A strain of Streptomyces noursei S83, biological preparation and application thereof

Abstract

The present invention relates to the field of microorganisms, and in particular to a strain of Streptomyces noursii S83, a biological agent and its application. In view of the occurrence of common tobacco diseases, the present invention isolates and screens a strain of Streptomyces noursii S83 that effectively prevents and treats tobacco target spot disease, and its preservation number is CGMCC No.31252. The present invention evaluates its application performance in a specific embodiment, and it is found that it has a preventive effect on diseases such as tobacco target spot disease, rice sheath blight, rice blast and wheat stem base rot, and the preventive effect on tobacco target spot disease reaches 52.8%; at the same time, it can also promote the growth of tobacco. It can be seen that the Streptomyces noursii S83 provided by the present invention is a multifunctional strain, and the present invention provides strong support for the green prevention and control of plant diseases such as tobacco.

Description

Technical Field

[0001] The invention relates to the field of microorganisms, and in particular to a strain of Streptomyces noursei S83, a biological preparation and applications thereof. Background Art

[0002] Tobacco target spot mainly harms tobacco leaves, causing leaf spots. The pathogen is Rhizoctonia solani Kühn. The disease mainly occurs in the vigorous growth and maturity stages of tobacco. It is a new domestic tobacco disease with a short incubation period and rapid epidemicity, and the disease has been reported abroad. The current control method for tobacco target spot is mainly chemical control, but chemical control has problems such as environmental pollution, human health hazards and pesticide residues. Therefore, it is very important to develop high-efficiency, low-toxicity, low-residue and pollution-free biological pesticides.

[0003] Streptomyces is a Gram-positive bacterium with a complex life cycle and morphological characteristics, and is widely found in nature. During the process of morphological differentiation, Streptomyces can metabolize and produce a wide variety of secondary metabolites. 70%-80% of the antibiotics discovered so far are produced by Streptomyces. Therefore, Streptomyces has also become an important microbial resource and is known as the "natural drug synthesis factory." Streptomyces secondary metabolites can not only promote plant development and enhance their resistance to adversity, but also metabolize to produce lysozyme that directly acts on the cell membrane and cell wall of pathogens, playing an important role in plant diseases. Therefore, finding new Streptomyces to treat tobacco target spot disease can effectively enrich the ways to prevent and control tobacco target spot disease. Summary of the invention

[0004] The purpose of the present invention is to provide a strain of Streptomyces noursei S83, a biological agent and its application to solve the problems existing in the above-mentioned prior art. The Streptomyces noursei S83 provided by the present invention can effectively prevent and treat tobacco target spot disease and also has the effect of promoting plant growth.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a strain of Streptomyces noursei S83, and the deposit number of the Streptomyces noursei S83 is CGMCC No.31252.

[0007] In the specific examples of the present invention, the application performance of Streptomyces noursei S83 was evaluated, and it was found that it has a preventive effect on diseases such as tobacco target spot, rice sheath blight, rice blast and wheat stem base rot, and the preventive effect on tobacco target spot reached 52.8%; at the same time, it can also promote the growth of tobacco. Therefore, the strain and its fermentation liquid can be used to prepare biological preparations for preventing and controlling plant diseases and / or promoting tobacco growth.

[0008] The present invention provides the use of the above-mentioned Streptomyces noursei S83 in preparing a biological agent for preventing and controlling plant diseases, wherein the plant diseases include one or more of tobacco target spot disease, rice sheath blight, rice blast and wheat stem base rot.

[0009] The present invention provides a biological preparation for preventing and controlling plant diseases, wherein the biological preparation comprises the above-mentioned Streptomyces noursei S83 or the fermentation liquid of the Streptomyces noursei S83; the plant diseases comprise one or more of tobacco target spot disease, rice sheath blight, rice blast and wheat stem base rot.

[0010] Preferably, the method for preparing the fermentation broth comprises the step of inoculating the Streptomyces noursei S83 into a fermentation medium for fermentation culture to obtain the fermentation broth.

