Streptomyces metabolite hydrogel preparation for preventing and controlling sclerotinia rot of colza and preparation method of streptomyces metabolite hydrogel preparation

Abstract

The invention discloses a streptomyces metabolite hydrogel preparation for preventing and controlling sclerotinia rot of colza and a preparation method of the streptomyces metabolite hydrogel preparation, and belongs to the technical field of microorganisms. According to the invention, a strain of streptomyces olivulariculi is obtained through screening and separation, and the preservation number of the streptomyces olivulariculi is CGMCC (China General Microbiological Culture Collection Center) No.35897. The streptomyces olivaceus and the hydrogel are combined to prepare the streptomyces metabolite hydrogel preparation, the streptomyces metabolite hydrogel preparation is used for preventing and controlling the sclerotinia rot of colza, and the prevention effect reaches 100%, so that a new solution is provided for green prevention and control of the sclerotinia rot of colza, and a scientific basis is provided for promoting green transformation of agricultural production.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to a streptomyces metabolite hydrogel formulation for the prevention and control of sclerotinia stem rot in rapeseed and its preparation method. Background Technology

[0002] Sclerotinia sclerotiorum, a major fungal disease of rapeseed, is characterized by its wide spread, rapid spread, and severe damage in major rapeseed producing areas. The latest monitoring data from 2025 shows an average incidence rate of 35%, with mortality rates exceeding 60% in some severely affected fields, resulting in annual yield losses of 10%-40%, and as high as 70% in severe cases. The disease survives in the soil as sclerotia for 5-8 years, spreading via ascospores and wind and rain. The peak incidence occurs during the budding to full flowering stage of rapeseed. Its pathogenic mechanism includes the secretion of oxalic acid to dissolve plant cell walls, the production of cell wall-degrading enzymes to destroy tissue structure, ultimately leading to stem rot and premature plant aging. Traditional chemical control faces a triple dilemma: continuous use of fungicides such as carbendazim and tebuconazole has led to a surge in the frequency of pathogen resistance from 12% in 2010 to 68% in 2025, with cross-resistance already emerging in some areas; chemical pesticides have a half-life of 30-90 days in the soil, resulting in excessive nitrate levels in groundwater and a 30%-50% decrease in soil microbial diversity; and pesticide residues in rapeseed are a prominent problem, with a 2024 sampling showing that carbendazim residues in rapeseed oil from conventional planting areas reached 0.15 mg / kg, exceeding the EU limit of 0.1 mg / kg.

[0003] Against this backdrop, biological control technology, due to its environmental friendliness and sustainability, shows great promise in the prevention and control of plant diseases. Streptomyces are a class of microorganisms with abundant metabolites, which possess various biological activities such as antibacterial, antifungal, and antiviral activity. Their metabolite library contains over 22,000 natural products and has been widely used in agriculture and medicine. For example, although the novel compound montamide A produced by Streptomyces S001 did not show significant antibacterial activity, it is of significant value in bioactivity research. Furthermore, Streptomyces has also shown good potential in the biological control of plant diseases; for instance, Streptomyces isolated from the rhizosphere of oil palm showed a significant inhibitory effect on oil palm root rot.

[0004] Hydrogels, as a novel drug carrier, are widely used in pesticides, cosmetics, and pharmaceuticals due to their excellent sustained-release properties and biocompatibility. For example, hymexazol hydrogels have a significant inhibitory effect on *Streptomyces*, the pathogen causing *Sclerotinia sclerotinia* rot in rapeseed. However, research on the use of *Streptomyces* metabolites combined with hydrogels for the control of *Sclerotinia sclerotinia* rot in rapeseed is still limited and requires further exploration. Summary of the Invention

[0005] The purpose of this invention is to provide a streptomyces metabolite hydrogel formulation for the prevention and control of sclerotinia stem rot in rapeseed and its preparation method, so as to solve the problems existing in the prior art. Combining Streptomyces oliveis and hydrogel to prepare a streptomyces metabolite hydrogel formulation can effectively prevent and control sclerotinia stem rot in rapeseed, and provide a scientific basis for promoting green prevention and control of sclerotinia stem rot in rapeseed.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a strain of Streptomyces olivoreticuli, with the accession number CGMCC No. 35897, the accession date being September 11, 2025, and the depositary institution being the China General Microbiological Culture Collection Center, located at Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0008] The present invention also provides the use of the aforementioned Streptomyces oliveii in any of the following:

[0009] (1) Application in inhibiting Sclerotinia sclerotiorum;

[0010] (2) Application in the control of sclerotinia stem rot in rapeseed;

[0011] (3) Application in the preparation of biological agents for the prevention and control of sclerotinia stem rot in rapeseed.

