Salt-tolerant bacillus Bah-38 strain and application thereof

Abstract

The invention provides a salt-tolerant bacillus strain Bah-38, the classification name of the salt-tolerant bacillus strain Bah-38 is the salt-tolerant bacillus strain Bah-38, the salt-tolerant bacillus strain Bah-38 is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number of the salt-tolerant bacillus strain Bah-38 is CGMCC NO.33642. The invention further provides a preparation method of the salt-tolerant bacillus strain Bah-38. According to the invention, a confrontation culture test proves that the Bah-38 strain has a bacteriostatic effect on fusarium solani, and the inhibitory effect of the strain on the fusarium solani reaches 51.4%. In a potting inoculation test, the prevention and control effect on the root rot caused by fusarium solani reaches 70.6% after the fermentation liquor of the strain is subjected to root irrigation treatment. Meanwhile, the obvious growth promoting effect is achieved. The fusarium solani has a high and stable control effect on fusarium solani, and is suitable for agricultural production requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of microorganisms, and in particular to a halotolerant Bacillus sp. Bah-38 strain and application thereof. Background Art

[0002] tomato( Solanum lycopersicum ) is an annual herbaceous plant of the genus Solanum in the Solanaceae family. It has a high nutritional value and is rich in nutrients such as carotene and vitamins. There are many varieties of tomatoes, suitable for both raw and cooked consumption, and they are very popular among consumers. Tomatoes are widely cultivated throughout my country, both in the open field and in protected areas. With the rapid development of my country's agriculture, the tomato industry has become one of the leading sectors of agricultural development in many regions. Tomato production in my country is widely distributed, and three methods have been used: solar greenhouses, plastic greenhouses, and open field cultivation, with cultivation occurring year-round. Based on cultivation methods and harvest seasons, the main advantageous production areas include the Huanghuaihai and Bohai Rim facility production areas, the northern high-latitude summer and autumn production areas, the Yangtze River Basin early spring production areas, the southwest winter production areas, and the southern China tomato production areas. However, due to the influence of natural factors and pests and diseases, tomato production in my country has experienced a certain degree of instability. According to surveys, my country is plagued by a wide variety of tomato diseases, with severe outbreaks occurring in increasingly widespread areas and over 10 causing significant yield reductions. These diseases are a major obstacle to high and stable tomato yields, with root rot being a key concern. With the expansion of tomato planting areas and protected cultivation, the incidence of tomato root rot, caused by Fusarium solani, has also increased, severely impacting plant growth and leading to a decline in tomato yield and quality. In mild cases, yield reductions can range from 10% to 20%, to more severe cases exceeding 40%, resulting in significant economic losses.

[0003] Fusarium solani ( Fusarium solani) is one of the pathogens that cause root rot, which is one of the most destructive soil-borne diseases of tomatoes and a worldwide disease. At present, tomato root rot occurs in all parts of my country, posing a serious threat to my country's tomato production. The optimum temperature for the growth and development of Fusarium solani is 25°C, and its host range is very wide. Tomatoes, peppers, eggplants, etc. can be infected by the disease. The pathogen prefers low temperature and high humidity. Infected in the seedling stage, the early symptoms are atrophy and yellowing, and the late symptoms are atrophy and collapse of the stem base, rot of the root system and stem base, and even death. The tomato root rot caused by Fusarium solani is characterized by hidden damage and difficulty in prevention and control. After damage by Fusarium solani, the stem base and roots of the tomato plant will turn brown and rot, disrupting the transport of water and nutrients, resulting in rapid wilt and necrosis of the aboveground part. In recent years, with the adjustment of agricultural industrial structure and the promotion of greenhouse and other facility cultivation technologies, the cultivated area of greenhouse tomatoes has been increasing. However, due to the difficulty of crop rotation and the increase in the multiple cropping index, root rot has caused serious problems with continuous cropping, resulting in huge economic losses. The damage caused by Fusarium solani has become a major problem that needs to be addressed in the tomato industry. Currently, the main control measures for root rot caused by Fusarium oxysporum include chemical control, biological control, crop rotation, and other measures. Among them, biological control has attracted widespread attention due to its safety and efficiency.

