Bacillus velezensis capable of tolerating various environmental pollution and promoting growth and application of bacillus velezensis

Abstract

The invention discloses bacillus velezensis capable of tolerating various environmental pollution and promoting growth and application of the bacillus velezensis. A plant endophyte bacillus velezensis L381 strain is identified in wild rice, and the strain is high in environmental adaptability, can grow in the environment with the temperature of 15-40 DEG C and the pH value of 5-8, and can tolerate the NaCl concentration of 4%; the rice growth promoting agent has a good growth promoting function, can secrete auxin IAA, solubilize phosphorus, dissolve potassium and secrete siderophores, and can effectively promote rice growth. Meanwhile, the strain has stress resistance to environmental stress such as heavy metals and antibiotics, and tetracycline can be degraded; the strain has a wide antibacterial spectrum, and can be used as a biocontrol bacterium for preventing and treating various plant diseases. The plant endophyte L381 can adapt to variable temperature conditions and variable soil environments in the natural environment, has very strong practical application potential, not only improves the functions of bacillus velezensis, but also widens the application range of the strain.

Description

Technical Field

[0001] The present invention belongs to the field of microbial technology, and more specifically, relates to a Velez subtilis strain that tolerates multiple environmental pollutions and promotes growth, and application thereof. Background Art

[0002] Endophytes are fungi or bacteria that live inside the tissues and organs of plants at certain stages or all stages. They are commonly found in higher plants, such as woody plants, herbaceous plants, monocots and dicots. Studies have found that plant endophytes are systematically distributed in the cells and intercellular spaces of various organs and tissues of plants. In the long-term evolution, endophytes interact with host plants to form a mutualistic symbiotic relationship. In recent years, with the development of microbiology and molecular biology techniques, the research on endophytes has continued to deepen. They have become potential microbial pesticides, yield-increasing bacteria or potential biocontrol carriers in biological control. At present, scientists have isolated a variety of endophytes with potential application value from rice. These endophytes have shown great application potential in promoting rice growth, inhibiting pests and diseases, and improving stress resistance.

[0003] Bacillus has the advantages of broad antibacterial spectrum, strong stress resistance, secretion of multiple antibacterial substances, low production cost and high safety, and occupies an important position in biological control. However, among the existing microbial agent products, only limited strains have been registered and commercialized for use in agriculture. The main reason is that most Bacillus are easily affected by environmental factors such as pH, temperature, and salinity. The registered products are all used alone for their effects, and it is difficult to work together in a complex and changing environment. Because the field environment is complex and changeable, and does not fully meet the requirements of the optimal growth of microorganisms, the activity of microbial strains will be inhibited, thereby affecting its promotion of plant growth, the prevention and control of plant diseases, and the degradation efficiency of pollutants. At present, there are few strains with a wide range of activity, which can adapt to the changing soil environment, and can grow and play their role in a variety of complex polluted environments.

[0004] Therefore, it is urgent to develop and discover more beneficial microorganisms with strong environmental adaptability that can promote plant growth, effectively alleviate the stress of various plant pathogens, improve plant resistance to various stresses such as heavy metals, antibiotics, DEHP, etc., and can work synergistically in a complex and changing environment, thereby increasing crop yields and improving agricultural productivity. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the fact that the activity of plant endophytes is inhibited under various existing environmental pollutions and cannot work synergistically in a complex and changeable environment, and to provide a Velez subtilis strain that tolerates various environmental pollutions and promotes growth and its application.

[0006] The invention aims to provide a strain of Bacillus Velezii L381.

[0007] Another object of the present invention is to provide the application of Bacillus Velez L381 strain.

[0008] Another object of the present invention is to provide a product.

[0009] Another object of the present invention is to provide a method for promoting plant growth or preventing and controlling plant diseases in a complex polluted environment.

[0010] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0011] The present invention provides a Bacillus velezensis L381 strain, which has been deposited in Guangdong Provincial Microbiological Culture Collection Center on May 16, 2023, with a deposit number of GDMCCNo: 63468.

