Antibacterial active substance and application thereof

Abstract

The invention belongs to the technical field of agricultural microorganisms, and relates to an antibacterial active substance and application thereof. According to the invention, oleic acid, oosporin, 2, 4-dihydroxy-6-benzyl formic acid and dioctyl terephthalate, which have antibacterial activity, are separated from fermentation products of lecanicillium lecanii. Experiments prove that the oleic acid, the oosporin, the 2, 4-dihydroxy-6-benzyl formic acid and the dioctyl terephthalate have good bacteriostatic activity on wheat stripe rust, fusarium pseudograminearum and fusarium graminearum, can be applied to prevention and treatment of wheat stripe rust, plant scab and plant basal stem rot, and provide more compound choices for development of biopesticides.

Description

[0001] This application is a divisional application of the parent application, application number CN202510628960.0, and the application date is 2025-05-16. Technical Field

[0002] This invention belongs to the field of agricultural microbial technology and relates to an antibacterial active substance and its application. Background Technology

[0003] wheat( Triticum aestivum Wheat (L.) is the most widely distributed and cultivated cereal crop globally, serving as a staple food for 40% of the world's population. However, wheat is susceptible to pathogen infection throughout its growth and development, especially fungal diseases, which are a significant factor affecting wheat yield. Among these, wheat stripe rust (L.) is particularly prevalent. P. striiformis f.sp. Tritici ), wheat scab ( Fusarium head blight ) and wheat stem base rot (C rown rot Straw rust, wheat scab, and wheat stem rot are major diseases of wheat. Therefore, effectively controlling these fungal diseases is one of the key means to increase wheat yield.

[0004] Currently, wheat disease control strategies mainly rely on disease-resistant breeding and chemical control. While using disease-resistant varieties is the most economical and environmentally friendly measure for controlling wheat diseases, the frequent mutations in stripe rust fungus and the continuous emergence of new pathogenic races have led to the loss of resistance in resistant wheat varieties. Furthermore, resistance to Fusarium head blight and stem rot is extremely complex, controlled by multiple genes, and currently, there are no highly resistant varieties available for widespread application in production. Chemical control remains a powerful tool for plant disease control, but due to over-reliance on various chemical pesticides, it currently faces problems such as high resistance, poor durability, environmental pollution, and food safety issues caused by pesticide residues. Moreover, for soil-borne diseases, chemical fungicides often fail to effectively kill pathogens in the soil and can also affect beneficial microorganisms in the soil.

[0005] In contrast, biological control has advantages such as not polluting the environment, long-term inhibition of pathogens, abundant natural resources, and ease of development, making it a research hotspot for the control of fungal diseases in wheat. Finding microorganisms with antifungal activity and their metabolites has become a key means of biological control of fungal diseases. However, there are no reports on the antifungal active substances of *Cercospora filamentosa*. Researching the antifungal active substances of this fungus will provide new ideas for the control of plant fungal diseases. Summary of the Invention

[0006] To solve the above-mentioned technical problems, this invention utilizes *Cyclocarya paliurus*, a fungus previously isolated from our laboratory and deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 41682.Lecanicillium aphanocladill The compound with antibacterial activity is obtained by separation and purification in GC-2, and the antifungal activity of the screened compound is further studied, aiming to provide a new idea for preventing and treating plant fungal diseases such as wheat stripe rust, wheat scab, and stem base rot.

[0007] In one aspect, the application provides an application of an antibacterial active substance in inhibiting the growth of plant fungi, wherein the plant fungi are one or more of Puccinia striiformis, Fusarium pseudograminearum and Fusarium graminearum, and the antibacterial active substance is one or more of oleic acid, oosporein, 2,4-dihydroxy-6-benzyl formic acid and dioctyl terephthalate.

[0008] Further, in the application, the antibacterial active substance is obtained by separation from fermentation broth of Ampelomyces quisqualis, and the preservation number of the Ampelomyces quisqualis is CGMCC No. 41682.

