Streptomyces alboflavinus SC-3 and its composition and use

Abstract

The present invention discloses Streptomyces SC-3 and its composition and use. The Streptomyces SC-3 strain is deposited in China Center for Type Culture Collection with the deposit number CCTCC NO:M 2024906. The present invention finds that the Streptomyces SC-3 strain itself has high efficiency and broad-spectrum antibacterial activity, and finds that the Streptomyces SC-3 strain has a significant antagonistic effect on kiwifruit soft rot bacteria. It is verified by indoor experiments that the speed of kiwifruit fruit decay caused by Phomopsis can be slowed down. Its fermentation liquid has good temperature stability, and a variety of antibacterial substances are identified from its sterile fermentation liquid, including antibiotics such as antimycin, tetramycin, candidacidin, streptomycin, etc., which are widely used in biological control. The speed of fruit decay caused by the infection of Botrytis cinerea after inoculation can be effectively inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field related to biological agriculture, and in particular relates to a new strain and its aseptic fermentation product, and its use in biological control of plant diseases. Background Art

[0002] Kiwifruit (Actinidia chinensis) belongs to the genus Actinidia in the family Actinidia, and is a perennial and dioecious vine. Rich in nutrients such as vitamin C, minerals, dietary fiber, and antioxidants, kiwifruit has received high attention for its essential nutrients and health benefits, and has long been known as the "king of fruits" and is deeply loved by the public.

[0003] After harvest, kiwifruit is prone to becoming soft and rotten during storage, transportation and sales, which can cause serious economic losses and potential food safety issues. Soft rot is a serious disease caused by fungal infection. The main pathogens causing kiwifruit soft rot are Botryosphaeria dothidea, Alternaria alternata, Phomopsis spp., Penicillium expansum, Botrytis cinerea, etc. Soft rot caused by Botryosphaeria dothidea is one of the most prominent diseases affecting kiwifruit after harvest. When the disease occurs, the skin of the infected fruit becomes concave and soft, with milky white flesh in the center of the disease, and it completely rots after 6-10 days.

[0004] At present, the prevention and control of kiwifruit soft rot is mainly chemical fungicides. Long-term use of these fungicides may lead to resistance of pathogens, fungicide residues, and environmental pollution. Therefore, there is an urgent need to develop an effective strategy for the prevention and control of kiwifruit soft rot with natural products.

[0005] The use of microorganisms and their metabolites to control fruit diseases is a promising approach. Microorganisms and their metabolites are the source and inspiration for the development of new green pesticides to control plant pathogens. Streptomyces is a Gram-positive filamentous fungus that can produce a variety of natural secondary metabolites with important economic significance. The application potential of Streptomyces in agriculture is huge. Since the discovery of Streptomyces, many species that can inhibit pathogens have been found, and some have been developed into commercial products and widely used. Biological control has become an effective measure for safe and effective prevention and control of diseases in agricultural production, and has broad development prospects. Summary of the invention

[0006] The present invention aims to provide Streptomyces alboflavinus SC-3 and a composition and use thereof, in particular, use of the sterile fermentation liquid of Streptomyces alboflavinus SC-3 in preventing and controlling kiwifruit soft rot.

[0007] According to the first main aspect of the present invention, a strain of Streptomyces albidoflavus is provided, which is classified and named Streptomyces albidoflavus SC-3, with a preservation number of CCTCC NO: M2024906, a preservation date of May 11, 2024, and a preservation unit of China Center for Type Culture Collection (address: Wuhan University, Wuhan, China, zip code: 430072, telephone: 027-68754052). The test result on May 18, 2024 was: survival.

[0008] Furthermore, the Streptomyces alboflavinus SC-3 strain has a 16S rDNA sequence shown in SEQ ID NO: 1. The strain can be isolated from the rhizosphere soil of healthy kiwifruit.

[0009] According to the second main aspect of the present invention, there is provided a composition comprising the aforementioned Streptomyces alboflavinus SC-3 strain or its metabolites, and may also include necessary adjuvants or carriers. These adjuvants or carriers include but are not limited to one or a combination of two or more of the following:

[0010] Surfactant: Increase the adhesion of fermentation liquid on the plant surface and improve its bioavailability.

