Bacillus siamensis strain bswq66, microbial inoculant and application thereof

Abstract

The application discloses a bacillus siamensis BZWQ66, a microbial inoculum and application thereof, and belongs to the technical field of microorganisms. The bacillus siamensis BZWQ66 is screened from rhizosphere soil of potato powdery scab and has a preservation number of CGMCC No.39538. Experimental results show that the bacillus siamensis BZWQ66 can significantly inhibit the growth of streptomyces lydicus, fusarium oxysporum, neocosmospora vasinfecta, verticillium dahliae, rhizoctonia solani and alternaria solani, has a significant prevention effect on multiple soil-borne diseases such as potato powdery scab, potato early blight, potato wilt, potato yellow wilt, sweet potato root rot, potato black scab, potato scab and peanut fruit rot, and can effectively promote plant growth. The application provides a new strain resource for biological control of plant soil-borne diseases and promotion of plant growth.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to a strain of Bacillus sicca BZWQ66, microbial agents, and their applications. Background Technology

[0002] Crop diseases are a significant factor limiting agricultural production, often causing yield losses and quality declines, seriously impacting food security. Effective crop disease control has substantial economic, ecological, and social benefits. Social development places higher demands on disease control, requiring efforts to both control diseases within permissible economic limits and reduce pesticide use and residues to protect the ecological environment. Therefore, developing green biological control methods for crop diseases is essential.

[0003] Bacillus is a Gram-positive bacterium, ubiquitous in nature and can be isolated from all environmental niches. Bacillus species are commonly used in the production of agricultural, industrial, and pharmaceutical products. Biofertilizers can serve as alternatives to chemical fertilizers and pesticides, effectively antagonizing plant pathogens, preventing disease occurrence or outbreaks, promoting plant growth, and increasing yields. Beneficial Bacillus species form biofilms on the plant root surface, promoting plant growth. Applying Bacillus-based fertilizers to the soil can also increase the availability of nutrients in the rhizosphere, control the growth of pathogenic microorganisms, and induce plant resistance to pathogens.

[0004] With the expansion of crop cultivation areas, crop diseases are becoming increasingly serious. While Bacillus has been widely used in biological control to manage various plant diseases, such as powdery mildew, root rot, black scurf, wilt, canker, and fruit rot, its effectiveness remains unsatisfactory, and most biocontrol strains can only control a single type of pathogen. Therefore, there is an urgent need to provide a biocontrol strain with outstanding control efficacy and broad-spectrum control capabilities. Summary of the Invention

[0005] The purpose of this invention is to provide a strain of Bacillus sicca BZWQ66, a microbial inoculant, and its applications to solve the problems existing in the prior art. The Bacillus sicca BZWQ66 provided by this invention has a broad-spectrum control effect against pathogens, providing a new strain resource for the biological control of soil-borne plant diseases and the promotion of plant growth.

[0006] To achieve the above objectives, the present invention provides the following solution: This invention provides a strain of Bacillus sicca ( Bacillus siamensis BZWQ66, the Bacillus sicca of Siamese origin, has the accession number CGMCC No. 39538.

[0007] This invention provides the application of the above-mentioned Bacillus sicca BZWQ66 in the preparation of products that promote plant growth and / or control soil-borne diseases.

[0008] Optionally, the soil-borne diseases include potato powdery scab, potato wilt, potato black scurf, sweet potato root rot, potato verticillium wilt, potato early blight, potato scab, and peanut fruit rot.

[0009] Optionally, the plants include potatoes, peanuts, cucumbers, tomatoes, peas, pumpkins, radishes, sweet potatoes, wheat, and corn.

[0010] Optionally, the product includes microbial inoculants.

[0011] This invention provides a microbial agent for promoting plant growth and / or preventing soil-borne diseases, wherein the microbial agent includes the aforementioned Bacillus sicca BZWQ66.

[0012] Optionally, the microbial agent may be in the form of a liquid agent or a solid agent.

[0013] Optionally, when the microbial agent is in liquid form, the effective viable count of the Bacillus sicca BZWQ66 is ≥1.65 × 10⁻⁶. 9 CFU / mL; When the microbial agent is in the form of a solid agent, the effective viable count of the Bacillus sicca BZWQ66 is ≥1.65 × 10⁻⁶. 8 CFU / g.

[0014] This invention provides the application of the above-mentioned Bacillus sicca BZWQ66 or the above-mentioned microbial agents in the prevention and control of soil-borne diseases.

