CN110257281A - The bacillus cereus of prevention and treatment dothiorella gregaria and biological control agent and method - Google Patents

Abstract

The invention discloses Bacillus cereus, a biological control preparation and a method for preventing and treating poplar canker. The bacterial strain is Bacillus cereus strain SM02, which is isolated from saline-alkaline soil and can be used for biological control preparations. The Bacillus cereus strain It has the characteristics of fast growth, large spore production, strong stress resistance, and rapid and large-scale colonization on the plant surface, so it has good application prospects; The prevention and treatment of poplar canker can effectively promote the growth of poplar. It is a kind of biological control agent with great application prospect. The microbial preparation can be used as biological pesticide or biological fertilizer to prevent and control poplar canker.

Description

Bacillus cereus for preventing and treating poplar canker and biological control preparation and method

technical field

The invention relates to the technical field of biological control of plant diseases, in particular to Bacillus cereus for preventing and treating poplar canker, as well as a biological control preparation and method.

Background technique

Poplar is an important industrial plantation tree species in my country. Due to long-term continuous cropping management, the productivity of forest land has declined generation by generation, and frequent diseases have seriously affected the stability and sustainable development of poplar production. Poplar canker, also known as vesicular canker, is one of the most serious diseases on poplar. The pathogenic fungi include Botryosphaeria , Dothichiza , and Coniothyrium ), Valsa , Coryneum , Nectria , Phoma , etc.; in China, it is mostly reported as Botryosphaeria , This genus of fungi is a class of pathogenic fungi that are widely distributed in the world. Poplar canker mainly occurs in branches, causing local ulcerative necrosis of the cortex. The disease began to onset in April, and the first incidence peak was formed from late May to June. The disease slowed down from July to August, and the second incidence peak appeared in September, and the disease weakened after October. At present, poplar canker occurs in all poplar planting areas in my country and is seriously harmful, which is one of the important factors hindering the development of poplar industry.

For the prevention and treatment of poplar canker, the current production mainly relies on forestry cultivation management measures and chemical pesticides. However, due to the long incubation period, long onset cycle and multi-point damage of the disease, it needs multiple treatments and multiple application of chemical pesticides in a growth cycle to control its damage well. There are problems such as high cost of prevention and control, long time consumption, and environmental pollution. Therefore, seeking new cost-effective, green and environment-friendly control techniques and approaches has become an urgent problem to be solved in the prevention and treatment of poplar canker.

Contents of the invention

The object of the present invention is to provide Bacillus cereus and biological control preparation and method for preventing and treating poplar canker, which has the advantages of fast growth rate, large spore production, strong stress resistance, and rapid large-scale colonization on the plant surface. To solve the problems raised in the background art above.

To achieve the above object, the present invention provides the following technical solutions:

Bacillus cereus for preventing and treating poplar canker, the strain is Bacillus cereus ( Bacillus cereus ) strain SM02;

It is isolated from saline-alkali soil, and its biological characteristics are as follows: on beef extract peptone agar medium or LB (Luria-Bertani) medium, the strain is rod-shaped, with obvious flagella characteristics, and the single colony is round, stained white, Opaque, raised in the center, neat at the edge, and wrinkled in the later stage; cultured on beef extract peptone agar medium at 28°C for two days, microscopic examination showed that the bacterial cells were rod-shaped and able to move; His staining was positive; after spore staining, the spores were oval or columnar.

Further, the culture method of Bacillus cereus bacterial strain SM02 comprises the following steps:

S1: LB medium is used for ordinary culture and preservation, and the formula is 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 15-20 g of agar, 1000 mL of distilled water, and the pH is adjusted to 7.0-7.2;

S2: Laboratory liquid culture uses LB liquid medium, the formula is 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 1000 mL of distilled water, and the pH is adjusted to 7.0-7.2;

S3: solid medium formula: solid material and inorganic salt solution, the ratio of the solid material and inorganic salt is a mass ratio of 98.7:0.3; the mass ratio of the solid material is rice husk: corn flour: soybean meal powder: bran= The composition of 55:25:15:5; the inorganic salt comprises 20% potassium dihydrogen phosphate, 5% magnesium sulfate, 10% ammonium sulfate, and 65% light calcium carbonate by mass percentage;

S4: mass fermentation culture formula: the same as the solid medium formula in S3.