[0009] Further, in the application, when the plant fungi are Puccinia striiformis, the concentration of the oleic acid is 25 ppm to 100 ppm, the concentration of the oosporein is 25 ppm to 100 ppm, the concentration of the 2,4-dihydroxy-6-benzyl formic acid is 25 ppm to 100 ppm, and the concentration of the dioctyl terephthalate is 25 ppm to 100 ppm.

[0010] Further, in the application, when the plant fungi are Fusarium pseudograminearum or Fusarium graminearum, the concentration of the oleic acid is 25 ppm to 100 ppm, the concentration of the oosporein is 25 ppm to 100 ppm, the concentration of the 2,4-dihydroxy-6-benzyl formic acid is 25 ppm to 100 ppm, and the concentration of the dioctyl terephthalate is 5 ppm to 50 ppm.

[0011] In another aspect, the application also provides an application of an antibacterial active substance in preventing and treating plant fungal diseases induced by Puccinia striiformis, Fusarium pseudograminearum or Fusarium graminearum, wherein the antibacterial active substance is one or more of oleic acid, oosporein, 2,4-dihydroxy-6-benzyl formic acid and dioctyl terephthalate.

[0012] Further, in the application, the antibacterial active substance is obtained by separation from fermentation broth of Ampelomyces quisqualis, and the preservation number of the Ampelomyces quisqualis is CGMCC No. 41682.

[0013] Further, in the application, the plant fungal diseases are wheat stripe rust, plant scab or plant stem base rot.

[0014] Finally, the present invention also provides a method for controlling plant fungal diseases induced by wheat stripe rust, Fusarium graminearum, or Fusarium graminearum, comprising applying an antibacterial active substance to the plant, said antibacterial active substance being composed of one or more of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate.

[0015] Furthermore, in the method, the plant fungal disease is wheat stripe rust, plant scab, or plant stem rot.

[0016] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: This invention relates to the *Cyclocarya paliurus* species isolated in our laboratory previously and deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 41682. Lecanicillium aphanocladill Compounds with antibacterial activity, namely oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate, were isolated and purified by GC-2. Further microbiological tests were conducted to verify the activity of these antibacterial substances. The results showed that oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate all exhibited good inhibitory activity against wheat stripe rust, *Fusarium graminearum*, and *Fusarium graminearum*, and can be applied to the control of wheat stripe rust, plant scab, and plant stem rot. Attached Figure Description

[0017] Figure 1 The images show the NMR spectra of oleic acid. A is the 1H NMR spectrum of oleic acid; B is the 1C NMR spectrum of oleic acid.

[0018] Figure 2 The images show the nuclear magnetic resonance (NMR) spectra of oosporin. A is the hydrogen NMR spectrum of oosporin; B is the carbon NMR spectrum of oosporin.

[0019] Figure 3 The NMR spectra of 2,4-dihydroxy-6-benzylcarboxylic acid are shown below. A is the 1H NMR spectrum of 2,4-dihydroxy-6-benzylcarboxylic acid; B is the 1C NMR spectrum of 2,4-dihydroxy-6-benzylcarboxylic acid.

[0020] Figure 4 The images show the nuclear magnetic resonance (NMR) spectra of dioctyl terephthalate. A is the 1H NMR spectrum of dioctyl terephthalate; B is the 1C NMR spectrum of dioctyl terephthalate.

[0021] Figure 5 This is a diagram showing the antibacterial effect of oleic acid on wheat stripe rust.

[0022] Figure 6 This is a diagram showing the antibacterial effect of oosporin on wheat stripe rust.

[0023] Figure 7 The image shows the antibacterial effect of 2,4-dihydroxy-6-benzylcarboxylic acid on wheat stripe rust.

[0024] Figure 8 This image shows the antibacterial effect of dioctyl terephthalate on wheat stripe rust.

[0025] Figure 9 This is a diagram showing the antibacterial effect of oleic acid on Fusarium graminearum.

[0026] Figure 10 This is a diagram showing the antibacterial effect of oleic acid on Fusarium graminearum.

