Bacillus altitudinis Baa-12 strain and application thereof

Abstract

The invention provides a bacillus altitudinis strain, the classification name of the bacillus altitudinis strain is bacillus altitudinis, the bacillus altitudinis strain is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number of the bacillus altitudinis strain is CGMCC NO.33641. The bacillus altitudinis strain provided by the invention is a bacillus altitudinis strain. According to the invention, the bacteriostatic effect of the Baa-12 strain on fusarium solani is detected through confrontation culture, and the result proves that the inhibitory effect of the strain on fusarium solani reaches 57.3%. 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 73.1%, and the strain has a remarkable growth promoting effect. The control effect is high and stable, and agricultural production requirements are met.

Description

Technical Field

[0001] The present invention relates to the technical field of microorganisms, and particularly relates to a Bacillus altitudinis Baa-12 strain and its application. Background Art

[0002] Tomato ( Solanum lycopersicum ) is a daily vegetable in most countries and regions of the world and occupies an important position in global vegetable production. As one of the world's three major tomato production areas, China's position and influence in the world's tomato production and trade have been significantly improved. China has also made remarkable achievements in tomato breeding. The newly bred varieties have significantly improved in terms of compound disease resistance and quality. In particular, significant breakthroughs have been made in pink fruit varieties, and self-developed varieties account for more than 85%, dominating the domestic market. China is a major producer of fresh and processed tomatoes. China ranks first in the world in fresh tomato production and second in processed tomato production.

[0003] With the increase in tomato planting area and the expansion of protected cultivation methods, tomato root rot has become increasingly serious and has become one of the major diseases commonly occurring in China. Fusarium solani ( Fusarium solani ) is one of the most destructive tomato soil-borne diseases causing tomato root rot. It mainly harms the roots and the base of the stem of the plant. Infected plants have rotten roots, grow poorly, and may even die completely when severely affected. The main pathogen of tomato root rot is Fusarium solani, which can quickly infect the roots and the base of the stem of tomatoes, destroying the absorption of nutrients and water, thus endangering the plant. Tomato root rot can occur throughout the growth period, and it occurs in both open-field cultivation and protected cultivation. When infected at the seedling stage, water-soaked lesions appear at the base of the stem or roots of the seedlings, the cortex turns brown and rots, the leaves turn yellow, and eventually wither and die. In the later stage of the disease, the pathogen spreads rapidly in the vascular bundles, forming ring-shaped brown lesions on the epidermis of the roots and stems. The vascular bundles and phloem tissues are damaged, inhibiting the absorption of water and nutrients, resulting in the death of the whole plant and causing a serious "dead plant" phenomenon. At this time, when the base of the stem or roots of the plant is longitudinally dissected, the xylem is brown and the roots of the plant are rotten. The dead plants caused by root rot are common in tomato production in China, especially highly prevalent in protected production, with an incidence rate of 30% - 60%. In severe cases, it can lead to the complete failure of tomato crops, and this disease has shown an outbreak trend in recent years. Effectively preventing and controlling the occurrence of tomato root rot has become an urgent problem to be solved in tomato production.

[0004] When the temperature is around 20 - 24°C, the occurrence of tomato neck rot and root rot is relatively severe, and it is even more significant in protected cultivation, indicating that lower soil temperature and higher soil humidity are suitable for the occurrence of tomato root rot. In addition, the pathogen can be spread through irrigation water and agricultural operations, and a humid environment is conducive to the pathogen invading from the wounds or natural orifices of the plant, harming the roots and stems of the plant until the entire root system rots and dies, causing serious damage.