The present invention provides another technical solution:

A biological control agent for preventing and treating poplar canker, including the Bacillus cereus ( B. cereus ) strain SM02.

Further, the preparation method of the biological control agent of preventing and treating poplar canker is as follows:

S1: preparing the seed solution of the Bacillus cereus;

S2: inoculate the seed solution prepared in S1 into a solid medium, and cultivate at a constant temperature of 28-30°C;

S3: Mix the culture cultured in S2 with sterile water at a mass ratio of 1:15, filter, inoculate the filtrate into a large amount of fermentation medium, and place it in a fermentation room with a room temperature of 28-30°C and a relative humidity of 85% or more Carry out fermentation culture.

The present invention also provides a kind of technical scheme as:

The biological control method for preventing and treating poplar canker disease comprises applying the above-mentioned Bacillus cereus ( B. cereus ) strain SM02 or the above-mentioned biological control preparation to poplar plants with canker.

Compared with prior art, the beneficial effect of the present invention is:

1. The Bacillus cereus and the biological control preparation and method for preventing and treating poplar canker provided by the present invention, the Bacillus cereus bacterial strain has fast growth rate, large spore production, strong stress resistance, and can quickly and massively Colonization and other characteristics, so it has a good application prospect.

2. The Bacillus cereus and the biological control preparation and method for preventing and treating poplar canker provided by the present invention, the biological control preparation prepared by the Bacillus cereus can not only effectively prevent and treat poplar canker, but also effectively promote poplar canker. Tree growth is a biological control agent with great application prospects. The microbial agent can be used as biological pesticide or biological fertilizer to prevent and treat poplar canker.

Detailed ways

The embodiments of the present invention will be described in detail below, however, the embodiments of the present invention are not limited thereto. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the embodiment of the present invention: Bacillus cereus for preventing and treating poplar canker, the strain is Bacillus cereus ( Bacillus cereus ) strain SM02, which was isolated from saline-alkali soil and was preserved in China Microorganism Bacteria on March 18, 2019. General Microbiology Center of Species Preservation Committee (CGMCC for short, address: Datun Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences), and the preservation number is CGMCC No. 17337;

Its biological characteristics are: on the beef extract peptone agar medium or LB (Luria-Bertani) medium, the strain is rod-shaped, with obvious flagella characteristics, and the single colony is round, stained white, opaque, with a raised center and neat edges , with folds in the later stage; on beef extract peptone agar medium, cultured at 28°C for two days, microscopic examination, the bacterial cells were rod-shaped and able to move; Escherichia coli was used as a control, and it was positive by Gram staining; After staining, the spores were observed to be oval or columnar.

In the present embodiment, the cultivation method or propagation method of Bacillus cereus bacterial strain SM02 comprises the following steps:

Step 1): LB medium is used for ordinary culture and preservation, and the formula is 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 15-20 g of agar, 1000 mL of distilled water, and the pH is adjusted to 7.0-7.2;

Step 2): LB liquid medium is used for laboratory liquid culture, the formula is tryptone 10 g, yeast extract 5 g, sodium chloride 10 g, distilled water 1000 mL, and the pH is adjusted to 7.0-7.2;

Step 3): solid medium formula: solid material and inorganic salt solution, the ratio of the solid material and inorganic salt is a mass ratio of 98.7:0.3; the mass ratio of the solid material is rice husk: corn flour: soybean meal powder: bran The composition of skin=55:25:15:5; the inorganic salt comprises 20% potassium dihydrogen phosphate, 5% magnesium sulfate, 10% ammonium sulfate, and 65% light calcium carbonate in terms of mass percentage;

Step 4): mass fermentation culture formula: the same as the solid medium formula in step 3).

