Application of biological silver nanoparticles synthesized based on bacillus velezensis in prevention and treatment of botrytis cinerea

Abstract

The invention discloses application of biological silver nanoparticles synthesized based on bacillus velezensis in prevention and treatment of tomato gray mold, and relates to the technical field of prevention and treatment of tomato gray mold. Researches find that the biological silver nanoparticles Bio-AgNPs have a relatively strong inhibition effect on the growth of botrytis cinerea hyphae, and when the concentration of the biological silver nanoparticles Bio-AgNPs is 100 mu g / mL, the growth inhibition rate of the botrytis cinerea hyphae is 100%. The Bio-AgNPs shows a good prevention and treatment effect on the tomato gray mold, after 40 [mu] g / mL of Bio-AgNPs is used for treating tomato fruits and leaves, the scab of the tomato fruits is obviously reduced by 52.21%, and the prevention and treatment effect on the tomato leaf gray mold is 40.19%.

Description

Technical Field

[0001] The present invention belongs to the field of crop disease control, and particularly relates to the application of biosilver nanoparticles synthesized by Bacillus velezensis Lnu-21 in the control of tomato gray mold Background Art

[0002] Tomato (Solarium lycopersicum L.) is a widely cultivated vegetable worldwide and an important source of nutrients such as lycopene, potassium, magnesium, calcium, and iron. As a major tomato-growing country, China's planting area accounts for 21.5% of the global planting area, with an annual output of approximately 55 million tons. Tomato gray mold is one of the main reasons for tomato yield reduction, generally resulting in a 20% - 30% reduction in tomato yield, and in severe cases, a reduction of more than 50%.

[0003] Tomato gray mold is caused by the infection of Botrytis cinerea. This pathogenic fungus is an airborne pathogen that can be spread by air currents, rainwater or irrigation water, and farm tools. Subsequently, it infects different parts of tomatoes, such as flowers, fruits, leaves, and stems, mainly invading through host wounds, senescent organs, or dead tissues, and mostly starting from the stigma or petals, gradually spreading to the fruit stalk and fruit, presenting grayish-white rot, and then growing a large amount of grayish-green mold layer along the lesion.

[0004] Currently, the main measure for controlling tomato gray mold is the use of chemical fungicides. Although the application of chemical fungicides can effectively reduce the occurrence of gray mold, the widespread use of fungicides brings many drawbacks, including the generation of pathogen resistance, increased production costs, environmental pollution, and threats to human health. In recent years, due to their high surface area and small size effect, nanomaterials have shown great application potential in plant disease management.

[0005] Silver nanoparticles (AgNPs) are artificially produced silver particle substances with sizes between 1 nm and 100 nm. Due to their excellent antibacterial properties, they are used as nano-fungicides for plant disease control. The synthesis methods of AgNPs include physical methods, chemical methods, and biological methods. Compared with physical and chemical methods, the biological synthesis method is simple, low-cost, easy to scale up production, does not involve toxic and harmful chemicals, and the bioactive substances used for synthesis can simultaneously act as reducing agents and capping agents. The prepared materials usually have good biocompatibility, lower toxicity, and higher stability. Summary of the Invention

[0006] To solve the above-mentioned existing technical problems, the present invention provides an application of biosilver nanoparticles synthesized by Bacillus velezensis Lnu-21 in preventing and controlling Botrytis cinerea of tomatoes.

[0007] To achieve the above invention object, the technical solution adopted by the present invention is: an application of biosilver nanoparticles synthesized based on Bacillus velezensis in preventing and controlling Botrytis cinerea of tomatoes.

[0008] Furthermore, the biosilver nanoparticles synthesized based on Bacillus velezensis are used for inhibiting the growth of Botrytis cinerea hyphae.

[0009] Furthermore, the biosilver nanoparticles synthesized based on Bacillus velezensis are used for preventing and controlling Botrytis cinerea of tomato fruits.

[0010] Furthermore, the biosilver nanoparticles synthesized based on Bacillus velezensis are used for preventing and controlling Botrytis cinerea of tomato leaves.

[0011] Furthermore, the biosilver nanoparticles synthesized based on Bacillus velezensis are used for promoting the germination of tomato seeds.

[0012] Furthermore, the biosilver nanoparticles synthesized based on Bacillus velezensis are used for promoting the growth of tomato seedlings.

[0013] Furthermore, the biosilver nanoparticles synthesized based on Bacillus velezensis are synthesized by Bacillus velezensis Lnu-21 with the preservation number of CGMCC NO.29565 and silver nitrate.