[0005] In tomato production, techniques such as crop rotation, selection of resistant varieties, water and fertilizer management, biological control, and chemical control are all commonly used methods for preventing and controlling root rot. However, pathogens such as Fusarium have a wide range of hosts and can survive in the soil for a long time in various forms such as spores and hyphae. In recent years, with the adjustment of the agricultural industrial structure and the popularization of facility cultivation techniques such as greenhouse cultivation, the planting area of tomatoes in protected vegetables has been increasing. Due to the difficulty of crop rotation and the increase in the multiple cropping index of continuous cropping, root rot has caused serious continuous cropping obstacles and huge economic losses. Cultivating and utilizing disease-resistant varieties is the most economical and effective measure to control this disease, but the lack of resistant resources limits the cultivation and application of resistant varieties. Chemical control is still the main method for preventing and controlling root rot at present. Although it has advantages such as high control efficiency and fast speed, problems such as pesticide residues and the generation of pathogen resistance seriously affect the application of chemical control. Compared with traditional chemical agent control, the advantages of biological control technology using some beneficial microorganisms or microbial metabolites to effectively control crop diseases are gradually emerging. It has attracted the favor of researchers because of its advantages such as green safety, no drug resistance, no pollution to the environment, and friendly to humans and livestock. Summary of the Invention

[0006] To solve the above technical problems, the purpose of the present invention is to provide a Bacillus altitudinis Baa-12 strain and its application. The Bacillus altitudinis Baa-12 strain is derived from the rhizosphere soil of alpine meadows in Tibet. The preparation of the microbial agent is simple and efficient, and it has a good control effect on tomato root rot. Through experiments, it is proved that the isolated Bacillus altitudinis Baa-12 strain has a good control effect on root rot in indoor and pot experiments, which is of great significance for preventing and controlling the damage of tomato root rot and ensuring the safe production of vegetables such as tomatoes.

[0007] The technical solution adopted by the present invention is as follows: According to one aspect of the present application, the present application provides a Bacillus altitudinis Baa-12 strain ( Bacillus altitudinis ), whose taxonomic name is Bacillus altitudinis Bacillus altitudinis , and it is deposited in the General Microbiological Center of the China Committee for Culture Collection of Microorganisms, with the deposit number of CGMCC NO.33641.

[0008] The strain Baa-12 was deposited with the International Depository Authority for Microorganisms under the Budapest Treaty, the General Microbiology Center of the China Committee for Culture Collection of Microorganisms, at No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, with a postal code of 100101. The deposit date was February 24, 2025, and the deposit number was CGMCC NO. 33641. The optimal growth temperature of this strain is 28°C. The medium for strain isolation and purification is LB medium (10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 15 g of agar powder, made up to 1 L with sterile water). On the LB medium plate, after culturing at 28°C for 3 days, the colony morphology is round, white and opaque, with a smooth edge, protruding upwards, and slightly wrinkled. This bacterium is rod-shaped, arranged singly or in pairs, with a size of 0.3 - 1.0 μm × 2 - 5 μm, and the spore size is 0.6 - 0.9 μm × 1.0 - 1.5 μm. Observed by Gram staining, this bacterium is Gram-positive (G+). In liquid culture, the culture solution is turbid and has no pigment. According to the "Bacterial Identification Manual", the morphology of strain Baa-12 was determined, and this strain was identified as Bacillus altitudinis( Bacillus altitudinis ).

[0009] According to another aspect of the present application, the present application also provides the fermentation broth of the strain Baa-12, which is obtained by the following method: inoculating the strain Baa-12 into LB medium for fermentation culture to obtain the fermentation broth.

[0010] Specifically, the temperature of the fermentation culture is 25°C - 30°C, the rotation speed of the fermentation culture is 100 - 300 rpm, and the time of the fermentation culture is 2 - 5 d.

[0011] According to another aspect of the present application, the present application also provides a microbial inoculum, which contains the fermentation broth described in claims 2 - 3.

[0012] Specifically, the concentration of strain Baa-12 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 application of the strain, the fermentation broth, and the microbial inoculum in preventing and controlling Fusarium solani.

[0014] According to another aspect of the present application, the present application also provides the application of the strain, the fermentation broth, and the microbial inoculum in preventing and controlling 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, which is to apply the fermentation broth and the microbial inoculum to tomato seedlings.

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

[0017] The beneficial effects of the present invention include but are not limited to: 1. The Bacillus altitudinis Baa-12 strain of the present invention is a bacterium isolated from the rhizosphere soil of alpine meadows, which is safe and harmless to crops and has a control effect on root rot caused by Fusarium solani, showing safety characteristics in agricultural applications.