[0015] More preferably, the soil-borne diseases include potato powdery scab, potato wilt, potato black scurf, sweet potato root rot, potato verticillium wilt, potato early blight, potato scab, and peanut fruit rot.

[0016] This invention provides the application of the above-mentioned Bacillus sicca BZWQ66 or the above-mentioned microbial agents in inhibiting pathogenic microorganisms.

[0017] More preferably, the pathogenic microorganisms include *Potato scab fungus*, *Potato early blight fungus*, *Potato black scurvy fungus*, *Potato wilt fungus*, *Peanut rot fungus*, and *Potato verticillium wilt fungus*.

[0018] The present invention discloses the following technical effects: This invention screened a strain of *Bacillus sicca* BZWQ66 from the rhizosphere soil of a potato field infected with powdery mildew. Its preservation number is CGMCC No. 39538. Experimental results show that *Bacillus sicca* BZWQ66 possesses the ability to produce proteases, cellulases, pectins, amylases, laccases, and siderophores, as well as the ability to solubilize phosphorus, potassium, and fix nitrogen, effectively promoting plant growth. *Bacillus sicca* BZWQ66 also stably inhibits the growth of *Streptomyces scabica*, *Fusarium oxysporum*, *Neococcus sanguinis*, *Verticillium dahliae*, *Rhizoctonia solani*, and *Alternaria alternata*, demonstrating significant control efficacy against various soil-borne diseases such as potato powdery mildew, sweet potato root rot, potato black scurf, potato wilt, and potato scab. This invention provides a new strain resource for the biological control of soil-borne plant diseases and for promoting plant growth. Attached Figure Description

[0019] 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.

[0020] Figure 1 This is a colony morphology diagram of Bacillus sicca BZWQ66. Figure 2 The image shows the physiological and biochemical function test results of Bacillus sicca BZWQ66; where A represents the protease production ability test result; B represents the laccase production ability test result; C represents the siderophore production ability test result; D represents the nitrogen fixation ability test result; E represents the potassium solubilization ability test result; F represents the amylase production ability test result; G represents the inorganic phosphorus solubilization ability test result; and H represents the cellulase production ability test result. Figure 3 Phylogenetic tree of Bacillus sicca BZWQ66 constructed based on 16S rDNA sequence; Figure 4 The image shows the inhibitory effect of Bacillus sicca BZWQ66 on six pathogens; where A represents the inhibitory effect on Neocarobacter osmosis (…). Neocosmospora vasinfecta A) Inhibitory effect against GF-1; B) Inhibitory effect against HZ-RS of potato black scurf; C) Inhibitory effect against CPS-1 of potato scab; D) Inhibitory effect against KW-F of potato wilt; E) Inhibitory effect against ZY-AS of potato early blight; F) Inhibitory effect against HW-VD of potato verticillium wilt. Figure 5This study investigated the growth-promoting effects of Bacillus sicca BZWQ66 liquid inoculant on plant growth. Specifically, A represents the growth-promoting effect on cucumber seedlings 10 days after treatment; B represents the growth-promoting effect on pumpkin seedlings 10 days after treatment; C represents the growth-promoting effect on corn seedlings 10 days after treatment; D represents the growth-promoting effect on radish seedlings 10 days after treatment; E represents the growth-promoting effect on wheat seedlings 10 days after treatment; F represents the growth-promoting effect on potato seedlings 10 days after treatment; and G represents the growth-promoting effect on peanut seedlings 10 days after treatment. In A and G, a represents plants treated with Bacillus sicca BZWQ66 inoculant, and b represents control plants. Figure 6 The image shows the results of a pot experiment on the control of potato wilt by Bacillus sicca BZWQ66 inoculum; where A is the water control; B is the Bacillus sicca BZWQ66 inoculum treatment; and C is the inoculation control. Figure 7 The figure shows the results of a field trial of Bacillus sicca BZWQ66 inoculum for the control of potato powdery scab; where A represents the treatment with Bacillus sicca BZWQ66 inoculum and B represents routine management. Figure 8 The figure shows the results of a field trial of Bacillus sicca BZWQ66 inoculum for the control of sweet potato root rot; where A represents the treatment with Bacillus sicca BZWQ66 inoculum and B represents routine management.

