Streptomyces fusichromogenes AK308 and application thereof

Abstract

This invention belongs to the field of biological control technology, specifically disclosing a strain of *Streptomyces fusiforme* AK308 and its applications. The *Streptomyces fusiforme* AK308 provided by this invention has the preservation number CGMCC No. 35050. This strain possesses broad-spectrum antifungal activity and can be used for biocontrol of various plant fungal diseases, including apple leaf spot, wheat scab, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, and tomato early blight. The fermentation product of AK308 has good inhibitory effects on 12 pathogenic fungi, including *Fusarium graminearum* and *Fusarium graminearum*. Botryosphaeria berengeriana and Valsa ceratosperma EC 50 The concentration can be as low as 0.02 μg / mL and 0.06 μg / mL, and this strain has a wide range of applications.

Description

Technical Field

[0001] This invention belongs to the field of biological control technology and relates to a strain of Streptomyces fusiforme AK308 and its applications. Background Technology

[0002] Plant fungal diseases are among the most destructive biological stressors in agricultural production, causing a 10%-30% reduction in global major food crop yields annually, according to FAO statistics, resulting in economic losses exceeding US$220 billion. The pathogens causing plant fungal diseases are numerous and diverse, generally characterized by short infection cycles, varied transmission vectors (soil, seeds, airflow, irrigation water), and strong environmental adaptability. Outbreaks often lead to widespread crop death, fruit rot, and a sharp decline in quality, sometimes resulting in total crop failure. Conventional chemical fungicides pose serious challenges in control, including pathogen resistance, environmental pollution, and disruption of soil microecological balance. Their effectiveness is inconsistent, and costs are constantly rising. Finding efficient, environmentally friendly, and sustainable alternative control strategies has become an urgent need for sustainable agricultural development globally.

[0003] Biological control utilizes beneficial microorganisms or their metabolites to inhibit plant pathogens, offering advantages such as good environmental compatibility, low likelihood of inducing drug resistance, and some strains also possessing growth-promoting effects. Among numerous biocontrol microorganisms, *Streptomyces* is considered an ideal candidate for developing biocontrol agents against fungal diseases due to its abundant antifungal secondary metabolites and strong soil colonization ability. Although *Streptomyces* holds great potential as a biocontrol resource pool, significant differences exist in the biocontrol efficacy, environmental adaptability, and metabolite profiles among different strains. While existing *Streptomyces* strains used for biocontrol possess some broad-spectrum antifungal activity, reports on *Streptomyces* effective against diseases such as Fusarium head blight in wheat, wilt in cotton, leaf spot in celery, and ear rot in maize are rare. Therefore, further screening for *Streptomyces* strains with broad-spectrum and highly effective antagonistic activity against these plant diseases is of great significance. Summary of the Invention

[0004] In response to the current lack of effective control technologies against Streptomyces fungi that cause diseases such as Fusarium head blight in wheat, wilt in cotton, leaf spot in celery, and ear rot in maize, this invention creatively discovers a Streptomyces fusiforme strain AK308. This strain exhibits significant antagonistic activity against a variety of diseases, including apple spot leaf drop, wheat Fusarium head blight, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, and tomato early blight. It demonstrates highly efficient and stable disease control effects and shows promising application prospects.

[0005] To achieve the above-mentioned objectives, the embodiments of the present invention employ the following technical solutions:

[0006] Firstly, this invention provides a strain of *Streptomyces fusiforme* AK308, which was isolated from the water of Lake Ailik in Karamay City, Xinjiang, and has been identified as belonging to... Streptomyces netropsis This strain was deposited on June 30, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 35050.

[0007] Analysis of the biosynthetic gene clusters of secondary metabolites using antiSMASH revealed that the *Streptomyces fusiforme* AK308 provided in this invention can produce more than 40 secondary metabolites, including polyketides, non-ribosomal peptides, and ribosomal peptides. These metabolites contain various antibiotic-like substances such as herbimycin A, kinamycin, kirromycin, and nystatin A1. This strain exhibits the potential for a potent and long-lasting antifungal spectrum due to its abundant secretion of antifungal secondary metabolites. Antifungal experiments have demonstrated that this strain exhibits significant antagonistic activity against various diseases, including wheat scab, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, and tomato early blight. This provides valuable microbial resources and technical support for developing efficient, safe, and environmentally friendly green control strategies for plant fungal diseases.