[0011] Preferably, the fermentation medium comprises 20 g soybean powder, 30 g corn powder, 20 g glucose, 4 g sodium chloride, 3 g calcium carbonate and 1 L water.

[0012] Preferably, the inoculation amount of the Streptomyces noursei S83 is 1%; the temperature of the fermentation culture is 28° C., the rotation speed is 220 rpm, and the time is 72 h.

[0013] The present invention provides the use of the above-mentioned Streptomyces noursei S83 or the above-mentioned biological agent in preventing and controlling plant diseases, wherein the plant diseases include one or more of tobacco target spot disease, rice sheath blight, rice blast and wheat stem base rot.

[0014] The present invention provides a method for preventing and controlling plant diseases, comprising the following steps:

[0015] Spray the above biological preparation on the plant surface;

[0016] The plant diseases include one or more of tobacco target spot, rice sheath blight, rice blast and wheat stem rot.

[0017] The present invention provides the use of the above-mentioned Streptomyces noursei S83 in preparing a biological preparation for promoting tobacco growth.

[0018] The present invention provides a biological preparation for promoting tobacco growth. The biological preparation comprises the above-mentioned Streptomyces noursei S83 or the fermentation liquid of the Streptomyces noursei S83.

[0019] Further preferably, the method for preparing the fermentation broth comprises the step of inoculating the Streptomyces noursei S83 into a fermentation medium for fermentation culture to obtain the fermentation broth.

[0020] Further preferably, the fermentation medium comprises 20 g soybean powder, 30 g corn powder, 20 g glucose, 4 g sodium chloride, 3 g calcium carbonate and 1 L water.

[0021] Further preferably, the inoculation amount of the Streptomyces noursei S83 is 1%; the temperature of the fermentation culture is 28° C., the rotation speed is 220 rpm, and the time is 72 h.

[0022] The present invention discloses the following technical effects:

[0023] In view of the occurrence of common tobacco diseases, the present invention has isolated and screened a strain of Streptomyces noursei S83 that effectively prevents and treats tobacco target spot disease, and its deposit number is CGMCC No.31252. The present invention evaluated its application performance in a specific embodiment, and found that it has a preventive effect on diseases such as tobacco target spot disease, rice sheath blight, rice blast and wheat stem base rot, and the preventive effect on tobacco target spot disease reached 52.8%; at the same time, it can also promote the growth of tobacco. It can be seen that the Streptomyces noursei S83 provided by the present invention is a multifunctional strain, and the present invention provides strong support for the green prevention and control of tobacco diseases. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 : is the effect of Streptomyces 83 fermentation liquid on the growth of tobacco target spot mycelia; wherein A is the effect of Streptomyces 83 fermentation liquid treatment on the growth of tobacco target spot mycelia; B is the effect of clean water on the growth of tobacco target spot mycelia;

[0026] Figure 2 : are morphological characteristics of Streptomyces 83; wherein A is a picture of the early growth stage of Streptomyces 83; B is a picture of the late growth stage of Streptomyces 83; C is a picture of the hyphae morphology of Streptomyces 83; D is a picture of the spore morphology of Streptomyces 83;

[0027] Figure 3 This is the complete genome map of Streptomyces noursei S83;

[0028] Figure 4 This is a diagram showing the control effect of the fermentation filtrate of Streptomyces noursei S83 on rice sheath blight, rice blast and wheat stem rot; wherein, the S83 fermentation liquid is the fermentation filtrate of Streptomyces noursei S83. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0032] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] Example 1

[0035] 1. The efficacy of the fermentation liquid of biocontrol Streptomyces against tobacco spot pathogen