[0018] 2. The present invention detected the antibacterial effect of the Baa-12 strain against Fusarium solani through confrontation culture. The results confirmed that the inhibition effect of this strain on Fusarium solani reached 57.3%. In the pot experiment, the fermentation broth of this strain was used for root irrigation treatment, and the prevention and control effect on root rot caused by Fusarium solani reached 73.1%, showing a significant growth-promoting effect. The prevention and control effect is high and stable, meeting the requirements of agricultural production.

[0019] 3. The present invention first applied the Bacillus altitudinis Baa-12 strain to control tomato root rot caused by Fusarium solani, providing an important basis for its biocontrol application. Brief Description of the Drawings

[0020] Figure 1 For Figure 1 Schematic diagram of the confrontation culture between the biocontrol bacterium and the root rot fungus; 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 4 bacterial strains and their numbers for confrontation culture; Figure 2 For Figure 2 Colony and streaking morphology of the Bacillus altitudinis Baa-12 strain; A Front of the colony B Back of the colony; Figure 3 For the results of the confrontation culture between the Baa-12 strain and the root rot pathogen; A Colony morphology on the front of the confrontation treatment, B Colony morphology of the control; Figure 4 For the above-ground parts of tomatoes in different treatment groups; Figure 5 For the root and stem parts of tomatoes in different treatment groups. Detailed Description of the Invention

[0021] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments are only for the convenience of those skilled in the art to understand the technical solutions of the present invention and to implement or use the present invention, and do not limit the protection scope 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 embodiments are conventional methods in the art unless otherwise specified.

[0023] Example 1: Rapid isolation and screening of biocontrol bacteria Firstly, LB agar plates and PDA plates were prepared on a sterile workbench for bacterial isolation and confrontation tests respectively. The test media and their formulations are as follows: LB medium: 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 15 g of agar powder, and made up to 1 L with sterile water. After preparation, it was sterilized by high temperature and high pressure at 121 °C for 20 min, and then spread into plates in petri dishes for isolating and purifying bacteria. Liquid LB medium without agar was used for culturing the fermentation broth to make the microbial agent. When preparing the LB liquid medium, agar powder was deleted from the formula, and the preparation process was the same as before.

[0024] PDA medium: 200 g of potato, 20 g of glucose, 15 g of agar powder, made up to 1 L, pH = 7.0. When preparing, the potato was peeled, 200 g was weighed, cut into pieces, boiled for 15 min, filtered through gauze to remove potato pieces and residues, 20 g of glucose and 15 g of agar powder were added to the filtrate, sterilized by high temperature and high pressure at 121 °C for 20 min, and then spread into plates in petri dishes for analyzing the inhibitory effect of Bacillus altitudinis strain Baa - 12 on Fusarium solani.

[0025] Soil samples were evenly taken from meadow soil, a total of 3 portions, each taking 200 g, and mixed evenly; 50 g was taken from them and added to 1000 mL of distilled water, stirred evenly, allowed to stand for 3 min, 1 mL of the supernatant was taken, diluted 100 times with sterile water, and then 50 μL of the diluted liquid was spread on the LB agar plate. After the soil diluent was evenly spread, it was inverted and placed in an incubator at 28 °C for 2 d. After colonies grew on the plate, single colonies were picked with a sterile toothpick and streaked on the LB medium plate for isolation and purification to obtain purified single colonies for analyzing the confrontation culture effect. 30 - 50 single colonies were randomly picked with a sterile toothpick on each LB agar plate, and each colony was numbered starting from 1 in order. Single colonies were picked from 5 petri dishes in turn until the number reached 200. Each numbered single colony was streaked for culture, and then a sterile toothpick was used to pick the bacterial cells and stick them to 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 with shaking at 28 °C and 180 rpm for 2 days. Then 20 μl was taken from it and confronted with Fusarium solani on the PDA plate. Around the inoculation point of Fusarium solani in each petri dish, 4 isolated and purified bacterial strains were inoculated at equal distances respectively for rapid confrontation screening, as Figure 1 shown. During the screening, if the bacterial colony has an inhibitory effect on root rot, an antibacterial line will be formed against the root rot fungus colony. The margin of the antibacterial line is clear, and the farther the antibacterial line is from the bacterial colony, the more significant the inhibitory effect, which is used as the screening criterion.

