Actinomycetes capable of antagonizing various plant pathogens and application of actinomycetes

Abstract

The invention relates to the technical field of microbial pesticides and microbial fertilizers, in particular to actinomycetes antagonizing various plant pathogens and application of the actinomycetes antagonizing various plant pathogens, and provides a YC3041 strain with the taxonomic name of Streptomyces pratensis and the preservation number of GDMCC No: 64828. The technical scheme provided by the invention has the characteristics of low use cost, good control effect, no residue and safety to human, livestock and environment, and the actinomycetes antagonizing various plant pathogens and the application of the actinomycetes antagonizing various plant pathogens have broad application prospects. The biological pesticide prepared from the YC3041 strain has the control effect of 70% or above on tobacco root knot nematode disease, tobacco bacterial wilt, tobacco black shank and compound diseases caused by the tobacco root knot nematode disease, the tobacco bacterial wilt and the tobacco black shank.

Description

Technical Field

[0001] The invention relates to the technical field of microbial pesticides and microbial fertilizers, and in particular to application of a Streptomyces pratensis YC3041 strain in preventing and controlling tobacco root knot nematode disease, tobacco black shank disease or tobacco bacterial wilt disease and composite diseases caused by the three in agricultural planting. Background Art

[0002] Tobacco root knot nematode disease caused by root knot nematodes, tobacco black shank disease caused by tobacco phytophthora infection, and tobacco bacterial wilt disease caused by Ralstonia solanacearum infection are the three major soil-borne diseases in flue-cured tobacco cultivation. Disease complexes caused by plant parasitic nematodes and soil-borne pathogens that inhabit the same ecological niche and co-infect the same host often cause greater losses than single pathogenic diseases and are more difficult to control. In flue-cured tobacco cultivation, complex diseases caused by mixed infection of "root knot nematodes-tobacco phytophthora", "root knot nematodes-Ralstonia solanacearum", and "root knot nematodes-tobacco phytophthora-Ralstonia solanacearum" are serious and cause huge losses. Current prevention and control measures for complex diseases mainly rely on the application of chemical pesticides targeting different pathogens, and large doses must be applied to achieve good prevention and control effects. Large doses of chemical pesticides pollute the environment and destroy the soil microecology; therefore, it is imperative to develop safe and efficient microbial pesticides. At present, composite bacterial agents are developed using biocontrol bacteria that antagonize different pathogens for the prevention and treatment of root-knot nematode complex diseases. However, due to the use of multiple biocontrol bacteria, the cost is high and the processing technology is complicated, which is not easy to promote. Many microorganisms are resistant to pathogenic nematodes, bacteria and fungi. It has broad application prospects to explore and utilize such microbial resources to develop biocontrol products for the prevention and treatment of root-knot nematode complex diseases. Streptomyces is the main group of actinomycetes, which can produce abundant active metabolites such as antibiotics and is widely used in biological control of pests and diseases. The present invention screened an actinomycete YC3041 from tobacco-growing soil. Based on morphological and molecular biological characteristics, the actinomycete was identified as S. pratensis. The fermentation liquid of the YC3041 strain has good antagonistic activity against the second-instar larvae of root-knot nematodes, tobacco phytophthora nicotianae and Ralstonia solanacearum. After searching domestic and foreign literature, there is no report on the biocontrol activity of S. pratensis against root-knot nematodes, tobacco phytophthora and Ralstonia solanacearum, which highlights the innovation and potential application value of the present invention. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an application of a S. pratensis strain that is resistant to root-knot nematodes, plant pathogenic bacteria and plant pathogenic fungi.

[0004] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0005] On the one hand, the present invention provides a YC3041 strain, the taxonomic name of the YC3041 strain is Streptomyces pratensis, and the deposit number is GDMCC No: 64828. More specifically, the YC3041 strain, whose deposit name is Streptomyces pratensis YC3041 strain, is deposited in the Guangdong Provincial Microbiological Culture Collection Center, the address of which is the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou; the deposit date is July 4, 2024; the deposit number is GDMCC No: 64828, and the viability of the biological material was tested by the collection center on July 4, 2024, and the result was viable.

[0006] In another aspect, the present invention provides a fermentation culture of the YC3041 strain.