[0027] Figure 11 This image shows the antibacterial effect of oosporin against Fusarium graminearum.

[0028] Figure 12 This is a diagram showing the antibacterial effect of oosporin against Fusarium graminearum.

[0029] Figure 13 The image shows the antibacterial effect of 2,4-dihydroxy-6-benzylcarboxylic acid on Fusarium graminearum.

[0030] Figure 14 The image shows the antibacterial effect of 2,4-dihydroxy-6-benzylcarboxylic acid on Fusarium graminearum.

[0031] Figure 15 This is a diagram showing the antibacterial effect of dioctyl phthalate on Fusarium graminearum.

[0032] Figure 16 This is a diagram showing the antibacterial effect of dioctyl phthalate on Fusarium graminearum. Detailed Implementation

[0033] The technical solution of the present invention will be described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.

[0034] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0035] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0036] Example 1 This embodiment describes the preparation of *Heterocystis suis*. Lecanicillium aphanocladill GC-2 fermentation broth.

[0037] The *Heterocarya stenoptera* fungus used in this example Lecanicillium aphanocladillGC-2 was previously isolated by our laboratory and deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences. The collection was received by the collection center on December 4, 2024; the deposit certificate was issued on January 2, 2025; the accession number is CGMCC No. 41682. Hereinafter, it will be referred to as *C. 41682*.

[0038] Primary seed preparation: Spores or mycelia of *C. 41682* (CGMCC No. 41682) from slant culture, glycerol cryovials, or freeze-dried tubes are inoculated into 500 mL Erlenmeyer flasks containing 100 mL of seed culture medium under strict aseptic conditions. The flasks are then incubated at 25–30 °C on a shaker at 280 rpm for 5–7 days. Samples are taken, stained, and examined under a microscope under strict aseptic conditions. If the results are satisfactory, a 1:1 ratio of 40% sterile glycerol solution is added, mixed thoroughly, and dispensed into 2 mL cryovials. The mixture is then stored at -80 °C to obtain the primary seed culture of *C. 41682*.

[0039] The seed culture medium is agar medium, and any commercially available agarose medium can be used. The preparation method of the agar medium used in this invention is as follows: weigh 200 g of potato, 20 g of agar, and 20 g of glucose, dissolve them in distilled water, and then make up to 1000 mL with distilled water. Sterilize at 121°C for 20 min.

[0040] Silky wax scale fungus Lecanicillium aphanocladill Preparation of GC-2 fermentation broth: Primary seeds of the preserved *C. 41682*, CGMCC No. 41682, were inoculated into a secondary seed culture medium or fermentation medium at an inoculum volume of 3-10%. The secondary seed culture and fermentation medium were the same as those used in the primary seed preparation process, namely agar medium. Fermentation conditions were 25-30°C at 280 rpm on a shaker for 5-7 days to obtain *C. 4168*. Lecanicillium aphanocladill GC-2 fermentation broth.

[0041] Example 2 This embodiment describes the isolation and identification of antibacterial active substances from *Cercospora filamentosa* CGMCC No. 41682.

[0042] Fermentation broth pretreatment: The *Firmiana filamentosa* prepared in Example 1 Lecanicillium aphanocladillThe GC-2 fermentation broth was filtered to obtain two parts: fermentation filtrate and mycelium. The fermentation filtrate was used for later use.

[0043] Treatment of fermentation filtrate: The fermentation filtrate was separated and purified by extraction. An equal volume of chloroform was mixed with the fermentation filtrate and stirred thoroughly for 1 ± 0.2 hours. The active substances in the fermentation filtrate were transferred to the solvent, and then the chloroform phase was separated. The filtrate was evaporated to dryness under reduced pressure to obtain the antibacterial active substance of *C. 41682*.

