Bacillus velezensis SFJ-27682 and application thereof

Abstract

The invention belongs to the technical field of plant disease control, and particularly relates to bacillus velezensis and application thereof. The bacillus velezensis strain is separated and screened from rhizosphere soil of wheat in a main wheat area in Hebei Province, the growth characteristics and physiological and biochemical characteristics of the bacterial colony are identified, then 16S rDNA sequencing is carried out, Blast homology comparison is carried out in a GenBank database, the bacterial strain is identified to be bacillus velezensis through the analysis, and the bacillus velezensis strain is identified to be bacillus velezensis. The fungicide containing the bacillus velezensis has a good prevention and treatment effect on wheat stem rot through seed coating.

Description

Technical Field

[0001] The invention belongs to the technical field of plant disease prevention and control, and specifically relates to Bacillus velez and application thereof. Background Art

[0002] Wheat crown rot (Fusarium Crown Rot) is a soil-borne disease caused by a variety of Fusarium species. The disease occurs in countries such as Australia, the United States, and Canada and causes serious damage. In normal years, it can cause an average wheat yield loss of about 9.5%, while in epidemic years it can reach 35%. The main symptoms of wheat crown rot are browning and necrosis at the base of the wheat stem, which can lead to withered and white ears in severe cases. The withered and white ear rate in some plots can reach 20% to 50%. In recent years, the disease has developed rapidly in major wheat-growing areas in my country. It is reported that in parts of Henan and Hebei provinces, the rate of wheat crown rot diseased fields is as high as 65.1% and 81.4%, respectively, and the rate of white ears in severe plots is as high as 31.5% and 50.0%, which has seriously threatened my country's wheat production and has a tendency to worsen year by year.

[0003] At present, there is a lack of ideal disease-resistant varieties and efficient prevention and control strategies for wheat stem rot, and there is no registered fungicide for the prevention and control of this disease. Only seed coating agents registered for the prevention and control of other soil-borne diseases are used to prevent and control this disease. However, these agents are highly effective in the seedling stage, but the prevention effect decreases during the filling stage. In addition, excessive use of agents such as tebuconazole can easily affect wheat germination and growth. The large-scale use of chemical agents will also pose a great threat to the ecological environment and food safety. Therefore, finding an environmentally friendly and effective prevention and control measure for wheat stem rot is an urgent problem to be solved today.

[0004] Biocontrol microorganisms themselves or their metabolites have a variety of biological activities, which can be used to inhibit bacteria, promote growth, and improve plant resistance, thereby controlling the occurrence of diseases. Microbial live pesticides and microbial metabolite pesticides can be produced through microbial fermentation, which can achieve the green economic sustainable development of agriculture. Summary of the invention

[0005] The object of the present invention is to provide a Bacillus velezensis SFJ-27682.

[0006] Another object of the present invention is to provide the application of the above-mentioned Bacillus Velezii strain.

[0007] The Bacillus velezensis SFJ-27682 of the present invention was deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration on September 19, 2024. The specific deposit address is: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, and the deposit number is CGMCC No: 32000.

[0008] The invention separates and obtains a strain of Bacillus velezensis from the rhizosphere soil of wheat in the main wheat-growing areas of Hebei Province and preserves the strain, which has a significant inhibitory effect on pseudo-graminearum Fusarium and has a good control effect on wheat stem base rot.

[0009] Based on the above-mentioned effects of the Bacillus Velez strain, the present invention proposes the application of the strain, especially in the prevention and treatment of wheat base stem rot. For example, according to factors such as plant growth status or soil conditions, the strain is evenly sprayed on the soil surface and covered with a thin layer of soil to prevent wheat base stem rot. Alternatively, the strain is prepared into a bacterial agent and used.

[0010] The above-mentioned bacterial agent contains the Velezac bacteria strain, a suspension seed coating agent containing its fermentation product, and the like.

[0011] The invention provides a composite biocontrol agent, which comprises the fermentation liquid of the Velezac bacteria strain, a dispersant, a synergist, a thickener and a defoamer.

[0012] Preferably, the biocontrol agent comprises a fermentation broth of Bacillus Velezii (Bacillus Velezii concentration 10 11 cfu / mL), dispersant 5-10%, synergist 1.2-2.5%, thickener 1-3%, defoamer 0.5-1.5%.

