Streptomyces sp. and application thereof

Abstract

The application discloses a streptomyces mutans and application thereof, and belongs to the field of agricultural biotechnology, and the classification and naming of the streptomyces mutans is streptomyces mutans Streptomyces varsoviensis The BZ109 is preserved in the China Center for Type Culture Collection on August 5, 2024, and the preservation number is CCTCC NO: M 20241749, the streptomyces mutans produces aerial hyphae and intracellular hyphae on a potato glucose agar culture medium after being cultured at 28 DEG C for 7 days, does not secrete pigment, the aerial hyphae are chalky, a circle around the hyphae is light gray, and the colony edge is relatively neat. The streptomyces mutans can effectively inhibit the hyphal growth of soybean phytophthora, rhizoctonia solani, fusarium oxysporum, and fusarium graminearum, has good effects in the prevention and control of plant botrytis and plant bacterial wilt, can promote plant growth, and has wide application potential in the field of agricultural biology.

Description

Technical Field

[0001] This invention belongs to the field of agricultural biotechnology, specifically relating to a strain of Streptomyces and its applications. Background Technology

[0002] Currently, chemical fungicides are the primary method for disease control. However, the long-term improper use of chemical pesticides has led to serious ecological and environmental impacts. Plants require a healthy and stable environment to maintain normal development and high yields during their growth. However, the overuse of chemical fungicides not only disrupts this balance but can also trigger a series of chain reactions, thereby weakening the plant's disease resistance. When pesticides are widely applied in the field, beneficial organisms such as bees, birds, and aquatic invertebrates are directly or indirectly exposed to pesticide toxicity through spray drift or leaching, thus affecting their population and health. This impact not only weakens the interrelationships between organisms in nature but also disrupts key ecological services such as plant pollination and natural pest and disease control, ultimately leading to increased plant dependence and a more pronounced reliance on chemical fungicides.

[0003] More seriously, the persistent presence of highly toxic and persistent chemical pesticides in ecosystems leads to bioaccumulation. This not only results in the accumulation of harmful substances in the food chain, causing greater harm to apex predators, but also inflicts irreversible damage on human health and the environment. Chemical pesticide residues can enter soil and water bodies, polluting the environment, reducing soil microbial activity, affecting the normal growth of plant roots, and ultimately impacting plant absorption capacity and overall health. Furthermore, the long-term irrational use of chemical pesticides accelerates the development of fungicide resistance in plant pathogens. Once pathogens develop resistance, traditional control methods become ineffective, leading to the rapid spread of diseases among plants and causing greater crop losses. To curb this trend, agricultural producers often have to increase the amount or frequency of pesticide use, further exacerbating the burden on the ecological environment.

[0004] Against this backdrop, biopesticides are considered a safer and more sustainable alternative to chemical pesticides due to their harmlessness and environmental compatibility. Derived from the metabolites or extracts of organisms in nature, biopesticides are not only more friendly to humans and the environment but also effectively control pests and diseases without disrupting the ecological balance. By rationally utilizing biopesticides, we can reduce dependence on chemical pesticides, maintain the diversity and stability of ecosystems, promote healthy plant growth, and ensure the sustainable development of agricultural production. Furthermore, the use of biopesticides can enhance the plant's own defense mechanisms. For example, some biological agents can induce resistance responses in plants, increasing their resistance to pathogens. This not only reduces the need for external pesticides but also improves crop yield and quality by enhancing plant health. Therefore, promoting the research and application of biopesticides will become an important pathway to achieving sustainable agricultural development. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. For example, one objective of this invention is to provide a strain of Streptomyces to overcome the drawbacks of existing biological pesticides, such as limited range of action, slow onset of action, and significant susceptibility of efficacy to environmental influences.

[0006] To achieve the above objectives, one aspect of the present invention provides a Streptomyces strain, classified as Streptomyces varsoviensis BZ109, which was deposited at the China Center for Type Culture Collection on August 5, 2024, with accession number CCTCC NO: M 20241749.

