Marine streptomyces OUC-HL1638 with low temperature and saline-alkaline tolerance and application thereof

Abstract

The application belongs to the technical field of microorganism and soil improvement, and particularly relates to a low-temperature and salt-tolerant marine streptomyces OUC-HL1638 and application thereof. The preservation number of the strain OUC-HL1638 is CGMCC No. 36765. The application forms include the strain itself, a bacterial suspension, a fermentation product, a volatile gas or an extract, etc. The strain can maintain the production of active substances under high salt and alkali conditions, and has the functions of salt and alkali tolerance, low-temperature tolerance and surface activity. When the strain is applied to the prevention and treatment of diseases caused by fusarium oxysporum, the plant diseases such as radish seedling blight and cherry tomato blight can be effectively prevented and treated in a salt and alkali environment or under low-temperature conditions, and the strain itself has no influence on the ecological environment, thus solving the problems of low efficiency and great harm to the environment caused by chemical pesticides.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology and soil improvement technology, specifically involving a marine streptomyces strain OUC-HL1638 that is resistant to low temperature and salt and alkali and its application. Background Technology

[0002] Against the backdrop of global climate change and intensive agricultural development, soil salinization and Fusarium ( ) Fusarium spp. The combined stress of fungal diseases has become a key bottleneck restricting the productivity and sustainability of agriculture in saline-alkali land. Diseases such as Fusarium wilt and root rot caused by Fusarium are more likely to break out and spread under saline-alkali stress, leading to severe crop yield reduction or even crop failure.

[0003] Currently, agricultural production mainly relies on chemical fungicides to control this disease. However, long-term and excessive use of chemical agents can lead to increased drug resistance in pathogens, soil microecological imbalance, and excessive pesticide residues in agricultural products, seriously threatening ecological and environmental safety and agricultural product quality. To avoid these problems, existing research has adopted biological control methods to improve saline-alkali land. Biological control methods are economical, effective, and environmentally friendly.

[0004] Streptomyces are widely distributed in soil, seawater, and extreme environments, and are important biocontrol microorganisms. They produce a variety of secondary metabolites with antibacterial activity, showing significant potential in the field of agricultural biological control. Recent studies have found that some Streptomyces metabolites also possess surface-active functions, reducing liquid surface tension, forming a thin film on plant surfaces, and enhancing wettability. This promotes the spread and adhesion of antibacterial components, achieving synergistic effects through a dual mechanism of "bactericidal and spreading" action. This characteristic holds promise for overcoming the drawback of uneven distribution of chemical pesticides, which necessitates higher dosages, and provides a new approach for developing environmentally friendly biocontrol agents. However, most Streptomyces have limited colonization capacity under saline-alkali stress. By selecting and optimizing strains and fermentation processes, screening for superior strains that are salt-tolerant and possess the aforementioned functions can further expand their application in the green control of diseases in modern agriculture, providing new microbial resources for reducing dependence on chemical pesticides and promoting sustainable agricultural development.

[0005] Currently, agriculture in saline-alkali land urgently needs a highly efficient, environmentally compatible biological control method that can adapt to high salinity and alkalinity stress. However, known microorganisms, such as Streptomyces, often struggle to colonize and function effectively under saline-alkali stress. Therefore, developing microbial strains that combine salt tolerance with highly effective resistance to Fusarium is of great practical significance and urgent application for achieving green and sustainable development in agriculture in saline-alkali land. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems existing in the prior art, and to propose a marine streptomyces strain OUC-HL1638 that is resistant to low temperature and salt and alkali and its application.

[0007] The technical solution of this invention is: This invention provides a strain of Streptomyces ( Streptomyces strain OUC-HL1638 (sp.) has the accession number CGMCC No.36765.

[0008] The present invention provides a microbial agent comprising any one or more of the following: Streptomyces strain OUC-HL1638, its bacterial suspension, fermentation broth, fermentation product, volatile gas, or extract.

