Pseudomonas aeruginosa Pb-13 strain and application thereof

Abstract

The invention provides a Pseudomonas brassicae Pb-13 strain, the classification name of the Pseudomonas brassicae Pb-13 strain is Pseudomonas brassicae Pb-13 strain, the Pseudomonas brassicae Pb-13 strain is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number of the Pseudomonas brassicae Pb-13 strain is CGMCC NO.33643. The Pseudomonas brassicae Pb-13 strain is named as Pseudomonas brassicae Pb-13 strain, and the Pseudomonas brassicae Pb-13 strain is named as Pseudomonas brassicae Pb-13 strain. Experiments show that the bacterial strain Pb-13 has the bacteriostatic effect on fusarium solani, and the inhibitory effect of the bacterial strain on the fusarium solani reaches 65.1%. In a pot experiment, the strain fermentation liquor is subjected to root irrigation treatment, the prevention and control effect on the root rot caused by fusarium solani reaches 72.5%, meanwhile, the plant height and fresh weight can be increased, the obvious growth promotion effect is achieved, the prevention and control effect is high and stable, and the requirements of agricultural production are met.

Description

Technical Field

[0001] The present invention relates to the technical field of microorganisms, and in particular to a Pseudomonas rapeseed Pb-13 strain and an application thereof. Background Art

[0002] tomato( Solanum lycopersicum Tomatoes are a major staple vegetable crop, widely cultivated worldwide for their high quality, diverse variety, and adaptability. Global annual production reaches 170 million tons, ranking first among vegetable crops. According to 2021 data, my country is a major producer of fresh and processed tomatoes and the world's largest tomato seed market, exceeding 1.5 billion yuan.

[0003] In recent years, the planting area and yield of tomatoes in my country have been steadily increasing, and the tomato industry has great economic value. However, tomato plants are susceptible to pests and diseases, causing huge economic losses. Fusarium solani Root rot is one of the most destructive soilborne diseases of tomatoes. First discovered in Japan in 1974, it subsequently appeared in the southern United States. Currently, it poses a significant threat to tomato production in Canada, Mexico, Israel, the United States, Japan, South Korea, South Africa, and most European countries. The disease was first discovered in Shouguang City, Shandong Province, and has now spread across large areas of vegetable-producing regions throughout my country, posing a serious threat to tomato production. Fusarium solani has an optimal growth temperature of 25°C and a wide host range, infecting tomatoes, peppers, eggplant, cucumbers, and other crops. The pathogen prefers low temperatures and high humidity, with an optimal growth temperature of 10-20°C, and an optimum temperature of 18°C. It has a long disease cycle and can infect seedlings during the seedling stage, with symptoms generally becoming apparent during flowering. Early symptoms in the seedling stage include yellowing and stunted growth, while later symptoms include shriveling and collapse of the stem base, root rot, and even death. Tomato root rot caused by Fusarium solani is insidious and difficult to control. After the damage of Fusarium solani, the stem base and roots of tomato plants will turn brown and rot, causing the aboveground parts to wilt and necrotize rapidly. As a result, the yield will be reduced by 20-30% in mild cases, and in severe cases, large areas of the whole plant will die, resulting in a total crop failure. In recent years, with the adjustment of the agricultural industrial structure and the promotion of facility cultivation technologies such as greenhouses, the planting area of tomatoes in facility vegetable cultivation has become increasingly larger. Due to the difficulty of crop rotation and the increase in the multiple cropping index, root rot has caused serious problems of continuous cropping, causing huge economic losses. The damage of Fusarium solani has become a major problem that needs to be solved urgently in the tomato industry. At present, the main prevention and control measures for root rot caused by Fusarium oxysporum are chemical control, biological control, crop rotation and other measures. Among them, biological control has received widespread attention due to its safety and efficiency.