[0007] Furthermore, the 16S rRNA sequence of Streptomyces is shown in SEQ ID NO.1.

[0008] Furthermore, after Streptomyces was cultured on potato dextrose agar at 28°C for 7 days, aerial hyphae and substrate hyphae were produced on the medium. They did not secrete pigments. The aerial hyphae were chalky white with a light gray ring around them, and the colony edges were relatively neat.

[0009] Another aspect of the present invention provides a method for screening a Streptomyces strain, which isolates Streptomyces from soil samples using a gradient dilution method.

[0010] Further, the gradient dilution method includes the following steps: weigh 10 grams of soil, pour it into a conical flask containing 90 ml of sterile water, and place it in a shaker at 28°C and 200 rpm for 30 minutes; take 1 ml of soil suspension into a centrifuge tube containing 9 ml of sterile water and mix thoroughly; dilute the soil suspension sequentially to 10⁻³, 10⁻⁴, and 10⁻⁵; take 100 μl of soil suspension diluted to 10⁻³, 10⁻⁴, and 10⁻⁵ and spread it on a starch-casein solid medium containing naphthylpyridinone acid (25 μg / ml), actinomycin (25 μg / ml), and nystatin (25 μg / ml), and incubate at 28°C for 5-7 days. Select single colonies that are chalky white in color, rough and dry on the surface, and difficult to pick up, exhibiting hyphae in the substrate during the later stages of cultivation, and inoculate them into a starch-casein liquid medium containing naphthylpyridinol (25 μg / ml), actinomycete ketone (25 μg / ml), and nystatin (25 μg / ml). Incubate at 28°C and 200 rpm for 5-7 days. Then, use a 10 μl inoculation loop to inoculate into a starch-casein solid medium containing naphthylpyridinol (25 μg / ml), actinomycete ketone (25 μg / ml), and nystatin (25 μg / ml) for streak purification. Select single colonies of the purified isolates for propagation. Preserve the propagated isolate suspension with glycerol by mixing the Streptomyces suspension with 50% glycerol at a 1:1 ratio and storing it at -80°C.

[0011] Another aspect of the present invention provides a biological agent comprising Streptomyces as described above, or a suspension thereof, a culture medium thereof, a fermentation product thereof, or a dry powder thereof.

[0012] Furthermore, the dry powder inoculant is obtained by fermenting Streptomyces to obtain a fermentation broth, and then freeze-drying the fermentation broth to obtain the dry powder inoculant; or by spray-drying the fermentation broth to obtain the dry powder inoculant.

[0013] Another aspect of the present invention provides the application of a Streptomyces strain and its biological agents.

[0014] Furthermore, this includes its application in inhibiting the pathogenic fungus Phytophthora in soybean.

[0015] Furthermore, this includes its application in inhibiting Rhizoctonia solani.

[0016] Furthermore, this includes its application in inhibiting Fusarium oxysporum.

[0017] Furthermore, this includes its application in inhibiting Fusarium oxysporum in Fusarium graminearum.

[0018] Furthermore, it includes the role in the prevention and control of plant diseases, including gray mold and bacterial wilt.

[0019] Furthermore, this includes applications in promoting plant growth.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. The Streptomyces varsoviensis BZ109 of the present invention can effectively inhibit the mycelial growth of Phytophthora soybeani, Rhizoctonia solani, Fusarium oxysporum, and Fusarium graminearum. Under plate confrontation culture conditions, the inhibition rate against Phytophthora soybeani reaches nearly 100% after 3-7 days of inoculation culture, and the treatment effect is significant.

[0022] 2. The Streptomyces varsoviensis BZ109 of this invention can also be well applied in the prevention and control of plant diseases. It can effectively control gray mold and also has a good control effect on typical plant bacterial wilt pathogens.

