Application of a strain of bacillus subtilis k8 nanometer selenium-activated bio-pesticide in preventing and treating plant pathogenic fungi
By preparing Bacillus subtilis K8 nano-selenium active bacterial agent, the problems of single biocontrol function and high preparation cost of nano-selenium in the existing technology have been solved, and the dual effects of efficient control of plant diseases and selenium enrichment of crops have been achieved, which is suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANJIN ACAD OF AGRI SCI
- Filing Date
- 2026-04-16
- Publication Date
- 2026-06-05
Smart Images
Figure CN122146500A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of biological control technology for plant diseases, and in particular relates to the application of a Bacillus subtilis K8 nano-selenium active bacterial agent in the control of plant pathogens. Background Technology
[0002] In recent years, with the expansion of greenhouse vegetable cultivation and the increase in greenhouses cultivating cucumbers and tomatoes in the same field, cucumber wilt (pathogen: Fusarium oxysporum ), cucumber gray mold (pathogen: Botrytis cinerea Early blight of tomato (pathogen: Alternaria solani ) and tomato root rot (pathogen: Fusarium solani This disease is common and seriously damaging in both greenhouse agriculture and open-field cultivation. In conditions of high humidity and poor ventilation, once it breaks out, if not controlled promptly, it can cause significant losses, typically reducing yield by 20% to 30%, and in severe cases, causing complete wilting and crop failure. Existing control methods, such as agricultural control through breeding and grafting, as well as chemical spraying and seed soaking, suffer from drawbacks including low efficiency, difficulty in field management, and environmental pollution. Biological control, on the other hand, can effectively control the disease and promote sustainable agricultural development.
[0003] Selenium is an essential trace element for the life activities of organisms, and it has important functions such as enhancing immunity, scavenging free radicals, and antioxidation. In recent years, nano-selenium (SeNPs) has attracted widespread attention in the agricultural field due to its low toxicity, high bioactivity, and slow-release properties. The reduction of highly toxic sodium selenite (Na₂SeO₃) into non-toxic, highly active red nano-selenium using microorganisms is currently a research hotspot in the green synthesis of nano-selenium.
[0004] Bacillus subtilis, an important rhizosphere growth-promoting bacterium, is widely used in biological control due to its ability to produce various antimicrobial substances, compete for ecological niches, induce systemic resistance in plants, and is safe for humans and animals and environmentally friendly. However, different Bacillus subtilis strains exhibit significant differences in their antimicrobial spectrum and biocontrol efficacy. Therefore, isolating and screening new strains with excellent control efficacy against specific important diseases from nature is of great significance for enriching biocontrol resources and developing novel biological pesticides.
[0005] However, the existing technology has the following shortcomings: (1) Most biocontrol Bacillus species have low tolerance and conversion efficiency to sodium selenite, and high-concentration selenium environment will inhibit bacterial growth; (2) Biocontrol function and nano-selenium synthesis function usually belong to different strains, making it difficult to achieve "one strain with two functions"; (3) Patent technology that integrates the functions of nano-selenium synthesis, pathogen inhibition and crop selenium enrichment into a single active bacterial agent is still blank. Summary of the Invention
[0006] In view of this, the purpose of this invention is to provide an active bacterial agent of Bacillus subtilis K8 nano-selenium in the prevention and control of plant pathogens, so as to solve the technical problems of existing biocontrol agents having single function, high cost of nano-selenium preparation, and separation of selenium conversion and biocontrol function.
[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a Bacillus subtilis K8 nano-selenized active bacterial agent, wherein the Bacillus subtilis K8 nano-selenized active bacterial agent is prepared by processing Bacillus subtilis... Bacillus subtilis K8 was obtained by fermentation in a fermentation medium containing sodium selenite; Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
[0008] This invention also provides a method for preparing the aforementioned Bacillus subtilis K8 nano-selenized active bacterial agent, comprising the following steps: (1) Bacillus subtilis Bacillus subtilis K8 was inoculated into LB solid medium and activated during culture. (2) Pick a single colony obtained in step (1) and inoculate it into LB liquid medium, shake and culture to obtain seed culture; (3) Transfer the seed liquid to a fermentation medium containing sodium selenite at an inoculation rate of 1% to 5%, and ferment to obtain nano-selenized active fermentation broth; (4) The nano-selenium active fermentation broth was centrifuged / concentrated / directly diluted to obtain Bacillus subtilis K8 nano-selenium active bacterial agent.
