Bacillus velez JSBV55 and biocontrol agent and preparation method and application thereof, and method for preventing and controlling garlic purple spot disease

Abstract

The invention relates to a Velez bacillus JSBV55 and a biocontrol agent and a preparation method and application thereof, and a method for preventing and treating garlic purple spot disease. The deposit number of the Velez bacillus strain JSBV55 is CGMCC NO.24637; the strain and the biocontrol agent containing the strain can effectively prevent and treat garlic purple spot disease. The invention has the advantages that, compared with chemical prevention and treatment, Velez bacillus JSBV55 and the biocontrol agent containing Velez bacillus JSBV55 can prevent and treat garlic purple spot disease, which belongs to biological prevention and treatment, has low toxicity, is degradable, and has no pollution to the environment. While effectively preventing and treating garlic purple spot disease, the green and sustainable development of the garlic industry is realized.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural biological control, in particular to Bacillus velez JSBV55 and a biological control agent, a preparation method and application thereof, and a method for controlling garlic purple spot disease. Background Art

[0002] In recent years, garlic purple spot disease (the pathogen of the disease is Alternaria alternata) has become one of the common diseases in garlic production. In years with frequent and heavy rainfall, the incidence of garlic purple spot disease is quite high. When the disease is serious, it often leads to garlic leaf death, premature aging of plants, reduced garlic yield, and garlic stalk rot, which directly affects the quality and yield of garlic, causing huge economic losses and affecting the cultivation and sustainable development of garlic.

[0003] At present, the prevention and control of garlic purple spot disease still refers to the prevention and control methods of other fungal diseases, mainly chemical prevention. The toxicity of the pesticides used varies, and some areas even use highly toxic pesticides, which seriously hinders the green and sustainable development of the garlic industry.

[0004] As an effective means of plant disease control, biological control is gaining more and more attention. The application of microbial antagonists to plant disease control has shown good disease control effects on a variety of crops such as cucumbers, peppers, rice, wheat, and corn.

[0005] However, there are few reports on the biological control of garlic purple spot disease. Summary of the invention

[0006] The invention aims to solve the technical problem that the toxicity of chemical agents is different in the process of controlling garlic purple spot disease, which seriously hinders the green and sustainable development of the garlic industry. The invention provides a Velez Bacillus JSBV55 and a biocontrol agent and a preparation method and application thereof, and a method for controlling garlic purple spot disease. The garlic purple spot disease is biologically controlled by Velez Bacillus JSBV55, and the green and sustainable development of the garlic industry is achieved while the garlic purple spot disease is effectively controlled.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a Bacillus Velezii strain JSBV55, whose deposit number is CGMCCNO.24637.

[0009] In a second aspect, the present invention provides a biocontrol agent comprising the Bacillus Velezii strain JSBV55 as described in the first aspect.

[0010] In some embodiments, it comprises at least one of the bacterial cells, spores and fermentation broth of the Bacillus Velezii strain JSBV55 as described in the first aspect;

[0011] Among them, in the fermentation broth of Bacillus velez strain JSBV55, the content of Bacillus velez strain JSBV55 is 10 7 ~10 9 cfu / mL.

[0012] In some embodiments, when the biocontrol agent comprises a fermentation broth of Bacillus Velezii strain JSBV55, the content of Bacillus Velezii strain JSBV55 in the fermentation broth is 10 8 cfu / mL.

[0013] In a third aspect, the present invention provides a method for preparing the biocontrol agent as described in the second aspect, comprising the following steps:

[0014] The pretreated Bacillus Velezii strain JSBV55 is fermented and cultured in LB medium to obtain a fermentation liquid containing the Bacillus Velezii strain JSBV55, which is a biocontrol agent.

[0015] In some embodiments, the steps include:

[0016] Pretreatment: Inoculate the Bacillus Velezii strain JSBV55 in LB medium, culture at 30-37°C in a dark environment for 24-32 hours and set aside.

[0017] In some embodiments, the steps include:

[0018] Pretreatment: Bacillus Velezii strain JSBV55 was inoculated into LB medium and cultured at 30°C in a dark environment for 24 hours before use.