[0044] The vacuum drying conditions are: vacuum degree 0.1~0.09MPa, temperature 40~60℃; Isolation of antibacterial active substances from *C. 41682* (CGMCC No. 41682): The antibacterial active substances of *C. 41682*, prepared in the above steps, were further separated using silica gel column chromatography. The separation steps were as follows: (1) Column wet packing: Use a glass column with a diameter of 10~50 mm and a diameter-to-height ratio of 1:10~30; wet the silica gel with sufficient petroleum ether, stir evenly, pack it into the glass column, wash off the silica gel on the wall with petroleum ether, let it stand for more than 30 minutes, and release the excess solvent for later use. (2) Sample preparation: Dissolve the antibacterial active substance of CGMCC No. 41682 of Fibrostomium filamentosa in dichloromethane, add silica gel at a ratio of dichloromethane:silica gel = 4~5:1 (V / W), stir well, and evaporate the solvent; (3) Sample loading: Carefully add the mixture of silica gel and sample into the column, just above the liquid surface; (4) Gradient elution: Elution was performed sequentially with 100% petroleum ether, petroleum ether:ethyl acetate = 100:1, 50:1, 20:1, 10:1, 5:1, 1:1, 100% ethyl acetate, and dichloromethane:methanol = 10:1, 5:1, 2:1, 1:1. The volume of each eluent was 3 to 5 times the volume of the silica gel column, and the eluent was collected according to the volume of the silica gel column. The obtained components JQ2, JQ3, JQ4, and JQ10 were identified by nuclear magnetic resonance. The identification results are as follows: Figures 1-4 As shown. Among them. Figure 1 For JQ2 identification results, Figure 2 For JQ3 identification results, Figure 3 For JQ4 identification results, Figure 4 The results are for JQ10 identification.

[0045] The results showed that JQ2 was oleic acid. 1 H NMR (400 MHz, CDCl3) δ 5.43 – 5.22 (m, 2H), 2.34 (t,J = 7.5 Hz, 2H), 2.01 (dd, J = 12.1, 6.2 Hz, 3H), 1.67 – 1.58 (m, 2H), 1.32 – 1.24 (m, 18H), 0.88 (dd, J = 8.7, 4.9 Hz, 3H); 13 C NMR (101 MHz, CDCl3) δ 180.03, 130.04,129.74, 34.07, 31.93, 29.78, 29.70, 29.61, 29.54, 29.34, 29.16, 29.08, 29.05,27.23, 27.17, 24.68, 22.71, 14.13. JQ3 is oosporin. 1 H NMR (400 MHz, DMSO) δ 11.11 (s, 3H), 1.82 (s, 6H); 13 C NMR (101 MHz, DMSO) δ 113.32, 107.68, 8.07. JQ4 is 2,4-dihydroxy-6-benzylcarboxylic acid. 1 H NMR (400 MHz, DMSO) δ 12.42 (s, 1H), 10.14 (s, 1H), 6.18 (d, J = 2.0Hz, 1H), 6.12 (d, J = 2.3 Hz, 1H), 2.40 (s, 3H); 13 C NMR (101 MHz, DMSO) δ173.73, 164.84, 162.40, 143.47, 111.43, 105.28, 101.02, 23.93. JQ10 is dioctyl terephthalate. 1 H NMR (400 MHz, CDCl3) δ 7.74 – 7.67 (m, 2H), 7.56 – 7.50 (m, 2H), 4.26 – 4.17 (m, 4H), 1.44 – 1.29 (m, 17H), 0.91 (dt, J = 8.8, 6.9 Hz, 13H); 13CNMR (101 MHz, CDCl3) δ 167.83, 132.46, 131.03, 128.84, 68.19, 38.74, 30.38, 28.96, 23.76, 23.04, 14.12, 11.01. Example 3 This example demonstrates an in vitro antibacterial test of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate.

[0046] (1) Test on the antibacterial effects of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid and dioctyl terephthalate on wheat stripe rust. The in vitro inhibitory effects of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate on wheat stripe rust were tested using the spore germination method.

[0047] Based on the preliminary test results, oleic acid, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate were dissolved in DMSO and then prepared into solutions with concentrations of 25 ppm, 50 ppm, 100 ppm, and 200 ppm using Tween-20 water for later use; oosporin was dissolved in DMSO and then prepared into solutions with concentrations of 5 ppm, 25 ppm, 50 ppm, and 100 ppm using Tween-20 water for later use.