[0007] Furthermore, the method for preparing the fermentation culture of the YC3041 strain comprises the following steps:

[0008] (1) Activation of strains: Inoculate the YC3041 strain onto a slant of solid ISP4 medium in a test tube and culture at 30-37°C for 3-6 days to obtain a slant strain;

[0009] (2) Fermentation culture: The activated strain was inoculated into liquid ISP4 medium, and cultured at 28-36° C. and 120-180 rpm for 4-8 days to obtain a fermentation culture of the YC3041 strain;

[0010] The ISP4 culture medium includes 10 g / L soluble starch, 1 g / L peptone, 0.5 g / L yeast extract, 2 g / L (NH4)2SO4, 1 g / L MgSO4, 1 g / L K2HPO4, 1 g / L NaCl, and 2 g / L CaCO3; the solid ISP4 culture medium contains 18 g / L agar, and the liquid ISP4 culture medium does not contain agar.

[0011] On the other hand, the present invention provides a bacterial agent, which contains the YC3041 strain or the fermentation culture of the YC3041 strain. In some specific embodiments, the bacterial agent also contains nutrients: providing nutrients required for the growth of microorganisms, such as carbon sources, nitrogen sources, inorganic salts, etc.; protective agents: used to protect the activity of microorganisms during processing, storage and application; carriers or matrices: microorganisms need to attach to a certain carrier, such as organic materials (such as straw, sawdust), inorganic media (such as bentonite, perlite), etc.; other additives: may include some enhancers, sustained-release agents, etc., to improve the effect and stability of the bacterial agent.

[0012] In another aspect, the present invention provides a pesticide complex, which contains the microbial agent. In some specific embodiments, the pesticide complex can be a complex of the microbial agent of the present invention and other microbial agents, chemical fungicides or antibiotic fungicides.

[0013] In another aspect, the present invention provides the use of the YC3041 strain, or the fermentation culture of the YC3041 strain, or the bacterial agent, or the pesticide complex in controlling at least one of root-knot nematodes, tobacco phytophthora, or Ralstonia solanacearum.

[0014] In another aspect, the present invention provides the use of the YC3041 strain, or the fermentation culture of the YC3041 strain, or the bacterial agent, or the pesticide complex according to claim 5 in preventing and controlling at least one of tobacco root knot nematode disease, tobacco bacterial wilt or tobacco black shank disease.

[0015] In another aspect, the present invention provides the use of the YC3041 strain, or the fermentation culture of the YC3041 strain, or the bacterial agent, or the pesticide complex in preventing and controlling complex diseases caused by tobacco root-knot nematode disease, tobacco bacterial wilt and tobacco black shank disease.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The YC3041 strain of the present invention is easy to ferment and culture, and its culture has nematicidal, antibacterial and antifungal activities, and can be used as a nematicide and fungicide to prevent and control tobacco root knot nematode disease, tobacco bacterial wilt and tobacco black shank disease and the combined diseases caused by them, with a prevention efficiency of more than 70%.

[0018] (2) The YC3041 strain of the present invention has the advantages of high efficiency, low toxicity and low residue in preventing and treating tobacco root-knot nematode disease, tobacco bacterial wilt and tobacco black shank disease and the complex diseases caused by them, and is safe for humans, animals and the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The morphological characteristics and phylogenetic analysis diagram of the S. pratensis YC3041 strain of the present invention; Figure 1 A: Colony morphology of YC3041 strain cultured on ISP4 medium at 30°C for 7 days; Figure 1 B: Spore morphology of strain YC3041; Figure 1 C: Phylogenetic analysis based on 16S rDNA sequences showed that strain YC3041 was S. pratensis.

[0021] Figure 2 The figure is a graph showing the antagonistic activity of the YC3041 strain culture of the present invention against the second-instar larvae of root-knot nematodes, Phytophthora nicotianae and Ralstonia solanacearum; Figure 2 A: control nematodes; Figure 2 B: YC3041 strain culture kills second-instar larvae; Figure 2 C: Colonies of Phytophthora nicotianae in the control; Figure 2 D: YC3041 strain culture antagonizes the colony of Phytophthora nicotianae; Figure 2 E: Colonies of Ralstonia solanacearum in the control; Figure 2 F: YC3041 strain culture antagonizes Ralstonia solanacearum colonies. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0024] In the present application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple, respectively.