[0013] Preferably, according to the mass ratio of the fermentation broth of the Bacillus Velezii strain, the biocontrol agent contains 5% of dispersant, 1.5% of synergist, 2% of thickener and 1% of defoamer.

[0014] Preferably, the dispersant is a mixture of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80. More preferably, the mass ratio of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80 in the dispersant is 1:1-3:2-5, wherein the mass ratio of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80 can be 1:1:3.

[0015] More preferably, the synergist is a nitrogen synergist, the thickener is xanthan gum, and the defoamer is a silicone defoamer.

[0016] Preferably, the present invention also provides a composite biocontrol agent, which also contains the above-mentioned agent and 6% oligosaccharide·tetherin.

[0017] The commercial product of 6% oligosaccharide and chain protein wettable powder is Ata Ling, which is an antiviral protein pesticide with a wide range of applications, including various viral diseases in crops such as corn, rice, wheat, vegetables, fruits, tobacco, fruit trees, flowers, and medicinal materials. The application method is to add 6% oligosaccharide and chain protein wettable powder to water (generally 15-20g of Ata Ling to 15kg of water), spray on the leaves, and spray 2-3 times in a row.

[0018] Preferably, the mass ratio of the bacterial agent to 6% oligosaccharide·chain protein is 1-10:1-10, and more preferably, the mass ratio of the bacterial agent to 6% oligosaccharide·chain protein is 1:1.

[0019] The present invention also creatively discovered that the above-mentioned Bacillus Velez subtilis agent can be used in combination with 6% oligosaccharide·catenin for preventing and controlling wheat stem base rot, and has a more significantly excellent effect than a single Bacillus Velez subtilis agent or 6% oligosaccharide·catenin wettable powder, indicating that the Bacillus Velez subtilis agent and 6% oligosaccharide·catenin have a synergistic effect in the above-mentioned effects, especially when the mass ratio of the Bacillus Velez subtilis agent to the 6% oligosaccharide·catenin is 1:1, the effect is best.

[0020] The present invention also provides a culture medium for the above-mentioned Bacillus Velez, which comprises 1-5% sucrose, 1-5% soybean powder, 0.5-2% NaCl, 0.1-0.5% CaCO3, 0.01-0.05% KH2PO4 and 0.01-0.05% MgSO4·7H2O.

[0021] Preferably, the culture medium comprises 3% sucrose, 1% soybean powder, 1% NaCl, 0.2% CaCO3, 0.02% KH2PO4 and 0.03% MgSO4·7H2O.

[0022] Beneficial effects of the present invention:

[0023] The Bacillus velezensis strain of the invention is separated and screened from wheat rhizosphere soil in the main wheat-growing areas of Hebei Province, and its colony growth characteristics and physiological and biochemical properties are identified, followed by 16S rDNA sequencing and Blast homology comparison in the GenBank database. Through the above analysis, the strain is identified as Bacillus velezensis.

[0024] The Bacillus velezensis strain SFJ-27682 of the invention has an obvious inhibitory effect on Fusarium graminearum, and the prevention effect of the strain on wheat stem base rot can reach 41.47%.

[0025] The fermentation liquid of Bacillus Velez SFJ-27682 is mixed with dispersants, thickeners, synergists and other ingredients in a specific proportion to make a bacterial agent. When used for wheat seed dressing, it can form a complete and uniform coating on the seeds and exert a sustained and long-lasting protective effect. The prevention effect against wheat stem base rot can be increased to 64.43%.

[0026] The present invention further compounds the Bacillus Velez SFJ-27682 microbial agent with 6% oligosaccharide·chain protein to form a composite microbial agent, and when combined at a ratio of 1:1, an obvious synergistic effect is obtained. The composite microbial agent is used for seed dressing of wheat, and the prevention effect of wheat stem base rot is further improved to 83.54%, and the disease index and white ear rate in the field adult stage are 62.25% and 65.32% respectively. At the same time, the composite microbial agent can increase the emergence rate of wheat, promote wheat growth, and significantly increase wheat yield. DETAILED DESCRIPTION

[0027] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0028] The Bacillus velezensis SFJ-27682 of the present invention was deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration on September 19, 2024. The specific deposit address is: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, and the deposit number is CGMCC No: 32000.

