Agricultural composition of paenibacillus polymyxa and gallnut extract and application

Abstract

The invention belongs to the technical field of plant disease control, and particularly relates to an agricultural composition of paenibacillus polymyxa and gallnut extract and application. According to the invention, it is found for the first time that the gallnut extract has an inhibition effect on the growth of four different pathogenic bacteria, namely pseudomonas syringae pv. Syringae, pseudomonas syringae pv. Syringae, pear fire blight bacteria and xanthomonas citrus subspecies, and it is found that the gallnut extract has a synergistic effect on paenibacillus polymyxa; the invention also provides an agricultural composition composed of the gallnut extract and paenibacillus polymyxa, and the agricultural composition has an inhibition effect on the growth of pseudomonas syringae pv. Syringae, pseudomonas syringae pv. Syringae, pear fire blight bacteria and xanthomonas citrus subspecies, and can be applied to the field of plant disease control.

Description

Technical Field

[0001] The invention belongs to the technical field of plant disease prevention and control, and particularly relates to an agricultural composition of Paenibacillus polymyxa and gallnut extract and application thereof. Background Art

[0002] Diseases such as bacterial canker of kiwifruit caused by Pseudomonas syringae pv.actinidiae, bacterial spot of tomato caused by Pseudomonas syringae pv.tomato, fire blight of amylovory caused by Erwinia amylovory infecting Rosaceae plants such as pear, apple and hawthorn, and citrus canker caused by Xanthomonas citri subsp.citri seriously restrict the sustainable development of the above-mentioned fruit and vegetable industries.

[0003] Biological control has shown obvious advantages in plant disease control due to its high safety and good environmental protection. Biocontrol bacteria have become the mainstream direction of biological control because of their antagonistic effect on pathogenic bacteria. However, the control effect of using only biocontrol agents is limited, and the potential of biocontrol cannot be maximized, which is not conducive to application and promotion. Chinese herbal medicine extracts are natural, relatively abundant in resources, and can be naturally degraded. They are increasingly widely used in the fields of antibacterial and antibacterial. Therefore, screening Chinese herbal medicine extracts and compounding them with biocontrol bacteria with control effects to achieve biocontrol bacteria synergy can maximize the potential of biocontrol, provide new ideas for plant disease control, and have broad development prospects.

[0004] At present, there is no literature report on the application of compounding Bacillus polymyxa with plant extracts in disease prevention and control, and there is no literature report on the application of compounding Chinese herbal medicine extracts with Bacillus polymyxa in inhibiting Pseudomonas syringae pv.actinidiae, Pseudomonas syringae pv.tomato, Erwinia amylovory and Xanthomonas citri subsp.citri. Without the creative knowledge of compounding synergistic data verification, it is difficult for ordinary technicians in this field to know that compounding can effectively prevent and treat diseases.

[0005] What kind of antibacterial effect will it produce? Summary of the invention

[0006] In order to overcome the above-mentioned problems in the prior art, the present invention provides an agricultural composition of Paenibacillus polymyxa and Galla chinensis extract and its application.

[0007] The inventors of the present patent application obtained the gallnut extract by screening, and further explored an agricultural composition of Paenibacillus polymyxa and gallnut extract through in-depth research.

[0008] It is easy for ordinary technicians in this field to know that the biocontrol effect can be improved by compounding with a single bacterial agent and avoiding the problem of a single mechanism of action of a single bacterial agent. Multiple bacterial agents are often used in combination. There are few literature reports on compounding Chinese herbal medicine extracts with bacterial agents to improve the biocontrol effect. Due to the unclear mechanism of action of Chinese herbal medicine extracts, it is difficult to predict whether the control effect after combining them with bacterial agents or using them together is synergistic. After in-depth experimental research, the inventors found that according to the comprehensive effect evaluation of the antibacterial effect, the agricultural composition of the polymyxa bacillus and the gallnut extract of the present invention showed good antibacterial effect on Pseudomonas syringae pv. actinidiae, Pseudomonas syringae pv. tomato, Erwinia amylovory and Xanthomonas citri subsp. citri, and the antibacterial effect of the gallnut extract after compounding with polymyxa bacillus was better than that of the gallnut extract or the single agent of polymyxa bacillus.