[0009] Preferably, the activation culture temperature in step (1) is 28~32℃, and the activation culture time is 18~30h; The temperature of the shaking culture in step (2) is 28~32℃, the shaking speed is 100~200rpm, and the shaking culture time is 18~30h.
[0010] Preferably, the concentration of sodium selenite in step (3) is 0.1~5.0 mmol / L, the fermentation medium includes the following components at the following concentrations: 5~15 g / L tryptone, 3~8 g / L yeast extract, 5~15 g / L sodium chloride, and the pH of the fermentation medium is 6.5~7.5.
[0011] Preferably, the fermentation temperature in step (3) is 28~35℃, the fermentation speed is 150~200rpm, and the fermentation time is 36~72h.
[0012] This invention also provides Bacillus subtilis Bacillus subtilis Application of K8 or the aforementioned Bacillus subtilis K8 nano-selenized active bacterial agent in the prevention and control of plant diseases, wherein Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
[0013] Preferably, the plant disease is caused by one or more of Fusarium oxysporum, Botrytis cinerea, Alternaria alternata, and Fusarium solani.
[0014] Preferably, the plant diseases include cucumber wilt, cucumber gray mold, tomato early blight, or tomato root rot.
[0015] Preferably, the Bacillus subtilis K8 nano-selenized active bacterial agent is diluted 100 to 800 times and applied as a foliar spray or root irrigation during the crop's growth period or at the early stage of disease onset.
[0016] This invention also provides Bacillus subtilis Bacillus subtilis The application of K8 or the aforementioned Bacillus subtilis K8 nano-selenized active bacterial agent in the preparation of selenium-enriched agricultural products, wherein Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Dual-function strain: The Bacillus subtilis K8 provided by this invention has both broad-spectrum antagonistic activity against plant pathogens and highly efficient sodium selenite reducing ability, making it a dual-function strain that overcomes the shortcomings of traditional technologies that require the combination of biocontrol bacteria and selenium-converting bacteria.
[0018] 2. High selenium tolerance: This strain can still grow normally and transform efficiently in a culture medium with a sodium selenite concentration as high as 5 mM, and its tolerance is significantly better than that of ordinary Bacillus.
[0019] 3. High bacterial activity: The nano-selenized active bacterial agent prepared by this invention has a viable bacteria count ≥102 9 CFU / mL, possessing both the dual antibacterial effects of live biocontrol bacteria and nano-selenium, with a significant synergistic effect.
[0020] 4. Broad application prospects: This microbial agent can not only prevent and control plant diseases, but also simultaneously achieve biological selenium enrichment of crops, producing functional selenium-enriched agricultural products with high added value and environmental friendliness. Attached Figure Description
[0021] Figure 1Example 1 shows the inhibition rates of different Bacillus strains against four plant pathogens; Figure 2 The germination rate of spores of four plant pathogens by different Bacillus strains in Example 2; Figure 3 These are photomicrographs showing the effect of K8 on the spore germination of four plant pathogens in Example 2 (where A is the effect of K8 on the spore germination of cucumber wilt, B is the effect of K8 on the spore germination of cucumber gray mold, C is the effect of K8 on the spore germination of tomato early blight, and D is the effect of K8 on the spore germination of tomato root rot). Figure 4 Photograph of the active bacterial agent after K8 reduction of sodium selenite in Example 3; Figure 5 The effect of different concentrations of sodium selenite on the number of K8 bacteria in Example 3; Figure 6 The inhibition rate of the K8 nano-selenized active bacterial agent in Example 3 against different pathogens; Figure 7 Images showing the antibacterial activity of K8 nano-selenium-modified active bacteria against different pathogens in Example 3 (where A is cucumber gray mold, B is cucumber wilt, C is tomato early blight, and D is tomato root rot). Figure 8 In Example 4, K8 nano-selenized active bacterial agent was used to inoculate pathogens onto the leaves of living plants.
