Biocontrol bacterium DXQ-1 for preventing and treating leaf spot disease of davidia involucrata and application method of biocontrol bacterium DXQ-1

Abstract

The invention discloses a biocontrol bacterium DXQ-1 for preventing and treating davidia involucrata leaf spot and an application method of the biocontrol bacterium DXQ-1. The pathogenic bacteria of the davidia involucrata leaf spot are pyricularia oryzae. The biocontrol bacterium DXQ-1 is bacillus obtained by screening and identifying microorganisms of bacterial strains which are selected from healthy davidia involucrata rhizosphere soil and have a bacteriostatic effect on pyricularia oryzae through a plate confrontation experiment. The application of the biocontrol bacterium DXQ-1 comprises the following steps: uniformly inoculating prepared DXQ-1 fermentation liquor to davidia involucrata so as to prevent and treat the davidia involucrata leaf spot disease, and after fermentation conditions of the DXQ-1 fermentation liquor are optimized, determining that a fermentation method is fermentation for 30 hours through an LB culture medium. The bacillus subtilis DXQ-1 is subjected to strain separation, identification and preparation, the application of the DXQ-1 strain in the aspects of prevention and control and broad-spectrum bacteriostasis of the davidia involucrata leaf spot disease is determined, development and application of biological pesticides in the future are facilitated, and the progress of biological prevention and control is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of biological control, and in particular to a biological control bacterium DXQ-1 for controlling Davidia involucrata leaf spot disease and an application method thereof. Background Art

[0002] Davidia involucrata is a relict plant, known as a "living fossil of plants", and is also a world-famous ornamental plant. It is named "Chinese Dove Tree" by Western botanists because its flower shape resembles a flying white dove. However, due to the destruction of the forest environment, its number is small and its distribution range is shrinking. At the same time, Davidia involucrata in the natural environment is also prone to fungal diseases of varying degrees, such as leaf spot caused by Pyricularia oryzae.

[0003] At present, the control of plant diseases mainly relies on chemical control. Synthetic fungicides can significantly reduce the severity of diseases; however, excessive use of chemical fungicides usually leads to drug resistance of pathogens and environmental pollution problems, which can easily destroy the original ecological balance of Davidia involucrata. In order to solve these problems, it is very important to develop safe and environmentally friendly alternative antimicrobial agents. Biological control is currently the fastest growing field in the prevention and control of plant diseases.

[0004] Biological control generally refers to the use of living microorganisms or their metabolically active substances to control pathogens, pests and weeds, as well as measures to regulate plant growth to prevent or treat plant diseases. It has the characteristics of stable and obvious effects, less selective pressure on the environment, and is not easy to make target pathogens resistant. It is a new, safe and efficient method of plant disease control that can effectively address the limitations of chemical control.

[0005] Among them, Bacillus is widely distributed, has strong environmental tolerance, can produce a variety of metabolites, and has strong stability and compatibility of Bacillus biocontrol agents. It is currently the most studied type of biocontrol bacteria for biological control of plant diseases. Bacillus has become a hot spot in biological control research in recent years due to its many advantages such as heat resistance, stress resistance, and environmental friendliness. At the same time, although the research on biocontrol Bacillus against diseases has achieved many results, the industrialization process of biocontrol still has a long way to go. It still requires technology owners and production units to devote more time and energy to realize the industrialization process of biocontrol technology from research results to mass production and even practical application. Summary of the invention

[0006] The purpose of the present invention is to provide a biocontrol bacterium DXQ-1 for preventing and controlling Davidia involucrata leaf spot disease and an application method thereof, aiming to discover effective antagonistic bacteria from the in situ living environment of Davidia involucrata and protect Davidia involucrata without destroying the original ecological environment balance.

[0007] To achieve the above object, the present invention provides the following technical solution: a biocontrol bacterium DXQ-1 for preventing and controlling Davidia involucrata leaf spot disease, wherein the pathogen of Davidia involucrata leaf spot disease is Pyricularia oryzae;

[0008] The biocontrol bacteria DXQ-1 is a Bacillus obtained by selecting strains with antibacterial effects on Pyricularia oryzae in the rhizosphere soil of healthy Davidia involucrata through a plate confrontation experiment and performing microbial screening and identification;

[0009] The specific process of screening and identifying the biocontrol bacteria DXQ-1 is as follows:

[0010] Firstly, the strains isolated from the rhizosphere soil of healthy Davidia involucrata were subjected to a plate confrontation test with Pyrrospora oryzae, and the strains with antibacterial activity were observed and recorded to screen the antagonistic strains.