[0029] Example 1 Screening and Identification of Bacillus Velezii SFJ-27682

[0030] 1.1 Screening of Bacillus velez SFJ-27682

[0031] The wheat rhizosphere soil from the main wheat-growing areas of Hebei Province was collected, and then ground with sterile saline and graded diluted (10 1 ~10 5times), spread on beef extract peptone medium (NA), invert and culture in a 37℃ incubator for 2-3 days, and use the last rinse water as a control. Pick different single colonies according to the morphology, color, size, etc. of the colonies grown on the plate, and then perform streaking purification until a single colony is obtained, and store the slant at 4℃ for later use.

[0032] Each strain was screened by the confrontation culture method. A 5 mm diameter Fusarium graminearum cake was placed in the center of the PDA plate. The bacteria to be tested were dipped in a bacterial loop and streaked in the center of the plate. Then, the isolated bacteria were inoculated at an equal distance from the cross 2.5 cm from the center of the plate. At the same time, the control (CK) without inoculation of isolated bacteria was used. The experiment was repeated 3 times for each treatment and cultured at a temperature of 25°C. When the control group (CK) was full of all the vessels, the size of the inhibition zone was recorded. The five strains with the largest inhibition zone (SFJ-27634, SFJ-27682, SFJ-27684, SFJ-27698, and SFJ-28725) were selected for greenhouse potted bioassay. Each strain was cultured in an LB medium in a shaking incubator at 37°C and 180 r / min for 2 days, and the bacterial solution was concentrated by centrifugation until the number of viable bacteria was 10 10 CFU / mL bacterial solution, the bacterial solution and wheat seeds (variety Shixin 828) were mixed at room temperature at 300g / 100kg seeds, the wheat seeds were taken out after mixing, and dried at 35℃ for 24h to obtain coated wheat seeds. At the same time, a blank control group (no seed dressing treatment) was added, and the coated seeds were sown in nutrient pots (diameter 15cm×15cm) and inoculated with 1×10 5 The disease was induced in the soil with spores / g of soil. After culturing in a greenhouse at 22℃ and 12h light-dark alternation for 30 days, the disease stage of wheat was investigated, the disease index and the greenhouse control effect were calculated.

[0033] The greenhouse pot survey adopted a modified Bovill grading method: wheat stem base rot was graded based on the length of browning of the stem below the first leaf sheath.

[0034] Level 0: no browning symptoms;

[0035] Level 1: The length of browning below the first leaf sheath accounts for less than 25% of the stem;

[0036] Level 2: The length of browning below the first leaf sheath accounts for 25-50% of the stem;

[0037] Level 3: The length of browning below the first leaf sheath accounts for 50-75% of the stem, and the brown color deepens;

[0038] Level 4: The brown length below the first leaf sheath accounts for more than 75% of the stem, or the entire plant turns brown and dies.

[0039] Disease index = ∑ (number of diseased plants × representative values ​​at each level) / (total number of plants surveyed × highest representative value) × 100;

[0040] Control effect (%) = (control disease index - treatment disease index) / control disease index × 100.

[0041] Table 1 The inhibitory zone of biocontrol bacteria against wheat stem rot and the control effect of greenhouse potted plants

[0042]

[0043] As shown in Table 1, the strain SFJ-27682 has the best protective effect. Therefore, SFJ-27682 with the highest protective effect was selected for identification and the next step of testing.

[0044] 1.2 Identification of Bacillus velez SFJ-27682

[0045] 1. Morphological identification

[0046] Colony morphology: The antagonistic strain was inoculated on beef extract peptone medium (NA) by streaking method and cultured at 37°C for 1-2 days to observe its colony morphology. The bacterial morphology was stained by single staining and Gram staining and observed under an optical microscope.

[0047] The results showed that the colonies formed by strain SFJ-27682 on beef extract peptone medium were thin, oval or nearly circular, milky white, with wrinkled surface, raised in the middle, neat edges, opaque, rod-shaped cells, Gram-positive, and spore-forming bacteria.