[0022] Biological Preservation Instructions
[0023] The Bacillus subtilis provided by this invention Bacillus subtilis K8 is deposited at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, on April 10, 2020, with accession number CGMCCNo. 19558. Detailed Implementation
[0024] This invention provides a Bacillus subtilis K8 nano-selenized active bacterial agent, wherein the Bacillus subtilis K8 nano-selenized active bacterial agent is prepared by processing Bacillus subtilis... Bacillus subtilis K8 was obtained by fermentation in a fermentation medium containing sodium selenite; Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
[0025] In this invention, the active ingredients in the Bacillus subtilis K8 nano-selenized active bacterial agent include a mixture of Bacillus subtilis K8 cells, spores, fermentation broth, and elemental selenium; the Bacillus subtilis K8 nano-selenized active bacterial agent also includes agriculturally acceptable carriers and adjuvants; the dosage form of the Bacillus subtilis K8 nano-selenized active bacterial agent includes wettable powder, water-dispersible granules, suspension concentrate, or granules.
[0026] This invention also provides a method for preparing the aforementioned Bacillus subtilis K8 nano-selenized active bacterial agent, comprising the following steps: (1) Bacillus subtilis Bacillus subtilis K8 was inoculated into LB solid medium and activated during culture. (2) Pick a single colony obtained in step (1) and inoculate it into LB liquid medium, shake and culture to obtain seed culture; (3) Transfer the seed liquid to a fermentation medium containing sodium selenite at an inoculation rate of 1% to 5%, and ferment to obtain nano-selenized active fermentation broth; (4) The nano-selenium active fermentation broth was centrifuged / concentrated / directly diluted to obtain Bacillus subtilis K8 nano-selenium active bacterial agent.
[0027] In this invention, Bacillus subtilis is used. Bacillus subtilis K8 was inoculated into LB solid medium and activated. The activation temperature was preferably 28-32℃, more preferably 29-31℃, and even more preferably 30℃; the activation time was preferably 18-30h, more preferably 21-27h, and even more preferably 24h.
[0028] In this invention, a single colony obtained from step (1) is picked and inoculated into LB liquid medium, and cultured by shaking to obtain a seed culture; the temperature of the shaking culture is preferably 28~32℃, more preferably 29~31℃, and even more preferably 30℃; the shaking speed is preferably 100~200rpm, more preferably 120~180rpm, and even more preferably 150rpm; the shaking time is preferably 18~30h, more preferably 21~27h, and even more preferably 24h.
[0029] In this invention, the seed liquid is transferred to a fermentation medium containing sodium selenite at an inoculation rate of 1% to 5%, and fermented to obtain a nano-selenized active fermentation broth. The inoculum amount is preferably 2%~4%, more preferably 3%; the concentration of sodium selenite is preferably 0.1~5.0 mmol / L; the fermentation medium comprises the following components at the following concentrations: 5~15 g / L tryptone, 3~8 g / L yeast extract, and 5~15 g / L sodium chloride; the amount of tryptone is preferably 8~12 g / L, more preferably 10 g / L; the amount of yeast extract is preferably 4~7 g / L, even more preferably 5 g / L; the amount of sodium chloride is preferably 8~12 g / L, even more preferably 10 g / L; the pH of the fermentation medium is 6.5~7.5; the fermentation temperature is preferably 28~35℃, more preferably 29~32℃, even more preferably 30℃; the fermentation speed is preferably 120~200 rpm, more preferably 130~180 rpm, even more preferably 150 rpm. The fermentation time is preferably 36-72 h, more preferably 40-50 h, and even more preferably 48 h.
