Pseudomonas for antagonizing ralstonia solanacearum and application of pseudomonas

Abstract

The invention discloses pseudomonas for antagonizing ralstonia solanacearum and application thereof, and belongs to the technical field of microorganisms. The Pseudomonas sp. SHP-38 disclosed by the invention is preserved in the China General Microbiological Culture Collection Center (CGMCC), the preservation date is January 19, 2026, and the preservation number is CGMCC No.37456. The Pseudomonas sp. SHP-38 disclosed by the invention has the advantages that the preservation number is CGMCC No.37456; through physiological and biochemical identification and molecular taxonomy identification, it is confirmed that the pseudomonas SHP-38 belongs to a new species of pseudomonas, and species resources and genetic diversity of pseudomonas flora are expanded. The pseudomonas sp. SHP-38 has double effects of inhibiting the growth of ralstonia solanacearum and promoting the growth of plants, has the potential of being developed into a microbial agent for the eucalyptus bacterial wilt, is beneficial to reducing the use of chemical pesticides, provides a new biological control technology for solving the eucalyptus bacterial wilt, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to a Pseudomonas strain antagonistic to Ralstonia solanacearum and its applications. Background Technology

[0002] Eucalyptus (Eucalyptus spp.) is a general term for plants in the genus Eucalyptus of the family Myrtaceae. As one of the world's three major fast-growing timber tree species, eucalyptus has strong environmental adaptability and ecological stability, and has therefore been widely introduced and cultivated in many regions around the world.

[0003] Eucalyptus bacterial wilt is a systemic vascular bacterial disease caused by *Ralstonia solanacearum*, a member of the Solanaceae family. This pathogen invades the host's root system through the soil and then spreads systematically within the plant's vascular tissue, leading to acute wilting and ultimately the death of the entire plant. This disease severely restricts the development of the eucalyptus industry and has caused significant economic losses. Traditional chemical control methods, with long-term use, not only pollute the environment but may also lead to drug resistance in the pathogen. Therefore, developing greener, safer, and more efficient biological control methods using biocontrol-capable microbial strains has become a key research focus. Summary of the Invention

[0004] The purpose of this invention is to provide a *Pseudomonas* strain antagonistic to *Ralstonia solanacearum* and its applications, thereby addressing the problems existing in the prior art. This invention discovers a new species of *Pseudomonas*, *Pseudomonas* sp. SHP-38, which exhibits antagonistic activity against *Ralstonia solanacearum*, expanding the species resources and genetic diversity of the *Pseudomonas* genus. This *Pseudomonas* sp. SHP-38 has a dual effect of inhibiting the growth of *Ralstonia solanacearum* and promoting plant growth, showing potential for development into a microbial agent targeting *Ralstonia solanacearum* disease. This would help reduce the use of chemical pesticides, promote environmental friendliness and sustainable development, and provide a new biological control technology for *Ralstonia solanacearum* disease, with broad application prospects.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a strain of Pseudomonas sp. SHP-38, deposited at the China General Microbiological Culture Collection Center (CGMCC) on January 19, 2026, with accession number CGMCC No. 37456, and the deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0007] The present invention also provides the application of the above-mentioned Pseudomonas SHP-38 in the preparation of microbial agents antagonizing Ralstonia solanacearum.

[0008] The present invention also provides a microbial agent for antagonizing Bacillus eucalyptus, the microbial agent comprising the above-mentioned Pseudomonas SHP-38, the fermentation broth of the above-mentioned Pseudomonas SHP-38, or the metabolites of the above-mentioned Pseudomonas SHP-38.

[0009] The present invention also provides the application of the above-mentioned Pseudomonas SHP-38 or the above-mentioned microbial agent in inhibiting the growth of Ralstonia solanacearum.

[0010] The present invention also provides the application of the above-mentioned Pseudomonas SHP-38 or the above-mentioned microbial inoculant in the prevention and control of bacterial wilt of plants.

[0011] The present invention also provides the application of the above-mentioned Pseudomonas SHP-38 or the above-mentioned microbial agent in the preparation of products for the prevention and control of bacterial wilt of plants.

[0012] The present invention also provides the application of the above-mentioned Pseudomonas SHP-38 or the above-mentioned microbial inoculants in promoting plant growth.

[0013] The present invention also provides the application of the above-mentioned Pseudomonas SHP-38 or the above-mentioned microbial inoculant in the preparation of plant growth promoters.