[0009] The present invention also provides the application of the aforementioned Streptomyces strain OUC-HL1638 or the aforementioned inoculum in any one of A1) to A5): A1) Inhibits the growth of Fusarium oxysporum; A2) Prepare products that inhibit the growth of Fusarium oxysporum; A3) Prevention and control of plant diseases caused by Fusarium oxysporum; A4) Prevention and control of radish seedling wilt; A5) Control of plant wilt disease.

[0010] Furthermore, the plant wilt disease includes tomato wilt, and the method for controlling tomato wilt includes the following steps: Using fermentation broth of OUC-HL1638 strain, 50 mL of broth with a bacterial count of 1×10⁻⁶ was applied weekly to each cubic meter of tomato-growing soil. 6 Fermentation broth at CFU / mL.

[0011] This invention provides the application of the aforementioned Streptomyces strain OUC-HL1638 or the aforementioned bacterial agent in the preparation of biosurfactants.

[0012] This invention also provides the application of the aforementioned Streptomyces strain OUC-HL1638 or the aforementioned inoculant in the remediation of saline-alkali soils and / or the enhancement of plant salt stress tolerance.

[0013] This invention further demonstrates the application of the aforementioned Streptomyces strain OUC-HL1638 or the aforementioned inoculum in the prevention and control of plant diseases caused by Fusarium oxysporum under saline-alkali conditions, including radish seedling wilt and cherry tomato wilt.

[0014] This invention also provides the application of the aforementioned Streptomyces strain OUC-HL1638 or the aforementioned inoculant in the prevention and control of plant diseases under low-temperature conditions, wherein the plant diseases include radish seedling wilt and cherry tomato wilt caused by Fusarium oxysporum.

[0015] Furthermore, the fermentation broth of strain OUC-HL1638 showed no change in inhibitory activity against Fusarium oxysporum after being refrigerated at 4°C for 7 days.

[0016] This invention provides a combined fungicide, composed of the aforementioned Streptomyces strain OUC-HL1638 or the aforementioned fungicide, and an agricultural fungicide; the agricultural fungicide includes one or more of hymexazol, carbendazim, oxadixyl, and pyraclostrobin.

[0017] The beneficial effects of this invention are: The Streptomyces strain OUC-HL1638 provided by this invention was screened from deep-sea sediments. It can maintain the production of active substances under high salinity and alkalinity conditions, and also exhibits salt and alkali tolerance, low-temperature resistance, and surface activity. When applied to control diseases caused by Fusarium oxysporum, the strain itself has no impact on the ecological environment, solving the problems of low efficiency and significant environmental harm associated with chemical pesticides. It can effectively control plant diseases such as radish seedling wilt and cherry tomato wilt. Attached Figure Description

[0018] Figure 1 The colony growth morphology of marine streptomyces OUC-HL1638 on MS solid plates.

[0019] Figure 2 The inhibitory effect of strain OUC-HL1638 on Fusarium oxysporum W2401 was investigated.

[0020] Figure 3 This is a phylogenetic tree of strain OUC-HL1638 constructed based on the 16S rRNA gene sequence using the neighbor-joining method.

[0021] Figure 4 The study aimed to assess the control effect of Streptomyces OUC-HL1638 fermentation broth on Fusarium wilt disease in radish seedlings; UC (uninfected control) was the uninfected group, and IC (infected control) was the infected group.

[0022] Figure 5 The study aimed to assess the control effect of Streptomyces OUC-HL1638 fermentation broth on Fusarium wilt in cherry tomatoes; UC represented the uninfected group, IC the infected group, and FB the fermentation broth treatment group.

[0023] Figure 6The analysis of salt and alkali tolerance of Streptomyces OUC-HL1638 includes: (A) growth curves at different NaCl concentrations; (B) HPLC analysis of the yield of active compounds at various NaCl concentrations (gray background indicates target product); (C) growth curves under different pH conditions; and (D) HPLC analysis of the yield of active compounds at various pH conditions (gray background indicates target product). All chromatograms were detected using 210 nm UV.