[0012] Preferably, the biological agent includes a hydrogel formulation.

[0013] The present invention also provides a hydrogel formulation for controlling sclerotinia stem rot in rapeseed, comprising the aforementioned Streptomyces oliveri.

[0014] This invention also provides a method for preparing a hydrogel formulation for controlling sclerotinia stem rot in rapeseed, comprising the step of mixing Streptomyces oliveri with a gel to prepare a hydrogel formulation; wherein the gel comprises carboxymethyl chitosan, sodium alginate and calcium chloride.

[0015] Preferably, the preparation method includes the following steps:

[0016] Using the fermentation broth of *Streptomyces oliveri* as a solvent, carboxymethyl chitosan and sodium alginate were added to prepare solutions I and II, respectively. Then, the calcium chloride aqueous solution was added to obtain a hydrogel preparation for controlling sclerotinia stem rot in rapeseed.

[0017] Preferably, the concentration of both solution I and solution II is 10 mg / mL, and solution I and solution II are mixed at a mass ratio of carboxymethyl chitosan to sodium alginate of (1-3):(1-3).

[0018] The concentration of the calcium chloride aqueous solution is 2-20 mg / mL.

[0019] This invention also provides a method for controlling sclerotinia stem rot in rapeseed, comprising the following steps:

[0020] Using the fermentation broth of Streptomyces oliveii as a solvent, carboxymethyl chitosan and sodium alginate were added to prepare solutions I and II, respectively. The two solutions were mixed evenly to obtain a mixed solution.

[0021] After spraying the mixture onto the rapeseed leaves, a calcium chloride aqueous solution is then sprayed onto them.

[0022] Preferably, in the mixture, the mass ratio of carboxymethyl chitosan to sodium alginate is (1-3):(1-3), and the concentrations of both solution I and solution II are 10 mg / mL;

[0023] The concentration of the calcium chloride aqueous solution is 2-20 mg / mL.

[0024] This invention also provides the use of the hydrogel formulation in any of the following:

[0025] (1) Application in inhibiting Sclerotinia sclerotiorum;

[0026] (2) Application in the prevention and control of sclerotinia stem rot in rapeseed.

[0027] The present invention discloses the following technical effects:

[0028] This invention screened a strain of *Streptomyces oliveii*, which exhibits good inhibitory effects against *Sclerotinia sclerotinia*, the causal agent of rapeseed sclerotinia. Combining the fermentation broth of this bacterium with a gel and applying it sequentially (first mixing the fermentation broth with CMCS / SA solution and spraying it onto rapeseed leaves, then spraying with calcium chloride solution) yielded even better control results. Therefore, developing a hydrogel formulation of *Streptomyces oliveii* metabolites based on this invention or its secondary metabolites holds promise for providing a new solution for the green control of *Sclerotinia sclerotinia* in rapeseed, and promoting the green transformation of agricultural production. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 It has the morphological characteristics of T016;

[0031] Figure 2 The complete genome map of Streptomyces oliveri T016;

[0032] Figure 3 Image of hydrogel formation;

[0033] Figure 4 The shear rheological behavior of hydrogels;

[0034] Figure 5 The dynamic contact angle diagram (A) and contact angle-time curve (B) of the hydrogel are shown. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] 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 have been described herein, any methods and materials similar 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.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] Example 1

[0041] 1. Screening of biocontrol Streptomyces

[0042] 1.1 Screening of Sclerotinia sclerotiorum for rapeseed in fermentation broth

[0043] Ten biocontrol Streptomyces species that showed good antagonistic effects in the laboratory were selected and inoculated into fermentation media A and B at a 1% inoculum. The cultures were incubated on a shaker at 220 rpm and 28 °C for 72 h, and the fermentation broth was obtained by filtration. A 0.6 cm specimen of Sclerotinia sclerotiorum var. rapeseed was punched and placed in the center of the culture medium. An Oxford cup was placed 2 cm to the left and right of the specimen, and 200 μL of fermentation broth was added. When the control group colonies reached 2 / 3 of the total plate size, the inhibition zone was observed and measured, and the inhibition rate was calculated.