[0004] Beneficial microorganisms can inhibit pathogens through competition, antimicrobial activity, hyperparasitism, cross-protection, and the induction of disease resistance. It has been reported that several beneficial bacteria, including Paenibacillus polymyxa, Bacillus amyloliquefaciens, Bacillus mucilaginosus, Bacillus velezensis, and Trichoderma, can control tomato root rot caused by Fusarium solani. Furthermore, the metabolites of some biocontrol bacteria are also effective against root rot in various vegetables, including cucumbers and tomatoes. Paenibacillus polymyxa SeR8 produces cellulases, proteases, and siderophores, and can also decompose calcium phosphate, promoting pepper growth and significantly controlling other root diseases such as pepper blight. Effective colonization of biocontrol bacteria in the plant rhizosphere is crucial for their effectiveness. Once established, they can enhance plant resistance to pathogens and promote growth. For example, Pseudomonas fluorescens colonizes the rhizosphere soil of tomatoes and spreads to the root and stem tissues, effectively controlling Fusarium infection and promoting plant growth. In addition, beneficial microorganisms such as Bacillus subtilis can not only inhibit the growth of pathogens, but also induce the activity of tomato plants' stress-resistant enzymes, such as PPO, POD, and SOD, thereby preventing and controlling the harm of root rot.

[0005] Biological control is green and safe, but there are few officially registered products that can be used to prevent and control Fusarium solani in agricultural production. In addition, some products have problems such as low control efficiency, unstable control efficiency, and short survival time. Therefore, new and efficient biocontrol bacteria are urgently needed in production for the development of beneficial microorganisms to prevent and control Fusarium solani. Summary of the Invention

[0006] To address the above technical problems, the present invention provides a halogen-tolerant Bacillus sp. Bah-38 strain and its use. This halogen-tolerant Bacillus sp. Bah-38 strain is derived from rhizosphere soil in greenhouse vegetable fields in Langfang, Hebei Province. The preparation of the inoculum is simple and efficient, and the strain exhibits excellent efficacy against tomato root rot. Experiments have demonstrated that the isolated halogen-tolerant Bacillus sp. Bah-38 strain exhibits excellent control of root rot in both indoor and potted inoculation tests. This is of great significance for preventing and controlling the harmful effects of tomato root rot in production and ensuring safe vegetable production.

[0007] The technical solutions adopted in the present invention are as follows: According to one aspect of the present application, the present application provides a halophilic Bacillus subtilis Bah-38 strain ( Bacillus halotolerans ), whose taxonomic name is Bacillus halodurans Bacillus halotolerans , deposited in the General Microbiology Center of China Culture Collection Administration of Microorganisms, with the deposit number CGMCC NO.33642.

[0008] The Bah-38 strain was deposited with the General Microbiology Center of the China Culture Collection Administration under the Budapest Treaty on International Depository of Microorganisms prior to the application. The address is: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, 100101, China. The deposit date is February 24, 2025, and the accession number is CGMCC NO. 33642. The strain has an optimal growth temperature of 28°C. The strain was isolated and purified using LB medium (10g tryptone, 5g yeast extract, 10g sodium chloride, 15g agar powder, and sterile water to 1L). After culturing on LB plates at 28°C for 3 days, colonies appeared light yellow, nearly round or with irregular edges, opaque, shiny, and with a smooth, moist, and sticky surface. The bacteria were observed to be rod-shaped, 0.5-2.5 μm × 1.2-10 μm in size, and Gram-positive (G+). The morphology of Bah-38 strain was determined according to the Manual of Bacterial Identification, and it was determined to be a halophilic Bacillus ( Bacillus halotolerans ).

[0009] According to another aspect of the present application, the present invention further provides a fermentation broth of the Bah-38 strain, which is obtained by the following method: inoculating the Bah-38 strain into LB culture medium for fermentation to obtain the fermentation broth.

[0010] Specifically, the fermentation temperature is 25° C. to 30° C., the fermentation speed is 100 to 300 rpm, and the fermentation time is 2 to 5 days.