[0023] 3. The Streptomyces varsoviensis BZ109 of this invention also has good application in promoting plant growth and flowering. Foliar spraying and root irrigation of plant plants can significantly promote plant growth and development. Attached Figure Description

[0024] The Streptomyces varsoviensis BZ109 of this invention has been deposited at the China Center for Type Culture Collection (CCTCC), located at Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan, Hubei Province, on August 5, 2024, with accession number CCTCC NO: M 20241749.

[0025] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 The morphology of Streptomyces in Example 2 of this invention cultured on PDA medium;

[0027] Figure 2 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP1 medium.

[0028] Figure 3 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP2 medium.

[0029] Figure 4 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP3 medium.

[0030] Figure 5 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP4 medium.

[0031] Figure 6 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP5 medium.

[0032] Figure 7 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP6 medium.

[0033] Figure 8 This is the morphology of Streptomyces in Example 2 of the present invention cultured on ISP7 medium.

[0034] Figure 9 This is a phylogenetic tree of BZ109 and other Streptomyces species generated by neighbor-joining analysis based on the 16S ribosomal RNA gene in Example 2 of the present invention.

[0035] Figure 10 This image shows the inhibitory effect of strain BZ109 in Example 3 of the present invention on the mycelial growth of Phytophthora soybeana, Rhizoctonia solani, Fusarium oxysporum, and Fusarium graminearum.

[0036] Figure 11 This is a graph showing the inhibitory effect of different concentrations of BZ109 culture filtrate on the mycelial growth of Phytophthora soybeanis in Example 4 of the present invention.

[0037] Figure 12 The image shows the four chili pepper plants selected in Example 5 of this invention.

[0038] Figure 13 This is a comparative diagram showing the inhibitory effect of BZ109 on soybean Phytophthora infestation host pepper in Example 5 of the present invention.

[0039] Figure 14 This is a comparison chart showing the inhibitory effect of BZ109 on gray mold-infected peppers in Example 6 of the present invention.

[0040] Figure 15 This is a diagram showing the antibacterial activity of BZ109 against *Rahuella oxypetalum* in Example 7 of the present invention.

[0041] Figure 16 This is a comparison chart of the growth of cucumber plants treated with BZ109 fermentation broth in Example 8 of the present invention and the control plants on the 14th day after treatment.

[0042] Figure 17 This is a comparison chart of the growth of cucumber plants treated with BZ109 fermentation broth in Example 8 of the present invention and the control plants on the 21st day after treatment. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0044] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended and mean including but not limited to. Unless the context clearly indicates otherwise, the expressions “a” and “an” as used herein include plural references. For example, reference to “a cell” includes a plurality of such cells and equivalents known to those skilled in the art, etc. The term “about” as used herein indicates a range of ±20% of the following numerical value. In some embodiments, the term “about” indicates a range of ±10% of the following numerical value. In some embodiments, the term “about” indicates a range of ±5% of the following numerical value.

[0045] Exemplary Example 1

[0046] In this exemplary embodiment, a strain of Streptomyces is provided.

[0047] The fungus, classified as *Streptomyces varsoviensis* BZ109, was deposited on August 5, 2024, at the China Center for Type Culture Collection (CCTCC). The depositary address is Wuhan University, No. 299 Bayi Road, Wuchang District, Wuhan, Hubei Province, China. The accession number is CCTCC NO: M 20241749.

[0048] In this exemplary embodiment, the 16S rRNA sequence of Streptomyces is shown in SEQ ID NO.1.

[0049] In this exemplary embodiment, after Streptomyces varsoviensis BZ109 was cultured on potato dextrose agar at 28°C for 7 days, aerial hyphae and substrate hyphae were produced on the medium. The bacteria did not secrete pigments. The aerial hyphae were chalky white with a light gray ring around them, and the colony edges were relatively neat.

[0050] Exemplary Example 2

[0051] In this exemplary embodiment, a method for screening a strain of Streptomyces is provided. The strain of Streptomyces in Exemplary Embodiment 1 can be obtained by using the gradient dilution screening method in this exemplary embodiment.