[0019] In some embodiments, the steps include:

[0020] Fermentation culture: The pretreated Bacillus Velezii strain JSBV55 is inoculated into LB liquid culture medium for fermentation culture at a fermentation temperature of 30-37°C for 48-72 hours, and the culture is shaken at a rotation speed of 180-220 rpm to obtain a fermentation liquid containing the Bacillus Velezii strain JSBV55, which is the biocontrol agent.

[0021] In some embodiments, the steps include:

[0022] Fermentation culture: The pretreated Bacillus Velez strain JSBV55 was inoculated into LB liquid culture medium, and after shaking culture at a rotation speed of 180 rpm and a temperature of 30° C. in the dark for 48 hours, a fermentation liquid containing Bacillus Velez strain JSBV55 was obtained, and the fermentation liquid was the biocontrol agent.

[0023] In a fourth aspect, the present invention provides a use of the Bacillus Velezii strain JSBV55 as described in the first aspect or the biocontrol agent as described in the second aspect in preventing and controlling plant diseases.

[0024] The plant includes a plant of the genus Liliaceae or a plant of the genus Allium;

[0025] The pathogen of the plant disease is a pathogen of the genus Alternaria.

[0026] In some of these embodiments, the plant includes garlic;

[0027] The plant disease is garlic purple spot disease;

[0028] The pathogen of the plant disease is Alternaria alternata.

[0029] In a fifth aspect, the present invention provides a method for preventing and controlling garlic purple spot disease, comprising applying the biocontrol agent as described in the second aspect to the above-ground part of a plant suffering from garlic purple spot disease or to the root growth environment thereof.

[0030] The present invention adopts the above technical solution, and has the following technical effects compared with the prior art:

[0031] The invention discloses a Bacillus Velez JSBV55 and a biocontrol agent, a preparation method and application thereof, and a method for controlling garlic purple spot disease. Since Bacillus Velez JSBV55 has an antagonistic effect on the pathogenic bacteria Alternaria alternata of garlic purple spot disease, Bacillus Velez JSBV55 and a biocontrol agent containing Bacillus Velez JSBV55 can effectively control garlic purple spot disease. Compared with chemical control, Bacillus Velez JSBV55 and a biocontrol agent containing Bacillus Velez JSBV55 can control garlic purple spot disease, which belongs to biological control, has low toxicity, is degradable, and has no pollution to the environment. While effectively controlling garlic purple spot disease, the green and sustainable development of the garlic industry is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is a colony morphology diagram of Bacillus velezensis strain JSBV55 according to an embodiment of the present invention;

[0033] Figure 2This is a diagram showing the inhibitory effect of Bacillus velezensis strain JSBV55 on the mycelial growth of garlic purple spot pathogen according to an embodiment of the present invention, wherein the diameter of the culture dish is 9 cm;

[0034] Figure 3 This is a potted plant control effect diagram of Bacillus velezensis strain JSBV55 on garlic purple spot according to an embodiment of the present invention;

[0035] [Preservation information] Bacillus velezensis strain JSBV55, its preservation number is CGMCC NO.24637, the preservation date is April 6, 2022, the preservation unit is the General Microbiology Center of China Microorganism Culture Collection Administration (CGMCC), and the preservation unit address is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, Postal Code 100101. DETAILED DESCRIPTION

[0036] The following will be combined with the accompanying 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 in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work belong to the scope of protection of the present invention. The experimental methods without specific conditions in the following embodiments are usually measured according to national standards. The experimental materials without the source indicated in the following embodiments are all commercially available raw materials. The equipment used in each step in the following embodiments is conventional equipment. If there is no corresponding national standard, it is carried out according to the general international standards, conventional conditions, or according to the conditions recommended by the manufacturer. Unless otherwise specified, all parts are weight parts and all percentages are mass percentages. Unless otherwise defined or specified, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. In addition, any method and material similar or equal to the recorded content can be applied to the method of the present invention.

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0039] Example 1

[0040] This embodiment relates to the Bacillus Velezii JSBV55 and applications of the present invention.