[0011] According to another aspect of the present application, the present invention further provides a microbial agent, which contains the fermentation broth.

[0012] Specifically, the concentration of Bah-38 strain in the fermentation broth is ≥2×10 7 cfu / mL.

[0013] According to another aspect of the present application, the present invention also provides the use of the strain, the fermentation broth, and the microbial agent in inhibiting Fusarium solani.

[0014] According to another aspect of the present application, the present invention also provides the use of the strain, the fermentation broth, and the microbial agent in preventing and treating tomato root rot.

[0015] According to another aspect of the present application, the present invention also provides a method for preventing and controlling tomato root rot, comprising applying the fermentation liquid and the microbial agent to tomato seedlings.

[0016] Specifically, the application is: inoculating the bacterial agent on the roots of tomato seedlings by root irrigation.

[0017] The beneficial effects of the present invention include but are not limited to: 1. The salt-tolerant Bacillus sp. Bah-38 strain of the present invention is a bacterium isolated from the soil of a vegetable field. It is safe and harmless to crops, and has a preventive and therapeutic effect on root rot caused by Fusarium solani. It has safety characteristics in agricultural applications.

[0018] 2. The present invention demonstrated the antibacterial activity of the Bah-38 strain against Fusarium solani through stand-off culture experiments, achieving an inhibitory effect of 51.4% against Fusarium solani. In potted plant inoculation experiments, the strain's fermentation broth achieved a 70.6% control effect against Fusarium solani-induced root rot. Furthermore, the strain exhibited a significant growth-promoting effect. This strain exhibits a high and stable control effect against Fusarium solani, making it suitable for agricultural production needs.

[0019] 3. The present invention is the first to apply the salt-tolerant Bacillus subtilis Bah-38 strain to the prevention and control of tomato root rot caused by Fusarium solani, providing an important basis for its application in the prevention and control of root rot in agricultural production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a confrontation culture of biocontrol bacteria and root rot fungi. Note: The blue circle represents the LB plate, the red dot in the middle is Fusarium solani, and the blue dots 1-4 around it represent the four bacterial strains and their numbers in the confrontation culture; Figure 2 The colony and streak morphology of the halodurable Bacillus subtilis strain Bah-38; Figure 3 The results of the confrontation culture between Bah-38 strain and root rot pathogen, A is the colony morphology of the positive side of the confrontation treatment, B is the colony morphology of the control; Figure 4 These are the aboveground parts of tomatoes in different treatment groups; Figure 5 These are the rhizome parts of tomato roots in different treatment groups. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to specific embodiments. The following embodiments are only provided to facilitate those skilled in the art to understand the technical solutions of the present invention, to implement or use the present invention, and are not intended to limit the scope of protection of the present invention.

[0022] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the examples, unless otherwise specified, are all conventional methods in the art.

[0023] Example 1 Rapid Isolation and Screening of Rhizosphere Biocontrol Bacteria First, prepare LB agar plates on a sterile workbench. The composition is 10g tryptone, 5g yeast extract, 10g sodium chloride, and 15g agar powder. The volume is adjusted to 1L with sterile water and autoclaved at 121°C for 20 minutes. The plates are then poured into 10cm diameter Petri dishes and plated for use in soil bacterial isolation. For the preparation of LB liquid medium, omit the agar powder and follow the same process as above. PDA medium: 200g potatoes, 20g glucose, and 15g agar powder are adjusted to 1L, pH = 7.0. To prepare the plate, peel the potatoes, weigh 200g, cut them into pieces, and boil them for 15 minutes. Filter through gauze to remove the pieces and residue. The filtrate is then added with 20g glucose and 15g agar powder. The filtrate is autoclaved at 121°C for 20 minutes, and plated into Petri dishes for analysis of its inhibitory activity against Fusarium solani.

