A Strain of Halophilic Bacillus B13 and Its Application

Abstract

The present invention discloses a strain of Bacillus halotolerans B13 and its application; the strain has been deposited in the General Microbiology Center of China Microorganism Culture Collection Administration Committee on December 26, 2022, and the biological deposit number is: CGMCC NO.26273. The strain provided by the present invention has an inhibitory effect on the pathogenic bacteria of sweet potato black spot disease, and can also promote the growth of sweet potatoes, increase the enzyme activity of defense enzymes in sweet potato leaves, and increase the enzyme activity of sweet potato rhizosphere soil enzymes. At the same time, the biological control agent with the strain as the active ingredient is low in cost, pollution-free, and has good control effect. It is the best substitute for chemical fertilizers and pesticides frequently used in the prevention and control of sweet potato black spot disease; it has guiding significance for increasing sweet potato yield, so the halotolerans B13 of the present invention has good application potential.

Description

Technical Field

[0001] The invention relates to the technical field of microorganisms, in particular to a halotolerant Bacillus B13 and application thereof. Background Art

[0002] Sweet potato is one of the four major economic crops in my country, and its production in my country ranks first in the world. As a common crop among my country's grain varieties, sweet potato has strong drought and cold resistance characteristics, and can grow in large quantities in areas with warmer climates. Sweet potato is rich in starch, vitamins, dietary fiber, minerals and other nutrients, and also has rich nutrients, such as carotene, vitamin B1, B2, C and iron, calcium and other minerals. The content is higher than rice and wheat flour, and it has special health care effects and high nutritional value. It can nourish the mind, replenish the spleen and replenish qi, effectively prevent and treat daily diseases, and can also be used as the main raw material for my country's industrial production, contributing to the improvement of the overall level of my country's industrial development.

[0003] Sweet potato black spot disease is also known as black scar disease, commonly known as lamp head scar, dry rot, black foot, black plaster, etc. It is a fungal disease caused by the infection of sweet potato long beaked shell fungus of the Ascomycetes class of the Pyrocomycetes order. The pathogen mainly overwinters in the diseased potatoes and the soil of the field or seedbed, as well as in manure and storage pits in the form of thick-walled spores and ascospores, becoming the main source of initial infection. The disease can cause huge losses in production. Generally, the yield of the diseased fields is reduced by 20% to 30%, and the yield of the seriously diseased fields is 70% to 80%. Some seriously diseased fields may even have no harvest. The diseased potatoes also contain toxins, which can cause poisoning when eaten by humans and animals.

[0004] Halophilic Bacillus is a species in the genus Bacillus. It has been reported that halophilic Bacillus can inhibit a variety of plant pathogenic fungi. Patent CN111979149A discloses a halophilic Bacillus SY1836, which has a good control effect on pepper blight and can significantly increase the plant height and fresh weight of pepper during growth. However, so far, there are few reports on the use of halophilic Bacillus to control sweet potato black spot. For example, "Study on the Biological Control Effect of Bacillus amyloliquefaciens Strain XZ-1 on Sweet Potato Black Spot" (Yang Dongjing et al., Journal of Southwest Agriculture, Vol. 31, No. 4, 2018) shows that although the Bacillus amyloliquefaciens strain XZ-1 screened from the rhizosphere soil of sweet potato is used to control sweet potato black spot, microscopic observation of mycelium morphology has not found that the strain has a significant inhibitory effect on the mycelium of the black spot pathogen, and the strain has a great influence on the spore production type of the black spot pathogen. The use of traditional chemical pesticides has a great impact on the environment, and the residual pesticides are also harmful to the human body. It is particularly important to find new biological control products. The excellent microbial resources in the rhizosphere of plants can provide a good material basis for the manufacture of biological control products. Therefore, screening biological control strains that can prevent and treat sweet potato black spot disease has a very important application value. Summary of the invention

[0005] The present invention aims at the deficiencies of the prior art and provides a salt-tolerant Bacillus B13 and its application. The salt-tolerant Bacillus B13 screened out by the present invention has a good inhibitory effect on the pathogen of sweet potato black spot disease, and can promote the growth and development of sweet potatoes, providing a strong guarantee for the production of sweet potatoes.