[0012] The present invention isolates a plant endophyte strain L381 from rice. The strain has a wide growth range and strong environmental adaptability. It can grow in an environment with a temperature of 15 to 40°C and a pH of 5 to 8, and tolerates a NaCl concentration of 4%. It can secrete auxin, has the ability to dissolve phosphorus, potassium and produce iron carriers, helps plants absorb nutrients in the soil, can promote rice growth, and has a good promoting effect when used in soil and plants. At the same time, the L381 strain also has good tolerance, can tolerate a variety of heavy metals and antibiotics, can grow in a culture medium with tetracycline as the only carbon source, has the effect of degrading tetracycline, and can better promote plant growth in a complex polluted environment.

[0013] In addition, the plant endophyte L381 strain also has a broad-spectrum antibacterial activity, can inhibit a variety of plant pathogens, and has good antibacterial activity against banana wilt pathogen (Fusarium.oxysporum f.sp.cubense), oxysporum Fusarium (Fusariumoxysporum), corn anthracnose pathogen (Colletotrichumgraminicola), rice sheath blight pathogen (Rhizoctoniasolani) and pink banana wilt pathogen (Fusarium arysperum f.sp.cudense), and can be used to prevent and treat plant diseases caused by them. In summary, the Velez Bacillus L381 strain provided by the present invention can tolerate a variety of polluted environments while having multiple beneficial properties such as phosphate solubilization, potassium solubilization, growth promotion, antibacterial, disease resistance, and degradation of antibiotics, and also has a wider antibacterial spectrum, which is rarely reported in existing microorganisms, and increases the bacterial species resources with more functions and excellent effects.

[0014] Therefore, the present invention provides the use of the L381 strain or its bacterial solution in promoting plant growth, or in promoting plant growth in an environment of salt stress, heavy metal and / or antibiotic pollution.

[0015] The present invention provides the use of L381 strain or its bacterial liquid in preparing a growth-promoting agent or in preparing a heavy metal ring and / or antibiotic pollution tolerance agent.

[0016] The present invention provides application of L381 strain or bacterial liquid thereof in preparing auxin and / or iron carrier.

[0017] The present invention provides application of L381 strain or bacterial liquid thereof in preparing phosphorus-dissolving and / or potassium-dissolving microbial fertilizer.

[0018] The present invention provides application of L381 strain or its bacterial liquid in degrading tetracycline or in preparing a tetracycline degradation agent.

[0019] The present invention provides application of L381 strain or bacterial liquid thereof in inhibiting plant pathogenic bacteria or in preventing and controlling plant diseases caused by plant pathogenic bacteria.

[0020] Preferably, the plant pathogen is one or more of banana wilt pathogen, Fusarium oxysporum, corn anthracnose pathogen, rice sheath blight pathogen, and pink banana wilt pathogen.

[0021] The present invention provides application of L381 strain or its bacterial solution in preparing antibacterial agent.

[0022] The present invention provides a product, comprising the above-mentioned L381 strain or its bacterial liquid.

[0023] Preferably, the bacterial liquid is a bacterial suspension.

[0024] More preferably, the concentration of the bacterial suspension is not less than 2×10 9 cfu / mL.

[0025] The present invention also provides a method for promoting plant growth in a complex polluted environment, wherein the L381 strain or its bacterial solution is used to treat plants or soil.

[0026] The invention also provides a method for preventing and controlling plant diseases, which comprises using the L381 strain or its bacterial liquid to treat plants.

[0027] The present invention has the following beneficial effects:

[0028] The present invention identifies a plant endophyte Bacillus Velez subtilis L381 strain, which has strong environmental adaptability, can grow in an environment with a temperature of 15-40°C and a pH of 5-8, and can tolerate a NaCl concentration of 4%. It also has good growth-promoting functions, can secrete the auxin IAA, dissolve phosphorus, dissolve potassium, and secrete iron carriers, and can effectively promote rice growth. At the same time, it has resistance to environmental stresses such as heavy metals and antibiotics, can degrade tetracycline, and has a wider antibacterial spectrum. As a biocontrol bacterium, it can prevent and control a variety of plant diseases, which not only improves the functional role of Bacillus Velez subtilis but also broadens the application scope of the strain. The plant endophyte L381 can adapt to changing temperature conditions and variable soil environments in the natural environment, and has strong practical application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the single colony morphology of strain L381 on the LB plate.

