A cotton phage and its application in plant disease control and plant growth promotion

Abstract

The present invention belongs to the field of microbial technology, and specifically relates to a cotton phagocytic bacterium and its application in plant disease prevention and control and plant growth promotion. The present invention screened and isolated a cotton phagocytic bacterium ( Variovorax gossypii )Cas202, which has been proven to significantly inhibit Ralstonia solanacearum, effectively prevent and treat tobacco bacterial wilt, and promote tobacco seed germination and tobacco plant growth. This strain has a wide range of applications, and can be used for the prevention and treatment of plant diseases, especially tobacco bacterial wilt, as well as for promoting tobacco seed germination and tobacco plant growth, thereby effectively broadening its application field and having good practical application value.

Description

Technical Field

[0001] The invention belongs to the technical field of microorganisms, and specifically relates to a cotton phagocytic bacterium and its application in plant disease prevention and control and plant growth promotion. Background Art

[0002] Solanaceae crops include tomatoes, potatoes, tobacco, eggplant, etc., which are important economic crops. With the change of eating habits and the development of facility agriculture, the planting area of ​​Solanaceae crops has been increasing. Due to the long-term continuous cropping, the diseases of Solanaceae crops have been getting worse year by year. Among them, bacterial wilt is caused by Ralstonia solanacearum ( Ralstonia solanacearum ) is a bacterial disease known as "plant cancer".

[0003] At present, the main prevention and control measures for Solanaceae bacterial wilt are concentrated on the selection and breeding of new resistant varieties, chemical control, biological control, etc. The breeding of resistant varieties is mostly targeted at a certain type of pathogenic species, which has limitations, and the cycle of variety breeding is long, which is difficult to meet agricultural needs. Chemical control is currently a common method for the prevention and control of Solanaceae bacterial wilt, but excessive chemical agents will lead to the emergence of pathogen resistance, reducing the field control effect, and will also threaten the environment and human health and other adverse effects. Biological control generally uses indigenous microorganisms with pathogen antagonism to inhibit the growth of pathogens, which has the characteristics of high efficiency, safety, and environmental friendliness. With the increasing demand for Solanaceae crop products and the increasing demand for health, while reducing the use of chemical fertilizers and pesticides, the development of new multifunctional microbial agents, improving the quality of Solanaceae crops and green prevention and control of bacterial wilt have attracted much attention. Summary of the invention

[0004] Based on the above prior art, the present invention provides a cotton phagocytic bacteria and its application in plant disease prevention and control and plant growth promotion. Specifically, the present invention isolates a cotton phagocytic bacteria ( Variovorax gossypii ) Cas202, which has been verified by experiments to have a strong ability to inhibit the growth of bacterial wilt pathogens and can effectively promote tobacco seed germination and tobacco plant growth. Based on the above research results, the present invention is completed.

[0005] In order to achieve the above technical objectives, the present invention relates to the following technical solutions:

[0006] The first aspect of the present invention provides a cotton phage ( Variovorax gossypii )Cas202, which was deposited in the General Microbiology Center of China Microbiological Culture Collection Administration (address: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, China) on September 5, 2023, and its biological deposit number is CGMCC No. 28362.

[0007] The second aspect of the present invention provides the above-mentioned cotton greedy phage ( Variovorax gossypii ) A fermentation production method for Cas202, the fermentation production method comprising: Variovorax gossypii )Cas202 is inoculated into the fermentation medium for fermentation culture.

[0008] The third aspect of the present invention provides a bacterial agent, which contains cotton phage Cas202 or its fermentation product.

[0009] The fourth aspect of the present invention provides the use of the cotton phage Cas202 or the bacterial agent in any one or more of the following (a)-(e):

[0010] (a) inhibiting plant pathogens;

[0011] (b) suppressing plant diseases;

[0012] (c) production of siderophore;

[0013] (d) promoting plant seed germination;

[0014] (e) Promote plant growth.

[0015] Wherein, the plant pathogen may be Ralstonia solanacearum;

[0016] The plant disease may be a plant disease mediated by Ralstonia solanacearum, such as tobacco bacterial wilt.

[0017] The promoting of plant growth is specifically manifested in increasing the plant height, leaf length, leaf width and root length.

[0018] The plant may be tobacco.

[0019] A fifth aspect of the present invention provides a method for promoting tobacco seed germination, the method comprising soaking the tobacco seeds with the cotton phage Cas202 or the above-mentioned bacterial agent.

