Paenibacillus polymyxa K17 for disease control and application of paenibacillus polymyxa K17

Abstract

The invention discloses paenibacillus polymyxa K17 for preventing and treating diseases, the preservation number of the paenibacillus polymyxa K17 is CGMCC (China General Microbiological Culture Collection Center) No.33366, and the paenibacillus polymyxa K17 is classified and named as Paenibacillus polymyxa K17. The strain has a good anti-antagonism effect on 16 different plant pathogenic fungi from 8 crops; particularly, the antibacterial effect on various leaf spot diseases of tea trees is superior to that of part of common biocontrol strains such as Pristeria aryabhattai 11, Bacillus tequilensis R2 and the like. The control effect on tea tree leaf spot and tea tree anthracnose is higher than 70%, the control effect on black spot of picked tomatoes is 68%, the control effect is equivalent to that of various chemical pesticides, and the method has extremely high application prospects and market value in field biological control and postharvest preservation of plant diseases. Meanwhile, the strain K17 has the plant growth-promoting characteristics of secreting multiple extracellular hydrolases, dissolving inorganic phosphorus and mineral potassium and biologically fixing nitrogen, and has the potential of preparing plant growth-promoting microbial agents or bacterial fertilizers.

Description

Technical Field

[0001] The present invention relates to the technical field of biological control, in particular to a new strain of Paenibacillus polymyxa, and also to the application of the strain in the prevention and control of fungal diseases of crops such as tea, tomatoes and peaches. Background Art

[0002] Fungal diseases are a major type of disease affecting farmland and cash crops in my country, causing significant yield reductions and economic losses. Chemical pesticides are currently the primary means of controlling field or post-harvest fungal diseases of major crops both domestically and internationally. However, the long-term, large-scale application of chemical pesticides can lead to a series of production, environmental, and health problems, such as increased pathogen resistance, reduced efficacy, increased pesticide residues in agricultural products, and ecological damage. Biological control is a plant protection method that utilizes interactions between different species to mitigate the harm caused by pests. It is environmentally friendly and avoids pathogen resistance, making it a sustainable alternative to chemical pesticides. The development of safe, non-toxic, and highly effective biopesticides is a key strategy for sustainable agricultural development in my country.

[0003] Tea is a perennial cash crop, and my country is the world's largest tea producer and exporter. The tea industry plays a vital role in promoting regional economic development and foreign trade earnings in my country. However, tea trees are often grown in mountainous, foggy areas, making them highly susceptible to pests and diseases, severely hindering the high-quality and high-yield development of the tea industry. To this day, Chinese tea is repeatedly notified by the European Union for excessive pesticide residues, and even faces export restrictions. Although my country's microbial pesticide portfolio has continued to expand in recent years, the number and variety of available biocontrol agents remains far lower than in Europe and the United States, and full self-sufficiency has yet to be achieved. In particular, very few biocontrol products are currently available for use in the tea industry. As of 2025, the only registered biocontrol agent in my country for biological control of tea diseases is Bacillus velezensis NSZYBGJ0001, and this bacterium has only been reported for the control of tea anthracnose.

[0004] Paenibacillus polymyxa is a recently discovered bacterium with great potential for biocontrol. Currently, patents related to Paenibacillus polymyxa primarily focus on plant growth regulation, biological nitrogen fixation, soil improvement, organic fertilizer and animal feed fermentation, toxin degradation, and aquaculture. However, research on its use in controlling plant fungal diseases is relatively limited. It is worth noting that different strains of the same biocontrol bacterium can vary significantly in the types and effectiveness of plant diseases they control.

[0005] Patented strains of Paenibacillus polymyxa disclosed in the prior art only target a few diseases and pathogens. For example, Paenibacillus polymyxa DN67 can control American ginseng root rot, watermelon wilt, wheat head blight, and solanaceous wilt; Paenibacillus polymyxa P1 is primarily used to control cucumber powdery mildew and downy mildew; P. polymyxa dgnkzx004 has significant and stable antibacterial effects against Corynespora cassiicola, the pathogen of lipstick leaf spot; and Paenibacillus polymyxa HZ-9 has excellent control effects against soil-borne diseases such as potato scab and black mole. However, there are currently no reports on Paenibacillus polymyxa technologies for the efficient biological control of tea plant diseases. Summary of the Invention

[0006] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a polymyxa K17 for disease control and its application, and to provide a new species of polymyxa with broad-spectrum antibacterial ability that can be used in economic crops such as tea, tomatoes, and citrus, providing more options for the prevention and control of microbial diseases of economic crops, solving the current problem of limited types of biocontrol bacteria in the tea field, and providing a green and efficient alternative to chemical pesticides for a variety of field crops.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, a polymyxa K17 strain is provided for disease control. The strain has been deposited in the General Microbiology Center of the China Culture Collection Administration (CGMCC, address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing) on ​​January 10, 2025. The strain deposit number is CGMCC No. 33366 and the classification name is Paenibacillus polymyxa K17.