[0048] One drop each of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate (distilled water was used for the control group) was placed on a clean glass slide. A small amount of wheat stripe rust urediniospores was picked up with an inoculation needle and shaken onto the surface of the droplet. The slide was inverted to form a hanging droplet, which was then placed on a small glass rod lined with moistened absorbent paper at the bottom of a petri dish. The petri dish was placed at 10–14°C for 6–12 hours. Spore germination was checked after 6–12 hours; spores were considered to have germinated when the germ tube length exceeded 50% of the spore diameter. The in vitro inhibitory effects of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate on wheat stripe rust were as follows: Figures 5-8 As shown, where Figure 5 This image shows the antibacterial effect of oleic acid on wheat stripe rust. Figure 6 This image shows the antibacterial effect of oosporin against wheat stripe rust. Figure 7 The image shows the antibacterial effect of 2,4-dihydroxy-6-benzylcarboxylic acid on wheat stripe rust. Figure 8The image shows the antibacterial effect of dioctyl terephthalate (DTP) on wheat stripe rust. The results indicate that oleic acid, oosporin, and 2,4-dihydroxy-6-benzylcarboxylic acid all exhibited inhibitory effects on wheat stripe rust within the concentration range of 25–100 ppm, with the optimal inhibitory effect observed at 25 ppm. DTP also showed inhibitory effects on wheat stripe rust within the same concentration range, with the best inhibitory effect observed at 50 ppm.

[0049] (2) Test on the antibacterial effects of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid and dioctyl terephthalate on the mycelia of Fusarium graminearum and Fusarium pseudograminearum Fusarium graminearum is the pathogen of Fusarium head blight, while Fusarium pseudograminearum is the pathogen of stem rot. Fusarium graminearum and Fusarium pseudograminearum are often used to evaluate the control effects of Fusarium head blight and stem rot. In this embodiment, the inhibitory effects of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate on Fusarium graminearum and Fusarium pseudograminearum are evaluated based on the mycelial growth rate method.

[0050] Preparation of the stock solution: Oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate were dissolved separately (using DMSO) according to the method for indoor toxicity assays, diluted with Tween-20 water, and prepared to a concentration of 1×10⁻⁶. 4 The ppm stock solution was stored in a refrigerator at 4°C for a short period of time for future use.

[0051] 45 mL of the pre-prepared PDA medium was quantitatively added to a 100 mL pre-sterilized and dried Erlenmeyer flask. The stock solutions of oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate were added sequentially from low to high concentration to prepare the final concentrations of the different compounds shown in Table 1. The mixture was thoroughly shaken, and then poured into three equal volumes into three 9 cm diameter petri dishes to prepare plates containing the different concentrations of compounds as shown in Table 1. The PDA medium plates without the compounds served as a blank control (CK), and each treatment was repeated in triplicate.

[0052] Table 1 Concentration gradient of the four compounds

[0053] Indoor toxicity tests were conducted using the mycelial growth rate method. Based on the preliminary test results, under aseptic conditions, activated *Fusarium graminearum* and *Fusarium pseudograminearum* were used. 7 mm diameter mycelial cakes were punched from the edge of vigorous mycelia using a sterilized punch and inoculated into the center of prepared plates containing the compounds. The plates were sealed with sealing film and incubated in the dark at 25±1℃. When the mycelia of the blank control reached 3 / 4 of the plate, the colony diameter was measured using the cross-crossing method and compared with the blank control without the compounds. The inhibition rate of each fungicide on mycelial growth was calculated using the following formula. The recorded data were analyzed using SPSS 25.0 software to calculate the toxicity regression equation and EC50 of different compounds on the mycelial growth of *Fusarium graminearum* and *Fusarium pseudograminearum*. 50 Values ​​and correlation coefficients (R) 2 The results are shown in Tables 2-5. Figures 9-16 As shown.