[0011] Then, according to the antagonistic effect of the bacteria on Pyricularia oryzae, the strains of Bacillus were selected, the inhibition rate was statistically analyzed, and the strain with the highest inhibition rate was selected for subsequent identification. The bacteria were identified as Bacillus subtilis through morphological and molecular biological methods.

[0012] It was selected as the biocontrol bacterium DXQ-1 for fermentation broth culture and control application.

[0013] Preferably, the plate confrontation test process specifically includes first inoculating the Davidia involucrata leaf spot disease cake on the prepared CM plate, culturing at a constant temperature for 4 days, inoculating the isolated strain around the plate 20 mm away from the Davidia involucrata leaf spot disease cake, culturing at a constant temperature of 28°C and inverting, and observing and recording the strains with antibacterial activity after 2 days.

[0014] Preferably, the morphological identification includes observing the colony morphology of DXQ-1, observing individual bacteria under a scanning electron microscope and observing the antagonistic strain under an optical microscope, and verifying that the strain meets the morphological characteristics of the genus Bacillus through morphological observation.

[0015] Preferably, the molecular biological identification is performed by amplifying the 16S rRNA sequence of DXQ-1, then using the website NCBI for blast comparison, and using the software MEGA to construct a phylogenetic tree, and then performing molecular biological identification. Combining the morphological and molecular biological identification results, DXQ-1 is identified as Bacillus subtilis.

[0016] The invention discloses an application of a biocontrol bacterium DXQ-1 for preventing and controlling leaf spot disease of Davidia involucrata. The application of the biocontrol bacterium DXQ-1 comprises the following steps: uniformly inoculating a prepared DXQ-1 fermentation liquid onto Davidia involucrata for preventing and treating the leaf spot disease of Davidia involucrata. After the fermentation conditions of the DXQ-1 fermentation liquid are optimized, the fermentation method is determined to be fermentation in LB medium for 30 hours.

[0017] Preferably, the DXQ-1 fermentation conditions include the selection of a fermentation medium and the determination of a fermentation time. The fermentation medium is one of LB medium, NB medium and PDB medium, and the fermentation time is 30-120 hours.

[0018] Preferably, the DXQ-1 fermentation condition optimization is carried out by experiments. First, 2 mL of DXQ-1 seed solution is added to LB medium, NB medium or PDB medium after sterilization, and 5 portions of each medium are prepared. The medium is cultured in an oscillating incubator at 28°C and 180 r / min for 30 h, 48 h, 80 h, 96 h, and 120 h, respectively. The fermentation broth is filtered and sterilized with a filter with a pore size of 0.22 μm. The obtained filtrate is mixed with CM medium at a volume ratio of 10% and poured into a plate. After the plate solidifies, a rice black pear spore cake with a diameter of 8 mm and the same growth is inoculated in the center of the plate. After constant temperature culture at 28°C for 5 days, the diameter of the rice black pear spore cake is measured, and the antibacterial activity at the fermentation temperature of different fermentation mediums and fermentation times is determined to obtain the optimal culture medium and fermentation conditions. The LB fermentation broth has the highest inhibition rate on Davidia involucrata leaf spot pathogen, and the hyphae are in a collapsed and broken state. It has a good prevention effect after fermentation for 30 hours.

[0019] Preferably, the application of the DXQ-1 fermentation broth also requires good stability and prevention effect under high temperature and ultraviolet rays. The stability analysis of the DXQ-1 fermentation broth is carried out by experiment. First, DXQ-1 is cultured according to the optimal culture medium and fermentation conditions obtained by previous screening to obtain 100 mL of fermentation broth and sterilize it by filtration with a filter with a pore size of 0.22 μm. Take 5 tubes of 10 mL of fermentation broth and place them at 28°C, 38°C, 48°C, 58°C, and 68°C for 1 hour, and use the fermentation broth without heating treatment as a control, and then use the drug plate method to determine the antibacterial activity of the treated fermentation filtrate. Similarly, 5 tubes of 10 mL of fermentation broth were irradiated under ultraviolet light for 10 minutes, 30 minutes, 1 hour, 2 hours, and 4 hours, and the fermentation broth not treated with ultraviolet rays was used as a control, and then the antibacterial activity of the treated fermentation filtrate was determined by the drug plate method.