[0048] 2. Physiological and biochemical identification

[0049] Physiological and biochemical tests of endogenous antagonistic bacteria were performed with reference to the Bergey's Manual of Bacterial Identification and the Manual of Identification of Common Bacterial Systems.

[0050] The results showed that the catalase reaction was positive, the starch hydrolysis reaction was positive, the glucose acid production test was negative, the glucose gas production test was negative, the methyl red assay was negative, the acetylmethylcarbinol test (VP) was positive, the gelatin liquefaction reaction was positive, the nitrate reduction reaction was positive, the citrate utilization assay was positive, the indole test was negative, the phenylalanine dehydrogenase test was negative, and the urea hydrolysis test was positive.

[0051] The results of physiological and biochemical reactions of strain SFJ-27682 were compared with those of Bacillus Velezii described in the literature, and it was found that the physiological and biochemical test results of this strain were basically consistent with those of Bacillus Velezii.

[0052] 3.16S rDNA sequence analysis

[0053] The genomic DNA was extracted using Shanghai Biotech SK1201-UNIQ-10 column bacterial genomic DNA extraction kit. The 16S rDNA universal primers 7F (5'-CAGAGTTTGATCCTGGCT-3') and 1540R (5'-AGGAG GTGATCCAGCCGCA-3') were used to amplify the bacterial 16S rDNA fragments in the total DNA of the strains. The reaction conditions were as follows:

[0054] Pre-denaturation 98℃, 5min,

[0055] Cycle 95℃35s, 55℃35s, 72℃90s, 35 cycles,

[0056] Extension for 8 minutes.

[0057] PCR system establishment (50 μL):

[0058]

[0059]

[0060] The amplified product was recovered using a UNIQ-10 column DNA gel recovery kit (Shanghai Bioengineering Co., Ltd.) and sequenced by Shanghai Bioengineering Co., Ltd. The sequence was submitted to Genbank and compared through Blast. It was found that the sequence had a 100% similarity with several reported strains of Bacillus velezensis. Based on the results of morphological characteristics and physiological and biochemical reactions, the strain SFJ-27682 was determined to be Bacillus velezensis.

[0061] The strain was deposited in the General Microbiology Center of China Microbiological Culture Collection Administration on September 19, 2024. The specific address is: No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, and the deposit number is CGMCC No: 32000.

[0062] Example 2 Optimization of the fermentation medium of Bacillus Velez SFJ-27682

[0063] The fermentation medium of the selected biocontrol bacteria strain SFJ-27682 with the highest field control effect was optimized. Corn flour, sucrose, glucose, and soluble starch were used as carbon sources, soybean flour, sodium nitrate, ammonium nitrate, and ammonium sulfate were used as nitrogen sources, and a certain amount of trace elements, NaCl, KH2PO4, MgSO4·7H20, and CaCO3 were added. Through single factor determination experiments, the effects of the four carbon sources and four nitrogen sources on the reproduction and growth of the strain SFJ-27682 were clarified.

[0064] The results showed that among the four carbon sources, sucrose was the best carbon source, with the highest concentration of 1.47×10 10 cfu / ml, followed by glucose, soluble starch, and corn flour. Among the four nitrogen sources, soybean flour was the best nitrogen source, with the highest concentration of 1.22×10 10 cfu / mL, followed by ammonium sulfate, sodium nitrate and ammonium nitrate.

[0065] Table 2 Single factor determination of carbon and nitrogen sources in biocontrol bacteria fermentation

[0066]

[0067]

[0068] On the basis of the single factor experiment, an L9(34) orthogonal experiment was carried out under the condition that the two trace elements KH2PO4 and MgSO4·7H2O remained unchanged. The concentrations of four factors, namely, carbon source sucrose (A), nitrogen source soybean meal (B), and two inorganic salts with higher dosages, NaCl (C) and CaCO3 (D), were screened to establish the optimal culture medium for strain fermentation.

[0069] Table 3 Orthogonal test for screening the amount of carbon and nitrogen sources and inorganic salts

[0070]

[0071] The results of orthogonal test showed that the optimal culture medium formula for each factor was A3B1C3D2, with a concentration of 6.43×10 11 cfu / mL, which is more than 30 times higher than the lowest fermentation medium concentration. That is, the optimal fermentation medium for SFJ-27682 is 3% sucrose, 1% soybean powder, 1% NaCl, 0.2% CaCO3, 0.02% KH2PO4 and 0.03% MgSO4·7H2O.

