Bacillus thuringiensis and application thereof

Abstract

The application discloses a bacillus thuringiensis and application thereof. The bacillus thuringiensis ZF505 provided by the application has a preservation number of CGMCC No.24585 in the China General Microbiological Culture Collection Center. A potting living body test shows that the bacillus thuringiensis can prevent and treat cucumber downy mildew with a highest effect of 73.01%, and the bacillus thuringiensis CGMCC No.24585 can promote the increase of the content of three endogenous hormones of cucumber, wherein gibberellin is increased by 15.61%, indole acetic acid is increased by 5.05%, and zeatin is increased by 5.12%.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a strain of Bacillus thuringiensis and its applications. Background Technology

[0002] Downy mildew of cucumber, caused by the obligate oomycete *Pseudoperonospora cubensis*, is one of the most devastating diseases affecting cucumbers, resulting in severe yield and quality losses worldwide. However, persistently resistant varieties of downy mildew are still lacking, making chemical control one of the most effective methods for managing this disease. Fungicides with different modes of action have been widely used to control the disease, such as triadimefon fungicides like cymoxanil, carbamate fungicides like propiconazole, and morpholine fungicides like dimethomorph. However, under long-term selection pressure from fungicides and the seasonal sexual reproduction of the pathogen, fungal pathogens often rapidly differentiate and develop resistance to fungicides. Therefore, developing reasonable resistance management methods is crucial for controlling cucumber downy mildew. The application of biological agents to control pathogens resistant to repeated fungicide use is less likely to induce resistance and shows broad application prospects.

[0003] Bacillus is a widely distributed aerobic and anaerobic Gram-positive bacillus, easily isolated from soil. It produces heat-resistant and stress-resistant spores, possessing significant biocontrol potential and has become one of the most important biological agents. Common Bacillus species include Bacillus thuringensis, Bacillus subtilis, and Paenibacillus polymyxa. However, there are no reports of using Bacillus thuringensis to control cucumber downy mildew; therefore, there is an urgent need to discover highly effective and stable Bacillus thuringensis strains for the control of cucumber downy mildew. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to inhibit downy mildew pathogens in fruit and vegetable crops and / or prevent downy mildew in cucumbers.

[0005] To address the aforementioned technical problems, this invention provides for the first time a strain of Bacillus thuringensis, namely Bacillus thuringensis ZF505, which has the accession number CGMCC No.24585 at the China General Microbiological Culture Collection Center.

[0006] The present invention also provides a composition containing the above-mentioned Bacillus thuringiensis.

[0007] The composition may be a culture, which is a substance obtained by culturing the Bacillus thuringiensis in a microbial culture medium.

[0008] The active ingredient in the above composition may be the Bacillus thuringiensis or / and the metabolites of the Bacillus thuringiensis or / and the culture of the Bacillus thuringiensis.

[0009] In the above text, the metabolites can be obtained from the shake culture broth of Bacillus thuringiensis. The metabolites can be bacterial metabolites of Bacillus thuringiensis. Specifically, the bacterial metabolites of Bacillus thuringiensis can be prepared by culturing Bacillus thuringiensis in LB liquid medium and collecting the bacterial solution, which is the bacterial metabolite of Bacillus thuringiensis.

[0010] The culture can be a substance obtained by culturing the Bacillus thuringiensis in a microbial culture medium.

[0011] The culture medium is made from the following raw materials: yeast extract, tryptone, sodium chloride, and water. The yeast extract contains 0.5% by mass, the tryptone contains 1% by mass, the sodium chloride contains 1% by mass, and the pH is 7.0-7.5.

[0012] The substance may be a fermentation product, such as a fermentation broth containing the Bacillus thuringiensis and a substance secreted into a liquid culture medium, or a solid fermentation product containing the Bacillus thuringiensis and a substance secreted into a solid culture medium.

[0013] The composition may be a microbial agent. The microbial agent may be a pathogen inhibitor or a disease inhibitor.