[0054] Growth inhibition rate (%) = [1 - (diameter of treated colonies - diameter of mycelial cake) / (diameter of control colonies - diameter of mycelial cake)] × 100 Table 2. Test results of toxicity of oleic acid against Fusarium graminearum and Fusarium pseudograminearum hyphae.

[0055] Table 3. Test results of toxicity of oosporin against Fusarium graminearum and Fusarium pseudograminearum hyphae.

[0056] Table 4. Virulence test results of 2,4-dihydroxy-6-benzylcarboxylic acid against Fusarium graminearum and Fusarium pseudograminearum hyphae.

[0057] Table 5. Test results of the toxicity of dioctyl terephthalate against Fusarium graminearum and Fusarium pseudograminearum hyphae.

[0058] Table 2 Figure 9 , Figure 10 The results show that oleic acid concentrations in the range of 25–100 ppm have a significant inhibitory effect on the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum*, with the best inhibitory effect observed at a concentration of 100 ppm.

[0059] Table 3 Figure 11 , Figure 12 The results showed that oosporin concentrations in the range of 5–50 ppm significantly inhibited the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum*, with the best inhibitory effect observed at a concentration of 50 ppm.

[0060] Table 4 Figure 13 , Figure 14 The results showed that 2,4-dihydroxy-6-benzylcarboxylic acid had a significant inhibitory effect on the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum* when the concentration of 2,4-dihydroxy-6-benzylcarboxylic acid was in the range of 25 to 100 ppm, and the inhibitory effect on the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum* was the best when the concentration of 2,4-dihydroxy-6-benzylcarboxylic acid was 100 ppm.

[0061] Table 5 Figure 15 , Figure 16 The results indicate that dioctyl terephthalate (DTP) has a significant inhibitory effect on the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum* when the concentration is in the range of 25–100 ppm. The DTP concentration of 100 ppm shows the best inhibitory effect on the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum*.

[0062] The above results indicate that oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid, and dioctyl terephthalate have a strong inhibitory effect on the mycelial growth of *Fusarium graminearum* and *Fusarium graminearum*.

[0063] In summary, it can be seen that the antibacterial active substances of *C. 41682*, namely oleic acid, oosporin, 2,4-dihydroxy-6-benzylcarboxylic acid and dioctyl terephthalate, of the *C. 41682* exhibit good activity against wheat stripe rust, *Fusarium graminearum*, and *Fusarium pseudograminearum*, and can be used for the prevention and control of wheat stripe rust, plant scab, and plant stem rot.

[0064] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. The application of an antibacterial active substance in inhibiting the growth of plant fungi, characterized in that, The plant fungus is Fusarium graminearum, and the antibacterial active substance is oosporin.

2. The application according to claim 1, characterized in that, The antibacterial active substance is derived from *Hemiberlesia lataniae*. Lecanicillium aphanocladill The *Cercospora filamentosa* was obtained by isolating the fermentation broth of GC-2. Lecanicillium aphanocladill The accession number for GC-2 is CGMCC No. 41682.

3. The application according to claim 1, characterized in that, The concentration of the oosporin is 25 ppm to 100 ppm.

4. The application of an antibacterial active substance in the control of plant fungal diseases induced by Fusarium graminearum, characterized in that, The antibacterial active substance is oosporin.

5. The application according to claim 4, characterized in that, The antibacterial active substance is derived from *Hemiberlesia lataniae*. Lecanicillium aphanocladill The *Cercospora filamentosa* was obtained by isolating the fermentation broth of GC-2. Lecanicillium aphanocladill The accession number for GC-2 is CGMCC No. 41682.

6. The application according to claim 5, characterized in that, The fungal disease of the plant is Fusarium head blight.

7. A method for controlling plant fungal diseases induced by Fusarium graminearum, characterized in that, This includes applying an antibacterial active substance to plants, wherein the antibacterial active substance is oosporin.

8. The method according to claim 7, characterized in that, The fungal disease of the plant is Fusarium head blight.

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