[0026] Through confrontation culture, in the experiment of confrontation culture of 200 colonies at 3 days, 198 bacteria were strains without inhibitory effect, and the root rot pathogen could cover the bacterial colonies and continue to grow; while 2 bacterial strains had inhibitory effects and could form antibacterial lines, which were the strains numbered 12 and 106 respectively. The vertical distances of the antibacterial lines from the bacterial colonies were 0.7±0.1 cm and 0.2±0.1 cm respectively. According to the distance and morphology of the antibacterial line from the colony, the antibacterial line of strain No. 12 was obvious, and the distance from the bacterial colony was large (0.7 cm), and the effect was significantly higher than that of strain No. 106 (0.2 cm). Therefore, the bacterial strain numbered 12 was finally selected as the biocontrol bacterium for subsequent research.

[0027] Example 2: Purification and identification of biocontrol strain No. 12 Pick a single colony from the LB agar plate of strain No. 12, and further streak culture on the LB medium plate again to obtain a single colony. Observe the growth process and form of the colony, and conduct Gram staining analysis of the bacteria for classification and identification. Morphological determination and species identification of the strain are carried out according to the "Bacterial Identification Manual".

[0028] On the streak culture plate of strain No. 12, pick a single colony with a sterilized toothpick and gently touch the bottom in a PCR special tube to stick the bacteria of No. 12 to the bottom of the PCR tube as the PCR amplification template for bacterial PCR amplification. The 16sDNA fragment sequence of strain Baa-12 is determined by using the 16sDNA universal primers 27F: 5'-AGAGTTTGATCCTGGCTCAG-3' and 1492R: 5'-GGTTACCTTGTTACGACTT-3' in bacterial molecular identification for molecular identification and species analysis. The PCR amplification reaction system is 50 μL, containing 25 μL ExTaq enzyme MIX, 1 μL forward primer, 1 μL reverse primer, and 23 μL sterile water. Amplification conditions: pre-treatment at 94°C for 5 min; 94°C for 30S, 55°C for 30S, 72°C for 1 min, 30 cycles; termination of amplification at 72°C for 10 min. The amplification products are separated and identified by 1% agarose gel electrophoresis. The PCR products are directly sequenced bidirectionally, and Blast comparison analysis is carried out on the NCBI website to determine the species of strain No. 12.

[0029] The results are shown in Figure 2, After culturing the obtained strain No. 12 on an LB medium plate at 28 °C for 3 days, the colony morphology was round, white and opaque, with a smooth edge, protruding upward, and slightly wrinkled. The bacteria were rod-shaped, arranged singly or in pairs, with a size of 0.3 - 1.0 μm × 2 - 5 μm, and the spore size was 0.6 - 0.9 μm × 1.0 - 1.5 μm. Through Gram staining, the bacteria were observed to be Gram-positive (G+) under the microscope. In the LB liquid shake culture of strain No. 12, the culture broth was turbid and without pigment. According to the "Bacterial Identification Manual", the morphology of strain No. 12 was determined, and the strain was identified as Bacillus altitudinis ( Bacillus altitudinis ), and the official preservation number was designated as Baa-12.

[0030] The 16S rDNA region sequence of strain Baa-12 was amplified using the 16S universal primers 27F and 1492R, and a single band was obtained. The PCR product was separated and purified by 1% agarose gel electrophoresis. Sequencing analysis confirmed that the amplified 16S rDNA sequence of strain No. 12 was 1066 bp in length (SEQ ID NO.1). After performing a BLAST analysis on the 16S sequence of the strain, the results showed that the similarity between strain Baa-12 and Bacillus altitudinis ( Bacillus altitudinis ) reached 100%. Through molecular identification, the strain was identified as Bacillus altitudinis (Bacillus altitudinis ).

[0031] Example 3: Analysis of the inhibitory effect of Bacillus altitudinis Baa-12 strain on Fusarium solani Test media and their formulations: LB medium: 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, 15 g of agar powder, made up to 1 L with sterile water. After preparation, it was sterilized at 121 °C for 20 min under high temperature and high pressure, and then spread into plates in petri dishes for the isolation and purification of bacteria and culture. The liquid LB medium without agar was used for the culture of the fermentation broth.