[0036] Seventeen biocontrol Streptomyces strains with good antagonistic effects in the laboratory were selected (the strain names are shown in Table 1) and inoculated into a fermentation medium (20 g soybean powder, 30 g corn powder, 20 g glucose, 4 g sodium chloride, 3 g calcium carbonate and 1 L water) at a 1% inoculation rate. The culture was shaken at 220 rpm and 28 °C for 72 h and filtered to obtain the fermentation broth of the 17 biocontrol Streptomyces strains. The effective viable count of the fermentation broth was 2.8 × 10 4CFU / mL. Use a hole puncher to punch a tobacco target spot pathogen cake with a diameter of 0.6 cm and place it in the center of a PDA medium (PDA medium, brand BD-Pharmingen, item number 213400) plate. Place an Oxford cup 2 cm to the left and right of the tobacco target spot pathogen cake and add 200 μL of different biocontrol Streptomyces fermentation liquid. There are 17 biocontrol Streptomyces treatments in total, that is, each biocontrol Streptomyces fermentation liquid is used as one treatment, and each treatment is repeated 3 times. At the same time, the water treatment is used as the control group. When the colony of the control group grows to 2 / 3 of the entire plate, observe and measure the inhibition zone, and calculate the inhibition rate. The results are shown in Table 1.

[0037] Table 1 Inhibition zones and inhibition rates of Streptomyces antagonistic to tobacco target spot

[0038]

[0039] The Oxford cup method was used to determine the antibacterial activity of fermented bacterial broths of 17 Streptomyces species preserved in the laboratory against tobacco target spot pathogens. The results showed that the fermented bacterial broths of 14 Streptomyces species had inhibitory effects on tobacco target spot disease, among which Streptomyces 83 had the highest inhibition rate against tobacco target spot disease, reaching 64.6%, which was higher than that of other Streptomyces (Table 1).

[0040] 2.2 Effect of Streptomyces 83 fermentation broth on the mycelial growth of tobacco spot pathogen

[0041] The mycelium growth rate method was used to test the tobacco spot pathogen. Two treatments were set up in the experiment, and each treatment was repeated 3 times. Treatment 1 was a water control; Treatment 2 was a fermentation broth of Streptomyces 83 (the effective viable count was 2.8×10 4 CFU / mL), to explore the effect of fermentation liquid treatment on the growth of tobacco target spot mycelium. The results are as follows Figure 1 The results showed that the hyphae morphology was observed under a microscope, and it was found that the hyphae of treatment 1 were thick and strong, with long internodes, and the angle between the newly grown hyphae and the parent hyphae was about 30°-45°, and the hyphae grew regularly; compared with treatment 1, treatment 2 had more branches, deformed, short and thick branches, etc.

[0042] 3. Identification and characterization of Streptomyces 83

[0043] 3.1 Observation of mycelial morphology

[0044] Gao's No. 1 culture medium (brand name: Aoboxing, item number: S1090198) was heated to melt and then inverted to cool. A sterilized cover glass was inserted into the culture medium at an angle of about 40-45 degrees. Streptomyces 83 was picked up with an inoculation loop and a line was drawn at the junction of the culture medium and the cover glass. The culture was inverted. Afterwards, the hyphae and spore morphology were observed under a microscope. The results were as follows: Figure 2The results showed that the surface of the colony of Streptomyces 83 was dry, opaque, and tightly velvety, and it was tightly bound to Gao's medium No. 1. The colony was white at the beginning, and gray spores began to be produced on the 4th to 5th day of culture at 28°C, and the colony gradually turned gray. At the same time, it can be observed under the microscope that the hyphae are multi-branched and unbroken. From the 4th day of culture, the hyphae are partially differentiated into compact spore threads.

[0045] 3.2. Whole genome sequencing of Streptomyces 83

[0046] The whole genome of Streptomyces 83 was sequenced and the sequencing results were analyzed. The metabolites of Streptomyces 83 were analyzed using the antiSMASH database. The whole genome map of the strain is shown in Figure 3 The analysis results of the antiSMASH database are shown in Table 2.

