Streptomyces pralactiae and application thereof in prevention and treatment of stem rot of dendrobium officinale kimura et migo

Abstract

The invention discloses streptomyces pralaticus and application thereof in prevention and treatment of stem rot of dendrobium officinale, and belongs to the technical field of microorganisms. The classification name of the Streptomyces pratensis is Streptomyces pratensis, the Streptomyces pratensis is preserved in China General Microbiological Culture Collection Center, the preservation address is Institute of Microbiology, Chinese Academy of Sciences, No.3, No.1 Yard, West Beichen Road, Chaoyang District, Beijing, the preservation name of the Streptomyces pratensis is MEPP0209, the preservation number is CGMCC No.32171, and the preservation date is October 11, 2024. The Streptomyces pralaticus MEPP0209 can obviously inhibit the growth of pathogenic bacteria of the stem rot of Dendrobium officinale, obviously reduces the pathogenic index of the stem rot of Dendrobium officinale, does not affect the quality of the medicinal material Dendrobium officinale, and avoids the problems of environmental pollution caused by pesticide abuse, threat of pesticide residues to human health and drug resistance of pathogenic bacteria.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and particularly relates to a strain of Streptomyces prattii and application thereof in the prevention and treatment of stem rot of Dendrobium officinale. Background Art

[0002] Dendrobium officinale Kimura et Migo, also known as black knot grass, is a perennial herbaceous plant of the genus Dendrobium in the orchid family. It grows on cliffs and rocks or trunks in dense forests at an altitude of 800-1600 meters. Dendrobium officinale is a traditional precious Chinese medicinal material. It is known as the "life-saving fairy grass" among the people and enjoys the reputation of being the first of the "Nine Fairy Grasses in China". It is mainly distributed in Yunnan, Guangxi, Fujian, Guizhou, Zhejiang and other places in my country. Modern pharmacological studies have shown that Dendrobium officinale contains a variety of chemical components such as polysaccharides, flavonoids, alkaloids, phenols, terpenes, etc., and has multiple pharmacological effects such as lowering blood sugar, lowering blood lipids, anti-oxidation, antibacterial, anti-tumor and enhancing immunity. Due to its extremely high medicinal value and economic value, the phenomenon of over-exploitation of Dendrobium officinale is extremely serious. In addition, its low reproduction rate and slow growth under natural conditions have caused the wild resources of Dendrobium officinale to be on the verge of exhaustion. In order to meet the market supply demand, artificial cultivation has become an effective shortcut to solve this problem. However, the quality of artificially cultivated Dendrobium officinale products is uneven. And artificially cultivated Dendrobium officinale is susceptible to diseases. At present, the main diseases of artificially cultivated Dendrobium officinale are stem rot, white rot, soft rot, black spot, and anthracnose. Among them, stem rot is a common disease in the cultivation process of Dendrobium officinale, which directly threatens the industrial development of Dendrobium officinale. Therefore, how to use effective biological methods that effectively inhibit pathogens, are green, environmentally friendly, healthy and sustainable to improve quality and increase quantity has become a new direction for Dendrobium officinale research.

[0003] Different climatic conditions, regional environments, and cultivation methods will cause different types of pathogens of stem rot in Dendrobium officinale. The pathogens that cause stem rot are generally Fusarium oxysporum and Lasiodiplodia theobromae. The symptoms of stem rot in Dendrobium officinale are that the leaves lose their green color and turn yellow and water-soaked spots appear when the plant is infected. As time goes by, water-soaked spots appear on the stems. In severe cases, the leaves wither and fall off, the stems wilt and wither, and white aerial hyphae can be seen at the diseased site, and eventually the whole plant withers and dies. The pathogen Lasiodiplodia theobromae can cause water-soaked necrotic spots on the stems, with a diameter of about 3 mm, and the symptoms are similar to those of natural disease. At present, the methods for preventing and controlling stem rot in Dendrobium officinale mainly rely on chemical fungicides, but since chemical control is prone to excessive pesticide residues, environmental pollution, and pathogen resistance, it is urgent to seek green control methods for stem rot in Dendrobium officinale.