[0032] PDA medium: 200 g of potato, 20 g of glucose, 15 g of agar powder, made up to 1 L, pH = 7.0. When preparing, the potato was peeled, 200 g was weighed, cut into pieces, boiled for 15 min, filtered through gauze to remove the potato pieces and residues, and 20 g of glucose and 15 g of agar powder were added to the filtrate. After sterilization at 121 °C for 20 min under high temperature and high pressure, it was spread into plates in petri dishes for the analysis of the inhibitory effect of Bacillus altitudinis Baa-12 strain on Fusarium solani.

[0033] (1) Preparation of the fermentation broth of strain Baa-12 The Bacillus altitudinis Baa-12 strain was streaked and activated 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 LB liquid medium, and cultured with shaking (200 rpm) at 28 °C for 3 days. When the absorbance value OD600 of the fermentation broth reached 2.0, 20 μl was pipetted for confrontation culture in a petri dish to analyze the inhibitory effect of this bacterium on Fusarium solani f. sp. cucurbitae.

[0034] (2) Preparation of the test bacterium Fusarium solani f. sp. cucurbitae Fusarium solani f. sp. cucurbitae was preserved by the Disease Group of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences. During the preparation, first, a bacterial block was picked with an inoculation needle from the bacterial strain preservation test tube on a sterile operating table and inoculated on a PDA plate, and cultured in the dark at 28 °C for 3 days. A 3-mm-diameter bacterial cake was taken with a sterilized borer on the Fusarium solani f. sp. cucurbitae colony for the confrontation culture test to determine the inhibitory effect of the Bacillus altitudinis Baa-12 strain on Fusarium solani f. sp. cucurbitae.

[0035] (3) Test method The PDA petri dish was used for confrontation culture to analyze the antibacterial effect. A bacterial block of root rot fungus was inoculated at the center of the petri dish, and then 2 drops (20 μL per drop) of the fermentation culture solution of the Baa-12 strain were inoculated at the center of the two sides of the bacterial cake to the edge of the petri dish respectively, and the bacterial solution was gently dropped to prevent the bacterial solution from flowing. Then it was cultured statically in the dark at 25 °C. In the test, clear water was set as the control. At 3 days, the growth of the root rot fungus colony was observed, the antibacterial line and the colony size were observed, and compared with the colony diameter of the control root rot fungus to determine the inhibitory effect of the Baa-12 strain on the root rot pathogen. The calculation formula is as shown in Equation 1. There were 5 petri dishes for each treatment, and the test was independently repeated 3 times.

[0036] The results showed that at 3 d, the Bacillus altitudinis Baa-12 strain showed a significant inhibitory effect on the root rot fungus. In the clear water control, the colony diameter of the root rot pathogen reached 7.5 ± 0.1 cm, while in the treatment with the Baa-12 strain, the colony of the root rot pathogen was only 3.2 ± 0.1 cm (Table 1). Through calculation, the inhibition rate of the Baa-12 strain on the root rot pathogen reached 57.3%.

[0037] Table 1 Experiment Confronting colony diameter cm Control colony diameter cm Replicate 1 3.14 7.64 Replicate 2 3.32 7.34 Replicate 3 3.24 7.56 Average 3.2±0.1 7.5±0.1 Inhibitory rate - 57.3% Example 4: Potted plant prevention and control effect of Bacillus altitudinis Baa-12 strain on tomato root rot (1) Preparation of the Baa-12 strain bacterial solution The Bacillus altitudinis strain Baa-12 was streaked and activated on an LB medium plate and cultured at 28 °C for 3 days. An inoculation loop was used to scrape the activated colonies and inoculate them into a triangular flask (250 mL) containing 100 mL of LB liquid medium, and cultured with shaking (200 rpm) at 28 °C for 3 days. When the absorbance OD 600 reached 2.0 (at this time, the concentration of strain Baa-12 was 2×10 7 cfu / mL), it was used for the pot control experiment to analyze the control effect of this bacterium on Fusarium solani.