[0024] Figure 7 The study investigated the control effect of Streptomyces OUC-HL1638 fermentation broth on Fusarium wilt disease in radish seedlings before and after refrigeration.

[0025] Figure 8 The inhibitory effects of four commonly used fungicides on Streptomyces OUC-HL1638 at effective concentrations of Fusarium oxysporum (left figure) are shown in the right figure. Information on the preservation of biological materials

[0026] Streptomyces ( Streptomyces sp.) OUC-HL1638 was deposited on November 25, 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. 36765. Detailed Implementation

[0027] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0029] Unless otherwise specified, any techniques or conditions not specifically described in this invention can be performed according to the conventional techniques or conditions described in literature, books, papers, etc. in this field, or according to the product instructions. Unless otherwise stated, the raw materials, reagents, or instruments used in the following examples that do not specify the manufacturer are all conventional products that can be purchased from legitimate channels or prepared by known methods.

[0030] The formula for Murashige and Skoog medium (MS medium) is: 30 g / L soybean flour, 20 g / L mannitol, 20 g / L agar powder, and distilled water as the solvent.

[0031] The formula for TSB-Y liquid culture medium is as follows: sucrose 103 g / L, yeast extract 0.5 g / L, trypsin soybean broth (TSB) 30 g / L, tryptone 1 g / L, and distilled water as the solvent.

[0032] The formula for the F2 fermentation medium is as follows: glucose 20 g / L, soluble starch 10 g / L, KH2PO4 0.5 g / L, MgSO4·7H2O 0.5 g / L, CaCO3 2 g / L, yeast extract 10 g / L, beef extract 3 g / L, corn extract 4 g / L, seawater salt 3.3 g / L, pH 7.0, and distilled water as the solvent.

[0033] The formula for PDA medium is: 6 g / L potato extract powder, 20 g / L glucose, 20 g / L agar, pH 5.6, and distilled water as the solvent.

[0034] The formula for PDB medium is: 6 g / L potato extract powder, 20 g / L glucose, and distilled water as the solvent.

[0035] The pathogenic fungus W2401 used in this invention was purchased from Beina Biotechnology Co., Ltd. Fusarium oxysporum BNCC 120618.

[0036] Example 1: Isolation, screening and identification of Streptomyces strain OUC-HL1638 (1) Isolation and screening of strains A dual-layer fast screening (DLFS) platform was established to screen strains with potential resistance to Fusarium oxysporum.

[0037] The pathogenic fungi used are Fusarium oxysporum W2401 was purchased from Beina Biotechnology Co., Ltd. The strain was activated using PDA medium, and the bacterial culture was prepared using PDB medium.

[0038] Seventy-two marine actinomycete strains, enriched and isolated from deep-sea sediments in the South China Sea, were inoculated onto F2 medium and cultured at 30°C for 7 days. The medium was then covered with a PDA soft agar layer containing Fusarium oxysporum spores. After the upper culture medium solidified and dried, the medium was cultured at 30°C for another 2 days.

[0039] By observing the formation of inhibition zones and measuring the diameter of each inhibition zone in millimeters, a target strain capable of producing active secondary metabolites against Fusarium oxysporum was screened and named OUC-HL1638.

[0040] (2) Classification and identification of strains Morphological identification and physicochemical characteristics identification: The colonies of this strain are dense, white, fluffy, and relatively dry. The strain morphology is as follows: Figure 1 As shown.

[0041] Molecular identification of the strain: Genomic DNA was extracted from the strain and used as a template for 16S rRNA amplification. The primers used were: F: 5′-AGAGTTTGATCCTGGCTCAG-3′ (SEQ ID NO. 2) R: 5′-GGTTACCTTGTTACGACTT-3′ (SEQ ID NO.3) PCR amplification was performed using primers. The PCR amplification reaction system is shown in Table 1, and the PCR amplification reaction conditions are shown in Table 2.