[0008] Secondly, this invention provides the application of *Streptomyces fusiforme* AK308 in the prevention and control of plant fungal diseases, wherein the pathogens of the plant fungal diseases include... Alternaria brassicae, Fusarium graminearum, Valsa Ceratosperma, Septoria apiicola, Fusarium verticillioides, Bipolaris sorokiniana,Rhizoctonia solani and Altemaria solani At least one of them.

[0009] Preferably, the pathogens causing the plant fungal disease also include... Botrytis cinerea , Fusarium oxysporum , Botryosphaeria berengeriana or Alternaria alternate At least one of them.

[0010] More preferably, the plant includes at least one of the following: grapes, apples, wheat, cotton, celery, maize, solanum, or pears.

[0011] More preferably, the plant includes at least one of grapes, apples, wheat, cotton, celery, corn, potatoes, tomatoes, or pears.

[0012] Thirdly, the present invention provides a biological control agent for plant fungal diseases, wherein the biological control agent includes the Streptomyces fusiforme AK308 or its fermentation product as described in claim 1;

[0013] The plant fungal diseases include at least one of the following: apple scab, wheat scab, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, or tomato early blight.

[0014] Preferably, the plant fungal disease also includes at least one of grape gray mold, cotton wilt, apple ring rot, or pear black spot.

[0015] Preferably, the method for preparing the fermentation product of *Streptomyces fusiforme* AK308 includes the following steps:

[0016] After liquid fermentation of Streptomyces fusiforme AK308, liquid and solid components were separated.

[0017] The liquid component is extracted with esters to obtain an organic phase, and the solid component is ultrasonically treated with a short-chain alcohol to obtain a short-chain alcohol phase;

[0018] The organic phase was mixed with the short-chain alcohol phase and concentrated to obtain the fermentation product.

[0019] More preferably, the temperature of the liquid fermentation is 28℃-32℃ and the fermentation time is 96h-144h;

[0020] For example, the temperature of the liquid fermentation is 30°C and the fermentation time is 120 hours (i.e., 5 days).

[0021] More preferably, the fermentation medium for liquid fermentation comprises: 2.0%-2.8% glucose, 0.6%-1.0% soluble starch, 1%-2% peanut cake powder, 0.5%-1.0% corn steep liquor, 0.3%-0.5% sodium chloride, 0.2%-0.4% calcium carbonate, 0.01%-0.03% potassium dihydrogen phosphate, 1%-3% walnut oil, and the balance being water.

[0022] For example, the fermentation medium formula is: 2.4% glucose, 0.8% soluble starch, 1.5% peanut cake powder, 0.8% corn steep liquor, 0.4% sodium chloride, 0.3% calcium carbonate, 0.02% potassium dihydrogen phosphate, and 2% walnut oil, with the balance being water.

[0023] This invention creatively discovers that, compared with the fermentation medium without added walnut oil, the culture medium with added walnut oil can increase the content of mandimycin in the fermentation broth of Streptomyces fusiforme AK308 by more than 8 times, thereby improving the antibacterial activity of the fermentation product.

[0024] More preferably, the esters include ethyl acetate.

[0025] More preferably, the short-chain alcohol includes methanol or ethanol.

[0026] More preferably, the ultrasound duration is 8-15 minutes.

[0027] The *Streptomyces fusiforme* AK308 strain provided by this invention possesses the potential to secrete abundant antifungal secondary metabolites and exhibit a potent and long-lasting antifungal spectrum. Indoor antifungal activity experiments have confirmed that this strain has broad-spectrum antifungal activity and can be used for biocontrol of various plant fungal diseases, including apple leaf spot, wheat scab, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, and tomato early blight. The crude extract of AK308 fermentation broth is effective against *Fusarium graminearum* (the causal agent of wheat scab). Fusarium graminearum Celery leaf spot pathogen ( Septoria apiicola ), corn ear rot fungus ( Fusarium verticillioides It showed good inhibitory effects on 12 pathogenic fungi, including EC. 50 The values ​​were all less than 10 μg / mL; for pathogenic fungi causing apple rot and apple ring rot. Botryosphaeria berengeriana and Valsa ceratosperma EC 50 The concentrations can be as low as 0.02 μg / mL and 0.06 μg / mL, thus Streptomyces fusiforme AK308 has a wide range of applications. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a diagram illustrating the inhibitory effect of strain AK308 on pear black spot fungus in Example 1 of the present invention.