[0004] The main chemical agents currently on the market for tomato root rot prevention and control fall into two categories: fumigants and fungicides. Fumigants include dazomethon, methamphetamine, and calcium cyanamide. These typically react with water to release toxic gases, killing Fusarium solani in the soil. These fumigants are often broad-spectrum, killing both pathogens and beneficial microorganisms in the soil. Residual fungi can also cause phytotoxicity to vegetables planted later. Chemical fungicides can be categorized by their structure, including halogenated hydrocarbons, methyl thioisothiocyanates, organophosphates, carbamates, and antibiotics. These fungicides often have a rapid effect against Fusarium solani, but their long-term use can lead to severe residual contamination and drug resistance in the soil, significantly impacting the safe production of vegetables.

[0005] Biological control, the use of beneficial microorganisms to control pests, is green and safe, closely linked to the green control of agricultural pests and diseases, and is gaining increasing attention. However, there are currently few registered commercial products suitable for the control of Fusarium solani in agricultural production, and some products suffer from low efficacy, unstable efficacy, and short survival times. Therefore, new and effective biocontrol bacteria are urgently needed in production. Summary of the Invention

[0006] To address the above technical problems, the present invention provides a method for preparing a Pseudomonas rapeseed Pb-13 strain and a microbial agent thereof. The Pseudomonas rapeseed Pb-13 strain of the present invention has a good control effect on tomato root rot. Experiments have shown that the isolated Pseudomonas rapeseed Pb-13 strain has a good control effect on root rot in both indoor and potted plant experiments, which is of great significance for preventing and controlling the harm of tomato root rot and ensuring the safe production of vegetables.

[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 Pseudomonas campestris Pb-13 strain ( Pseudomonas brassicacearum ), whose taxonomic name is Pseudomonas campestris Pseudomonas brassicacearum , deposited in the General Microbiology Center of China Culture Collection Administration of Microorganisms, with the deposit number CGMCC NO.33643.

[0008] The Pb-13 strain has been deposited with the General Microbiology Center of the China Culture Collection Administration under the Budapest Treaty. 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. 33643. The strain has an optimal growth temperature of 25-28°C. The strain was isolated and purified in LB medium (10 g tryptone, 5 g yeast extract, 10 g sodium chloride, 15 g agar powder, and sterile water to 1 L). After culturing on LB plates at 28°C for 3 days, colonies exhibited transparent, glossy, rounded convexities with smooth, moist surfaces and neat edges. Staining revealed rod-shaped colonies measuring 0.8 × 1.0-2.0 μm. Gram-negative (G-), the strain Pb-13 was classified and identified according to the Manual of Bacterial Identification, and the strain was identified as Pseudomonas campestris ( Pseudomonas brassicacearum ).

[0009] According to another aspect of the present application, the present application also provides a method for preparing the fermentation broth of the Pseudomonas rapeseed Pb-13 strain, wherein the Pb-13 strain is inoculated 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 application also provides a microbial agent, which comprises the fermentation broth of the Pb-13 strain according to claim 2 or 3.

[0012] Specifically, the concentration of Pb-13 strain in the fermentation broth is ≥2×10 7 cfu / mL.

[0013] According to another aspect of the present application, the present application also provides the use of the strain, the fermentation broth prepared by the preparation method, and the microbial agent in preventing and controlling Fusarium solani.

[0014] According to another aspect of the present application, the present application also provides the use of the strain, the fermentation liquid prepared by the preparation method, and the microbial agent in preventing and treating tomato root rot.

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

[0016] Specifically, the application is: soaking the roots of the tomato seedlings in a solution containing the fermentation liquid or microbial agent.

[0017] The beneficial effects of the present invention include but are not limited to: 1. The Pseudomonas rapeseed Pb-13 strain of the present invention is a bacterium isolated from open-field vegetable field soil. 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. Experiments have demonstrated the antibacterial effect of the Pb-13 strain against Fusarium solani, achieving a 65.1% inhibitory effect. In potted plant experiments, root irrigation with a fermentation broth from this strain achieved a 72.5% control effect on Fusarium solani-induced root rot. Furthermore, the strain increased plant height and fresh weight, demonstrating a significant growth-promoting effect. This high and stable control effect is suitable for agricultural production needs.