[0011] Stabilizer: Prevents the active ingredients in the fermentation broth from decomposing or becoming inactive, thus prolonging their effective time.

[0012] Dispersant: Ensure that the fermentation broth is evenly dispersed before final use to avoid local concentrations that are too high or too low.

[0013] Sustained-release agent: controls the release rate of active ingredients in the fermentation broth so that it continues to work over a period of time.

[0014] Solvent or diluent: Adjust the concentration of the fermentation broth to make it suitable for field application.

[0015] Preservatives: protect the composition from microbial contamination during storage.

[0016] pH adjuster: adjusts the pH of the fermentation broth to optimize its biological activity.

[0017] Nutritional additives: provide nutrients required for microbial growth and enhance their biological activity.

[0018] Carrier material: such as starch, clay or other porous materials, used to adsorb and carry the fermentation liquid.

[0019] Emulsifiers: If the fermentation broth needs to be made into an emulsion, emulsifiers can help form a stable emulsion.

[0020] Thickener: Increases the viscosity of the fermentation liquid, making it easier to form a protective film on the surface of plants.

[0021] Antioxidant: Prevents the active ingredients in the fermentation broth from becoming ineffective due to oxidation.

[0022] Penetrants: Help the fermented liquid to better penetrate into plant tissues, improving its therapeutic effects.

[0023] Adsorbent: such as activated carbon or other porous materials, used to adsorb and enrich active ingredients in the fermentation broth.

[0024] Protective colloid: forms a protective layer to reduce the impact of environmental factors on the active ingredients in the fermentation broth.

[0025] As a preferred embodiment of the present invention, the metabolites of Streptomyces alboflavinus SC-3 strain include sterile fermentation broth.

[0026] Those skilled in the art should know that the metabolites produced by different strains are diverse and can exert antibacterial effects against specific pathogens. Sterile fermentation broth is usually produced through fermentation engineering. It involves the biological transformation of microorganisms, converting nutrients in the culture medium into useful metabolites.

[0027] Compared with cell supernatant (CFS), the bacteria in the fermentation broth are usually inactivated and used directly, which reduces the dependence on selective culture media. Therefore, the antibacterial activity of the sterile fermentation broth can be utilized, which can reduce or replace the use of chemical preservatives.

[0028] Furthermore, the sterile fermentation broth is a product obtained by culturing Streptomyces alboflavinus SC-3 in PSB medium for 9 days.

[0029] According to the third main aspect of the present invention, there is provided a method for preparing the aforementioned sterile fermentation broth by using the Streptomyces alboflavin SC-3 strain, comprising at least the following steps: inoculating the strain SC-3 into PSB culture medium, culturing at set temperature and rotation speed conditions for at least 9 days, centrifuging the supernatant and filtering it with a sterile microporous filter membrane to obtain a cell-free supernatant.

[0030] In a possible embodiment, the method comprises the following steps: inoculating strain SC-3 into PSB medium, culturing at 28° C. and 180 rpm for 9 days, centrifuging and filtering the supernatant with a 0.22 μm sterile microporous filter membrane to obtain a cell-free supernatant.

[0031] According to a fourth main aspect of the present invention, there is provided a use of a composition containing metabolites of Streptomyces alboflavinus SC-3 strain in controlling plant diseases, wherein the composition acts as an antibacterial active substance.

[0032] Among them, the aforementioned plant diseases include kiwifruit soft rot.

[0033] Furthermore, the composition has an antagonistic effect on Botrytis cinerea, Phomopsis spp., Alternaria alternata, Fusarium spp., Fusarium spp., Melanosporium spp., American-Australian drupe brown rot, Alternaria spp., Rice blast fungus, Rhizoctonia solani, American-Australian drupe chain sclerotinia, and Verticillium spp.

[0034] In particular, the Streptomyces alboflavinus SC-3 strain is more suitable for producing antibacterial active substances when cultured in PSB medium for 9 days, and its sterile filtrate has a good inhibitory effect on B. dothidea., Phomopsis sp., and A. alternate, with the inhibition rates being 87.06%, 64.%, and 71.08%, respectively.