[0030] Figure 2 This is the morphological structure of strain L381 under scanning electron microscope.

[0031] Figure 3 This is the phylogenetic tree of strain L381.

[0032] Figure 4 It is the transparent zone of starch hydrolysis by strain L381.

[0033] Figure 5 The transparent zone is the cellulose hydrolysis zone of strain L381.

[0034] Figure 6 Qualitative results of IAA production by strain L381.

[0035] Figure 7 The growth of strain L381 on plates containing high concentrations of heavy metals and tetracycline.

[0036] Figure 8 These are the amplification results of the disease resistance genes Srf, ItuD, and ItuC of Bacillus L381.

[0037] Fig. 9 The inhibition of strain L381 on 5 pathogens.

[0038] Fig.10 This is the growth status of rice plants on the 30th day. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0040] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0041] The culture medium formula used in the embodiments of the present invention is:

[0042] MSM medium (g / L): K2HPO4 5.8 g, KH2PO4 4.5 g, (NH4)2SO4 2.0 g, MgCl2 0.16 g, CaCl2 0.02 g, Na2MoO4·2H2O 0.0024 g, KNO3 0.0012 g, FeCl3 0.0018 g, MnCl2·2H2O 0.0015 g, and the pH of the medium was adjusted to 7.0.

[0043] LB medium (g / L): 5.0 g yeast powder, 10.0 g peptone, 10.0 g NaCl, add ultrapure water to 1 L, and adjust the pH to 7.0.

[0044] King medium formula (1L): peptone 20.0g, K2HPO4 1.725g, glycerol 15mL, MgSO4·7H2O1.5g, tryptophan 0.1g, pH 7.2.

[0045] Colorimetric solution formula (50mL): 0.5mol / L FeCl3 1.0mL, concentrated sulfuric acid 30.0mL, distilled water 29.0mL.

[0046] PKO medium formula (1L, g / L): glucose 10.0g, (NH4)2SO4 0.5g, NaCl 0.3g, KCl 0.3g, MgSO4·7H2O 0.1g, MnSO4·H2O 0.03g, FeSO4 0.03g, Ca3(PO4)2 5.0g, yeast powder 0.5g, agar 20.0g, pH 7.0.

[0047] MSA-CAS medium: Add 50 mL of phosphate buffer and 50 mL of CAS dye solution to 1 L of sterilized MSA basal medium and mix well.

[0048] Fungal culture medium (1 L): 200.0 g potatoes (boiled for 30 min and filtered), 20.0 g glucose, 20.0 g agar, pH 7.0.

[0049] Example 1 Isolation and identification of plant endophytes

[0050] 1. Treatment of host plants

[0051] Collect wild rice plant samples from the wild rice collection garden in the south, wash them, and cut the roots, stems, and leaves into small pieces of about 4 cm in a clean bench. Soak them in 75% alcohol for 5 minutes, then soak them in 0.1% mercuric chloride for 3 minutes, stirring them with tweezers while soaking. Pour out all the mercuric chloride, and wash them with sterile distilled water for 7 times, 5 minutes each time. Take the last washing water and apply it to the LB plate. If there is no microbial growth, the host plant surface is completely disinfected. Remove 1 cm from each end of the surface-disinfected plant segment, and cut them into pieces with sterile scissors to break up the plant tissue and release the endophytes.

[0052] 2. Isolation and purification of strains

[0053] The above plant tissues were inoculated on LB plates, single colonies were selected and streaked using the quartering method, and strains were isolated on MSM plates with DEHP (concentration 200 mg / L) as the sole carbon source. Finally, pure cultured plant endophytes were obtained, in which the bacteria grew vigorously on DEHP as the sole carbon source, and the isolated strain was named L381.