[0019] 3. The present invention is the first to apply the Pseudomonas campestris Pb-13 strain to the prevention and control of tomato root rot caused by Fusarium solani, providing an important basis for its biocontrol application. 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 surrounding blue dots and numbers represent the four bacterial strains and numbers in the confrontation culture. A is a schematic diagram of the confrontation culture, and B is a diagram of the confrontation culture results. Figure 2 The colony and streak morphology of Pseudomonas campestris strain Pb-13; Figure 3 Results of the confrontation culture of Pb-13 strain and root rot pathogen; A: Colony morphology of the front side of the confrontation treatment, B: Colony morphology of the back side of the confrontation treatment, C: 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. 50μL of the diluted solution was then spread onto LB agar plates. The soil dilution was evenly spread and inverted in a 28°C incubator for 2 days. After colonies developed on the plates, individual colonies were picked and streaked onto LB agar plates for isolation and purification. Single colonies were obtained for analysis of standoff culture results. Using a sterile toothpick, 30-50 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 total 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 was aspirated and cultured on a PDA plate against Fusarium solani. Four bacterial strains were inoculated at equal distances around the inoculation point of Fusarium solani in each culture dish for rapid high-throughput screening. Figure 1 As shown in A. In the standoff screening, if the bacterial colony has an inhibitory effect on the root rot fungus colony, an inhibition line will be formed against the root rot fungus colony. The edge of the inhibition line is clear, and the farther the distance, the more significant the inhibitory effect, which serves as the screening standard.

[0025] After 3 days of confrontation culture, we found that most of the bacteria in the soil were strains with no inhibitory effect in 200 colony confrontation cultures. Among the isolated bacteria, 197 were strains with no inhibitory effect, and the root rot bacteria could cover the bacterial colonies. Among them, 3 had inhibitory effects (strains 13, 116, and 152), and could form an inhibition line against the root rot colonies. Based on the vertical distance from the inhibition line to the colony and the morphology, we preliminarily classified the biocontrol bacteria, such as Figure 1 B. Among them, the inhibition line of colony No. 13 was obvious, and the distance between the colony and the inhibition line was 1.1±0.1cm. Although the other two colonies No. 116 and No. 152 could form an inhibition line, the distance from the inhibition line was less than 0.5cm, which were 0.3±0.1cm and 0.1±0.1cm respectively. Therefore, the strain with the most obvious inhibitory effect (No. 13) was determined as the target bacteria of biocontrol bacteria. Finally, the colony numbered Pb-13 was selected as the biocontrol bacteria for subsequent research.

[0026] Example 2: Purification and identification of strain Pb-13 Isolate and purify strain 13 by streaking on LB agar plates. Pick a single colony and streak it on LB medium plates to obtain a single colony for classification and identification. Perform morphological analysis of the strain according to the "Bacteria Identification Manual." The method is as follows: A single colony was picked with a sterile toothpick and gently tapped on the bottom of a PCR tube. This colony was then attached to the bottom of the tube and used as a template for PCR amplification. The primers for 16sDNA fragments used for bacterial molecular identification were 27F: 5'-AGAGTTTGATCCTGGCTCAG-3' and 1492R: 5'-GGTTACCTTGTTACGACTT-3'. The PCR amplification reaction system consisted of 50 μL of 25 μL ExTaq MIX enzyme, 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, with termination at 72°C for 10 min. The amplified product was separated and identified by 1% agarose gel electrophoresis. The PCR amplified fragment was purified and directly sequenced in both directions. The resulting sequence was then submitted for Blast comparison at the NCBI website.

[0027] Test results: see Figure 2 The obtained Pb-13 strain was cultured on LB medium plates at 28°C for 3 days, and the colonies were glossy, with rounded convexities, a smooth, moist surface, and neat edges. Bacterial staining revealed that individual bacteria were rod-shaped, 0.8 × 1.0–2.0 μm in size. They had a thin capsule and a single flagellum, and Gram staining was negative (G-). Morphological analysis of strain 13 was performed according to the "Bacterial Identification Manual," and the strain was identified as Pseudomonas campestris ( Pseudomonas brassicacearum ), officially preserved as Pb-13.