[0025] The first aspect of the embodiment of the present application provides a strain YC3041 of Streptomyces pratensis (referred to as S. pratensis in the present invention), the taxonomic name of the strain is Streptomyces pratensis, the preservation name is Streptomyces pratensis YC3041 strain, which is preserved in Guangdong Provincial Microbiological Culture Collection Center, and the preservation address is the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, Compound 100, Xianlie Middle Road, Guangzhou; preservation date: July 4, 2024; preservation number: GDMCC No: 64828, the viability of the biological material was tested by the preservation center on July 4, 2024, and the result was survival.

[0026] The second aspect of the embodiments of the present application provides a bacterial agent prepared by the S. pratensis YC3041 strain, wherein the active ingredient is the fermentation culture of the S. pratensis YC3041 strain.

[0027] A third aspect of the embodiments of the present application provides the use of a bacterial agent of the S. pratensis YC3041 strain in preventing and controlling tobacco root-knot nematode disease, tobacco bacterial wilt and / or tobacco black shank disease and the combined diseases caused by them.

[0028] Example 1: The actinomycetes of the present invention are S. pratensis YC3041 strains

[0029] The YC304 strain was deposited in the Guangdong Provincial Microbiological Culture Collection on July 4, 2024; the address of the deposit unit is: Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou; the deposit number is GDMCC No: 64828.

[0030] When YC304 strain was cultured on ISP4 solid medium (soluble starch 10 g / L, peptone 1 g / L, yeast extract 0.5 g / L, (NH4)2SO4 2 g / L, MgSO4 1 g / L, K2HPO4 1 g / L, NaCl 1 g / L, CaCO3 2 g / L, agar 18 g / L, pH 7.2) at 30°C for 7 days, the colonies were gray, the edge hyphae were white, the colony surface was dry and difficult to pick up, showing typical actinomycete colony characteristics ( Figure 1 A); spores are columnar and chain-like on hyphae ( Figure 1 B); Phylogenetic analysis based on 16S rDNA sequences ( Figure 1 C) indicates that the strain is S. pratensis.

[0031] Example 2: The S. pratensis YC3041 strain of the present invention can antagonize root-knot nematodes, tobacco phytophthora and Ralstonia solanacearum

[0032] The present invention uses ISP4 liquid culture medium (agar is not added in the formula of ISP4 solid culture medium) to culture the YC3041 strain at 30° C. and 150 rpm for 7 days according to a conventional microbial fermentation method to obtain a culture.

[0033] 500 second-instar larvae (J2) of southern root-knot nematode (Meloidogyne incognita) were added to a plate containing 2 ml of YC3041 culture medium, and an equal volume of ISP4 culture medium was used instead of YC3041 culture medium as a control. After being placed at room temperature for 24 hours, the number of dead nematodes and the number of live nematodes in 200 nematodes were counted under a dissecting microscope, and the nematode mortality rate was calculated: Nematode mortality rate (%) = (number of dead nematodes in the treatment group - number of dead nematodes in the control group) / 200 × 100. The results showed that ISP4 culture medium had no activity against J2, and the nematodes were bent ( Figure 2 A); The lethality rate of YC3041 culture on J2 reached 98.74%, and the dead nematodes were in a state of stiffness ( Figure 2 B).

[0034] A 5 mm diameter mycelium sheet of tobacco phytophthora was inoculated in the center of the PDA plate. Three filter papers were placed on the plate with the mycelium sheet as the center, forming an isosceles triangle shape. 10 μl of YC3041 culture was dripped on each filter paper sheet. The YC3041 culture was replaced with an equal volume of ISP4 medium as a control. Each treatment was repeated 5 times. After culturing at 28°C for 5 days, the colony diameter of tobacco phytophthora was measured, and the antibacterial rate was counted: antibacterial rate (%) = (control colony diameter - treatment colony diameter) / control colony diameter × 100. The results showed that ISP4 medium had no antagonistic activity against the mycelial growth of tobacco phytophthora, and its colonies were round ( Figure 2C); YC3041 culture had an inhibition rate of 75.64% on the mycelial growth of tobacco phytophthora, and the colonies were small and nearly triangular ( Figure 2 D).