[0030] Figure 2 This is a colony morphology diagram of strain AK308 in Example 1 of the present invention; wherein, Figure 2 A represents the positive colony morphology. Figure 2 B represents the colony morphology on the reverse side;

[0031] Figure 3 This is the phylogenetic tree of strain AK308 constructed in Example 1 of the present invention;

[0032] Figure 4 This is a liquid chromatogram of the crude extract of *Streptomyces fusiforme* AK308 fermentation broth in Example 2 of the present invention;

[0033] Figure 5 The ultraviolet absorption spectrum of compound 3 in Example 2 of this invention is shown.

[0034] Figure 6 This is the mass spectrum of compounds 1-4 from the crude extract of *Streptomyces fusiforme* AK308 fermentation broth in Example 2 of this invention. Figure 6 A is the mass spectrum of compound 1. Figure 6 B is the mass spectrum of compound 2. Figure 6 C is the mass spectrum of compound 3. Figure 6 D is the mass spectrum of compound 4;

[0035] Figure 7 This is a partial diagram showing the antibacterial effect of the crude extract of AK308 fermentation broth in Example 2 of the present invention;

[0036] Figure 8 This is a comparison chart of the peak area of ​​mandimycin in the crude extract of *Streptomyces fusiforme* AK308 fermentation broth prepared in Examples 2 and 3 of this invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] Unless otherwise specified, the raw materials and reagents used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0039] Example 1

[0040] This embodiment provides the isolation, identification, and preservation of *Streptomyces fusiforme* AK308, which was isolated from the water of Lake Ailik, 85 km northeast of Karamay City, Xinjiang. The specific isolation and purification methods for this strain are as follows:

[0041] (1) Isolation and screening of strains

[0042] Water samples taken from Lake Erik were serially diluted with sterile distilled water, spread on Gao's No. 1 solid medium, and incubated at 30°C for 5 days. After observation, actinomycete colonies with different appearances were picked and purified on new Gao's No. 1 solid medium to obtain a series of candidate antagonistic strains.

[0043] The plate confrontation culture method was used to further screen the above-isolated candidate antagonistic bacteria, among which *Pyrus pyrifolia* (pear black spot pathogen) was the most prominent. Alternaria alternate The indicator bacteria were selected. Using a punch, 7mm diameter mycelial discs of the candidate antagonist bacteria and *Pyrus pyrifolia* were taken from activated agar plates and inverted onto PDA medium. The plates were incubated at 28°C for 5 days, and the inhibitory effect was observed. Based on the inhibitory effect, strain AK308 was found to be the most effective against *Pyrus pyrifolia*. The inhibitory effect of strain AK308 against *Pyrus pyrifolia* is shown in the figure below. Figure 1As shown.

[0044] (2) Identification of strains

[0045] The AK308 strain was streaked onto Gao's No. 1 medium and incubated at 28℃ for 5 days. The colony morphology of the AK308 strain is shown in the figure below. Figure 2 As shown, where Figure 2 A represents the positive colony morphology. Figure 2 B represents the colony morphology on the reverse side. Figure 2 It can be seen that the colony morphology of strain AK308 is round and smooth, with well-developed aerial hyphae, which are pink to white in color, while the hyphae in the substrate are yellow.

[0046] Strain strain AK308 was inoculated into TSB medium and cultured at 28°C and 200 rpm for 48 h to obtain a single bacterial culture. DNA was extracted from 1 mL of the single culture, and its 16S rDNA gene fragment was amplified by PCR. The 16S rDNA gene sequence of *Streptomyces fusiforme* AK308 is shown in SEQ ID NO.1.

[0047] The gene sequence shown in SEQ ID NO.1 is as follows:

[0048]

[0049] The 16S rDNA gene sequence was sequenced and BLASTed on NCBI for phylogenetic tree construction analysis. The constructed phylogenetic tree of strain AK308 is shown below. Figure 3 As shown.

