTGTACCCCCCTACTATACATAGTATATACA-3’ (SEQ ID NO.1), where TCATATG is the genomic sequence, and after deleting 6 bp bases, it becomes T.

[0027] InDel_18 is located at SL2.50ch07:5090520, and its sequence is: 5’-ACCCATTCCATCATTTTTTTTTAGTGATGTTTAAGTTTGGTCTACATGAAAATAAATTCAATTGCAACCTCCACTTCAGCTCGTGTGTTGTTGGGAAATAATAATTCCATTTAGTAGTAAGATCCACCTAGAAAATAAGAATAAGAATAAGAATAAATAAATAATAAAAATATCATGTGTCATAATCAAAAAATTGAGACCATTCATAACAATATCTATTCAATTTCTCTAATGGAATCATAATTTAAATTTAAATCCATTTTAATATTATATTATAACATGTAATAACATACACTTATCGTATGCATAAATG ATTAAATGAAATAA ATCAT As shown in GATTTATATGTCTAAATAAATTTTATCGATAAATTTAAAATACATTAATATATTAATTAAGCCTTTAAAATCATCATGGCAAACAAGTTGATGATATGACATGACCTGCAATGACCAATGATGCATGTGTATCTTACTACACTTTGACACTTTCATTAAAAATCAACGCAGTGCCAAATAAGTGATCGATAGGTCCAATATAATAAGATGTGGCTAAAATCATTTCAATCAATATCAATTATAATAATTTTATATTATTTCGTATTATTTATTTGGCTATATATT-3’ (SEQ ID NO.2), where ATTAAATGAAATAAATCAT is the genomic sequence, and after deleting 18 bp of bases, it becomes A.

[0028] Confirmation of InDel Loci Closely Related to Tomato Salt Tolerance in Example 2

[0029] Subsequently, we performed haplotype analysis based on InDel_6 and InDel_8 ( Figure 3 B), respectively selected 4 high-haplotype materials and low-haplotype materials as templates, designed primers upstream and downstream of these two InDel loci respectively, carried out PCR amplification, and found through sequencing results that there were 6 bp and 18 bp deletions in the low-haplotype materials ( Figure 2 C, D).

[0030] To demonstrate the contribution rates of two InDels to the salt tolerance trait, the Na + content and the Na + / K + ratio of four haplotypes were further analyzed. It was found that compared with the alleles commonly present in cultivated species, InDel_6 / InDel_18 mainly exists in wild tomatoes, which is beneficial to their stronger salt tolerance (for the classification of cultivated and wild tomatoes, refer to Ye J, Wang X, Wang W, Yu H, Ai G, Li C, Sun P, Wang X, Li H, Ouyang B, Zhang J, Zhang Y, Han H, Giovannoni JJ, Fei Z, Ye Z. Genome-wide association study reveals the genetic architecture of 27 agronomic traits in tomato. Plant Physiol. 2021 Aug 3; 186(4): 2078 - 2092. doi: 10.1093 / plphys / kiab230. PMID: 34618111; PMCID: PMC8331143.). In addition, compared with the two haplotypes Del_18 / Del_6 and Ins_18 / Del_6, the Na + / K + ratio of Del_18 / Ins_6 and Ins_18 / Ins_6 was significantly reduced ( Figure 3 D). Therefore, compared with InDel_18, InDel_6 has a higher contribution. Del_6 was initially confirmed as the major locus and named NTC7.

[0031] Tomato materials with the four haplotypes shown in Figure 3 C were selected for salt treatment and phenotype identification. The four haplotype materials were Del_18 / Del_6 (TS-17, TS-123), Ins_18 / Del_6 (TS-18, TS-156), Del_18 / Ins_6 (TS-50, TS-16), and Ins_18 / Ins_6 (TS-680, TS-9). After treating the tomato materials with normal nutrient solution for 28 days, they were respectively treated with normal nutrient solution and nutrient solution containing 200 mM NaCl for 10 days, with 3 replicates for each. The plant height and root length of the four haplotype materials under different conditions are as shown in Figure 4 . Figure 4 A shows the statistical results of plant height, root length, aboveground fresh weight, and underground fresh weight, where Figure 4 B shows the phenotype observation results of the four haplotype plants TS-17, TS-156, TS-50, and TS-680.