[0004] Biological control is an effective means to achieve green control of plant diseases. The premise of implementing biological control is to find beneficial microorganisms that have antagonistic effects on pathogens. The key to biological control is the screening of biocontrol bacteria. Plant endophytes refer to microorganisms that coexist in plant tissues without causing any disease symptoms. They are widely present in the roots, stems, leaves, flowers and fruits of host plants. Zhang Qingming et al. isolated a strain of Streptomyces caulerii from healthy apple branches, which has a good control effect on apple tree rot. Zhang Jingjing et al. screened a strain of Pseudomonas from walnut soil, which has a good antagonistic effect on walnut rot bacteria. YongJing Zhang et al. isolated a strain of Streptomyces jakarta from sweet potatoes, which can effectively inhibit sweet potato black spot disease. However, there are few reports on the application of endophytic biocontrol bacteria in treating stem rot of Dendrobium officinale. Therefore, using endophytic bacteria of Dendrobium plants as an entry point to screen out functional strains that are highly effective in antagonizing the pathogens of stem rot of Dendrobium officinale is of great significance to the development of the medicinal plant Dendrobium industrialization and the safety of the use of Dendrobium as a traditional Chinese medicine. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the prior art, the purpose of the present invention is to provide a strain of Streptomyces pratense and its application in the prevention and treatment of stem rot of Dendrobium officinale. The strain can effectively inhibit Diplodia sphaeroides on Dendrobium officinale, and can prevent and treat the stem rot of Dendrobium officinale for a long time, which has practical significance for the cultivation of Dendrobium officinale.

[0006] Technical solution: In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0007] A strain of Streptomyces platensis, the classification name of the Streptomyces platensis is Streptomyces platensis, the preservation unit is the General Microbiology Center of the China Culture Collection Administration, the preservation address is the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, the strain preservation name is: MEPP0209, the preservation number is: CGMCCNo.32171, and the preservation date is October 11, 2024.

[0008] Furthermore, the 16S rRNA gene sequence of the strain is shown in SEQ ID NO:1.

[0009] The invention discloses an application of Streptomyces platensis, which is used to prepare a method for preventing and treating stem rot of Dendrobium officinale.

[0010] Furthermore, Streptomyces platensis is used in the form of bacterial suspension or cell-free fermentation filtrate.

[0011] Furthermore, the bacterial suspension or the cell-free fermentation filtrate is sprayed on the Dendrobium officinale to inhibit the Diplodia theobroma cacao on the Dendrobium officinale.

[0012] Further, Streptomyces platensis was taken and, under sterile conditions, the bacteria were inoculated into sterilized ISP2 liquid culture medium and transferred to a shaking incubator shaker at 28°C and 180 rpm for dark culture for 7 days; after centrifugation at 12000 r / min for 10 min, the bacterial precipitate was taken and sterile water was added to adjust the concentration of the bacterial suspension to OD 600 =1.0.

[0013] Further, the strain of Streptomyces prausnitzii MEPP0209 was taken, and under sterile conditions, the bacteria were inoculated into the sterilized ISP2 liquid culture medium, and transferred to a shaking incubator shaker at 28°C and 180rpm for dark culture for 7 days; then, after centrifugation at 12000r / min for 10min, the supernatant was taken, and under sterile conditions, the supernatant was filtered and sterilized through a 0.22μm filter membrane to prepare a cell-free fermentation filtrate.

[0014] A microbial composition comprises Streptomyces platensis.

[0015] In the early stage, the inventors isolated 43 endophytes from the roots, stems and leaves of wild Dendrobium officinale, and then used the plate confrontation test to conduct screening experiments. It was found that the endophytes of Dendrobium officinale had a significant inhibitory effect on the pathogen of stem rot (Diplodia theobroma cacao). Subsequently, the endophytes were further purified and identified to obtain Streptomyces platensis MEPP0209, which can effectively prevent and control the stem rot of Dendrobium officinale.

[0016] The present invention has the beneficial effects that the Streptomyces pratense MEPP0209 provided by the present invention can effectively inhibit the pathogenic bacteria of stem rot of Dendrobium officinale, can be used for biological control of stem rot of Dendrobium officinale, and reduce the occurrence of stem rot during artificial cultivation of Dendrobium officinale; in addition, the method provided by the present invention belongs to the field of biological control, and the plant endophytes can stably colonize in the plant body, can enhance the disease resistance of the plant, and will not have an adverse effect on the quality of Dendrobium officinale medicinal materials, effectively avoid the problems of excessive pesticide residues, environmental pollution, pathogen resistance, etc. caused by chemical control methods, and is more green and environmentally friendly, can ensure the safety of the use of Dendrobium officinale medicinal materials, and has broad application prospects in the prevention and control of Dendrobium officinale diseases. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1The morphological characteristics of strain MEPP0209 in Example 1 of the present invention are shown in Figure 1. Figure A shows the colony morphology after culturing on an ISP2 plate for 4 days; Figure B shows the hyphae morphology under a scanning electron microscope.