[0014] Furthermore, the preparation method of the biosilver nanoparticles synthesized based on Bacillus velezensis includes the following steps:

[0015] Activated culture of the strain: Bacillus velezensis Lnu-21 with the preservation number of CGMCC NO.29565 is placed on a nitrate solid medium for culture, a single colony is picked and added to a nitrate liquid medium for culture at 37°C for 45h - 50h to obtain a Bacillus velezensis culture solution;

[0016] Preparation of cell-free supernatant: The obtained Bacillus velezensis culture solution is centrifuged, and the supernatant obtained by centrifugation is filtered through a filter membrane with a diameter of 0.22μm to obtain a Bacillus velezensis cell-free supernatant;

[0017] Preparation of the stock solution of biological silver nanoparticles: The obtained cell-free supernatant of Bacillus velezensis was co-cultured with silver nitrate solution at 37 °C and 180 rpm for a reduction reaction for 45 h - 50 h to obtain the stock solution of biological silver nanoparticles; the concentration of the silver nitrate solution was 4 mM - 6 mM, and by volume ratio, the cell-free supernatant of Bacillus velezensis:silver nitrate solution = (1 - 3):(7 - 9).

[0018] Furthermore, the method is as follows: The stock solution of biological silver nanoparticles synthesized based on Bacillus velezensis was formulated into a medicament with sterile water and sprayed on the fruits and leaves of tomatoes.

[0019] Furthermore, in the medicament, the concentration of biological silver nanoparticles synthesized based on Bacillus velezensis was 1 μg / mL - 100 μg / mL.

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The biological silver nanoparticles Bio-AgNPs synthesized based on Bacillus velezensis provided by the present invention showed an obvious inhibitory effect on the mycelial growth of Botrytis cinerea through the mycelial growth inhibition experiment of Botrytis cinerea. When the concentration of Bio-AgNPs was 100 μg / mL, the mycelial growth inhibition rate of Botrytis cinerea was 100%.

[0022] 2. The biological silver nanoparticles Bio-AgNPs synthesized based on Bacillus velezensis provided by the present invention had a promoting effect on the germination of tomato seeds. After applying Bio-AgNPs, when its concentration was 1 μg / mL, the stem length of tomato seeds increased significantly by 34.38%. When its concentration was 5 μg / mL, the root length of tomato seeds increased significantly by 44.72%. When its concentration was 40 μg / mL, the number of lateral roots of tomato seeds increased significantly by 2.76.

[0023] 3. The biological silver nanoparticles Bio-AgNPs synthesized based on Bacillus velezensis provided by the present invention had a promoting effect on the growth of tomato seedlings. When the concentration of Bio-AgNPs was 20 μg / mL, the root length of tomato seedlings increased by 8.20%. When its concentration was 40 μg / mL, the dry weight of the underground part of tomato seedlings increased by 28.57%.

[0024] 4. The biological silver nanoparticles Bio-AgNPs synthesized based on Bacillus velezensis provided by the present invention had a good control effect on tomato fruit gray mold. After the tomato fruits were treated with Bio-AgNPs, when its concentration was 40 μg / mL, the lesion of tomato fruits decreased significantly by 52.21%.

[0025] 5. The bio-silver nanoparticles Bio-AgNPs synthesized based on Bacillus velezensis provided by the present invention have a good control effect on Botrytis cinerea of tomato leaves. For the tomato plants treated with Bio-AgNPs, the incidence rate is significantly reduced compared with the blank control group. Among them, the control effect of 40 μg / mL Bio-AgNPs on Botrytis cinerea of tomato leaves is 40.19%.

[0026] In summary, the Bio-AgNPs provided by the present invention can inhibit the growth of Botrytis cinerea, have a good control effect on Botrytis cinerea, and have the potential to promote the growth of tomatoes and seed germination. It is an emerging material on the road of plant disease management and agricultural sustainable development. Description of the Drawings

[0027] Figure 1 It is a result diagram of the inhibition of the mycelial growth of Botrytis cinerea by Bio-AgNPs in Example 2.

[0028] Figure 2 It is a result diagram of the influence of Bio-AgNPs on the seed germination of tomatoes in Example 3.

[0029] Figure 3 It is a result diagram of the influence of Bio-AgNPs on the growth of tomato seedlings in Example 4.

[0030] Figure 4 It is a result diagram of the control effect of Bio-AgNPs on Botrytis cinerea of tomato fruits in Example 5.