[0028] The 16S rDNA region of the Pb-13 strain was amplified using universal 16sDNA primers 27F and 1492R. The PCR product was electrophoresed on a 1% agarose gel. Sequencing analysis revealed that the amplified 16S rDNA sequence was 1540 bp long (SEQ ID NO. 1). BLAST analysis of the 16S rDNA fragment sequence of the strain showed that the Pb-13 strain was similar to Pseudomonas campestris ( Pseudomonas brassicacearum ) bacteria similarity reached 100%. Identification of the strain Pseudomonas campestris ( Pseudomonas brassicacearum ).

[0029] Example 3: Analysis of the inhibitory effect of Pseudomonas campestris Pb-13 strain 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 Pseudomonas campestris Pb-13 against Fusarium solani.

[0031] (1) Preparation of Pb-13 strain fermentation broth The Pseudomonas campestris Pb-13 strain was streaked on an LB medium plate and cultured at 28°C for 3 days. The activated bacteria were scraped with an inoculation loop and inoculated into a 250 mL Erlenmeyer flask containing 100 mL LB liquid medium. The culture was shaken at 28°C (200 rpm) for 3 days. When the absorbance of the fermentation liquid reached OD 600 When the concentration reached 2.0, 20 μl was pipetted and used in a culture dish for a confrontation culture test to analyze the inhibitory effect of the bacteria on Fusarium solani.

[0032] (2) Preparation of 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 workbench. The plate was then inoculated onto a PDA plate and incubated at 28°C in the dark for three days. A sterile borer was used to extract a 3 mm diameter cake from the Fusarium solani colony for a counterculture test to determine the inhibitory effect of Pseudomonas campestris Pb-13 against Fusarium solani.

[0033] (3) Test method PDA culture dishes were used for counter-culture and analysis of the antibacterial effect. A root rot fungus cake was inoculated in the center of the dish. Two drops of biocontrol bacteria solution (20 μL per drop) were then inoculated from both sides of the 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. In the experiment, water was used instead of the solution as a control. After 3 days, the growth of the root rot fungus colony was observed. The diameter of the colony in the counter-culture was the shortest distance between the two inhibition lines. The root rot fungus colony diameter was statistically analyzed and compared with the diameter of the control colony to determine the inhibitory effect of the root rot fungus. The calculation formula is shown below. Five culture dishes were used for each treatment, and the experiment was repeated three times independently.

[0034] ① Calculation formula for antibacterial rate: Inhibition rate (%) = (diameter of control root rot fungus - diameter of opposing root rot fungus) / diameter of control root rot fungus × 100 The results showed that at 3 days, the Pseudomonas rapeseed Pb-13 strain showed a significant inhibitory effect on root rot fungi. In the water control, the diameter of the root rot fungi colony reached 6.5 cm, while in the Pb-13 strain treatment, the root rot fungi colony diameter was only 2.9 cm ( Figure 3 ). Through calculation, the inhibition rate of Pb-13 strain against root rot bacteria reached 65.1%.

[0035] Example 4: Effect of Pseudomonas rapeseed Pb-13 strain on root rot in potted plants (1) Preparation of Pb-13 bacterial culture The Pseudomonas campestris Pb-13 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 absorbance value of the fermentation liquid was OD 600 When the concentration of Pb-13 strain reaches 2.0 (the concentration of Pb-13 strain is 2×10 7 cfu / mL) were used in pot experiments to analyze the inhibitory effect of the fungus on Fusarium solani.

[0036] (2) Preparation of 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 bacterial clumps from the culture storage tube using an inoculating needle. These clumps were inoculated onto PDA plates 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 clumps, mycelium, and impurities were then filtered through sterile gauze to remove them. Spores of F. solani were collected from the filtrate, and the spore concentration was adjusted to 1 × 10 spores with sterile water. 7 cfu / ml, used for pot inoculation test.