The present invention provides another biological control agent for preventing and treating poplar canker, including the B. cereus strain SM02;

And, also provide the preparation method of the biological control agent that is used for preventing and treating poplar canker, comprise the following steps:

Step 1): preparing the seed liquid of Bacillus cereus;

Step 2): Inoculate the seed solution prepared in S1 into a solid medium, and culture at a constant temperature of 28-30°C;

Step 3): Mix the culture cultured in S2 with sterile water at a mass ratio of 1:15, filter, inoculate the filtrate into a large amount of fermentation medium, and ferment at room temperature 28-30°C and relative humidity above 85%. fermentation in the chamber.

In a specific embodiment of the present invention, the above-mentioned preparation method comprises the following steps:

Step 1: Transplant the spores of Bacillus cereus into LB liquid medium, shake and culture on a shaker at 28-30°C for 3-5 days to obtain seed liquid;

The second step: inoculate the seed liquid prepared in the first step into the solid medium at a ratio of 10% by mass, and shake and culture at 28-30°C for 3-5 days;

Step 3: Mix the culture cultured in the second step with sterile water at a mass ratio of 1:15, filter, and inoculate the filtrate into the fermentation medium at a room temperature of 28-30°C at a volume ratio of 1:6. Ferment and cultivate in a fermentation room with a relative humidity above 85% for 8-9 days; the active bacteria can reach 3-4 billion/g;

Among them, the LB liquid medium in the first step is formulated as tryptone 10 g, yeast extract 5 g, sodium chloride 10 g, distilled water 1000 mL, and the pH is adjusted to 7.0-7.2.

The solid culture medium in the second step is made up of solid material and inorganic salt, and the mass ratio of described solid material and inorganic salt is 98.7: 0.3; The mass ratio of described solid material is rice husk: corn flour: soybean meal powder: bran =55:25:15:5 composition; the inorganic salt contains 20% potassium dihydrogen phosphate, 5% magnesium sulfate, 10% ammonium sulfate, and 65% light calcium carbonate in terms of mass percentage.

The fermentation medium in the third step is the same as the solid medium in the second step.

The present invention also provides a technical solution: a biological control method for preventing and treating poplar canker, comprising applying the above-mentioned B. cereus strain SM02 or the above-mentioned biological control preparation to poplar plants with canker.

In order to explain the present invention better further, further description is made through the following examples, so that its disclosure is more sufficient:

Embodiment one:

1. Isolation and purification of Bacillus cereus ( B. cereus ) SM02:

The Bacillus cereus ( B. cereus ) SM02 of the present invention is obtained from saline-alkaline soil by using the dilution plate method and the plate streak method to separate and obtain, and the separation method is as follows:

Step 1: Isolation of Bacillus cereus: soil sample collection, saline-alkali soil was collected in Dongying, and mixed; weighed 1 g of soil in 100 mL of sterile water, placed in a shaker at 30°C at 150 rpm for 10 min, Then place it in a water bath at 60°C and incubate for 30 minutes, take 100 μL of 10 ^-2 , 10 ^-3 , and 10 ^-4 dilutions and spread them on the LB medium plate, and apply three parallels for each gradient, and culture at 30°C for 2 days Pick different forms of microbial colonies on the LB medium and streak them on the LB medium plate, observe the growth of the colonies regularly; then use the plate streaking method to purify the Bacillus cereus strains and store them under serial numbers.

Step 2: Screening of highly effective antagonists against Bacillus cereus against poplar canker:

1) Preliminary screening: Prepare PDA (Potato Dextrose Agar) plates using the confrontation culture method, use a puncher to take fungus cakes with a diameter of 5mm from the edge of Bacillus cereus and poplar canker, and transplant them on the opposite sides of the plate respectively In the center, cultivate at a constant temperature of 30°C, and observe the inhibitory effect of Bacillus cereus on pathogenic bacteria day by day;

2) Re-screening: Re-screen the screened Bacillus cereus strains with high-efficiency antagonistic activity, mainly through temperature resistance, acid and alkali resistance, and drug resistance tests, and screen out Bacillus strains with better tolerance. Carry out potted control experiments and field trials.