[0014] Furthermore, the plant includes eucalyptus.

[0015] The present invention also provides a product for preventing and controlling bacterial wilt of plants, the product containing the above-mentioned Pseudomonas SHP-38 or the above-mentioned microbial agent.

[0016] The present invention discloses the following technical effects:

[0017] This invention obtained a new species of Pseudomonas sp., SHP-38, which exhibits antagonistic activity against Ralstonia solanacearum. Physiological, biochemical, and molecular taxonomic identification confirmed that SHP-38 belongs to the genus Pseudomonas. Antagonistic experiments revealed that the inhibition zone diameter of SHP-38 against Ralstonia solanacearum was no less than 30 mm. Further analysis confirmed that SHP-38 inhibits biofilm formation and flagella-mediated migration of the pathogen, thereby weakening its colonization efficiency and reducing its pathogenicity. Simultaneously, SHP-38 also has a certain growth-promoting effect, increasing the height and root length of eucalyptus seedlings, thus achieving a dual beneficial effect of "disease resistance and growth promotion."

[0018] This invention discovers a new species of Pseudomonas microorganism with antagonistic activity against bacterial wilt of eucalyptus, expanding the species resources and genetic diversity of the Pseudomonas genus. It also provides a basis for the safety and effectiveness of developing microbial agents for bacterial wilt of eucalyptus, which is conducive to reducing the use of chemical pesticides, promoting environmental friendliness and sustainable development, and providing a new biological control technology for solving bacterial wilt of eucalyptus with broad application prospects. 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 The graph shows the inhibitory effect of Pseudomonas SHP-38 on Ralstonia solanacearum; where A is the blank control group and B is Pseudomonas SHP-38.

[0021] Figure 2 The images show the morphological observations of Pseudomonas SHP-38; where A is a plate morphology image; B is a single colony morphology image, with a scale bar of 200 μm; and C is a Gram staining result image.

[0022] Figure 3 Phylogenetic tree diagram of Pseudomonas SHP-38;

[0023] Figure 4 The graph shows the effect of the active fermentation broth of Pseudomonas SHP-38 on the growth curve of the pathogen of bacterial wilt; R represents the control group and R+38 represents the experimental group.

[0024] Figure 5 The figure shows the effect of Pseudomonas SHP-38 on Ralstonia solanacearum biofilm formation; where A represents the Ralstonia solanacearum biofilm in the control group (scale bar 200 μm); B represents the Ralstonia solanacearum biofilm in the treatment group (scale bar 200 μm); and C represents the biofilm formation OD in the control and treatment groups. 595 Absorbance values; CK represents the control group, and 38 represents the treatment group;

[0025] Figure 6 The figure shows the effect of Pseudomonas SHP-38 on the motility of Ralstonia solanacearum; where A and B represent the motility of Ralstonia solanacearum in the treatment group; C and D represent the motility of Ralstonia solanacearum in the control group; E represents the diameter of colony growth on the culture medium; CK represents the control group and 38 represents the treatment group.

[0026] Figure 7The graph shows the antibacterial effect of Pseudomonas SHP-38 under different culture medium conditions; where A, B, C, D and E are Pseudomonas SHP-38 under LB, LBD, LBG, LBP and LBY culture medium conditions, respectively; F, G, H, I and J are blank control groups under LB, LBD, LBG, LBP and LBY culture medium conditions, respectively.

[0027] Figure 8 The figure shows the effect of Pseudomonas SHP-38 on seedling growth; where A represents the average change in seedling root length; B represents the average change in seedling height; C represents the average change in seedling leaf length; D represents the average change in seedling leaf width; CK represents the control group, and 38 represents the treatment group. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] Unless otherwise specified, the biological materials or reagents involved in the following embodiments can be purchased through conventional channels; the experimental methods involved are conventional technical methods in the field unless otherwise specified.

[0034] The basal culture medium formulations used in the following examples are as follows:

[0035] LB medium: peptone 10.0 g / L, sodium chloride 5.0 g / L, yeast extract 5.0 g / L, agar powder 15.0 g / L.

[0036] NA medium: peptone 10.0 g / L, sodium chloride 5.0 g / L, beef extract powder 3.0 g / L, agar powder 15.0 g / L.

[0037] PDA medium: 200.0 g / L peeled potato, 20.0 g / L glucose, 15.0 g / L agar powder.

[0038] V8 medium: V8 juice 100.0 mL / L, agar powder 20.0 g / L, calcium carbonate 3.0 g / L.