[0037] (3) 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 placed on moistened sterile filter paper, spread flat in a Petri dish, and placed in a 30°C incubator for germination. When the seeds had just sprouted and developed radicles, the germinated tomato seeds were sown in seedling trays containing a sterilized mixture of 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 4 groups, and the following treatments were performed: healthy plants + sterile water (A), healthy plants + LB liquid culture medium (B), healthy plants + Fusarium solani (C), and healthy plants + Pb-13 + Fusarium solani (D). During the treatment, the biocontrol bacteria Pb-13 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 the root rot pathogen Fusarium solani by root immersion. The tomato roots of groups C and D were immersed in the Fusarium solani spore suspension (10 7 cfu / ml) for 15 minutes and then cultured in a greenhouse at 25 ± 2°C. Each treatment group consisted of 10 plants, with three replicates. Sterile water (Group A) and LB liquid medium (Group B) served as negative controls, while plants inoculated only with the pathogen Fusarium solani (Group C) served as a positive control. After treatment with Fusarium solani, the plants were replanted in their original pots. Fifteen days after inoculation with the biocontrol agent, the aboveground and underground disease conditions were observed. Fresh weight, plant height, and disease severity were statistically analyzed, and the incidence rate, disease index, and relative control efficacy were calculated.

[0039] The calculation of disease grade, incidence rate, disease index and relative efficacy is as follows (Table 1): Table 1 Tomato root rot disease survey and 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. ① Incidence calculation formula: Incidence rate (%) = (number of diseased plants / number of surveyed plants) × 100 ②Calculation formula for disease index: 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 ③ Relative prevention effect calculation formula: Relative control efficacy (%) = (control disease index - treatment disease index) / control disease index × 100 (5) Test results Experiments revealed that the aboveground parts of tomatoes treated with the Pb-13 strain grew significantly more vigorously than those inoculated only with Fusarium solani, with dark green leaves and robust plants. In contrast, treatment with Fusarium solani resulted in yellowing leaves and wilting. Testing showed that treatment with the Pseudomonas strain Pb-13 reduced the incidence of tomato root rot by 50% and the disease index by 45.3, achieving a relative control efficacy of 72.5% (Table 2). These results demonstrate that the Pb-13 strain has a significant inhibitory effect on Fusarium solani in tomatoes and holds significant potential for application in agricultural production.

[0040] At the same time, the plant height and fresh weight were detected (Table 3, Figure 4 ), the results showed that the average fresh weight of tomato plants treated with Pb-13 strain was 4.1g / plant and the average plant height was 24.0cm / plant, while the average fresh weight of the positive control treated with root rot fungi was 1.9g / plant and the average plant height was 19.5cm / plant. Compared with the sterile water control, the plant height and fresh weight of Pb-13 strain treatment increased by 5.3% and the fresh weight increased by 51.7%, which can significantly promote growth, while the root rot fungus treatment inhibited the growth of tomatoes.

[0041] Table 2 Disease index and control effect of different treatments deal with Incidence (%) Disease Index Relative prevention effect (%) Sterile water control 0 0 - LB control 0 0 - Root rot treatment 100% 62.5 - Treatment of Pb-13 with Shengfang fungus 50% 17.2 72.5% Table 3 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 22.8 2.7 - - LB medium treatment 23.3 2.5 102.3% 94.0% Root rot treatment 19.5 1.9 85.5% 72.1% Pb-13 treatment 24.0 4.1 105.3% 151.7% The above is a detailed introduction to a Pseudomonas rapeseed Pb-13 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 Pseudomonas campestris Pb-13 strain ( Pseudomonas brassicacearum ), characterized in that Its taxonomic name is Pseudomonas campestris Pseudomonas brassicacearum , deposited in the General Microbiology Center of China Culture Collection Administration of Microorganisms, with the deposit number CGMCC NO.33643.

2. The method for preparing the fermentation broth of Pseudomonas campestris Pb-13 strain according to claim 1, characterized in that: The Pb-13 strain was inoculated into LB culture medium for fermentation to obtain the fermentation broth.

3. The preparation method 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 of the Pb-13 strain according to claim 2 or 3.

5. The microbial agent according to claim 4, characterized in that The concentration of Pb-13 strain in the fermentation broth is ≥2×10 7 cfu / mL.

6. Use of the strain according to claim 1, the fermentation broth prepared by the preparation method according to claim 2 or 3, and the microbial agent according to claim 4 or 5 in controlling Fusarium solani.

7. Use of the strain according to claim 1, the fermentation liquid prepared by the preparation method according to claim 2 or 3, and 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 prepared by the preparation method 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 is as follows: soaking the roots of the tomato seedlings in a solution containing the fermentation liquid or microbial agent.

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