[0009] Furthermore, the deposit information of the Paenibacillus polymyxa in the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract provided by the present invention is as follows:

[0010] Taxonomic nomenclature: Paenibacillus polymyxa YLC1;

[0011] Deposit date: March 14, 2022;

[0012] Depository: General Microbiology Center, China Microbiological Culture Collection Administration;

[0013] Address of the depository: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing;

[0014] Deposit number: CGMCC No.24524; this strain has been disclosed in CN114591876A.

[0015] Further, the active ingredients of the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract consist of component A and component B;

[0016] The component A is Paenibacillus polymyxa, the fermentation liquid of Paenibacillus polymyxa, or a mixture of Paenibacillus polymyxa cells and the fermentation liquid;

[0017] The component B is a gallnut extract.

[0018] Furthermore, in terms of mL:mg, the volume mass ratio of component A to component B of the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract is 1:50-900.

[0019] Furthermore, the gallnut extract of the agricultural composition of Paenibacillus polymyxa and gallnut extract is an ethanol extract of gallnut.

[0020] Furthermore, the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract is used for plant disease prevention and control.

[0021] Furthermore, the agricultural composition of Bacillus polymyxa and gallnut extract is applied to plant diseases caused by at least one of Pseudomonas syringae pv.actinidiae, Pseudomonas syringae pv.tomato, Erwinia amylovory and Xanthomonas citri subsp.citri.

[0022] Furthermore, the gallnut extract is used to enhance at least one of Paenibacillus polymyxa, the fermentation broth of Paenibacillus polymyxa, or a mixture of Paenibacillus polymyxa cells and the fermentation broth in the prevention and control of plant diseases.

[0023] Furthermore, the mass volume ratio of the gallnut extract to at least one of Bacillus polymyxa, the fermentation broth of Bacillus polymyxa, or the mixture of Bacillus polymyxa cells and the fermentation broth is 400:1 in mg:mL; the pathogens of plant diseases are selected from at least one of Pseudomonas syringaepv.actinidiae, Pseudomonas syringae pv.tomato, Erwinia amylovory and Xanthomonas citrisubsp.citri.

[0024] Based on the inspiration or ideas of the technical solution of the present invention, the objects of use of the compound biocontrol agent can be further expanded to other pathogenic variants of Pseudomonas syringae and their hosts.

[0025] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0026] The present invention firstly discovered that the gallnut extract has an effect on the pathogenicity of Pseudomonas syringae pv. kiwifruit

[0027] It has an inhibitory effect on Pseudomonas syringae pv.actinidiae, Pseudomonas syringae pv.tomato, Erwinia amylovory and Xanthomonas citri subsp.citri. On this basis, after the gallnut extract is mixed with Paenibacillus polymyxa, the present invention has a significant inhibitory effect on Pseudomonas syringae pv.actinidiae, Pseudomonas syringaepv.tomato, Erwinia amylovory and Xanthomonas citri subsp.citri, and the antibacterial effect is better than that of a single dose when the mass volume ratio of the gallnut extract to Paenibacillus polymyxa is 400:1 in mg:mL. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a picture of the in-dish morphology of the Paenibacillus polymyxa YLC strain.

[0029] Figure 2 This is a graph showing the antibacterial effect of Paenibacillus polymyxa YLC fermentation broth on four pathogens in a dish.

[0030] Figure 3 This is a graph showing the antibacterial effect of different concentrations of gallnut extract on four pathogens in a dish.

[0031] Figure 4 This is a graph showing the antibacterial effect of different proportions of compound biocontrol agents on four pathogens in a dish.

[0032] Figure 5 This is a diagram showing the antibacterial effect of a compound biocontrol agent on plant diseases from different sources.

[0033] Figure 6 This is a graph showing the antibacterial effect of the compound biocontrol agent on M228 on detached kiwifruit leaves. DETAILED DESCRIPTION

[0034] The technical scheme of the present invention is described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The experimental methods and detection methods described in each embodiment are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0035] Example 1

[0036] This example is about the culture of Paenibacillus polymyxa YLC1 strain.

[0037] Prepare LB solid culture medium plates with 1.5% agar: weigh 10 g of tryptone, 5 g of yeast powder, 10 g of NaCl, and 15 g of agar powder, mix with 1 L of distilled water, and sterilize in a high-pressure steam autoclave (121°C, 20 min). Pour the sterilized culture medium onto the plate and wait for it to solidify before use.