[0044] Fermentation medium A: 30g corn flour, 20g soybean flour, 20g glucose, 3g calcium carbonate, 4g ammonium chloride, 1L distilled water.

[0045] Fermentation medium B: 20g soybean meal powder, 2g peptone, 20g glucose, 5g starch, 4g sodium chloride, 2g calcium carbonate, 0.5g dipotassium hydrogen phosphate, 0.5g magnesium sulfate, 2g yeast extract, 1L distilled water.

[0046] 2. Identification and Characterization of Streptomyces T016

[0047] 2.1 Mycelial Morphology Methods

[0048] The culture medium is heated to melt, then inverted and cooled. A sterile coverslip is inserted into the culture medium at approximately 40-45°. Using an inoculation loop, inoculate the bacterial culture at the junction of the culture medium and the coverslip, and then incubate upside down. The morphology of hyphae and spores is observed under a microscope.

[0049] 2.2 T016 whole genome sequencing

[0050] Whole-genome sequencing was performed, and the sequencing results were analyzed. The T016 metabolites were analyzed using the antiSMASH database.

[0051] 2.3 Determination of physiological and biochemical characteristics of T016

[0052] (1) Gelatin liquefaction test:

[0053] T016 was punctured and inoculated into gelatin liquefaction medium in test tubes. After incubation at 28 °C for 10 days, the test tubes were placed in a 4 °C refrigerator for 0.5 h, and the degree of gelatin liquefaction was observed. If the medium was partially or completely liquefied, it was a positive reaction; otherwise, it was a negative reaction.

[0054] Gelatin liquefaction medium: 20g glucose, 5g peptone, 120g gelatin, 1L water, sterilized at 115℃ for 15 min.

[0055] (2) Generation of hydrogen sulfide:

[0056] The bacterial strain was inoculated onto hydrogen sulfide medium and incubated at 28 °C for 5 days. The color change around the bacterial block was then observed. If the area around the bacterial block turned black, it indicated that hydrogen sulfide was being produced, which was a positive reaction; otherwise, it was a negative reaction.

[0057] Hydrogen sulfide medium: 10 g peptone, 0.5 g ferric citrate, 17 g agar powder, 1 L water.

[0058] (3) Carbon source utilization experiment:

[0059] Nine carbon sources, namely galactose, maltose, sucrose, xylose, mannitol, glucose, lactose, rhamnose, and fructose, were added to the basic carbon source utilization medium at 1% each. T016 was inoculated into a medium containing only one carbon source and cultured at 28 °C. After 7 days, the strain was observed to see if it could grow normally. If it grew normally, the strain could utilize the carbon source; otherwise, it could not.

[0060] Carbon source utilization basal culture medium: 1 g diammonium hydrogen phosphate, 1 g sodium chloride, 0.2 g magnesium sulfate heptahydrate, 0.5 g potassium dihydrogen phosphate, 20 g agar, 1 L distilled water.

[0061] (4) Nitrate reduction test:

[0062] Strains T016 were inoculated into nitrate-reducing medium and incubated at 28 °C for 7–14 days. The results were then analyzed according to the nitrate-reducing kit procedure.

[0063] Nitrate reducing medium: 0.5 g magnesium sulfate, 1 g potassium nitrate, 0.5 g dipotassium hydrogen phosphate, 0.5 g sodium chloride, 20 g sucrose, 1 L water.

[0064] (5) Iron production capacity test:

[0065] Inoculate strain T016 into CAS medium and incubate at 28 ℃ for 7 days. Observe whether an orange-yellow halo forms around the colony. If a halo is present, it indicates that the strain has the ability to synthesize siderophores; otherwise, it does not.

[0066] (6) Phosphorus solubilization capacity test:

[0067] Inoculate strain T016 onto organic and inorganic phosphorus media and incubate at 28 ℃ for 5-7 days. Observe whether a clear halo appears around the bacterial block. If a clear halo appears around the bacterial block, it indicates that it has phosphorus solubilizing ability; otherwise, it does not.