[0041] The invention discloses a Bacillus velezensis strain JSBV55, whose deposit number is CGMCCNO.24637.

[0042] The above-mentioned Bacillus velezensis strain JSBV55 was registered and deposited at the General Microbiology Center of China Culture Collection Administration (CGMCC) on April 6, 2022, with the deposit number CGMCC No. 24637. The deposit address is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, Postal Code 100101.

[0043] The morphological characteristics of the Bacillus velezensis strain JSBV55 with the deposit number of CGMCC 24637 are as follows: on the LB solid culture medium, the colonies appear as light yellow opaque colonies with wrinkled surfaces, irregular edges and a slight depression in the middle.

[0044] An application of the Bacillus velezensis strain JSBV55 as described above in preventing and controlling plant diseases, wherein the plants include plants of the lily family or plants of the genus Allium; and the pathogens of the plant diseases are pathogens of the genus Alternaria.

[0045] In some embodiments thereof, the plant includes garlic; the plant disease is garlic purple spot disease; the pathogen of the plant disease is Alternaria alternata, and Alternaria alternata is the pathogen of garlic purple spot disease of the present invention.

[0046] Bacillus velezensis strain JSBV55 can prevent and control garlic purple spot disease through its antagonistic effect on Alternaria, especially Alternaria alternata.

[0047] Example 2

[0048] The present embodiment relates to the biocontrol agent of the present invention, the preparation method of the biocontrol agent, the application of the biocontrol agent, and the method for controlling garlic purple spot disease using the biocontrol agent.

[0049] A biocontrol agent comprises the Bacillus velezensis strain JSBV55 as described in Example 1.

[0050] In some embodiments, the biocontrol agent comprises at least one of the bacterial cells, spores and fermentation broth of the Bacillus velezensis strain JSBV55 as described in Example 1;

[0051] Among them, in the fermentation broth of Bacillus velezensis strain JSBV55, the content of Bacillus velezensis strain JSBV55 is 10 7 ~10 9 cfu / mL.

[0052] In some embodiments, when the biocontrol agent comprises a fermentation broth of Bacillus velezensis strain JSBV55, the content of Bacillus velezensis strain JSBV55 in the fermentation broth is 10 7 cfu / mL.

[0053] In some embodiments, when the biocontrol agent comprises a fermentation broth of Bacillus velezensis strain JSBV55, the content of Bacillus velezensis strain JSBV55 in the fermentation broth is 10 8 cfu / mL.

[0054] In some embodiments, when the biocontrol agent comprises a fermentation broth of Bacillus velezensis strain JSBV55, the content of Bacillus velezensis strain JSBV55 in the fermentation broth is 10 9 cfu / mL.

[0055] A method for preparing the above-mentioned biocontrol agent comprises the following steps:

[0056] Pretreatment: Bacillus velezensis strain JSBV55 was inoculated into LB medium and cultured at a constant temperature for later use;

[0057] Fermentation culture: The pretreated Bacillus velezensis strain JSBV55 is fermented in LB medium to obtain a fermentation broth containing Bacillus velezensis strain JSBV55, which is the biocontrol agent.

[0058] In some embodiments, the method for preparing the above-mentioned biocontrol agent comprises the following steps:

[0059] Pretreatment: Bacillus velezensis strain JSBV55 was inoculated into LB medium, and cultured at 30-37° C. in a dark environment for 24-32 hours before use.

[0060] In some embodiments, the method for preparing the above-mentioned biocontrol agent comprises the following steps:

[0061] Pretreatment: Bacillus velezensis strain JSBV55 was inoculated into LB medium, cultured at 30°C in a dark environment for 24 hours and then used.

[0062] In some embodiments, the method for preparing the above-mentioned biocontrol agent comprises the following steps:

[0063] Fermentation culture: The pretreated Bacillus velezensis strain JSBV55 is inoculated into LB liquid culture medium for fermentation culture at a fermentation temperature of 30-37°C for a fermentation time of 48-72 hours, and the culture is shaken at a rotation speed of 180-220 rpm to obtain a fermentation broth containing the Bacillus velezensis strain JSBV55, which is the biocontrol agent.