[0031] Figure 5 It is a result diagram of the control effect of Bio-AgNPs on Botrytis cinerea of tomato leaves in Example 6. Detailed Embodiments

[0032] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following will further clearly and completely describe the technical solutions of the present invention in combination with specific implementation schemes. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments.

[0033] Example 1 Preparation of Bio-silver Nanoparticles (Bio-AgNPs) Synthesized Based on Bacillus velezensis

[0034] The preparation method includes the following steps:

[0035] 1. Activation culture of the strain:

[0036] Nitrate solid medium: It is made of 0.3 g of yeast extract, 3 g of agar, 0.5 g of sodium nitrate, 1.5 g of glucose and 100 mL of water.

[0037] Nitrate liquid medium: Prepared from 0.3 g of yeast extract, 0.5 g of sodium nitrate, 1.5 g of glucose and 100 mL of water.

[0038] Bacillus velezensis Lnu-21 with the preservation number of CGMCC NO.29565 was cultured in a nitrate solid medium. Single colonies were picked and added to the nitrate liquid medium, and cultured with shaking at 37 °C and 180 rpm for 48 h to obtain a Bacillus velezensis culture solution.

[0039] 2. Preparation of cell-free supernatant:

[0040] The Bacillus velezensis culture solution obtained in step 1 was centrifuged at 8000 rpm for 20 min, and the supernatant obtained by centrifugation was filtered through a filter membrane with a diameter of 0.22 μm to obtain a cell-free supernatant of Bacillus velezensis.

[0041] 3. Preparation of bio-silver nanoparticles stock solution (Bio-AgNPs stock solution):

[0042] The cell-free supernatant of Bacillus velezensis obtained in step 2 was mixed with a 5 mM silver nitrate solution at a volume ratio of 3:7, and co-cultured at 37 °C and 180 rpm for 48 h for a reduction reaction. When the color no longer deepened further, a bio-silver nanoparticles stock solution (Bio-AgNPs stock solution) was obtained.

[0043] The bio-silver nanoparticles stock solution (Bio-AgNPs stock solution) obtained in step 3 was directly used in the experiments of Examples 2 - 6 below. It was also possible to obtain bio-silver nanoparticles (Bio-AgNPs) powder through freeze-drying.

[0044] Example 2 Effect of bio-silver nanoparticles (Bio-AgNPs) synthesized based on Bacillus velezensis on the mycelial growth of Botrytis cinerea

[0045] (I) The method is as follows:

[0046] The Bio-AgNPs stock solution prepared in Example 1 was respectively added to a potato dextrose agar (PDA) medium to form drug-containing plates, so that the final concentrations of Bio-AgNPs in the medium were 1 μg / mL, 2 μg / mL, 3 μg / mL, 4 μg / mL, 5 μg / mL, 10 μg / mL, 15 μg / mL, 20 μg / mL, 40 μg / mL, 60 μg / mL, 80 μg / mL, 100 μg / mL respectively. Then, a 7-mm mycelial disc of Botrytis cinerea was placed in the center of the plate, and PDA without Bio-AgNPs was used as a control. After culturing for 5 d, a vernier caliper was used to measure the colony diameter, and the mycelial growth inhibition rate was calculated according to the formula.

[0047] Hyphal growth inhibition rate (%) = (control colony diameter - treated colony diameter) / control colony diameter × 100%

[0048] (II) Test results

[0049] Figure 1 Table 1 shows the inhibitory effect of Bio-AgNPs on the hyphal growth of Botrytis cinerea. As Figure 1 shown in Table 1, as the concentration of Bio-AgNPs increases, its inhibitory effect on hyphal growth gradually increases, and the hyphal growth inhibition rate gradually increases. When the concentration of Bio-AgNPs is 1 μg / mL, the hyphal growth inhibition rate of Botrytis cinerea is only 4.08%, with no significant inhibitory effect; while when the concentration of Bio-AgNPs is 100 μg / mL, the hyphal growth inhibition rate of Botrytis cinerea is 100%.

[0050] Table 1

[0051]

[0052]

[0053] Note: The data in the table are mean ± standard deviation. Letters after the data in the same column indicate significant differences at the p < 0.05 level after one-way ANOVA and Duncan's multiple comparison test to verify the differences between groups.

