Bacillus thuringiensis and application thereof

Abstract

The invention discloses a bacillus thuringiensis strain and an application thereof. The bacillus thuringiensis ZF505 provided by the invention has the preservation number of CGMCC (China General Microbiological Culture Collection Center) No.24585 in the General Microbiological Culture Collection Center of the China Committee for Culture Collection of Microorganisms. A potted living body test shows that the highest control effect of the bacillus thuringiensis on cucumber downy mildew can reach 73.01%, meanwhile, the bacillus thuringiensis CGMCC No.24585 can promote the increase of the content of three endogenous hormones in cucumbers, gibberellin is increased by 15.61%, indoleacetic acid is increased by 5.05%, and corn nucleoside is increased by 5.12%.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and specifically relates to a Bacillus thuringiensis strain and application thereof. Background Art

[0002] Cucumber downy mildew, caused by the obligate plant pathogenic oomycete Pseudoperonospora cubensis, is one of the most devastating diseases of cucumber, causing serious yield and quality losses in cucumbers worldwide. However, there is still a lack of durable resistant varieties to downy mildew, so chemical control remains one of the most effective methods for controlling the disease. Fungicides with different modes of action have been widely used to control the disease, such as triadimefon fungicide cymoxanil, carbamate fungicide cymoxanil, and morpholine fungicide oxazolidinone. However, under the long-term selection pressure of pesticides and the seasonal sexual reproduction of pathogenic fungi, fungal pathogens tend to differentiate rapidly and develop resistance to fungicides. Therefore, it is crucial to develop reasonable resistance management methods for the prevention and control of cucumber downy mildew. The use of biological agents to control pathogenic fungi that are resistant to repeated use of fungicides is not easy to develop resistance, showing broad application prospects.

[0003] Bacillus is a widely distributed aerobic and anaerobic Gram-positive rod. It is easy to be isolated from the soil and can produce heat-resistant and stress-resistant spores. It has significant biocontrol potential and has become one of the most important biological agents. Currently, the common Bacillus mainly include Bacillus thuringensis, Bacillus subtilis, Paenibacillus polymyxa, etc. However, there is no report on the use of Bacillus thuringensis to control cucumber downy mildew. Therefore, it is urgent to explore efficient and stable Bacillus thuringiensis to control cucumber downy mildew. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to inhibit downy mildew of fruit and vegetable crops and / or prevent and control downy mildew of cucumber.

[0005] In order to solve the above technical problems, the present invention provides a strain of Bacillus thuringiensis for the first time. The Bacillus thuringensis is Bacillus thuringensis ZF505, and its deposit number in the General Microbiological Center of China Microbiological Collection Committee is CGMCC No.24585.

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

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

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

[0009] In the above, the metabolite can be obtained from the shaking culture of the Bacillus thuringiensis. The metabolite can be a bacterial metabolite of the Bacillus thuringiensis. The bacterial metabolite of the Bacillus thuringiensis can be prepared according to the following method: the Bacillus thuringiensis is cultured in LB liquid culture medium, and the bacterial liquid is collected, and the bacterial liquid is the bacterial metabolite of the Bacillus thuringiensis.

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

[0011] The culture medium is made of the following raw materials: yeast extract, tryptone, sodium chloride and water. The mass percentage of yeast extract in the culture medium is 0.5%, the mass percentage of tryptone is 1%, the mass percentage of sodium chloride is 1%, and the pH value 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 can be a bacterial agent. The bacterial agent can be a pathogen inhibitor or a disease inhibitor.

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

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

[0016] A2) Compositions as pathogen inhibitors;

[0017] A3) Compositions as disease inhibitors;

[0018] A4) a composition for increasing the content of endogenous hormones in plants;

[0019] A5) a composition for increasing the gibberellin content of a plant;

[0020] A6) A composition for increasing the indoleacetic acid content of a plant;

[0021] A7) A composition for increasing the content of zea mays nucleoside in plants;

[0022] A8) Compositions for promoting 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, which comprises the step of using the above Bacillus thuringiensis as a component of the composition.