[0042] Table 1 PCR amplification reaction system

[0043] Table 2 PCR amplification reaction conditions

[0044] The three steps of denaturation, annealing, and extension were set for 25 cycles, and the PCR amplification product was obtained after the reaction.

[0045] The obtained PCR amplification products were detected and recovered by 1% agarose gel electrophoresis to obtain the target gene fragment of 16S rRNA.

[0046] The obtained 16S rRNA target gene fragment was sequenced by Qingke Biotechnology Co., Ltd. The sequencing results are shown in SEQ ID NO.1. The 16S rRNA sequence of the obtained OUC-HL1638 strain was compared using BLAST on the NCBI website. Based on the 16S rRNA sequence, a phylogenetic tree was constructed using MEGA 11.0 software, as follows... Figure 3 As shown. The results are displayed in conjunction with... Streptomyces amphotericinicus The 1H-SSA8 strain showed the highest sequence similarity, further confirming that this strain belongs to Streptomyces.

[0047] 16S rRNA sequence of the strain:

[0048] Streptomyces ( Streptomyces sp.) OUC-HL1638 was deposited on November 25, 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. 36765.

[0049] Example 2: Fermentation culture of strain OUC-HL1638 The fermentation process is as follows: Strain activation: The preserved Streptomyces OUC-HL1638 strain was activated and cultured on MS solid medium plates at 30°C. Spores grew after 7 days of inverted culture in an incubator.

[0050] Preparation of seed culture: Spores were scraped off with a toothpick and inoculated into a 250 mL Erlenmeyer flask containing 50 mL of TSB-Y liquid medium. The flask was then cultured for 2 days in a shaker at 28℃ and 180 rpm to obtain the seed culture.

[0051] Preparation of fermentation broth: The prepared seed liquid was inoculated into an Erlenmeyer flask containing F2 fermentation medium at a volume ratio of 2%, and fermented for 7 days in a shaker at a temperature of 28℃ and a rotation speed of 180 rpm.

[0052] Example 3: Antibacterial activity test of strain OUC-HL1638 The pathogenic fungi used are Fusarium oxysporum W2401 was purchased from Beina Biotechnology Co., Ltd. The strain was activated using PDA medium, and the bacterial culture was prepared using PDB medium.

[0053] The antibacterial activity of Streptomyces OUC-HL1638 was determined by the plate confrontation culture method.

[0054] OUC-HL1638 was inoculated on one side of F2 solid medium, and 5 mm W2401 bacterial blocks were punched from the other side. The plates were then incubated for 7 days. Plates without OUC-HL1638 served as a control. The inhibitory effect of Streptomyces OUC-HL1638 on Fusarium oxysporum W2401 was as follows: Figure 2 As shown.

[0055] The antibacterial rate is calculated using the following formula:

[0056] In the formula, DC For reference diameter, dt To handle the diameter.

[0057] The calculated inhibition rate of OUC-HL1638 against Fusarium oxysporum was 35.6%.

[0058] Example 4: Effect of OUC-HL1638 fermentation broth on the prevention and control of Fusarium wilt in radish seedlings. Fermentation broth was prepared according to the fermentation culture method of Example 2, and Streptomyces OUC-HL1638 was cultured to 1×10⁻⁶. 6 CFU / mL; and Fusarium oxysporum W2401 was cultured in liquid medium PDB until the bacterial count reached 1×10⁻⁶. 6 CFU / mL.

[0059] A six-well cell culture plate containing 30 μL of Fusarium oxysporum W2401 bacterial suspension was prepared with six gradient dilutions of fermentation broth / supernatant: 600 μL (5-fold dilution), 300 μL (10-fold dilution), 150 μL (20-fold dilution), 60 μL (50-fold dilution), 30 μL (100-fold dilution), and 6 μL (500-fold dilution). The volume was brought up to 3 mL with Murashige and Skoog medium to achieve the above-mentioned different dilutions of fermentation broth / supernatant.