[0068] (7) Nitrogen fixation capacity test:

[0069] Inoculate strain T016 into nitrogen-free medium and incubate at 28 ℃ for 5-7 days. Observe whether the strain can grow in the medium. If it can grow normally, it indicates that it has nitrogen fixation ability; otherwise, it does not.

[0070] 3. Hydrogel preparation and formulation optimization

[0071] 3.1 Optimization of Streptomyces T016 hydrogel formulation

[0072] Weigh out a certain amount of carboxymethyl chitosan (CMCS) and sodium alginate (SA) respectively, and prepare these two materials to concentrations of 5 mg / mL and 10 mg / mL respectively. Mix CMCS:SA (m / m) in ratios of 1:1, 1:2, 1:3, 2:1 and 3:1, and then add CaCl2 solutions of 2 mg / mL, 4 mg / mL, 6 mg / mL, 8 mg / mL, 10 mg / mL and 20 mg / mL respectively.

[0073] 3.2 Characterization and evaluation of Streptomyces T016 hydrogel

[0074] 3.2.1 Determination of shear rheological properties of Streptomyces T016 hydrogel

[0075] The rheological properties of the hydrogel were evaluated using an MCR301 rheometer. This rheometer was equipped with a 20 mm parallel plate and operated at a temperature of 25 ± 0.1 ℃. The synthesized hydrogel was characterized by the dynamic stress scan spectrum of the hydrogel in the range of 0.1–100 Pa at a frequency of 1 Hz. The dynamic frequency scan spectrum of the gel in its linear viscoelastic state, determined from the dynamic stress scan measurements, i.e., the dynamic frequency scan range of 0.1–10 Hz at a strain of 1 Pa, was also obtained. Dynamic oscillation measurements of the gel were performed at 1% strain and 1 Hz, with shear rates starting from 1 s⁻¹. -1 Increase to 10 s -1 Immediately afterwards, the shear rate decreased from 10 s. -1 Reduced to 1 s -1 Oscillatory strain tests were conducted at a frequency of 1 Hz using alternating small strain (0.2%) and large strain (200%) to investigate the strain-induced damage and self-healing properties of hydrogel under applied stress.

[0076] 3.2.2 Contact Angle Determination of Streptomyces T016 Hydrogel

[0077] The contact angle (DCA) of different droplets was determined using the seated drop method with an Experience A-300 optical contact angle / surface tension meter (DropMeter, Ningbo). Fresh rapeseed leaves were selected as test subjects. The leaves were cut into 20*20 mm pieces and attached to a glass slide. A 6 μL droplet of the test liquid was gently placed on the leaf surface using a syringe. The four treatments are as follows: (1) T+CMCS / SA: CMCS / SA solution droplets (using T016 fermentation broth as solvent, the concentration of each solution is 10 mg / mL, and the mass ratio of CMCS and SA is 1:2); (2) Gel KT2: T+CMCS / SA solution (using T016 fermentation broth as solvent, the concentration of each solution is 10 mg / mL, and the mass ratio of CMCS and SA is 1:2) and CaCl2 droplets (CaCl2 concentration is 4 mg / mL) are mixed in a volume ratio of 1:1 to form a gel and then gently placed on the leaf; (3) Sequential spraying of gel KT2: 3 μL T+CMCS / SA solution (using T016 fermentation broth as solvent, the concentration of each solution is 10 mg / mL, and the mass ratio of CMCS and SA is 1:2) is first gently placed on the leaf, and then 3 μL CaCl2 solution (4 mg / mL) is injected through an injection needle inserted into the CMCS / SA droplet. (4) T-CK: T016 fermentation broth original solution control.

[0078] 4. Effects of Streptomyces T016 hydrogel on sclerotinia stem rot in rapeseed leaves