[0035] In the above application, the aseptic filtrate of Streptomyces SC-3 with a content of 10% is used for biological control of soft rot of kiwifruit, which can slow down the decay speed of kiwifruit caused by Botrytis cinerea.

[0036] Advantages and beneficial effects of the present invention:

[0037] The present invention finds that the Streptomyces SC-3 strain itself has high efficiency and broad-spectrum antibacterial activity, and finds that the Streptomyces SC-3 strain has a significant antagonistic effect on kiwifruit soft rot bacteria. It is verified by indoor experiments that the speed of kiwifruit fruit decay caused by Phomopsis can be slowed down. Its fermentation liquid has good temperature stability, and a variety of antibacterial substances are identified from its sterile fermentation liquid, including antibiotics such as antimycin, tetramycin, candidacidin, streptomycin, etc., which are widely used in biological control. It can effectively inhibit the speed of fruit decay caused by Botrytis cinerea infection after live inoculation, indicating that the strain has broad application prospects in the field of biological control of plant diseases, and also has extremely high development value in the development of biological control agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0039] Figure 1 The colony morphology of Streptomyces alboflavinus SC-3 in one embodiment of the present invention is shown;

[0040] Figure 2The figure shows the inhibitory effect on Botrytis cinerea in one embodiment of the present invention;

[0041] Figure 3 The morphological characteristics, physiological and biochemical characteristics and carbon source utilization characteristics of one embodiment of the present invention on different culture media are shown;

[0042] Figure 4 The SC-3 phylogenetic tree constructed using the MEGA software neighbor method in one embodiment of the present invention is shown;

[0043] Figure 5 A diagram showing the inhibitory effect of fermentation broths cultured in different liquid culture media on Botrytis cinerea in one embodiment of the present invention;

[0044] Figure 6 The figure shows the inhibitory effect of different days of culturing on Botrytis cinerea in PSB medium in one embodiment of the present invention;

[0045] Figure 7 The figure shows the inhibitory effect of Streptomyces alboflavinus SC-3 and sterile filtrate on plant pathogenic fungi in one embodiment of the present invention;

[0046] Figure 8 The effect of sterile fermentation liquid on the growth of Botrytis cinerea in one embodiment of the present invention is shown;

[0047] Fig. 9 The graph shows the antibacterial activity of the aseptic fermentation liquid of the strain against Botrytis cinerea after being treated at different temperatures in one embodiment of the present invention;

[0048] Fig.10 The figure shows the biocontrol effect of the fermentation liquid on the kiwifruit soft rot caused by Botrytis cinerea in one embodiment of the present invention. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings so that the purpose, features and advantages of the present invention can be more clearly understood. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solution of the present invention.

[0050] In the following description, certain specific details are set forth for the purpose of illustrating the various disclosed embodiments to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details. In other cases, well-known devices, structures, and techniques associated with the present application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0051] References throughout the specification to "one embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "in one embodiment" or "in an embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0052] like Figure 1 As shown, the Streptomyces albidoflavus SC-3 of the present invention has been deposited in China Center for Type Culture Collection (Address: Wuhan University, Wuhan, China, Postal Code: 430072, Tel: 027-68754052) on May 11, 2024, with a deposit number of CCTCC NO: M 2024906. The following is a detailed description of several aspects.

[0053] 1 Isolation and identification of biocontrol strains:

[0054] 1.1 Isolation and screening of biocontrol strains: Soil samples were collected from a kiwi fruit planting base in Shuicheng District, Liupanshui City, Guizhou Province, China. The isolation and screening steps are as follows:

[0055] Soil was randomly collected from 10-20 cm of the rhizosphere of kiwifruit, the soil samples were mixed, stored at -20 °C, and 10 g of soil sample was added to 90 mL of sterile water and cultured at 28 °C and 180 rpm for 1 h.

[0056] The homogenate was serially diluted to 10 -2 , 10 -3 , 10 -4 , 10 -5 , spread 150 μL on Gao's No. 1 agar medium and culture at 28°C for 7 days.