[0060] Wells containing only W2401 bacterial suspension and culture medium were classified as infected group (IC), and wells containing only culture medium were classified as uninfected group (UC).

[0061] Radish seeds were soaked overnight and disinfected with 1% sodium hypochlorite solution for 20 minutes. After rinsing three times with sterile water, they were placed in a clean bench under UV light for 30 minutes and then dried. 3-5 seeds were gently placed in the prepared culture medium. The plates were incubated at 28℃ for three days, and the seedling height after germination was recorded.

[0062] The results are as follows Figure 4 As shown, when 30 μL of fermentation broth was added (100-fold dilution), no fungal growth was observed in the culture wells, and the seedlings grew well, with an average height of 4 ± 0.8 cm. However, higher concentrations of fermentation broth had a toxic effect on seed growth, causing the seeds to fail to grow normally.

[0063] Therefore, the fermentation broth of OUC-HL1638 diluted 100 times can be used as a biocontrol agent to deal with Fusarium oxysporum infection.

[0064] Example 5: Disease Prevention Experiment of Cherry Tomato Potted Plants Transplant cherry tomato seedlings into pots of 3 seedlings each (about 3 L of soil per pot) and place them outdoors in a natural environment for 1 week to acclimate (average daytime temperature about 20°C).

[0065] Water each healthy potted plant with 50 mL of Fusarium oxysporum inoculum culture that has been cultured for 2 days (1×10⁻⁶). 6 Inoculation was performed using CFU / mL. Treatment began 2 days after inoculation: the treatment group (FB) was treated by pouring 50 mL of Streptomyces OUC-HL1638 fermentation broth (1×10⁻⁶ CFU / mL) into each pot. 6 CFU / mL), once a week; two control groups were set up: the infected group (IC), i.e., the potted plants inoculated with the pathogen were watered with the same amount of sterile water every week; the uninfected group (UC), i.e., the plants were watered with sterile water only at regular intervals.

[0066] After all potted plants were grown outdoors for 30 days, the plant growth and the degree of wilting were observed to comprehensively evaluate the plant growth status and the prevention and control effect of the fermentation liquid.

[0067] Observation results as follows Figure 5 As shown, after 30 days of cultivation, the seedlings in the IC group exhibited severe wilting, slow growth, and yellowing of leaves; in contrast, the wilting symptoms of the seedlings in the fermentation broth treatment group (FB) were significantly reduced.

[0068] The above results indicate that when the fermentation broth of strain OUC-HL1638 is applied to 50 ml of soil per cubic meter weekly, the bacterial count is 1 × 10⁻⁶. 6 Fermentation broth with CFU / mL can effectively inhibit the occurrence of Fusarium wilt in plants.

[0069] Example 6: Test of the salt and alkali tolerance of Streptomyces OUC-HL1638 The fermentation medium F2 of the strain was appropriately modified to test the tolerance of OUC-HL1638 to high salt and alkali and the yield of active compounds under the corresponding conditions.

[0070] When testing the strain's salt tolerance, 0.5%, 1.5%, 3%, 4%, 5%, 6%, and 9% NaCl were added to the culture medium, and the pH was adjusted to 7.0.

[0071] When testing the strain's tolerance to alkali, the NaCl content was fixed at 3%, and the solution pH was adjusted to 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, and 10.0. Then, OUC-HL1638 was fermented according to the inoculation method in Example 2. 200 μL of the solution was periodically sampled and the OD was measured using a microplate reader. 600 To plot growth curves.

[0072] The results are as follows Figure 6 As shown, when the NaCl content is 0.5-3%, the logarithmic growth phase of OUC-HL1638 is within 12-24 h, and the yield of active compounds is the highest; when the NaCl content is 6%, the bacterial density of OUC-HL1638 decreases significantly, and the synthesis of active compounds is limited, indicating that the strain can tolerate high salt environment.