[0006] The present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a salt-tolerant Bacillus B13, whose biological preservation number is: CGMCCNO.26273, and it was deposited in the General Microbiology Center of China National Microbiological Culture Collection Administration on December 26, 2022.

[0008] The salt-tolerant Bacillus B13 was isolated from the rhizosphere soil of sweet potatoes. The colony and bacterial characteristics of the strain are as follows: after culturing on the LB plate for 24 hours, the colony is approximately round, beige and opaque, with irregular edges, dry and rough surface, and the colony diameter is 4.12 mm. The bacterial body is long rod-shaped, produces spores, and is Gram-positive.

[0009] The physiological and biochemical characteristics of the halotolerant Bacillus B13 are: negative in VP test, positive in starch hydrolysis test, positive in sorbitol fermentation test, positive in glucose fermentation test, negative in raffinose fermentation test, negative in arabinose fermentation test, negative in xylose fermentation test, and positive in mannitol fermentation test.

[0010] The molecular biological characteristics of the halotolerant Bacillus B13 are:

[0011] The 16S rDNA sequence of the strain is shown in SEQ ID NO.1.

[0012] The second aspect of the present invention provides a biological control agent, which uses Bacillus halodolerans B13 as an active ingredient.

[0013] Preferably, the biological control agent is a liquid agent, and the content of Bacillus halophilus (Bacillus halophilus) B13 is greater than or equal to 1×10 8 cfu / mL.

[0014] The third aspect of the present invention provides a method for preparing a biological control agent, comprising the following steps:

[0015] (1) inoculating the salt-tolerant Bacillus B13 into a liquid LB medium to obtain an activated bacterial solution;

[0016] (2) The activated bacterial solution was inoculated into liquid LB medium for fermentation to obtain a fermentation solution, and the fermentation solution was diluted with sterile water until the content of halotolerant Bacillus B13 was greater than or equal to 1×10 8 cfu / mL, and obtain the biological control agent.

[0017] Preferably, in step (1), the culturing is carried out at 37° C. in a constant temperature shaker for 12 h at a rotation speed of 180 rpm.

[0018] Preferably, in step (2), the inoculation amount of the activated bacterial solution is 1 vt%; and the fermentation is carried out by culturing in a shaker at 37° C. for 24 hours at a rotation speed of 180 rpm.

[0019] Preferably, the composition of the liquid LB medium is: yeast extract, 5 g; peptone, 10 g; sodium chloride, 10 g; distilled water, 1000 ml; agar, 15-20 g; sterilization at 121° C. for 20 min; pH 7.0.

[0020] In a fourth aspect of the present invention, there is provided a use of Bacillus halotolerans B13 or a biological control agent in at least one of the following 1) to 5):

[0021] (1) Inhibit the pathogen of sweet potato black spot;

[0022] (2) preparing products for preventing and treating sweet potato black spot pathogens;

[0023] (3) Promote sweet potato growth;

[0024] (4) Increase the activity of defense enzymes in sweet potato leaves;

[0025] (5) Improve the enzyme activity of sweet potato rhizosphere soil enzymes.

[0026] Preferably, the sweet potato black spot pathogen is Ceratocystis fimbriata.

[0027] Preferably, the defense enzymes include peroxidase, catalase, and superoxide dismutase.

[0028] Preferably, the sweet potato rhizosphere soil enzymes include sucrase, catalase, phosphatase and urease.

[0029] The beneficial effects of the present invention are:

[0030] 1. The present invention isolates a salt-tolerant Bacillus halotolerans B13 from the rhizosphere soil of sweet potatoes, and the strain has the functions of preventing and treating sweet potato black spot, promoting sweet potato growth, enhancing plant defense enzyme activity, and improving soil enzyme activity. Therefore, the strain has a good basis for preparing microbial agents and has good application value.