[0014] In the above text, the composition may be any of the following:

[0015] A1) A composition for controlling downy mildew in cucumbers;

[0016] A2) Compositions that act as pathogen inhibitors;

[0017] A3) Compositions used as disease inhibitors;

[0018] A4) Compositions that increase the content of endogenous hormones in plants;

[0019] A5) Compositions that increase the gibberellin content of plants;

[0020] A6) A composition that increases the indoleacetic acid content in plants;

[0021] A7) A composition that increases the content of zeatin in plants;

[0022] A8) A composition that promotes plant growth.

[0023] The pathogen may be *Pseudoperonospora cubensis*, and the disease may be cucumber downy mildew.

[0024] The present invention also provides a method for preparing the above composition, the method comprising the step of using the above-mentioned Bacillus thuringiensis as a component of the composition.

[0025] The scope of protection of this invention also includes the use of the above-mentioned Bacillus thuringiensis or composition in the preparation of products.

[0026] The product may be a composition, a microbial agent, or a fertilizer. The product may contain the aforementioned Bacillus thuringiensis.

[0027] The active ingredients of the above composition may also contain other biological or non-biological components, and those skilled in the art can determine the other active ingredients of the above composition based on the effects of the composition.

[0028] The above composition can also be a microbial agent or a microbial fertilizer.

[0029] The aforementioned microbial agents refer to live microbial preparations made by using a carrier as an adsorbent to adsorb the fermentation broth or solid fermentation products of the target microorganisms after propagation.

[0030] The above-mentioned microbial agents can be in various dosage forms, including but not limited to liquids, emulsions, suspensions, powders, granules, wettable powders, or water-dispersible granules.

[0031] Depending on the needs, the microbial agent may also include a carrier. The carrier may be a solid carrier or a liquid carrier.

[0032] The above-mentioned microbial fertilizer is a liquid microbial phosphate fertilizer with a strong phosphorus solubilization ability, which can convert insoluble phosphorus into soluble phosphorus that can be absorbed and utilized by plants.

[0033] The aforementioned carrier may specifically be at least one of calcium phosphate, rice husk powder, wheat bran, rice bran, skim milk powder, maltodextrin, sucrose, glycerol, and starch.

[0034] The above-mentioned products should have at least one of the following properties:

[0035] B1) Used to prevent and control cucumber downy mildew;

[0036] B2) as a pathogen inhibitor;

[0037] B3) as a disease inhibitor;

[0038] B4) Increases the content of endogenous hormones in plants;

[0039] B5) Increases the gibberellin content in plants;

[0040] B6) Increases the indoleacetic acid content in plants;

[0041] B7) Increases the content of plant zeatin nucleosides;

[0042] B8) Promotes plant growth.

[0043] The present invention also provides a method for preventing and controlling downy mildew in plants and / or increasing the level of endogenous hormones in plants, the method comprising contacting plants with the above-mentioned Bacillus thuringiensis or its composition to prevent and control downy mildew in plants and / or increase the level of endogenous hormones in plants.

[0044] The plant may be a seedling.

[0045] The endogenous hormone may be gibberellin, indoleacetic acid, and / or zeatin.

[0046] The plant mentioned above can be any of the following:

[0047] C1) Angiosperms;

[0048] C2) Dicotyledons;

[0049] C3) Cucurbitales plants;

[0050] C4) Cucurbitaceae plants;

[0051] C5) Cucumber species;

[0052] C6) Cucumber.

[0053] This invention investigated the disease control and endogenous hormone secretion-promoting functions of Bacillus thuringiensis ZF505 collected from potato rhizosphere soil in Zhangjiakou City, Hebei Province. Through in vivo pot experiments, this study found that Bacillus thuringiensis achieved a control effect of up to 73.01% against cucumber downy mildew. Simultaneously, Bacillus thuringiensis ZF505 promoted an increase in the content of three endogenous hormones in cucumber: gibberellin increased by 15.61%, indoleacetic acid by 5.05%, and zeatin by 5.12%. This provides new microbial resources and theoretical basis for the use of microorganisms in biocontrol and the preparation of bio-agent products.