[0073] The OUC-HL1638 strain also exhibits high tolerance to alkaline conditions. Although the bacterial density decreased during the stable growth phase at pH 10.0, the production of active compounds did not decrease significantly. Therefore, the OUC-HL1638 fermentation broth still has the potential to be used as a biocontrol agent in high-salt, high-alkalinity farmland to control Fusarium oxysporum infection.

[0074] Example 7 Temperature tolerance test of Streptomyces OUC-HL1638 fermentation broth The strain was fermented according to the fermentation method in Example 2, and Fusarium oxysporum W2401 was cultured in liquid according to the method in Example 3, both cultures reaching a growth rate of 1×10⁻⁶. 6 CFU / mL.

[0075] After the fermentation broth was placed at 4°C for one week, the antibacterial effect of the refrigerated fermentation broth was evaluated using a 100-fold diluted fermentation broth according to the method in Example 4: 30 μL of Fusarium oxysporum W2401 bacterial suspension and 30 μL of fermentation broth / fermentation supernatant before and after refrigeration (diluted 100 times) were added to a 3 mL volume with Murashige and Skoog medium to achieve the above-mentioned different dilutions of the fermentation broth / fermentation supernatant. The wells containing only W2401 bacterial suspension and culture medium were designated as the infected group (IC), and the wells containing only culture medium were designated as the uninfected group (UC).

[0076] The results are as follows Figure 7 As shown, UC represents the uninfected group and IC represents the infected group. No fungal growth was observed in the culture wells before and after refrigeration of the fermentation broth, and the seedlings were growing well with an average height of 4 ± 0.8 cm. This indicates that after refrigeration at 4℃ for 7 days, the fermentation broth, diluted 100 times, still maintained significant and stable antifungal activity against Fusarium oxysporum.

[0077] This result fully confirms that the storage condition of 4℃ refrigeration does not affect the antibacterial effect of this strain. It also directly demonstrates that the antifungal active ingredients contained in its fermentation broth have excellent low-temperature stability and can maintain their activity without significant impact during low-temperature storage.

[0078] Example 8: Resistance test of Streptomyces OUC-HL1638 to chemical pesticides Seed culture of the strain was prepared according to Example 2.

[0079] Spread 100 μL of seed liquid onto an MS solid plate. Use a sterile punch to make holes in the plate surface and add 10 μL of each of the four commonly used pesticides to the holes: hymexazol (100 mg / μL), carbendazim (2.5 mg / mL), oxadixyl (2.5 mg / mL), and azoxystrobin (10 mg / mL).

[0080] The results are as follows Figure 8 As shown, the left figure shows the inhibitory effects of agricultural fungicides carbendazim, difenoconazole, pyraclostrobin, and hymexazol on the effective concentration of Fusarium oxysporum W2401. At the above concentrations, all four agricultural fungicides showed significant inhibitory effects on Fusarium oxysporum W2401. The right figure shows that at the same concentration of the above four agricultural fungicides, 100 μL of seed liquid was spread on MS solid plates. None of the four reagents showed any inhibitory effect on the growth of OUC-HL1638.

[0081] The four pesticides mentioned above exhibited inhibitory activity against Fusarium oxysporum but showed no inhibitory effect on Streptomyces OUC-HL1638. This characteristic indicates that this strain can coexist with chemical fungicides, and the negative impact on soil microecology can be indirectly reduced by decreasing the amount of chemical agents used.

[0082] Example 9: Surfactant Function of Streptomyces OUC-HL1638 After large-scale fermentation by strain OUC-HL1638, the fermentation broth was extracted with twice its volume of ethyl acetate, evaporated to dryness, and dissolved in methanol. The crude extract from the large-scale fermentation was dissolved in 500 mL of 90% methanol, and liquid-liquid extraction was performed in a separatory funnel using a hexane / 90% methanol (v / v) ratio of 1:1. The mixture was shaken to ensure complete extraction, and after standing for 2 h, the hexane was replaced. This process was repeated three times. After evaporation of both phases to dryness, 90% methanol and hexane layers were obtained, respectively. The 90% methanol layer was separated using a SEPAFLASH™ SW120 Bonded medium-pressure column.