[0024] Soil samples were collected evenly from the vegetable fields. Three separate 200g samples were taken from each sample and mixed thoroughly. 50g of each sample was added to 1000mL of distilled water, stirred thoroughly, and allowed to stand for 3 minutes. 1mL of the supernatant was diluted 100-fold with sterile water, and 50μL of the diluted solution was spread onto LB agar plates. After the soil dilution was evenly spread, the plates were inverted and incubated in a 28°C incubator for 2 days. After bacterial colonies grew on the plates, individual colonies were picked and streaked onto LB agar plates to isolate them for analysis in the standoff culture test. Using a sterile toothpick, 30-50 individual colonies were randomly picked from each LB agar plate. Each colony was numbered sequentially, starting with 1. Single colonies were then picked from each of the five culture dishes until the number reached 200. Each numbered single colony was picked up with a sterile toothpick and placed at the bottom of a 2.0 ml sterile centrifuge tube. 1.0 ml of LB liquid medium was added to each centrifuge tube and cultured at 28°C and 180 rpm for 2 days. Then 20 μl of the culture medium was taken out and cultured against Fusarium solani on a PDA plate. Four bacterial strains were inoculated at equal distances around the inoculation point of Fusarium solani in each culture dish for rapid screening. Figure 1 In the screening, if the bacterial colonies have an inhibitory effect on root rot, an inhibition line will be formed for the root rot fungus colonies. The edge of the inhibition line is clear, and the farther the distance, the more significant the inhibitory effect, which is used as the screening standard. After three days of confrontation culture, 198 of the 200 colonies in the confrontation culture showed no inhibitory effect, with the root rot bacteria able to cover the bacterial colonies; while two showed inhibitory effects, forming an inhibition line, numbered 38 and 171. Judging by the distance from the inhibition line to the colony, the inhibition distance of No. 38 was 0.6±0.1cm, while that of No. 171 was 0.1±0.1cm. It can be seen that the inhibition line of No. 38 was obvious and the effect was significant. Ultimately, colony No. 38 was selected as the biocontrol agent for subsequent research.

[0025] Example 2: Purification and identification of biocontrol bacteria strain No. 38 Isolate and purify strain 38 by streaking on LB agar plates. Pick a single colony from the LB agar plate and observe its growth and morphology. Perform Gram stain analysis for bacterial identification. Perform morphological analysis and species identification according to the Bacterial Identification Manual.

[0026] A single colony was picked with a sterile toothpick and gently tapped on the bottom of a PCR tube to stick it to the tube. This served as a template for PCR amplification. The universal primers for 16sDNA fragments used in bacterial molecular identification, 27F: 5'-AGAGTTTGATCCTGGCTCAG-3' and 1492R: 5'-GGTTACCTTGTTACGACTT-3', were used to sequence a fragment of the mitochondrial DNA of the Bah-38 strain. The PCR amplification reaction system consisted of 50 μL of ExTaq MIX, 1 μL of forward primer, 1 μL of reverse primer, and 23 μL of sterile water. Amplification conditions included lysis at 94°C for 5 min, followed by 30 cycles of 94°C for 30 s, 55°C for 30 s, and 72°C for 1 min; the amplification was terminated at 72°C for 10 min. Amplified products were separated and identified by 1% agarose gel electrophoresis and directly sequenced in both directions. Blast comparisons were performed on the NCBI website.

[0027] The test results can be found in Figure 2 After culturing the obtained strain No. 38 on LB medium plates at 28°C for 3 days, the colonies were light yellow, nearly round or with irregular edges, opaque, shiny, and smooth, moist, and sticky. Staining revealed that the bacteria were rod-shaped, 0.5-2.5 μm × 1.2-10 μm in size, and Gram-positive (G+). Morphological analysis of strain No. 38 was performed according to the "Bacterial Identification Manual," confirming that it was a halodurable Bacillus sp. Bacillus halotolerans ), and its official preservation number is Bah-38.

[0028] The 16S rDNA region of the Bah-38 strain was amplified using 16S universal primers 27F and 1492R. The PCR product was electrophoresed on a 1% agarose gel. Sequencing analysis revealed that the amplified 16S rDNA sequence of the strain was 1411 bp (SEQ ID NO. 1). BLAST analysis of the 16S sequence fragment of the strain showed that the Bah-38 strain was similar to the halodurogenic Bacillus ( Bacillus halotolerans ) bacteria similarity reached 100%, and the strain was identified as halogen-resistant Bacillus ( Bacillus halotolerans ).