[0009] The bacterial agent containing the above-mentioned Paenibacillus polymyxa K17 also falls within the scope of protection of the present invention.

[0010] In the bacterial agent, Paenibacillus polymyxa K17 exists in the form of cultured live bacteria, fermentation liquid or bacterial suspension.

[0011] Preferably, the fermentation broth of Paenibacillus polymyxa K17 is prepared by the following method:

[0012] Inoculate Paenibacillus polymyxa K17 into liquid fermentation medium and culture at 25°C for 1-2 days;

[0013] The liquid fermentation medium is composed of: 10 g of tryptone, 10 g of NaCl, 10 g of yeast powder, 1 L of deionized water, pH 7.0.

[0014] Preferably, the bacterial suspension of Paenibacillus polymyxa K17 is prepared by the following method:

[0015] The fermentation broth of Paenibacillus polymyxa K17 was centrifuged, and the bacterial precipitate was resuspended in a phosphate buffer solution at pH 7 to obtain a bacterial suspension.

[0016] The second aspect of the present invention provides the use of the above-mentioned Paenibacillus polymyxa K17 or the above-mentioned bacterial agent containing Paenibacillus polymyxa K17 in at least one of the following (1)-(5):

[0017] (1) Inhibit the growth of plant pathogens;

[0018] (2) Preparation of products for inhibiting plant pathogens;

[0019] (3) Prevent and control diseases caused by plant pathogens;

[0020] (4) Preparation of products for preventing and treating diseases caused by plant pathogens;

[0021] (5) Preparation of biological agents or fertilizer products that promote plant growth;

[0022] The plant pathogens are mango stem rot pathogen Lasiodiplodia hormozganensis, peach rot pathogen Diaporthe nobilis, tomato gray mold Botrytis cinerea, black spot pathogen Alternaria arborescens, citrus green mold Penicillium digitatum, tea anthracnose pathogen Colletotrichum fructicola, tea anthracnose pathogen Colletotrichum camelliae, tea leaf blight pathogen Pestalotiopsis telopeae, tea leaf blight pathogen Neofusicoccumparvum, tea leaf spot pathogen Lasiodiplodiagonubiensis, tea leaf spot disease Didymella rosea, tea leaf spot disease Hypoxylonsp, tea ring spot disease Pseudopestalotiopsis camelliae-sinensis, tea bud blight pathogen Pyronema sp., tea red leaf spot disease Phyllosticta elongata, melon vine blight pathogen Didymella bryoniae, Rhizoctonia solani, and Fusarium graminearum.

[0023] The third aspect of the present invention provides the use of the above-mentioned Paenibacillus polymyxa K17 in at least one of the following (1)-(4):

[0024] (1) Protease production;

[0025] (2) Production of amylase;

[0026] (3) dissolving phosphate and potassium;

[0027] (4) Biological nitrogen fixation.

[0028] A fourth aspect of the present invention provides a method for preventing tea anthracnose and tea leaf spot, comprising the following steps:

[0029] The above-mentioned Paenibacillus polymyxa K17 or the above-mentioned bacterial agent containing Paenibacillus polymyxa K17 is applied on tea leaves.