[0032] As can be seen from Figure 4 A, under 200 mM salt treatment, compared with the two haplotypes of Del_18 / Ins_6 (TS-50, TS-16) and Ins_18 / Ins_6 (TS-680, TS-9), the plant height and root length of Del_18 / Del_6 (TS-17, TS-123) and Ins_18 / Del_6 (TS-18, TS-156) were significantly shorter, and the fresh weights of the above-ground and underground parts were significantly reduced. As can be seen from Figure 4 B, it can be clearly seen that under salt stress, compared with TS-50 and TS-680, the leaves of TS-17 and TS-156 withered and the plants grew short. Thus, it was confirmed that Del_6 was the major locus related to salt tolerance, and the haplotype materials of Del_6 were determined to be salt-intolerant materials, while the haplotype materials of Ins_6 were salt-tolerant materials.

[0033] Among them, the formula of the normal nutrient solution was: 0.8 mM Ca(NO3)2·4H2O, 0.83 mM KH2PO4·3H2O, 0.75 mM MgSO4·7H2O, 1.5 mM KNO3, 11.6 μM H3BO3, 2.4 μM MnSO4·H2O, 0.2 μM ZnSO47·H2O, 0.1 μM CuSO4·5H2O, 0.1 μM NaMoO4·2H2O, 50 μM FeSO4·7H2O, 50 μM EDTA-Na2.

[0034] Example 3 Development of molecular markers

[0035] According to this InDel_6 locus, molecular marker typing primers were designed. By designing ARMS-PCR primers, the full length was amplified to be 486 bp or 480 bp. If InDel_6 existed at this locus, bands of 480 bp and 332 bp would appear. If InDel_6 did not exist, bands of 486 bp and 191 bp would appear. If it was heterozygous, theoretically four bands of 486 bp, 480 bp, 332 bp, and 191 bp would appear. However, since the difference between the two bands of 480 bp and 486 bp was too small, three bands could be seen on the gel imaging. That is, the three-band materials were heterozygous materials. See Figure 5 , and the electrophoresis results of several haploid materials in Examples 1 and 2 are shown in Figure 6 . Among them, the designed specific primer sequences are as follows:

[0036] Forward outer primer NTC7-out-F 5'-AATCAACACACAATTGCATTTGTTA-3' (SEQ ID NO.3);

[0037] Reverse outer primer NTC7-out-R 5'-GCAAGAGAAATATGGATCATGAAAA-3' (SEQ ID NO.4);

[0038] Forward inner primer NTC7-in-F 5'-CGTTTTAGAATCATATGCATATGCA-3' (SEQ ID NO.5);

[0039] Reverse inner primer NTC7-in-F 5'-ATATAGCTACAACAGTACTGCATACGA-3' (SEQ ID NO.6).

[0040] The amplified 486bp band sequence is: 5'AATCAACACACAATTGCATTTGTTATATATG GAAATGTGGCATGCCACAAGTTAAAATAGTATTGGTTAGTCTAGTTATAACTTAATAGTAAATGATTCAAACATGTTATTGTAGGCCTAGCACTATAAAAACAGCGTGAATTACTGTAAAAATTCACAGGTTACTTATTATTTTTGTAAATTTTCATACTGATTCGCAGGAAAAAATTTCTACATAATTTACAGTTTTCTTATATTGTAGGTTGCATATCGATCGATTTGATTCATTACTTATCAATTTATAGACATATTAAATCGTTTTAGAATCATATGCATATGCAGTACTGTTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGC-3' (SEQ IDNO.7);

[0041] The amplified 480bp band sequence is: 5'AATCAACACACAATTGCATTTGTTATATATG GAAATGTGGCATGCCACAAGTTAAAATAGTATTGGTTAGTCTAGTTATAACTTAATAGTAAATGATTCAAACATGTTATTGTAGGCCTAGCACTATAAAAACAGCGTGAATTACTGTAAAAATTCACAGGTTACTTATTATTTTTGTAAATTTTCATACTGATTCGCAGGAAAAAATTTCTACATAATTTACAGTTTTCTTATATTGTAGGTTGCATATCGATCGATTTGATTCATTACTTATCAATTTATAGACATATTAAATCGTTTTAGAATCATATGCAGTACTGTTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGC-3'(SEQ ID NO.8);

[0042] The amplified 332bp band sequence is: 5'ATATAGCTACAACAGTACTGCATATGATTCT AAAACGATTTAATATGTCTATAAATTGATAAGTAATGAATCAAATCGATCGATATGCAACCTACAATATAAGAAAACTGTAAATTATGTAGAAATTTTTTCCTGCGAATCAGTATGAAAATTTACAAAAATAATAAGTAACCTGTGAAT TTTTACAGTAATTCACGCTGTTTTTATAGTGCTAGGCCTACAATAACATGTTTGAATCATTTACTATTAAGTTATAACTAGACTAACCAATACTATTTTAACTTGTGGCATGCCACATTTCCATATATAACAAATGCAATTGTGTGTTGATT-3'(SEQ ID NO.9);

[0043] The amplified 191bp band sequence is: 5'CGTTTTAGAATCATATGCATATGCAGTACTG TTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGC-3' (SEQ ID NO.10).