[0052] Specifically, the following steps are included:

[0053] Weigh 10 grams of soil, pour it into an Erlenmeyer flask containing 90 ml of sterile water, and place it in a shaker at 28°C and 200 rpm for 30 minutes.

[0054] Take 1 ml of soil suspension into a centrifuge tube containing 9 ml of sterile water, mix thoroughly, and dilute the soil suspension to 10⁻³, 10⁻⁴, and 10⁻⁵ in sequence. Take 100 μl of the soil suspension diluted to 10⁻³, 10⁻⁴, and 10⁻⁵ and spread it on a starch-casein solid medium containing naphthylpyridinone acid (25 μg / ml), actinomycin (25 μg / ml), and nystatin (25 μg / ml). Incubate at 28°C for 5–7 days.

[0055] Select single colonies that are chalky white in color, rough and dry on the surface, and difficult to pick up, and whose mycelia in the substrate meet the culture characteristics of Streptomyces in the later stage of culture. Place them into a starch-casein liquid medium containing naphthylpyridinol (25 μg / ml), actinomycin (25 μg / ml) and nystatin (25 μg / ml) and culture at 28℃ and 200 rpm for 5-7 days.

[0056] Then, use a 10 μl inoculation loop to inoculate into a starch-casein solid medium containing naridinone acid (25 μg / ml), actinomycin (25 μg / ml), and nystatin (25 μg / ml) for streak purification culture.

[0057] Select purified isolates and propagate them. Preserve the propagated isolate suspension with glycerol by mixing the Streptomyces suspension with 50% glycerol in a 1:1 ratio and storing it in an ultra-low temperature freezer at -80°C.

[0058] Exemplary Example 3

[0059] In this exemplary embodiment, a biological agent prepared based on Streptomyces varsoviensis BZ109 as described in Exemplary Embodiment 1 is provided.

[0060] The biological agent in this exemplary embodiment includes Streptomyces varsoviensis BZ109 obtained as described in the exemplary embodiments above.

[0061] Alternatively, a bacterial suspension prepared according to the Streptomyces strain described in the exemplary embodiments above.

[0062] Or the culture medium of Streptomyces as described in the exemplary embodiments above.

[0063] Alternatively, the fermentation product obtained by fermenting Streptomyces according to the above exemplary embodiment.

[0064] Alternatively, according to the Streptomyces in the above exemplary embodiments, the Streptomyces is fermented to obtain a fermentation broth, and the fermentation broth is freeze-dried to obtain a dry powder inoculant, or spray-dried to obtain a dry powder inoculant.

[0065] Exemplary Example 4

[0066] This exemplary embodiment provides the application of a Streptomyces strain as in Exemplary Embodiment 1 or a biological agent as in Exemplary Embodiment 3, specifically including,

[0067] Application of strain BZ109 and its biological agents in inhibiting the pathogenic fungus Phytophthora in soybean.

[0068] Application of strain BZ109 and its biological agents in inhibiting Fusarium oxysporum.

[0069] Application of strain BZ109 and its biological agents in inhibiting Fusarium oxysporum.

[0070] Application of strain BZ109 and its biological agents in inhibiting Fusarium graminearum.

[0071] The role of strain BZ109 and its biological agents in the control of plant diseases, including gray mold and bacterial wilt.

[0072] Application of strain BZ109 and its biological agents in promoting plant growth.

[0073] To better understand the Streptomyces strain and its application provided in this embodiment, the following description, in conjunction with the accompanying drawings and embodiments, further clarifies the content of the present invention.

[0074] Example 1

[0075] Isolation, purification and preservation of Streptomyces varsoviensis BZ109 (hereinafter referred to as "strain BZ109").