[0020] Preferably, the DXQ-1 fermentation liquid has a good preventive and therapeutic effect on Davidia involucrata leaf spot. The DXQ-1 fermentation liquid is used to perform an in vitro leaf inoculation experiment on Davidia involucrata leaf spot, and the experimental process is as follows: taking Davidia involucrata leaves for poking and inoculation; pressing the surface of the Davidia involucrata leaves with a 10 μL gun tip to produce a wound, and then placing it in a 6-BA (1 mg / L, pH 7.0) solution, paying attention to keeping the pressing force as consistent as possible; scraping the conidia produced by the rice blast fungus on the CM culture medium, removing impurities and hyphae with a filter cloth, counting and adjusting the spore concentration to 1×105 / mL with a hemocytometer; mixing the DXQ-1 fermentation filtrate with the spore liquid, dripping 5 μL of the mixed liquid on each wound, and using sterile water and spore liquid as the control group; then placing the inoculated leaves and the control group in an artificial climate chamber and placing them in the dark for 12 hours; then transferring them to a 12-hour light / 12-hour dark environment for continued placement for 5-7 days, observing the incidence of the wound, taking pictures and measuring the size of the lesions.

[0021] Preferably, the application of the biocontrol bacteria DXQ-1 also includes the fermentation liquid of Bacillus DXQ-1, which also has antibacterial effect on other fungi, and is used as a broad-spectrum antibacterial agent for preventing and controlling fungal diseases of grain crops;

[0022] Through the fermentation liquid drug-carrying plate method, 10mL of DXQ-1 fermentation liquid was added to 90mL of CM culture medium and then poured onto the plate. A fungus block containing pathogenic fungi was inoculated in the center of the plate and the inhibition was observed after growing for several days. The pathogenic fungi selected were sheath blight, gibberella, and corn leaf blight. The fermentation liquid had a certain inhibitory effect on rice sheath blight, wheat gibberella, rice blast, and corn leaf blight.

[0023] Compared with the prior art, the invention has the following beneficial effects: the biocontrol bacteria DXQ-1 for preventing and controlling leaf spot disease of Davidia involucrata and the application method thereof are prepared by separating and identifying the strain of Bacillus subtilis DXQ-1 to obtain the biocontrol bacteria DXQ-1 for preventing and controlling leaf spot disease of Davidia involucrata; the fermentation liquid of DXQ-1 has a good inhibitory effect on the pathogenicity of Pyricularia oryzae, and can effectively inhibit the occurrence of leaf spot disease of Davidia involucrata; the strain DXQ-1 has the ability to antagonize the pathogenic bacteria of Pyricularia oryzae, and also has good broad-spectrum resistance to various plant pathogens. The DXQ-1 fermentation liquid has a certain inhibitory effect on rice sheath blight, wheat gibberella, rice blast fungus, and corn leaf blight, and the fermentation liquid stability analysis results show that the fermentation liquid has good stability and prevention effect under different temperatures and ultraviolet treatments, indicating that DXQ-1 has the potential for large-scale outdoor applications in the next step and has certain research value. The present invention determines the application of DXQ-1 strains in the prevention and control of Davidia involucrata leaf spot disease and broad-spectrum antibacterial properties, which is beneficial to the future development and application of biological pesticides and helps to promote the progress of biological control. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1Schematic diagram of leaf spot infected leaves and the pathogen Pyrrospora oryzae;

[0025] Figure 2 It is a schematic diagram of a plate confrontation test of the biocontrol bacteria DXQ-1 of the present invention;

[0026] Figure 3 This is a schematic diagram of observing DXQ-1 colonies under an optical microscope of the present invention;

[0027] Figure 4 This is a schematic diagram of observing the DXQ-1 strain under a scanning electron microscope of the present invention;

[0028] Figure 5 This is a schematic diagram of the molecular biological identification of the DXQ-1 strain of the present invention;

[0029] Figure 6 It is a schematic diagram of the inhibitory effect of the antagonistic bacteria fermentation liquid of the present invention on Davidia involucrata 11-1;

[0030] Figure 7 This is a schematic diagram of the comparison of hyphae after DXQ-1 of the present invention confronts Davidia involucrata 11-1;

[0031] Figure 8 This is a schematic diagram showing the comparison of the protective effects of DXQ-1 of the present invention under different fermentation media and fermentation times;