[0030] A fifth aspect of the present invention provides a method for treating postharvest black spot disease of tomatoes, comprising the following steps:

[0031] Apply Paenibacillus polymyxa K17 or the above-mentioned bacterial agent containing Paenibacillus polymyxa K17 to the surface of the harvested tomatoes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The new strain of Paenibacillus polymyxa screened in this study exhibits broad-spectrum, highly effective antagonism against 16 different plant pathogens from eight crop species, including five common pathogens of pre- and post-harvest fruit diseases, three field crop diseases, and eight tea plant pathogens. In particular, its antibacterial efficacy against various tea leaf spot pathogens surpasses that of some common biocontrol strains, such as Priestia aryabhattai 11 and Bacillus tequilensis R2. Fermentation broths and inoculants prepared using this new strain of Paenibacillus polymyxa effectively control tea anthracnose, tea leaf spot, and tomato postharvest black spot, achieving efficacy exceeding 68%, comparable to that of various chemical pesticides. This strain has significant potential for application in field biocontrol of plant diseases and holds significant market value. Furthermore, this strain secretes multiple extracellular hydrolases, dissolves inorganic phosphorus and mineral potassium, and biologically fixes nitrogen, demonstrating its potential for promoting plant growth and preventing diseases. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figures are the colony, bacterial morphology and Gram staining of Paenibacillus polymyxa K17 of the present invention; wherein, A is the colony morphology of Paenibacillus polymyxa K17 on different culture media; B is the Gram staining result.

[0035] Figure 2 The diagram is a phylogenetic tree diagram of the 16S rDNA sequence evolution of Paenibacillus polymyxa K17 of the present invention.

[0036] Figure 3 This is the antibacterial spectrum of Paenibacillus polymyxa K17 of the present invention.

[0037] Figure 4 This is a diagram showing the secretion of extracellular enzyme hydrolases, nitrogen fixation and inorganic phosphorus solubilization by Paenibacillus polymyxa K17 of the present invention.

[0038] Figure 5 The figure is a comparison chart of the antibacterial effects of the polymyxa K17 of the present invention and other common Bacillus biocontrol bacteria; wherein A is the antibacterial comparison plate chart, and B is the antibacterial rate results of each biocontrol bacteria.

[0039] Figure 6 This is a diagram showing the biocontrol effect of Paenibacillus polymyxa on tea tree anthracnose.

[0040] Figure 7This is a diagram showing the biocontrol effect of the polymyxa bacteria of the present invention on post-harvest black spot disease of tomatoes. DETAILED DESCRIPTION

[0041] The present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments derived by persons of ordinary skill in the art based on the present invention are within the scope of protection of the present invention.

[0042] Unless otherwise indicated in specific cases, the numerical ranges listed herein include the upper and lower limits, and all integers and fractions within the range, and are not limited to the specific values ​​listed when defining the range.

[0043] 1. Paenibacillus polymyxa K17 for disease control

[0044] 1. Culture medium and its preparation

[0045] PDA solid medium: 200g potato, 20g glucose, 20g agar, 1L deionized water, pH 6.50. Sterilize at 121°C, 1.5 atm, for 30 minutes. After cooling, pour onto a plate (solid medium) or transfer 20mL to a 150mL Erlenmeyer flask (liquid medium) for later use. For liquid medium (PDB), remove the agar.

[0046] LB solid medium (liquid medium without agar): 10 g of tryptone, 10 g of NaCl, 10 g of yeast powder, 1 L of deionized water, pH 7.0.

[0047] Silicate bacterial culture medium: 1g glass powder, sucrose, 0.5g magnesium sulfate heptahydrate, 0.1g calcium sulfate, 2.0g disodium hydrogen phosphate, 0.005g ferric chloride, 15g agar, pH 7.0.

[0048] Inorganic phosphorus selective medium (Pikovskaya medium): glucose 10 g, Ca3(PO4)25 g, (NH4)2SO4 0.5 g, NaCl 0.2 g, KCl 0.2 g, MgSO4·7H2O 0.1 g, FeSO4·7H2O 0.002 g, MnSO4 0.003 g, yeast powder 0.5 g, water 1 L, pH 7.

[0049] Protease detection medium (Skim milk medium): 15g skim milk powder, 20g agar, 1.0L water, natural pH.

[0050] Amylase assay medium: peptone 10.0 g, beef extract 5.0 g, NaCl 5.0 g, soluble starch 2.0 g, agar 20.0 g, distilled water 1.0 L, pH 7.0.

[0051] Ashbys nitrogen-fixing medium: mannitol 10.0 g, anhydrous CaCO3 5 g, KH2PO4 0.2 g, NaCl 0.2 g, MgSO4·7H2O 0.2 g, agar 20 g, water 1.0 L, natural pH.

[0052] All culture media were sterilized at 121°C and 1.5 atmospheres for 30 min, then cooled and poured onto plates (solid culture media) or 20 mL was taken out and placed into 150 mL Erlenmeyer flasks (liquid culture media) for later use.