[0044] Example 4 Verification of Salt Tolerance Molecular Markers

[0045] Select 96 tomato TS population materials that have been re-sequenced in the laboratory (Ye et al., 2021) to verify the above-determined NTC7 (InDel_6 locus) molecular marker. The specific steps are as follows:

[0046] (1) Extract the DNA of tomato materials

[0047] Using tomato genomic DNA as a template with a concentration of 80 - 120 ng / ul, perform PCR amplification with the primers described in Example 3. The forward primers are SEQ ID NO.3 and SEQ ID NO.5, and the reverse primers are SEQ ID NO.4 and SEQ ID NO.6. The total volume of the PCR reaction is 20 μL, and the specific components are as follows: 2*Tag mix 9.6 μL, outer primers (SEQ ID NO.3 and SEQ ID NO.4) 0.4 μL each, inner primers (SEQ ID NO.5 and SEQ ID NO.6) 0.6 μL each, DNA template 1 μL (100 - 200 ng / μL), ddH2O 7.4 μL.

[0048] (2) PCR amplification:

[0049] The reaction program is pre-denaturation at 94°C for 3 min, denaturation at 94°C for 30 s, annealing at 55°C for 30 s, extension at 72°C for 30 s for 39 cycles, extension at 72°C for 5 min, and cooling to 15°C.

[0050] (3) Gel electrophoresis detection:

[0051] The PCR products are electrophoresed on 2% agarose at 100V for 40 min, and the final results are shown on a gel imaging system.

[0052] (4) The results of some materials are as follows:

[0053] Electrophoresis results: Only bands of 486 bp and 191 bp were amplified from TS-60, TS-28, TS-56, TS-90, TS-115, TS-104, TS-38, TS-46, and TS-30, which were determined to be salt-tolerant materials. Only bands of 480 bp and 332 bp were amplified from TS-95, TS-39, TS-97, TS-22, TS-20, and TS-37, which were determined to be salt-intolerant materials. Bands of 486 bp, 480 bp, 332 bp, and 191 bp were amplified from TS-77 and TS-33, which were determined to be heterozygous materials. The electrophoresis results were consistent with the re-sequencing results.

[0054] After culturing the above materials under normal full-nutrient conditions for 35 days, the Na + , K + contents in the above-ground parts of the plants were measured, and their Na + / K + ratios were calculated. The results are shown in Figure 7 . As can be seen from Figure 7 , the Na + / K + ratio in the salt-tolerant materials was lower than that in the salt-intolerant materials, which was consistent with the research conclusion that an increase in the Na + / K + ratio in tomato plants would lead to a decrease in salt tolerance.

[0055] It is necessary to point out here that the above embodiments are only for further elaboration and explanation of the technical solution of the present invention, and not for further limitation of the technical solution of the present invention. The method of the present invention is only a preferred implementation, and not for limiting the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for identifying salt-tolerant tomato genotypes, characterized in that, It includes the following steps: Extract the total DNA of the tomato sample to be tested. Using the total DNA of the tomato to be tested as a template, amplify with primers shown in sequences such as SEQ ID NO.3 - 6, and make a determination according to the length of the amplified fragment. Among them, those with amplified band patterns of 486bp and 191bp are salt - tolerant genotypes, those with amplified band patterns of 480bp and 332bp are salt - intolerant genotypes, and those with amplified 191bp and 332bp simultaneously are heterozygous genotypes.

2. The method for identifying tomato salt-tolerant genotypes according to claim 1, characterized in that, The system for amplification is: 2*Tag mix 9.6μL, each outer primer 0.4μL, each inner primer 0.6μL, DNA template 1μL, ddH2O 7.4μL.