[0054] Preservation Instructions

[0055] Bacterial strain name: Bacillus thuringiensis

[0056] Latin name: Bacillus thuringensis

[0057] Strain number: ZF505

[0058] Preservation Institution: China General Microbiological Culture Collection Center, China Microbiological Culture Collection Committee

[0059] Collection institution abbreviation: CGMCC

[0060] Address: No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing

[0061] Deposit date: March 24, 2022

[0062] Collection Center Registration Number: CGMCC No. 24585 Attached Figure Description

[0063] Figure 1 Phylogenetic tree of Bacillus thuringiensis ZF505 and related strains constructed based on 16S rDNA, rpoB, and groEL gene sequences.

[0064] Figure 2 The colony morphology of Bacillus thuringiensis ZF505.

[0065] Figure 3 The leaf morphology of cucumbers affected by downy mildew.

[0066] Figure 4 Morphological characteristics of sporangiophores and sporangia of *Pseudomonas cucumeroides*. Detailed Implementation

[0067] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0068] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0069] The following examples use SPSS 23.0.0.0 statistical software to process the data and use the t-test method to perform statistical difference analysis. The English letters after the values ​​in each column indicate the degree of significance of the difference. Treatments with the same letter have no significant difference at the 0.05 level, while treatments without the same letter have a significant difference at the 0.05 level.

[0070] The raw materials for the culture media in the following examples are as follows:

[0071] Strain isolation and culture medium (LB medium): tryptone 10 g / L, yeast extract 5 g / L, sodium chloride 10 g / L, distilled water to a final volume of 1 L. Solid culture medium requires the addition of 20 g / L agar.

[0072] Control fungicide: 50% dimethomorph wettable powder (Shandong Keda Chuangye Biotechnology Co., Ltd., purchased from the market).

[0073] Plant gibberellin (Catalog No.: HBDY-0125O2), auxin (Catalog No.: F6269-A), and zeatin nucleoside kit (Catalog No.: HBDY-0124O2): purchased from Beijing Huabodeyi Biotechnology Co., Ltd.

[0074] In the following examples, cucumber downy mildew was investigated on a whole-leaf basis, and the disease grading criteria are as follows:

[0075] Grading standard: Grade 0: No lesions.

[0076] Grade 1: The lesion area accounts for less than 5% of the total leaf area;

[0077] Grade 3, with lesions covering 6%-10% of the entire leaf area;

[0078] Level 5, with lesions covering 11%-25% of the entire leaf area;

[0079] Level 7, with lesions covering 26%-50% of the entire leaf area.

[0080] Level 9, with lesions covering more than 50% of the entire leaf area.

[0081] Four to six days after inoculation, once the water control group has fully developed disease, investigate the disease severity and calculate the control efficacy. Calculate the disease index and control effect using the formula: Disease Index = ∑(Number of diseased leaves at each level × Relative level value) / (Total number of leaves investigated × 9) × 100%.

[0082] Unless otherwise specified, all quantitative experiments in the following examples are performed in triplicate.

[0083] Example 1: Isolation and Identification of Strains

[0084] 1.1 Screening and purification of strains

[0085] Rhizosphere soil samples were collected from potatoes in Zhangjiakou City, Hebei Province. 10g of soil sample was weighed and fully suspended in 90mL of sterile water. The sample was then placed on a shaker at 37℃ and 200r / min for 15min to ensure full suspension. After treatment in an 80℃ water bath for 10min, the sample was serially diluted to 10⁻⁶. -3 10 -4After concentration, 10 μL of the suspension was evenly spread onto LB agar plates and incubated at 30°C for 2 days. Each treatment was repeated three times. Bacterial strains with different morphologies were picked for purification and numbered. When cultured on an LB solid substrate at 28°C, colonies of strain ZF505 were disc-shaped or oval with irregular edges and rough wrinkles. Figure 2 Further identification of the strain was conducted.