[0029] Example 3: Verification and analysis of the inhibitory effect of the halodurable Bacillus subtilis strain Bah-38 on Fusarium solani Experimental culture medium and its formula: LB medium: 10g tryptone, 5g yeast extract, 10g sodium chloride, 15g agar powder, dilute to 1L with sterile water. After preparation, sterilize by autoclaving at 121°C for 20 minutes, then plate onto a Petri dish for bacterial isolation and purification. Liquid LB medium without agar is used for fermentation broth cultivation.

[0030] PDA medium: 200g potatoes, 20g glucose, 15g agar powder, dilute to 1 L, pH = 7.0. To prepare, peel the potatoes, weigh 200g, cut into pieces, and boil for 15 minutes. Filter through gauze to remove the pieces and residue. Add 20g glucose and 15g agar powder to the filtrate, sterilize at 121°C for 20 minutes, and then plate onto Petri dishes for analysis of the inhibitory activity of the halodurable Bacillus sp. strain Bah-38 against Fusarium solani.

[0031] Preparation of Bah-38 strain fermentation broth First, the halodurable Bacillus sp. Bah-38 strain was streaked and activated on LB medium plates and cultured at 28°C for 3 days. The activated colonies were scraped with an inoculation loop and inoculated into a 250 mL Erlenmeyer flask containing 100 mL of LB liquid medium. The culture was shaken (200 rpm) at 28°C for 3 days. When the OD600 absorbance of the fermentation broth reached 2.0, 20 μL was pipetted with a pipette for confrontation culture in a culture dish to analyze the inhibitory effect of the bacteria on Fusarium solani.

[0032] Preparation of the test fungus Fusarium solani Fusarium solani was maintained by the Disease Group of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences. For preparation, a bacterial mass was first extracted from a culture tube using an inoculating needle on a sterile operating table. The plate was then inoculated onto a PDA plate and incubated at 28°C in the dark for three days. A sterile micropipette with a sterile borer was then used to remove a 3 mm diameter piece of bacteria from the Fusarium solani colony. This was then used in a head-off test to analyze the inhibitory effect of the halodurable Bacillus sp. strain Bah-38 against Fusarium solani.

[0033] Test methods PDA culture dishes were used for counter-culture and analysis of antibacterial activity. A root rot fungus colony was inoculated in the center of the dish. Two drops of biocontrol solution (20 μL each) were then inoculated from either side of the colony cake to the center of the dish edge. The solution was gently dripped in to prevent it from flowing. The culture was then incubated at 25°C in the dark. Clear water was used as a control in place of the solution. After three days, the growth of the root rot fungus colony was observed and compared to the diameter of the control colony. The inhibitory effect on the root rot fungus was determined, as calculated in Equation 1. Five dishes were used for each treatment, and the experiment was repeated three times.

[0034] The results showed that at 3 days, the salt-tolerant Bacillus strain Bah-38 showed a significant inhibitory effect on root rot fungi. In the water control, the diameter of the root rot fungi colonies reached 7.2±0.1cm, while in the Bah-38 strain treatment, the root rot fungi colonies were only 3.5±0.1cm ( Figure 3 , Table 1). Calculation showed that the inhibition rate of Bah-38 against root rot pathogens reached 51.4%.

[0035] Table 1 test Diameter of opposing colonies (cm) Diameter of control colony (cm) Repeat 1 3.52 7.28 Repeat 2 3.56 7.16 Repeat 3 3.42 7.18 average 3.5±0.1 7.2±0.1 Antibacterial rate - 51.4% Example 4: Effect of Halophilous Bacillus subtilis Bah-38 on Root Rot in Potted Plants Preparation of Bah-38 strain fermentation broth The salt-tolerant Bacillus subtilis Bah-38 strain was streaked on an LB medium plate and cultured at 28°C for 3 days. The activated colonies were scraped with an inoculation loop and inoculated into a 250 mL Erlenmeyer flask containing 100 mL of liquid culture medium. The culture was shaken at 28°C (200 rpm) for 3 days. When the OD600 absorbance of the fermentation liquid reached 2.0 (the concentration of the Bah-38 strain at this time was 2 × 10 7 cfu / mL) were used in potted plant inoculation control experiments to analyze the inhibitory effect of the fungus on Fusarium solani.