[0076] In this embodiment, soil samples were collected from the rhizosphere soil of a cypress grove in Qinglong Village, Shangxueshan Town, Enyang District, Bazhong City, Sichuan Province. A gradient dilution method was used to isolate Streptomyces from the collected soil samples, ultimately yielding a Streptomyces strain named BZ109. The detailed isolation method is as follows:

[0077] Step 1: Weigh 10 grams of soil, pour it into an Erlenmeyer flask containing 90 ml of sterile water, and place it in a shaker at 28°C and 200 rpm for 30 minutes.

[0078] Step 2: Take 1 ml of soil suspension into a centrifuge tube containing 9 ml of sterile water and mix thoroughly.

[0079] Step 3: Dilute the soil suspension sequentially to 10⁻³, 10⁻⁴, and 10⁻⁵. Take 100 μl of each soil suspension diluted to 10⁻³, 10⁻⁴, and 10⁻⁵ and spread it onto a starch-casein solid medium containing naphthylpyridinone acid (25 μg / ml), actinomycin (25 μg / ml), and nystatin (25 μg / ml). Incubate at 28°C for 5–7 days.

[0080] Step 4: Select single colonies that are chalky white in color, have a rough and dry surface, are not easy to pick up, and whose mycelia in the substrate meet the culture characteristics of Streptomyces in the later stage of culture. Place them into a starch-casein liquid medium containing nadolol (25 μg / ml), actinomycin (25 μg / ml), and nystatin (25 μg / ml). Incubate at 28°C and 200 rpm for 5-7 days for propagation.

[0081] Step 5: Use a 10 μl inoculation loop to inoculate into a starch-casein solid medium containing naridinone acid (25 μg / ml), actinomycin (25 μg / ml), and nystatin (25 μg / ml) for streak purification culture.

[0082] Step 6: Select a single colony of the purified isolate for propagation. Preserve the propagated isolate suspension with glycerol. Mix the propagated isolate suspension with 50% glycerol in a 1:1 ratio and store in an ultra-low temperature freezer at -80℃.

[0083] Example 2

[0084] For the identification of Streptomyces varsoviensis BZ109 (hereinafter referred to as "strain BZ109").

[0085] In this embodiment, the morphological identification of the cultivated Streptomyces was performed. Strain BZ109 was inoculated onto PDA and seven culture media specified in the International Streptomyces Project: ISP1—caseinyeast extract agar; ISP2—yeast extract maltextract agar; ISP3—oatmeal agar; ISP4—inorganicsalt starch agar; ISP5—glycerol asparagine agar; ISP6—peptone yeast extract iron agar; and ISP7—tyrosine agar. After culturing at 28°C for 7 days, the growth of strain BZ109 on the tested media, the color of aerial hyphae, the color of intramural hyphae, and pigment production were recorded. The morphological characteristics of the spores and hyphae of strain BZ109 were observed using scanning electron microscopy.

[0086] Figure 1 The morphology of Streptomyces in this embodiment cultured on PDA medium is shown; Figure 2 The morphology of Streptomyces in this embodiment cultured on ISP1 medium is shown; Figure 3 The morphology of Streptomyces in this embodiment cultured on ISP2 medium is shown; Figure 4 The morphology of Streptomyces in this embodiment cultured on ISP3 medium is shown; Figure 5 The morphology of Streptomyces in this embodiment cultured on ISP4 medium is shown; Figure 6 The morphology of Streptomyces in this embodiment cultured on ISP5 medium is shown; Figure 7 The morphology of Streptomyces in this embodiment cultured on ISP6 medium is shown; Figure 8 The morphology of *Streptomyces* strain BZ109 cultured on ISP7 medium in this embodiment is shown. As can be seen from the attached figures, strain BZ109 produces abundant aerial and substrate hyphae on PDA medium, does not secrete pigment, and the aerial hyphae are white to gray with a light gray ring around them, exhibiting relatively neat colony edges. It grows normally on all other IPS media, and except for chalky white hyphae on IPS2 and IPS4, it appears light gray on other IPS media. Based on these morphological observations, BZ109 is identified as belonging to the genus *Streptomyces*.