[0038] Cultivation of Paenibacillus polymyxa YLC1 strain: Inoculate the Paenibacillus polymyxa YLC1 strain on the above-mentioned 1.5% agar LB solid medium and incubate at 28°C for 24-48 hours for activation. After activation, pick a single colony and inoculate it on a new plate for secondary activation, and incubate it at 28°C for 24-48 hours to finally obtain a plate with a single colony. Figure 1 As shown, Paenibacillus polymyxa YLC1 appears as milky white, opaque, irregularly round colonies with smooth and flat surfaces and uneven edges on LB solid culture medium.

[0039] Example 2

[0040] This example is a bacteriostasis test of the fermentation broth of Paenibacillus polymyxa YLC1 strain in a dish.

[0041] In this example, four pathogenic bacteria, M228: a highly pathogenic strain of Pseuomonas syringae pv.actinidae; DC3000: a highly pathogenic strain of Pseudomonas syringae pv.tomato; 4-1-8: a strain of Erwinia amylovory; and YXGJ: a strain of Xanthomonas citri subsp.citri, were subjected to an in-dish antibacterial test. The specific test is as follows:

[0042] Preparation of sterile fermentation broth of Paenibacillus polymyxa YLC1: Pick a single colony of Paenibacillus polymyxa YLC into liquid LB medium and culture at 28°C in a shake flask until OD 600 =1.0, and obtain Paenibacillus polymyxa YLC fermentation liquid. The Paenibacillus polymyxa YLC fermentation liquid is filtered three times with a 0.22 μm filter membrane to obtain a Paenibacillus polymyxa YLC sterile fermentation liquid.

[0043] Preparation of pathogenic bacteria liquid: Streak and activate the culture of M228, DC3000, 4-1-8 and YXGJ on 1.5% agar LB solid medium plates, pick out activated single colonies and inoculate them into liquid LB medium, and culture them in bottles at 28℃ until OD 600 =1.0.

[0044] Preparation of bacterial plates: Add the bacterial solution prepared above to LB solid medium containing 1% agar at 40°C at a content of 5%, mix well and pour onto plates. After cooling, M228, DC3000, 4-1-8 and YXGJ bacterial plates were obtained.

[0045] Preparation of liquid LB medium: weigh 10 g of tryptone, 5 g of yeast powder, and 10 g of NaCl, mix with 1 L of distilled water, and sterilize in a high-pressure steam autoclave (121°C, 20 min). Cool the sterilized medium to obtain liquid LB medium.

[0046] Prepare LB solid culture medium plate with 1% agar: weigh 10g of tryptone, 5g of yeast powder, 10g of NaCl, and 10g of agar powder, mix with 1L of distilled water, and sterilize in a high-pressure steam sterilizer (121°C, 20min). Prepare LB solid culture medium liquid, pour the LB solid culture medium liquid into the plate on a sterile operating table, and wait for the medium in the plate to solidify to obtain 1% agar LB solid culture medium plate.

[0047] Bacteriostatic test of Paenibacillus polymyxa YLC1 strain fermentation broth in dishes:

[0048] Use a sterile puncher to punch holes on M228, DC3000, 4-1-8 and YXGJ bacteria-containing plates, and drop 20 μL of Paenibacillus polymyxa YLC1 sterile fermentation liquid into each hole. Place the plates in a 28°C incubator and culture them upright for 24 hours. Use the cross method to measure the diameter of the inhibition zone. Set up 3 replicates and take the average value. Figure 2 As shown, the diameter of the inhibition zone of Paenibacillus polymyxa YLC1 against four pathogens, M228, DC3000, 4-1-8 and YXGJ, is 11-15 mm, indicating that Paenibacillus polymyxa YLC1 strain has antagonistic effects on M228, DC3000, 4-1-8 and YXGJ.

[0049] Example 3

[0050] This example is for preparing Galla chinensis extracts of different solubility.

[0051] Weigh 30 g of gallnut powder into a conical flask, add 95% ethanol solution until it is submerged, extract at room temperature for 2 days, place it on a shaker at 200 rpm / min for 18 hours, filter the gallnut ethanol mixture to obtain the first extraction filtrate, and then repeat the above method for 2 times with the gallnut residue. After mixing the 3 extraction filtrates, place them in a rotary evaporator, heat them in a water bath at 85°C, condense and reflux to extract them, and rotary evaporate them in the rotary evaporator. After rotary evaporation, the residual liquid is transferred to a 50 mL centrifuge tube and dried in an oven to a paste.