[0035] Use conventional beef extract peptone medium (beef extract 3g / L, peptone 10g / L, NaCl 5g / L, pH 7.2) to culture Ralstonia solanacearum at 30℃ and 150rpm for 2 days. Take 1ml of Ralstonia solanacearum culture and add it to 500ml beef extract peptone medium. Mix well and pour it into a plate. After the plate is cooled and solidified, use a 0.5cm fungus puncher to evenly punch 6 holes on the plate. Add 100μl YC3041 culture to 3 of the holes, and add an equal amount of beef extract peptone medium to the other 3 holes as a control. Each treatment is repeated 5 times; after culturing at 28℃ for 2 days, the diameter of the inhibition zone is measured. The results showed that ISP4 liquid culture medium had no antagonistic activity against the growth of Ralstonia solanacearum, and there was no inhibition zone near the circular hole ( Figure 2 E); YC3041 culture showed strong antagonistic activity against the growth of Ralstonia solanacearum, with an obvious inhibition zone near the circular hole ( Figure 2 F), the diameter of the inhibition zone reached 12.35 mm.

[0036] Example 3: The S. pratensis YC3041 fungal agent of the present invention can effectively prevent and control tobacco root knot nematode disease, tobacco bacterial wilt and tobacco black shank disease and the combined diseases caused by them

[0037] 1. Preparation of S. pratensis YC3041 inoculum

[0038] Test tube slant seed culture of YC3041 strain: The strain was inoculated onto a conventional ISP4 solid culture medium slant and cultured at 35°C for 5 days to obtain slant seeds.

[0039] Liquid seed culture of YC3041 strain: The slant seeds were inoculated into a conical flask filled with ISP4 liquid culture medium and cultured in a shaking incubator at 35°C and 150 rpm for 4 days to obtain liquid seeds.

[0040] Large-scale culture of YC3041 strain in a fermenter: The liquid seeds are inoculated into the ISP4 liquid culture medium in the fermenter at a ratio of 10% (V / V). The culture conditions in the 500-1000 liter fermenter are controlled at: temperature 30-37°C, stirring speed 150-180rpm, and fermentation time 5-7 days.

[0041] Preparation of YC3041 strain inoculant: The bacteria and its metabolites obtained by fermentation tank culture are mixed with an appropriate amount of soluble starch, dried or air-dried at 50℃-65℃ until the moisture content is less than 5%, and then crushed. The viable bacterial count of YC3041 strain spores in the inoculant must be 1×108 Pieces / gram or more.

[0042] 2. Field effect of YC3041 fungicide on controlling tobacco root-knot nematode disease

[0043] Test location: tobacco fields seriously infested with root-knot nematodes in Dafang County, Guizhou Province.

[0044] Experimental crops: tobacco (variety: Yunnan 87).

[0045] Test agent: YC3041 bacterial agent, with a viable count of 2.5×10 8 Pieces / g, prepared according to the above method of the present invention; 10% thiazolyl granules (Shandong United Pesticide Industry Co., Ltd.).

[0046] Experimental method: There are three treatments as follows, each with 3 replicates and 60 plants in each replicate.

[0047] Treatment 1: YC3041 fungicide 2 kg / mu. Dissolve the fungicide in about 100 kg of water, mix well, soak the roots of tobacco seedlings in the solution for about 10 minutes, then transplant, and evenly water the remaining solution on the roots of tobacco plants.

[0048] Treatment 2: Apply 10% thiamethoxam granules in holes, 2.5 g / plant.

[0049] Treatment 3: blank control without any nematicide application.

[0050] Survey and statistical methods: After 120 days, investigate the root nodule disease index of the plants (0: no nodules; 1: 1-20% of the roots have nodules; 2: 21-40% of the roots have nodules; 3: 41-60% of the roots have nodules; 4: 61-80% of the roots have nodules; 5: 81-100% of the roots have nodules), and calculate the disease index and prevention effect according to the following formula:

[0051] Disease index = (n1×1+n2×2+n3×3+n4×4+n5×5) / (S×5)×100, n1-n5 represent the total number of plants corresponding to root nodule disease index level 1-5, and S represents the total number of plants surveyed.

[0052] Preventive effect (%) = 100 (1-x / y), x and y are the disease indexes of the treated and control groups respectively.