[0021] Biological Preservation Information: Siamese Bacillus ( Bacillus siamensis BZWQ66 was deposited on June 30, 2026, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC NO.39538. The deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Example 1: Isolation, screening, and identification of Bacillus sicca BZWQ66 1. Isolation and screening of strain BZWQ66 Soil samples from the rhizosphere of diseased plants in fields where potatoes have been continuously cropped for many years and have developed potato scab disease were placed in a 200-mesh sieve. The soil samples were then coated with a fungicide containing potato scab pathogen CPS-1. Streptomyces scabies CPS-1 (disclosed in the literature "Cloning and Expression of Pathogenic Genes of Potato Scab Bacterium") was placed in a PDA culture dish and incubated at 30°C for 48 hours. The central colonies with inhibition zones were picked, purified by streak plating, and then cultured on PDA slant for 24 hours. The culture was then stored in a refrigerator at 4°C for later use. After the isolated bacteria were propagated in LB liquid medium, 5 μL of each strain was evenly inoculated onto filter paper discs of culture plates coated with different soil-borne pathogens. The strains were cultured at 28℃ for 72 h, and each treatment was repeated 3 times. The strain that showed inhibitory effects against different soil-borne pathogens was selected and recorded as strain BZWQ66.

[0028] 2. Identification of strain BZWQ66 2.1 Morphological observation of strain BZWQ66 Strawberry strain BZWQ66 was streaked onto a PDA agar plate, which was then inverted and incubated at 30°C for 24 hours. Colony growth was observed and recorded. Initially, the colonies on the plate were round, milky white, and opaque, resembling... Figure 1 As shown; later colonies can form larger films with relatively neat edges.

[0029] 2.2 Physiological and biochemical functional determination of strain BZWQ66 The information on the culture media required for physiological and biochemical functional assays is as follows: Inorganic phosphorus medium: 10.0g glucose, 0.5g (NH4)2SO4, 0.3g MgSO4·7H2O, 0.3g NaCl, 0.3g KCl, 0.03g FeSO4·7H2O, 0.03g MnSO4·7H2O, 25.0g Ca3(PO4)2, 17.0g agar, add distilled water to a final volume of 1.0L, maintain pH between 7.0 and 7.4, autoclave at 121℃ for 20min.

[0030] Nitrogen-fixing medium: KH2PO4 0.2g, MnSO4 0.2g, NaCl 0.2g, CaCO3 5.0g, mannitol 10.0g, CaSO4 0.1g, agar 18.0g, add distilled water to a final volume of 1.0L, pH 7.0, autoclave at 121℃ for 30min.

[0031] Potassium-solubilizing medium: Na2HPO4 2.0g, FeCl3 0.005g, MgSO4·7H2O 0.5g, CaCO3 0.1g, sucrose 5.0g, potassium feldspar powder (washed 5 times with deionized water) 1.0g, bromothymol blue 0.1g, agar 20.0g, add distilled water to a final volume of 1.0L, pH 7.0, autoclave at 121℃ for 20min.

[0032] Protease medium: 15.0g skim milk powder, 15.0g agar, add distilled water to a final volume of 1.0L, set pH to normal, autoclave at 110℃ for 15min.

[0033] Starch hydrolase culture medium: 2.0g soluble starch, 3.0g beef extract, 5.0g peptone, 2.5g glucose, 18.0g agar, add distilled water to a final volume of 1.0L, pH 7.0, autoclave at 121℃ for 20min.

[0034] IAA medium: Add 0.1g of L-tryptophan to LB medium and autoclave at 121℃ for 20min.

[0035] Cellulase medium: 10.0g peptone, 10.0g sodium carboxymethyl cellulose (CMC-Na), 5.0g yeast extract, 5.0g NaCl, 0.2g MgSO4, 1.0g KH2PO4, 20.0g agar, add distilled water to a final volume of 1.0L, autoclave at 115℃ for 30min.

[0036] Pectinase medium: 0.5 g MgSO4·7H2O, 1.0 g KH2PO4·3H2O, 0.01 g FeSO4·7H2O, 2.0 g pectin, 0.2 g Congo red, 20.0 g agar, add distilled water to a final volume of 1.0 L, set pH to natural, autoclave at 121℃ for 20 min.

[0037] Laccase medium (LB-guaiacol medium): Add 0.04% guaiacol to LB medium and autoclave at 121℃ for 20 min.