[0054] Example 3 Effect of biosilver nanoparticles (Bio-AgNPs) synthesized based on Bacillus velezensis on tomato seed germination

[0055] (I) The method is as follows:

[0056] The Bio-AgNPs stock solution prepared in Example 1 was diluted with sterile water to concentrations of 1 μg / mL, 5 μg / mL, 10 μg / mL, 20 μg / mL, 40 μg / mL, and 80 μg / mL, respectively. The filter paper in the petri dish was moistened with 6 mL of Bio-AgNPs at different concentrations, and the control group was treated with sterile water. 30 plump tomato seeds were placed in each petri dish and cultured in a light incubator with a light intensity of 4000 lx, a light time of 16 h, and a temperature of 28°C. On the 7th day, the germination number, root length, shoot length, and number of lateral roots of the seeds were recorded and measured, and the germination potential and germination rate of the seeds were calculated according to the relevant formulas.

[0057] Germination potential (%) = (number of germinated seeds at 3 d / total number of tested seeds) × 100%

[0058] Germination rate (%) = (number of germinated seeds at 7 d / total number of tested seeds) × 100%

[0059] (2) Detection Results

[0060] Figure 2 And Table 2 show the results of the effects of Bio-AgNPs on the germination of tomato seeds. As Figure 2 shown in and Table 2, the root length and shoot length of tomato seeds in the control group were 3.69 cm and 2.88 cm, respectively. When treated with 1 μg / mL, 5 μg / mL, 10 μg / mL, and 20 μg / mL of Bio-AgNPs, the shoot length increased significantly by 34.38%, 18.75%, 13.19%, and 10.76%; when treated with 1 μg / mL, 5 μg / mL, 10 μg / mL, and 20 μg / mL of Bio-AgNPs, the root length of the seeds increased significantly by 19.78%, 44.72%, 42.28%, and 20.05%; when treated with 5 μg / mL, 10 μg / mL, 20 μg / mL, and 40 μg / mL of Bio-AgNPs, the number of lateral roots of the seeds increased significantly by 2.35, 1.76, 1.53, and 2.76. However, when treated with 80 μg / mL of Bio-AgNPs, there were no signs of seed germination, probably because the high concentration of Bio-AgNPs was toxic to the seeds. The above results indicate that Bio-AgNPs at concentrations of 1 μg / mL, 5 μg / mL, 10 μg / mL, 20 μg / mL, and 40 μg / mL can improve the relevant indexes of tomato seed germination and have the effect of promoting tomato seed germination.

[0061] Table 2

[0062]

[0063]

[0064] Note: The data in the table are mean ± standard deviation. Letters after the data in the same column indicate significant differences at the p < 0.05 level after one-way ANOVA and Duncan's multiple comparison test to verify the differences between groups.

[0065] Example 4 Effects of Biosilver Nanoparticles (Bio-AgNPs) Synthesized Based on Bacillus velezensis on the Growth of Tomato Seedlings

[0066] (1) The method is as follows:

[0067] The stock solution of Bio-AgNPs prepared in Example 1 was diluted with sterile water to concentrations of 20 μg / mL and 40 μg / mL. Tomato seeds were treated with Bio-AgNPs at a concentration of 80 μg / mL, and there were no signs of germination in the tomato seeds at all. Considering the toxicity of Bio-AgNPs and combining with the results of the mycelial growth inhibition experiment, Bio-AgNPs at concentrations of 20 μg / mL and 40 μg / mL were selected for subsequent experiments. When the tomato plants grew to the four-leaf stage, 20 μg / mL and 40 μg / mL of Bio-AgNPs were evenly sprayed on both the front and back sides of the tomato leaves. At 14 d after the treatment, plant height, stem diameter, aboveground fresh weight, aboveground dry weight, underground fresh weight, underground dry weight, and root length were measured.

[0068] (II) Detection Results

[0069] Figure 3 Table 3 shows the results of the effects of Bio-AgNPs on the growth of tomato seedlings. As Figure 3 shown in Table 3, the underground dry weight of the tomato plants in the control group (CK) was 0.28 g. Compared with the control group (CK), the underground dry weight of the tomato plants treated with Bio-AgNPs increased significantly. Among them, in the Bio-AgNPs group with a concentration of 40 μg / mL (Bio-40), it increased significantly by 28.57%. In addition, in terms of the root length of the tomato plants, the root length of the tomato plants in the control group (CK) was 16.82 cm. After treatment with Bio-AgNPs, the root length increased significantly. Among them, in the Bio-AgNPs group with a concentration of 20 μg / mL (Bio-20), the root length increased significantly by 8.20%. There were no significant differences in the growth indexes of the other treatment groups, including the fresh weight and dry weight of the aboveground part, the fresh weight of the underground part, plant height, and stem diameter, compared with the control group (CK). The above results indicate that 40 μg / mL and 20 μg / mL of Bio-AgNPs can promote the growth of tomato plants by increasing the underground dry weight and root length, respectively.