[0020] A sixth aspect of the present invention provides a method for preventing and controlling tobacco bacterial wilt or promoting the growth of tobacco plants, the method comprising spraying or root irrigation treatment on tobacco plants using the cotton phage Cas202 or the above-mentioned bacterial agent.

[0021] Beneficial technical effects of one or more of the above technical solutions:

[0022] The above technical scheme screened and isolated a cotton phage Cas202 from the rhizosphere soil of tobacco for the first time. Experiments have shown that this strain can significantly inhibit Ralstonia solanacearum, effectively prevent and control tobacco bacterial wilt, and promote tobacco seed germination and tobacco plant growth.

[0023] In short, this strain has a wide range of applications. It can be used for the prevention and treatment of plant diseases, especially tobacco bacterial wilt, and can also be used to promote tobacco seed germination and tobacco plant growth, thereby effectively broadening its application field and having good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a colony morphology diagram of strain Cas202 in an embodiment of the present invention.

[0025] Figure 2 The Neighbour-Joining method was used to construct a phylogenetic tree of Cas202 and other standard species of the genus Vibrio and the family Comamonadaceae in the examples of the present invention.

[0026] Figure 3 This is the antibacterial effect of strain Cas202 on Ralstonia solanacearum in the examples of the present invention.

[0027] Figure 4 The figure shows the inhibitory effect of strain Cas202 on tobacco seedling morbidity under greenhouse conditions in an embodiment of the present invention; wherein A is the Cas202 treatment group and B is the clean water treatment group.

[0028] Figure 5 The results of the strain Cas202 producing siderophore (A) and promoting the germination rate of tobacco seeds (B) in the examples of the present invention are shown. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0030] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the term "comprising" or "including" is used in this specification, it indicates the presence of features, steps, operations, devices, components or combinations thereof.

[0031] In a typical embodiment of the present invention, a cotton phage ( Variovorax gossypii )Cas202, which was deposited in the General Microbiology Center of China Microbiological Culture Collection Administration (address: No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing, China) on September 5, 2023, and its biological deposit number is CGMCC No.28362.

[0032] In another specific embodiment of the present invention, the cotton phage ( Variovorax gossypii ) A fermentation production method for Cas202, the fermentation production method comprising: Variovorax gossypii )Cas202 is inoculated into the fermentation medium for fermentation culture.

[0033] The fermentation medium can be any medium for culturing bacteria. In a specific embodiment of the present invention, the medium is any one of NA medium and NB medium.

[0034] In another specific embodiment of the present invention, a bacterial agent is provided, which contains cotton phagocytic bacteria Cas202 or its fermentation product.

[0035] In the present invention, the term "fermentation" is used to refer to fermentation products. The corresponding fermentation can be obtained from the fermentation culture of cotton phage ( Variovorax gossypii ) The liquid obtained by the process of Cas202 can therefore also be called fermentation liquid; the liquid can contain bacteria (bacteria), but does not necessarily need to contain bacteria. The liquid preferably contains the cotton phage ( Variovorax gossypii ) Metabolites produced by Cas202.

[0036] Also, in an embodiment of the present invention, the fermentation liquid or culture liquid containing the bacteria is centrifuged, filtered, sedimented or other means known in the art to separate the bacterial cells grown in the fermentation liquid or culture liquid from the liquid, and the liquid remaining after the bacterial cells are removed is the "supernatant", and in the present invention, the supernatant contains Cotton Phage ( Variovorax gossypii ) Extracellular metabolites of Cas202. In an embodiment of the present invention, the bacterial agent may also include the supernatant.

[0037] Also, in an embodiment of the present invention, the fermentation liquid or culture liquid containing the bacteria is centrifuged, filtered, sedimented or other means known in the art to separate the bacterial cells grown in the fermentation liquid or culture liquid from the liquid to obtain the bacteria, and the bacteria can be crushed to obtain the bacterial crushed material, and the crushing method can be ultrasound (such as ice bath ultrasound crushing cells) or other means known in the art, or, further, the bacterial crushed material is centrifuged to collect the supernatant, and the supernatant is recorded as a cell-free extract, and in the present invention, the bacterial crushed material or the cell-free extract contains Cotton Phage ( Variovorax gossypii ) Intracellular metabolites of Cas202. In an embodiment of the present invention, the bacterial agent may also include the bacterial cell fragments or cell-free extracts.