[0083] Elution was performed with methanol at concentrations of 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%, yielding eight fractions (named Fr.1-8 sequentially). Among these, the antifungal active compound was present in fraction Fr.6. The collected fractions were evaporated to dryness and quantified to 10 mg / mL. The surface activity of the fraction obtained by elution with 80% methanol (fraction Fr.6) was tested.

[0084] Dispense 32 µL of crystal violet aqueous solution (0.0025%) into 1.5 mL EP tubes. Then, pipette 8 µL of the prepared sample into the EP tubes and gently blow (avoiding the generation of air bubbles) to mix it evenly. Pipette 25 µL of the mixed sample onto a smooth surface and observe its diffusion state.

[0085] Experimental results show that the surface tension of Fr.6 is less than that of water, and its interfacial tension with kerosene is much smaller than that between water and kerosene. The lower the surface tension of a material, the less shrinkage it exerts on impurities or the substrate under the same conditions, making it easier to diffuse on a solid surface and thus more easily wet the solid. General interfacial tension testing measures the magnitude of the interfacial tension between two substances. The lower the interfacial tension, the weaker the adhesion of the liquid, and the easier it is to wet the workpiece surface, resulting in better lubrication, cleaning, and drainage effects.

[0086] Table 3. Surface active functions of component Fr.6

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., 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 ( Streptomyces strain OUC-HL1638 (sp.) is characterized by, The accession number is CGMCCNo.36765.

2. A microbial agent, characterized in that, It includes any one or more of the Streptomyces strain OUC-HL1638 as described in claim 1, its bacterial suspension, fermentation broth, fermentation products, volatile gases, or extracts.

3. The use of the Streptomyces strain OUC-HL1638 according to claim 1 or the inoculum agent according to claim 2 in any one of A1) to A5): A1) Inhibits the growth of Fusarium oxysporum; A2) Prepare products that inhibit the growth of Fusarium oxysporum; A3) Prevention and control of plant diseases caused by Fusarium oxysporum; A4) Prevention and control of radish seedling wilt; A5) Control of plant wilt disease.

4. The application according to claim 3, characterized in that, The plant wilt disease mentioned includes tomato wilt, and the control method for tomato wilt includes the following steps: Using fermentation broth of OUC-HL1638 strain, 50 mL of broth with a bacterial count of 1×10⁻⁶ was applied weekly to each cubic meter of tomato-growing soil. 6 Fermentation broth at CFU / mL.

5. The use of the Streptomyces strain OUC-HL1638 of claim 1 or the microbial agent of claim 2 in the preparation of biosurfactants.

6. The application of the Streptomyces strain OUC-HL1638 of claim 1 or the microbial agent of claim 2 in the remediation of saline-alkali soil and / or the improvement of plant salt stress tolerance.

7. The application of the Streptomyces strain OUC-HL1638 according to claim 1 or the inoculant according to claim 2 in the control of plant diseases caused by Fusarium oxysporum under saline-alkali conditions, characterized in that, The plant diseases mentioned include radish seedling wilt and cherry tomato wilt.

8. The application of the Streptomyces strain OUC-HL1638 according to claim 1 or the inoculant according to claim 2 in the control of plant diseases under low-temperature conditions, characterized in that, The plant diseases mentioned include radish seedling wilt and cherry tomato wilt caused by Fusarium oxysporum.

9. The application according to claim 8, characterized in that, The fermentation broth of strain OUC-HL1638 showed no change in inhibitory activity against Fusarium oxysporum after being refrigerated at 4°C for 7 days.

10. A combined bactericide, characterized in that, The fungicide is composed of the Streptomyces strain OUC-HL1638 as described in claim 1 or the fungicide as described in claim 2, and an agricultural fungicide; the agricultural fungicide includes one or more of hymexazol, carbendazim, oxadixyl, and pyraclostrobin.

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