[0018] Figure 2 Part of the physiological and biochemical characteristics of strain MEPP0209 in Example 1 of the present invention: In the figure: A phosphate-solubilizing ability, B amylase-producing ability, C iron carrier-producing ability, D cellulase-hydrolyzing ability, E urease-producing ability, F ACC deaminase-producing ability, G oxidase-producing ability, H protease-producing ability, I nitrogen-fixing ability, J gelatin-liquefying ability, K glucose fermentation, L xylose fermentation, MV-P reaction.

[0019] Figure 3 The figure shows the antagonistic effect of strain MEPP0209 in Example 1 of the present invention on stem rot pathogens on a plate. Figure A is the control group of the plate confrontation experiment, Figure B is the experimental group of the plate confrontation experiment, and Figure C is the diameter of the stem rot pathogens in the control group and the experimental group.

[0020] Figure 4 This is a phylogenetic tree constructed based on the 16S rRNA gene sequence of strain MEPP0209 in Example 1 of the present invention.

[0021] Figure 5 This is a graph showing the inhibitory effect of the cell-free fermentation filtrates of strain MEPP0209 with different gradients on the stem rot pathogen of Dendrobium officinale in Example 2 of the present invention.

[0022] Figure 6 It is the inhibition rate of stem rot of Dendrobium officinale treated with cell-free fermentation filtrates of strain MEPP0209 at different gradients in Example 2 of the present invention.

[0023] Figure 7 This is a diagram showing the biological control effect of strain MEPP0209 on stem rot of Dendrobium officinale in Example 4 of the present invention; Figure A is a sterile water treatment; Figure B is a MEPP0209 cell-free fermentation filtrate treatment; Figure C is a MEPP0209 bacterial suspension treatment. DETAILED DESCRIPTION

[0024] The present invention is further described by the following examples. These examples are purely illustrative and are only used to specifically describe the present invention and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0026] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0027] A strain of Streptomyces platensis MEPP0209 and its application in the prevention and treatment of stem rot of Dendrobium officinale.

[0028] The Streptomyces platensis MEPP0209 has a deposit number of 32171 and a deposit date of October 11, 2024. The depository unit is the General Microbiology Center (CGMCC) of the China Microbiological Culture Collection Administration, and the address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0029] The second object of the present invention is to provide the use of the above-mentioned Streptomyces platensis MEPP0209 in preventing and controlling stem rot pathogens.

[0030] In one example of the present invention, the Streptomyces platensis MEPP0209 can be applied in the form of bacterial suspension or cell-free fermentation filtrate.

[0031] Preferably, the preparation method of the Streptomyces prausnitzii MEPP0209 bacterial suspension is:

[0032] Take the strain of Streptomyces pratense MEPP0209, pick up a small amount of bacteria with a bamboo stick under sterile conditions (try to avoid agar), inoculate it into the sterilized ISP2 liquid culture medium, and culture it in a dark shaker at 28°C and 180rpm for 7 days; after centrifugation at 12000r / min for 10min, take the bacterial precipitate, add sterile water to adjust the concentration of the bacterial suspension to OD 600 =1.0, that is;

[0033] Preferably, the preparation method of the cell-free fermentation filtrate of Streptomyces prausnitzii MEPP0209 is:

[0034] Take the strain of Streptomyces prausnitzii MEPP0209, pick up a small amount of bacteria with a bamboo stick under sterile conditions, inoculate it into the sterilized ISP2 liquid culture medium, and culture it in a shaker at 28°C and 180rpm in the dark for 7 days; after centrifugation at 12000r / min for 10min, take the supernatant, and filter and sterilize the supernatant through a 0.22μm filter membrane under sterile conditions to prepare a cell-free fermentation filtrate.

[0035] The third object of the present invention is to provide the use of the above-mentioned Streptomyces platensis MEPP0209 in the preparation of a product for preventing and controlling stem rot of Dendrobium officinale.