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

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

[0027] The active ingredients of the above composition may also contain other biological ingredients or non-biological ingredients. Those skilled in the art may determine the other active ingredients of the above composition according to the effects of the composition.

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

[0029] The above-mentioned bacterial agent refers to a live bacterial preparation made by expanding the target microorganisms and using a carrier as an adsorbent to adsorb the fermentation liquid or solid fermentation product of the bacteria.

[0030] The above-mentioned bacterial agents may be in various dosage forms, including but not limited to liquid, emulsion, suspension, powder, granule, wettable powder or water dispersible granule, etc.

[0031] The bacterial agent may further include a carrier as required, and the carrier may be a solid carrier or a liquid carrier.

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

[0033] The above-mentioned carrier can specifically be at least one of calcium phosphate, rice husk powder, bran, rice bran, skimmed milk powder, maltodextrin, sucrose, glycerol and starch.

[0034] The above products shall have at least one of the following properties:

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

[0036] B2) as an inhibitor of pathogens;

[0037] B3) as a disease inhibitor;

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

[0039] B5) Increase the content of gibberellins in plants;

[0040] B6) increasing the indoleacetic acid content of plants;

[0041] B7) increasing the content of corn nucleoside in plants;

[0042] B8) Promote plant growth.

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

[0044] The plant may be a young plant.

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

[0046] In the above, the plant may be any of the following:

[0047] C1) Angiosperms;

[0048] C2) Dicotyledonous plants;

[0049] C3) Cucurbitales;

[0050] C4) Cucurbitaceae;

[0051] C5) Cucumber plants;

[0052] C6) Cucumber.

[0053] The present invention studies the disease prevention and control function and the function of promoting endogenous hormone secretion of Bacillus thuringiensis ZF505 collected from potato rhizosphere soil in Zhangjiakou City, Hebei Province. Through a live pot experiment, the study found that the control effect of Bacillus thuringiensis on cucumber downy mildew can reach up to 73.01%. At the same time, Bacillus thuringiensis ZF505 can promote the increase of the content of three endogenous hormones in cucumber, among which gibberellin increased by 15.61%, indoleacetic acid increased by 5.05%, and zeaxanthin increased by 5.12%. It provides new strain resources and theoretical basis for using microorganisms for biological control and preparing biological microbial agent products.

[0054] Collection Instructions

[0055] Bacteria name: Bacillus thuringiensis

[0056] Latin name: Bacillus thuringensis

[0057] Strain ID: ZF505

[0058] Depository: China National Microbiological Culture Collection Administration General Microbiology Center

[0059] Abbreviation of depository institution: CGMCC

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

[0061] Date of deposit: March 24, 2022

[0062] CGMCC Registration Number: CGMCC No.24585 BRIEF DESCRIPTION OF THE DRAWINGS

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

[0064] Figure 2 This is the colony morphology of Bacillus thuringiensis ZF505.

[0065] Figure 3 This is the leaf morphology of cucumber infected with downy mildew.

[0066] Figure 4 These are the morphological characteristics of the sporangium stalks and sporangia of Pseudocymopara Cubanense. DETAILED DESCRIPTION

[0067] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0068] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0069] The following examples used SPSS23.0.0.0 statistical software to process the data, and used the t-test method to perform statistical difference analysis. The English letters after the numerical values ​​in each column indicate the degree of significance of the difference. There was no significant difference between treatments with the same letters at the 0.05 level, and there was a significant difference between treatments without the same letters at the 0.05 level.

[0070] The raw materials of the culture medium in the following examples are as follows:

[0071] Strain isolation and culture medium (LB medium): 10 g / L tryptone, 5 g / L yeast extract, 10 g / L sodium chloride, distilled water to 1 L. For solid culture medium, 20 g / L agar should be added.