[0079] Rapeseed leaf treatment: Select rapeseed leaves of uniform size, rinse them with sterile water, place them in a petri dish lined with filter paper, wet the bottom layer of filter paper and cover the petiole with cotton to keep it moist. The four treatments are as follows: (1) T+CMCS / SA: CMCS / SA solution droplets (using T016 fermentation broth as solvent, the concentration of each solution is prepared to 10 mg / mL, and the mass ratio of CMCS and SA is 1:2); (2) Sequential spraying of gel KT2: First spray T+CMCS / SA solution (using T016 fermentation broth as solvent, the concentration of each solution is prepared to 10 mg / mL, and the mass ratio of CMCS and SA is 1:2), and then spray an equal amount of CaCl2 solution (4 mg / mL); (3) T016: T016 fermentation broth; (4) Blank control: water control. After spraying different treatments, rapeseed leaves were placed in a 25 ℃ incubator for 24 h of humidity incubation. Then, a sterile syringe needle was used to create wounds on the detached rapeseed leaves, and 5 mm diameter Sclerotinia sclerotiorum bacterial blocks were inoculated on the wounds. Each treatment was repeated 3 times and placed in a 25 ℃ incubator for humidity incubation. The diameter of leaf lesions was measured using the cross-cross method, and the control effect of different concentrations was calculated.

[0080] 5. Test Results

[0081] 5.1 Screening of biocontrol Streptomyces

[0082] The antibacterial activity of fermentation broths of 10 Streptomyces species preserved in the laboratory against Sclerotinia sclerotinia, the causal agent of rapeseed rot, was determined using the Oxford cup method. The table below shows that the fermentation broths of 7 Streptomyces species all had an inhibitory effect on Sclerotinia sclerotinia, among which Streptomyces T016 showed the best inhibitory effect.

[0083] Table 1. Screening of Streptomyces antagonistic to Sclerotinia stem rot in rapeseed.

[0084]

[0085] 5.2 Identification and Morphological Observation of Streptomyces T016

[0086] like Figure 1 As shown, the T016 strain colonies are dry, opaque, and densely velvety, adhering tightly to the culture medium. Initially white, the colonies begin to produce grayish-green spores on days 4-5 of incubation at 28°C, gradually turning the colonies grayish-green. Under a microscope, the hyphae are observed to be highly branched and unbroken; from day 4 onwards, some hyphae differentiate into dense spore hyphae.

[0087] Sequencing and assembly results showed that the total genome length of Streptomyces T016 was 8,302,896 bp, with a GC content of 71.33%. Gene function annotation of the whole genome using the NR, COG, KEGG, and GO databases identified 6,898, 5,197, 1,403, and 4,562 genes, respectively, accounting for 98.64%, 74.32%, 20.06%, and 65.24% of the total genome length. Prediction of coding genes, repetitive sequences, and non-coding RNAs revealed the composition of the T016 genome, which encodes 71 tRNAs, 7 5S rRNAs, 7 16S rRNAs, 7 23S rRNAs, and 98 sRNAs (total length 10,264 bp).

[0088] The anti-SMASH analysis identified 46 secondary metabolic gene clusters, including nucleosides, polyketides, non-ribosomal peptides, terpenes, and carbohydrates. Specific base positions and cluster types are listed in Tables 2-4.

[0089] Table 2

[0090]

[0091] Table 3

[0092]

[0093] Note: The serial numbers in Table 3 follow the sequence of those in Table 2.

[0094] Table 4

[0095]

[0096] Note: The serial numbers in Table 4 follow the sequence of those in Table 3.

[0097] After inoculating the biocontrol strain T016 into test plates or tubes and culturing for 5-10 days, the hydrogen sulfide reaction and siderogenesis results were negative, indicating that it cannot produce hydrogen sulfide and iron ions. However, strain T016 possesses nitrate reduction ability, nitrogen fixation and gelatin liquefaction ability, and can utilize both organic and inorganic phosphorus. Furthermore, strain T016 cannot utilize xylose as a carbon source, but it can utilize the other eight carbon sources, with high utilization rates for galactose, maltose, and glucose. (See Table 5.)

[0098] Table 5. Physiological and biochemical characteristics of Streptomyces T016

[0099]

[0100] Note: "+" in the table indicates a positive reaction.

[0101] The aforementioned Streptomyces olivoreticuli was deposited on September 11, 2025, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35897, located at Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0102] 5.3 Hydrogel preparation and formulation optimization

[0103] 5.3.1 Optimization of the Streptomyces T016 hydrogel formulation

[0104] By mixing carboxymethyl chitosan, sodium alginate, and calcium chloride in different proportions, it was found that when carboxymethyl chitosan and sodium alginate were mixed in a 1:2 ratio, and then calcium chloride solution was added, a complete gel could be formed. Figure 3 .