[0050] Depend on Figure 3 It can be seen that strain AK308 is related to Streptomyces fusiforme ( Streptomyces netropsis The AK308 strain showed the highest homology with *Streptomyces fusiforme* and could aggregate into a single lineage. Based on morphological characteristics and molecular sequence identification, strain AK308 was confirmed to be *Streptomyces fusiforme*. Streptomyces netropsis Therefore, the strain was named Streptomyces spindleii AK308.

[0051] (3) Prediction of antimicrobial substance gene clusters in AK308 strain

[0052] This invention further obtained the complete genome sequence of *Streptomyces fusiforme* AK308 through de novo sequencing and obtained the gene cluster information of secondary metabolite biosynthesis in this strain through antiSMASH. Statistical information of antimicrobial substance-related gene clusters in AK308 predicted by AntiSMASH is shown in Table 1.

[0053] Table 1

[0054]

[0055] Table 1 shows that although similar gene clusters and / or similarity rates are not given for numbers 5, 27, and 30, compounds with structural types of lantopeptide, non-ribosomal peptides (NRPs), and lipids (Esters) can be predicted to be synthesized based on gene structure. Table 1 also shows that *Streptomyces fusiforme* AK308 has the potential to produce at least 40 secondary metabolites, including compounds such as polyketides (PKs), non-ribosomal peptides (NRPs), and ribosomal peptides (RiPPs), containing various antibiotic-like substances such as herbimycin A, kinamycin, kirromycin, and nystatin A1. This suggests that this strain may produce a variety of effective antibacterial substances and has the potential for excellent antibacterial effects.

[0056] (4) Preservation of strains

[0057] Streptomyces fusiforme AK308 was deposited at the China General Microbiological Culture Collection Center (CGMCC) on June 30, 2025, with accession number CGMCC No. 35050. The Latin name of this strain is... Streptomyces netropsis .

[0058] Example 2

[0059] This embodiment provides the application of the fermentation product of *Streptomyces fusiforme* AK308 in the control of plant fungal diseases. A crude extract of AK308 with antibacterial activity was obtained through chemical extraction and separation, and the inhibitory effect of the obtained crude extract on plant fungal pathogens was further investigated. Details are as follows:

[0060] (1) Preparation of crude extract of fermentation broth of Streptomyces fusiforme AK308

[0061] S1. After activating Streptomyces fusiforme AK308 on PDA medium for 3 days, scrape off approximately 1 cm of the sample. 2 Mycelia were inoculated into 250 mL shake flasks containing 50 mL of fermentation medium and cultured at 30 °C and 200 rpm for 5 days. The fermentation medium consisted of: 2.4% glucose, 0.8% soluble starch, 1.5% peanut meal, 0.8% corn steep liquor, 0.4% sodium chloride, 0.3% calcium carbonate, 0.02% potassium dihydrogen phosphate, and 2% walnut oil, with the remainder being water.

[0062] S2. Centrifuge the fermentation broth after the above culture at 8000 rpm for 5 min to obtain the supernatant; extract the supernatant three times with an equal volume of ethyl acetate, soak the precipitate in methanol for 2 h and sonicate for 10 min, combine the ethyl acetate and methanol phases, evaporate to dryness at 45℃, sonicate the contents of the rotary evaporation flask with a small amount of ethyl acetate, transfer to a 50 mL centrifuge tube, let stand for 10 min, filter to obtain the crude extract, which is a solid powder with a brownish-yellow color, which is the crude extract. 0.1 g of crude extract can be obtained from 1 L of fermentation broth.

[0063] The macrocyclic lactones in the crude extract were detected by high-performance liquid chromatography (HPLC). The HPLC chromatogram of the crude extract is shown below. Figure 4 As shown.

[0064] The specific liquid chromatography conditions are as follows: Waters E2695-2998 PDA detector, Kromasil 100A C18 column (4.6×250mm, 5μm), mobile phase acetonitrile:water = 45:55 (V / V), flow rate 1mL / min, detection wavelength 350nm, and injection volume 10μL.

[0065] Figure 4 In the diagram, compound with peak 1 is designated as compound 1, compound with peak 2 as compound 2, compound with peak 3 as compound 3, and compound with peak 4 as compound 4.

[0066] During the testing process, it was found that the compounds represented by peaks 1-4 in the crude extract obtained from the fermentation broth of *Streptomyces fusiforme* AK308 all exhibited absorption peaks at 319 nm, 334 nm, and 352 nm, consistent with the characteristic absorption of the "three-finger peak" of pentaene macrocyclic lactones. The UV absorption spectrum of compound 3 is shown below. Figure 5 As shown.

