A strain of Paenibacillus polymyxa and its application in the field of plant pathogen control

Abstract

The present invention relates to a strain of Paenibacillus polymyxa and its application in the field of plant pathogen control, belonging to the technical field of biocontrol microorganisms. At present, there are no effective prevention and control measures for ginger rot in Laiwu area of Shandong. In view of this situation, a strain of Paenibacillus polymyxa NBL-B13008 was screened in the present invention. This strain can synthesize 5-ALA and has good inhibitory effects on strains of various genera such as Enterobacter cloacae, Colletotrichum, Alternaria, and Fusarium. It has good application prospects when applied to the prevention and control of crop diseases including ginger rot.

Description

Technical Field

[0001] The present invention belongs to the technical field of biocontrol microorganisms, and particularly relates to a Paenibacillus polymyxa NBL-B13008, a bacterial agent of the strain, and its application in the field of plant pathogen control. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Ginger is a perennial herbaceous plant, which is planted in many regions of China and has very high edible, medicinal, and economic values. According to statistics, the annual global output of ginger is about 100,000 tons, and 80% of which comes from China. In China, the main ginger production areas are mainly concentrated in the central, southeastern to southwestern regions, and the planting area accounts for about 43.2% of the world. Among them, Shandong is the largest ginger planting area. The Laiwu area in Shandong is the main ginger production area, with an annual output of up to 500,000 tons.

[0004] Ginger is prone to various diseases and pests during the planting process, among which ginger soft rot occurs most severely. The general incidence rate in the field is 10%-20%, and it can reach more than 50% in severe cases. In the Laiwu ginger planting area, the inventor investigated and found that the incidence rate of ginger soft rot can reach more than 70%, causing serious economic losses. And because ginger soft rot is difficult to control, only the planting land can be continuously changed. At present, biological control is an efficient, non-toxic, green, and economic control scheme. However, there are few biocontrol bacteria applied to ginger soft rot at present, and the effect is not obvious. In view of the above research status, the inventor believes that clarifying the pathogen of ginger soft rot in the Laiwu area of Shandong and providing accurate biocontrol bacteria are of great significance for improving the economic benefits of the ginger planting industry. Summary of the Invention

[0005] In the present invention, disease samples were collected from ginger planting areas, and soil samples were also collected. Through pathogen isolation and biocontrol strain isolation, it was first determined that the main pathogen causing ginger rot in Laiwu area, Shandong Province, is Enterobacter cloacae. In order to provide a precise biocontrol bacterium for ginger pathogens in Laiwu area, Shandong Province, the present invention screened for antagonists against Enterobacter cloacae and obtained a strain of Paenibacillus polymyxa, named Paenibacillus polymyxa NBL-B13008, which has a good inhibitory effect on Enterobacter cloacae and can be used for the prevention and control of ginger rot. Further, the present invention studied the antibacterial properties of strain NBL-B13008. The research shows that the strain also has a good inhibitory effect on 9 other pathogens of different genera and species, and this strain is expected to achieve the control effect of various crop diseases as a biocontrol bacterium. Based on the above research conclusions, the present invention provides the following technical solutions:

[0006] In the first aspect, there is provided a Paenibacillus polymyxa NBL-B13008, which was deposited at the China Center for Type Culture Collection (CCTCC for short) on May 15, 2023. The address is: Wuhan University, Wuhan, China, and its biological deposit number is: CCTCC M 2023751.

[0007] The above strain was obtained by the punching method in the present invention. The morphological characteristics of the strain were observed under an oil immersion microscope as follows:

[0008] Colony characteristics: white, smooth surface, no luster, raised, uneven edges, irregular or nearly circular in shape, and sporulation was observed under the microscope. Bacterial body characteristics: rod-shaped, Gram-positive staining, and oval spores were produced.

[0009] The Paenibacillus polymyxa NBL-B13008 described in the first aspect has a 16S rDNA sequence as shown in SEQ ID NO:1.