[0070] Table 3

[0071]

[0072] Note: CK: control group; Lnu-21-CFS: cell-free supernatant of Bacillus velezensis Lnu-21; Bio-20: 20 μg / mL Bio-AgNPs; Bio-40: 40 μg / mL Bio-AgNPs; Chem-40: 40 μg / mL Chem-AgNPs. The data in the table are mean ± standard deviation. The letters after the data in the same column indicate significant differences at the p < 0.05 level after being verified by one-way ANOVA and tested by Duncan's multiple comparison method.

[0073] Control Effect of Biosynthesized Silver Nanoparticles (Bio-AgNPs) Based on Bacillus velezensis on Botrytis cinerea of Tomato Fruit

[0074] (I) The method is as follows:

[0075] Tomato fruits were treated in 0.1% sodium hypochlorite solution for 2 min and then rinsed with water and reserved. The fruits were randomly grouped and soaked in water (control group) and 1 μg / mL, 5 μg / mL, 10 μg / mL, 20 μg / mL, 40 μg / mL Bio-AgNPs solutions for 10 min respectively. Then, wounds with uniform size and depth (diameter 0.5 mm, depth 0.5 mm) were punctured at the equatorial position of the fruits, and 0.6 mm×0.6 mm Botrytis cinerea mycelial discs were randomly pasted on the wounds. The treated tomato fruits were placed in a sterile fresh-keeping box and stored at a constant temperature of 22 °C. After 72 h, the lesion diameter was measured.

[0076] Lesion diameter = (transverse diameter of lesion + longitudinal diameter of lesion) / 2

[0077] (II) Detection results

[0078] As Figure 4 shown in and Table 4, compared with the control group (CK), the lesion diameters of the 10 μg / mL, 20 μg / mL, 40 μg / mL Bio-AgNPs treatment groups were all significantly reduced. Among them, the inhibitory effect of 40 μg / mL Bio-AgNPs was the best, and the lesion diameter was significantly reduced by 52.21%. The results showed that Bio-AgNPs had a significant inhibitory effect on Botrytis cinerea of tomato fruit.

[0079] Table 4

[0080]

[0081] Note: The data in the table are mean ± standard deviation. Letters after the data in the same column indicate significant differences at the p<0.05 level by Duncan's multiple comparison method after verification of inter-group differences by one-way analysis of variance.

[0082] Example 6 Control Effect of Biosynthesized Silver Nanoparticles (Bio-AgNPs) Based on Bacillus velezensis on Botrytis cinerea of Tomato Leaves

[0083] (I) The method is as follows:

[0084] When tomatoes grew to the four-leaf stage, the control effect experiment on leaves was carried out. The front and back sides of tomato leaves were evenly sprayed with 20 μg / mL and 40 μg / mL Bio-AgNPs. Six hours later, Botrytis cinerea spore suspension (1.0×10 7(cfu / mL). After 48 h of dark treatment at 22 °C, the plants were placed in a growth chamber with a day temperature of 28 °C, a night temperature of 12 °C, and a 12-h light cycle for 7 d. The disease index was investigated, and the control effect was calculated. A total of seven treatment groups were set up in the experiment:

[0085] CK: Only sprayed with clear water

[0086] BC: Only sprayed with a spore suspension of Botrytis cinerea (1.0×10 7 cfu / mL);

[0087] Lnu-21-CFS: First sprayed with the cell-free supernatant of Bacillus velezensis Lnu-21, and then sprayed with a spore suspension of Botrytis cinerea (1.0×10 7 cfu / mL) after 6 h;

[0088] Bio-20: First sprayed with 20 μg / mL Bio-AgNPs, and then sprayed with a spore suspension of Botrytis cinerea (1.0×10 7 cfu / mL) after 6 h;

[0089] Bio-40: First sprayed with 40 μg / mL Bio-AgNPs, and then sprayed with a spore suspension of Botrytis cinerea (1.0×10 7 cfu / mL) after 6 h;

[0090] Pro: First sprayed with the pesticide procymidone, and then sprayed with a spore suspension of Botrytis cinerea (1.0×10 7 cfu / mL) after 6 h;