[0086] 2. Identification

[0087] 2.1 Molecular biological identification

[0088] Genomic DNA of strain ZF505 was extracted according to the instructions of the bacterial genomic DNA extraction reagent (Tiangen Biotech (Beijing) Co., Ltd., product number: DP302). The genomic DNA of the strain was amplified by PCR using the universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') / 1492R (5'-GGTTACCTTGTTACGACTT-3') for 16S rDNA sequence, rpoB-F (5'-ATCGAAACGCCTGAAGGTCCAAACAT-3') / rpoB-R (5'-ACACCCTTGTTACCGTGACGACC-3') for rpoB sequence, gyrB-F (5'-GCTTACCAGGGAAATTGGCAG-3') / gyrB-R (5'-ATCAACGTCGGCGTCGG-3') for gyrB sequence, and groEL-F (5'-GTGCGAACCCAATGGGTCTTC-3') / groEL-R (5'-CCTTGTTGTACCACTTGCTC-3') for groEL sequence. PCR reaction system (50 μL): 25 μL 2×KeyPoMaster Mix (Dye Plus), 2 μL upstream primer, 2 μL downstream primer, 1 μL DNA template, 20 μL ddH2O. PCR reaction program: 98℃ pre-denaturation for 5 min, 98℃ denaturation for 10 s, 56℃ annealing for 5 s, 72℃ extension for 20 s, 35 cycles, with a final extension at 72℃ for 5 min. The amplified products were sequenced by Beijing Bomeide Gene Technology Co., Ltd. The sequencing results were compared using BLAST on the NCBI (National Center for Biotechnology Information) website, and the result with the highest consistency ranking was used as the preliminary identification result of the strain.

[0089] Phylogenetic analysis of the assembled three sequences (sequences in the sequence listing) revealed that strain ZF505 clustered with Bacillus thuringensis (CP014847.1) on the same branch, with 100% support for the bootstrap. Figure 1 ).

[0090]

[0091] In Sequence 1, positions 1-381 are the partial sequence of the groEL gene, positions 382-1479 are the partial sequence of the rpoB gene, positions 1480-1759 are the partial sequence of the gyrB gene, and positions 1760-3205 are the reverse complementary sequences of the partial sequence of the 16S rDNA gene.

[0092] 2.2 Physiological and biochemical characteristics of strain ZF505

[0093] Table 1. Physiological and biochemical characteristics of strain ZF505

[0094] Item Reaction Item Reaction 1%, 4%, 8% NaCl + L-glutamic acid + D-galactose + L-histidine + Sucrose + D-aspartic acid Alpha-D-glucose + L-pyroglutamic acid - L-alanine + L-arginine + D-sorbitol + D-mannitol +

[0095] Note: + indicates positive; - indicates negative.

[0096] Strain ZF505 can grow on 1%-8% NaCl medium, with an optimal pH of 6.0. It cannot grow at pH 5.0 and can liquefy gelatin. It can utilize most carbon sources such as D-galactose, sucrose, α-D-glucose, D-sorbitol, and D-mannitol. It can utilize most nitrogen sources such as L-alanine, L-arginine, L-glutamic acid, and L-histidine, but cannot utilize D-aspartic acid or L-pyroglutamic acid (Table 1).

[0097] Bacillus thuringiensis ZF505 was deposited at the China General Microbiological Culture Collection Center (CGMCC) on March 24, 2022, with accession number CGMCC No. 24585. Hereinafter referred to as Bacillus thuringiensis CGMCC No. 24585.

[0098] Example 2: Evaluation of the control efficacy of Bacillus thuringiensis CGMCC No. 24585 bacterial suspension against cucumber downy mildew.

[0099] 2.1 Preparation of Bacillus thuringiensis bacterial culture

[0100] Bacillus thuringiensis CGMCC No. 24585, stored in a cryovial at -80℃, was inoculated onto an LB agar plate using an inoculation loop. The plate was then incubated at 28℃ for 48 hours. After activation, a single colony of the strain was picked and inoculated into LB liquid medium. The medium was then incubated at 28℃ and 180 rpm for 36 hours with shaking to obtain Bacillus thuringiensis bacterial suspension.