[0072] The above culture medium was used to culture Bacillus Velez subsp. SFJ-27682 in a shaking incubator at 37° C. and 180 rpm for 30 days to obtain a fermentation liquid of Bacillus Velez subsp. SFJ-27682.

[0073] Example 3 Preparation of biocontrol agents

[0074] Example 3: The fermentation broth of SFJ-27682 was obtained according to the method of Example 2, and the fermentation broth was diluted with sterile water to a concentration of 10 11cfu / mL. According to the mass ratio of the fermentation liquid, 8% dispersant, 1.5% nitrogen enhancer, 2.0% xanthan gum (thickener), and 1.0% organosilicon defoamer were added to prepare the Velez Bacillus SFJ-27682 inoculum; the dispersant was a mixture of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80 in a mass ratio of 1:1:3.

[0075] Comparative Example 1: The fermentation liquid of SFJ-27682 was obtained according to the method of Example 2, and the sterile water was diluted to a concentration of 10 11 cfu / mL. According to the mass ratio with the fermentation liquid, 5% dispersant, 1.5% nitrogen enhancer, 2.0% xanthan gum (thickener), and 1.0% organosilicon defoamer were added; the dispersant was a mixture of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80 in a mass ratio of 1:1:3.

[0076] Comparative Example 2: The fermentation liquid of SFJ-27682 was obtained according to the method of Example 2, and the fermentation liquid was diluted with sterile water to a concentration of 10 11 cfu / mL. According to the mass ratio with the fermentation liquid, 8% dispersant, 1.5% nitrogen enhancer, 2.0% xanthan gum (thickener), and 1.0% organosilicon defoamer were added; the dispersant was a mixture of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80 in a mass ratio of 1:1:1.

[0077] Comparative Example 3: The fermentation broth of SFJ-27682 was obtained according to the method of Example 2, and the fermentation broth was diluted with sterile water to a concentration of 10 11 cfu / mL. According to the mass ratio with the fermentation liquid, 8% dispersant, 1.5% nitrogen enhancer, 1.0% xanthan gum (thickener), and 1.0% organosilicon defoamer were added; the dispersant was a mixture of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether, and Tween 80 in a mass ratio of 1:1:3.

[0078] The control effects of the biocontrol agents prepared in Example 3 and Comparative Examples 1, 2, and 3 were determined according to the greenhouse potted plant bioassay method in Example 1.

[0079] Table 4 Biocontrol agents for wheat stem rot control greenhouse potted plant efficacy

[0080]

[0081] The results are shown in Table 4. The dispersant content in Comparative Example 1 was reduced, and the dispersant formula in Comparative Example 2 was changed, which affected the uniformity of seed coating, and the protective film of the agent on the seedlings was incomplete, resulting in a decrease in the prevention effect; while the thickener content in Comparative Example 3 was reduced, affecting the sustained release of the agent, resulting in a decrease in the persistence of the agent and a decrease in the prevention effect. Example 3 selects a suitable component ratio to make the seed coating uniform, form a complete protective film for the seedlings, and can play a protective role for a longer period of time, so the prevention effect is significantly higher than that of the comparative example, so the formula of Example 3 is selected for further experimental research.

[0082] Example 4. Screening and efficacy determination of the combination of Bacillus Velezii SFJ-27682 and 6% oligosaccharide-linked protein

[0083] 4.1 Greenhouse efficiency enhancement ratio screening

[0084] The Velez Bacillus SFJ-27682 bacterial agent prepared according to Example 3 was screened for a synergistic combination of SFJ-27682 bacterial agent and 6% oligosaccharide·chain protein according to the greenhouse potted plant bioassay method in Example 1. The seed dressing amounts of SFJ-27682 bacterial agent and 6% oligosaccharide·chain protein wettable powder were set to 900 g / 100 kg seeds, 600 g / 100 kg seeds, 300 g / 100 kg seeds, 100 g / 100 kg seeds, 50 g / 100 kg seeds, 25 g / 100 kg seeds, and 12.5 g / 100 kg seeds, respectively. Each seed dressing amount was then prepared into a composition with a mass ratio of 1:1, 1:3, 1:5, 1:7, 1:9, 3:1, 5:1, 7:1, and 9:1 for seed dressing, and two single agents were used as controls. The control effects of each treatment were determined, and the linear regression equation was calculated using the logarithmic value of each seed dressing concentration and the control efficiency probability value to calculate the EC 50 The theoretical and measured values ​​were used to evaluate the joint toxicity using the Wadley method.