[0053] 2. Isolation, screening and identification of the Paenibacillus polymyxa K17 strain

[0054] Isolation method: The soil was selectively isolated from the rhizosphere soil of plants in a long-term positioning experiment on vegetable crops in Chongqing using a silicate selective medium (bacteria that can grow on this medium have the ability to decompose and utilize mineral potassium). The microorganisms in the soil were separated using a dilution gradient method. 10.0 g of soil was weighed and placed in a 250 mL Erlenmeyer flask filled with 90 mL of sterile water. The soil suspension was prepared by shaking in a shaker at 25°C and 150 rpm for 1 hour. The soil suspension was then diluted to 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6 and 10 -7 Different concentration gradients were prepared. 0.1 mL 10 -4 ,~10 -6 The diluted soil suspension was evenly spread on the silicate bacterial culture medium plate, and each dilution gradient was repeated 5 times. After the operation was completed, the plate was cultured at 25℃ for 2 days. Different bacteria were selected according to the morphology, color and size of the bacterial colonies, and purified 4 times.

[0055] Identification method: Inoculate the aforementioned strain K17 onto LB and silicate solid media and incubate at 25°C for 48 hours. Observe the colony morphology and photograph it. Use an inoculating loop to remove the colony from the plate and gently smear it onto a glass slide for fixation. After drying, use the Beekman Gram stain kit to stain, decolorize, and rinse in the correct order according to the manufacturer's instructions. After drying, observe under a microscope to determine whether a fungus-free clear zone appears around the bacterial cells. The size of the clear zone represents the antibacterial potential of the biocontrol agent. Figure 1The bacterial strain K17 obtained in the present invention has a moist and smooth colony, and is creamy or light yellow on PDA or LB culture medium, with a slightly convex surface ( Figure 1 A), colorless and transparent on silicate bacterial culture medium. Under an optical microscope, the strain is rod-shaped, with a length of 1.7-2.6 μm and a diameter of 0.8-1.2 μm ( Figure 1 B); Gram staining was positive ( Figure 1 B, positive purple, negative red).

[0056] 3. 16S rRNA gene sequencing of the Paenibacillus polymyxa K17:

[0057] The above strain K17 was inoculated into LB liquid culture medium, cultured at 25°C for 24h, and the bacteria were collected by centrifugation at 10,000rpm. The genomic DNA of strain K17 was extracted using a Sangon column bacterial genomic DNA extraction kit, and the quality of the genomic DNA was detected using Nanodrop2500. Qualified bacterial DNA (OD260 / 280=1.8-2.0, total amount not less than 10μg) was sent to Qingke Biotechnology Co., Ltd. for bacterial 16S rRNA gene amplification and sequencing (Sanger sequencing). Finally, the obtained sequence was aligned with the NCBI bacterial 16S ribosomal RNA gene nucleic acid sequence database, and a phylogenetic tree was constructed using Mega. The results showed that the homology between the strain K17 of the present invention and the genus Paenibacillus polymyxa was as high as 99%, and the phylogenetic analysis showed that the strain K17 and the model strain P.polymyxa DSM 36 were located in the same branch of the phylogenetic tree (support 99, Figure 2 ), indicating that the two are closely related in taxonomic status. Combining morphological and molecular identification results, the strain was identified as Paenibacillus polymyxa K17. The P. polymyxa K1716s rDNA sequence is as follows, with a length of 1354 bp:

[0058]

[0059] The strain Paenibacillus polymyxa K17 provided by the present invention was deposited on January 10, 2025 at the General Microbiology Center of the China Culture Collection Administration Committee of Microorganisms, Institute of Microbiology, Chinese Academy of Sciences (referred to as CGMCC, address: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code: 100101), with the deposit number CGMCC No. 33366, and the classification name is Paenibacillus polymyxa K17.