A strain of Bacillus cereus ( B. cereus ) SM02 that can effectively prevent and treat poplar canker was obtained through a large number of screening work; experiments have proved that the Bacillus cereus strain has a very high control effect in the prevention and treatment of poplar canker , so that the poplar grows well. Therefore, the bacillus cereus of the present invention is a new strain of the bacillus cereus with broad application prospects, and can be used to prepare biological control agents for preventing and treating poplar canker.

2. Strain identification:

(1) Microbiological characteristics: on the beef extract peptone agar medium or LB medium, the strain is rod-shaped, with obvious flagella characteristics, and the single colony is round, stained white, opaque, with a raised center, neat edges, and folds in the later stage ; On the beef extract peptone agar medium, cultured at 28°C for two days, microscopic examination showed that the bacterial cells were rod-shaped and could move. Positive by Gram staining (with Escherichia coli as the control); after spore staining, it is observed that the spores are oval, mesozoic or nearly mesozoic, and the cysts are not enlarged;

(2) Molecular biological characteristics: The results of the 16s rRNA gene sequence determination of the strain are as follows (SEQ-1):

CTTCTATACATGCAGTAGAGCGGACAGATGGGAGCTTGCTCCCTGATGTTAGCGGCGGACGGGTGAGTAACACGTGGGTAACCTGCCTGTAAGACTGGGATAACTCCGGGAAACCGGGGCTAATACCGGATGCTTGTTTGAACCGCATGGTTCAAACATAAAAGGTGGCTTCGGCTACCACTTACAGATGGACCCGCGGCGCATTAGCTAGTTGGTGAGGTAACGGCTCACCAAGGCAACGATGCGTAGCCGACCTGAGAGGGTGATCGGCCACACTGGGACTGAGACACGGCCCAGACTCCTACGGGAGGCAGCAGTAGGGAATCTTCCGCAATGGACGAAAGTCTGACGGAGCAACGCCGCGTGAGTGATGAAGGTTTTCGGATCGTAAAGCTCTGTTGTTAGGGAAGAACAAGTACCGTTCGAATAGGGCGGTACCTTGACGGTACCTAACCAGAAAGCCACGGCTAACTACGTGCCAGCAGCCGCGGTAATACGTAGGTGGCAAGCGTTGTCCGGAATTATTGGGCGTAAAGGGCTCGCAGGCGGTTTCTTAAGTCTGATGTGAAAGCCCCCGGCTCAACCGGGGAGGGTCATTGGAAACTGGGGAACTTGAGTGCAGAAGAGGAGAGTGGAATTCCACGTGTAGCGGTGAAATGCGTAGAGATGTGGAGGAACACCAGTGGCGAAGGCGACTCTCTGGTCTGTAACTGACGCTGAGGAGCGAAAGCGTGGGGAGCGAACAGGATTAGATACCCTGGTAGTCCACGCCGTAAACGATGAGTGCTAAGTGTTAGGGGGTTTCCGCCCCTTAGTGCTGCAGCTAACGCATTAAGCACTCCGCCTGGGGAGTACGGTCGCAAGACTGAAACTCAAAGGAATTGACGGGGGCCCGCACAAGCGGTGGAGCATGTGGTTTAATTCGAAGCAACGCGAAGAACCTTACCAGGTCTTGACATCCTCTGACAATCCTAGAGATAGGACGTCCCCTTCGGGGGCA GAGTGACAGGTGGTGCATGGTTGTCGTCAGCTCGTGTCGTGAGATGTTGGGTTAAGTCCCGCAACGAGCGCAACCCTTGATCTTAGTTGCCAGCATTCAGTTGGGCACTCTAAGGTGACTGCCGGTGACAAACCGGAGGAAGGTGGGGATGACGTCAAATCATCATGCCCCTTATGACCTGGGCTACACACGTGCTACAATGGACAGAACAAAGGGCAGCGAAACCGCGAGGTTAAGCCAATCCCACAAATCTGTTCTCAGTTCGGATCGCAGTCTGCAACTCGACTGCGTGAAGCTGGAATCGCTAGTAATCGCGGATCAGCATGCCGCGGTGAATACGTTCCCGGGCCTTGTACACACCGCCCGTCACACCACGAGAGTTTGTAACACCCGAAGTCGGTGAGGTAACCTTTAGGAGCCAGCCGACGAAGGGTGAT