[0085] EC 50 (th) = (a + b) / [a / EC 50 (A)+b / EC 50 (B)];

[0086] Synergy coefficient (SR) = EC 50 (th) / EC 50 (ob).

[0087] In the formula, A and B represent two drugs respectively, a and b represent the ratio of the two drugs respectively, ob is the actual observed value, and th is the theoretical value.

[0088] Table 5 Screening of greenhouse synergistic combination of Bacillus Velez SFJ-27682 and 6% oligosaccharide·chain protein wettable powder

[0089]

[0090] The results are shown in Table 5. The combinations of Bacillus Velez SFJ-27682 and 6% oligosaccharide·catenin wettable powder at 1:1, 1:3, 1:5, 1:9, and 3:1 had a certain synergistic effect on the prevention and control of wheat stem base rot at the greenhouse seedling stage. Among them, the 1:1 combination had the most obvious synergistic effect, and the synergistic coefficient could reach 2.59. Therefore, this synergistic combination was selected for greenhouse and field control efficacy determination.

[0091] 4.2 Greenhouse bioassay of synergistic combination

[0092] The Velez Bacillus SFJ-27682 fungicide prepared in Example 3 was combined with 6% oligosaccharide chain protein (Atai Ling) wettable powder in a mass ratio of 1:1, and 300 g / 100 kg of seeds were used for seed dressing. A chemical fungicide 6% tebuconazole seed coating agent 66.7 mL / 100 kg of seeds was used as a control. A blank control group CK (i.e., no seed dressing treatment) was added. The method was carried out according to the greenhouse bioassay method in Example 1. The plant height, root length, and fresh weight of each treated wheat were measured, and the disease index and greenhouse control effect and other indicators were calculated.

[0093] Table 6 Greenhouse bioassay of the combination of Bacillus Velez SFJ-27682 and 6% oligosaccharide-linked protein wettable powder

[0094]

[0095] The results showed that the 1:1 combination of Bacillus Velez SFJ-27682 and 6% oligosaccharide·chain egg (Atai Ling) wettable powder can increase the wheat emergence rate and promote wheat growth. Its protective effect is significantly better than that of the chemical fungicide 6% tebuconazole seed coating agent, and it does not affect the emergence of wheat.

[0096] 3.3 Field efficacy test of synergistic combination

[0097] In a mass ratio of 1:1, the Bacillus Velez SFJ-27682 agent and 6% oligosaccharide·chain protein (Atailing) wettable powder were combined at 300g / 100kg of seeds for seed dressing. The variety selected was Shixin 828, and a control group of 6% tebuconazole seed coating agent was set up.

[0098] Wheat seeds of each treatment group and the control group were planted in the field at the experimental farm of the Institute of Plant Protection, Hebei Academy of Agricultural and Forestry Sciences from October 2020 to June 2021. The survey was conducted during the grain filling period, and 20 to 30 wheat plants were sampled at 5 points. According to the slightly modified grading standard of Yang Yun et al., the disease index was calculated according to the formula to obtain the control effect.

[0099] Level 0: no browning symptoms;

[0100] Level 1: The browning area of ​​the first stem node is less than 25%;

[0101] Level 2: The browning area of ​​the first stem node is 25% to 50%;

[0102] Level 3: The browning area of ​​the first stem node is 50% to 75%;

[0103] Level 4: The first stem node accounts for more than 75% or the browning extends to the second and third stem nodes without causing withered and white ears;

[0104] Level 5: Wheat plants withered and white ears;

[0105] Level 6: The plants are dwarfed, dead, and have not produced headings. The number of white ears and the disease level of each plant are recorded, and the disease index, white ear rate, and control effect are calculated.