[0054] 3. Morphological identification

[0055] The strain L381 was inoculated on the LB plate and cultured. The colonies were observed to be large, grayish white, with a rough and irregular surface, with ridges and wrinkles. Figure 1 As shown; scanning electron microscopy showed that the bacteria were short rod-shaped, about 0.4μm×1.4μm in size, with flagella on the surface, as shown Figure 2 shown.

[0056] 4. Phylogenetic analysis

[0057] The 16S rRNA gene sequences of 15 bacterial species closely related to strain L381 were downloaded from NCBI and compared with the 16S rRNA of strain L381 to construct a phylogenetic tree, such as Figure 3 As shown, strain L381 is most closely related to Bacillus velezensis and is on the same evolutionary branch.

[0058] Based on the above morphological identification and homology comparison results, strain L381 was identified as Bacillus velezensis in the genus Bacillus spp., named Bacillus velezensis L381 strain, and deposited in the Guangdong Provincial Microbiological Culture Collection Center (GDMCC) on May 16, 2023, with the deposit number GDMCC No: 63468, and the deposit address is 3rd Floor, Building 59, No. 100 Xianlie Middle Road, Yuexiu District, Guangzhou City, Guangdong Province.

[0059] 5. Whole genome sequencing analysis

[0060] The L381 bacteria were collected and sent to Novogene for whole genome sequencing. The third-generation single-molecule and Illumine NovaSeq PE150 platform and PacBio Sequel platform sequencing technology of PACBIO were used to obtain the chromosome genome sequence of strain L381, and no plasmid was detected. The chromosome genome sequence of strain L381 was uploaded to NCBI, showing that the genome length of strain L381 was 3861105bp, the number of genes was 4102, and the GC% content was 46.2%.

[0061] Example 2 Characteristic Analysis of Plant Endophyte L381 Strain

[0062] 1. Preparation of bacterial suspension

[0063] The strain L381 was inoculated into 50 mL of LB liquid medium and activated overnight to the logarithmic phase. The bacteria were collected by centrifugation at 4000 rpm for 5 min, washed three times with 0.9% sterile saline to remove impurities, and the washed bacteria were resuspended and the OD of the bacterial suspension was measured by a spectrometer (UV-2600, Shimadzu Corp., Japan). 600 nm value, and adjust the OD of bacterial suspension with 0.9% sterile saline 600 nm=1.0.

[0064] The strain L381 bacterial suspension (concentration OD 600 =1) As a bacterial suspension, the inoculation volume was standardized to 2% for subsequent experiments.

[0065] 2. Determination of the growth range of strain L381

[0066] The L381 bacterial suspension was inoculated onto the LB plate. A single factor experiment was used to set the temperature to 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, and 45°C (pH=7, 0.5% NaCl), the pH to 5, 6, 7, 8, 9, and 10 (culture temperature 30°C, 0.5% NaCl), and the NaCl concentration to 0.5%, 1%, 2%, 3%, 4%, and 5% (culture temperature 30°C, pH=7). The LB plate inoculated with L381 was cultured under the corresponding treatment conditions for 3 days, the colony growth was observed and recorded, and each treatment was repeated 3 times.

[0067] The results showed that strain L381 can grow in an environment with a temperature of 15-40°C and a pH of 5-8, indicating that the strain has a wide growth range; strain L381 can also tolerate a 4% NaCl concentration and has a certain salt tolerance. This shows that plant endophyte L381 can adapt to the changing temperature conditions and variable soil environment in the natural environment and has strong practical application potential.

[0068] 3. Determination of physiological and biochemical characteristics of strain L381

[0069] Conventional experimental methods were used to determine the physiological and biochemical indices of strain L381. The results showed that strain L381 was Gram-stain positive, methyl red test negative, acetylmethylcarbinol (VP) test positive, gelatin liquefaction test positive, catalase test positive, indole test negative, starch hydrolysis test positive, nitrate reduction test positive, ammonia production test positive, urease test positive, and cellulase test positive, as shown in Table 1.