[0105] 5.3.2 Characterization and evaluation of Streptomyces T016 hydrogel

[0106] (1) Determination of shear rheological properties of Streptomyces T016 hydrogel

[0107] The shear rheology of hydrogels can provide a reference for their fluidity and physical stability. Figure 4 The rheological diagrams of the selected hydrogels are shown in the figure. As shown, the elastic modulus G' of the hydrogels is greater than its viscous modulus G", indicating that the hydrogels have stable elastic properties within the strain range; and with the increase of shear rate, the hydrogels exhibit good shear thinning behavior.

[0108] (2) Contact angle determination of Streptomyces T016 hydrogel

[0109] Using a contact angle meter, the dynamic contact angle of the hydrogel on the surface of rapeseed leaves was measured with different application sequences, such as... Figure 5 As shown, at 450 s, the contact angles of the four treatments were 111.88°, 99.85°, 95.67°, and 108.24°, respectively. The contact angle of the sequentially sprayed hydrogel decreased from 107.25° at 0 s to 95.67° at 450 s, indicating that the sequentially sprayed hydrogel has a lower contact angle and better wettability and adhesion stability.

[0110] 5.4 Effects of Streptomyces T016 hydrogel on sclerotinia stem rot in rapeseed leaves

[0111] After spraying different treatments of rapeseed leaves with hydrogel, it was found that the hydrogel KT2 with the addition of fermentation broth of strain T016 had a better control effect on large detached rapeseed leaves, with an efficacy of 100% (see Table 6).

[0112] Table 6. Efficacy of Streptomyces T016 hydrogel KT2 against detached rapeseed leaves

[0113]

[0114] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A strain of Streptomyces olivoreticuli, characterized in that, The preservation number of the *Streptomyces oliveri* is CGMCC No. 35897.

2. The use of *Streptomyces oliveri* as described in claim 1 in any of the following: (1) Application in inhibiting Sclerotinia sclerotiorum; (2) Application in the control of sclerotinia stem rot in rapeseed; (3) Application in the preparation of biological agents for the prevention and control of sclerotinia stem rot in rapeseed.

3. The application as described in claim 2, characterized in that, The biological agents include hydrogel formulations.

4. A hydrogel formulation for controlling sclerotinia stem rot in rapeseed, characterized in that, Includes *Streptomyces oliveii* as described in claim 1.

5. A method for preparing a hydrogel formulation for controlling sclerotinia stem rot in rapeseed, characterized in that, The method includes the step of preparing a hydrogel formulation by mixing the *Streptomyces oliveri* of claim 1 with a gel; the gel comprises carboxymethyl chitosan, sodium alginate, and calcium chloride.

6. The preparation method according to claim 5, characterized in that, The preparation method includes the following steps: Using the fermentation broth of *Streptomyces oliveri* as a solvent, carboxymethyl chitosan and sodium alginate were added to prepare solutions I and II, respectively. Then, the calcium chloride aqueous solution was added to obtain a hydrogel preparation for controlling sclerotinia stem rot in rapeseed.

7. The preparation method according to claim 6, characterized in that, The concentration of both solution I and solution II is 10 mg / mL. Solution I and solution II are mixed at a mass ratio of carboxymethyl chitosan to sodium alginate of (1-3):(1-3). The concentration of the calcium chloride aqueous solution is 2-20 mg / mL.

8. A method for controlling sclerotinia stem rot in rapeseed, characterized in that, Includes the following steps: Using the fermentation broth of Streptomyces oliveii as a solvent, carboxymethyl chitosan and sodium alginate were added to prepare solutions I and II, respectively. The two solutions were mixed evenly to obtain a mixed solution. After spraying the mixture onto the rapeseed leaves, a calcium chloride aqueous solution is then sprayed onto them.

9. The method as described in claim 8, characterized in that, In the mixture, the mass ratio of carboxymethyl chitosan to sodium alginate is (1-3):(1-3), and the concentrations of both solution I and solution II are 10 mg / mL; The concentration of the calcium chloride aqueous solution is 2-20 mg / mL.

10. The use of the hydrogel formulation as described in claim 4 in any of the following: (1) Application in inhibiting Sclerotinia sclerotiorum; (2) Application in the prevention and control of sclerotinia stem rot in rapeseed.

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