[0038] Siderophore culture medium (CAS): CAS 0.0605g, HDTMA 0.0729g, FeCl3·6H2O 0.002645g, NaH2PO4·2H2O 0.29525g, Na2HPO4·12H2O 1.2135g, NH4Cl 0.125g, KH2PO4 0.0375g, NaCl 0.0625g, agar 9.0g, diluted with distilled water to a final volume of 1.0L, autoclaved at 116℃ for 30min, purchased from Haibo Biotechnology Co., Ltd.

[0039] Salkowski colorimetric solution: 15 mL of 0.5 mol / L FeCl3 solution, 300 mL of H2SO4, and 500 mL of distilled water. Mix well before use and store away from light.

[0040] Strain BZWQ66 was inoculated onto protease, cellulase, amylase, laccase, and pectinase media, respectively, and incubated at 28°C for 4 days. The presence or absence of a clear zone around the strain on each medium was observed. The presence of a clear zone indicated that strain BZWQ66 possessed the function of producing the corresponding enzyme; otherwise, it did not.

[0041] After strain BZWQ66 was cultured on cellulase medium for 5 days, an appropriate amount of Congo red solution (1 mg / mL) was added to the medium. After staining for 1 hour, the Congo red solution was poured out, and the strain was washed repeatedly with distilled water. Finally, it was soaked and eluted with an appropriate amount of NaCl solution (1 mol / L) for 30 minutes. The NaCl eluent was then poured out. If a clear zone was formed around the strain, it indicated that cellulase could be produced; otherwise, it could not.

[0042] The selected strain BZWQ66 was spotted onto an inorganic phosphorus medium plate and incubated at 28°C for 2-5 days. The presence or absence of a clear zone was observed to determine the phosphorus solubilizing ability of strain BZWQ66.

[0043] The selected strain BZWQ66 was inoculated onto potassium-solubilizing and nitrogen-fixing medium plates using the three-zone streak method and cultured at 28℃ for 2-5 days. The results showed that strain BZWQ66 could produce smooth, transparent, oil-drop-shaped colonies.

[0044] The selected strain BZWQ66 was inoculated onto CAS plates and cultured at 28°C for 2-5 days. The presence of transparent orange circles was observed to determine the strength of the siderophore production capacity of strain BZWQ66.

[0045] The selected bacterial strain BZWQ66 was inoculated into IAA medium and cultured at 28℃ and 180 r / min for 48 h. Then, 1.0 mL of the bacterial suspension was mixed with Salkowski colorimetric solution. A control was prepared by mixing 1.0 mL of 50 mg / L IAA standard solution with an equal volume of the colorimetric solution. All mixtures were incubated in the dark for 30 min and observed. If the solution turned red, strain BZWQ66 could produce IAA; otherwise, it could not.

[0046] The test results are shown in Table 1 and Figure 2 As shown.

[0047] Table 1. Statistical analysis of functional test results for strain BZWQ66 Note: "+" indicates a positive result, and "-" indicates a negative result.

[0048] From Table 1 and Figure 2 The test results show that strain BZWQ66 has the ability to produce protease, cellulase, amylase, pectinase, laccase, siderophore and IAA, and also has the functions of phosphorus solubilization, potassium solubilization and nitrogen fixation.

[0049] 3. According to 16S rRNA Molecular identification of gene sequences DNA was extracted from strain BZWQ66 using a bacterial genomic DNA extraction kit from Tiangen Biotech Co., Ltd. PCR amplification was performed using 27F / 1492R bacterial primers (primer sequences are detailed in Table 2). PCR products were detected by 1% agarose gel electrophoresis and then sent to Shanghai Sangon Biotech Co., Ltd. for sequencing. After sequencing, the obtained sequences were submitted to the GenBank nucleic acid database for BLAST alignment. Sequences with high similarity were selected for analysis. The 16S sequence of strain BZWQ66 was analyzed using the neighbor-joining method in Mega 6.0 software. rRNA Genetic constructs phylogenetic trees.

[0050] Table 2 Primer sequences for molecular biological identification The obtained PCR product was sequenced by Tianjin Qingke Biotechnology Co., Ltd., and the 16S r of strain BZWQ66 was analyzed. RNA The nucleotide sequence of the gene is shown in SEQ ID NO.3, specifically:

[0051] The obtained nucleotide sequences were subjected to BLAST homology sequence alignment analysis using the NCBI database, yielding sequences with high similarity. A phylogenetic tree was constructed using MEGA 6.0 software. Figure 3 The 16S of strain BZWQ66 isolated in this invention rRNA Sequence and Bacillus sicca ( Bacillus siamensis ) of 16S rRNA The gene homology is 100%.