[0070] Table 1 Physiological and biochemical characteristics of strain L381

[0071] Experimental indicators result Experimental indicator results Growth temperature range 15～40℃ Growth NaCl concentration range ≤4 Growth pH range 5～8 Gram stain+ Methyl red test - Starch hydrolysis+ VP test + Nitrate reduction+ Gelatin liquefaction + Ammonia production test+ Catalase + Urease- Indole test - Cellulase+

[0072] Note: +: positive; -: negative

[0073] At the same time, a transparent circle appeared on the test plate, and the transparent circle area was large, indicating that strain L381 degraded starch ( Figure 4 ) and degraded cellulose ( Figure 5 ) ability is strong, which is beneficial to the degradation of dead branches and leaves in the soil.

[0074] 4. Secretion of auxin IAA

[0075] Based on the active tryptophan metabolic pathway in the genome analysis of strain L381, six tryptophan metabolic genes were obtained through KEGG pathway analysis: atoB, fadB, OGDH, katE, ALDH, cypD_E, and the synthesis of auxin IAA is produced by tryptophan metabolism. Tryptophan can synthesize auxin through a series of enzymes. Strain L381 was inoculated into 10mL King liquid medium and cultured in a shaker at 30℃ and 120r / r / min for 2 days. IAA was determined by SalKowski colorimetry.

[0076] Qualitative determination: Pipette 50 μL of bacterial suspension onto a white ceramic plate and add 50 μL of colorimetric solution. After 15 minutes, the color turns red, indicating a positive result. Figure 6 As shown, it was shown that strain L381 can produce the auxin IAA.

[0077] Quantitative determination: The culture solution was centrifuged at 5000r / r / min for 3min, 1mL of the supernatant was added with 1mL of the colorimetric solution and allowed to stand in the dark for half an hour, and the absorbance was measured at a wavelength of 530nm. The standard curve was made with pure 3-indoleacetic acid (IAA), and the IAA concentration produced was calculated based on the standard curve. The IAA concentration produced by strain L381 within 2d was measured to be 1.55±0.36mg / L. It can be used to prepare auxin, which can promote cell division, leaf enlargement, stem elongation, adventitious root formation, seed growth, fruit growth, fruit setting and apical dominance, etc., and plays an important role in promoting plant growth.

[0078] 5. Phosphorus dissolving properties

[0079] Based on the KEGG pathway analysis of the strain L381 genome, it was found that strain L381 contained a phosphate-solubilizing gene cluster Pho, which contained genes including PhoD, PhoA, PhoE, PhoH, PhoR, and PhoP, and the phosphate-solubilizing characteristics of strain L381 were verified.

[0080] Experimental analysis: Inoculate the L381 bacterial suspension into PKO medium and culture at 30℃ for 3 days. A transparent circle is formed around the colonies on the plate, indicating that the strain has the ability to dissolve phosphorus. The molybdenum antimony colorimetric method is used to determine the effective phosphorus content in the culture solution and quantitatively determine the amount of phosphorus solubilized by the strain. Take 1mL of the culture solution and centrifuge it. Take an appropriate amount of the supernatant in a 50mL volumetric flask, dilute it to 30mL with water, add 5mL of molybdenum antimony reagent, make it up to 50mL, shake it well and let it stand at room temperature for 30min, and measure the OD 700 The phosphorus content in the colorimetric solution was calculated using the phosphorus standard curve, and the strain L381 was found to have a phosphorus solubility of 47.9±10.9 mg / L within 3 days, which helps plants absorb nutrients in the soil.

[0081] 6. Potassium-dissolving properties

[0082] Based on the KEGG pathway analysis of the strain L381 genome, it was found that the strain L381 contained the potassium-solubilizing gene AckA, and the potassium-solubilizing property of the strain L381 was verified. The L381 bacterial suspension was inoculated on a potassium feldspar culture medium plate and cultured at 30°C for 3 days. A transparent circle formed around the colony, indicating that the strain L381 has the ability to solubilize potassium, which can help release the insoluble potassium element in the soil and convert it into fast-acting potassium that can be directly absorbed and utilized by plants, thereby increasing the content of fast-acting potassium in the soil, meeting the plant's demand for potassium, and promoting plant growth and development.