[0010] The physiological and biochemical characteristics of the strain NBL-B13008 are as follows: Positive items: V-P, nitrate reduction, starch hydrolysis, gelatin liquefaction, citrate, D-xylose, L-arabinose, D-mannose, glucose, sucrose, tyrosine; Negative items: propionate, D-mannitol, D-arabinose, phenylalanine.

[0011] The suitable culture conditions are: 35-38 °C, corn starch medium. The composition of the corn starch medium is as follows: 20-30 g of corn starch, 13-17 g of soybean meal, 5-7 g of CaCO3, 4-6 g of (NH4)2SO4, pH 7.6-7.5, and add water to make up to 1 L.

[0012] There are quite a few reports on Paenibacillus polymyxa as a biocontrol agent in existing research, mainly focusing on the inhibitory effects of Paenibacillus polymyxa on plant pathogens such as Fusarium and Colletotrichum. The present invention believes that the Paenibacillus polymyxa reported currently usually only shows inhibitory effects on a single genus of pathogen, such as Colletotrichum or Fusarium, and there are very few reports that can achieve the control effects on multiple genera of pathogens simultaneously. It has been verified that the strain NBL-B13008 provided by the present invention has control effects on ten pathogens such as Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum, and Fusarium redolens. The above pathogens include Enterobacter, Colletotrichum, molds, Fusarium, and Alternaria, and there are significant genetic differences among the various pathogens. In addition, the above pathogens cover common pathogenic strains in the process of crop planting.

[0013] In addition, the research of the present invention has also confirmed that the strain NBL-B13008 can synthesize 5-aminolevulinic acid (5-ALA), and 5-ALA is a prefix compound of pyrrolidine (pyrrolidine is a substance that constitutes heme, cytochrome, and vitamin B12), and it is an essential substance for organisms to synthesize chlorophyll, heme, vitamin B12, etc. It is an important component commonly used in agriculture to increase photosynthetic efficiency and promote color change. Therefore, applying the strain NBL-B13008 to crop planting has considerable application prospects.

[0014] In a second aspect, a microbial agent is provided, and the microbial agent includes the Paenibacillus polymyxa NBL-B13008 described in the first aspect and / or the culture of the bacterium.

[0015] Preferably, the dosage form of the microbial agent in the second aspect can be a liquid microbial agent, a powder, or a granule; further, it is a water suspension, a dispersible oil suspension, a wettable powder, or a water-dispersible granule.

[0016] Preferably, the microbial agent further includes agriculturally acceptable excipients, and the agriculturally acceptable excipients are selected from one or more of a dispersant, a wetting agent, a disintegrant, a binder, an antifoaming agent, an antifreezing agent, a thickening agent, a filler, and a solvent. The present invention has no special restrictions on the sources of the agriculturally acceptable excipients, and generally commercially available products can be used.

[0017] In a third aspect, the application of the Paenibacillus polymyxa NBL-B13008 described in the first aspect and the microbial agent described in the second aspect in inhibiting plant pathogens is provided.

[0018] The above-mentioned plant pathogenic bacteria include, but are not limited to, one or more of Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens.

[0019] The application in inhibiting plant pathogenic bacteria, feasible application methods at least include the following aspects:

[0020] (1) Applied to crops infected with Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens, so as to prevent, improve or eliminate the disease state of the crops;

[0021] (2) Applied to prepare a medicament for inhibiting Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens;

[0022] (3) Applied to prepare a pesticide preparation for controlling crop diseases caused by Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens.

[0023] Fourthly, a biocontrol preparation is provided, which includes the Paenibacillus polymyxa NBL-B13008 described in the first aspect and / or the bacterial agent described in the second aspect.

[0024] The biocontrol preparation is preferably a liquid bacterial agent and is used by spraying it on the soil of the crop roots.