[0057] Each colony was purified on Gao's medium No. 1, and 21 actinomycetes with different morphological characteristics were isolated from the rhizosphere soil of kiwifruit. The antagonistic activity of the isolated strains was evaluated by plate confrontation method. It was found that SC-3 had a strong inhibitory effect on Botrytis cinerea, with an inhibition rate of 75.30% ( Figure 2 ).

[0058] 1.2 Identification of biocontrol strains:

[0059] Physiological and biochemical characteristics: The physiological characteristics of strain growth were determined according to the method of the "Streptomyces Identification Manual".

[0060] like Figure 3As shown in the figure, Streptomyces SC-3 can grow on 7 specific culture media, and grows better on Gao's No. 1, ISP1, ISP4 and ISP6 culture media. The aerial hyphae are light yellow on ISP2 culture media, grayish white on ISP4, ISP5 and ISP7 culture media, and white on SP1, ISP3 and ISP6 culture media. The strain cannot produce soluble pigments. The short rod-shaped spores of strain SC-3 were observed by scanning electron microscopy.

[0061] Physiological and biochemical tests showed that the strain can liquefy gelatin, coagulate milk, hydrolyze starch, and produce urease and lipase, but cannot decompose cellulose, produce hydrogen sulfide and melanin. It can also utilize eight carbon sources (glucose, fructose, sucrose, maltose, lactose, sorbitol, arabinose, cellobiose, and mannitol) to produce cellulose. Figure 3 ).

[0062] 16S rDNA identification of strain SC-3: strain M-1 was transferred to Gao's liquid medium and cultured at 28°C and 180 rpm on a shaker for 3 days. Mycelia were collected by centrifugation at 12000 rpm for 30 min, washed three times with sterile water, and DNA was extracted using the TIANamp bacterial DNA kit (Tiangen Biotechnology Co., Ltd., Beijing, China). The extracted DNA was used as a template for PCR amplification using universal primers 27F (5′-AGAGTTTTGATCCTGGCTCAG-3′) and 1492R (:5′-GGTTACCTTGTTACGACTT-3′).

[0063] The reaction system was: 1 μL DNA template, 10 μL 2× Taq Master Mix, 0.4 μL each of forward and reverse primers and 8.2 μL ddH2O, and the PCR amplification program was: pre-denaturation at 95°C for 5 min, denaturation at 94°C for 30 s, annealing at 56°C for 30 s, extension at 72°C for 30 s, and final extension at 72°C for 10 min, for 35 cycles.

[0064] The PCR products were sequenced by Sangon Biotech Co., Ltd. and analyzed by blast in NCBI database. The phylogenetic tree of 16S rDNA sequences of strain M-1 and its close relatives was constructed by neighbor-joining method in MEGA7.0.

[0065] A 1412pb 16S rRNA sequence was amplified from strain SC-3 and submitted to NCBI for comparison. The accession number is PP663758. The sequence is clustered with Streptomyces albidoflavus, with a similarity of 90% ( Figure 4). Combining its phenotypic, physiological and biochemical characteristics, strain SC-3 was identified as Streptomyces albidoflavus.

[0066] 2 Screening of the optimal fermentation medium for strain SC-3: The spore suspension was inoculated with 10 culture media at an inoculation rate of 1%: PDB medium, NB medium, LB medium, PSB medium, Gao's medium No. 1, Am6 medium, Bennett medium, F2 medium, Czapek medium, and YEME medium (see the attached table for the culture medium formula). After shaking and culturing at 28°C and 180 rpm for 5 days, the culture was centrifuged at 4000 rpm / min for 30 min. The supernatant was filtered three times with a 0.22 μm sterile microporous filter membrane (SCAA-104, ANPEL, Shanghai, China) to obtain a filtrate without bacteria (Zhang et al., 2020).

[0067] The sterile filtrate and PDA were mixed thoroughly at a volume ratio of 1:9 and poured into the plate. After cooling, a 6mm Botrytis ciliate cake was inoculated in the center of the plate. The same volume of sterile water was used as a control to determine the mycelial growth inhibition rate of different sterile fermentation broths. The mycelial growth inhibition rate was calculated according to the following formula:

[0068]

[0069] The results showed that the sterile fermentation broth of PSB medium had the best antibacterial effect on Botrytis cinerea, reaching 85.80% ( Figure 5 ).