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

[0073] Plant gibberellin (catalog number: HBDY-0125O2), auxin (catalog number: F6269-A), zeatin riboside kit (catalog number: HBDY-0124O2): purchased from Beijing Huabo Deyi Biotechnology Co., Ltd.

[0074] In the following examples, cucumber downy mildew was investigated on the whole leaf unit, and the disease classification standard was as follows:

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

[0076] Level 1: the lesion area accounts for less than 5% of the entire leaf area;

[0077] Level 3: the lesion area accounts for 6%-10% of the entire leaf area;

[0078] Level 5: the lesion area accounts for 11%-25% of the entire leaf area;

[0079] Level 7: The lesion area accounts for 26%-50% of the entire leaf area

[0080] Level 9: The lesion area accounts for more than 50% of the entire leaf area.

[0081] 4-6 days after inoculation, wait until the clear water control is fully diseased, investigate the disease condition, and calculate the control effect. Calculate the disease index and control effect according to the formula: Disease index = ∑ (number of diseased leaves at each level × relative level value) / (total number of leaves investigated × 9) × 100%.

[0082] The quantitative tests in the following examples were performed in triplicate unless otherwise specified.

[0083] Example 1 Isolation and identification of strains

[0084] 1.1 Screening and purification of strains

[0085] The rhizosphere soil of potato was collected from Zhangjiakou City, Hebei Province. 10 g of soil sample was weighed and fully suspended in 90 mL of sterile water. The sample was placed on a shaker at 37 °C and 200 rpm for 15 min to fully suspend it. After being treated in a water bath at 80 °C for 10 min, it was gradiently diluted to 10 -3 , 10 -4After concentration, 10 μL of the suspension was evenly applied to the LB plate and cultured at 30°C for 2 days. Each treatment was repeated 3 times. Bacterial strains with different morphologies were selected for purification and numbering. The colonies of strain ZF505 were disc-shaped or oval, with irregular edges and rough wrinkles ( Figure 2 ) to further identify the strain.

[0086] 2. Identification

[0087] 2.1 Molecular biological identification

[0088] The genomic DNA of strain ZF505 was extracted according to the instructions of bacterial genomic DNA extraction reagent (Tiangen Biochemical Technology (Beijing) Co., Ltd., catalog number: DP302). The genomic DNA of the strain was amplified by PCR using the 16S rDNA sequence universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') / 1492R (5'-GGTTACCTTGTTACGACTT-3'), rpoB sequence primers rpoB-F (5'-ATCGAAACGCCTGAAGGTCCAAACAT-3') / rpoB-R (5'-ACACCCTTGTTACCGTGA CGACC-3'), gyrB sequence primers gyrB-F (5'-GCTTACCAGGGAAATTGGCAG-3') / gyrB-R (5'-ATCAACGTCGGCGTCGG-3'), and groEL sequence primers groEL-F (5'-GTGCGAACCCAATGGGTCTTC-3') / groEL-R (5'-CCTTGTTGTACCACTTGCTC-3'). PCR reaction system (50 μL): 2×KeyPoMaster Mix (Dye Plus) 25 μL, upstream primer 2 μL, downstream primer 2 μL, DNA template 1 μL, ddH2O 20 μL. PCR reaction program: 98℃ pre-denaturation 5 min, 98℃ denaturation 10 s, 56℃ annealing 5 s, 72℃ extension 20 s, 35 cycles, 72℃ supplementary extension 5 min. The amplified product was sequenced by Beijing Bomed Gene Technology Co., Ltd., and the sequencing results were compared with the BLAST function of 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 was performed after splicing the three sequences (in the sequence list). It was found that strain ZF505 and Bacillus thuringensis (CP014847.1) were clustered on the same branch, and the Bootstrap support rate was 100% ( Figure 1 ).