[0031] 2. The preparation method of the microbial agent of the present invention is simple, short in cycle, low in cost and pollution-free. It can be used to replace traditional chemical pesticide products used to prevent and treat sweet potato black spot disease, and has important guiding significance for sweet potato production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : Plate colony morphology of strain B13;

[0033] Figure 2 :Microscopic examination of strain B13;

[0034] Figure 3 : Phylogenetic tree of strain B13;

[0035] Figure 4 :Antagonistic effect diagram of strain B13 against sweet potato black spot pathogen;

[0036] Figure 5 : The growth value of the main vine of sweet potato after applying the fungus for 60 days;

[0037] Figure 6 : The growth value of sweet potato stem diameter after 60 days of application of bacterial agent;

[0038] Figure 7 :Peroxidase activity in sweet potato leaves after 60 days of bacterial inoculant application;

[0039] Figure 8 : Catalase activity in sweet potato leaves after 60 days of bacterial inoculant application;

[0040] Fig. 9 :Superoxide dismutase activity in sweet potato leaves after 60 days of bacterial inoculant application;

[0041] Fig.10 : Fresh weight of sweet potato above ground 120 days after application of fungicide;

[0042] Fig.11 : Aboveground dry weight of sweet potato 120 days after application of bacterial agent;

[0043] Fig.12 : Fresh weight of sweet potato tubers after 120 days of bacterial inoculant application;

[0044] Fig.13 : Dry weight of sweet potato root tubers after 120 days of application of bacterial agent;

[0045] Fig.14: Sweet potato yield after 120 days of bacterial inoculant application;

[0046] Fig.15 : Sucrase activity in rhizosphere soil of sweet potato after 120 days of bacterial inoculant application;

[0047] Fig.16 : Catalase activity in rhizosphere soil of sweet potato after 120 days of bacterial inoculant application;

[0048] Fig.17 : Phosphatase activity in rhizosphere soil of sweet potato after 120 days of bacterial inoculant application;

[0049] Fig.18 : Urease activity in rhizosphere soil of sweet potato 120 days after application of bacterial agent. DETAILED DESCRIPTION

[0050] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0051] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific examples. If the specific experimental conditions are not specified in the examples, they are usually in accordance with conventional conditions or the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following examples, unless otherwise specified, can be obtained through commercial channels.

[0052] Example 1: Isolation and identification of strains

[0053] 1. Strain Isolation and Screening

[0054] 1.1 Strain Isolation

[0055] Soil samples were collected from the sweet potato planting base in Sishui County, Jining City, Shandong Province. The collected sweet potato rhizosphere soil was immediately processed: 90 mL of sterile water was added to every 10 g of soil in a pre-prepared triangular bottle filled with glass beads, and the soil suspension was placed on a 37°C constant temperature shaker and shaken at 180 r / min for 20-30 min to obtain a soil suspension. The soil suspension was gradiently diluted to 10 -2 g / mL, 10 -3 g / mL, 10 -4 g / mL, 10 -5 g / mL, 10 -6 g / mL and other concentration gradients. -4 , 10 -5 , 10 -6100 μL of soil suspensions of three concentration gradients were placed in LB plate medium and spread evenly. Cultured in a 37°C constant temperature incubator for 24 hours, and single colonies were picked. The obtained strains were purified using the three-zone line method until a single colony was obtained, and the strains were numbered and stored in a 4°C refrigerator for later use.

[0056] 1.2 Screening of antagonistic bacteria

[0057] Antagonistic bacteria were screened using the plate confrontation method: the sweet potato black spot pathogen stored on the slant was activated on the PDA plate by streaking, and cultured at 28°C until the plate was full. The sweet potato black spot pathogen Ceratocystis fimbriata was made into a round bacterial cake using a sterilized hole puncher, transferred to the middle part of the PDA plate with tweezers, and placed in a 28°C incubator for 3 days. The activated antagonistic bacteria were picked with a toothpick and inoculated 2 cm away from the edge of the pathogen, placed in a 28°C incubator for 5 days, and observed whether an antibacterial zone appeared and measured the width of the antibacterial zone. At the same time, the antibacterial diameter was measured and the antibacterial rate was calculated.

[0058] Inhibition rate (%) = (colony diameter D-inhibition diameter d) / colony diameter D×100%

[0059] A strain B13 with the best antibacterial effect was selected, and the results of its plate confrontation test are shown in Table 1 and Figure 4 .

[0060] Table 1: Flat plate confrontation test results

[0061]

[0062] It can be seen from Table 1 that strain B13 has a good antibacterial effect on the pathogen of sweet potato black spot.

[0063] 2 Determination of morphological and physiological and biochemical characteristics of strain B13

[0064] 2.1 Colony characteristics and bacterial morphology

[0065] After culturing on LB medium at 37°C for 24 hours, the surface of the colony was dry, opaque, beige, with irregular or nearly circular edges. Microscopic observation showed that the bacterial morphology was rod-shaped, single-celled, Gram-positive, and had spores.