[0036] A fourth aspect of the present invention is to provide a microbial preparation, the active ingredient of which is the above-mentioned Streptomyces platensis MEPP0209.

[0037] In the early stage, the inventors isolated 43 endophytes from the roots, stems and leaves of wild Dendrobium candidum, and then used the plate confrontation test to conduct a screening experiment. It was found that one of the endophytes had a significant inhibitory effect on the stem rot pathogen (Diplodia theobroma cacao). Subsequently, the endophyte was further purified and identified to obtain Streptomyces platensis MEPP0209.

[0038] Example 1

[0039] Isolation, Screening and Identification of Streptomyces platensis MEPP0209

[0040] 1. Isolation of endophytes from wild Dendrobium candidum

[0041] The endophyte MEPP0209 of the present invention is a strain isolated from wild Dendrobium candidum collected from Jinxiu Yao Autonomous County, Guangxi. The specific steps include: (1) removing roots, stems and leaves from wild Dendrobium candidum, repeatedly rinsing them under tap water, and then absorbing the moisture with absorbent paper. In a clean bench, first soak the leaves, stems and roots in 75% ethanol for 30s, 60s and 80s respectively, then rinse them with sterile water twice, and then soak them in 2% sodium hypochlorite for 8min, 12min and 15min respectively, rinse them with sterile water 5 times, and absorb the moisture with filter paper for later use. The sterile water after the last washing is applied to the ISP2 solid culture medium, cultured at 28°C for one week, and observing whether there is colony growth to verify whether the surface is thoroughly disinfected to ensure that the colonies grown on the plate are all endophytes of Dendrobium candidum. (2) Take 0.1 g of the surface-sterilized roots, stems, and leaves, put them in a mortar, add 900 μL of sterile water, grind them into a homogenate, and prepare a tissue stock solution. Take a certain amount of the root stock solution and prepare a dilution gradient of 10 -1 , 10 -2 Take 100 μL of root dilution, 10 μL of stem and leaf dilution, and 10 μL of root dilution. -1 , 10 -2The dilution was spread on the center of the surface of the ISP2 solid culture medium and cultured in the dark at 28°C for 3-5 days. A single colony grown on the ISP2 plate was picked and inoculated on the same solid culture medium (ISP2) for four-zone line purification. After repeated purification and cultivation, the endophytic strain MEPP0209 of the present invention was finally obtained. Figure 1 As shown in A, the colony is white, round, and opaque as a whole, and changes to mouse-gray with black spots over time. The strain was preserved in a -80℃ refrigerator using the glycerol preservation method.

[0042] 2. Plate confrontation test between endophytes of wild Dendrobium candidum and stem rot pathogens

[0043] The test pathogen was Diplosporus cocosus isolated from Dendrobium officinale suffering from stem rot in the inventor's laboratory.

[0044] First, under sterile conditions, a 200μL sterilized pipette tip was used to make a 6mm cake of the pathogen of stem rot, and the pathogen cake was transferred to the center of the PDA culture dish. Then, the MEPP0209 strain was inoculated at a position 2.5cm away from both sides of the pathogen cake, and repeated for 3 dishes; in the control group, only the pathogen of Dendrobium officinale stem rot was inoculated without endophytes, and repeated for 3 dishes. Cultured in the dark at 28℃ for 3 days, the colony diameters of the pathogens in the control group and the experimental group were measured using the cross method. Finally, the inhibition rate was calculated according to the following formula: Inhibition rate (%) = [(colony diameter of the control group - colony diameter of the treatment group) / colony diameter of the control group] × 100. The results are shown in the attached figure. Figure 3 As shown, Figure 3 A is the control group inoculated with pathogens alone; Figure 3 B is the experimental group inoculated with strain MEPP0209 and pathogens, Figure 3 C is the diameter of the stem rot pathogen in the control group and the experimental group. The results showed that strain MEPP0209 had a significant inhibitory effect on the growth of stem rot pathogens on the plate, and its inhibition rate on the stem rot pathogen of Dendrobium officinale was 91%.

[0045] 3. Identification of strain MEPP0209

[0046] (1) Morphological characteristics of strains:

[0047] The purified strain MEPP0209 grew well on ISP2 solid medium. The colonies were white, round, and opaque, and changed to mouse-gray with black spots over time. Figure 1 As shown in A, Gram staining is positive. Strain MEPP0209 was observed under a scanning electron microscope. Its mycelium is slender, the spores are short, and the spore chains are spiral, as shown in Figure 1 As shown in B.