[0039] CMA medium: corn flour 10.0 g / L, agar powder 15.0 g / L.

[0040] Example 1: Isolation, screening, and identification of strains

[0041] 1. Isolation and screening of strain SHP-38

[0042] Soil samples were collected from healthy forest areas in eucalyptus forests severely affected by bacterial wilt in Qingyuan City, Guangdong Province. Rhizosphere soil samples with roots were taken and placed in conical flasks containing appropriate amounts of sterile water and sterile steel balls. The flasks were shaken at 160 rpm for 20 min to obtain a rhizosphere soil suspension. A 10-fold serial dilution method was used to obtain 10... -1 10 -2 10 -3 10 -4 Four gradients of soil suspension dilutions were prepared. 80 μL of each gradient dilution was spread evenly onto LB, NA, PDA, V8, and CMA media using a sterile spreader. The media were then sealed and incubated upside down at 28°C. After 2 days of observation, single colonies of different morphologies were purified onto their respective solid media using the streak plate method. The purified colonies were stored in 50% glycerol tubes at -20°C for long-term preservation.

[0043] Antagonistic strains were screened using the disk diffusion method. Single colonies of the obtained strains were picked and placed in centrifuge tubes containing 1 mL of LB liquid medium. 0.5 cm diameter filter paper discs were added to the centrifuge tubes, and the mixtures were incubated at 28°C and 180 rpm for 48 h to obtain the bacterial suspension filter paper discs. Single colonies of *Ralstonia solanacearum* were picked and placed in an appropriate amount of LB liquid medium, and incubated at 28°C and 180 rpm for 24 h to obtain the pathogen suspension. LB solid medium was melted by heating and cooled to 50°C. The pathogen suspension was mixed with LB solid medium at a ratio of 1:10 (v / v) and poured into petri dishes. The mixture was allowed to solidify, yielding a plate containing live pathogens. Filter paper discs containing the bacterial suspension were symmetrically placed at four points on the plates. Filter paper discs inoculated only with LB liquid medium served as a blank control group. The plates were incubated upside down at 28°C for 2-3 days. The presence and size of transparent inhibition zones were compared to preliminarily screen for strains antagonistic to *Ralstonia solanacearum*. Strains with good initial screening results were selected, and a bacterial suspension filter paper disc was placed in the center of each plate using the disc diffusion method (3 replicates). The plates were incubated upside down at 28°C for secondary screening, and the results were observed. Finally, strains with significant antagonistic effects were selected. Figure 1 It was named SHP-38, and its average inhibition zone diameter can reach 3.120 cm.

[0044] 2. Morphological and physiological-biochemical identification of strain SHP-38

[0045] Strain SHP-38 was inoculated onto LB agar plates, and its morphological characteristics were observed. Colonies were pale yellow, round, with regular edges, smooth and glossy surfaces, and opaque. Figure 2 (A and B). Gram reaction is negative, and the bacteria are short rod-shaped ( Figure 2 (C). The physiological and biochemical characteristics of SHP-38 are shown in Table 1. The results show that this strain is a Gram-negative bacterium.

[0046] Table 1. Biological characteristics of strain SHP-38

[0047]

[0048] 3. Molecular taxonomic identification of strain SHP-38

[0049] DNA was extracted from this strain using a boiling method, and the 16S rRNA gene of the strain was amplified and sequenced. PCR reactions were performed in a 25 μL system containing: 1 μL each of forward and reverse primers (27F and 1492R), 12.5 μL of 2× premix, 2 μL of DNA template, and double-distilled water to a final volume of 25 μL. The universal primers used for amplification were: 27F sequence: 5'-AGAGTTTGATCCTGGCTCAG-3' (SEQ ID NO.1), and 1492R sequence: 5'-GGTTACCTTGTTACGACTT-3' (SEQ ID NO.2). The reaction was performed according to the following program: 94℃ pre-denaturation for 5 min; 94℃ denaturation for 30 s, 55℃ annealing for 30 s, 72℃ extension for 45 s, 30 cycles; and a final extension at 72℃ for 10 min. PCR products were stored at 4℃. The PCR products were sent to the Sanger sequencing laboratory of Beijing Nosai Genome Research Center Co., Ltd. for sequencing. The obtained sequencing sequences were assembled using SEQMAN software to obtain the complete 16S rRNA gene sequence (SEQ ID NO.3). Subsequently, the sequences were aligned and cut using MEGA 6.0 software, and a phylogenetic tree was constructed using FigTree software. Figure 3 (This is used to analyze its phylogenetic position).