[0101] The Bacillus thuringiensis bacterial suspension was diluted 50 times with sterile water to obtain a 50-fold diluted Bacillus thuringiensis CGMCC No. 24585 bacterial suspension (the content of Bacillus thuringiensis CGMCC No. 24585 was 1×10⁵). 6 (CFU / mL)

[0102] 2.2 Preparation of cucumber downy mildew spore suspension

[0103] Cucumber leaves infected with downy mildew were collected from the experimental field of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences. The lesions on the upper surface of the affected leaves appear as water-soaked, pale greenish-yellow spots. The expansion of these spots is limited by leaf veins and is polygonal in shape. Figure 3 In medium humidity (A), a grayish-black mold layer grows on the lesions on the underside of the leaves. Figure 3 (Medium B) Clean the surface of diseased leaves with sterile water to remove debris. Use sterile water containing 0.1% Tween 20 to scrub the sporangia of *Pseudomonas columbarium* on the surface of the diseased leaves, preparing a spore suspension and adjusting it to a concentration of 10. 5 1 spore / ml. The spore suspension contains sporangiophores and sporangia. After the sporangia release spores, the spores are examined under a microscope. Their morphological characteristics are: the upper part of the sporangiophore is bifurcate, branching 3 to 6 times, with the terminal branches slightly curved or straight; the sporangia are oval or lemon-shaped, with a nipple-like projection at the apex, unicellular, and light brown (see...). Figure 4 It has been identified as *Pseudoperonospora cubensis*. Store at 4°C.

[0104] 2.3 Evaluation of the control efficacy of Bacillus thuringiensis CGMCC No. 24585 bacterial suspension against cucumber downy mildew

[0105] In May 2024, a pot experiment was conducted in a greenhouse at the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, to study the efficacy of cucumber control in pots. Seeds of cucumber variety Zhongnong 6 (purchased from Zhongshu Seed Industry Technology (Beijing) Co., Ltd.) were sown in seedling trays, and the experiment was conducted after the cucumbers had developed two leaves and a central bud. The experiment included four treatments:

[0106] 1) Treatment with Bacillus thuringiensis CGMCC No.24585 bacterial solution: Spray the above-mentioned Bacillus thuringiensis CGMCC No.24585 bacterial solution at a dilution of 50 times onto cucumber leaves, spraying evenly.

[0107] 2) Treatment with 50% dimethomorph wettable powder: Spray 50% dimethomorph wettable powder onto cucumber leaves and spray evenly.

[0108] 3) Treatment with 10 billion live bacteria / gram of Bacillus thuringiensis wettable powder: Spray 10 billion live bacteria / gram of Bacillus thuringiensis wettable powder onto cucumber leaves and spray evenly.

[0109] 4) Spray the cucumber leaves evenly with sterile water.

[0110] After 24 hours of spraying, all treatments were sprayed at a concentration of 10. 5 One spore / mL of cucumber downy mildew spore suspension. The procedures were identical across all treatments, except for the different pesticides used.

[0111] Each treatment was set up with three replicates. Each replicate contained 15 cucumber seedlings.

[0112] Four to 15 days after inoculation, after the water control showed sufficient disease development, the disease severity was investigated, and the control efficacy was calculated. The results are shown in Table 2 below: The control efficacy of 50-fold dilution of Bacillus thuringiensis CGMCC No. 24585 against cucumber downy mildew in the first and second replicate tests was 69.31% and 72.62%, respectively. Both were higher than those of the chemical fungicide 50% dimethomorph wettable powder (59.28% and 52.77% in the first and second replicate tests, respectively) and Bacillus thuringiensis wettable powder at 10 billion viable cells / gram (68.46% and 64.50% in the first and second replicate tests, respectively). The 50-fold dilution of Bacillus thuringiensis CGMCC No. 24585 showed a control efficacy of 55.29% against cucumber downy mildew in the third replicate test. This is higher than that of Bacillus thuringiensis wettable powder (37.53%) with 10 billion viable cells / gram, but slightly lower than that of the chemical fungicide 50% dimethomorph wettable powder (56.18%). In conclusion, the 50-fold dilution of Bacillus thuringiensis CGMCC No. 24585 exhibits good and stable control efficacy against cucumber downy mildew.