[0025] In a preferred embodiment, the bacterial agent is the fermentation broth of Paenibacillus polymyxa NBL-B13008. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0027] Figure 1 It is a microscopic photograph of Enterobacter cloacae described in Example 1;

[0028] Figure 2 It is a morphological diagram of Paenibacillus polymyxa NBL-B13008;

[0029] Among them, Figure 2 A is a colony diagram of Paenibacillus polymyxa NBL-B13008;

[0030] Figure 2Figure B is the cell diagram of Paenibacillus polymyxa NBL-B13008;

[0031] Figure 3 Figure is the bacteriostatic effect diagram of Paenibacillus polymyxa NBL-B13008;

[0032] Figure 4 Figure is the bacteriostatic effect diagram of Paenibacillus polymyxa NBL-B13008 against nine pathogenic bacteria;

[0033] Among them, Figure 4 Figure A is the bacteriostatic effect diagram against Colletotrichum camelliae;

[0034] Figure 4 Figure B is the bacteriostatic effect diagram against Colletotrichum gloeosporioides;

[0035] Figure 4 Figure C is the bacteriostatic effect diagram against Fusarium proliferatum;

[0036] Figure 4 Figure D is the bacteriostatic effect diagram against Fusarium redolens;

[0037] Figure 4 Figure E is the bacteriostatic effect diagram against Colletotrichum acutatum;

[0038] Figure 4 Figure F is the bacteriostatic effect diagram against Colletotrichum camelliae;

[0039] Figure 4 Figure G is the bacteriostatic effect diagram against Fusarium oxysporum;

[0040] Figure 4 Figure H is the bacteriostatic effect diagram against Alternaria cucumerina;

[0041] Figure 4 Figure I is the bacteriostatic effect diagram against Fusarium oxysporum f. sp. cucumerinum. Detailed implementation manners

[0042] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention belongs.

[0043] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0045] Example 1: Isolation, Screening and Identification of the Pathogen of Ginger Soft Rot

[0046] 1.1 Experimental Materials

[0047] Ginger soft rot samples; NA medium; NA slant; 75% alcohol; sterile water; etc.

[0048] 1.2 Experimental Methods

[0049] 1.2.1 Isolation of the Pathogen

[0050] Select ginger soft rot samples collected from Laiwu area, with a field incidence rate of up to 70%. Treat them by surface disinfection method. Rinse the ginger 3 times with sterile water, disinfect with 75% alcohol for 20 s, then pick the rotten part with a toothpick and streak it onto the NA medium, and culture it overnight at 30 °C. After picking single colonies and streaking 2 - 3 times, store them on the NA slant.

[0051] 1.2.2 Morphological and Molecular Identification of the Pathogen

[0052] Observe the morphology of the colonies on the NA medium. Pick the strains stored on the slant to make slides, perform crystal violet staining, observe the cell morphology under an oil microscope, and conduct molecular biological identification.

[0053] 1.2.3 Verification of Koch's Postulates for the Pathogen

[0054] Select healthy ginger tissue, cut it into pieces and disinfect with 75% alcohol. Place the ginger pieces in a petri dish lined with filter paper. Use an inoculation loop to inoculate the pathogen onto the ginger pieces, seal it and place it in an incubator at 25 °C. At the same time, use healthy ginger pieces as a control. After 7 d, observe the disease symptoms. Pick the diseased ginger pieces and conduct isolation, purification, morphological and molecular biological identification of the pathogen.

[0055] In addition, select healthy ginger potted plants, shake the pathogen, culture it at 180 rpm for 16 h. Use sterile water as a control, and irrigate each plant with 100 ml of 10 6 bacterial solution. After 7 d, observe the disease symptoms. Pick the diseased ginger pieces and conduct re - isolation, purification, morphological and molecular biological identification of the pathogen.

[0056] 1.3 Experimental Results

[0057] A total of 37 strains of bacteria were obtained from ginger rot samples using the tissue separation method. After verification by tissue block and potting back-inoculation, it was found that 12 strains showed varying degrees of pathogenic conditions after treatment. Finally, according to Koch's postulates, Enterobacter cloacae was determined as the pathogen causing ginger rot in Laiwu area of Shandong Province.

[0058] This strain appears round and without spores under the microscope, arranged individually ( Figure 1 ).

[0059] 1.4 Experimental conclusions

[0060] In this experiment, Enterobacter cloacae was first discovered as the pathogen causing ginger rot in Laiwu area of Shandong Province. Since previous control methods mainly targeted Ralstonia solanacearum, the control effect may not be ideal. Therefore, biocontrol bacteria against Enterobacter cloacae will be screened for the control of ginger rot.