[0067] Therefore, it can be known that the crude extract of the fermentation broth of Streptomyces fusiforme AK308 contains four kinds of pentaene macrocyclic lactone compounds.

[0068] Further analysis was conducted using liquid chromatography-mass spectrometry (LC-MS) to infer... Figure 4 The structures of compounds 1-4 are shown. The mass spectra of compounds 1-4 are shown below. Figure 6 As shown. Among them, Figure 6 A is the mass spectrum of compound 1. Figure 6 B is the mass spectrum of compound 2. Figure 6 C is the mass spectrum of compound 3. Figure 6 D is the mass spectrum of compound 4.

[0069] The LC-MS conditions were as follows: Vanquish Flex UHPLC Orbitrap Exploris 120MS system (Thermo Fisher Scientific, USA), ACQUITY BEH C column. 18 (100mm×2.1mm, 1.7μm), injection volume 2μL, mobile phase is acetonitrile:water, 0-2min is 5% acetonitrile, 2-13min acetonitrile increases from 5% to 95%, mass spectrometry detection range 150-2000m / z.

[0070] Analysis revealed that compound 1 was mandimycin B, compound 2 was C-10-deoxymandimycin B, compound 3 was mandimycin, and compound 4 was C-10-deoxymandimycin.

[0071] (2) Detection of the antibacterial activity of crude extract of Streptomyces fusiforme AK308 fermentation broth in vitro

[0072] This invention uses the mycelial growth rate method to determine the antibacterial activity of the crude extract obtained from the fermentation broth of *Streptomyces fusiforme* AK308, specifically examining its inhibitory effect on 12 plant pathogenic fungi, including the pathogen causing grape gray mold. Botrytis cinerea Apple leaf spot disease pathogen Alternaria brassicae Fusarium head blight pathogen Fusarium graminearumApple rot disease pathogens Valsa ceratosperma Pathogens causing cotton wilt Fusarium oxysporum Celery leaf spot pathogen Septoria apiicola Pathogens causing corn ear rot Fusarium verticillioides Apple ring rot pathogen Botryosphaeria berengeriana Pathogens causing wheat root rot Bipolaris sorokiniana Potato black scurf pathogen Rhizoctonia solani Early blight pathogen of tomato Altemaria solani Pear black spot pathogen Alternaria alternate Meanwhile, natamycin, a polyene antibiotic widely used in plant disease control and food preservation, was used as a control.

[0073] The crude extract was dissolved in methanol to prepare a 2 mg / mL stock solution. The stock solution was then serially diluted with methanol to obtain a series of crude extract solutions of different concentrations. These solutions were added to PDA medium to prepare plates with different concentrations of the drug. PDA medium containing the same concentration of methanol was used as a control group.

[0074] 7mm diameter bacterial pellets of pathogenic bacteria were punched out and inverted onto a pharmaceutically controlled agar plate. The plates were incubated at 28℃ with three replicates. When the control group nearly filled the agar plate, the diameter of the pathogenic bacteria was measured using the cross-sectional method. The inhibition rate was calculated using Formula 1. Based on the inhibition rate and the virulence regression equation provided by Formula 2, the median inhibitory concentration (EC50) was deduced. 50 value).

[0075] Formula 1;

[0076] The virulence regression equation is Y = aX + b, as shown in Formula 2.

[0077] In Formula 1, the growth diameter is in mm;

[0078] In Formula 2, X is lg (concentration), Y is the probability value, and b is the intercept.

[0079] The antibacterial effect of the crude extract of AK308 fermentation broth is shown in the following figures. Figure 7 As shown in Table 2, the results of the indoor toxicity test of the crude extract of AK308 fermentation broth against 12 plant pathogens are as follows.

[0080] Table 2

[0081]

[0082] As shown in Table 2, the crude extract of AK308 fermentation broth exhibits good inhibitory effects against all 12 plant pathogenic fungi mentioned above. 50The values ​​were all less than 10 μg / mL. Except for grape gray mold, cotton wilt, and potato black scurf, the inhibitory effect against the other nine plant pathogens was superior to the control natamycin, especially against apple ring rot and apple canker. EC 50 The values ​​can be as low as 0.02 μg / mL and 0.06 μg / mL.