[0087] Then, molecular identification was used to further determine the species status of strain BZ109.

[0088] First, the genomic DNA of BZ109 was extracted using the Gram-positive bacterial genomic DNA extraction kit (catalog number ZP303-1) produced by Zhuangmeng International Biotechnology Co., Ltd.

[0089] The 16S ribosomal RNA sequence of BZ109 was then amplified using the universal primers for bacterial molecular identification, 16S–27F (5'-AGAGTTTGATCTGGCTCAG-3′) and 16S-1492R (5'-TACGGCTACCTTGTTACGACTT-3′). After purification, the amplified sequence was sequenced by Shanghai Sangon Biotech. The obtained BZ109 16S ribosomal RNA sequence is shown in SEQ ID NO.1.

[0090] Alignment analysis using the EzBioCloud 16S database revealed that the BZ109 16S ribosomal RNA sequence showed the highest similarity (99.71%) to the Streptomyces varsoviensis 16S rRNA sequence. Since the BZ109 16S ribosomal RNA also showed high sequence similarity to other Streptomyces species besides Streptomyces varsoviensis, phylogenetic analysis was performed on the top 15 Streptomyces species with the highest similarity to the BZ109 16S ribosomal RNA in the EzBioCloud 16S database, resulting in the following phylogenetic tree: Figure 9 As shown in the figure, BZ109 still clusters with Streptomyces varsoviensis, therefore BZ109 is identified as Streptomyces varsoviensis.

[0091] Example 3

[0092] This embodiment discloses the preparation process of a biological agent based on Streptomyces varsoviensis BZ109 (hereinafter referred to as "strain BZ109") and its effect on inhibiting mold.

[0093] In this embodiment, the plate confrontation method was used to evaluate the antibacterial activity of the isolated and purified strain BZ109. Specifically, this included:

[0094] PDA culture medium was poured into a 9mm diameter sterile petri dish to prepare PDA solid culture medium plates.

[0095] Place a block of mycelial material (d = 8 mm) of pathogens (Fusarium oxysporum, Rhizoctonia solani, Fusarium graminearum, and Phytophthora sacchari) in the center of a PDA plate. On the same plate, titrate 5 μl of Streptomyces isolate suspension at a distance of 2.5 cm from the pathogen mycelial block. Incubate the plate at 28°C for 3–7 days and observe the inhibition of pathogen mycelial growth. Figure 10 The experimental results of this embodiment are shown. The left side of the figure represents the control group, and the right side represents the experimental group containing strain BZ109. As can be seen from the figure, strain BZ109 isolate exhibits excellent antibacterial activity, significantly inhibiting the mycelial growth of *Phytophthora sojae*, *Rhizoctonia solani*, *Fusarium oxysporum*, and *Fusarium graminearum*. In particular, it shows excellent inhibitory effects against *Phytophthora sojae*, *Rhizoctonia solani*, and *Fusarium oxysporum*. The figure shows that strain BZ109 isolate achieved the best inhibition rate against these fungi, reaching nearly 100% inhibition efficiency.

[0096] Example 4

[0097] In this embodiment, Phytophthora soybeanis was used as a model plant pathogen to further evaluate the antibacterial activity of strain BZ109.

[0098] This study specifically evaluated the antifungal activity of strain BZ109 against *Phytophthora soybeanae*. The evaluation method used was to assess the antifungal activity of BZ109 fermentation broth against *Phytophthora soybeanae*. The specific steps included:

[0099] Step 1: Pick the cultured BZ23 colonies and put them into 50ml of sterilized Gao's No. 1 liquid culture medium. Incubate at 28℃ and 180rpm / min for 7 days to obtain BZ23 fermentation broth.

[0100] Step 2: Centrifuge the fermentation broth at 6000×g at 4℃ for 10 min, and filter it through a 0.22μm filter membrane to obtain the BZ109 culture filtrate.