[0060] 2. Example

[0061] Example 1: Determination of the antibacterial spectrum of P. polymyxa K17

[0062] The antibacterial spectrum of biocontrol bacteria was evaluated using the confrontation culture method. The pathogens tested included: mango stem rot (Lasiodiplodia hormozganensis), peach rot (Diaporthe nobilis), tomato gray mold (Botrytis cinerea) and black spot (Alternaria arborescens), citrus green mold (Penicillium digitatum), tea anthracnose (Colletotrichum fructicola and Colletotrichum camelliae), tea leaf blight (Pestalotiopsis telopeae and Neofusicoccumparvum), tea leaf spot (Lasiodiplodiagonubiensis, Didymella rosea and Hypoxylon sp), tea ring spot (Pseudopestalotiopsis camelliae-sinensis), tea bud blight (Pyronema sp.), tea red leaf spot (Phyllosticta elongata), melon vine blight (Didymella bryoniae), Rhizoctonia solani, and Fusarium graminearum. These pathogens were inoculated onto PDA solid culture medium and cultured at 25°C for 5 days for activation. Along the edge of the activated colony, a 5mm diameter bacterial block was taken and inoculated in the center of the PDA culture medium. The activated bacteria were then inoculated on both sides of the fungal block (3cm away from the block) for confrontation culture. The control was not inoculated with biocontrol bacteria K17 and cultured in the dark at 25°C for 3 to 6 days. Figure 3As shown in the figure, the pathogen colonies treated with CK were round or oval, while when co-cultured with P. polymyxa K17, all pathogenic fungi showed obvious inhibition zones in the radial bacterial direction to varying degrees, with an inhibition rate of 53% to 82%, indicating that K17 has a broad-spectrum and efficient resistance to pathogenic fungi.

[0063] Example 2: Analysis of plant growth-promoting properties of P. polymyxa K17 strain

[0064] 1. Determination of the ability to secrete proteases and amylases

[0065] Most of the organic matter in the soil exists in the form of protein, which is difficult to be directly used by plants. Some plant growth-promoting bacteria can secrete proteases to increase the available nitrogen content in the soil. Proteins are hydrolyzed and disappear under the action of proteases. Microorganisms that can secrete proteases will form a transparent hydrolysis zone around their colonies on a culture medium with pure milk powder as the only nutrient source. Strain K17 was inoculated on a solid culture medium with milk powder and cultured at 25℃ for 2 days. Figure 4 As shown in the figure, stable transparent zones appeared around the three K17 colonies, indicating that P. polymyxa K17 has the ability to produce proteases to hydrolyze proteins.

[0066] Starch turns blue-purple when it comes into contact with iodine. Under the action of amylase, starch is hydrolyzed and disappears. After staining the area around the colony with iodine solution, a transparent hydrolysis zone will form around the colony that can secrete amylase, otherwise it cannot secrete. Strain K17 was inoculated on a culture medium with starch as the only carbon source and cultured at 25℃ for 2 days. Iodine solution was added and the presence of a transparent zone around the colony was observed to determine whether it had the ability to decompose starch. Figure 4 As shown in the figure, stable transparent zones appeared around the three K17 colonies, indicating that P. polymyxa K17 has the ability to produce amylase to hydrolyze starch.

[0067] 2. Determination of phosphorus solubility

[0068] The main inorganic phosphorus sources in soil that are difficult for plants to utilize are poorly soluble tricalcium phosphate, aluminum phosphate, and iron phosphate. Strain K17 was inoculated onto a culture medium containing tricalcium phosphate as the sole phosphorus source and cultured at 25°C for 5 days. The presence of a phosphate-solubilizing zone around the colony was observed to determine its phosphate-solubilizing ability. Figure 4 This is a plate test image of the phosphate solubilization of P.polymyxa K17 of the present invention. Obvious hydrolysis zones appear around the colonies, indicating that P.polymyxa K17 has the ability to solubilize phosphate.

[0069] 3. Determination of potassium-dissolving ability

[0070] Strain K17 was inoculated on a silicate medium with potassium feldspar or glass powder as the sole potassium source and cultured at 25°C for 3 days to observe whether it could grow normally on this selective medium to determine whether it had the ability to solubilize potassium. Figure 1 The culture medium used in the experiment is silicate culture medium. The bacteria that can grow on this culture medium have the ability to decompose and utilize mineral potassium. Therefore, Figure 1 It also shows that the P. polymyxa K17 of the present invention can grow normally on a silicate culture medium and is a typical potassium-solubilizing bacterium, proving that the P. polymyxa K17 has the ability to solubilize potassium.