[0036] Preparation of pathogenic fungus Fusarium solani Fusarium solani was maintained by the Disease Group of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences. For preparation, a sterile operating table was used to extract a bacterial mass from a culture tube using an inoculating needle. This mass was then inoculated onto a PDA plate and incubated at 28°C in the dark for 3 days. Five 3-mm-diameter bacterial cakes were then removed from the F. solani colonies using a sterile borer and inoculated into PDA liquid medium. The culture was then shaken at 200 rpm for 5 days at 28°C. The bacterial mass, mycelium, and impurities were then filtered through sterile gauze to remove the bacterial mass, mycelium, and impurities. Spores were collected from the filtrate and adjusted to a spore concentration of 1 × 107 cfu / ml with sterile water for use in potted plant inoculation experiments.

[0037] Preparation of tomato seedlings Moneymaker tomato (Lycopersicon esculentum) seeds were soaked in 0.5% NaClO for 2-3 minutes, then rinsed multiple times with sterile water until no NaClO residue remained. The surface-sterilized seeds were spread flat on moistened sterile filter paper, then spread in a Petri dish and placed in a 30°C incubator for germination. When the seeds germinated and just emerged from the radicle, the germinated tomato seeds were sown in seedling trays containing a mixture of sterilized peat soil and vermiculite in a 2:1 volume ratio. The seeds were grown naturally in a 28°C greenhouse to obtain healthy tomato seedlings for subsequent experiments.

[0038] (4) Inoculation test Tomato seedlings at the 3-4 leaf stage with consistent growth were selected and divided into 3 groups, and the following treatments were performed: healthy plants + sterile water (A), healthy plants + Fusarium solani (B), and healthy plants + Bah-38 + Fusarium solani (C). In the C group, the biocontrol bacteria Bah-38 was inoculated by root irrigation, with 20 ml of fermentation liquid per pot (10 cm✕10 cm) and cultured in a solar greenhouse at 28±2°C. After 2 days, the tomato seedlings were gently separated from the soil and inoculated with root rot pathogens by root immersion. The tomato roots of groups B and C were immersed in the prepared Fusarium solani spore suspension (10 7 cfu / ml) for 15 minutes and then cultured in a greenhouse at 28±2°C. Group A served as a control and was immersed in sterile water for a simulated inoculation treatment. Ten plants were treated in each group, with three replicates. Sterile water (Group A) served as a negative control, while plants inoculated only with the pathogen Fusarium solani (Group B) served as a positive control. Following Fusarium solani treatment, the plants were replanted in their original pots. Fifteen days after inoculation with the biocontrol agent, the aboveground and belowground disease patterns were observed. Fresh weight, plant height, and disease severity were statistically analyzed for each treatment, and the incidence rate, disease index, and relative control efficacy were calculated.

[0039] The calculations of disease grade, incidence, disease index and relative efficacy are as follows (Table 2).