[0047] The sequencing and assembly results showed that the total length of the whole genome was 8212422bp and the GC content was 72.54%. At the same time, the whole genome was annotated with gene functions in combination with NR, COG, KEGG and GO databases. A total of 8998 open reading frames were predicted in the whole genome of the strain, accounting for 86.9% of the total genome length. The coding genes, repetitive sequences, non-coding RNAs, etc. were predicted to obtain the composition of the Streptomyces 83 genome. The genome encodes 71 tRNAs (total length 5385bp), 7 5S rRNAs (total length 812bp), 7 16S rRNAs (total length 10619bp), 7 23S rRNAs (total length 21836bp) and 16 sRNAs (total length 2197bp).

[0048] The blast results showed that Streptomyces 83 was Streptomyces noursei S83, and its classification name was Streptomyces noursei. It was deposited in the General Microbiology Center (CGMCC) of China Microorganism Culture Collection on July 10, 2024. The deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, and the deposit number is CGMCC No.31252.

[0049] The analysis results of the antiSMASH database showed that there were 36 secondary metabolic gene clusters, including nucleosides, polyketides, non-ribosomal peptides, butyrolactones, lactic acid bacteria peptides, etc. The base positions and gene cluster types of specific secondary metabolic gene clusters were (Table 2).

[0050] Table 2 Prediction of secondary metabolism biosynthesis gene clusters in the whole genome of Streptomyces noursei S83

[0051]

[0052] Table 3 Prediction of secondary metabolism biosynthesis gene clusters in the whole genome of Streptomyces noursei S83

[0053]

[0054] Note: The numbers are connected to the above table.

[0055] 3.3. Determination of physiological and biochemical characteristics of Streptomyces noursei S83

[0056] The culture medium formula used in the experiment is:

[0057] Gelatin liquefaction medium: 20 g glucose, 5 g peptone, 120 g gelatin, 1 L water, sterilized at 115 °C for 15 min;

[0058] Milk culture coagulation and peptone medium: 200g skim milk powder, 0.2g calcium carbonate, 1L water, sterilized at 115℃ for 15min;

[0059] Hydrogen sulfide medium: peptone 10g, ferric citrate 0.5g, agar powder 17g, water 1L;

[0060] Nitrate reduction medium: 0.5 g magnesium sulfate, 1 g potassium nitrate, 0.5 g potassium dihydrogen phosphate, 0.5 g sodium chloride, 20 g sucrose, 1 L water;

[0061] Gao's medium No. 1 containing starch: 0.5 g sodium chloride, 20 g soluble starch, 1 g potassium nitrate, 0.5 g dipotassium hydrogen phosphate, 0.5 g magnesium sulfate, 18 g agar, 1 L water;

[0062] Cellulose hydrolysis liquid medium: sodium chloride 0.5g, soluble starch 20g, potassium nitrate 1g, dipotassium hydrogen phosphate 0.5g, magnesium sulfate 0.5g, water 1L;

[0063] Phosphate-dissolving medium: glucose 10.0 g, ammonium sulfate 0.5 g, potassium chloride 0.3 g, sodium chloride 0.3 g, manganese sulfate 0.03 g, ferrous sulfate heptahydrate 0.03 g, magnesium sulfate 0.3 g, calcium phosphate 5.0 g, agar 20.0 g, water 1 L, pH 7.0-7.5;

[0064] Iron carrier production medium: agar powder 20g, 10× buffer (sterilized) 100mL, chrome azurol S (CAS) 0.06g; ferrous chloride hexahydrate 0.0027g, hexadecyltrimethylammonium bromide (MDTMA) 0.073g, water 1L;

[0065] Dextran agar medium: 4.0g Poria powder, 17.9g disodium hydrogen phosphate, 6.8g potassium dihydrogen phosphate, 6.7g yeast powder, 0.06g aniline blue, 15g agar powder, 1L water;

[0066] IAA production liquid medium: glucose 20.0 g / L, peptone 6.0 g / L, yeast extract 6.0 g / L, NaCl 10.0 g / L;

[0067] Carbon source utilization basic culture medium: 1 g diammonium hydrogen phosphate, 1 g sodium chloride, 0.2 g magnesium sulfate heptahydrate, 0.5 g potassium dihydrogen phosphate, 20 g agar, and 1 L distilled water.