[0090]

[0091] In sequence 1, positions 1-381 are partial sequences of the groEL gene, positions 382-1479 are partial sequences of the rpoB gene, positions 1480-1759 are partial sequences of the gyrB gene, and positions 1760-3205 are reverse complementary sequences of partial sequences 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] project reaction project reaction 1%, 4%, 8% NaCl + L-Glutamic Acid + D-Galactose + L-Histidine + sucrose + D-Aspartic Acid α-D-Glucose + L-Pyroglutamic acid - L-Alanine + L-Arginine + D-Sorbitol + D-Mannitol +

[0095] Note: + means positive; - means negative

[0096] The strain ZF505 can grow on a culture medium containing 1%-8% NaCl, with an optimum 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 and L-pyroglutamic acid (Table 1).

[0097] Bacillus thuringiensis ZF505 was deposited in the General Microbiology Center of China Microorganism Culture Collection Administration on March 24, 2022, with the deposit number CGMCC No. 24585. Hereinafter referred to as Bacillus thuringiensis CGMCC No. 24585.

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

[0099] 2.1 Preparation of Bacillus thuringiensis culture

[0100] The Bacillus thuringiensis CGMCC No.24585 stored in a -80°C cryopreservation tube was inoculated onto an LB plate by streaking with an inoculating loop and incubated at 28°C for 48 hours. A single colony of the activated strain was picked and inoculated into LB liquid culture medium and cultured at 28°C, 180 r / min, with shaking for 36 hours to obtain a Bacillus thuringiensis bacterial solution.

[0101] The Bacillus thuringiensis bacterial solution was diluted 50 times with sterile water to obtain a 50-fold bacterial solution of Bacillus thuringiensis CGMCC No. 24585 (the content of Bacillus thuringiensis CGMCC No. 24585 is 1×10 6 CFU / mL).

[0102] 2.2 Preparation of cucumber downy mildew spore suspension

[0103] The cucumber downy mildew diseased leaves were collected from the experimental field of the Institute of Vegetables and Flowers of the Chinese Academy of Agricultural Sciences. The lesions on the front of the cucumber downy mildew-infected leaves were water-soaked and faded green yellow spots. The expansion of the lesions was limited by the leaf veins and was polygonal ( Figure 3 Middle A), when humidity is high, gray-black mold grows on the lesions on the back of the leaves ( Figure 3 B). Use sterile water to clean the debris on the surface of the diseased leaves, and use sterile water containing 0.1% Tween 20 to brush the sporangium of Pseudocytin on the surface of the diseased leaves to prepare a spore suspension, which is adjusted to a concentration of 10 5 spores / ml. The spore suspension contains sporangiophores and sporangia. After the sporangia release spores, the spores are taken for microscopic examination. The morphological characteristics are that the upper part of the sporangiophore is bifurcated and can branch 3 to 6 times, and the branches at the end are slightly curved or straight; the sporangium is ovate or lemon-shaped, with a nipple-like protrusion at the top, single-celled, and light brown (see Figure 4 ). It was confirmed to be Pseudoperonospora cubensis. Store at 4℃.

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

[0105] In May 2024, a potted control effect test was conducted in the solar greenhouse of the Institute of Vegetables and Flowers of the Chinese Academy of Agricultural Sciences. Cucumber Zhongnong No. 6 seeds (purchased from China Vegetable Seed Technology (Beijing) Co., Ltd.) were sown in seedling trays and the test was conducted after the cucumbers grew two leaves and one heart. The test set up 4 treatments:

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

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

[0108] 3) Treatment with 10 billion viable bacteria / g of Bacillus thuringiensis wettable powder: Spray 10 billion viable bacteria / g of Bacillus thuringiensis wettable powder on 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 with a concentration of 10 5 spores / mL cucumber downy mildew spore suspension. Except for the different spraying drugs, other operations were exactly the same among the treatments.

[0111] Three replicates were set for each treatment, and each replicate had 15 cucumber plants.