[0048] (2) Physiological and biochemical characteristics of strains

[0049] The nitrogen fixation reaction, siderophore production reaction, amylase production reaction, ACC dehydrogenase production reaction, phosphate solubilization reaction, starch hydrolysis, urease, and gelatin hydrolysis reaction of strain MEPP0209 were all positive, while the oxidase reaction, cellulase production reaction, protease production reaction, glucose fermentation, VP reaction, and xylose fermentation were all negative, as shown in Table 1. The specific test results are as follows Figure 2 shown.

[0050] Table 1 Some physiological and biochemical characteristics of strain MEPP0209

[0051]

[0052] (3) Phylogenetic analysis of strain MEPP0209 based on 16S rRNA gene:

[0053] The total DNA of strain MEPP0209 obtained by separation and screening was extracted using the Novozymes bacterial extraction kit.

[0054] 16S rDNA gene PCR amplification:

[0055] Forward Prime A: 5'-CAGAGTTTGATCCTGGCT-3' (base 7 to 24 of E. coli),

[0056] Reverse Prime B: 5'-AGGAGGTGATCCAGCCGCA-3) (bases 1540 to 1522 of E. coli),

[0057] The amplification system (components / reaction volume) was Premix Taq / 12.5 μL, Prime A / 0.5 μL, Prime B / 0.5 μL, DNA template / 0.5 μL, and sterile distilled water ddH2O / 12.5 μL.

[0058] PCR amplification reaction conditions: pre-denaturation at 95°C for 5 min; denaturation at 95°C for 30 s, annealing at 54°C for 30 s, extension at 72°C for 1 min 45 s, 30 cycles, and total extension at 72°C for 10 min.

[0059] The amplified products were detected by 1% agarose gel electrophoresis at 135 V for 25 min.

[0060] The PCR products were sent to Nanjing Branch of Sangon Biotech (Shanghai) Co., Ltd. for sequencing, and the obtained sequences were compared with the NCBI database. Then, based on the homologous sequences of 16 other Streptomyces, a phylogenetic tree was constructed using MEGA11.0 software, as shown in Figure 4 shown.

[0061] The 16S rRNA gene sequence of strain MEPP0209 is shown in SEQ ID NO:1.

[0062] The results of the constructed phylogenetic tree showed that strain MEPP0209 and Streptomyces platensis were clustered into one branch with a support of 98%. Combining morphological characteristics and molecular methods, strain MEPP0209 was identified as Streptomyces platensis.

[0063] Example 2

[0064] Effects of cell-free fermentation filtrate of strain MEPP0209 on the growth of stem rot pathogen

[0065] The activated strain MEPP0209 was inoculated into a triangular flask containing 200 mL ISP2 liquid culture medium and shake-cultured at 28°C and 180 r / min. After 7 days of shaking culture, the fermentation liquid of strain MEPP0209 was filtered and the supernatant was filtered with a 0.22 μm microporous filter membrane. The obtained filtrate was the cell-free fermentation filtrate. The fermentation filtrate was added to the PDA culture medium in proportion to make the final volume 200 mL to make a poisonous plate, and then a pathogenic fungus cake with a diameter of 6 mm was inoculated in the center of the plate. Ordinary PDA culture medium inoculated with only pathogens was used as the control. Three replicates were set for each treatment and cultured in a constant temperature incubator at 28°C. When the control covered the entire plate, the colony diameter was measured by the cross method, and the inhibition rate of 10%, 20%, 30%, 40%, and 50% of the cell-free fermentation filtrate of Streptomyces pratense MEPP0209 against the pathogen of Dendrobium officinale stem rot was calculated. The inhibition rate calculation results are shown as follows Figure 6 Inhibition rate (%) = [(colony diameter of control group - colony diameter of treatment group) / colony diameter of control group] × 100.

[0066] The results showed that the cell-free fermentation filtrate of strain MEPP0209 had a significant inhibitory effect on the growth of the pathogenic bacteria of Dendrobium officinale stem rot. Figure 5 , Figure 6 shown.