[0070] 3 Screening of the optimal fermentation time of strain SC-3: The antagonistic strain was inoculated at a 2% inoculation size into 12 150 mL Erlenmeyer flasks containing 50 mL PSB medium, and cultured in a shaking incubator at 28 °C and 160 rpm / min for 1 to 12 days. 50 mL of sterile fermentation broth was taken every 24 hours to evaluate its antibacterial rate against Botrytis cinerea, and the antibacterial activity of the sterile fermentation broth against Botrytis cinerea was determined at different times.

[0071] The results showed that the antibacterial activity of the aseptic fermentation liquid of strain SC-3 reached the highest level on the 9th day of culture, with an antibacterial rate of 88.22% ( Figure 6 ).

[0072] 4 Broad-spectrum antifungal activity of strain SC-3: The antagonistic activity of the biocontrol fungus SC-3 was evaluated by the plate confrontation method. 6 mm cakes of Botrytis cinerea, Phomopsis spp., Alternaria alternifolia, Fusarium trilineata, Fusarium spp., American-Australian drupe brown rot, Alternaria longibotia, Magnaporthe oryzae, Rhizoctonia solani, American-Australian drupe chain disc, and Verticillium raphis were inoculated in the center of the PDA plate, and filter paper pieces (6 mm) containing SC-3 bacterial solution were inoculated at four symmetrical points 2.5 cm away from the center of the plate.

[0073] The broad-spectrum antifungal activity of the aseptic fermentation broth of strain SC-3 was detected by the toxin-carrying plate method. 5 mL of CFS was added to 45 mL of PDA at 50 °C, mixed and poured into the plate. After cooling, the pathogenic fungus cake (6 mm) was inoculated in the center of the plate and cultured in the dark in a constant temperature box at 28 °C for 5 days.

[0074] The results showed that the strain SC-3 and its sterile fermentation broth showed significant antibacterial activity against the selected pathogenic fungi ( Figure 7 ).

[0075] 5 Effect of aseptic fermentation broth of strain SC-3 on the growth of Botrytis cinerea: strain SC-3 was inoculated into PSB medium, cultured at 28°C, 180rpm for 9 days, and the supernatant was centrifuged and filtered with a 0.22μm sterile microporous filter to obtain a cell-free supernatant. The inhibitory effect of aseptic fermentation broth diluted 10 times, 50 times, 100 times, 200 times, 300 times, and 400 times on Botrytis cinerea was determined. A 6mm B. dothidea cake was added to a 250mL conical flask containing 100mL potato dextrose broth (PDB) medium and cultured at 28°C, 180rpm for 3 days.

[0076] Weigh 0.2 g of equal amount of wet weight of mycelium and inoculate it into a conical flask, add it to PDB medium containing 10×, 50×, 100×, and 200× diluted sterile fermentation broth, and add an equal amount of sterile water as a control. After culturing at 28°C for 2d and 4d, respectively, filter and wash with sterile water 2-3 times, dry in an oven at 80°C, weigh and record the dry weight of the mycelium.

[0077] The results showed that as the concentration of the sterile fermentation broth increased, its antibacterial activity also increased. When the sterile fermentation broth of Streptomyces SC-3 was diluted 10 times, the inhibition rate of Botrytis cinerea on the 3rd day was 89.02%, and the sterile fermentation broth diluted 400 times still had an inhibitory effect on Botrytis cinerea. The sterile fermentation broth diluted 10 times had the strongest inhibitory effect on the dry weight of pathogenic mycelium, with inhibition rates of 86.57% and 94.98% on the 2nd and 4th days, respectively. The sterile fermentation broth diluted 10 times, 50 times, 100 times and 200 times significantly inhibited the growth of mycelium, and the dry weight of mycelium was significantly lower than that of the control group ( Figure 8 ).