[0068] Gelatin liquefaction test: Inoculate the S83 strain of Streptomyces noursei into a test tube containing gelatin liquefaction medium, culture at 28℃ for 10 days, then place the test tube in a 4℃ refrigerator for 0.5 hours to observe the degree of gelatin liquefaction. If the medium is partially or completely liquefied, it is a positive reaction; otherwise, it is a negative reaction.

[0069] Milk coagulation and peptonization: Inoculate the Streptomyces noursei S83 strain into a test tube containing milk culture medium by puncture. After culturing at 28°C for 7 days, if clots appear in the milk, it is coagulation. If it becomes liquid with continued culturing, it is peptonization, which is a positive reaction. Otherwise, it is a negative reaction.

[0070] Production of hydrogen sulfide: Inoculate the S83 strain of Streptomyces noursei on hydrogen sulfide culture medium, culture at 28℃ for 5 days, and observe the color change around the bacterial block. If the area around the bacterial block turns black, it means that hydrogen sulfide can be produced, which is a positive reaction; otherwise, it is a negative reaction.

[0071] Nitrate reduction test: Inoculate the Streptomyces noursei S83 strain into nitrate reduction medium, incubate at 28°C for 7-14 days, and then perform the test according to the operating procedures of the nitrate reduction kit.

[0072] Starch hydrolysis test: Inoculate the S83 strain of Streptomyces noursei into Gao's medium No. 1 containing starch, and culture it at 28℃ for 7 days. After the S83 strain of Streptomyces noursei grows well, drip iodine solution around the colony. If amylase is produced, the starch will be converted into dextrin or absorbed, and it will not turn blue when it encounters iodine solution, forming a transparent circle; otherwise, the colony will turn blue when it encounters iodine solution.

[0073] Cellulose hydrolysis test: Inoculate the S83 strain of Streptomyces noursei in a cellulose hydrolysis liquid medium with a filter paper strip, culture at 220 rpm at 28°C for 3 days and observe. If the filter paper breaks or becomes thinner, it means that the S83 strain of Streptomyces noursei can produce cellulase that can hydrolyze the filter paper, otherwise it can't.

[0074] Phosphate solubilization ability test: Inoculate the S83 strain of Streptomyces noursei on the phosphate solubilization medium and culture it at 28℃ for 5-7 days. Observe whether there is an obvious transparent circle around the colony, which means that the S83 strain of Streptomyces noursei has the ability to solubilize phosphate, otherwise it does not.

[0075] Siderophore production ability test: The Streptomyces noursei S83 strain was inoculated on the siderophore production medium and cultured at 28°C for 5-7 days. The formation of an orange halo around the colony was observed, indicating that the Streptomyces noursei S83 had the ability to synthesize siderophores, otherwise it did not.

[0076] Glucanase capacity test: Inoculate the Streptomyces noursei S83 strain on the glucan agar medium and culture it at 28°C for 5 days. If the transparent circle continues to increase with the growth of the Streptomyces noursei S83 colony, it means that glucanase is produced, otherwise it is not.

[0077] IAA production ability test: The Streptomyces noursei S83 strain was inoculated into the IAA-producing liquid culture medium, and cultured at 28°C, 220 rpm in a shaking incubator for 3 days. Then, an equal volume of Salkowski colorimetric solution (50 mL 35% HCl + 1 mL 0.5 mol / LFeCl3) was added, the mixture was allowed to stand in the dark for 3 minutes, and a color reaction was performed. If the fermentation broth of the Streptomyces noursei S83 strain turned pink, it proved that the secondary metabolism of the strain could produce IAA, otherwise it could not produce IAA.

[0078] Carbon source utilization test: 1% of galactose, maltose, sucrose, xylose, mannitol, glucose, lactose, rhamnose and fructose were added to the carbon source utilization basal culture medium respectively, and the Streptomyces noursei S83 strain was inoculated into the culture medium containing only one carbon source and cultured at 28°C. After 7 days, whether the Streptomyces noursei S83 strain can grow normally was observed. If it grows normally, the Streptomyces noursei S83 strain can utilize the carbon source, otherwise it cannot.