[0061] Example 2: Screening and performance evaluation of biocontrol bacteria against the pathogen of ginger rot

[0062] 2.1 Experimental materials

[0063] Ginger rot diseased soil and healthy soil; 1.5% NA medium; NB medium; normal saline; glycerol, etc.

[0064] 2.2 Experimental methods

[0065] 2.2.1 Screening of biocontrol bacteria

[0066] Preparation of soil suspension: Take 1 g of soil and put it into a triangular flask containing 99 mL of sterile normal saline with glass beads, shake at room temperature for 30 min; Take 0.5 mL of soil suspension from the shaking flask and add it to a test tube containing 4.5 mL of sterile normal saline, shake and mix well, and dilute it successively in the test tube to 10 -3 to 10 -7 ; Take 100 μL of suspension from the corresponding gradient test tube, and evenly coat it on the NA medium with a spreader. Bacteria are cultured at 37 °C, and actinomycetes and fungi are cultured at 30 °C;

[0067] Select single colonies on the plate, purify them on a new plate, number them, and then store the bacteria on the NA slant and the actinomycetes on the Gao's slant.

[0068] 2.2.2 Screening of antagonistic bacteria

[0069] The hole punching method was used to screen for antagonistic bacteria against ginger rot. The specific experimental method is as follows: Perform shake plate counting on Enterobacter cloacae to determine that the concentration of the bacterial solution is 10 9 after shaking for 16 h, and perform gradient dilution on it to 10 6, Take 17.5 ml of the bacterial liquid and add it to 350 ml of NA medium. After cooling, use a hole punch to make holes on the NA medium. Place 6 kinds of bacterial liquids on each plate, 100 μL per hole, set 3 replicates, and use the plate without bacterial liquid as a blank control. Observe the antibacterial effect after culturing for one day, and screen the strain with the largest inhibition zone for subsequent experiments.

[0070] 2.2.2 Morphological and Molecular Identification of Antagonistic Bacteria

[0071] Observe the morphology of the colonies on the NA medium, pick the strains preserved on the slant to make slides, perform crystal violet staining, observe the cell morphology under an oil microscope, and conduct molecular biological identification.

[0072] 2.2.3 Antibacterial Performance Identification of Antagonistic Bacteria

[0073] The antibacterial performance of this antagonistic bacterium against 9 other pathogenic bacteria was identified by the plate confrontation method. The specific method was as follows: Inoculate the pathogenic bacteria at the center of the plate, and inoculate the biocontrol bacteria at the center between the pathogenic bacteria and the edge of the petri dish. The biocontrol bacteria were inoculated by the streaking method, with a length of 1 cm. Use the plate without inoculating the biocontrol bacteria as a control. Observe the test results after static culture at 25 °C for 7 d, and calculate the inhibition rate.

[0074] 2.2.4 Exploration of Fermentation Conditions of Antagonistic Bacteria

[0075] In the actual production of Paenibacillus polymyxa, the viable count after fermentation is relatively low. To solve this problem, in this example, the viable count was increased by improving the medium conditions and adjusting the temperature, etc.

[0076] This example tried to use the following media for culture:

[0077] Medium 1: NB medium (10 g of peptone, 3 g of beef extract powder, 5 g of sodium chloride, pH 7.2, made up to 1 L with water), 30 °C;

[0078] Medium 2: NB medium (10 g of peptone, 3 g of beef extract powder, 5 g of sodium chloride, pH 7.2, made up to 1 L with water), 37 °C;

[0079] Medium 3: Corn starch medium (25 g of corn starch, 15 g of soybean meal, 6 g of CaCO3, 5 g of (NH4)2SO4, pH 7, made up to 1 L with water), 30 °C;

[0080] Medium 4: Corn starch medium (25 g of corn starch, 15 g of soybean meal, 6 g of CaCO3, 5 g of (NH4)2SO4, pH 7, made up to 1 L with water), 37 °C.