[0030] In this invention, the effective viable count of the Bacillus subtilis K8 nano-selenized active bacterial agent is ≥1.0 × 10⁻⁶. 9 CFU / mL, with nano-selenium content ranging from 300 to 3000 mg / kg.
[0031] This invention also provides Bacillus subtilis Bacillus subtilis Application of K8 or the aforementioned Bacillus subtilis K8 nano-selenized active bacterial agent in the prevention and control of plant diseases, wherein Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
[0032] In this invention, the plant diseases are caused by one or more of Fusarium oxysporum, Botrytis cinerea, Alternaria alternata, and Fusarium solani; the plant diseases include cucumber wilt, cucumber gray mold, tomato early blight, or tomato root rot; the Bacillus subtilis K8 nano-selenized active bacterial agent is diluted 100-800 times and applied as a foliar spray or root drenching during the crop growth period or at the early stage of disease onset; it is applied once every 7-15 days, for 2-3 consecutive applications.
[0033] This invention also provides Bacillus subtilis Bacillus subtilis The application of K8 or the aforementioned Bacillus subtilis K8 nano-selenized active bacterial agent in the preparation of selenium-enriched agricultural products, wherein Bacillus subtilis Bacillus subtilisK8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
[0034] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0035] Example 1
[0036] Screening of Bacillus antibacterial properties
[0037] 1. Preparation of pathogens
[0038] Prepare PDA medium (1 L): 200.0 g peeled potato, 20.0 g glucose, 18-20 g agar, distilled water to a final volume of 1 L, sterilize at 115℃ for 20 min; cool to 60℃, pour into 85 mm sterile petri dishes to make PDA plates, inoculate with plant pathogen mycelia, incubate at 25℃ for 5 days, and use when the mycelia have covered the petri dishes.
[0039] 2. Preparation of Bacillus fermentation broth
[0040] Prepare a liquid culture medium with 1% peptone, 1% soluble starch, 0.3% sodium chloride, 0.1% dipotassium hydrogen sulfate, and 0.1% magnesium sulfate, bringing the volume to 1 L. Dispense 100 mL into 250 mL Erlenmeyer flasks and sterilize at 121°C for 20 min. Inoculate different preserved Bacillus strains into the liquid culture medium cooled to 30°C and incubate at 30°C for 2 days. Determine the bacterial count when it reaches 10⁻⁶. 9 The probiotic fermentation broth can be obtained at CFU / mL.
[0041] 3. In vitro antibacterial test – Oxford cup method
[0042] Antagonistic bacteria were initially screened using the plate confrontation method. Holes were punched at the edge of the plant pathogen using a 6 mm diameter punch, and the bacterial blocks were inoculated into the center of a PDA plate. Probiotic fermentation broth (Oxford cups) was symmetrically inoculated 2 cm away from the pathogen. Petri dishes without probiotic fermentation broth served as controls. Each treatment had three replicates, and the plates were incubated in the dark at 25°C. When the diameter of the pathogen in the control group reached 3 / 4 of the petri dish diameter, the diameter of the pathogen colony was measured using the cross-sectional method.
[0043] Experimental results: such as Figure 1As shown, eight Bacillus strains exhibited significant inhibitory effects against the pathogens. Among them, six Bacillus strains showed inhibition rates exceeding 50% against four pathogens. K8 showed the best inhibitory effect, with inhibition rates of 68.57%, 67.14%, 56.46%, and 65.86% against cucumber wilt, cucumber gray mold, tomato early blight, and tomato root rot, respectively.