[0052] Based on the above morphological observations, physiological and biochemical characteristics, and multi-gene sequence identification results, it can be determined that the strain screened in this embodiment is Bacillus sicca (Bacillus sicca). Bacillus siamensis It was named Bacillus sicca BZWQ66.

[0053] 4. Strain preservation Siamese Bacillus ( Bacillus siamensis BZWQ66 was deposited on June 30, 2026, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 39538. The deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0054] Example 2: In-plate inhibition test of Bacillus sicca BZWQ66 against soil-borne pathogens Tested pathogens: *CPS-1*, *ZY-AS*, *HZ-RS*, *KW-F*, and *Neocarpus spp.* Neocosmospora vasinfecta GF-1 (the pathogen of peanut fruit rot, abbreviated as GF-1) and HW-VD (the pathogen of potato verticillium wilt, abbreviated as HW-VD) (the above pathogens were disclosed in the master's thesis "Research and Development of Biocontrol Compound Microbial Agent and Its Effect on the Control of Three Soil-borne Diseases", Shi Jiannan, 2021).

[0055] The plate confrontation method was used for detection. Method 1: Using various soil-borne pathogens as indicator bacteria, the antibacterial activity of Bacillus sicca BZWQ66 was tested. The specific steps were as follows: Using a 6 mm diameter punch, bacterial discs (excluding Streptomyces scabica and Verticillium dahliae) were collected from a plate. The bacterial discs were inoculated upside down into the center of PDA medium and incubated upside down in a 28℃ incubator for 2 days. When the diameter of the pathogens was about 2 cm, Bacillus sicca BZWQ66 was inoculated. A 6 mm diameter filter paper disc was placed 2 cm away from the edge of the pathogens using sterile forceps. 2 µL of the Bacillus sicca BZWQ66 bacterial suspension (effective viable count 5.0 × 10⁻⁶) was aspirated using a micropipette.6 Add (CFU / mL) to filter paper, inoculating 2-4 spots on each PDA plate, using normally growing pathogens as a control. Method 2: Add spore suspensions of *Streptomyces scabica* and *Verticillium dahliae* (effective viable count 1.0 × 10⁻⁶) to filter paper. 5 A 2µL suspension of Bacillus sicca BZWQ66 (with an effective viable count of 5.0 × 10⁻⁶ CFU / mL) was evenly spread in a petri dish. 6 Add CFU / mL to the middle filter paper. Incubate the petri dishes in a 28℃ incubator for 4 days. Measure the radius (distance between the edge of the pathogen at inoculation and the edge of the colony at measurement) of the pathogens in the control group and the treatment group, calculate the inhibition rate, and measure the width of the inhibition zone. All tests were repeated three times.

[0056] The formula for calculating the antibacterial rate is as follows: Inhibition rate (%) = (radius of pathogen in control group - radius of pathogen in treatment group) / radius of pathogen in control group × 100.

[0057] The antibacterial test results are shown in Table 3 and Figure 4 As shown, the results indicate that *Bacillus sicca* BZWQ66 exhibits good antibacterial activity against all six tested soil-borne pathogens. It forms a distinct inhibition zone against each tested pathogen, effectively inhibiting their growth, with the highest inhibition rate reaching 64.75%. Therefore, *Bacillus sicca* BZWQ66 demonstrates good antibacterial activity against various soil-borne pathogens.

[0058] Table 3. Results of antibacterial tests of strain BZWQ66 against six soil-borne pathogens. Example 3: Fermentation process and preparation of inoculum of Bacillus sicca BZWQ66 1. Preparation of Bacillus sicca BZWQ66 liquid inoculum Bacillus sicca BZWQ66 was inoculated into LB medium and activated at 28℃ for 48 h. The activated strain was then propagated in 500 mL Erlenmeyer flasks to obtain a fermentation seed culture. This seed culture was inoculated into medium 6 at a 5% inoculation rate, and continuous fermentation was carried out in 500 mL shake flasks and a 50 L fermenter under the following conditions: rotation speed 180 r / min, fermentation temperature 30℃, and fermentation time 20 h. This yielded a liquid Bacillus sicca BZWQ66 inoculum with a bacterial count of approximately 1.90 × 10⁻⁶. 9 CFU / mL. Samples were taken promptly after each fermentation was completed, and serial dilution counting was performed using the plate dilution method to determine the bacterial count in the fermentation broth.