[0081] According to the exploration of fermentation conditions, the fermentation broth under different conditions was counted, and the results were as follows:

[0082] Table 1

[0083]

[0084] Among the above media, Medium 4 has the best effect.

[0085] 2.2.5 Determination of the ability of antagonistic bacteria to produce 5-ALA

[0086] (1) Standard curve drawing

[0087] Prepare a 0.25 g / L 5-ALA stock solution with 5-ALA standard. Accurately weigh 0.0125 g of 5-ALA standard. Make up to 50 ml with distilled water in a volumetric flask. Prepare 5-ALA standard solutions with concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, and 50 mg / L using the stock solution. Pipette 2, 4, 6, 8, and 10 ml of the 5-ALA stock solution into volumetric flasks and make up to 50 ml. Each concentration needs to be repeated 3 times.

[0088] In a 10 ml stoppered centrifuge tube, add 2 ml of 5-ALA standard solution + 1 ml of acetate buffer + 0.5 ml of acetylacetone. Heat in a boiling water bath for 15 min, and cool naturally to room temperature. Take out 2 ml of the reaction solution from the centrifuge tube and add 2 ml of the color reagent. Carry out the color reaction for 30 min. Use water as the blank control and measure the absorbance OD at 554 nm. 554 .

[0089] (2) Determination of 5-ALA production

[0090] Activate the strain by shaking culture. Centrifuge the bacterial solution at 12000 rpm for 10 min. Take 2 ml of the supernatant + 1 ml of acetate buffer + 0.5 ml of acetylacetone, heat in a boiling water bath for 15 min, and cool naturally. Take 2 ml of the reaction solution + 2 ml of the color reagent, carry out the color reaction for 30 min. Use water as the blank control and measure the absorbance OD554 at 554 nm. This Paenibacillus polymyxa NBL-B13008 can produce 5-ALA, and its content was measured to be 8.2 mg / L after 3 days of shaking culture.

[0091] 2.3 Experimental results

[0092] 2.3.1 Experimental results

[0093] In this experiment, a Paenibacillus polymyxa NBL-B13008 with the best antibacterial performance against Enterobacter cloacae was obtained. After co-culturing for 1 day, the diameter of the antibacterial zone was 23 mm.

[0094] The colony morphology of the above-mentioned strain NBL-B13008 is as follows: white, smooth surface, no luster, raised, uneven edges, irregular or nearly circular in shape, and sporulation is observed under the microscope.

[0095] The 16S rDNA sequence of this strain is shown in SEQ ID NO: 1.

[0096] According to the determination, the strain NBL-B13008 has antibacterial properties against a variety of pathogenic bacteria, such as Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum, Fusarium redolens, etc. After culturing the NBL-B13008 in NB medium at 37 °C for 24 h, an antibacterial experiment was carried out on a PDA plate. After 7 days, the antibacterial effect was observed, and the antibacterial rate was calculated as shown in Table 1 below.

[0097] Table 1

[0098]

[0099] Example 3: Pot experiment on the control effect of Paenibacillus polymyxa on ginger soft rot

[0100] 3.1 Experimental materials

[0101] Ginger potted plants, fermentation broth of Paenibacillus polymyxa NBL-B13008, Enterobacter cloacae bacterial solution, etc.

[0102] 3.2 Experimental method

[0103] The healthy ginger with germinated buds was soaked in the fermentation broth of Paenibacillus polymyxa NBL-B13008 for 30 min. The experimental group was the strain NBL-B13008 fermented in corn starch medium, and three gradients of 10 5 , 10 6 , 10 7 were used for treatment. Each treatment group had 10 plants. After soaking, they were sown in sterile soil respectively. After sowing, 50 mL of Enterobacter cloacae bacterial solution was inoculated by irrigation per pot. After 7 days, 50 mL of the corresponding test bacterial solution was inoculated by irrigation per pot again. The control group was sterile water. After 30 days, the disease conditions of the ginger plants were counted. The disease conditions were classified as follows: Grade 0: The leaves are healthy and there is no withering; Grade 1: 0%-25% of the leaves show withering; Grade 2: 25%-50% of the leaves wither; Grade 3: 50%-75% of the leaves wither; Grade 4: 75%-100% of the leaves wither.