[0083] Example 3

[0084] This embodiment provides the application of the fermentation product of *Streptomyces fusiforme* AK308 in the prevention and control of plant fungal diseases. The method for preparing the fermentation product of *Streptomyces fusiforme* AK308 in this embodiment is basically the same as "(1) Preparation of crude extract of fermentation broth of *Streptomyces fusiforme* AK308" in Example 2, except that: in step S1, the fermentation medium formula does not contain 2% walnut oil, and the rest of the formula is the same; the rest of the preparation steps and parameters are the same as in Example 2, and finally the crude extract of fermentation broth of *Streptomyces fusiforme* AK308 is obtained. The crude extract of fermentation broth of *Streptomyces fusiforme* AK308 obtained in this embodiment and the crude extract of fermentation broth of *Streptomyces fusiforme* AK308 obtained in Example 2 are detected by HPLC, with compound 3-mandimycin as the detection target, and the yield of the two crude extracts is calculated based on the peak area.

[0085] The comparison of the peak area of ​​mandimycin in the crude extracts of *Streptomyces fusiforme* AK308 fermentation broth prepared in Examples 2 and 3 is shown in the figure below. Figure 8 As shown. By Figure 8 It can be seen that the peak area of ​​mandimycin in the crude extract of *Streptomyces fusiforme* AK308 fermentation broth obtained in Example 3 was 83422±11033.44, while the peak area of ​​compound 3 in the crude extract of *Streptomyces fusiforme* AK308 fermentation broth obtained in Example 2 was 815244±34475.32. Therefore, under the same conditions, adding walnut oil to the fermentation medium can increase the content of mandimycin in the *Streptomyces fusiforme* AK308 fermentation broth by 8.77 times.

[0086] Therefore, it is reasonable to speculate that during the fermentation of Streptomyces fusiforme AK308, walnut oil can significantly increase the synthesis of antibiotic compounds, including mandimycin, by this bacterium, thereby significantly enhancing its antibacterial activity.

[0087] Example 4

[0088] Given the excellent resistance of *Streptomyces fusiforme* AK308 to plant pathogenic fungi, it can be used to prepare inoculants for the control of plant fungal diseases. These inoculants can be used to control at least one of the following: apple leaf spot, wheat scab, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, tomato early blight, grape gray mold, cotton wilt, apple ring rot, or pear black spot.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A strain of Streptomyces spicatus (S. spicatus) AK308, characterized by: Streptomyces netropsis ) a 16S rRNA gene sequence of SEQ ID NO:

1. Its accession number is CGMCC No.35050.

2. The application of *Streptomyces fusiforme* AK308 as described in claim 1 in the prevention and control of plant fungal diseases, characterized in that: The pathogenic fungus of the plant fungal disease is at least one of Alternaria brassicae, Fusarium graminearum, Valsa Ceratosperma, Septoria apiicola, Fusarium verticillioides, Bipolaris sorokiniana,Rhizoctonia solani and Altemaria solani .

3. The application of *Streptomyces fusiforme* AK308 as described in claim 2 in the prevention and control of plant fungal diseases, characterized in that: The pathogenic fungus of the plant fungal disease is at least one of Botrytis cinerea , Fusarium oxysporum , Botryosphaeria berengeriana or Alternaria alternate .

4. Use of Streptomyces fimbriatus AK308 according to claim 2 or 3 for the control of fungal diseases of plants, characterized in that: The plants mentioned include at least one of the following: grapes, apples, wheat, cotton, celery, maize, solanum, or pears.

5. The application of *Streptomyces fusiforme* AK308 as described in claim 4 in the prevention and control of plant fungal diseases, characterized in that: The plant includes at least one of grapes, apples, wheat, cotton, celery, corn, potatoes, tomatoes, or pears.

6. A biological control agent for plant fungal diseases, characterized in that: The biological control agent includes Streptomyces fusiforme AK308 as described in claim 1; The plant fungal diseases mentioned are at least one of the following: apple leaf spot, wheat scab, apple rot, celery leaf spot, corn ear rot, wheat root rot, potato black scurf, tomato early blight, grape gray mold, cotton wilt, apple ring rot, or pear black spot.

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