[0066] 2.2 Physiological and biochemical characteristics

[0067] The strain B13 VP test was negative, the starch hydrolysis test was positive, the sorbitol fermentation test was positive, the glucose fermentation test was positive, the raffinose fermentation test was negative, the arabinose fermentation test was negative, the xylose fermentation test was negative, and the mannitol fermentation test was positive.

[0068] 2.3 Molecular biological identification of strain B13

[0069] The 16S rDNA gene sequence of strain B13 is shown in SEQ ID NO. 1 in the nucleotide sequence table. The 16S rDNA sequence was compared by BLAST, and combined with the morphology, culture characteristics and physiological and biochemical analysis results of the strain, strain B13 was preliminarily identified as Bacillus halotolerans.

[0070] The strain B13, classified and named Bacillus halotolerans B13, was deposited in the General Microbiology Center of China Culture Collection (CGMCC for short, address: No. 3, Building 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences) on December 26, 2022, and the strain deposit number is CGMCCNO.26273.

[0071] Example 2: Preparation of strain B13 inoculant

[0072] Transfer the salt-tolerant Bacillus B13 stored on the plate to a test tube containing 10 mL of liquid LB medium and culture it in a constant temperature shaker for 12 hours (temperature: 37°C; speed: 180 rpm). Inoculate the activated bacterial solution with a 1% (volume percentage) inoculation amount into 200 mL of liquid LB medium and culture it in a shaker for 24 hours (temperature: 37°C; speed: 180 rpm) to obtain the fermentation liquid of the B13 strain; when used as a biocontrol agent, dilute the fermentation liquid with an appropriate amount of sterile water to 1×10 8 cfu / mL is sufficient.

[0073] Embodiment 3:

[0074] 1. Potted experiment design

[0075] The experiment was carried out in a potted planting method with a natural soil and substrate ratio of 1:1. Healthy and uniformly growing sweet potato seedlings were selected for use. The sweet potato seedlings were treated by root irrigation. The method was as follows: after transplanting, when the seedlings grew stably, 2 g of black spot fungus hyphae cultured in liquid culture was buried near the roots of the sweet potatoes. After 10 days, 3 seedlings (1 seedling / pot) were treated with the B13 bacterial agent prepared in Example 2. Each seedling was applied with 100 mL of a diluted solution of the bacterial fermentation liquid at a concentration of about 10 8 cfu / mL, watered around the root system and managed normally; the chemical pesticide control was 100mL of 1600-fold diluted carbendazim, and the blank control was 100mL of clean water.

[0076] 2. Determination and analysis of sweet potatoes and potted soil in potted experiments:

[0077] 2.1. Prevention and control effects

[0078] The incidence and control effect of sweet potato black spot disease were calculated 120 days after the sweet potatoes were harvested after the application of the fungicide. The evaluation method was:

[0079] Level 0: The surface of the tuber is smooth and has no disease spots;

[0080] Level 1: There are 1 to 2 lesions on the tuber, the diameter of the lesions is less than 0.5 cm, and the lesions are not sunken;

[0081] Level 2: There are 3 to 5 lesions, which occupy 1 / 4 to 1 / 3 of the potato skin surface area, with a diameter of 0.5 to 1.0 cm. The lesions are sunken and do not infect the potato flesh.

[0082] Level 3: There are more than 5 lesions or the diameter of the lesions is less than 1.0 cm, accounting for 1 / 3 to 1 / 2 of the surface area of ​​the potato skin, the lesions are sunken, and the potato flesh is infected;

[0083] Level 4: Severe disease, infecting the potato flesh, with lesions exceeding 1 / 2 of the potato skin surface area.

[0084] The calculation formula is as follows:

[0085] Incidence rate (%) = (number of diseased potatoes / total number of surveyed potatoes) × 100%

[0086] Disease index (%) = (number of diseased potatoes × disease level / total number of investigated potatoes × highest disease level) × 100%

[0087] Control effect (%) = [(control disease index - treatment disease index) / control disease index] × 100%

[0088] 2.2 Agronomic traits and yield of sweet potato

[0089] Agronomic traits of sweet potatoes: The main vine length, stem thickness, fresh weight and dry weight of sweet potatoes were measured;

[0090] Sweet potato tuber yield per plant: The weight of tubers in each treatment group was weighed.