(3) Cell morphology and physical and chemical experiment results:

Table 1 Cell morphology and physicochemical results of Bacillus cereus ( B. cereus ) SM02

experimental project result experimental project result a positive Carbohydrate Acid + cell shape Rod glucose + Cell diameter > 1 μm - xylose + Sporulation + L-arabinose + Spore expansion - Mannitol - spore round - lactose - parasporal crystals - Fermenting glucose to produce gas + Catalase + Utilize citrate + Oxidase + Growth at 50°C + anaerobic growth - Growth at pH 5.7 + VP test + 7% NaCl growth + VP﹤pH 6 + starch hydrolysis + VP > pH 7 - break down casein + Nitrate reduction + hydrolyzed gelatin +

Embodiment two:

1. Fermentation process of Bacillus cereus:

The formula of LB liquid medium is 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 1000 mL of distilled water, and the pH is adjusted to 7.0-7.2;

The solid material is rice husk: corn flour: soybean meal flour: bran=55:25:15:5; the inorganic salt solution is 20% potassium dihydrogen phosphate, 5% magnesium sulfate, 10% ammonium sulfate, 65% light calcium carbonate ; The solid-liquid ratio is 98.7:0.3 (mass ratio).

Mass solid fermentation process of B. cereus strain SM02:

Step 1: culture of strains in seed solution: pick a small amount of bacteria from Bacillus cereus strain ( B. cereus ) SM02 from the slant of the test tube, transfer them to LB liquid medium, and cultivate them on a shaker at 30°C for 3-5 days. This is the seed liquid;

Step 2: Cultivation of solid production strains: Inoculate the seed liquid into solid medium (500 mL Erlenmeyer flask) at a ratio of 10%, and culture at a constant temperature of 30°C for 3-5 days, shaking several times in the middle;

The third step: a large amount of solid fermentation: Dilute the culture cultured in the second step with sterile water at a ratio of 1:15, and filter it with sterilized gauze to remove the coarse residue, which is the production bacterial liquid, and the inoculation ratio is 1: 6 Inoculate in a large amount of fermentation medium, put the inoculated raw materials in a fermentation room (30°C and relative humidity above 85%) and ferment for 8-9 days to obtain the original powder of Bacillus, and the active bacteria can reach 4 billion/g .

The test results showed that: Bacillus cereus ( B. cereus ) strain SM02 fermentation liquid was effective in controlling poplar canker, the control effect reached 67.81%, and the poplar grew well without phytotoxicity.

Embodiment three:

In order to clarify the control effect of Bacillus cereus ( B. cereus ) strain SM02 fermentation liquid on poplar canker, and to provide a basis for its popularization and application, the present invention was tested in Xiajin County, Dezhou City from April to October 2018, and now Report the test results as follows:

1. Test materials and methods

1.1 Test agent: Bacillus cereus ( B. cereus ) strain SM02 fermented liquid (500 million/ml bacterial liquid) produced according to the fermentation method of Example 1 of the present invention; 70% thiophanate-methyl wettable powder (Shandong Le Bang Chemical Co., Ltd., commercially available).