[0083] 7. Siderophore production characteristics

[0084] Based on the KEGG pathway analysis of the strain L381 genome, it was found that strain L381 contained the iron carrier synthesis gene cluster Feu, which contained genes including FeuC, FeuB, and FeuA, and the iron carrier production characteristics of strain L381 were verified. The L381 bacterial suspension was inoculated into MSA-CAS liquid culture medium and cultured in a shaker at 30°C and 120r / min for 2 days. The liquid culture medium changed from blue to red, orange-yellow or purple, which was positive. It was observed that the MSA-CAS liquid culture changed from blue to red, indicating that Bacillus L381 has the ability to produce iron carriers.

[0085] In summary, both the DNA molecular level and the physiological and biochemical levels confirmed that strain L381 has the characteristics of secreting IAA, solubilizing phosphate and potassium, and producing iron carriers, which can better promote plant growth.

[0086] 8. Strain L381 is tolerant to heavy metals and antibiotics

[0087] Inoculate the L381 bacterial suspension onto an LB plate containing a single pollutant (heavy metal or antibiotic), set heavy metal treatment: CdCl2 concentration of 5mg / L and 50mg / L, PbCl2 concentration of 100mg / L and 500mg / L, CuCl2 concentration of 100mg / L and 500mg / L, MnCl2 concentration of 50mg / L and 100mg / L, set antibiotic treatment: tetracycline concentration of 5mg / L and 50mg / L. After inoculation, culture in an incubator at 30°C for 3 days, repeat each treatment three times, observe the growth of the strain, and test its tolerance.

[0088] The results of the test are as follows Figure 7 As shown, colonies appeared on the LB plate after 3 days, indicating that strain L381 can grow normally and is resistant to 5 mg / L Cd 2+ 、100mg / L Cu 2+ 、100mg / L Mn 2+ Tolerant, and at least tolerant to 500mg / L Pb 2+and 50mg / L tetracycline, and has the characteristics of tolerating a variety of high concentrations of heavy metals and antibiotics. At the same time, it was shown that strain L381 was able to grow in MSM medium with tetracycline as the only carbon source, indicating that strain L381 can absorb and degrade tetracycline. Since the above concentration is the highest concentration set in this experiment, strain L381 is not restricted in its growth environment. Further increasing the concentration of heavy metals and antibiotics, strain L381 can tolerate higher concentrations of Pb 2+ and tetracycline.

[0089] In summary, it is shown that strain L381 can adapt to the complex pollution in the natural environment and grow well, has practical application value and development potential, and provides an excellent strain resource for repairing agricultural ecosystems polluted by heavy metals and organic pollutants.

[0090] Example 3 Disease resistance of plant endophyte strain L381

[0091] Based on the KEGG metabolic pathway, key disease resistance genes were obtained in the L381 genome, such as the surfactin synthesis gene cluster Srf and the iturin synthesis gene cluster Itu. Primers were designed based on their gene sequences and tested. Srf, ItuD, and ItuC genes were successfully amplified in the L381 gene. The results are as follows Figure 8 As shown, the disease resistance function of the plant endophyte strain L381 was further analyzed.

[0092] Experimental analysis: The experiment was carried out using the plate confrontation method. Plant pathogens (A banana wilt pathogen, B Fusarium oxysporum, C corn anthracnose pathogen, D rice sheath blight pathogen, E pink banana wilt pathogen) were inoculated in the center of the plate, and strain L381 was inoculated around the four sides. The control treatment was not inoculated with strain L381. The plates were placed in a fungal incubator at 28°C, and the growth of strain L381 and pathogens was observed after colonies grew.