[0050] In the phylogenetic tree, maximum likelihood analysis formed a separate branch with 100% support. SHP-38 is closely related to Pseudomonas fitomaticsae FIT81 T and Pseudomonas glycinae MS586 T. However, SHP-38 differs fundamentally from Pseudomonas fitomaticsae FIT81 T and Pseudomonas glycinae MS586 T in core physiological and biochemical characteristics such as heat tolerance, salt tolerance, and colony color. Among them, strain SHP-38 exhibits pale yellow colonies and demonstrates high heat resistance and broad-spectrum salt tolerance, still growing at 60℃ and in sodium chloride environments ranging from 2% to 10%. Strain Pseudomonas fitomaticsae FIT81 T, however, cannot grow at a culture temperature of 37℃ and has weak salt tolerance, tolerating 4% NaCl, with white colonies (see the literature "Pseudomonas fitomaticsae sp. nov., isolated at Marimurtra Botanical Garden in Blanes, Catalonia, Spain"). Pseudomonas glycinae MS586 T is intolerant of high temperatures (40℃) and cannot grow in 7% NaCl environments (see the literature "Pseudomonas glycinae sp. nov. isolated from the soybeanrhizosphere"). Based on morphological observation, physiological and biochemical characteristics, and molecular taxonomic identification results, this strain was comprehensively determined to be a new species of the genus Pseudomonas sp.

[0051] The strain was named Pseudomonas sp. SHP-38 and was deposited on January 19, 2026, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 37456, located at Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0052] SEQ ID NO.3:

[0053]

[0054] Example 2: Effect of Pseudomonas SHP-38 active fermentation broth on the growth of Ralstonia solanacearum.

[0055] (1) Preparation of bacterial culture and active fermentation broth

[0056] Preparation of active fermentation broth of Pseudomonas SHP-38: Activate Pseudomonas SHP-38, pick a single colony growing on the plate and inoculate it into LB liquid medium, ferment and culture at 28℃ and 180 rpm for 5 days. Filter the fermentation broth once with filter paper, and take the supernatant and filter it a second time with a 0.22 μm filter membrane to obtain the active fermentation broth of SHP-38.

[0057] Preparation of pathogenic fungal solution: Activate Ralstonia solanacearum, pick a single colony from the plate and place it in LB liquid medium, and incubate at 30℃ and 180 rpm for 10 h to obtain the pathogenic fungal solution for bacterial wilt.

[0058] (2) Effect of SHP-38 active fermentation broth on the growth curve of bacterial wilt pathogen

[0059] Experimental group: 15 mL of SHP-38 active fermentation broth and 80 μL of pathogenic bacteria solution were added to 40 mL of LB liquid medium and mixed evenly. The mixture was then placed in a shaker at 180 rpm and 30℃ and incubated in triplicate.

[0060] Control group: 100 μL of pathogenic bacterial solution was added to 55 mL of LB liquid medium and mixed well. The mixture was then incubated on a shaker at 180 rpm and 30 °C for 3 replicates.

[0061] Samples were taken every 4 hours to measure the concentration (OD) of Ralstonia solanacearum in the bacterial solution. 600 By comparing the changes in the concentration of *Ralstonia solanacearum* bacterial broth in different groups, growth curves were plotted. The results showed that the growth of *Ralstonia solanacearum* pathogen treated with *Pseudomonas aeruginosa* SHP-38 active fermentation broth was significantly lower than that in the control group, indicating that *Pseudomonas aeruginosa* SHP-38 active fermentation broth has a certain inhibitory effect on the growth of *Ralstonia solanacearum* pathogen. Figure 4 ).

[0062] Example 3: Effect of Pseudomonas SHP-38 active fermentation broth on biofilm formation of Ralstonia solanacearum

[0063] To evaluate the inhibitory effect of Pseudomonas SHP-38 on the biofilm formation ability of Ralstonia solanacearum, this example uses crystal violet staining for quantitative and qualitative analysis.