[0032] Fig. 9 This is a schematic diagram showing the comparison of the protective effects of DXQ-1 of the present invention at different fermentation times in LB medium;

[0033] Fig.10 This is a schematic diagram of the control effect of DXQ-1 of the present invention on Davidia involucrata leaf spot disease on detached leaves;

[0034] Fig.11 This is a schematic diagram comparing the stability of DXQ-1 fermentation broth under different temperature treatments of the present invention;

[0035] Fig.12 This is a schematic diagram of the stability analysis of DXQ-1 fermentation broth under different temperature treatments of the present invention;

[0036] Fig.13 This is a schematic diagram comparing the stability of DXQ-1 fermentation broth under ultraviolet treatment time of the present invention;

[0037] Fig.14 It is a schematic diagram of the stability analysis of DXQ-1 fermentation broth under ultraviolet treatment time of the present invention;

[0038] Fig.15 It is a schematic diagram of the inhibitory effect of the fermentation liquid of the present invention on rice sheath blight, wheat gibberella, rice blast fungus and corn leaf blight. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] See also Figure 1-15 The present invention provides a technical solution: a biocontrol bacterium DXQ-1 for preventing and controlling Davidia involucrata leaf spot disease. The laboratory previously identified the pathogen of Davidia involucrata leaf spot disease as Figure 1 The shown leaf of Pyricularia oryzae is 11-1;

[0041] The biocontrol bacteria DXQ-1 is a Bacillus obtained by selecting strains with antibacterial effects on Pyricularia oryzae in the rhizosphere soil of healthy Davidia involucrata through a plate confrontation experiment and performing microbial screening and identification;

[0042] The specific process of screening and identifying the biocontrol bacteria DXQ-1 is as follows:

[0043] Firstly, the strains isolated from the rhizosphere soil of healthy Davidia involucrata were subjected to a plate confrontation test with Pyrrospora oryzae, and the strains with antibacterial activity were observed and recorded to screen the antagonistic strains.

[0044] The plate confrontation test process specifically includes first inoculating the Davidia involucrata leaf spot pathogen cake on the prepared CM plate, culturing at a constant temperature for 4 days, inoculating the isolated strains 20 mm away from the Davidia involucrata leaf spot pathogen cake on all sides of the plate, culturing at a constant temperature of 28°C, and observing and recording the strains with antibacterial activity after 2 days. Figure 2 shown.

[0045] Then, according to the antagonistic effect of the bacteria on Pyricularia oryzae, the strains of Bacillus were selected, the inhibition rate was statistically analyzed, and the strain with the highest inhibition rate was selected for subsequent identification. The bacteria were identified as Bacillus subtilis through morphological and molecular biological methods.

[0046] The morphological identification includes observing the colony morphology of DXQ-1, observing the single bacteria under a scanning electron microscope and observing the antagonistic strain under an optical microscope, and verifying that the strain meets the morphological characteristics of the genus Bacillus through morphological observation. The results are as follows: Figure 3-4 shown.

[0047] The molecular biological identification was performed by amplifying the 16S rRNA sequence of DXQ-1, then using the website NCBI for blast comparison, and using the software MEGA to construct a phylogenetic tree, and molecular biological identification was performed. Combining the morphological and molecular biological identification results, DXQ-1 was identified as Bacillus subtilis. The results are as follows Figure 5 shown.

[0048] It was selected as the biocontrol bacterium DXQ-1 for fermentation broth culture and control application.

[0049] The application of the biocontrol bacteria DXQ-1 includes uniformly inoculating the prepared DXQ-1 fermentation liquid onto Davidia involucrata for preventing and treating Davidia involucrata leaf spot disease, and after the fermentation conditions of the DXQ-1 fermentation liquid are optimized, the fermentation method is determined to be fermented in LB medium for 30 hours.

[0050] The DXQ-1 fermentation conditions include the selection of a fermentation medium and the determination of a fermentation time. The fermentation medium is one of LB medium, NB medium and PDB medium, and the fermentation time is 30-120 hours.