[0093] The results of the test are as follows Fig. 9 As shown in the figure, compared with the control group CK, strain L381 was found to have antibacterial activity against 5 plant pathogens. The colonies of pathogens in the experimental group were smaller than those in CK, and an antibacterial zone or antibacterial circle was formed around the colonies of L381. The growth of pathogens was obviously inhibited by L381, showing that its antibacterial activity was strong, indicating that strain L381 had a broad-spectrum antibacterial effect and could be used for the prevention and treatment of a variety of plant diseases.

[0094] Example 4 Growth-promoting effect of strain L381 on rice

[0095] Rice seedling cultivation: Select uniform and full rice seeds and sterilize them with 10% hydrogen peroxide for 20 minutes, soak and wash them with sterile water for 5 times. Moisten the surface-sterilized rice seeds for germination, sow them after they turn white, and fill the sowing hole tray with a mixture of equal amounts of paddy soil and organic matrix. Water them regularly after sowing, and transplant them when the seedlings grow to 5 cm in height.

[0096] Rice potted plants: 1.5 kg of soil per pot, 100 mL of L381 suspension for inoculation treatment and mix well with the soil, and an equal amount of inactivated bacterial solution for non-inoculation control to ensure that the final bacterial content is 10 8 cfu / g. Healthy seedlings with basically the same growth were selected for transplantation, with 3 rice plants in each pot, and the outer wall of the beaker was shaded. Three replicates were set for each treatment, arranged randomly, and the potted plants were grown outdoors in a natural environment of 28℃~35℃, the field water holding capacity of the soil was maintained at 60% (w / w), and rice nutrient solution was applied. The experimental period was 30 days, and pests and diseases were artificially controlled, and no pesticides were sprayed.

[0097] The growth of rice plants Fig.10 As shown, compared with the uninoculated control CK treatment, the plant height and fresh weight of the plants treated with strain L381 increased by 8.57% and 9.49%. Strain L381 can play a growth-promoting function such as secreting IAA, producing siderophores, solubilizing phosphate and potassium, and at the same time improve the disease resistance and tolerance of rice, allowing the rice to grow healthily and rapidly.

[0098] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A strain of Bacillus velezensis L381, characterized in that: This strain was deposited in Guangdong Provincial Microbiological Culture Collection Center on May 16, 2023, with the deposit number GDMCC No: 63468.

2. Use of the L381 strain or its bacterial solution according to claim 1 in promoting plant growth, or in promoting plant growth in an environment of salt stress, heavy metal and / or antibiotic pollution.

3. Use of the L381 strain or its bacterial solution according to claim 1 in the preparation of a growth promoter, or in the preparation of a heavy metal and / or antibiotic pollution tolerance agent.

4. Use of the L381 strain or its bacterial solution according to claim 1 in the preparation of auxin and / or siderophore.

5. Use of the L381 strain or its bacterial solution according to claim 1 in the preparation of phosphate-dissolving and / or potassium-dissolving microbial fertilizers.

6. Use of the L381 strain or its bacterial solution according to claim 1 in degrading tetracycline or in preparing a tetracycline degrading agent.

7. Use of the L381 strain or its bacterial solution according to claim 1 in inhibiting plant pathogens or in preventing and controlling plant diseases caused by plant pathogens, characterized in that: The plant pathogen is one or more of banana wilt pathogen (Fusarium.oxysporum f.sp.cubense), Fusarium oxysporum (Fusarium oxysporum), corn anthracnose pathogen (Colletotrichum graminicola), rice sheath blight pathogen (Rhizoctonia solani), and pink banana wilt pathogen (Fusarium arysperum f.sp.cudense).

8. Use of the L381 strain or its bacterial solution according to claim 1 in the preparation of an antibacterial agent, characterized in that: The antibacterial agent can inhibit one or more of the pathogens of banana wilt, Fusarium oxysporum, corn anthracnose, rice sheath blight and pink banana wilt.

9. A product, characterized in that Containing the L381 strain or its bacterial solution as described in claim 1.

10. A method for promoting plant growth or preventing and controlling plant diseases in a complex polluted environment, characterized in that: The L381 strain or its bacterial solution described in claim 1 is used to treat soil or plants.

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