[0064] The experiment included a treatment group and a control group. In the treatment group, 800 μL of SHP-38 active fermentation broth (Example 2) and 200 μL of *Ralstonia solanacearum* suspension were added to 24-well plates, and NB medium was added to bring the total volume to 1.5 mL. In the control group, 200 μL of *Ralstonia solanacearum* suspension was added to 24-well plates, and NB medium was added to bring the total volume to 1.5 mL. The 24-well plates were incubated at 28°C for 24 h. After incubation, the supernatant was removed from the wells, and the plates were washed once with 1×PBS buffer to remove unattached cells. 200 μL of standard methanol solution was added for fixation for 15 min, followed by two washes with 1×PBS buffer to remove the fixative. Subsequently, 200 μL of 0.1% crystal violet staining solution was added to each well for staining, and after standing for 15 min, the plates were washed twice again with 1×PBS buffer and dried at room temperature for 30 min. To quantify biofilm biomass, 200 μL of 95% ethanol was added to dissolve crystal violet bound to the biofilm. After 30 min of incubation, the absorbance at 595 nm was measured using an ELISA reader. This value directly reflects the amount of biofilm formed. The experiment was repeated three times.

[0065] Microscopic observation results showed that, compared with the control group, the biofilm structure formed by the Ralstonia solanacearum suspension treated with SHP-38 fermentation broth became sparse, its integrity was damaged, and it was difficult to form a continuous and uniform membrane structure. Figure 5 (A and B). Quantitative results further confirmed that the absorbance of the treatment group at 595 nm was lower than that of the control group, indicating that Pseudomonas SHP-38 can effectively inhibit the formation of biofilm of bacterial wilt pathogen (Ralstonia solanacearum). Figure 5 (C). In summary, Pseudomonas SHP-38 can weaken the colonization ability of Ralstonia solanacearum biofilm by disrupting its structural integrity, thereby reducing the pathogenicity of the pathogen.

[0066] Example 4: Effect of Pseudomonas SHP-38 active fermentation broth on the motility of Ralstonia solanacearum.

[0067] Flagella-mediated migration is one of the key factors for Ralstonia solanacearum to colonize and infect host roots. To evaluate the inhibitory effect of Pseudomonas aeruginosa SHP-38 on the motility of this pathogen, this example uses a semi-solid culture medium method to analyze the effect of SHP-38 active fermentation broth on the migration behavior of Ralstonia solanacearum.

[0068] The experiment included a treatment group and a control group. The treatment group received a mixture of 2 mL SHP-38 active fermentation broth and 8 mL of *Ralstonia solanacearum* bacterial suspension, while the control group received an equal volume of TSB medium instead of the fermentation broth. Both groups were cultured at 28℃ and 180 rpm with shaking for 48 h. Subsequently, 5 μL of the bacterial suspension from both the treatment and control groups was inoculated onto the surface of NB semi-solid medium, inverted, and incubated statically at 28℃ for 12 h. Colony morphology was observed, and colony migration diameter was measured using the cross-crossing method. Each treatment was repeated three times.

[0069] The results showed that the colony migration diameter in the SHP-38 active fermentation broth treatment group was significantly smaller than that in the control group. Figure 6 (AD). Calculation of colony diameter (the difference between the treated and control groups after 12 h of treatment) revealed that SHP-38 active fermentation broth treatment significantly inhibited the migratory diffusion ability of the bacterial wilt pathogen. Figure 6 (E). The above results indicate that Pseudomonas SHP-38 can weaken the colonization efficiency of Ralstonia solanacearum to some extent by interfering with flagella-driven motility, thereby reducing its pathogenic potential.

[0070] Example 5: Effect of different culture medium components on the antibacterial effect of Pseudomonas SHP-38

[0071] To evaluate the effect of different culture medium components on the antibacterial effect of Pseudomonas SHP-38, this example uses the paper disc diffusion method. Single colonies of SHP-38 strain were picked and placed in centrifuge tubes containing 1 mL of LB, LBD, LBP, LBY, and LBG liquid culture medium. 0.5 cm diameter filter paper discs were added to the centrifuge tubes, and the cultures were incubated at 28°C and 180 rpm for 48 h to obtain SHP-38 bacterial suspension filter paper discs (different culture media and their components are shown in Table 2). Single colonies of the pathogen were picked and placed in an appropriate amount of LB liquid culture medium, and incubated at 28°C and 180 rpm for 24 h to obtain the pathogen suspension. LB, LBD, LBP, LBY, and LBG solid culture media were heated to melt, cooled to 50°C, and mixed with the pathogen suspension at a ratio of 1:10 (v / v) in petri dishes. The mixture was then cooled to a solid state to obtain agar plates containing live pathogen bacteria. Using the paper disc diffusion method, a filter paper disc containing a suspension of SHP-38 bacteria of the corresponding culture medium was placed in the center of each plate, with 3 replicates. The plates were incubated upside down at 28°C, and the results were observed.