[0051] The optimization of the DXQ-1 fermentation conditions is carried out through experiments. First, after sterilization, 2 mL of DXQ-1 seed solution is added to LB medium, NB medium or PDB medium respectively, and 5 portions of each medium are prepared. The medium is cultured in an oscillating incubator at 28° C. and 180 r / min for 30 h, 48 h, 80 h, 96 h, and 120 h, respectively. The fermentation broth is filtered and sterilized with a filter with a pore size of 0.22 μm. The obtained filtrate is mixed with CM medium at a volume ratio of 10% and poured into a plate. After the plate solidifies, a rice black pear spore cake with a diameter of 8 mm and the same growth potential is inoculated in the center of the plate. After constant temperature culture at 28° C. for 5 days, the diameter of the rice black pear spore cake is measured, and the antibacterial activity at the fermentation temperature of different fermentation mediums and fermentation times is judged to obtain the optimal culture medium and fermentation conditions. Figure 6-9 As shown, LB fermentation liquid has the highest inhibition rate against Davidia involucrata leaf spot pathogen, the mycelium is in a collapsed and broken state, and it has a good prevention effect after fermentation for 30 hours.

[0052] The application of the DXQ-1 fermentation broth also requires good stability and protection under high temperature and ultraviolet rays. The stability analysis of the DXQ-1 fermentation broth is carried out by experiment. First, DXQ-1 is cultured according to the optimal culture medium and fermentation conditions obtained by previous screening to obtain 100 mL of fermentation broth and sterilize it by filtration with a filter with a pore size of 0.22 μm. Take 5 tubes of 10 mL of fermentation broth and place them at 28°C, 38°C, 48°C, 58°C, and 68°C for 1 hour, and use the fermentation broth without heating treatment as a control, and then use the drug-plated plate method to determine the antibacterial activity of the treated fermentation filtrate. Similarly, 5 tubes of 10 mL of fermentation broth were irradiated under ultraviolet light for 10 minutes, 30 minutes, 1 hour, 2 hours, and 4 hours, and the fermentation broth not treated with ultraviolet rays was used as a control, and then the antibacterial activity of the treated fermentation filtrate was determined by the drug-plated plate method.

[0053] To determine whether the fermentation broth of DXQ-1 is stable, we treated the fermentation broth of DXQ-1 at different temperatures ranging from 40℃ to 120℃. Figure 11-12 As shown in Figure 2, the antibacterial activity of the fermentation broth remained basically unchanged as the treatment temperature increased, indicating that the DXQ-1 fermentation broth had strong thermal stability and the activity of the antibacterial substances would not be lost due to the increase in temperature.

[0054] The DXQ-1 fermentation liquid was irradiated with ultraviolet light, and the inhibitory effect on Pyricularia oryzae was as follows: Figure 13-14 As shown in the figure, with the increase of irradiation time, the antibacterial activity of the fermentation broth remained basically unchanged, indicating that the DXQ-1 fermentation broth was not sensitive to ultraviolet light and had strong stability.

[0055] The DXQ-1 fermentation liquid has a good preventive and therapeutic effect on Davidia involucrata leaf spot disease. The DXQ-1 fermentation liquid is used to perform an in vitro leaf inoculation experiment on Davidia involucrata leaf spot disease, and the experimental process is as follows: taking Davidia involucrata leaves for poking and inoculation; pressing the surface of the Davidia involucrata leaves with a 10 μL gun tip to produce a wound, and then placing it in a 6-BA (1 mg / L, pH 7.0) solution, paying attention to keeping the pressing force as consistent as possible; scraping the conidia produced by the rice blast fungus on the CM culture medium, removing impurities and hyphae with a filter cloth, counting and adjusting the spore concentration to 1×105 / mL with a hemocytometer; mixing the DXQ-1 fermentation filtrate with the spore liquid, dripping 5 μL of the mixed liquid on each wound, and sterile water and spore liquid as the control group; then placing the inoculated leaves and the control group in an artificial climate chamber and placing them in the dark for 12 hours; then transferring them to a 12-hour light / 12-hour dark environment for continued placement for 5-7 days, observing the incidence of the wound, taking pictures and measuring the size of the lesions.

[0056] Through the indoor in vitro leaf poke dripping experiment of Davidia involucrata, the length of the lesions on the leaves after fermentation liquid treatment was measured to explore the leaf spot control effect of the biocontrol fungus DXQ-1. Fig.10 As shown in the experimental results, it can be seen that the length of the lesions after treatment with DXQ-1 fermentation liquid is significantly smaller than that of the spore liquid control group, indicating that DXQ-1 fermentation liquid has a good inhibitory effect on the pathogenicity of Pyricularia oryzae and can effectively inhibit the occurrence of leaf spot disease.