[0044] Example 2
[0045] The effect of Bacillus inoculum on the germination of plant pathogen spores
[0046] Preparation of spore suspension. Following Example 1, the fungus was cultured to the spore formation stage in the first step. The fungal colonies were covered with sterile physiological saline (0.9% NaCl solution). The surface of the fungal colonies was gently scraped with a sterile glass rod or inoculation loop to allow spores to mix into the liquid. The spore-containing liquid was transferred to a sterile centrifuge tube and centrifuged at low speed (approximately 3000-5000 rpm) for several minutes to precipitate the spores and remove colony debris and culture medium residue. The supernatant was discarded, and the spore precipitate was gently resuspended with sterile physiological saline or other suitable buffer. After resuspending the spores, the spore concentration could be determined by counting using an optical microscope. The prepared spore suspension could be stored for a short period at low temperature (4°C).
[0047] 10 μL of sterile sucrose solution (0.1% by mass) was added to a concave glass slide, followed by 10 μL of sterile Bacillus filtrate and then 10 μL of fungal spore solution. A control group without sterile filtrate was used. Each treatment was repeated three times. After treatment, the slides were placed in petri dishes lined with moist filter paper, covered, and incubated at 25°C. Spore germination was assessed after 10 h, with germination defined as when the germ tube length exceeded half the diameter of the spore tip. Three replicates were performed for each treatment, and the spore germination rate was calculated.
[0048] Experimental results: such as Figure 2 As shown, eight Bacillus strains significantly inhibited spore germination of the pathogens. Among them, K8 showed the best antibacterial effect, with spore germination rates of only 3.25%, 1.26%, 16.46%, and 18.95% against cucumber wilt, cucumber gray mold, tomato early blight, and tomato root rot, respectively. Microscopic images of spore germination are shown below. Figure 3 As shown.
[0049] Example 3
[0050] The inhibitory effect of Bacillus subtilis K8 nano-selenium active bacterial agent on plant pathogens
[0051] Bacillus subtilis K8 was activated, and the seed culture was transferred to LB medium containing sodium selenite at an inoculation rate of 3%. Five concentrations of sodium selenite were used: 0, 0.1, 1, 2, and 5 mM. The medium was cultured at 30℃ and 150 rpm with shaking for 48 hours. The fermentation broth gradually turned red / brick red, yielding different concentrations of nano-selenized active fermentation broth (e.g., ...). Figure 4 As shown in the figure, a comparative experiment was conducted using the plate confrontation method to determine the antibacterial effect of K8 bacterial solutions fermented with different concentrations of sodium selenite on plant pathogens.
[0052] The bacterial count after K8 fermentation in sodium selenite culture media of different concentrations is as follows: Figure 5 As shown, the results indicate that the bacterial count of strain K8 was 9.67 × 10⁻⁶ in the absence of sodium selenite (0 mmol / L). 8 CFU / mL, low concentration of sodium selenite (0.1 mmol / L) significantly promoted the growth of strain K8, increasing the bacterial count to 19.6 × 10⁻⁶. 8 CFU / mL, when the sodium selenite concentration is ≥1 mmol / L, significantly inhibits the growth of K8.
[0053] Different concentrations of nano-selenium-enriched bacterial solutions exhibit varying inhibition rates against different pathogens, as shown in the following results. Figure 6 As shown in the image, the low-concentration sodium selenite (0.1 mmol / L) fermentation broth exhibited inhibition rates of 71.76% against cucumber wilt, 70.58% against cucumber gray mold, 76.47% against tomato early blight, and 68.15% against tomato root rot, respectively. These rates were significantly higher than the control without sodium selenite. However, when the sodium selenite concentration was ≥1 mmol / L, there was no significant difference in inhibition rate between the broth and the control. This indicates that low-concentration nano-selenium-based bacterial agents can improve the inhibition rate of the bacterial broth. Antibacterial photos are shown below. Figure 7 As shown.
[0054] Example 4
[0055] Antibacterial effect of Bacillus subtilis nano-selenium active bacterial agent on plant leaves
[0056] Pick plant leaves of similar size and shape, rinse the leaf surface clean, first soak them in 75% alcohol for 1 minute for surface disinfection, and then wash them with sterile water 3 to 5 times. The fermentation broth of the tested active bacteria was diluted 10 times, and the leaves were soaked for 2 hours and then dried. Sterile water treatment was used as a control. Wounds were made on the leaves with a sterile needle. Each treatment consisted of 6 true leaves, and the treatment was repeated 6 times.