[0113] Table 2. Control efficacy of 50-fold dilution of Bacillus thuringiensis CGMCC No. 24585 against cucumber downy mildew.

[0114]

[0115] Example 3: Evaluation of the effect of 50-fold dilution of Bacillus thuringiensis CGMCC No. 24585 on endogenous hormone levels in cucumber.

[0116] 3.1 Culture of Bacillus thuringiensis CGMCC No. 24585

[0117] Bacillus thuringiensis CGMCC No. 24585, stored in cryovials at -80℃, was inoculated onto LB agar plates using an inoculation loop and cultured at 28℃ for 48 hours. After activation, single colonies of the strain were picked and inoculated into LB liquid medium and cultured at 28℃ with shaking at 180 rpm for 36 hours.

[0118] 3.2 Effects of Bacillus thuringiensis CGMCC No. 24585 on endogenous hormone levels in cucumber

[0119] The plant hormone kits from Beijing Huabodeyi Biotechnology Co., Ltd. were used to determine the contents of the endogenous plant hormones gibberellin (GA3), indoleacetic acid (IAA), and zeatin nucleoside (ZR) in cucumber leaves. The specific procedures were performed according to the kit instructions. Each treatment was repeated in triplicate, with 15 cucumber plants per replicate.

[0120] After spraying with Bacillus thuringiensis CGMCC No. 24585 bacterial solution, the content of endogenous hormones in cucumber leaves increased significantly, with gibberellin increasing by 15.61%, indoleacetic acid increasing by 5.05%, and zeatin increasing by 5.12% (Table 3).

[0121] Table 3. Effects of Bacillus thuringiensis CGMCC No. 24585 bacterial culture on hormone levels in cucumber.

[0122] Treatment Gibberellin (ng / g) Indoleacetic acid (μg / g) Zeaaridin (μg / g) CGMCC No. 24585 5.68±0.084a 15.92±0.26a 1.64±0.03a Not inoculated with biocontrol bacteria 4.91±0.075b 15.16±0.18b 1.56±0.02b Change rate / % 15.61％ 5.05％ 5.12％

[0123] Example 4: Comparison of the efficacy of Bacillus thuringiensis CGMCC No. 24585 with similar biocontrol agents in controlling cucumber downy mildew.

[0124] To evaluate the difference in efficacy between Bacillus thuringiensis CGMCC No. 24585 and similar biocontrol agents in controlling cucumber downy mildew, a pot experiment was conducted to assess and compare their effects.

[0125] Bacillus thuringiensis CGMCC No. 24585 was diluted 50 times and sprayed on cucumber leaves. Other control biocontrol agents were diluted according to the dilution ratios in Table 4, and the application method was the same as for Bacillus thuringiensis CGMCC No. 24585. A water control was established by spraying the leaves with water after inoculation with the pathogen, while a healthy control was established by spraying only with water without pathogen inoculation. 24 hours after spraying, the concentration for all treatments was 10... 5 The cucumber downy mildew spore suspension was prepared according to Example 2, section 2.2.