[0052] Different masses of paste gallnut were weighed respectively and mixed with sterile water to prepare 25 mg / mL gallnut extract, 50 mg / mL gallnut extract, 100 mg / mL gallnut extract, 200 mg / mL gallnut extract and 300 mg / mL gallnut extract.

[0053] Example 4

[0054] This example is a bacteriostasis test of the Chinese nut extract.

[0055] Use a sterile puncher to evenly punch holes on M228, DC3000, 4-1-8 and YXGJ bacteria-containing plates, and drop 20 μL of 25 mg / mL, 50 mg / mL, 100 mg / mL, 200 mg / mL, and 300 mg / mL gallnut extracts, respectively. Place in a 28°C incubator and culture for 12 hours. Repeat the above test three times, and use the cross method to measure the diameter of the inhibition zone.

[0056] like Figure 3As shown, different concentrations of gallnut extracts have antibacterial effects on four pathogens, M228, DC3000, 4-1-8 and YXGJ, but there are differences in the antibacterial effects on different pathogens. The maximum diameter of the inhibition zone of gallnut extract on M228 is 28mm; the maximum diameter of the inhibition zone on DC3000 is 28mm; the maximum diameter of the inhibition zone on 4-1-8 is 26mm; and the maximum diameter of the inhibition zone on YXGJ is 26mm.

[0057] like Figure 3 As shown, the statistical results of the antagonistic effect showed that the diameter of the inhibition zone of the DC3000 pathogen was significantly different when the concentration of the gallnut extract was 300 mg / mL and 200 mg / mL, indicating that the antibacterial effect of the gallnut was best when the concentration was 300 mg / mL for DC3000. There was no significant difference in the antagonistic effect of the gallnut extract concentrations of 200 mg / mL and 300 mg / mL on the three pathogens M228, 4-1-8 and YXGJ. From the perspective of cost, the optimal antibacterial concentration of the gallnut extract for the three pathogens M228, 4-1-8 and YXGJ was 200 mg / mL.

[0058] Example 5

[0059] This example provides the preparation and antibacterial test of an agricultural composition of Paenibacillus polymyxa and Galla chinensis extract.

[0060] Preparation of an agricultural composition of Paenibacillus polymyxa and gallnut extract: mixing the sterile fermentation liquid of Paenibacillus polymyxa YLC1 with 200 mg / mL gallnut extract in a volume ratio of 3:1, 2:1, 1:1, 1:2, 1:3 to prepare an agricultural composition of Paenibacillus polymyxa and gallnut extract with the same total volume.

[0061] Antibacterial test: 20 μL of the agricultural composition of Bacillus polymyxa and Galla chinensis extract was added dropwise to the punched bacteria-containing plate wells of M228, DC3000, 4-1-8 and YXGJ, and cultured at 28°C for 12 h. The experiment was repeated three times, and the diameter of the inhibition zone was measured by the cross method.

[0062] like Figure 4 As shown, the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract prepared in this example has an inhibition zone diameter of up to 30 mm for M228; a maximum inhibition zone diameter of 28.5 mm for DC3000; a maximum inhibition zone diameter of 30 mm for 4-1-8; and a maximum inhibition zone diameter of 30 mm for YXGJ.

[0063] like Figure 4As shown in the figure, the statistical results of the antagonistic effect showed that the volume ratio of Paenibacillus polymyxaYCL1 to Galla chinensis extract was 3:1, 2:1, 1:1, 1:2, and 1:3, which had an antibacterial effect on four pathogens, M228, DC3000, 4-1-8, and YXGJ; the volume ratio of Paenibacillus polymyxaYCL1 to Galla chinensis extract was 1:3 and 1:2, which had a significant difference in the inhibitory effect on the M228 pathogen, indicating that the optimal mixing volume ratio for the M228 pathogen was 1:2; There was no significant difference in the antagonistic effect of YCL1 and gallnut extract at a volume ratio of 1:3 and 1:2 against DC3000, 4-1-8 and YXGJ pathogens, suggesting that the preferred mixed volume ratio for DC3000, 4-1-8 and YXGJ is 1:2 or 1:3.

[0064] Example 6

[0065] This example is a test to evaluate the synergistic effect of the combination of Paenibacillus polymyxa YCL1 sterile fermentation broth and Galla chinensis extract.