1.2 Test material and control object: The test material is poplar, and the control object is poplar canker.

1.3 The situation of the test site: The test site is located in Xiajin County, Dezhou City. The test soil type is cinnamon soil, the organic matter content is 0.53%, and the pH value is 7.8. The management measures of all test plots are the same.

1.4 Experimental design and arrangement: There are 3 treatments in this experiment, namely Bacillus cereus ( B. cereus ) strain SM02 fermentation broth 10 times liquid, 70% thiophanate-methyl wettable powder 100 times liquid, water without application As a control, each treatment was repeated 4 times, and 60 plants were sprayed on April 15, May 20, and August 22, 2018. The spraying equipment was Gongnong-16 sprayer.

1.5 Test investigation and calculation method

1.5.1 Meteorological conditions: The day of the first spraying (April 15) was sunny, the wind force was level 3, the highest temperature was 19°C, the lowest temperature was 8°C, and the relative humidity was 61%. The second spraying (May 20), the day was cloudy, the wind force was 3, the maximum temperature was 26°C, the minimum temperature was 16°C, and the relative humidity was 64%; the third spraying (August 22), the same day Cloudy, wind force 3, the highest temperature is 28 ℃, the lowest temperature is 20 ℃, and the relative humidity is 70%.

1.5.2 Drug efficacy and safety investigation

Drug efficacy investigation: 14 days after the last spraying, 50 plants were investigated for each treatment, the lower bark of the main trunk was investigated, the incidence rate was investigated, the disease progression was recorded and the disease index was calculated.

Safety investigation: Observe the safety of poplar trees 7 days and 14 days after the first application of pesticides. If any phytotoxicity occurs, describe the symptoms of phytotoxicity in detail and determine the degree of phytotoxicity according to the classification standard of phytotoxicity degree.

Grading method of poplar canker (in single plant):

Level 0: disease-free class.

Grade 1: The lesion area accounts for less than 1/4 of the entire trunk area.

Grade 2: The lesion area accounts for 1/4~2/4 of the entire trunk area.

Grade 3: The lesion area accounts for 2/4~3/4 of the entire trunk area.

Grade 4: The lesion area accounts for more than 3/4 of the entire trunk area.

1.5.3 Calculation method of efficacy

The control effect is calculated according to formula (1) and (2):

(1)

(2)

In the formula: CK ₀ - disease index in the blank control area before application;

CK ₁ - disease index of the blank control area after application;

PT _0—— the disease index before drug treatment and before application;

PT _1——— the disease index after drug treatment.

1.5.4 Direct impact on poplar

Observe whether the pesticide has harm to the poplar, and record the type and degree of the harm. In addition, record the impact on the growth of the poplar, and record the harm in the following way:

(a) If phytotoxicity can be measured or calculated, it should be expressed in absolute value, eg plant height.

(b) In other cases, the degree and frequency of injury may be estimated in the following two ways:

① According to the phytotoxicity classification method, record the phytotoxicity degree of each plot, expressed in -, +, ++, +++, +++++.

Phytotoxicity classification method:

—: no harm;

+: Slight phytotoxicity, does not affect the growth of trees;

++: Moderate phytotoxicity, recoverable, and will not cause tree yield reduction;

＋＋＋: Moderate phytotoxicity, which affects the normal growth of trees and causes a certain degree of loss in tree yield and quality;

＋＋＋＋: Severe phytotoxicity, hindered tree growth, serious loss of yield and quality.

② Compare the pesticide treatment area with the blank control area to evaluate the percentage of phytotoxicity. At the same time, accurately describe the symptoms of phytotoxicity (dwarfing, chlorosis, deformity, etc.).

2 results

2.1 The control effect of test agents on poplar canker

The results in Table 3 show that both Bacillus cereus ( B. cereus ) strain SM02 fermentation broth and 70% thiophanate-methyl wettable powder have good control effects on poplar canker, and the control effect of the former reaches 60%. above.