[0038] Furthermore, in the embodiments of the present invention, in order to facilitate storage and transportation, improve the survival rate of the strain, etc., the bacterial agent can also be a solid (such as a powder), and further a freeze-dried powder. Variovorax gossypii ) Cas202 or its fermentation product is further freeze-dried to obtain, and the freeze-drying technology (including vacuum freeze-drying technology) can be carried out by conventional methods, which will not be repeated here.

[0039] In another specific embodiment of the present invention, the bacterial agent may further include excipients acceptable in the field of bacterial agents.

[0040] In another specific embodiment of the present invention, the auxiliary material is selected from one or more of a dispersant, a wetting agent, a disintegrant, a binder, a defoamer, a thickener, a filler and a solvent. The present invention has no special restrictions on the source of the auxiliary materials acceptable to the bacterial agent, and generally commercial products can be used.

[0041] The dispersant is an anionic dispersant or a nonionic dispersant, and can be selected from one or more of sodium lignin sulfonate, sodium naphthalene sulfonate formaldehyde condensate, sodium methylene bisnaphthalene sulfonate, formaldehyde condensate sulfate, polycarboxylate, alkylphenol polyoxyethylene phosphate and fatty acid polyoxyethylene ester.

[0042] The wetting agent can be selected from one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, saponin powder, tea kudzu powder and lakai powder BX.

[0043] The disintegrant may be selected from one or more of bentonite, aluminum chloride, magnesium chloride and glucose.

[0044] The binder may be selected from one or more of starch, diatomaceous earth, cyclodextrin, rosin, carboxymethyl cellulose and carboxymethyl cellulose salt.

[0045] The defoaming agent can be selected from one or more of C8-C20 fatty alcohol compounds, epoxidized soybean oil, ethanol, silicone compounds and organic silicone oil.

[0046] The thickener may be selected from one or more of xanthan gum, polyethylene glycol and polyvinyl alcohol.

[0047] The filler may be selected from one or more of light calcium carbonate, diatomaceous earth, attapulgite and white carbon black.

[0048] The solvent may be selected from water or methyl oleate.

[0049] In another specific embodiment of the present invention, the cotton phage ( Variovorax gossypii ) Use of Cas202 or bacterial agents in any one or more of the following (a)-(e):

[0050] (a) inhibiting plant pathogens;

[0051] (b) suppressing plant diseases;

[0052] (c) production of siderophore;

[0053] (d) promoting plant seed germination;

[0054] (e) Promote plant growth.

[0055] Wherein, the plant pathogen may be Ralstonia solanacearum;

[0056] The plant disease may be a plant disease mediated by Ralstonia solanacearum, such as tobacco bacterial wilt.

[0057] The promoting of plant growth is specifically manifested in increasing the plant height, leaf length, leaf width and root length.

[0058] The plant may be tobacco.

[0059] In another specific embodiment of the present invention, a method for promoting tobacco seed germination is provided, the method comprising applying the above-mentioned cotton phage ( Variovorax gossypii ) Soak in Cas202 or the above-mentioned bacterial agents.

[0060] In another specific embodiment of the present invention, a method for preventing and controlling tobacco bacterial wilt or promoting the growth of tobacco plants is provided, the method comprising spraying or root irrigation treatment on tobacco plants using the cotton phagocytic bacterium Cas202 or the above-mentioned bacterial agent.

[0061] The present invention is further explained by the following examples, but they are not intended to limit the present invention. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The pathogens tested in the examples are all isolated and stored by the Tobacco Research Institute of the Chinese Academy of Agricultural Sciences.

[0062] Example

[0063] 1. Materials and Methods

[0064] 1.1 Materials

[0065] Experimental samples: rhizosphere soil samples from tobacco in Hubei.

[0066] Required culture medium: NA medium, NB medium, CAS identification medium.

[0067] Required tobacco varieties: K326, Yunyan 87.

[0068] 1.2 Methods

[0069] (1) Isolation and culture of strains

[0070] Root tissue samples of tobacco plants with bacterial wilt were collected on July 10, 2022. After brushing off the soil samples attached to the root surface with a brush, the root tissue samples were placed in physiological saline (0.85% NaCl), and the root surface soil was collected using ultrasonic vibration. Deionized water precooled at 4°C was added to the ultrasonic cleaner, and the centrifuge tube was placed in the water. Ultrasonic treatment was performed twice, each time for 20 s, and the interval between two ultrasonic treatments was 5 s. The fine roots in the centrifuge tube were removed and discarded with sterile tweezers, 1 mL of soil suspension was added to 9 mL of physiological saline, and a 10-fold gradient dilution was applied to NA medium (beef extract 3.0 g / L; peptone 5.0 g / L; glucose 2.5 g / L; agar 18.0 g / L; 121°C high temperature and high pressure sterilization for 20 min), and cultured at 28°C for 48 h. According to the growth characteristics of the colony, such as color, size, degree of protrusion, transparency, hardness and whether the edge is regular, a single colony is picked, and the picked single colony is streaked on NA medium and purified three times to obtain a pure culture strain.