[0112] 4-15 days after inoculation, after the clear water control is fully diseased, the disease condition is investigated and the control effect is calculated. The results are shown in Table 2 below: The control effect of 50 times bacterial solution of Bacillus thuringiensis CGMCC No.24585 on cucumber downy mildew in the first and second repeated tests was 69.31% and 72.62%, respectively, which was higher than that of chemical fungicide 50% methacryloyl morpholine wettable powder (the control effect of the first and second repeated tests was 59.28% and 52.77%, respectively) and 10 billion viable bacteria / g Bacillus thuringiensis wettable powder (the control effect of the first and second repeated tests was 68.46% and 64.50%, respectively). The control effect of 50 times of Bacillus thuringiensis CGMCC No.24585 on cucumber downy mildew in the third repeated test was 55.29%, which was higher than 10 billion viable bacteria / g Bacillus thuringiensis wettable powder (control effect 37.53%), and slightly lower than the chemical fungicide 50% methacryloyl methacrylate wettable powder (control effect 56.18%). In summary, the control effect of 50 times of Bacillus thuringiensis CGMCC No.24585 on cucumber downy mildew was good and the efficacy was stable.

[0113] Table 2 Control effect of 50 times of Bacillus thuringiensis CGMCC No.24585 on cucumber downy mildew

[0114]

[0115] Example 3 Evaluation of the effect of 50-fold bacterial suspension of Bacillus thuringiensis CGMCC No.24585 on the endogenous hormone level of cucumber

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

[0117] The Bacillus thuringiensis CGMCC No. 24585 stored in a -80°C cryotube was inoculated onto an LB plate by streaking with an inoculating loop and cultured in a 28°C incubator for 48 hours. A single colony of the activated strain was picked and inoculated into LB liquid culture medium and cultured at 28°C, 180 r / min, with shaking for 36 hours.

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

[0119] The plant hormone kit of Beijing Huabo Deyi Biotechnology Co., Ltd. was used to determine the content of endogenous plant hormones gibberellin (GA3), indoleacetic acid (IAA) and zeatin riboside (ZR) in cucumber leaves. The specific steps were carried out according to the instructions for use of the kit. Three replicates were set for each treatment. Each replicate had 15 cucumber plants.

[0120] After spraying Bacillus thuringiensis CGMCC No.24585 solution, the contents of endogenous hormones in cucumber leaves increased significantly, among which gibberellin increased by 15.61%, indoleacetic acid increased by 5.05%, and zeaxanthin increased by 5.12% (Table 3).

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

[0122] deal with Gibberellic acid (ng / g) Indoleacetic acid (μg / g) Corn nucleoside (μg / g) CGMCC No.24585 5.68±0.084a 15.92±0.26a 1.64±0.03a No 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 effects of Bacillus thuringiensis CGMCC No. 24585 and similar biocontrol agents on the prevention and treatment of cucumber downy mildew

[0124] In order to evaluate the difference between Bacillus thuringiensis CGMCC No.24585 and similar biocontrol agents in controlling cucumber downy mildew, a pot experiment was used to evaluate and compare the 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 multiples in Table 4 and used in the same way as Bacillus thuringiensis CGMCC No.24585. The leaves were sprayed with water after inoculation with pathogens as the water control, and the leaves were sprayed with water only without inoculation with pathogens as the healthy control. After 24 hours of spraying, all treatments were sprayed with 10 5 spores / mL of cucumber downy mildew spore suspension. The preparation of the cucumber downy mildew spore suspension refers to 2.2 in Example 2.