[0053] Test results: Table 1 shows that applying 2 kg of YC3041 per mu has a control effect of 76.1% on tobacco root-knot nematode disease, which is equivalent to the control effect (78.1%) of applying 2 kg of 10% thiazolyl granules per mu.

[0054] Table 1. Field efficacy of YC3041 fungicide against tobacco root knot nematode disease

[0055]

[0056] Note: The same letter after the data in the same column means that the difference between the two is not statistically significant, otherwise it is significant.

[0057] 3. Field effect of YC3041 fungicide on the control of tobacco black shank disease

[0058] Test location: Tobacco fields with serious black shank disease in Dafang County, Guizhou Province.

[0059] Experimental crops: tobacco (variety: Yunnan 87).

[0060] Test agent: YC3041 bacterial agent, with a viable count of 2.5×10 8 Pieces / g, prepared according to the above method of the present invention; 58% metalaxyl mancozeb (Xi'an Dingsheng Biochemical Co., Ltd.).

[0061] Experimental method: There are three treatments as follows, each with 3 replicates and 60 plants in each replicate.

[0062] Treatment 1: YC3041 fungicide 2 kg / mu. Dissolve the fungicide in about 100 kg of water, mix well, soak the roots of tobacco seedlings in the solution for about 10 minutes, then transplant, and evenly water the remaining solution on the roots of tobacco plants.

[0063] Treatment 2: 58% metalaxyl mancozeb, 1 kg / mu, diluted 1000 times and irrigated the roots.

[0064] Treatment 3: blank control without any fungicide application.

[0065] Investigation and statistical methods: 90 days after application, the tobacco black shank disease grade was classified, and the disease index and prevention effect were calculated according to the method introduced in GB / T23222-2008 "Grading and Investigation Methods of Tobacco Pests and Diseases".

[0066] Test results: Table 2 shows that the application of 2 kg of YC3041 per mu has a control effect of 75.14% on tobacco black shank, which is significantly higher than the control effect of 1 kg of 58% metalaxyl mancozeb per mu (70.75%).

[0067] Table 2. Field efficacy of YC3041 fungicide against tobacco black shank

[0068]

[0069] Note: The same letter after the data in the same column means that the difference between the two is not statistically significant, otherwise it is significant.

[0070] 4. Field effect of YC3041 fungicide on tobacco bacterial wilt

[0071] Test location: tobacco fields with severe tobacco wilt in Dafang County, Guizhou Province.

[0072] Experimental crops: tobacco (variety: Yunnan 87).

[0073] Test agent: YC3041 bacterial agent, with a viable count of 2.5×10 8 pieces / gram, prepared according to the above method of the present invention; Qingkuling (Shanghai Gunong Biotechnology Co., Ltd.).

[0074] Experimental method: There are three treatments as follows, each with 3 replicates and 60 plants in each replicate.

[0075] Treatment 1: YC3041 fungicide 2 kg / mu. Dissolve the fungicide in about 100 kg of water, mix well, soak the roots of tobacco seedlings in the solution for about 10 minutes, then transplant, and evenly water the remaining solution on the roots of tobacco plants.

[0076] Treatment 2: Qingkuling, 1000 ml / mu, diluted 1000 times and irrigated the roots.

[0077] Treatment 3: blank control without any fungicide application.

[0078] Investigation and statistical methods: 90 days after application, classify tobacco bacterial wilt according to the method described in GB / T23222-2008 "Grading and Investigation Methods of Tobacco Pests and Diseases", and calculate the disease index and prevention effect.

[0079] Test results: Table 3 shows that applying 2 kg of YC3041 per mu has a control effect of 76.19% on tobacco bacterial wilt, which is significantly higher than the control effect of applying 1000 ml of YC3041 per mu (74.37%).

[0080] Table 3. Field efficacy of YC3041 fungicide against tobacco bacterial wilt

[0081]

[0082] Note: The same letter after the data in the same column means that the difference between the two is not statistically significant, otherwise it is significant.

[0083] 5. Field effect of YC3041 fungicide on tobacco bacterial wilt

[0084] Test location: Tobacco fields with serious root-knot nematode complex disease in Dafang County, Guizhou Province.

[0085] Experimental crops: tobacco (variety: Yunnan 87).