[0071] 4. Determination of nitrogen fixation capacity

[0072] Inoculate strain K17 onto Ashbys nitrogen-fixing medium (this medium does not contain a nitrogen source), culture at 25°C for 3-5 days, and observe the growth of the colonies. This medium does not contain a nitrogen source. If the strain can grow on the nitrogen-free medium, it proves that the strain has the potential for biological nitrogen fixation. Figure 4 As shown, strain K17 was able to grow on this nitrogen-fixing medium, indicating that it has the potential for biological nitrogen fixation.

[0073] Example 3: Comparison of the antibacterial effects of P. polymyxa K17 strain and other Bacillus against various tea leaf spot pathogens

[0074] The antibacterial ability of P.polymyxa K17 and other common Bacillus biocontrol bacteria was compared by using the confrontation culture method. The operating steps of the test method were the same as those in "Example 1". The biocontrol strains tested were Priestia aryabhattai 11 and Bacillus tequilensis R2, and the pathogens tested were Colletotrichum fructicola, Neofusicoccumparvum, Lasiodiplodia gonubiensis and Hypoxylon sp, and Pseudopestalotiopsis camelliae-sinensis. The control (CK) was not inoculated with biocontrol bacteria, and each treatment was repeated 3 times. After culturing for 3-7 days, the colony diameter was measured and the antibacterial rate was calculated. The calculation method was the same as in "Example 1". Figure 5 As shown in the figure, the inhibition rate of P. polymyxa K17 against the five pathogens tested ranged from 53% to 73%, which was significantly higher than that of other biocontrol bacteria tested at the same time ( Figure 5 ).

[0075] Example 4: P. polymyxa K17 controls tea tree fungal diseases

[0076] Tea Anthracnose Prevention and Control Example: The detached leaf method was used to evaluate the preventive and therapeutic effects of P. polymyxa K17 on tea anthracnose. The experiment was set up with three treatments, including clean water (CK), P. polymyxa K17 fermentation liquid (cfu>10 7 / mL, containing 0.5% Tween 80) and chemical pesticide methyl thiophanate, with 9 biological replicates for each treatment. For all treatments, tea leaves with the same growth were taken, and after surface disinfection, the pathogen was inoculated using the conventional wound inoculation method (2 places / leaf). During the treatment, 4 to 6 hours before the pathogen inoculation, clean water, bacterial fermentation liquid containing strain K17 and diluted pesticides were sprayed on the leaves (pesticides were purchased from the local agricultural product center and configured to the corresponding use concentration according to the instructions). All treatments were sealed in large plates (13×13 cm) and cultured at a constant temperature of 25°C for 7 to 14 days. When the area of ​​a single lesion treated with PI is 2 to 3 cm 2 The leaves of each treatment were photographed, and the lesion area on the leaves was measured using ImageJ to calculate the control effect: control effect = (lesion area of ​​control treatment - lesion area of ​​treatment group) / lesion area of ​​control treatment.

[0077] like Figure 6 As shown, the incidence and morbidity of tea anthracnose were significantly reduced when treated with the biocontrol fungus P. polymyxa K17, with a control effect of 85.76%, which was not significantly different from that of chemical pesticides (t-test, p>0.05).

[0078] Tea leaf spot disease control example: The experiment was conducted in June 2025 at the Guizhou University Farm in Guizhou Province. The experiment included a control (clear water), a commonly used tea leaf spot disease pesticide kasugastatin (effective content 6%), a strain K17 bacterial suspension (bacterial concentration cfu>10 8 , adding 5% Tween 80) and other three treatments. Each treatment had three replicates, each consisting of 10 seedlings. For all treatments, a 1 cm wound was made on the tea seedlings and the above treatments were applied with a brush or spray bottle. After 6 hours, the fungus cake of Lasiodiplodia gonubiensis, the pathogen of tea leaf spot disease, was inoculated. After 7-10 days of incubation, the incidence of each treatment was counted, and the control effect was calculated based on the example of tea tree anthracnose control. As shown in Table 1, the K17 bacteria can effectively inhibit the growth of the tea leaf spot disease pathogen on tea trees. The area of ​​lesions on tea leaves treated with K17 bacteria was only 27% of that of the control treatment; its control effect reached 70.36%, which is the same as that of the leaf spot pesticide kaempferol (t-test, p>0.05).