[0064] In some embodiments, the method for preparing the above-mentioned biocontrol agent comprises the following steps:

[0065] Fermentation culture: The pretreated Bacillus velezensis strain JSBV55 is inoculated into LB liquid culture medium, and after shaking culture at a rotation speed of 180 rpm and a temperature of 30°C in the dark for 48 hours, a fermentation liquid containing Bacillus velezensis strain JSBV55 is obtained, and the fermentation liquid is the biocontrol agent.

[0066] An application of the above-mentioned biocontrol agent in preventing and controlling plant diseases, wherein the plants include plants of the lily family or plants of the genus Allium; and the pathogens of the plant diseases are pathogens of the genus Alternaria.

[0067] In some embodiments, the plant includes garlic; the plant disease is garlic purple spot disease; and the pathogen of the plant disease is Alternaria alternata.

[0068] A method for preventing and controlling garlic purple spot disease comprises applying the above-mentioned biocontrol agent to the above-ground part of a plant body suffering from garlic purple spot disease or to the growth environment of its root system, with the application amount being 2-4 L / mu.

[0069] Specifically, when applying to the above-ground part of the plant body affected by garlic purple spot disease, the biocontrol agent is sprayed on the leaves; when applying to the root growth environment of the plant affected by garlic purple spot disease, the biocontrol agent is irrigated with roots or applied in furrows.

[0070] In some embodiments, the application rate is 2 L / acre.

[0071] In some embodiments, the application rate is 3 L / acre.

[0072] In some of the embodiments, the application rate is 4 L / acre.

[0073] Example 3

[0074] This embodiment is a variation of the method for preparing the biocontrol agent of Embodiment 2.

[0075] The method for preparing the biocontrol agent described in Example 2 comprises the following steps:

[0076] Pretreatment: Bacillus velezensis strain JSBV55 was inoculated into LB medium and cultured at 33°C in a dark environment for 28 hours before use;

[0077] Fermentation culture: The pretreated Bacillus velezensis strain JSBV55 is inoculated into LB liquid culture medium, and after shaking culture at a rotation speed of 200 rpm and a temperature of 34°C in the dark for 60 hours, a fermentation broth containing Bacillus velezensis strain JSBV55 is obtained, and the fermentation broth is the biocontrol agent.

[0078] Example 4

[0079] This embodiment is a variation of the method for preparing the biocontrol agent of Embodiment 2.

[0080] The method for preparing the biocontrol agent described in Example 2 comprises the following steps:

[0081] Pretreatment: Bacillus velezensis strain JSBV55 was inoculated into LB medium and cultured at 37°C in a dark environment for 32 hours before use;

[0082] Fermentation culture: The pretreated Bacillus velezensis strain JSBV55 is inoculated into LB liquid culture medium, and after shaking culture at a rotation speed of 220 rpm and a temperature of 37°C in the dark for 72 hours, a fermentation broth containing Bacillus velezensis strain JSBV55 is obtained, and the fermentation broth is the biocontrol agent.

[0083] Example 5

[0084] This example is about the isolation and identification of the Bacillus velezensis strain JSBV55 of the present invention, the determination of its antagonistic effect with the garlic purple spot pathogen, and the control effect of the biocontrol agent on garlic purple spot.

[0085] (I) Isolation, screening and identification of strain JSBV55

[0086] (1) Isolation of strain JSBV55

[0087] The separation was performed by plate dilution method. The specific method includes: taking 1g of soil samples collected from the garlic production area of ​​Fengxian County, Jiangsu Province, and placing them in a sterile conical flask containing 27ml of 0.85% sodium chloride solution by mass volume, placing them on a shaker at 150rpm, shaking and incubating at 28℃ for 30min, and then letting them stand for 5min. The suspension at this time is considered to be 10 -1 The diluent was then diluted 10 times with 0.85% sodium chloride solution by mass volume to prepare 10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6 Dilution, pipette 10 -4 , 10 -5 , 10 -6 0.1 ml of three gradient dilutions were spread on LB solid medium, with 3 replicates for each gradient, and cultured at 30°C for about 3 days. Single colonies with different colony morphology were selected and streaked on LB medium for separation and purification. The purified strains were transferred to LB slant medium for culture and stored at 4°C for future use. A total of 122 bacterial strains were isolated.