[0091] 2.3 Sweet potato leaf defense enzymes

[0092] Sweet potato leaf enzyme activities: superoxide dismutase (SOD) and peroxidase (POD) were determined by referring to the “Principles and Techniques of Plant Physiology and Biochemistry Experiments” edited by Li Hesheng; catalase (CAT) activity was determined by referring to the “Plant Physiology Experiment Guide” edited by Zhang Zhiliang.

[0093] 2.4 Enzyme activities in sweet potato rhizosphere soil

[0094] Sweet potato soil enzyme activity: sucrase activity was measured by 3,5-dinitrofl colorimetric method, urease activity was measured by indophenol colorimetric method, phosphatase activity was measured by disodium phenyl phosphate colorimetric method, and catalase activity was measured by potassium permanganate titration method.

[0095] 2.5 Data Analysis

[0096] GraphPad Prism 9 and Excel 2021 were used to organize, analyze and plot data.

[0097] 3. Results and Analysis

[0098] 3.1B13 fungicide control effect on sweet potato black spot

[0099] The results of strain B13 on the control of sweet potato black spot are shown in Table 2

[0100] Table 2 Incidence and control effect of sweet potato black spot

[0101] deal with Incidence Control effect Shimizu 80％ — Carbendazim 1600 times dilution 70％ 52.35％ B13 50％ 84.38％

[0102] As shown in Table 2, the treatment group with B13 bacterial agent can reduce the incidence of sweet potato black spot disease, has a good prevention and control effect, and has a high application potential.

[0103] 3.2 Agronomic traits

[0104] 3.2.1 Main vine length growth value

[0105] The growth value of the main vine of sweet potato after 60 days of application of the fungus is as follows Figure 5 As shown, the B13 treatment group increased by 70.43% compared with the control group and increased by 48.54% compared with the carbendazim treatment group, both reaching the significant difference level (P<0.05).

[0106] 3.2.2 Stem diameter growth value

[0107] The growth value of sweet potato stem thickness after 60 days of application of fungicide is as follows Figure 6 As shown, the B13 treatment group increased by 128.85% compared with the control group and increased by 85.41% compared with the carbendazim treatment group, both reaching a significant difference level (P<0.05).

[0108] 3.2.3 Fresh weight above ground

[0109] The aboveground fresh weight of sweet potatoes after 120 days of application of the fungicide is as follows Fig.10 As shown, the B13 treatment group increased by 15.44% compared with the control group, reaching a significant difference level (P<0.05).

[0110] 3.2.4 Dry weight above ground

[0111] The aboveground dry weight of sweet potatoes after 120 days of application of the fungicide is as follows Fig.11 As shown, the B13 treatment group increased by 20.79% compared with the control group, reaching a significant difference level (P<0.05).

[0112] 3.2.5 Fresh weight of root tubers

[0113] Fresh weight of sweet potato tubers after 120 days of bacterial inoculant application Fig.12 As shown, the B13-treated group increased by 69% compared with the control group, reaching a significant difference level (P<0.05).

[0114] 3.2.6 Root dry weight

[0115] The dry weight of sweet potato root tubers after 120 days of application of the fungicide is as follows Fig.13 As shown, the B13 treatment group increased by 33.44% compared with the control group, reaching a significant difference level (P<0.05).

[0116] 3.2.7 Sweet potato production

[0117] The yield of sweet potato after applying the fungus for 120 days is as follows Fig.14 As shown, the B13 treatment group increased by 53.50% compared with the control group, reaching a significant difference level (P<0.05).

[0118] In summary, the application of B13 bacterial agent can significantly improve the agronomic traits and yield of sweet potatoes.

[0119] 3.3 Defensive enzyme activity in sweet potato leaves

[0120] Since carbendazim has no effect on increasing enzyme activity, the enzyme activity tests of 3.3 to 3.4 were only treated with an equal amount of clean water as a control.

[0121] 3.3.1 Peroxidase

[0122] Peroxidase activity in sweet potato leaves after 60 days of bacterial inoculant application Figure 7 As shown, the B13 treatment group increased by 70.45% compared with the control group, reaching a significant difference level (P<0.05).