[0038] (2) Preparation of the pathogen Fusarium solani Fusarium solani was preserved by the Disease Group of the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences. During preparation, first, a sterilized inoculation needle was used to pick up fungal blocks from the strain preservation tube on the sterile operating table and inoculate them on a PDA plate, and cultured in the dark at 28 °C for 3 days. Then, 5 fungal discs with a diameter of 3 mm were taken from the Fusarium solani colony using a sterilized borer and inoculated into PDA liquid medium, and cultured with shaking (200 rpm) at 28 °C for 5 days. Then, a sterilized gauze was used to filter out fungal blocks, mycelia and impurities, and the spores of Fusarium solani were collected in the filtrate, and the concentration of Fusarium solani spores was adjusted to 1×10 7 cfu / ml for the pot inoculation experiment.

[0039] (3) Preparation of tomato seedlings Tomato Moneymaker (Lycopersicon esculentum) seeds were soaked in 0.5% NaClO for 2 - 3 min, then rinsed several times with sterile water until there was no residual NaClO. The surface-sterilized seeds were spread out on a Petri dish with moist sterile filter paper and placed in an incubator at 30 °C for germination. When the seeds just germinated and radicles emerged, the germinated tomato seeds were sown into a seedling tray. The seedling substrate was a mixture of sterilized peat soil and vermiculite with a volume ratio of 2:1, and naturally grown in a greenhouse at 28 °C to obtain healthy tomato seedlings for subsequent experiments.

[0040] (4)Inoculation test Select tomato seedlings at the 3 - 4 leaf stage with consistent growth, divide them into 4 groups, and make the following treatments respectively: healthy plants + sterile water (A), healthy plants + LB liquid medium (B), healthy plants + Fusarium solani (C), healthy plants + Baa-12 + Fusarium solani (D). For the biocontrol treatment, the biocontrol bacterium Baa-12 was inoculated by the root irrigation method, and the dosage per pot (10 cm × 10 cm) was 20 ml of the fermentation broth, and cultured in a solar greenhouse at 28 ± 2 °C. Two days later, the tomato seedlings were gently separated from the soil, and the root rot pathogen was inoculated by the root immersion method. The tomato roots in groups C and D were immersed in the prepared Fusarium solani spore suspension (10 7Soak for 15 min in (cfu / ml), and culture in a solar greenhouse at 28 ± 2 °C. Groups A and B were used as controls and soaked in sterile water for mock inoculation treatment. Each treatment group had 10 plants, with 3 replicates. Sterile water (Group A) and LB liquid medium (Group B) were used as negative controls, and only inoculation with the pathogenic fungus Fusarium solani (Group C) was used as a positive control. The tomato seedlings treated with Fusarium solani were replanted into the original seedling pots. After inoculating with the biocontrol bacteria for 15 days, observe the disease occurrence in the above-ground and underground parts, statistically analyze the fresh weight, plant height, and disease level, and calculate the incidence rate, disease index, and relative control efficacy.

[0041] The calculation methods for disease level, incidence rate, disease index, and relative control efficacy are as follows: Table 2 Grading criteria for disease investigation of tomato root rot Disease level Root symptom description 0 No infection symptoms appeared on the rhizome 1 The diseased area accounted for less than 1 / 4 of the rhizome area, showing water-soaked brown spots, but no rot 2 The diseased area accounted for 1 / 4 - 1 / 2 of the rhizome area, the main root began to rot, the base of the stem began to show constriction, but new lateral roots grew, and there were no obvious symptoms above the ground 3 The diseased area accounted for 1 / 2 - 3 / 4 of the rhizome area, most of the main roots rotted, at the same time the base of the stem constricted, lateral roots no longer grew, and the leaves above the ground withered 4 The diseased area accounted for more than 3 / 4 of the rhizome area, the base of the stem constricted into a line, and the plant was almost dead ① Incidence rate calculation formula: Incidence rate (%) = (number of diseased plants / number of plants investigated) × 100 ② Disease index calculation formula: Disease index = [Σ (number of diseased plants × corresponding disease level) / (total number of plants × highest disease level)] × 100 In the formula: ∑ — The sum of the products of the values of each disease level and the number of plants at each disease level ③ Relative control efficacy calculation formula: Relative control efficacy (%) = (control disease index - treatment disease index) / control disease index × 100 (5)Test results It can be seen from the test that after treatment with the Baa-12 strain, the above-ground part of the tomato grew significantly more vigorously, with dark green leaves and strong plants. In the treatment with Fusarium solani, the plant leaves turned yellow, the plants were prone to wilting, and the incidence rate was 100%. After detection, after treatment with the Baa-12 strain, the incidence rate of tomato root rot decreased to 46.7%. At the same time, the disease index in the treatment with the biocontrol bacteria decreased significantly, only 21.7, and the relative control efficacy reached 73.1% (Table 3). The results show that the Baa-12 strain has a significant inhibitory effect on Fusarium solani of tomatoes and has important application potential in agricultural production.