[0079] The survey results are shown in Table 4.

[0080] Table 4 Physiological and biochemical characteristics of Streptomyces noursei S83

[0081]

[0082] Note: + in the table indicates a positive reaction.

[0083] The results showed that after the S. noursei S83 strain was inoculated into the test plate or test tube and cultured for 5 days, a yellow halo formed by iron ions appeared on the test plate; it had the ability to reduce nitrate and hydrolyze starch, indicating that the S. noursei S83 strain could secrete amylase and nitrate reductase; it did not have the ability to secrete glucanase, dissolve organic phosphorus, coagulate and peptone milk, or hydrolyze cellulose; the gelatin liquefaction reaction result was negative; the hydrogen sulfide reaction result was negative. The S. noursei S83 strain had a high utilization rate of lactose, rhamnose, glucose, and fructose (Table 4).

[0084] Experimental Example 2 Effect of the fermentation filtrate of Streptomyces noursei S83 on tobacco growth

[0085] According to the criteria for the safety assessment of pesticides on crops (NY / T1965.1-2010), the potted method was used to spray tobacco when it grew to 3-4 leaves. The fermentation filtrate of Streptomyces noursei S83 (i.e., the fermentation filtrate of Streptomyces noursei S83 was filtered through a 0.45 μm ultrafiltration membrane, and the effective viable count was 2.8×10 4 CFU / mL), the spraying amount was 5mL / plant, and 1 blank control was set for each treatment. There were 10 plants in each treatment and 3 replicates for each treatment. When the tobacco was in the 3-4 leaf stage, 5 tobacco plants with relatively consistent growth were selected in each replicate. The height from the soil surface to the tobacco growth point was measured as the plant height, and the plant height growth rate and plant height growth inhibition rate were calculated. The calculation formula for plant height growth rate was plant height growth rate (mm / d) = (plant height after application - plant height before application) / plant height before application × interval time before and after application; the calculation formula for plant height growth inhibition rate was plant height growth inhibition rate = (blank control plant height growth rate - agent treatment plant height growth rate) / blank control plant height growth rate × 100%. 7, 14, and 21 days after spraying, the tobacco was investigated for symptoms of drug damage such as discoloration, necrosis, wilting, deformity, growth stagnation, and the number of affected plants. The results of the investigation are shown in Table 5.

[0086] Table 5 Effects of fermentation filtrate of Streptomyces noursei S83 on tobacco plant growth

[0087]

[0088] Its safety was evaluated according to the criteria for pesticide safety assessment on crops NY / T1965.1-2010. The results showed that the fermentation liquid of Streptomyces noursei S83 had no inhibitory effect on tobacco growth, no phytotoxicity occurred, and had a promoting effect on plant growth (Table 5).

[0089] Example 3 Indoor control effect of the fermentation filtrate of Streptomyces noursei S83 on tobacco target spot

[0090] When the tobacco seedlings transplanted in the greenhouse grow to the 6-leaf stage, a protective test is conducted. First, the pesticide is sprayed on the leaves of the tobacco plants. Two treatments are set up, each with 6 pots of tobacco, as follows:

[0091] The agent used in treatment 1 was the fermentation filtrate of Streptomyces noursei S83 (i.e., the fermentation broth of Streptomyces noursei S83 was filtered through a 0.45 μm ultrafiltration membrane, and the effective viable count was 2.8×10 4CFU / mL), the spraying amount was 5mL / plant; the agent used in treatment 2 was the water control (CK), and the spraying amount was 5mL / plant. 24 hours after spraying, the scraped leaves were inoculated with tobacco boot spot pathogenic bacteria cakes, and the diameter of the cakes was 6mm; the third and fourth true leaves of each plant were inoculated, and each leaf was inoculated with 6 cakes, which were moisturized with sterilized cotton. After 48 hours of inoculation, the cakes and cotton were removed, and the agent (S. noursei S83 fermentation liquid or water) was sprayed again, and the spraying amount was 5mL / plant. The incidence rate and disease index were investigated 7 days after spraying, and the control effect was calculated. The results are shown in Table 6.