[0088] The plate confrontation test was used to screen strains that have an inhibitory effect on the growth of Alternaria from the above 122 bacterial strains. The Alternaria of the present invention was isolated from typical plants with purple spot disease of garlic in Fengxian County, Jiangsu Province, and was identified as Alternaria alternata. After the screened strains were verified again by the plate confrontation test, a strain with the best inhibitory effect on Alternaria was obtained, which was named JSBV55.

[0089] (2) Identification of strain JSBV55

[0090] a. Observation of morphological characteristics:

[0091] The strain JSBV55 was streaked onto LB medium and cultured at 30°C for 24 h before observing the morphological characteristics of the strain.

[0092] The results are as follows Figure 1 As shown, on LB solid culture medium, light yellow opaque colonies appeared with wrinkled surface, irregular edges and a slight depression in the middle.

[0093] b. Identification of 16S rRNA molecules of strain JSBV55

[0094] The total genomic DNA of strain JSBV55 was used as a template, and the 16S rRNA of strain JSBV55 was amplified by PCR with primer pair 27-F (5'-AGAGTTTGATCCTGGCTCAG-3') / 1492-R (5'-TACGGCTACCTTGTTACGACTT-3'). After PCR cleaning, recovery, ligation, transformation, identification, and positive clones were sent to Sangon Biotech (Shanghai) Co., Ltd. for sequencing to obtain nucleotide sequence information. The recovery was performed using the DNA gel recovery kit of Axygen, and the ligation was performed using the DNA gel recovery kit of TransGen. -Blunt Cloning Kit, and submit the obtained sequence to the GenBank database for BLAST analysis and comparison.

[0095] The sequencing results were sorted to obtain the 16S rRNA sequence, as shown in the nucleotide and amino acid sequence tables in the manual.

[0096] The total length of 16S rRNA is 1065bp, and its homology with Bacillus velezensis is between 99-100%. Combined with the morphological characteristics of the strain and referring to Bergey's Manual of Systematic Bacteriology, the Bacillus strain JSBV55 was preliminarily identified as Bacillus velezensis.

[0097] (II) Antagonistic effect of strain JSBV55 on garlic purple spot pathogens on plates

[0098] (1) Bacillus velezensis JSBV55 was inoculated into LB medium for activation and cultured in a 30°C constant temperature incubator in the dark for 2 days before use. LB medium consists of 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, and 15 g of agar. The volume was made up to 1000 ml with distilled water and sterilized at 121°C for 20 min.

[0099] (2) The pathogen Alternaria alternata was cultured on PDA solid medium. PDA solid medium was composed of 200 g of potato (peeled), 20 g of glucose, and 15 g of agar. The volume was made up to 1000 ml with distilled water and sterilized at 121°C for 20 min. The pathogen was cultured on PDA solid medium for 7 days.

[0100] (3) Use a sterilized puncher to punch holes along the edge of the prepared pathogen hyphae to obtain a 5 mm diameter bacterial cake, and inoculate the obtained bacterial cake in the center of a new PDA plate. The treatment group was inoculated with a sterile inoculation loop at four directions 25 mm away from the bacterial cake. The treatment was set up with 3 replicates, cultured in the dark at 28°C for 1-4 days, and the colony diameter was measured using the cross method. The antibacterial rate was calculated using the following formula:

[0101] Inhibition rate (%) = (control pathogen colony diameter - treatment pathogen colony diameter) / control pathogen colony diameter × 100%

[0102] Table 1 Antibacterial activity of JSBV55 strain against garlic purple spot pathogens

[0103]

[0104] The results of antibacterial activity are shown in Table 1. Figure 2 As shown, the strain JSBV55 has a significant inhibitory effect on garlic purple spot pathogens. The inhibition rates of each group of tests are: 82.67%, 83.11%, 83.78%, and the average inhibition rate is 83.19%.