[0059] The formula for culture medium No. 6 is as follows: 1.2 wt.% peanut cake powder, 2.0 wt.% soybean powder, 1.0 wt.% wheat bran powder, 1.2 wt.% glucose, 0.5 wt.% ammonium sulfate, 0.5 wt.% magnesium sulfate, 0.5 wt.% sodium chloride, 0.2 wt.% calcium carbonate, 0.1 wt.% monosodium glutamate, diluted with distilled water to 1000 mL, mixed well, and then autoclaved at 121℃ for 20 min.

[0060] 2. Preparation of Bacillus sicca BZWQ66 solid inoculum The liquid fermentation broth obtained from Bacillus sicca BZWQ66 (with an effective viable count of 1.90 × 10⁶) 9 (CFU / mL) was inoculated into a solid fermentation substrate at an inoculum size of 0.5 mL / g. After drying and pulverizing the fermentation product, Bacillus sicca BZWQ66 solid inoculum was obtained, with a viable count of 4.80 × 10⁻⁶ cells. 8 CFU / g.

[0061] The solid fermentation substrate formula consists of peanut meal powder, diatomaceous earth, and bentonite, with a mass ratio of 1.5:8:0.5.

[0062] Example 4 Safety test of Bacillus sicca BZWQ66 seedlings Bacillus sicca BZWQ66 liquid inoculum (1.90×10⁻⁶) 9 Safety tests were conducted on seedlings of potato, cucumber, radish, pumpkin, peanut, corn, and wheat using a concentration of CFU / mL. One week after emergence, Bacillus sicca BZWQ66 liquid inoculant was diluted 20-fold and applied as a root drench. Water was used as a control (CK). Plant growth was monitored, and after 15 days of treatment, various growth indicators were investigated and statistically analyzed. Results are shown in Table 4. Figure 5 .

[0063] Table 4. Statistical results of growth indicators of different crop seedlings after treatment with Bacillus sicca BZWQ66 fermentation broth. From Table 4 and Figure 5 It is known that the application of Bacillus sicca BZWQ66 liquid inoculant is safe for seedlings of potatoes, cucumbers, radishes, pumpkins, peanuts, corn, and wheat, and has a significant effect on promoting root length or plant height.

[0064] Example 5: Control effect of Bacillus sicca BZWQ66 liquid inoculant against potato wilt. A microbial inoculant made from Bacillus sicca BZWQ66 was applied to control potato wilt disease in potted potatoes. The tested potato variety was Wotu No. 5. The specific method was as follows: potato seed tubers were cut into pieces, dried, and then planted in pots filled with sandy loam soil. Treatment was applied when the potato seedlings reached a height of approximately 10 cm. The Bacillus sicca BZWQ66 liquid inoculant was diluted 1000 times (viable count 1.90 × 10⁻⁶). 6 After (CFU / mL), it was compared with Fusarium oxysporum, the pathogen of potato wilt ( Fusarium oxysporum KW-F spore suspension (viable count 5.50 × 10⁻⁶) 5 A mixture of CFU / mL was prepared at a 1:1 volume ratio, and 200 mL was inoculated into each pot. Controls were provided by inoculating 200 mL of Fusarium oxysporum KW-F spore suspension and 200 mL of water. Ten pots were used for each treatment, with three replicates. Disease incidence on the roots of potato seedlings under different treatments was assessed 20 days later.

[0065] As shown in Table 5 and Figure 6 As shown, the results indicate that the disease index of the control group was 78.0, the disease index of the treatment group was 12.6, and the disease control efficacy against potato wilt was 83.85%.

[0066] Table 5. Statistical results of the survey on the control of Fusarium wilt in mini-tubers by Bacillus sicca BZWQ66 inoculum. Example 6: Control effect of Bacillus sicca BZWQ66 on potato powdery scab In 2025, a potato powdery scab control experiment was conducted in Shuangaitang Village, Guyuan County, Zhangjiakou City. The experimental plots were potato fields infected with powdery scab that had been continuously cropped for many years. Each treatment area was 66.6 m². 2 The potato variety used in the experiment was Wotu No. 5, and the specific steps were as follows: When sowing on May 8, 2025, Bacillus sicca BZWQ66 solid inoculum (viable count of 4.80 × 10⁻⁶) was applied. 8 Seed dressing (CFU / g) at a rate of 1.5% of tuber weight. During plant growth, administer Bacillus sicca BZWQ66 solid inoculant (4.80 × 10⁻⁶ viable cells). 8 Two drip irrigation treatments were administered (CFU / g, diluted 1000 times with water). The first treatment was applied on July 15, 2025, during the tuber formation stage of the potato plants, and the second treatment was applied on August 10, 2025, during the tuber enlargement stage. The dosage for each treatment was 1.5 kg / mu (approximately 0.067 hectares). Conventional management served as a control. Before potato harvest, a five-point sampling survey was conducted using the diagonal method to count the number of tubers at each stage. The incidence rate, disease index, and control efficacy were calculated.