[0071] (2) Identification of strain types

[0072] ① Streak the strain onto fresh NA medium and culture at 28℃ for 24 h. Use a 10 μL pipette tip to pick up the purified cultured bacterial moss into a 2 mL centrifuge tube, add 100 μL of TE (10 mmol / L Tris.HCl; 1 mmol / L EDTA; pH 8.0) buffer, place in a boiling water bath for 10 min, immediately place in a -20 ℃ refrigerator overnight, centrifuge at 12000 rpm for 10 min, and take the supernatant as the strain DNA.

[0073] ②Using genomic DNA as template, bacterial primers (27F / 1492R: 5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO.1 / 5'-GGTTACCTTGTTACGACTT-3', SEQ ID NO.2) were used to amplify the 16S rRNA gene of the strain. The PCR system was 3 μL 10× buffer; 3 μL dNTP; 0.3 μL primer; 0.15 μL rTaq; 1 μL DNA template; 22.25 μL dd H2O. The reaction conditions were pre-denaturation at 94 ℃, 5 min; 94 ℃, 1 min, 55 ℃ 1 min, 72 ℃ 1.5 min, 30 cycles; extension at 72 ℃ 10 min. The PCR products were analyzed by agarose gel electrophoresis, and the obtained fragments were sequenced.

[0074] ③ The sequences obtained were compared on the EzBioCloud website (http: / / www.ezbiocloud.net / ), and a phylogenetic tree was constructed using MEGA 11 software. The taxonomic status of the strain was finally determined based on the similarity and the position of the phylogenetic tree.

[0075] (3) Preservation of bacterial strains

[0076] The purified strain was streaked on a slant, 5 mL of sterile glycerol seed solution (20% glycerol) was added, the bacterial moss was vortexed, and the tubes were divided into 2 mL cryovials, stored at -80°C, and sent to the China General Microbiological Culture Collection Center (CGMCC) with the deposit number of CGMCC No. 28362.

[0077] (4) Determination of antibacterial ability and disease prevention effect under greenhouse conditions

[0078] Pick a single colony and place it in NB medium (beef extract powder 3.0 g / L; peptone 10.0 g / L; sodium chloride 5 g / L; sterilized at 121 ℃ and high temperature and high pressure for 20 min) and culture at 28 ℃ for 24 h. Use NB medium to adjust the OD of the bacterial solution 600 to 0.3. Pipette 10 µL of bacterial suspension (OD 600 =0.3), inoculated in the center of a 9-cm diameter NA solid culture medium, and after the bacterial solution was fully absorbed, the culture dish was placed in a 28°C biochemical incubator and incubated upside down for 72 h. Ralstonia solanacearum ) RS10 was prepared into OD 600 = 0.3 bacterial suspension. Then, the pathogen suspension was sprayed onto the NA medium, and the culture dish was transferred to a 28°C constant temperature incubator. After inverted culture for 24 h, the size of the inhibition zone was measured and the antibacterial ability of the strain was calculated.

[0079] Tobacco seeds (Yunyan 87) were soaked in 15% H2O2 for 10 min, 75% ethanol for 30 s, and washed three times with sterile water. They were sown in the substrate and transplanted into a 10 cm diameter pot when the tobacco seedlings grew 4 leaves. The strains to be tested and Ralstonia solanacearum were inoculated into NB medium and cultured at 28°C and 200 rpm for 24 h. They were then centrifuged at 9000 rpm for 1 min, resuspended in sterile water, and the OD was adjusted. 600To 0.6. In the experimental group, 20 mL of the test bacterial suspension was taken and poured into the roots of the tobacco seedlings, and the roots were poured twice with an interval of 5 days in between; the control group was poured with an equal amount of clean water. After 10 days, 20 mL of the pathogen suspension was poured into the roots of the tobacco plants. Each treatment group repeated 15 pots of tobacco seedlings. The plants were observed for bacterial wilt symptoms after applying the bacterial wilt fungus. When the first diseased plant appeared, the disease situation of each treatment was observed every 2 days for a total of 20 days. The severity of the disease was graded as follows: Level 0: healthy plant; Level 1: 1%~25% of the leaves were diseased; Level 3: 26%~50% of the leaves were diseased; Level 5: more than 50% of the leaves were diseased; Level 7: more than two-thirds of the leaves were diseased; Level 9 The whole plant died. The incidence rate (= number of diseased plants / total number of plants investigated × 100%), disease index (= Σ (number of disease levels × number of diseased plants) / (number of plants investigated × 9) × 100%) and protective efficacy (control disease index - test disease index) / control disease index × 100%) of each treatment group were calculated.