[0086] Test agent: YC3041 bacterial agent, with a viable count of 2.5×10 8Pieces / gram, prepared according to the above method of the present invention; 58% metalaxyl mancozeb (Xi'an Dingsheng Biochemical Co., Ltd.), chloranil (Shanghai Gunong Biotechnology Co., Ltd.), 10% thiazolyl granules (Shandong United Pesticide Industry Co., Ltd.).

[0087] Experimental method: There are three treatments as follows, each with 3 replicates and 100 plants in each replicate.

[0088] Treatment 1: YC3041 fungicide 3 kg / mu. Dissolve the fungicide in about 100 kg of water, mix well, soak the roots of tobacco seedlings in the solution for about 10 minutes, then transplant, and evenly water the remaining solution on the roots of tobacco plants.

[0089] Treatment 2: Mixed use of chemical pesticides (10% thiamethoxam granules, 2.5 g / plant, hole application; 58% metalaxyl mancozeb 1 kg / mu, diluted 1000 times and irrigated with roots; 1000 ml / mu of chloranil, diluted 1000 times and irrigated with roots).

[0090] Treatment 3: blank control without any fungicide application.

[0091] Investigation and statistical methods: 90 days after application, classify the disease levels of tobacco root-knot nematode disease, black shank disease and bacterial wilt disease according to the above method, and calculate the disease index and prevention effect.

[0092] Test results: Table 4 shows that the application of 3 kg of YC3041 per mu has a control effect of 70.54%, 72.65% and 71.32% on tobacco root-knot nematode disease, bacterial wilt and black shank disease respectively; the control effect of the three chemical pesticides on these three diseases is 6.43%, 73.31% and 73.54% respectively. In the prevention and control of tobacco black shank disease and bacterial wilt, the control effect of YC3041 is equivalent to that of the chemical pesticides; in the prevention and control of tobacco root-knot nematode disease, the control effect of YC3041 is significantly higher than that of the chemical pesticides.

[0093] Table 4. Field efficacy of YC3041 fungicide against tobacco root-knot nematode complex disease

[0094]

[0095]

[0096] Note: The same letter after the data in the same column means that the difference between the two is not statistically significant, otherwise it is significant.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A YC3041 strain, characterized in that The taxonomic name of the YC3041 strain is Streptomyces pratensis, and its deposit number is GDMCC No: 64828.

2. The fermentation culture of the YC3041 strain according to claim 1.

3. A method for preparing the fermentation culture of the YC3041 strain according to claim 2, comprising the following steps: (1) Activation of strains: The YC3041 strain was inoculated onto the slant of ISP4 solid culture medium in a test tube and cultured at 30-37°C to obtain slant strains; (2) Fermentation culture: The activated strain was inoculated into ISP4 liquid culture medium, and cultured at 28-36° C. and 120-180 rpm to obtain a fermentation culture of the YC3041 strain; The ISP4 solid culture medium includes 10 g / L soluble starch, 1 g / L peptone, 0.5 g / L yeast extract, 2 g / L (NH4)2SO4, 1 g / L MgSO4, 1 g / L K2HPO4, 1 g / L NaCl, 2 g / L CaCO3, and 18 g / L agar.

4. A bacterial agent, characterized in that The bacterial agent contains the YC3041 strain according to claim 1, or the fermentation culture of the YC3041 strain according to claim 2.

5. A pesticide complex, characterized in that: The pesticide complex contains the bacterial agent according to claim 4.

6. Use of the YC3041 strain according to claim 1, or the fermented culture of the YC3041 strain according to claim 2, or the bacterial agent according to claim 4, or the pesticide complex according to claim 5 in controlling at least one of root-knot nematodes, tobacco phytophthora, or Ralstonia solanacearum.

7. Use of the YC3041 strain according to claim 1, or the fermented culture of the YC3041 strain according to claim 2, or the bacterial agent according to claim 4, or the pesticide complex according to claim 5 in preventing and controlling at least one of tobacco root-knot nematode disease, tobacco bacterial wilt or tobacco black shank disease.

8. Use of the YC3041 strain according to claim 1, or the fermented culture of the YC3041 strain according to claim 2, or the bacterial agent according to claim 4, or the pesticide complex according to claim 5 in preventing and controlling complex diseases caused by tobacco root-knot nematode disease, tobacco bacterial wilt and tobacco black shank disease.

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