[0057] The application of the biocontrol bacteria DXQ-1 also includes the fermentation liquid of Bacillus DXQ-1 also having antibacterial effect on other fungi, and being used as a green control agent for preventing and controlling fungal diseases of grain crops and having a broad-spectrum antibacterial effect;

[0058] By using the fermentation broth with drug plate method, 10 mL of DXQ-1 fermentation broth was added to 90 mL of CM medium and then poured into a plate. A fungus block containing pathogenic fungi was inoculated in the center of the plate and the inhibition was observed after several days of growth. The results are as follows: Fig.15As shown, the pathogenic fungi were selected as Sheath Blight, Gibberella, and Corn Leaf Spot, and the fermentation liquid had a certain inhibitory effect on Rice Sheath Blight, Wheat Gibberella, Rice Blast, and Corn Leaf Spot.

[0059] Contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field. Although the embodiments of the present invention have been shown and described, it is understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A biocontrol bacterium DXQ-1 for preventing and controlling Davidia involucrata leaf spot disease, characterized in that: The pathogen of Davidia involucrata leaf spot disease is Pyrrospora oryzae; The biocontrol bacteria DXQ-1 is a Bacillus obtained by selecting strains with antibacterial effects on Pyricularia oryzae in the rhizosphere soil of healthy Davidia involucrata through a plate confrontation experiment and performing microbial screening and identification; The specific process of screening and identifying the biocontrol bacteria DXQ-1 is as follows: Firstly, the strains isolated from the rhizosphere soil of healthy Davidia involucrata were subjected to a plate confrontation test with Pyrrospora oryzae, and the strains with antibacterial activity were observed and recorded to screen the antagonistic strains. Then, according to the antagonistic effect of the bacteria on Pyricularia oryzae, the strains of Bacillus were selected, the inhibition rate was statistically analyzed, and the strain with the highest inhibition rate was selected for subsequent identification. The bacteria were identified as Bacillus subtilis through morphological and molecular biological methods. It was selected as the biocontrol bacterium DXQ-1 for fermentation broth culture and control application.

2. The biocontrol bacterium DXQ-1 for controlling Davidia involucrata leaf spot according to claim 1, characterized in that: The plate confrontation test process specifically includes first inoculating the Davidia involucrata leaf spot pathogen cake on the prepared CM plate, culturing at a constant temperature for 4 days, inoculating the isolated strain around the plate 20 mm away from the Davidia involucrata leaf spot pathogen cake, culturing at a constant temperature of 28°C, and observing and recording the strains with antibacterial activity after 2 days.

3. The biocontrol bacterium DXQ-1 for controlling Davidia involucrata leaf spot according to claim 1, characterized in that: The morphological identification includes observing the colony morphology of DXQ-1, observing individual bacteria under a scanning electron microscope and observing the antagonistic strain under an optical microscope, and verifying that the strain meets the morphological characteristics of the genus Bacillus through morphological observation.

4. The biocontrol bacterium DXQ-1 for controlling Davidia involucrata leaf spot according to claim 1, characterized in that: The molecular biological identification was performed by amplifying the 16S rRNA sequence of DXQ-1, then using the website NCBI for blast comparison, and using the software MEGA to construct a phylogenetic tree for molecular biological identification. Based on the morphological and molecular biological identification results, DXQ-1 was identified as Bacillus subtilis.

5. An application of the biocontrol bacterium DXQ-1 for preventing and controlling Davidia involucrata leaf spot disease, characterized in that: The application of the biocontrol bacteria DXQ-1 includes uniformly inoculating the prepared DXQ-1 fermentation liquid onto Davidia involucrata for preventing and treating Davidia involucrata leaf spot disease, and after the fermentation conditions of the DXQ-1 fermentation liquid are optimized, the fermentation method is determined to be fermented in LB medium for 30 hours.

6. The use of the biocontrol bacteria DXQ-1 for preventing and controlling Davidia involucrata leaf spot according to claim 5, characterized in that: The DXQ-1 fermentation conditions include the selection of a fermentation medium and the determination of a fermentation time. The fermentation medium is one of LB medium, NB medium and PDB medium, and the fermentation time is 30-120 hours.