[0067] As shown in Table 6 and Figure 7 As shown, the experimental results indicate that the incidence of potato powdery scab in the control group of Wotu 5 variety was 83.61%, and the disease index was 47.68. The incidence of potato powdery scab in the treatment group treated with Bacillus sicca BZWQ66 was 55.95%, and the disease index was 17.36. The control efficacy of Bacillus sicca BZWQ66 against potato powdery scab was 63.59%.

[0068] Table 6. Statistical results of the survey on the control of potato powdery scab by biocontrol agents. Example 7: Control effect of Bacillus sicca BZWQ66 on sweet potato root rot The experiment was conducted in Daren Village, Dongluobao Town, Dingxing County, Baoding City, in a field that had been infected with sweet potato root rot for many years. The experimental variety was "Yanshu 25". The treatment area was 66.6 m². 2 At sowing time (May 17, 2025), use Bacillus sicca BZWQ66 solid inoculum (viable count 4.80 × 10⁻⁶). 8 Dip sweet potato seedlings in a solution of Bacillus sicca BZWQ66 solid inoculum (CFU / g, diluted 20 times with water) for 10 seconds during the sweet potato growth period. The inoculum was applied on June 9, 2025, and July 3, 2025 (4.80 × 10⁻⁶ viable cells). 8 Drip irrigation was performed using a solution of CFU / g (diluted 1000 times with water), with a dosage of 1.5 kg / mu per treatment. Conventional production management served as a control. At harvest (October 20, 2025), a five-point sampling survey was conducted using the diagonal method.

[0069] As shown in Table 7 and Figure 8 As shown, the experimental results indicate that the incidence of sweet potato root rot in the control group was 61.48%, and the disease index was 29.93; the incidence of disease in the Bacillus sicca BZWQ66 inoculant treatment group was 26.43%, the disease index was 11.61, and the control effect was 61.21%.

[0070] Table 7. Statistical results of the control experiment of BZWQ66 inoculant against sweet potato root rot. 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 Bacillus sicca ( Bacillus siamensis BZWQ66, characterized in that, The Bacillus sicca BZWQ66 has the accession number CGMCC No. 39538.

2. The use of Bacillus sicca BZWQ66 as described in claim 1 in the preparation of products that promote plant growth and / or control soil-borne diseases.

3. The application according to claim 2, characterized in that, The soil-borne diseases mentioned include potato powdery scab, potato wilt, potato black scurf, sweet potato root rot, potato verticillium wilt, potato early blight, potato scab, and peanut fruit rot.

4. The application according to claim 2, characterized in that, The plants mentioned include potatoes, peanuts, cucumbers, tomatoes, peas, pumpkins, radishes, sweet potatoes, wheat, and corn.

5. The application according to claim 2, characterized in that, The product includes microbial inoculants.

6. A microbial inoculant for promoting plant growth and / or controlling soil-borne diseases, characterized in that, The microbial agent includes Bacillus sicca BZWQ66 as described in claim 1.

7. The microbial agent according to claim 6, characterized in that, The microbial agent is in the form of a liquid agent or a solid agent.

8. The microbial agent according to claim 7, characterized in that, When the microbial agent is in liquid form, the effective viable count of Bacillus sicca BZWQ66 is ≥1.65 × 10⁻⁶. 9 CFU / mL; When the microbial agent is in the form of a solid agent, the effective viable count of the Bacillus sicca BZWQ66 is ≥1.65 × 10⁻⁶. 8 CFU / g.

9. The application of Bacillus sicca BZWQ66 as described in claim 1 or the microbial agent as described in any one of claims 6-8 in the prevention and control of soil-borne diseases.

10. The use of Bacillus sicca BZWQ66 as described in claim 1 or the microbial agent as described in any one of claims 6-8 in inhibiting pathogenic microorganisms.

Images