[0126] Table 4 Treatments and sources of test materials

[0127] serial number deal with Use concentration Production Company 1 Bacillus thuringiensis CGMCC No.24585 bacterial liquid 50 times liquid This patented bacterial liquid 2 500 million spores / g Pseudomonas fluorescens wettable powder 1000 times liquid Shandong Tainuo Pharmaceutical Co., Ltd. 3 10 billion spores / g Bacillus subtilis wettable powder 500 times liquid Shandong Weifang Double Star Pesticide Co., Ltd. 4 1 billion CFU / g Bacillus amyloliquefaciens WP 500 times liquid Jiangsu Subin Bio-Agrochemical Co., Ltd. 5 50% Dimethomorph WP 1000 times liquid Shandong Keda Chuangye Biological Co., Ltd. 6 Inoculate only pathogens - - 7 Healthy control (no pathogen inoculation, only spraying water) - -

[0128] The potted plant test showed (Table 5) that the control effect of Bacillus thuringiensis CGMCC No.24585 was 43.64%, only lower than the chemical fungicide 50% methoxymorph wettable powder (control effect 49.04%), the same as the control effect of 500 million spores / g Pseudomonas fluorescens wettable powder (control effect 43.64%), and higher than other similar biocontrol agents: 10 billion spores / g Bacillus subtilis wettable powder (control effect 35.47%) and 1 billion CFU / g Bacillus amyloliquefaciens wettable powder (control effect 34.97%), which has broad commercial prospects in the control of cucumber downy mildew.

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

[0130] serial number deal with Use concentration Disease index Control effect / % 1 Bacillus thuringiensis CGMCC No.24585 bacterial liquid 50 times liquid 37.78 43.64 2 500 million spores / g Pseudomonas fluorescens wettable powder 1000 times liquid 37.78 43.64 3 10 billion spores / g Bacillus subtilis wettable powder 500 times liquid 43.25 35.47 4 1 billion CFU / g Bacillus amyloliquefaciens WP 500 times liquid 43.59 34.97 5 50% Dimethomorph WP 1000 times liquid 34.16 49.04 6 Inoculate only pathogens - 67.03 - 7 Healthy control (no pathogen inoculation, only spraying water) - 0.00 -

[0131] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principles of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departure from the disclosed scope in the application, and changes made with conventional techniques known in the art.

Claims

1. Bacillus thuringiensis, characterized in that: The Bacillus thuringiensis is Bacillus thuringensis ZF505, and its deposit number in the General Microbiological Center of China Microbiological Collection Administration is CGMCC No.24585.

2. A composition, characterized in that The composition contains the Bacillus thuringiensis according to claim 1.

3. The composition according to claim 2, characterized in that: The composition is a culture, and the culture is a substance obtained by culturing the Bacillus thuringiensis in a microbial culture medium.

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

5. A composition according to any one of claims 2 to 4, characterized in that The composition is any one of the following: A1) A composition for controlling cucumber downy mildew; A2) Compositions as pathogen inhibitors; A3) Compositions as disease inhibitors; A4) a composition for increasing the content of endogenous hormones in plants; A5) a composition for increasing the content of gibberellins in plants; A6) A composition for increasing the indoleacetic acid content of a plant; A7) A composition for increasing the content of zea mays nucleoside in plants; A8) Compositions for promoting plant growth.

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

7. Use of the Bacillus thuringiensis according to claim 1 or the composition according to claims 2 to 5 in preparing a product.

8. The product according to claim 7, characterized in that The product has at least one of the following properties: B1) Used to control cucumber downy mildew; B2) as an inhibitor of pathogens; B3) as a disease inhibitor; B4) Increase the content of endogenous hormones in plants; B5) Increase the content of gibberellins in plants; B6) increasing the indoleacetic acid content of plants; B7) increasing the content of corn nucleoside in plants; B8) Promote plant growth.

9. A method for preventing and controlling plant downy mildew and / or increasing the level of endogenous hormones in plants, characterized in that: The method comprises contacting the Bacillus thuringiensis according to claim 1 or the composition according to claims 2 to 5 with plants to prevent and control plant downy mildew and / or increase the level of endogenous hormones in plants.

10. The composition according to claim 5, the product according to claim 8, or the method according to claim 9, characterized in that: The plant is any one of the following: C1) Angiosperms; C2) Dicotyledonous plants; C3) Cucurbitales; C4) Cucurbitaceae; C5) Cucumber plants; C6) Cucumber.

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