[0080] (5) Determination of siderophore production ability

[0081] CAS identification medium: 20% sucrose solution 10 mL / L, 10% acid hydrolyzed casein 30 mL / L, 1 mmol / L CaCl2 1 mL / L, 1 mmol / L MgSO4 20 mL / L, agar 15 g / L, slowly add 50 mL of phosphate buffer and CAS dye solution at about 60℃, sterilize at 121℃ high temperature and high pressure for 20 min; CAS dye solution: CAS (chrome azure) 1 mmol / L, FeCl3 0.1 mmol / L, HDTMA (hexadecyltrimethylammonium bromide) 4 mmol / L; phosphate buffer: Na2HPO4·12H2O 24.27 g / L, NaH2PO4·2H2O 5.905 g / L, KH2PO4 0.75 g / L, NH4Cl2 0.50 g / L, NaCl 1.25 g / L, pH 6.8, diluted 10 times when used. 10 μL of OD 600 =0.3 of bacterial suspension was spotted in the center of CAS identification medium, and the plate was transferred to a 28°C constant temperature incubator. Continuous observation was conducted, and the appearance of a yellow halo indicated that the strain had the ability to produce siderophore.

[0082] (6) Effects on tobacco seed germination and tobacco seedling growth

[0083] Tobacco seeds (K326) were soaked in 15% H2O2 for 10 min, soaked in 75% ethanol for 30 s, and washed three times with sterile water. The strain Cas202 was inoculated into NB liquid medium, cultured overnight at 28°C and 180 rpm, and the cells were collected by centrifugation at 8000 rpm for 5 min, resuspended in sterile water, and the OD value of the bacterial suspension was adjusted. 600=0.3; after disinfection, the seeds were soaked in bacterial suspension for 30 min, and the control was soaked in sterile water for 30 min; a double layer of sterilized filter paper was spread in the culture dish and moistened with 2 mL of sterile water; 100 tobacco seeds were evenly dotted on the filter paper and cultured at 28℃, and the seed germination was recorded.

[0084] The strain was inoculated into NB liquid medium, cultured overnight at 28°C and 180 rpm, centrifuged at 8000 rpm for 5 min to collect the bacteria, discarded the supernatant, resuspended with sterile water, and adjusted the OD value of the bacterial suspension. 600 =0.3, 14 d and 21 d after transplanting, each tobacco plant was irrigated with 20 mL of bacterial solution, and the control group was irrigated with 20 mL of sterile water. After 28 d, the differences in plant height, leaf length and leaf width between the treatment group and the control group were measured.

[0085] 2. Experimental Results

[0086] 2.1 Strain morphology and species identification

[0087] Cas202 was inoculated on NA medium and cultured at 28 °C for 24 h. The single colony of the strain was milky white, slightly transparent, and had smooth edges ( Figure 1 ). By sequencing the 16S rRNA gene, a gene sequence of 1415 bp was obtained. The obtained sequence was compared with the EZBioCloud database and it was found that Cas202 was similar to Cotton Phage ( Variovorax gossypii ) JM-310 T The highest similarity is 99.64%. The phylogenetic tree was constructed by comparing Cas202 with the 16S rDNA sequences of other standard bacteria of the genus Vibrio and the family Comamonadaceae ( Figure 2 ), and found that Cas202 and cotton phagocytosis clustered together, and finally determined that Cas202 was cotton phagocytosis.

[0088] 2.2 Antibacterial ability of strains and disease inhibition effect under greenhouse conditions

[0089] By testing the effect of strain Cas202 on tobacco bacterial wilt ( Ralstonia solanacearum ) The antibacterial ability of RS10 was investigated. The results showed that strain Cas202 had a significant antagonistic effect on Ralstonia solanacearum, the pathogen of tobacco wilt. Figure 3 ), the inhibition rate was 55.61%. Under greenhouse conditions, the control effect of Cas202 on bacterial wilt was determined, and the results are as follows Figure 4 As shown, Figure 4 Middle A is the Cas202 treatment group, Figure 4 B is the clean water treatment group or the control group, that is, 20 mL (OD 600=0.6) The morbidity rate of tobacco plants treated with Cas202 suspension was 60%, significantly lower than that of the control group (93%); the disease index of the treated group was 28.00, significantly lower than that of the control group (70.96); the prevention effect of strain Cas202 on bacterial wilt was 60.54%.