3. The method for identifying salt-tolerant tomato genotypes according to claim 1, wherein, The program for amplification is: pre - denaturation at 94°C for 3 min, 39 cycles of denaturation at 94°C for 30 s, annealing at 55°C for 30 s, extension at 72°C for 30 s, extension at 72°C for 5 min, and cooling to 15°C.

4. Application of molecular markers in identifying salt-tolerant tomato genotypes, wherein the molecular marker is a 6-bp deletion at position 5101860 of SL2.50ch07, InDel_6 is located at position 5101860 of SL2.50ch07, and its sequence is: 5’- TACCAATTAATTGAATGCAATGTATTATTCAGCCACGGAATCAACACACAATTGCATTTGTTATATATGGAAATGTGGCATGCCACAAGTTAAAATAGTATTGGTTAGTCTAGTTATAACTTAATAGTAAATGATTCAAACATGTTATTGTAGGCCTAGCACTATAAAAACAGCGTGAATTACTGTAAAAATTCACAGGTTACTTATTATTTTTGTAAATTTTCATACTGATTCGCAGGAAAAAATTTCTACATAATTTACAGTTTTCTTATATTGTAGGTTGCATATCGATCGATTTGATTCATTACTTATCAATTTATAGACATATTAAATCGTTTTAGAATCATATGCATATGCAGTACTGTTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGCCACGTGTTGCTTCCTAATTTGACCATGTGTCAAGCACGGTTTGTACCCCCCTACTATACATAGTATATACA-3’ (SEQ ID NO.1), wherein TCATATG is the genomic sequence, and after deleting 6 bp bases, it becomes T.

5. Use of molecular markers in breeding salt-tolerant tomato varieties, wherein the molecular marker is a 6-bp deletion at position 5101860 on SL2.50ch07, InDel_6 is located at position 5101860 on SL2.50ch07, and its sequence is: 5’- TACCAATTAATTGAATGCAATGTATTATTCAGCCACGGAATCAACACACAATTGCATTTGTTATATATGGAAATGTGGCATGCCACAAGTTAAAATAGTATTGGTTAGTCTAGTTATAACTTAATAGTAAATGATTCAAACATGTTATTGTAGGCCTAGCACTATAAAAACAGCGTGAATTACTGTAAAAATTCACAGGTTACTTATTATTTTTGTAAATTTTCATACTGATTCGCAGGAAAAAATTTCTACATAATTTACAGTTTTCTTATATTGTAGGTTGCATATCGATCGATTTGATTCATTACTTATCAATTTATAGACATATTAAATCGTTTTAGAATCATATGCATATGCAGTACTGTTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGCCACGTGTTGCTTCCTAATTTGACCATGTGTCAAGCACGGTTTGTACCCCCCTACTATACATAGTATATACA-3’ (SEQ ID NO.1), wherein TCATATG is the genomic sequence, and after deleting 6 bp bases, it becomes T.

6. Application of molecular marker in cultivating salt-tolerant tomatoes, wherein the molecular marker is a 6-bp deletion at position 5101860 of SL2.50ch07. The molecular marker is a 6-bp deletion at position 5101860 of SL2.50ch07. InDel_6 is located at position 5101860 of SL2.50ch07, and its sequence is: 5’- TACCAATTAATTGAATGCAATGTATTATTCAGCCACGGAATCAACACACAATTGCATTTGTTATATATGGAAATGTGGCATGCCACAAGTTAAAATAGTATTGGTTAGTCTAGTTATAACTTAATAGTAAATGATTCAAACATGTTATTGTAGGCCTAGCACTATAAAAACAGCGTGAATTACTGTAAAAATTCACAGGTTACTTATTATTTTTGTAAATTTTCATACTGATTCGCAGGAAAAAATTTCTACATAATTTACAGTTTTCTTATATTGTAGGTTGCATATCGATCGATTTGATTCATTACTTATCAATTTATAGACATATTAAATCGTTTTAGAATCATATGCATATGCAGTACTGTTGTAGCTATATATTGTAACTTAAATAGTAAATGATTCAACAAGTTGCAGTATTATAGCTTAAATTATTTGTATATCTTTGCCCCCTTAAAGCCCATTATAACATGTTACTACTATTTACGAAAAATTCAAACTATTTTCATGATCCATATTTCTCTTGCCACGTGTTGCTTCCTAATTTGACCATGTGTCAAGCACGGTTTGTACCCCCCTACTATACATAGTATATACA-3’ (SEQ ID NO.1), where TCATATG is the genomic sequence, and after deleting 6 bp bases, it becomes T.

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