[0042] At the same time, through the detection of plant height and fresh weight (Table 4, Figure 2 ), the results showed that the average fresh weight of tomato plants treated with the Baa-12 strain was 4.1 g / plant, and the average plant height was 24.0 cm / plant. The average fresh weight of the positive control treated with root rot fungus was 1.9 g / plant, and the average plant height was 19.5 cm / plant. Compared with the sterile water control, the Baa-12 strain could significantly promote growth in terms of plant height and fresh weight. The plant height increased by 8.0%, and the fresh weight increased by 70.8%.

[0043] Table 3 Disease index and control effect of different treatments Treatment Incidence rate (%) Disease index Relative control efficacy (%) Sterile water control 0 0 - LB medium control 0 0 - Root rot fungus treatment 100% 80.8 - Treatment with Bacillus altitudinis Baa-12 46.7% 21.7 73.1% Table 4 Fresh weight and plant height of tomatoes in different treatment groups Treatment Plant height cm Fresh weight g Plant height growth promotion rate (%) Fresh weight growth promotion rate (%) Sterile water control 22.5 2.4 - - LB medium control 22.4 2.5 - - Root rot fungus treatment 18.9 1.4 84.0% 58.3% Treatment with Baa-12 24.3 4.1 108.0% 170.8% The above has introduced in detail a Bacillus altitudinis Baa-12 strain and its application provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and optimizations can still be made to the present invention, and these improvements and optimizations also fall within the protection scope of the claims of the present invention.

Claims

1. Bacillus altitudinis strain Baa-12 ( Bacillus altitudinis ), characterized in that Its taxonomic name is Bacillus altitudinis Bacillus altitudinis , and it is deposited in the China General Microbiological Culture Collection Center with the deposit number of CGMCC NO. 33641.

2. The fermentation broth of the Baa-12 strain according to claim 1, characterized in that, The fermentation broth is obtained by the following method: inoculating the Baa-12 strain into an LB medium for fermentation culture to obtain the fermentation broth.

3. The fermentation broth of the Baa-12 strain according to claim 2, characterized in that, The temperature of the fermentation culture is 25°C to 30°C, the rotation speed of the fermentation culture is 100 to 300 rpm, and the time of the fermentation culture is 2 to 5 days.

4. A microbial inoculant, characterized in that, The microbial inoculum contains the fermentation broth described in claims 2 to 3.

5. The microbial inoculant according to claim 4, characterized in that, The concentration of strain Baa-12 in the fermentation broth is ≥ 2×10 7 cfu / mL.

6. Application of the strain described in claim 1, the fermentation broth described in claim 2 or 3, and the microbial inoculum described in claim 4 or 5 in controlling Fusarium solani.

7. Application of the strain described in claim 1, the fermentation broth described in claim 2 or 3, and the microbial inoculum described in claim 4 or 5 in controlling tomato root rot.

8. A method for preventing and controlling tomato root rot, characterized in that, Applying the fermentation broth described in claim 2 or 3 and the microbial inoculum described in claim 4 or 5 to tomato seedlings.

9. The method according to claim 8, wherein The application is: inoculating the inoculum at the roots of tomato seedlings by the method of root irrigation.

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