[0091] Chem-40: First sprayed with 40 μg / mL chemical AgNPs, and then sprayed with a spore suspension of Botrytis cinerea (1.0×10 7 cfu / mL) after 6 h;

[0092] (II) Detection results

[0093] According to the national guidelines for field efficacy trials of pesticides, the disease index grading standard (Table 5) is as follows:

[0094] Table 5

[0095]

[0096] Disease index (%) = ∑(number of diseased leaves at each level × representative value at each level) / (total number of leaves × highest representative extreme value) × 100%

[0097] Control effect (%) = (disease index of the control group - disease index of the treatment group) / disease index of the control group × 100%

[0098] Figure 5 Table 6 shows the control effects of Bio-AgNPs on tomato plants. As Figure 5 shown, the control effects of pesticides and Bio-AgNPs are the best. Among them, the control effect of the pesticide on Botrytis cinerea of tomato leaves is 47.09%, and the control effects of 20 μg / mL Bio-AgNPs and 40 μg / mL Bio-AgNPs are 34.13% and 40.19% respectively, indicating that Bio-AgNPs can control Botrytis cinerea of tomato leaves.

[0099] Table 6

[0100]

[0101] Note: CK: control group; BC: inoculated only with pathogenic bacteria; Lnu-21-CFS: cell-free supernatant of Bacillus velezensis Lnu-21; Pro: pesticide procymidone; Bio-20: 20 μg / mL Bio-AgNPs; Bio-40: 40 μg / mL Bio-AgNPs; Chem-40: 40 μg / mL Chem-AgNPs. The data in the table are mean ± standard deviation. Letters after the data in the same column indicate significant differences at the p < 0.05 level after one-way ANOVA to verify the differences between groups and using Duncan's multiple comparison method.

Claims

1. Application of biosilver nanoparticles synthesized based on Bacillus velezensis in controlling tomato gray mold 2. The application according to claim 1, characterized in that, The biosilver nanoparticles synthesized based on Bacillus velezensis are used to inhibit the growth of Botrytis cinerea mycelia.

3. The application according to claim 1, characterized in that, The biosilver nanoparticles synthesized based on Bacillus velezensis are used to control tomato fruit gray mold.

4. The application according to claim 1, wherein The biosilver nanoparticles synthesized based on Bacillus velezensis are used to control tomato leaf gray mold.

5. The application according to claim 1, wherein The biosilver nanoparticles synthesized based on Bacillus velezensis are used to promote tomato seed germination.

6. The application according to claim 1, wherein The biosilver nanoparticles synthesized based on Bacillus velezensis are used to promote the growth of tomato seedlings.

7. The application according to any one of claims 1-6, characterized in that, The biosilver nanoparticles synthesized based on Bacillus velezensis are synthesized from Bacillus velezensis Lnu-21 with the preservation number of CGMCC NO.29565 and silver nitrate.

8. The application according to claim 7, wherein The preparation method of the biosilver nanoparticles synthesized based on Bacillus velezensis includes the following steps: Activation culture of the strain: Bacillus velezensis Lnu-21 with the preservation number of CGMCC NO.29565 is placed on a nitrate solid medium for culture. Single colonies are picked and added to a nitrate liquid medium and cultured at 37 °C for 45 h - 50 h to obtain a Bacillus velezensis culture solution. Preparation of cell-free supernatant: The obtained Bacillus velezensis culture solution is centrifuged, and the centrifuged supernatant is filtered through a filter membrane with a diameter of 0.22 μm to obtain a Bacillus velezensis cell-free supernatant. Preparation of the biosilver nanoparticle stock solution: The obtained Bacillus velezensis cell-free supernatant and silver nitrate solution are co-cultured at 37 °C and 180 rpm for a reduction reaction for 45 h - 50 h to obtain a biosilver nanoparticle stock solution; the concentration of the silver nitrate solution is 4 mM - 6 mM, and by volume ratio, Bacillus velezensis cell-free supernatant: silver nitrate solution = (1 - 3):(7 - 9).

9. The application according to claim 7, characterized in that, The method is as follows: The biosilver nanoparticle stock solution synthesized based on Bacillus velezensis is formulated into a medicament with sterile water and sprayed on the fruits and leaves of tomatoes.

10. The application according to claim 9, wherein, In the medicament, the concentration of the biosilver nanoparticles synthesized based on Bacillus velezensis is 1 μg / mL - 100 μg / mL.

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