[0105] (III) The control effect of the fermentation liquid of strain JSBV55 on garlic purple spot disease

[0106] (1) The strain JSBV55 was inoculated into LB medium and grown in a 30°C constant temperature incubator in the dark for 24 hours before use.

[0107] (2) The reserved JSBV55 was inoculated into 1 L of LB liquid culture medium (the culture medium consisted of 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, and 15 g of agar, which was made up to 1000 ml with distilled water and sterilized at 121°C for 20 min) for fermentation. After shaking culture at a speed of 180 rpm and a temperature of 30°C in the dark for 48 h, the fermentation liquid of JSBV55 was obtained and stored at 4°C for future use.

[0108] (3) Sow the garlic cloves in sterilized soil. After 45 days, transplant the garlic seedlings into pots filled with sterile soil, with 3 plants per pot and 15 plants per treatment, and manage them as usual. After culturing the garlic purple spot pathogen on PDA solid medium for 7 days, scrape the spores and make a spore suspension with sterile water. The spore concentration is 1×10 6 Each pot was inoculated by spraying 50 ml of the solution. One hour after inoculation, the fermentation liquid of JSBV55 (with a bacterial content of 10 8 cfu / mL) were sprayed with 20mL of water. Clean water treatment and blank (not inoculated with garlic purple spot pathogen) were used as controls. The disease was investigated after 14 days and the control effect was calculated.

[0109] Disease grade determination criteria:

[0110] Level 0: no disease;

[0111] Level 1: The lesion area accounts for less than 5% of the entire leaf area;

[0112] Level 3: The lesion area accounts for less than 6% to 10% of the entire leaf area;

[0113] Level 5: The lesion area accounts for less than 11% to 20% of the entire leaf area;

[0114] Level 7: The lesion area accounts for less than 21% to 50% of the entire leaf area;

[0115] Level 9: The lesion area accounts for more than 50% of the total leaf area.

[0116] The calculation method of control effect is as follows:

[0117]

[0118]

[0119] In the formula: CK is the control group, PT is the treatment group.

[0120] Table 2 Determination of potted control effect of strain JSBV55 fermentation liquid on garlic purple spot disease

[0121]

[0122] Note: Data in the same column with the same letters indicate no significant difference at the 0.05 level. Data with different letters indicate significant difference at the 0.05 level.

[0123] The results are shown in Table 2. Figure 3As shown in the figure, 14 days after inoculation with garlic purple spot pathogen, the leaves of garlic plants in the control group showed typical leaf blight symptoms, and some plants fell over, with a disease index of 8.53. Plants treated with biocontrol bacteria JSBV55 showed less disease, with a disease index of only 2.55. Its potted plant protection efficiency reached 70.12%, which was significantly different from that of the water treatment.

[0124] (IV) Field control effect of the fermentation liquid of strain JSBV55 on garlic purple spot disease

[0125] (1) The strain JSBV55 was inoculated into LB medium for growth, and cultured in a 30° C. constant temperature incubator in the dark for 24 hours before use.

[0126] (2) The reserved JSBV55 was inoculated into 1 L of LB liquid culture medium (the culture medium consisted of 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, and 15 g of agar, which was made up to 1000 ml with distilled water and sterilized at 121°C for 20 min) for fermentation. After shaking culture at a speed of 180 rpm and a temperature of 30°C in the dark for 48 h, the fermentation liquid of JSBV55 was obtained and stored at 4°C for future use.

[0127] (3) The field plot test was conducted in a garlic field in Shouxian Town, Fengxian County, Xuzhou City, Jiangsu Province in 2019. A total of 5 treatments were set up, with 4 replications and a plot area of ​​20 square meters. Treatment 1: JSBV55 fermentation liquid (4 L / mu); Treatment 2: JSBV55 fermentation liquid (2 L / mu); Treatment 3: prochloraz manganese salt (active ingredient dosage 20 g / mu); Treatment 4: boscalid (active ingredient dosage 15 g / mu); Treatment 5: clear water control.