[0092] Table 6 Pot control effect of Streptomyces noursei S83 fermentation filtrate on tobacco target spot disease

[0093]

[0094] Through plate assay, it was determined that Streptomyces noursei S83 had a good antibacterial effect on tobacco target spot disease. In order to verify the control effect on tobacco plants, an indoor pot experiment was conducted. The results showed that the control effect of the fermentation filtrate of Streptomyces noursei S83 was better than that of the control. It was found that after applying the fermentation filtrate of Streptomyces noursei S83, the color of the tobacco leaves was also greener (Table 6).

[0095] Example 4 The control effect of the fermentation filtrate of Streptomyces noursei S83 on rice sheath blight, rice blast and wheat stem rot

[0096] The mycelium growth rate method was used to determine the inhibitory effect of the fermentation filtrate of Streptomyces noursei S83 on other different pathogens. Rice sheath blight, rice blast and wheat stem rot were selected as targets to determine their antibacterial efficacy. 2% of the volume of liquid PDA medium was added to 100 mL of melted liquid PDA medium (i.e., the fermentation filtrate of Streptomyces noursei S83 was filtered through a 0.45 μm ultrafiltration membrane, and the effective viable count was 2.8×10 4 CFU / mL), shake evenly and pour into a sterile culture dish, dry and solidify for use. Use a 0.6 cm diameter punch to punch the activated pathogen into a cake, place it with the mycelium side facing down in the center of the bacterial plate, and then put it in a 25°C incubator for 4 days; at the same time, use clean water as a control. Each treatment was repeated three times. When the control colony filled the culture dish, the colony diameter was measured using the cross method, and the inhibition rate was calculated to obtain its inhibition spectrum; the inhibition rate was calculated as follows: inhibition rate = (control group colony diameter - treatment group colony diameter) / control group colony diameter × 100%. The survey results are shown in Tables 7 and Figure 4 shown.

[0097] Table 7 The control effect of the fermentation filtrate of Streptomyces noursei S83 on other diseases

[0098]

[0099] From Table 7 and Figure 4 It can be seen that the fermentation filtrate of Streptomyces noursei S83 has a preventive and therapeutic effect on rice sheath blight, rice blast and wheat stem rot, with the inhibition rates being 59.9%, 20.0% and 26.8%, respectively.

[0100] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A strain of Streptomyces noursei ( Streptomyces noursei ) S83, characterized in that, The deposit number of the Streptomyces noursei S83 is CGMCC No.31252.

2. Use of the Streptomyces noursei S83 according to claim 1 in preparing a biological agent for preventing and controlling plant diseases, characterized in that: The plant diseases include one or more of tobacco target spot, rice sheath blight, rice blast and wheat stem rot.

3. A biological agent for preventing and controlling plant diseases, characterized in that: The biological agent includes the Streptomyces noursei S83 described in claim 1; the plant diseases include one or more of tobacco target spot, rice sheath blight, rice blast and wheat stem rot.

4. Use of the Streptomyces noursei S83 according to claim 1 or the biological agent according to claim 3 in preventing and controlling plant diseases, characterized in that: The plant diseases include one or more of tobacco target spot, rice sheath blight, rice blast and wheat stem rot.

5. A method for preventing and controlling plant diseases, characterized in that: The following steps are involved: Spraying the biological agent according to claim 3 on the surface of the plant; The plant diseases include one or more of tobacco target spot, rice sheath blight, rice blast and wheat stem rot.

6. Use of the Streptomyces noursei S83 according to claim 1 in preparing a biological preparation for promoting tobacco growth.

7. A biological agent for promoting tobacco growth, characterized in that: The biological preparation comprises the Streptomyces noursei S83 described in claim 1.

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