[0078] 6. Sensitivity of the fermentation broth of strain SC-3 to temperature: The aseptic fermentation broth of strain SC-3 was placed at -80℃, -20℃, 0℃, 80℃, and 121℃ for 1h. The results showed that the aseptic fermentation broth of strain M-1 had certain stability at different temperatures. After high temperature treatment, the antibacterial activity of the aseptic fermentation broth of the bacteria was reduced, but it still had antibacterial activity. Except for 121℃, there was no significant difference in the antibacterial activity of the aseptic fermentation broth treated at other temperatures ( Fig. 9 ).

[0079] 7 Biocontrol effect of SC-3 strain fermentation liquid on soft rot under live inoculation conditions: Take healthy kiwifruit, disinfect the surface with 75% alcohol, wash three times with sterile water, dry naturally on a sterile operating table, put it in an alcohol-sterilized fresh-keeping box, filter the actinomycete fermentation liquid with a 0.22μm filter membrane to make a sterile fermentation filtrate, and set the sterile fermentation liquid to three concentrations of 2 times, 10 times and undiluted, respectively, and put the sterilized kiwifruit into beakers containing fermentation liquid of different concentrations.

[0080] The control was treated with sterile water, soaked for 5 minutes and then taken out to dry. The surface of the kiwifruit was pierced with a sterile syringe, and a 7mm Botrytis ciliate cake was inoculated at the puncture site. The kiwifruit soaked in sterile water and inoculated with the cake was used as the control group. Each group was treated with 4 replicates. The kiwifruit was placed in a fresh-keeping box and placed in an artificial climate chamber. During the culture period, the kiwifruit was moisturized with fermentation liquid or sterile water of different concentrations. The disease condition of the kiwifruit was observed regularly, the diameter of the lesions of each treatment was recorded, and the incidence rate was calculated.

[0081]

[0082] The results showed that the kiwifruit inoculated with Botrytis cinerea was treated with different concentrations of sterile fermentation liquid. On the 11th day after inoculation with Botrytis cinerea, the incidence rates of kiwifruit were 51.11%, 35.57% and 28.57%, respectively. It can be seen that the diameter of the lesions decreased with the increase of the concentration of sterile fermentation liquid, indicating that the sterile fermentation liquid of strain SC-3 can delay the occurrence of kiwifruit soft rot ( Fig.10 ).

[0083] SEQ ID NO: 1:

[0084]

[0085] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

[0086] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. Streptomyces alboflavin SC-3 strain, which is deposited in China Center for Type Culture Collection with the deposit number CCTCC NO: M 2024906.

2. The Streptomyces alboflavin SC-3 strain according to claim 1, which has the 16S rDNA sequence shown in SEQ ID NO:

1.

3. A composition comprising the Streptomyces alboflavinus SC-3 strain according to claim 1 or 2.

4. A method for preparing a sterile fermentation liquid by using the Streptomyces alboflavinus SC-3 strain according to claim 1 or 2, characterized in that: The method comprises the following steps: inoculating the SC-3 strain into a PSB culture medium, culturing for at least 9 days under set temperature and rotation speed conditions, centrifuging and taking the supernatant, and filtering the supernatant with a sterile microporous filter membrane to obtain a cell-free supernatant.

5. Use of the composition according to any one of claims 3 as an antibacterial active substance in the prevention and control of plant diseases; the pathogens of the plant diseases are Botrytis cinerea, Phomopsis spp., Alternaria alternata, Fusarium spp., Fusarium spp., Fusarium spp., brown rot of American and Australian drupes, Alternaria spp., Rice blast fungus, Rhizoctonia solani, Sclerotinia spp. of American and Australian drupes, and Verticillium spp.

6. The use according to claim 5, characterized in that The plant diseases include kiwifruit soft rot.

7. The use according to claim 5 or 6, characterized in that The composition has antagonistic effects on Botrytis cinerea, Phomopsis spp., Alternaria alternata, Fusarium trilineata, Fusarium spp., American-Australian drupe brown rot, Alternaria longibotium, rice blast fungus, Rhizoctonia solani, American-Australian drupe chain sclerotinia, and Verticillium raphis.

8. The use according to claim 6, characterized in that The invention comprises using a 10% sterile filtrate of Streptomyces alboflavinus for biological control of soft rot of kiwifruit.

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