[0090] 2.3 Ability of strains to produce siderophore and promote seed germination

[0091] like Figure 5 As shown in Figure A, a yellow halo was produced on the CAS plate, indicating that strain Cas202 was able to produce siderophore. Figure 5 As shown in B, after treatment with Cas202 bacterial suspension, the seed germination rate reached 99.07±1.60%, while the germination rate of tobacco seeds treated with sterile water (control) was only 86.11±2.78%. The Cas202 treatment group was significantly higher than the control group, indicating that treatment of tobacco seeds with Cas202 bacterial suspension can significantly promote the germination of tobacco seeds.

[0092] 2.4 Effect of strain Cas202 on tobacco growth

[0093] As shown in Table 1, the plant height, leaf length, leaf width and other physiological indicators of the strain Cas202 after root irrigation were significantly improved compared with the control group (p<0.01), with the plant height increasing by about 0.66 cm, the leaf length increasing by about 2.42 cm, the leaf width increasing by about 1.85 cm, and the root length increasing by 1.03 cm. This shows that root irrigation with the suspension of the strain Cas202 can promote the growth of tobacco plants and has a good growth-promoting effect.

[0094] Table 1 The growth-promoting effect of strain Cas202 on plants

[0095]

[0096] Note: "**" in the table represents p <0.01; "***" represents p <0.001.

[0097] In summary, the present invention isolated a bacterium from the root surface of the diseased tobacco plant, named Cas202. 16SrRNA sequencing and phylogenetic tree construction were used to determine that strain Cas20 was a cotton phagocytosis ( Variovorax gossypii ), and the antibacterial ability of strain Cas202 was determined to be effective against Ralstonia solanacearum ( Ralstonia solanacearum) RS10 has a significant antagonistic effect, with an inhibition rate of 55.61%; and Cas202 has a protective effect against bacterial wilt of 60.54%. At the same time, strain Cas202 has the ability to produce siderophore and significantly promote the germination of tobacco seeds, with a germination rate of up to 99.07%; through growth promotion experiments, it was found that strain Cas202 can significantly promote plant growth after treatment, and significantly improve physiological indicators such as plant height, leaf length, leaf width, and root length.

[0098] Strain Cas202 16S rRNA gene sequence

[0099]

[0100] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A cotton phage ( Variovorax gossypii )Cas202, which was deposited in the General Microbiology Center of China Microbiological Culture Collection Administration on September 5, 2023, and its biological deposit number is CGMCC No. 28362.

2. The cotton phage according to claim 1 ( Variovorax gossypii ) A fermentation production method of Cas202, characterized in that: The fermentation production method comprises: Variovorax gossypii )Cas202 is inoculated into the fermentation medium for fermentation culture.

3. The fermentation production method according to claim 2, characterized in that: The fermentation medium is any one of NA medium and NB medium.

4. A bacterial agent, characterized in that: The bacterial agent contains the cotton phagocytic bacteria ( Variovorax gossypii )Cas202 or its fermentation broth.

5. The cotton phage according to claim 1 ( Variovorax gossypii ) Use of Cas202 or the bacterial agent described in claim 4 in any one or more of the following (a)-(e): (a) inhibiting plant pathogens; (b) suppressing plant diseases; (c) production of siderophore; (d) promoting plant seed germination; (e) promoting plant growth; The plant pathogen is Ralstonia solanacearum; the plant disease is tobacco bacterial wilt; The plant is tobacco.

6. The use according to claim 5, characterized in that The promoting of plant growth is specifically manifested in increasing the plant height, leaf length, leaf width and root length.

7. A method for promoting tobacco seed germination, characterized in that: The method comprises treating tobacco seeds with the cotton phage according to claim 1 ( Variovorax gossypii ) Cas202 or the bacterial agent described in claim 4 is soaked.

8. A method for preventing and controlling tobacco bacterial wilt or promoting tobacco plant growth, characterized in that: The method comprises applying the cotton phage according to claim 1 to tobacco plants. Variovorax gossypii ) Cas202 or the bacterial agent described in claim 4 is sprayed or root irrigated.

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