[0101] Step 3: Mix different volumes of culture filtrate with molten PDA to prepare culture filtrate PDA plates with concentrations of 1%, 5%, 10% and 20% (v / v).

[0102] Step 4: Using a PDA plate without culture filtrate as a control, place a block of Phytophthora soybean mycelium (8 mm in diameter) in the center of the PDA plate and incubate at 28°C for 3 days.

[0103] Step 5: Then measure the radial growth diameter of the hyphae and calculate the antibacterial activity of the culture filtrate. The formula is: Inhibition rate (%) = [(growth diameter of control group - growth diameter of treatment group) / growth diameter of control group] × 100%.

[0104] The results obtained are as follows Figure 11 As shown, Figure 11 The figure illustrates the inhibitory effect of different concentrations of BZ109 culture filtrate on the mycelial growth of *Phytophthora sojae* in this embodiment. As can be seen from the figure, the inhibition rate of *Phytophthora sojae* was over 12% with 1% BZ109 fermentation broth, 40% with 5% BZ109, over 78% with 10% BZ109, and over 98% with 20% BZ109. The efficiency of inhibiting *Phytophthora sojae* mycelial growth increased with increasing concentration of BZ109 fermentation broth in the PDA medium.

[0105] Example 5

[0106] In this embodiment, a pot experiment was used to evaluate the inhibitory effect of the fermentation broth of strain BZ109 on *Phytophthora sojae*. Specific steps included:

[0107] Step 1: Select 4 chili pepper plants with a height of about 10cm and uniform growth, and divide them into two groups, one as the control group and the other as the treatment group. Figure 12 The four chili pepper plants selected in this embodiment are shown. The left side is the control group, and the right side is the chili pepper plant treated with strain BZ109.

[0108] Step 2: Dilute the BZ109 fermentation liquid 5 times and apply it to the leaves and roots of the treated plants. The amount of spray should be enough to form a layer of water mist on the chili leaves, without the fermentation liquid dripping from the leaves. The amount of root drenching is 50ml per chili plant.

[0109] The control plants were sprayed and drenched with water, with the spraying and drenching amounts being the same as those in the treatment group.

[0110] Step 3: 24 hours later, inoculate the middle leaves of the pepper plant with Phytophthora soybean mycelium blocks (diameter = 8mm), and at the same time, inoculate the nutrient substrate at four locations 2cm away from the base of the pepper stem with Phytophthora soybean mycelium blocks (diameter = 8mm).

[0111] The plants were kept moist, and the disease status of the peppers was observed 7 days later.

[0112] The final result is as follows Figure 13 As shown, no obvious disease symptoms were observed in the plants after spraying and root irrigation with the fermentation liquid of strain BZ109, while the control group showed symptoms of yellowing, wilting and dropping of leaves, indicating that the fermentation liquid of strain BZ109 can effectively inhibit the infection of soybean Phytophthora infestans.

[0113] Example 6

[0114] In this embodiment, the antifungal activity of the fermentation broth of strain BZ109 against gray mold was tested. Specific steps included:

[0115] Step 1: Select 8 chili pepper plants with a height of about 10cm and uniform growth, and divide them into two groups, one as the control group and the other as the treatment group.

[0116] Step 2: Dilute the BZ109 fermentation liquid 5 times and apply it to the leaves and roots of the treated plants. The amount of spray should be enough to form a layer of water mist on the chili leaves, without the fermentation liquid dripping from the leaves. The amount of root drenching is 50ml per chili plant.

[0117] The control plants were sprayed and drenched with water, with the spraying and drenching amounts being the same as those in the treatment group.

[0118] Step 3: 24 hours later, each pepper plant in both the treatment and control groups was inoculated with 5 ml of solution containing 10... 7 Botrytis cinerea (the pathogen of gray mold) spores / ml. The plants were treated with moisture retention, and the disease status was observed after 7 days.