[0128] The sampling method for the investigation of disease control effect is carried out according to the following steps. Sampling is carried out at five points on the diagonal of each plot, with 4 plants at each point. All leaves of each plant are investigated, and the grades are determined according to the percentage of the diseased area on each leaf to the total leaf area. The criteria for determining the disease grade and calculating the control effect are the same as (III).

[0129] Table 3 Field control effect of JSBV55 fermentation liquid on garlic purple spot disease

[0130]

[0131] Note: Data in the same column with the same letters indicate no significant difference at the 0.05 level. Data with different letters indicate significant difference at the 0.05 level.

[0132] The results are shown in Table 3. After 14 days of treatment with JSBV55 fermentation liquid (4L / mu), the control effect on garlic purple spot disease reached 61.63%, which is equivalent to the control effect of the chemical agent prochloraz manganese salt. Compared with another chemical agent boscalid, the control effect is significantly different. This shows that the fermentation liquid of strain JSBV55 can be used for field control of garlic purple spot disease.

[0133] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A Bacillus velezensis strain JSBV55, characterized in that The deposit number is CGMCCNO.24637, and the sequence of its 16S rRNA is shown in SEQ ID No:

1.

2. A biocontrol agent, characterized in that: It comprises the Bacillus Velezii strain JSBV55 as described in claim 1.

3. The biocontrol agent according to claim 2, characterized in that Comprising at least one of the bacterial cells, spores and fermentation broth of the Bacillus Velezii strain JSBV55 according to claim 1; Among them, in the fermentation broth of Bacillus velez strain JSBV55, the content of Bacillus velez strain JSBV55 is 10 7 ~10 9 cfu / mL.

4. The biocontrol agent according to claim 3, characterized in that When the biocontrol agent comprises the fermentation broth of Bacillus Velezii strain JSBV55, the content of Bacillus Velezii strain JSBV55 in the fermentation broth is 10 8 cfu / mL.

5. A method for preparing the biocontrol agent according to any one of claims 2 to 4, characterized in that: The following steps are involved: The pretreated Bacillus Velezii strain JSBV55 is fermented and cultured in LB medium to obtain a fermentation liquid containing the Bacillus Velezii strain JSBV55, which is a biocontrol agent.

6. The method according to claim 5, characterized in that The following steps are involved: Pretreatment: inoculate the Velezac bacteria strain JSBV55 in LB medium, and culture at 30-37° C. in a dark environment for 24-32 hours for later use; and / or Fermentation culture: The pretreated Bacillus Velezii strain JSBV55 is inoculated into LB liquid culture medium for fermentation culture at a fermentation temperature of 30-37°C for 48-72 hours, and the culture is shaken at a rotation speed of 180-220 rpm to obtain a fermentation liquid containing the Bacillus Velezii strain JSBV55, which is the biocontrol agent.

7. The method according to claim 6, characterized in that The following steps are involved: Pretreatment: inoculate the Bacillus Velezii strain JSBV55 into LB medium, and culture at 30° C. in a dark environment for 24 hours before use; and / or Fermentation culture: The pretreated Bacillus Velez strain JSBV55 was inoculated into LB liquid culture medium, and after shaking culture at a rotation speed of 180 rpm and a temperature of 30° C. in the dark for 48 hours, a fermentation liquid containing Bacillus Velez strain JSBV55 was obtained, and the fermentation liquid was the biocontrol agent.

8. Use of the Bacillus Velezii strain JSBV55 according to claim 1 or the biocontrol agent according to any one of claims 2 to 4 in preventing and controlling plant diseases, characterized in that: The plant includes a plant of the genus Liliaceae or a plant of the genus Allium; The pathogen of the plant disease is a pathogen of the genus Alternaria.

9. The use according to claim 8, characterized in that: The plants include garlic; The plant disease is garlic purple spot disease; The pathogen of the plant disease is Alternaria alternata.

10. A method for preventing and treating garlic purple spot disease, characterized in that: The biocontrol agent according to any one of claims 2 to 4 is applied to the above-ground part of a plant suffering from garlic purple spot disease or to the growth environment of its root system.

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