[0106] Disease index = ∑ (number of diseased plants × representative values ​​at each level) / (total number of plants surveyed × highest representative value) × 100;

[0107] White ear rate (%) = number of white ears / total number of plants surveyed × 100;

[0108] Disease index control effect (%) = (control disease index - treatment disease index) / control disease index × 100;

[0109] White ear rate control effect (%) = (control white ear rate - treatment white ear rate) / control white ear rate × 100.

[0110] Sampling was carried out at 5 points during the maturity period, and 0.5m was surveyed at each point. 2 Number of ears, take 20 to 30 wheat plants, remove invalid spikelets with less than 5 grains, investigate the average number of grains per ear, weigh the thousand-grain weight, and calculate the wheat yield. The calculation formula is as follows:

[0111] Theoretical yield = (number of effective ears per unit area × number of grains per ear × thousand-grain weight) / 10 6 ×0.85.

[0112] Table 7 Field control effect of combined application of Bacillus Velez SFJ-27682 and 6% oligosaccharide·chain protein wettable powder

[0113]

[0114] Table 8 Field yield-increasing effect of combined application of Bacillus Velez SFJ-27682 and 6% oligosaccharide·chain protein wettable powder

[0115]

[0116] The results of field tests showed that the combination of SFJ-27682 fungicide and 6% oligosaccharide·chain protein wettable powder for seed dressing had a good control effect on wheat stem base rot. The disease index and white ear rate in the adult stage were 62.25% and 65.32%, which were significantly higher than those of the chemical fungicide 6% tebuconazole seed dressing agent. It could also significantly increase wheat yield, increasing yield by 11.42% compared with the blank control.

[0117] It can be seen that the biocontrol agent and plant immune inducer composition of the present invention has a high antibacterial activity against wheat stem base rot pathogens, has a good control effect in the field, has a significant synergistic effect compared with the two components, and is significantly better than the chemical fungicide 6% tebuconazole seed coating agent; at the same time, the fungicide composition of the present invention is safe for wheat, does not affect wheat germination, and promotes growth and increases yield. The biocontrol agent and plant immune inducer composition of the present invention has a long duration of efficacy, has a high preventive effect on the occurrence of wheat stem base rot in the adult stage, and is conducive to reducing the risk of pathogen resistance and the impact of the environment.

[0118] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. Bacillus velezensis SFJ-27682, characterized in that Its deposit number is CGMCC NO.32000.

2. Use of the Bacillus Velezii according to claim 1.

3. Use of the Bacillus Velezii described in claim 1 in preventing and treating wheat stem base rot.

4. A biocontrol agent, characterized in that: The bacterial agent comprises the Velez bacillus according to claim 1, 5-10% of a dispersant, 1.2-2.5% of a synergist, 1-3% of a thickener, and 0.5-1.5% of a defoaming agent.

5. The biocontrol agent according to claim 4, characterized in that The dispersant is prepared by mixing sodium lignin sulfonate, phenethylphenol polyoxyethylene ether and Tween 80.

6. The biocontrol agent according to claim 5, characterized in that The mass ratio of sodium lignin sulfonate, phenethylphenol polyoxyethylene ether and Tween 80 in the dispersant is 1:1-3:2-5.

7. A composite biocontrol agent, characterized in that: The composite biocontrol agent comprises the bacterial agent according to claim 4 and 6% oligosaccharide-chain protein.

8. The composite biocontrol agent according to claim 7, characterized in that: The mass ratio of the bacterial agent to 6% oligosaccharide·chain protein is 1-10:1-10.

9. The culture medium of Bacillus Velezii according to claim 1, characterized in that The culture medium includes 1-5% sucrose, 1-5% soybean powder, 0.5-2% NaCl, 0.1-0.5% CaCO3, 0.01-0.05% KH2PO4 and 0.01-0.05% MgSO4·7H2O.

10. The culture medium of Bacillus Velez subtilis according to claim 9, characterized in that: The culture medium includes 3% sucrose, 1% soybean powder, 1% NaCl, 0.2% CaCO3, 0.02% KH2PO4 and 0.03% MgSO4·7H2O.

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