[0104] Disease index = ∑(number of diseased plants at each disease level in each treatment × disease level value) / (total number of plants × highest disease level)

[0105] Control effect (%) = [(disease index of the control group - disease index of the treatment group) / disease index of the control group] × 100

[0106] Table 2

[0107]

[0108] Table 3

[0109]

[0110] 3.3 Experimental results

[0111] The disease index of the experimental group using the fermentation broth of Paenibacillus polymyxa NBL-B13008 was lower than that of the control group, and the disease index decreased with the increase of the application concentration.

[0112] Example 4: Field experiment on the prevention and control effect of Paenibacillus polymyxa on ginger soft rot

[0113] 4.1 Experimental materials

[0114] Fermentation broth of Paenibacillus polymyxa NBL-B13008 (inoculated from the preserved slant into NB medium, preparing 50 ml of seed liquid, inoculating into a 20 L fermenter and fermenting for 24 h, with the viable count of 6 billion), ginger planting land.

[0115] 4.2 Experimental methods

[0116] Select the ginger planting land in Meiguanzhuang Village, Laiwu, Shandong. A total of 300 m 2 of experimental land was selected, and 3 treatment groups were set up. The farmland without applying microbial inoculant was used as the control group, and other management methods were the same. It was applied once before ginger planting, at the early growth stage, and at the middle growth stage. The treatment group used 3 L of the fermentation broth of strain NBL-B13008, diluted 500 times and flushed, three times. Disease investigation was carried out 80 days after the first treatment. The grading of the disease situation referred to Example 3.

[0117] Table 4

[0118]

[0119] 4.3 Experimental results

[0120] The experimental results show that the incidence of ginger after spraying the biocontrol bacteria decreased significantly, proving that Paenibacillus polymyxa has an inhibitory effect on ginger soft rot.

[0121] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. 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 Paenibacillus polymyxa ( Paenibacillus polymyxa ) NBL-B13008, which was deposited at the China Center for Type Culture Collection, abbreviated as CCTCC, located at Wuhan University, Wuhan, China on May 15, 2023, and its biological deposit number is: CCTCC M 2023751.

2. A bacterial agent, characterized in that, The microbial agent includes the Paenibacillus polymyxa ( Paenibacillus polymyxa ) NBL-B13008 and / or its culture.

3. The microbial agent according to claim 2, characterized in that, The dosage form of the bacterial agent is selected from water suspension, dispersible oil suspension, wettable powder or water dispersible granule.

4. The microbial agent according to claim 2, wherein The bacterial agent further includes pharmaceutically acceptable excipients, which are selected from one or more of dispersants, wetting agents, disintegrants, binders, defoamers, antifreezing agents, thickeners, fillers and solvents.

5. Use of the Paenibacillus polymyxa ( Paenibacillus polymyxa ) NBL-B13008 or the bacterial agent according to any one of claims 2 to 4 in inhibiting plant pathogenic bacteria, characterized in that The plant pathogenic bacteria are selected from one or several of Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum and Fusarium redolens.

6. The application according to claim 5, wherein The application method is as follows: (1) Applied to crops infected with Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens, so as to prevent, improve or eliminate the disease state of the crops; (2) Applied to the preparation of a medicament for inhibiting Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens; (3) Applied to the preparation of a pesticide preparation for controlling crop diseases caused by Enterobacter cloacae, Botrytis cinerea, Fusarium oxysporum, Colletotrichum gloeosporioides, Alternaria alternata, Colletotrichum camelliae, Alternaria cucumerina, Fusarium cucumerinum, Fusarium proliferatum or Fusarium redolens.

7. A biocontrol agent, characterized in that, The preparation includes the Paenibacillus polymyxa ( Paenibacillus polymyxa ) NBL-B13008 described in claim 1 or the bacterial agent described in any one of claims 2-4; the biocontrol preparation is a liquid bacterial agent and is used by spraying on the soil of the crop roots.

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