[0079] Table 1 The control effect of Paenibacillus polymyxa on tea leaf spot

[0080]

[0081] Example 5: P. polymyxa K17 for controlling postharvest black spot in tomatoes

[0082] The experiment was conducted in Guizhou University, Guizhou Province in June 2025. The experiment included a control, a common fruit preservative prochloraz (active ingredient content 450g / L), a fermentation broth containing strain K17 (without removing the bacteria, cfu>10 7 ) and other 3 treatments. Each treatment had 4 repetitions, and each repetition consisted of 9 tomatoes. P.polymyxa K17 fermentation broth was diluted 4 times with water and 2% Tween 80 was added. Pesticide treatment was configured to the corresponding concentration according to the pesticide instructions. After the surface of the tomatoes was disinfected, they were soaked in clean water, K17 fermentation broth and myclobutanil solution for 2-5 minutes respectively. After being fished out and dried, they were inoculated with pathogenic fungi. They were then placed in commercial fruit boxes for culture for 2-5 days, and the area of ​​lesions in each treatment was counted. For the calculation of the prevention and control effect, refer to the formula of Example 4: Example of prevention and control of tea anthracnose. As Figure 7 As shown, the application of pesticides and fermentation liquid containing strain K17 significantly reduced the growth of black spot pathogens on tomatoes, and the control rate of black spot disease by fermentation liquid containing strain K17 was 68.81%, slightly higher than that of chemical pesticide prochloraz treatment (control rate 64.76%).

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that in terms of biological control, the expansion of the antibacterial spectrum of the strain obtained by the present invention and the replacement of crop disease types, as well as the microbial agents and biopesticides prepared from the bacterial cells and secondary metabolites of the strain, should be deemed to be within the purpose and scope of the technical solutions of the present invention and should be covered by the scope of the claims of the present invention.

Claims

1. A Paenibacillus polymyxa K17 for disease control, the strain having a deposit number of CGMCC No. 33366.

2. A bacterial agent containing the Paenibacillus polymyxa K17 according to claim 1.

3. The bacterial agent according to claim 2, characterized in that In the bacterial agent, Paenibacillus polymyxa K17 exists in the form of cultured live bacteria, fermentation liquid or bacterial suspension.

4. The bacterial agent according to claim 2 or 3, characterized in that The formulation of the bacterial agent is a wettable powder, a water dispersant, a water suspension or a dispersible oil suspension.

5. Use of the Paenibacillus polymyxa K17 according to claim 1 or the bacterial agent containing Paenibacillus polymyxa K17 according to any one of claims 2 to 4 in at least one of the following (1) to (5): (1) Inhibit the growth of plant pathogens; (2) Preparation of products for inhibiting plant pathogens; (3) Prevention and control of diseases caused by plant pathogens; (4) Preparation of products for preventing and treating diseases caused by plant pathogens; (5) Preparation of biological agents or fertilizer products that promote plant growth; The plant pathogens are mango stem rot pathogen Lasiodiplodia hormozganensis, peach rot pathogen Diaporthe nobilis, tomato gray mold Botrytis cinerea, black spot pathogen Alternaria arborescens, citrus green mold Penicillium digitatum, tea anthracnose pathogen Colletotrichum fructicola, tea anthracnose pathogen Colletotrichum camelliae, tea leaf blight pathogen Pestalotiopsis telopeae, tea leaf blight pathogen Neofusicoccumparvum, tea leaf spot pathogen Lasiodiplodiagonubiensis, tea leaf spot disease Didymella rosea, tea leaf spot disease Hypoxylonsp, tea ring spot disease Pseudopestalotiopsis camelliae-sinensis, tea bud blight pathogen Pyronema sp., tea red leaf spot disease Phyllosticta elongata, melon vine blight pathogen Didymella bryoniae, Rhizoctonia solani, and Fusarium graminearum.

6. Use of the Paenibacillus polymyxa K17 according to claim 1 in at least one of the following (1) to (4): (1) Protease production; (2) Production of amylase; (3) dissolving phosphate and potassium; (4) Biological nitrogen fixation.

7. A method for preventing anthracnose and leaf spot of tea trees, characterized in that: The following steps are involved: The Paenibacillus polymyxa K17 according to claim 1 or the bacterial agent containing Paenibacillus polymyxa K17 according to any one of claims 2 to 4 is applied on tea leaves.

8. A method for preventing and treating postharvest black spot disease of tomatoes, characterized in that: The following steps are involved: The Paenibacillus polymyxa K17 according to claim 1 or the bacterial agent containing Paenibacillus polymyxa K17 according to any one of claims 2 to 4 is applied to the surface of post-harvest tomatoes.

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