7. The use of the biocontrol bacteria DXQ-1 for preventing and controlling Davidia involucrata leaf spot according to claim 6, characterized in that: The optimization of the DXQ-1 fermentation conditions is carried out through experiments. First, 2 mL of DXQ-1 seed solution is added to LB medium, NB medium or PDB medium after sterilization, and 5 portions of each medium are prepared. The medium is cultured in an oscillating incubator at 28° C. and 180 r / min for 30 h, 48 h, 80 h, 96 h and 120 h, respectively. The fermentation liquid is filtered and sterilized with a filter with a pore size of 0.22 μm. The obtained filtrate is mixed with CM medium at a volume ratio of 10% and poured into a plate. After the plate solidifies, a rice black pear spore cake with a diameter of 8 mm and the same growth potential is inoculated in the center of the plate. After constant temperature culture at 28° C. for 5 days, the diameter of the rice black pear spore cake is measured, and the antibacterial activity at the fermentation temperature of different fermentation mediums and fermentation times is determined to obtain the optimal culture medium and fermentation conditions. The LB fermentation liquid has the highest inhibition rate on the leaf spot pathogen of Davidia involucrata, and the hyphae are in a collapsed and broken state. It has a good prevention effect after fermenting for 30 hours.

8. The use of the biocontrol bacteria DXQ-1 for preventing and controlling Davidia involucrata leaf spot according to claim 5, characterized in that: The application of the DXQ-1 fermentation broth also requires good stability and protective effect under high temperature and ultraviolet rays. The stability analysis of the DXQ-1 fermentation broth is carried out through experiments. First, DXQ-1 is cultured according to the optimal culture medium and fermentation conditions obtained by previous screening to obtain 100 mL of fermentation broth and filter and sterilize it with a filter with a pore size of 0.22 μm; 5 tubes of 10 mL of fermentation broth are placed at 28°C, 38°C, 48°C, 58°C, and 68°C for 1 hour, and the fermentation broth without heating treatment is used as a control. Then, the antibacterial activity of the treated fermentation filtrate is determined by the drug-containing plate method; similarly, 5 tubes of 10 mL of fermentation broth are irradiated under ultraviolet light for 10 minutes, 30 minutes, 1 hour, 2 hours, and 4 hours, and the fermentation broth without ultraviolet treatment is used as a control. Then, the antibacterial activity of the treated fermentation filtrate is determined by the drug-containing plate method.

9. The use of the biocontrol bacteria DXQ-1 for preventing and controlling Davidia involucrata leaf spot according to claim 5, characterized in that: The DXQ-1 fermentation liquid has a good preventive and therapeutic effect on Davidia involucrata leaf spot disease. The DXQ-1 fermentation liquid is used to perform an in vitro leaf inoculation experiment on Davidia involucrata leaf spot disease, and the experimental process is as follows: taking Davidia involucrata leaves for poking and inoculation; pressing the surface of the Davidia involucrata leaves with a 10 μL gun tip to produce a wound, and then placing it in a 6-BA (1 mg / L, pH 7.0) solution, paying attention to keeping the pressing force as consistent as possible; scraping the conidia produced by the rice blast fungus on the CM culture medium, removing impurities and hyphae with a filter cloth, counting and adjusting the spore concentration to 1×105 / mL with a hemocytometer; mixing the DXQ-1 fermentation filtrate with the spore liquid, dripping 5 μL of the mixed liquid on each wound, and sterile water and spore liquid as the control group; then placing the inoculated leaves and the control group in an artificial climate chamber and placing them in the dark for 12 hours; then transferring them to a 12-hour light / 12-hour dark environment for continued placement for 5-7 days, observing the incidence of the wound, taking pictures and measuring the size of the lesions.

10. The use of the biocontrol bacteria DXQ-1 for preventing and controlling Davidia involucrata leaf spot according to claim 5, characterized in that: The application of the biocontrol bacteria DXQ-1 also includes the fermentation liquid of Bacillus DXQ-1 also having antibacterial effect on other fungi, and being used as a green control agent for preventing and controlling fungal diseases of grain crops and having a broad-spectrum antibacterial effect; Through the fermentation liquid drug-carrying plate method, 10mL of DXQ-1 fermentation liquid was added to 90mL of CM culture medium and then poured onto the plate. A fungus block containing pathogenic fungi was inoculated in the center of the plate and the inhibition was observed after growing for several days. The pathogenic fungi selected were sheath blight, gibberella, and corn leaf blight. The fermentation liquid had a certain inhibitory effect on rice sheath blight, wheat gibberella, rice blast, and corn leaf blight.

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