[0126] Table 4. Sources of materials used in each treatment

[0127] Number Treatment Use concentration Production company 1 Bacillus thuringiensis CGMCC No. 24585 bacterial liquid 50 times liquid This patent bacterial liquid 2 5 billion spores / g Pseudomonas fluorescens wettable powder 1000 times liquid Shandong Taibo Pharmaceutical Co., Ltd. 3 100 billion spores / g Bacillus subtilis wettable powder 500 times liquid Shandong Weifang Shuangxing Pesticide Co., Ltd. 4 1 billion CFU / g Bacillus amyloliquefaciens wettable powder 500 times liquid Jiangsu Subin Biological and Chemical Co., Ltd. 5 50% dimethomorph wettable powder 1000 times liquid Shandong Keda Pioneer Biological Co., Ltd. 6 Only inoculated with pathogenic bacteria - - 7 Healthy control (not inoculated with pathogenic bacteria, only sprayed with water) - -

[0128] Pot experiments (Table 5) showed that Bacillus thuringiensis CGMCC No. 24585 had a control efficacy of 43.64%, which was only lower than that of the chemical fungicide 50% dimethomorph wettable powder (49.04%), and the same as that of 500 million spores / g Pseudomonas fluorescens wettable powder (43.64%). This efficacy was higher than other similar biocontrol agents: 10 billion spores / g Bacillus subtilis wettable powder (35.47%) and 1 billion CFU / g Bacillus amyloliquefaciens wettable powder (34.97%). Therefore, it has broad commercial prospects for controlling cucumber downy mildew.

[0129] Table 5. Comparison of biocontrol efficacy of Bacillus thuringiensis CGMCC No. 24585 with similar registered biocontrol agents.

[0130] Number Treatment Use concentration Disease index Control effect / % 1 Bacillus thuringiensis CGMCC No. 24585 bacterial liquid 50 times liquid 37.78 43.64 2 5 billion spores / g Pseudomonas fluorescens wettable powder 1000 times liquid 37.78 43.64 3 100 billion spores / g Bacillus subtilis wettable powder 500 times liquid 43.25 35.47 4 1 billion CFU / g Bacillus amyloliquefaciens wettable powder 500 times liquid 43.59 34.97 5 50% dimethomorph wettable powder 1000 times liquid 34.16 49.04 6 Only inoculated with pathogenic bacteria - 67.03 - 7 Healthy control (not inoculated with pathogenic bacteria, only sprayed with water) - 0.00 -

[0131] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. Bacillus thuringiensis, characterized in that, The Bacillus thuringiensis is Bacillus thuringiensis (Bacillus thuringiensis) Bacillus thuringensis ZF505 has the accession number CGMCC No. 24585 at the China General Microbiological Culture Collection Center.

2. The composition, characterized in that, The composition contains Bacillus thuringiensis as described in claim 1.

3. The composition according to claim 2, characterized in that, The composition is a culture, and the culture is the Bacillus thuringiensis culture according to claim 1.

4. The composition according to claim 2, characterized in that, The composition is a microbial agent.

5. The composition according to any one of claims 2-4, characterized in that, The composition is any one of the following: A1) A composition for controlling downy mildew in cucumbers; A2) Compositions that increase the gibberellin content of plants; A3) A composition that increases the indoleacetic acid content in plants; A4) A composition that increases the content of plant zeatin; A5) Compositions that promote plant growth; The plant in question is a cucumber.

6. A method for preparing the composition, characterized in that, The composition is the composition according to any one of claims 2-5, and the method includes the step of using Bacillus thuringiensis as a component of the composition according to claim 1.

7. The use of the Bacillus thuringiensis of claim 1 or the composition of claims 2-5 in the preparation of the product.

8. The product according to claim 7, characterized in that, The product has at least one of the following properties: B1) Used to prevent and control cucumber downy mildew; B2) Increase the gibberellin content in plants; B3) Increases the indoleacetic acid content in plants; B4) Increase the content of plant zeatin nucleosides; B5) Promotes plant growth; The plant in question is a cucumber.

9. A method for preventing and controlling downy mildew in plants and / or increasing the level of endogenous hormones in plants, characterized in that, The method comprises contacting plants with Bacillus thuringiensis as described in claim 1 or the compositions described in claims 2-5 to prevent downy mildew and / or increase the level of endogenous hormones in plants; the plant is cucumber; the endogenous hormones are gibberellin and / or indoleacetic acid and / or zeatin.

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