[0072] Table 2 Different culture media and their components

[0073]

[0074] The results showed that the composition of the culture medium had a significant impact on the antibacterial ability of the strains. Among the tested media, LBP medium showed the best antibacterial effect, while LBY, LBD, and the basal medium LB showed almost the same effect. LBG medium, however, had a certain inhibitory effect on the antibacterial effect (Table 3). Adding a certain amount of dipotassium hydrogen phosphate as an additional inorganic salt to LB medium significantly increased the antibacterial effect. Figure 7 This indicates that suitable inorganic salts can significantly improve the antibacterial effect, and suitable nitrogen sources can improve the antibacterial effect to a certain extent.

[0075] Table 3. Effects of different culture media on antibacterial activity

[0076]

[0077] Example 6: Effects of Pseudomonas SHP-38 active fermentation broth treatment on eucalyptus seedling growth

[0078] To assess the potential ecosafety of Pseudomonas SHP-38 to host plants, this example analyzed the effects of the active fermentation broth of this strain on the growth and development of eucalyptus seedlings. Seedlings with uniform growth were selected, and root length, seedling height, leaf length, and leaf width were measured before cultivation. The roots of the eucalyptus seedlings were irrigated with the active fermentation broth of SHP-38 (Example 2) every two days, keeping the soil moist. An equal amount of water was used as a control group. After a certain period of time, the growth of seedlings in each group was observed and recorded, with 10 replicates per group.

[0079] The results showed that the average changes in root length, seedling height, leaf length, and leaf width of the shoots treated with the SHP-38 active fermentation broth were greater than those in the control group. Regarding root growth, after 10 days of culture, the average change in root length of the control group was 0.16 cm, while the average change in root length of the SHP-38 active fermentation broth treatment group was 0.19 cm. Figure 8 (A); The average change in seedling height in the control group was 0.81 cm, while the average change in seedling height in the SHP-38 active fermentation broth treatment group was 1.27 cm. Figure 8 (B); The average change in leaf length of the control group was 0.85 mm, while the average change in leaf length of the SHP-38 active fermentation broth treatment group was 1.17 mm. Figure 8 (C); The average change in leaf width of the control group seedlings was 0.31 mm, while the average change in leaf width of the SHP-38 active fermentation broth treatment group was 0.39 mm. Figure 8 (D). The above results indicate that the active fermentation broth of Pseudomonas SHP-38 can promote the growth of eucalyptus seedlings to a certain extent, and has no inhibitory effect on the growth and development of various parts, showing good application potential of biocontrol strains, and providing a basis for the safety and effectiveness of developing microbial agents for eucalyptus bacterial wilt.

[0080] 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 Pseudomonas sp. SHP-38, characterized in that, It is deposited at the China General Microbiological Culture Collection Center (CGMCC) on January 19, 2026, with accession number CGMCC No. 37456, at the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Beichen West Road, Chaoyang District, Beijing.

2. The use of the Pseudomonas SHP-38 of claim 1 in the preparation of a microbial agent antagonizing Ralstonia solanacearum.

3. A microbial inoculant antagonizing *Ralstonia solanacearum*, characterized in that, The microbial agent comprises the Pseudomonas SHP-38 of claim 1, the fermentation broth of the Pseudomonas SHP-38, or the metabolites of the Pseudomonas SHP-38.

4. The application of the Pseudomonas SHP-38 of claim 1 or the microbial agent of claim 3 in inhibiting the growth of Ralstonia solanacearum.

5. The application of the Pseudomonas SHP-38 of claim 1 or the microbial agent of claim 3 in the prevention and control of bacterial wilt in plants.

6. The use of the Pseudomonas SHP-38 of claim 1 or the microbial agent of claim 3 in the preparation of products for the prevention and control of bacterial wilt of plants.

7. The application of the Pseudomonas SHP-38 of claim 1 or the microbial agent of claim 3 in promoting plant growth.

8. The use of the Pseudomonas SHP-38 of claim 1 or the microbial agent of claim 3 in the preparation of plant growth promoters.

9. The application according to any one of claims 5-8, characterized in that, The plants mentioned include eucalyptus trees.

10. A product for preventing and controlling bacterial wilt in plants, characterized in that, The product contains either the Pseudomonas SHP-38 of claim 1 or the microbial agent of claim 3.

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