[0067] Example 3

[0068] Biological Control of Stem Rot of Dendrobium officinale by Strain MEPP0209

[0069] After strain MEPP0209 was selected and fermented in ISP2 liquid medium for 7 days, it was centrifuged at 12000r / min for 10min, and the supernatant was filtered through a 0.22μm filter membrane to obtain the cell-free fermentation filtrate for use. The precipitated bacteria were diluted with sterile water to OD 600=1.0 and then prepare the bacterial suspension for use. Take the sterile seedlings of Dendrobium officinale with relatively consistent growth status (≥4 leaves per plant) and divide them into three groups, with no less than 10 plants in each group. The three groups of sterile seedlings of Dendrobium officinale were first inoculated with mycelial plugs of pathogenic bacteria, and then sprayed with equal amounts of sterile water ( Figure 7 A), MEPP0209 cell-free fermentation filtrate ( Figure 7 B) MEPP0209 bacterial suspension ( Figure 7 C). After 7 days, the pathogenicity index of sterile seedlings of Dendrobium officinale in each group was counted. This experiment was repeated three times. The grading standard of pathogenicity index of Dendrobium officinale stem rot pathogens is shown in Table 2.

[0070] Table 2 Pathogenicity index grading standard of Dendrobium officinale stem rot pathogens

[0071]

[0072] Incidence rate (%) = (number of diseased plants / total number of plants) × 10

[0073] Pathogenicity index = ∑ (number of diseased plants at each level × representative value at each level) × 100 / (total number of plants surveyed × highest representative value)

[0074] Control effect (%) = [(control disease index - treatment disease index) / control disease index] × 100

[0075] Table 3 Biological control effect of strain MEPP0209 on stem rot of Dendrobium officinale

[0076]

[0077] The results are shown in Table 3 and Figure 7 As shown: the pathogenicity index of the sterile water treatment (control group) was 95.33±3.712, the pathogenicity index of the cell-free fermentation filtrate treatment group was 16.00±2.000, and the pathogenicity index of the bacterial suspension treatment group was 12.00±1.732, indicating that the strain MEPP0209 has a good biological control effect on Dendrobium officinale stem rot.

[0078] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A strain of Streptomyces prausnitzii, characterized in that: The taxonomic name of the Streptomyces prauti is Streptomyces prauti. Streptomyces platensis ), the depository is the General Microbiology Center of China Microbiological Culture Collection Administration, and the deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The strain deposit name is: MEPP0209, the deposit number is: CGMCCNo.32171, and the deposit date is October 11, 2024.

2. The Streptomyces prausnitzii according to claim 1, characterized in that: The 16S rRNA gene sequence of the strain is shown in SEQ ID NO:

1.

3. An application of Streptomyces prausnitzii according to claim 1, characterized in that: Using Streptomyces prausnitzii ( Streptomyces platensis ) Prevent and control stem rot of Dendrobium officinale.

4. The use of Streptomyces prausnitzii according to claim 3, characterized in that: Streptomyces prausnitzii ( Streptomyces platensis ) The application form for preventing and controlling stem rot of Dendrobium officinale is bacterial suspension or cell-free fermentation filtrate.

5. The use of Streptomyces prausnitzii according to claim 4, characterized in that: The bacterial suspension or the cell-free fermentation filtrate is sprayed on the Dendrobium officinale to inhibit the Diplodia theobroma cacao on the Dendrobium officinale.

6. A method for preparing the Streptomyces prausnitzii suspension according to claim 4, characterized in that: Take Streptomyces prausnitzii ( Streptomyces platensis ), under sterile conditions, the bacteria were inoculated into the sterilized ISP2 liquid culture medium, and then transferred to a shaking incubator shaker at 28°C and 180 rpm for dark culture for 7 days; after centrifugation at 12000 r / min for 10 min, the bacterial precipitate was taken, and sterile water was added to adjust the concentration of the bacterial suspension to OD 600 =1.

0.

7. A method for preparing the cell-free fermentation filtrate of Streptomyces prausnitzii according to claim 4, characterized in that: Take the strain of Streptomyces prausnitzii MEPP0209, and under sterile conditions, inoculate the bacteria into the sterilized ISP2 liquid culture medium, transfer it to a shaking incubator shaker at 28°C and 180rpm for dark culture for 7 days; then centrifuge it at 12000r / min for 10min, take the supernatant, and filter and sterilize the supernatant through a 0.22μm filter membrane under sterile conditions to prepare a cell-free fermentation filtrate.

8. A microbial composition comprising the Streptomyces prausnitzii according to claim 1 ( Streptomyces platensis ).

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