Judging from the disease index of poplar canker field test (Table 3), 14 days after the last application, the control effect of B. cereus SM02 was 67.81%, which was significantly higher than 70% of methylthiobacterium The control effect of Ling WP was 49.51%.

Table 2 The status of poplar canker disease before three pesticide treatments

Table 3 Control effect of three pesticide treatments on poplar canker

2.2 Safety investigation of poplar: After spraying for 7 days and 14 days, compared with the control area, the poplars in the treatment areas of each chemical agent grew normally, and no phytotoxicity occurred, indicating that the Bacillus cereus bacterial solution was safe to poplars.

In summary: (1) From the perspective of disease index and control effect, Bacillus cereus ( B. cereus ) strain SM02 (preservation number CGMCC No. 17338) has a good control effect on poplar canker. The control effect reached over 60% in the last 14 days; (2) Judging from the growth of poplar, Bacillus cereus ( B. cereus ) strain SM02 had obvious growth-promoting effect on poplar, and it was safe and reliable without phytotoxicity.

In summary: the Bacillus cereus and biological control preparation and method for preventing and treating poplar canker provided by the present invention, its Bacillus cereus strain has fast growth rate, large spore production, strong stress resistance, and can be used on the plant surface It can quickly colonize a large number of characteristics, so it has a good application prospect; in addition, the biological control preparation prepared by the Bacillus cereus can not only effectively prevent and treat poplar canker, but also effectively promote the growth of poplar. A biological control preparation with great application prospects, the microbial preparation can be used as biological pesticide or biological fertilizer to prevent and treat poplar canker.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (5)

1. Bacillus cereus for preventing and treating poplar canker, characterized in that the strain is Bacillus cereus ( Bacillus cereus ) strain SM02; It is isolated from saline-alkali soil, and its biological characteristics are as follows: on beef extract peptone agar medium or LB (Luria-Bertani) medium, the strain is rod-shaped, with obvious flagella characteristics, and the single colony is round, stained white, Opaque, raised in the center, neat at the edge, and wrinkled in the later stage; cultured on beef extract peptone agar medium at 28°C for two days, microscopic examination showed that the bacterial cells were rod-shaped and able to move; His staining was positive; after spore staining, the spores were oval or columnar. 2. the culture method of bacillus cereus bacterial strain SM02 according to claim 1, is characterized in that, comprises the following steps: S1: LB medium is used for ordinary culture and preservation, and the formula is 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 15-20 g of agar, 1000 mL of distilled water, and the pH is adjusted to 7.0-7.2; S2: Laboratory liquid culture uses LB liquid medium, the formula is 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 1000 mL of distilled water, and the pH is adjusted to 7.0-7.2; S3: solid medium formula: solid material and inorganic salt solution, the ratio of the solid material and inorganic salt is a mass ratio of 98.7:0.3; the mass ratio of the solid material is rice husk: corn flour: soybean meal powder: bran= The composition of 55:25:15:5; the inorganic salt comprises 20% potassium dihydrogen phosphate, 5% magnesium sulfate, 10% ammonium sulfate, and 65% light calcium carbonate in terms of mass percentage; S4: mass fermentation culture formula: the same as the solid medium formula in S3. 3. A biological control agent for preventing and treating poplar canker, characterized in that it comprises the B. cereus strain SM02. 4. the biological control preparation of preventing and treating poplar canker according to claim 3, is characterized in that, preparation method is as follows: S1: preparing the seed solution of the Bacillus cereus; S2: inoculate the seed solution prepared in S1 into a solid medium, and cultivate at a constant temperature of 28-30°C; S3: Mix the culture cultured in S2 with sterile water at a mass ratio of 1:15, filter, inoculate the filtrate into a large amount of fermentation medium, and place it in a fermentation room with a room temperature of 28-30°C and a relative humidity of 85% or more Carry out fermentation culture. 5. A biological control method for preventing and treating poplar canker, characterized in that it comprises applying the above-mentioned B. cereus strain SM02 or the above-mentioned biological control agent to poplar plants with canker.