[0040] Table 2 Tomato root rot disease survey grading standards Disease level Root symptom description 0 No infection symptoms on the rhizomes 1 The diseased area is less than 1 / 4 of the rhizome area, with watery brown spots, but no rot. 2 The diseased area accounts for 1 / 4-1 / 2 of the rhizome area. The main root begins to rot and the base of the stem begins to constrict, but new lateral roots grow. There are no obvious symptoms above ground. 3 The diseased area accounts for 1 / 2-3 / 4 of the rhizome area, most of the main root rots, the base of the stem shrinks, the lateral roots no longer grow, and the leaves above the ground wither. 4 The diseased area accounts for more than 3 / 4 of the rhizome area, the base of the stem is constricted into a linear shape, and the plant is almost dead. Incidence calculation formula: Incidence rate (%) = (number of diseased plants / number of surveyed plants) × 100 The calculation formula of disease index is: Disease index = [Σ(number of diseased plants × corresponding disease level) / (total number of plants × highest disease level)] × 100 Where: ∑ — The sum of the product of the value of each disease level and the number of plants at each disease level Relative protection effect calculation formula: Relative control efficacy (%) = (control disease index - treatment disease index) / control disease index × 100 (5) Test results The experiments revealed that the aboveground parts of tomatoes treated with the Bah-38 strain (Group C) grew significantly more vigorously than those inoculated only with Fusarium solani (Group B), with dark green leaves and robust growth. In contrast, plants inoculated with Fusarium solani (Group B) exhibited yellowing leaves and wilting. Testing revealed that the incidence of root rot in tomatoes treated with Bah-38 was only 57.3%, a 43% decrease compared to the positive control (Group B). The disease index was only 23.3, significantly lower than Group B's 79.2, achieving a relative control efficacy of 70.6% (Table 3). These results demonstrate that the Bah-38 strain has an inhibitory effect on Fusarium solani in tomatoes and holds significant potential for application in agricultural production.

[0041] At the same time, the plant height and fresh weight were detected (Table 4, Figure 4-5 Results showed that tomato plants treated with the Bah-38 strain had an average fresh weight of 3.4g per plant and an average plant height of 23.4cm per plant, compared to the positive control treated with the root rot fungus, which had an average fresh weight of 1.6g per plant and an average plant height of 19.3cm per plant. Compared to the sterile water control, the Bah-38 strain significantly promoted tomato plant growth, with plant height increasing by 5.9% and fresh weight by 36.0%.

[0042] Table 3 Disease index and control effect of different treatments deal with Incidence (%) Disease index Relative prevention effect (%) Sterile water control 0 0 - Root rot treatment 100% 79.2 - Treatment with Bah-38 57.0% 23.3 70.6% Table 4 Fresh weight and plant height of tomatoes in different treatment groups deal with Plant height cm Fresh weight g Plant height promotion rate (%) Fresh weight growth promotion rate (%) Sterile water control 22.1 2.5 - - Root rot treatment 19.3 1.6 87.3% 64.0% Bah-38 Processing 23.4 3.4 105.9% 136.0% The above is a detailed introduction to a salt-tolerant Bacillus subtilis Bah-38 strain and its application provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, the present invention can also be improved and optimized, and these improvements and optimizations also fall within the scope of protection of the claims of the present invention.

Claims

1. A salt-tolerant Bacillus subtilis Bah-38 strain ( Bacillus halotolerans ), characterized in that Its classification name is Bacillus halodurans Bacillus halotolerans , deposited in the General Microbiology Center of China Culture Collection Administration of Microorganisms, with the deposit number CGMCC NO.33642.

2. The fermentation broth of the Bah-38 strain according to claim 1, characterized in that The fermentation broth is obtained by the following method: the Bah-38 strain is inoculated into LB culture medium for fermentation to obtain the fermentation broth.

3. The fermentation broth of the Bah-38 strain according to claim 2, characterized in that The fermentation temperature is 25° C. to 30° C., the fermentation speed is 100 to 300 rpm, and the fermentation time is 2 to 5 days.

4. A microbial agent, characterized in that: The microbial agent comprises the fermentation broth according to claims 2 to 3.

5. The microbial agent according to claim 4, characterized in that The concentration of Bah-38 strain in the fermentation broth is ≥2×10 7 cfu / mL.

6. Use of the strain according to claim 1, the fermentation broth according to claim 2 or 3, or the microbial agent according to claim 4 or 5 in inhibiting Fusarium solani.

7. Use of the strain according to claim 1, the fermentation liquid according to claim 2 or 3, or the microbial agent according to claim 4 or 5 in preventing and controlling tomato root rot.

8. A method for preventing and controlling tomato root rot, characterized in that: The fermentation liquid according to claim 2 or 3 and the microbial agent according to claim 4 or 5 are applied to tomato seedlings.

9. The method according to claim 8, characterized in that The application comprises the following steps: inoculating the bacterial agent on the roots of tomato seedlings by root irrigation.

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