[0123] 3.3.2 Catalase

[0124] Catalase activity in sweet potato leaves after 60 days of bacterial inoculant application Figure 8 As shown, the B13 treatment group increased by 18.52% compared with the control group, reaching a significant difference level (P<0.05).

[0125] 3.3.3 Superoxide dismutase

[0126] The superoxide dismutase activity of sweet potato leaves after 60 days of application of the fungicide is as follows Fig. 9 As shown, the B13 treatment group increased by 8.21% compared with the control group, reaching a significant difference level (P<0.05).

[0127] In summary, applying B13 for 60 days can induce the enhancement of the activity of sweet potato defense enzymes, thereby improving the stress resistance of sweet potatoes.

[0128] 3.4 Enzyme activities in sweet potato rhizosphere soil

[0129] 3.4.1 Sucrase

[0130] The activity of sucrase in the rhizosphere soil of sweet potato after applying the bacterial agent for 120 days Fig.15 As shown, the B13 treatment group increased by 24.02% compared with the control group, reaching a significant difference level (P<0.05).

[0131] 3.4.2 Catalase

[0132] Catalase activity in sweet potato rhizosphere soil after 120 days of bacterial inoculant application Fig.16 As shown, the B13 treatment group increased by 6.03% compared with the control group, which did not reach the significant difference level (P<0.05).

[0133] 3.4.3 Phosphatases

[0134] Phosphatase activity in sweet potato rhizosphere soil after 120 days of bacterial inoculant application Fig.17 As shown, the B13 treatment group increased by 25.20% compared with the control group, reaching a significant difference level (P<0.05).

[0135] 3.4.4 Urease

[0136] Urease activity in sweet potato rhizosphere soil after 120 days of bacterial inoculant application Fig.18 As shown, the B13 treatment group increased by 9.49% compared with the control group, reaching a significant difference level (P<0.05).

[0137] In summary, the application of B13 bacterial agent can significantly improve soil enzyme activity, thereby increasing nutrients in the soil, which has a positive effect on the growth of sweet potatoes.

[0138] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A strain of halotolerant Bacillus ( Bacillus halotolerans ) B13, characterized in that Its biological deposit number is: CGMCC NO.26273.

2. A biological control agent, characterized in that: The salt-tolerant Bacillus according to claim 1 ( Bacillus Halotolerans ) B13 is the active ingredient.

3. The biological control agent according to claim 2, characterized in that: The biological control agent is a liquid agent, wherein the salt-tolerant Bacillus ( Bacillus halotolerans )The content of B13 is greater than or equal to 1×10 8 cfu / mL.

4. The method for preparing the biological control agent according to claim 2 or 3, characterized in that: The following steps are involved: (1) Inoculating the salt-tolerant Bacillus sp. B13 into liquid LB medium to obtain an activated bacterial solution; (2) The activated bacterial solution was inoculated into liquid LB medium for fermentation to obtain a fermentation solution, and the fermentation solution was diluted with sterile water until the content of halotolerant Bacillus B13 was greater than or equal to 1×10 8 cfu / mL, and obtain the biological control agent.

5. The preparation method according to claim 4, characterized in that: In step (1), the culture is carried out at 37° C. in a constant temperature shaker for 12 h at a rotation speed of 180 rpm.

6. The preparation method according to claim 4, characterized in that: In step (2), the inoculation amount of the activated bacterial solution is 1vt%; and the fermentation is carried out by culturing in a shaker at 37°C for 24h at a rotation speed of 180rpm.

7. The halotolerant Bacillus according to claim 1 ( Bacillus halotolerans ) Use of the biological control agent described in B13 or claim 2 or 3 in at least one of the following 1) to 5): (1) Inhibit the pathogen of sweet potato black spot; (2) Preparation of products for controlling sweet potato black spot pathogens; (3) Promote the growth of sweet potatoes; (4) Improving the activity of defense enzymes in sweet potato leaves; the defense enzymes include peroxidase, catalase, and superoxide dismutase; (5) Improving the enzyme activity of sweet potato rhizosphere soil enzymes; the sweet potato rhizosphere soil enzymes include sucrase, catalase, phosphatase, and urease.

8. The use according to claim 7, characterized in that: The sweet potato black spot pathogen is Aspergillus niger ( Ceratocystis fimbriata ).

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