[0066] Antibacterial test: When C1 (Paenibacillus polymyxa YLC1 fermentation broth) and C2 (200 mg / mL gallnut extract) were used alone, the drop volume was added according to the ratio of Paenibacillus polymyxa to the gallnut extract in the agricultural composition, and the volume ratio of Paenibacillus polymyxa to the gallnut extract in the agricultural composition was 1:2.

[0067] 20 μL of the agricultural composition of Paenibacillus polymyxa and gallnut extract and the calculated corresponding volumes of C1 and C2 were added dropwise to the punched bacteria-containing plate wells of M228, DC3000, 4-1-8 and YXGJ, respectively, and cultured at 28°C for 12 h. The experiment was repeated three times. The Growing method was used to determine the synergistic effect of the agricultural composition of Paenibacillus polymyxa YCL1-galnut. The determination formula and method are as follows:

[0068] Cexp=C1+C2(1-C1).

[0069] Among them, Cexp is the expected level of inhibition of the combined biocontrol agent on pathogens (theoretical inhibition rate); C1 and C2 are the actual inhibition rates of pathogens when a single agent is used alone; Cobs is the actual inhibition rate of the combined biocontrol agent on pathogens measured in the experiment.

[0070] If Cobs = Cexp, it indicates that each component in the biocontrol compound preparation exhibits independent effects;

[0071] If Cobs > Cexp, it indicates that each component in the biocontrol compound preparation exhibits synergistic effects;

[0072] If Cobs < Cexp, it indicates that each component in the biocontrol compound preparation exhibits antagonistic effects.

[0073] Calculate the inhibition rate of the antibacterial substance against bacteria:

[0074] Inhibition rate = [(diameter of inhibition zone - diameter of colony) / diameter of inhibition zone] × 100%. Among them, the diameter of the inhibition zone refers to the diameter of the inhibition zone, and the diameter of the colony refers to the diameter of the colony formed by bacteria on the agar plate. In this example, the fermentation broth of Paenibacillus polymyxa YCL1 was dropped into the holes on the agar plate with a sterile puncher, so the diameter of the colony is the diameter of the puncher, which was measured to be 0.6 cm.

[0075] The evaluation test results of the synergistic effect of the fermentation broth of Paenibacillus polymyxa YCL1 and the extract of Chinese gallnut are shown in Table 1. The results show that the combination of the fermentation broth of Paenibacillus polymyxa YCL1 and the extract of Chinese gallnut has a synergistic effect on M228, DC3000, 4-1-8, and YXGJ.

[0076] Table 1 Evaluation results of the synergistic effect of the sterile fermentation broth of Paenibacillus polymyxa YCL1 and the extract of Chinese gallnut

[0077] Germs C1 average antibacterial rate C2 average antibacterial rate Average Cexp Average Cobs Is it effective? M228 0.2 0.52 0.61 0.80 yes DC3000 0.18 0.52 0.60 0.78 yes 4-1-8 0.15 0.49 0.57 0.80 yes YJ 0.15 0.51 0.58 0.78 yes

[0078] Example 7

[0079] This example is an in-dish antibacterial test of the Paenibacillus polymyxa YCL1 - Chinese gallnut agricultural composition against plant pathogens from different sources

[0080] Sources and numbers of pathogenic bacteria: In this example, the pathogenic bacteria are Pseudomonas syringae pv. actinidiae, and their sources and numbers are as follows: M228 from Yangling, Shaanxi; G25 and ML2 from Hubei and Guizhou; H32 from Xixia, Henan; N7 from Fenghuang, Hunan.

[0081] Prepare the Pseudomonas syringae pv. actinidiae bacterial solution: Streak and activate different strains of Pseudomonas syringae pv. actinidiae from different sources on LB plates respectively, and pick the activated single colonies and inoculate them into liquid LB medium, and culture them in a shaker at 28°C until OD 600=1.0.

[0082] Prepare bacterial plates: add the bacterial solution prepared above to LB solid medium with 1% agar at about 40°C at a content of 5%, mix well and pour into plates. After cooling, obtain bacterial plates of G25, H32, ML2 and N7, and punch a hole in the center with a cork puncher.

[0083] 20 μL of the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract was dropped into the center of the bacteria-containing plate prepared above, respectively, and cultured at 28° C. for 24 h. The diameter of the inhibition zone was measured by the cross method.

[0084] The experimental results are as follows Figure 5 As shown, the diameter of the inhibition zone is between 28 mm and 34 mm, indicating that the agricultural composition of Bacillus polymyxa and Galla chinensis extract has antagonistic effects on plant pathogens from different sources and has good biocontrol potential.