[0119] The final result is as follows Figure 14 As shown in the figure, the control group showed lesions, while the leaves of the plants treated with BZ109 fermentation liquid showed no obvious symptoms, indicating that BZ109 also has a good control effect on gray mold.

[0120] Example 7

[0121] In this embodiment, *Raulella ovale* was selected as the model bacterium for bacterial wilt of plants to evaluate the inhibitory activity of BZ109 against the pathogen. The specific steps are as follows:

[0122] Add 4% OD to molten LB solid medium (approximately 40-50°C). 600 A 0.6% concentration of *Rahus oryzae* bacterial suspension was poured into plates and cooled. Oxford cups were then placed on LB agar containing *Rahus oryzae*, and BZ109 fermentation filtrate diluted 5-fold was added to the Oxford cups. The plates were incubated overnight at 37°C, and the size of the inhibition zone was observed the next day. Results are as follows: Figure 15 As shown in the figure, the BZ109 fermentation broth diluted 5 times has a significant inhibitory effect on Raulella oxypetalum.

[0123] Example 8

[0124] In this embodiment, the effect of strain BZ109 on plant growth was tested.

[0125] Eight cucumber seedlings with four leaves and uniform growth were selected and divided into two groups: one group as the control and the other as the treatment group.

[0126] Dilute the BZ109 fermentation liquid five times and apply it to the leaves and roots of the treated plants. The amount sprayed should be enough to form a fine mist on the chili leaves without dripping. For root drenching, use 50 ml per plant. The control plants were treated with water. One week later, repeat the foliar spraying and root drenching treatment, using the same amounts as the first time.

[0127] Starting from the second treatment, observe the growth of the cucumber seedlings weekly. The growth status on day 14 after treatment is as follows: Figure 16 As shown in the figure, the cucumber seedlings treated with BZ109 fermentation liquid were significantly taller than those in the control group, and the cucumber tendrils in the treatment group grew earlier than those in the control group.

[0128] The growth status on day 21 after treatment is as follows: Figure 17 As shown in the figure, the cucumber plants treated with BZ109 fermentation broth flowered earlier than the control group. This indicates that BZ109 fermentation broth treatment has a significant effect on promoting cucumber growth and advancing flowering.

[0129] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A strain of Streptomyces BZ109, wherein the classification name of Streptomyces BZ109 is... Streptomyces varsoviensis BZ109 was deposited at the China Center for Type Culture Collection on August 5, 2024, with accession number CCTCC NO: M20241749.

2. The Streptomyces BZ109 according to claim 1, characterized in that, The 16S rRNA sequence of Streptomyces BZ109 is shown in SEQ ID NO.

1.

3. The Streptomyces BZ109 according to claim 1, characterized in that, After being cultured on potato dextrose agar at 28°C for 7 days, the Streptomyces BZ109 produced aerial hyphae and substrate hyphae on the medium. It did not secrete pigments. The aerial hyphae were chalky white with a light gray ring around them, and the colony edges were relatively neat.

4. A biological agent, characterized in that, The biological agent includes Streptomyces BZ109 as described in claim 1.

5. The application of Streptomyces BZ109 according to claim 1 or the biological agent according to claim 4 in inhibiting Phytophthora in soybean.

6. The use of Streptomyces BZ109 according to claim 1 or the biological agent according to claim 4 in inhibiting Rhizoctonia solani.

7. The use of Streptomyces BZ109 according to claim 1 or the biological agent according to claim 4 in inhibiting Fusarium oxysporum.

8. The use of Streptomyces BZ109 according to claim 1 or the biological agent according to claim 4 in inhibiting Fusarium graminearum.

9. The role of Streptomyces BZ109 according to claim 1 or the biological agent according to claim 4 in the control of plant diseases, wherein the plant disease is gray mold of pepper plants, and the gray mold of pepper plants is caused by Botrytis cinerea spores.

10. The application of Streptomyces BZ109 according to claim 1 or the biological agent according to claim 4 in promoting the growth of cucumber seedlings.

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