[0057] Use a punch to make holes in the pathogen plate, pick up the fungal cake and place it on the wound of the leaf; After being placed in a 25℃ incubator for 2 days, the size and length of leaf lesions were observed, and the inhibition effect was calculated using a formula.
[0058] Inhibition effect (%) = (Length of control lesion - Length of treated lesion) / (Length of control lesion - Diameter of mycelial cake) × 100
[0059] Experimental results: such as Figure 8 As shown, K8 nano-selenium-modified bacterial agent has a good inhibitory effect on tomato early blight strains inoculated on detached leaves, especially at a concentration of 0.1 mmol / L, the inhibitory effect reaches more than 90%.
[0060] As can be seen from the above embodiments, the Bacillus subtilis K8 and its nano-selenized active bacterial agent provided by the present invention can effectively prevent and control plant diseases, with low cost and suitable for large-scale production.
[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A Bacillus subtilis K8 nano-selenized active bacterial agent, characterized in that, The Bacillus subtilis K8 nano-selenium active bacterial agent is Bacillus subtilis K8 nano-selenium active bacterial agent. Bacillus subtilis K8 was obtained by fermentation in a fermentation medium containing sodium selenite; Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
2. The method for preparing the Bacillus subtilis K8 nano-selenized active bacterial agent according to claim 1, characterized in that, Includes the following steps: (1) Bacillus subtilis Bacillus subtilis K8 was inoculated into LB solid medium and activated during culture. (2) Pick a single colony obtained in step (1) and inoculate it into LB liquid medium, shake and culture to obtain seed culture; (3) Transfer the seed liquid to a fermentation medium containing sodium selenite at an inoculation rate of 1% to 5%, and ferment to obtain nano-selenized active fermentation broth; (4) The nano-selenium active fermentation broth was centrifuged / concentrated / directly diluted to obtain Bacillus subtilis K8 nano-selenium active bacterial agent.
3. The preparation method according to claim 2, characterized in that, The activation culture temperature in step (1) is 28~32℃, and the activation culture time is 18~30h; The temperature of the shaking culture in step (2) is 28~32℃, the shaking speed is 100~200rpm, and the shaking culture time is 18~30h.
4. The preparation method according to claim 2, characterized in that, The concentration of sodium selenite in step (3) is 0.1~5.0 mmol / L, and the fermentation medium includes the following components at the following concentrations: 5~15 g / L tryptone, 3~8 g / L yeast extract, and 5~15 g / L sodium chloride. The pH of the fermentation medium is 6.5~7.
5.
5. The preparation method according to claim 2, characterized in that, The fermentation temperature in step (3) is 28~35℃, the fermentation speed is 150~200rpm, and the fermentation time is 36~72h.
6. Bacillus subtilis Bacillus subtilis The application of K8 or the Bacillus subtilis K8 nano-selenized active bacterial agent according to claim 1 in the prevention and control of plant diseases, characterized in that... Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.
7. The application according to claim 6, characterized in that, The plant diseases mentioned are caused by one or more of the following fungi: Fusarium oxysporum, Botrytis cinerea, Alternaria alternata, and Fusarium solani.
8. The application according to claim 7, characterized in that, The plant diseases mentioned include cucumber wilt, cucumber gray mold, tomato early blight, or tomato root rot.
9. The application according to claim 6, characterized in that, The Bacillus subtilis K8 nano-selenized active bacterial agent is diluted 100-800 times and applied as a foliar spray or root irrigation during the crop's growth period or at the early stage of disease onset.
10. Bacillus subtilis Bacillus subtilis The application of K8 or the Bacillus subtilis K8 nano-selenized active bacterial agent according to claim 1 in the preparation of selenium-enriched agricultural products, characterized in that... Bacillus subtilis Bacillus subtilis K8 was deposited on April 10, 2020, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 19558.