[0085] Example 8

[0086] This example is a test on the antibacterial activity of the agricultural composition of Paenibacillus polymyxa and Galla chinensis extract on M228 on detached kiwifruit leaves.

[0087] Healthy kiwifruit leaves were collected, and the surface dust was washed off with sterile water. They were then soaked in 6% sodium hypochlorite solution for 5 minutes and then washed with sterile water until there was no pungent smell. The washed kiwifruit leaves were air-dried and leaf discs were made with a sterilized 1.6 cm diameter puncher, avoiding the main vein of the leaf when punching.

[0088] The vacuum penetration non-injury inoculation method was used for testing, and the vacuum penetration conditions were 0.1MPa and 30s. The experiment was divided into treatment a (negative control), treatment b (only penetration of M228 bacterial solution) and treatment c (experimental group).

[0089] The details are as follows:

[0090] Reagent preparation: Streak out M228 on LB plate to activate the culture, pick out the activated single colony and inoculate it into liquid LB medium, shake and culture at 28℃ until OD 600 =0.1, then add 80 μL OD 600 =0.1 to prepare a 500-fold diluted M228 bacterial solution.

[0091] A 0.8% water agar medium was prepared by conventional methods, and a 0.8% water agar medium plate was prepared.

[0092] Antibacterial test:

[0093] Treatment a: Infiltrate leaf discs with sterile water.

[0094] Treatment b: Place the leaf disk at OD600 = 0.1 diluted 500 times of M228 bacterial solution and vacuum infiltrated.

[0095] Treatment c: 80 μL of the agricultural composition of Paenibacillus polymyxa YCL1 and Galla chinensis extract in a volume ratio of 1:2 was added to 40 mL of sterile water and then added to the leaf disc for vacuum infiltration. After 12 hours, the OD 600 = 0.1 diluted 500 times of M228 bacterial solution.

[0096] After infiltration, each treatment group was washed three times with sterile water and then placed on a 0.8% water agar medium plate prepared in advance and cultured at 16°C for 3 days. The results were recorded by photographing.

[0097] The test results are as follows Figure 6 As shown, the lesion area of ​​treatment c is significantly smaller than that of treatment b, indicating that the agricultural composition with a volume mass ratio of Paenibacillus polymyxa YCL1 to Galla chinensis extract of 1:400 in mL:mg has a good preventive effect on further infection of kiwifruit bacterial canker on the leaves.

Claims

1. An agricultural composition of Paenibacillus polymyxa and Galla chinensis extract, characterized in that: The active ingredients of the agricultural composition are composed of component A and component B; The component A is Paenibacillus polymyxa, the fermentation liquid of Paenibacillus polymyxa, or a mixture of Paenibacillus polymyxa cells and the fermentation liquid; The component B is a gallnut extract.

2. The agricultural composition according to claim 1, characterized in that In terms of mL:mg, the mass volume ratio of the component A to the component B is 1:50-900.

3. The agricultural composition according to claim 1, characterized in that The gallnut extract is an ethanol extract of gallnut.

4. The agricultural composition according to claim 1, characterized in that The deposit number of the polymyxa bacillus is CGMCC No.24524.

5. Use of the agricultural composition according to any one of claims 1 to 4 in preventing and controlling plant diseases.

6. The use according to claim 5, characterized in that: The pathogen of the plant disease is selected from at least one of Pseudomonas syringae pv. actinidiae, Pseudomonas syringae pv. tomato, Erwinia amylovory and Xanthomonas citri subsp. citri.

7. Use of a gallnut extract in enhancing at least one of Paenibacillus polymyxa, a fermentation broth of Paenibacillus polymyxa, or a mixture of Paenibacillus polymyxa and a fermentation broth in plant disease control.

8. The use according to claim 7, characterized in that: The deposit number of the polymyxa bacillus is CGMCC No.24524.

9. The use according to claim 7, characterized in that: The mass volume ratio of the Galla chinensis extract to at least one of Paenibacillus polymyxa, the fermentation broth of Paenibacillus polymyxa, or the mixture of Paenibacillus polymyxa cells and the fermentation broth is 400:1 in mg:mL.

10. The use according to claim 7, characterized in that: The pathogen of the plant disease is selected from at least one of Pseudomonas syringae pv. actinidiae, Pseudomonas syringae pv. tomato, Erwinia amylovory and Xanthomonas citri subsp. citri.

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