Burkholderia cepacia S16-7 and application thereof

Abstract

This invention relates to the field of microbiology and biological control technology, and discloses a strain of Burkholderia viminalis (Vietnam Burkholderia violacea). Burkholderia cepacia Burkholderia S16-7 and its applications: This strain was deposited on August 21, 2025, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing, with accession number CGMCC NO. 35697. Burkholderia S16-7 exhibits broad-spectrum antibacterial activity, simultaneously inhibiting multiple types of pathogens, including Staphylococcus aureus, blast fungus, Phytophthora tobaccoii, and Escherichia coli. It also possesses nitrogen-fixing capabilities, significantly increasing the number and weight of root nodules in soybean seedlings. Furthermore, this strain exhibits high pesticide tolerance, with a minimum inhibitory concentration of 12 mM, and can produce IAA, proteases, and siderophores, possessing phosphate-solubilizing and cellulose-degrading abilities. The S16-7 strain provided by this invention integrates disease prevention, growth promotion, and environmental tolerance, showing broad application prospects in the preparation of microbial agents, biopesticides, and plant growth regulators.

Description

Technical Field

[0001] This invention relates to the field of microbiology and biological control technology, specifically to a strain of Burkholderia cepacia S16-7 and its applications. Background Technology

[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.

[0003] With the continuous growth of the global population, the demand for food is also increasing. However, environmental pollution caused by urbanization and industrialization leads to a decline in soil fertility, hindering crop growth and development, and severely impacting crop yield and quality. To address these challenges, chemical fertilizers and chemical amendments are widely used to improve soil fertility and crop yield. However, excessive and irrational use of chemical fertilizers can cause various environmental problems, leading to biodiversity loss and threatening the long-term sustainability of agricultural systems. Therefore, promoting new types of fertilizers to replace chemical fertilizers is a key measure to improve the soil environment and increase soil fertility. Among these, microbial fertilizers contain a large number of beneficial microorganisms that can provide plants with the nutrients they need while also improving soil structure and increasing soil fertility. Plant growth promoting bacteria (PGPB) are an important component of microbial fertilizers, and their isolation and application have received widespread attention from the academic community. PGPB are a class of microorganisms that naturally exist in the soil, plant rhizosphere, and other environments. They can form symbiotic or associated relationships with plants and promote plant growth and development through various mechanisms.

[0004] In agricultural production, the rational use of pesticides is one of the important means to address the impact of pathogenic fungi and bacteria and improve crop yield and quality. Soil microorganisms play a crucial role in crop production; however, pesticide use can negatively impact the soil microbial community, damaging beneficial fungi and bacteria and reducing their effectiveness in promoting crop production. Currently, a significant portion of plant growth promoters (PGPBs) are damaged by pesticides. Therefore, the development of pesticide-resistant plant growth promoters is becoming increasingly necessary and urgent, and research on pesticide-resistant plant growth promoters is receiving increasing attention.

[0005] Microbial strains are fundamental to the production and application of microbial fertilizers, and their performance directly affects fertilizer efficacy and agricultural ecological benefits. Screening for pesticide-resistant plant growth promoters (PGPBs) provides high-quality strain resources for developing novel microbial fertilizers. These strains not only survive in soil under pesticide application conditions but also promote plant growth through multiple mechanisms. Therefore, there is an urgent need to develop microbial strains with broad-spectrum antibacterial capabilities, multiple growth-promoting functions, and high pesticide tolerance to meet the demands of modern agriculture's green and sustainable development. Summary of the Invention

[0006] The purpose of this invention is to address the problems of narrow antibacterial spectrum, single growth-promoting function, and poor pesticide tolerance of current microbial fertilizer strains. This invention provides a strain of Burkholderia cepacia S16-7 and its application. This strain not only has the effect of significantly improving plant growth and yield, but also has pesticide tolerance, thus enabling it to continuously exert its growth-promoting function under pesticide application conditions.

[0007] The technical solution of the present invention is as follows: This invention provides a strain of Burkholderia cepacia S16-7, which was deposited on August 21, 2025, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing, with accession number CGMCC NO. 35697.

[0008] The strain has the following biological characteristics: (1) It can simultaneously inhibit Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), rice blast fungus (fungus) and Phytophthora indica (oomycete); (2) It has nitrogen-fixing ability; (3) It is resistant to pesticides, with a minimum inhibitory concentration of 12 mM; (4) It can produce indoleacetic acid, protease and iron carrier, and has phosphorus-solubilizing ability and cellulose degradation ability.

[0009] According to a preferred embodiment, the 16S rRNA sequence of the strain S16-7 is shown in SEQ ID NO.3.

[0010] Another aspect of the present invention provides a microbial inoculant comprising live cells, suspensions or fermentation broths of Burkholderia S16-7 as described above, and an agriculturally acceptable carrier or adjuvant.

[0011] Preferably, the agriculturally acceptable carrier is, for example, peat, vermiculite, bentonite, or a combination thereof.

[0012] Preferably, the microbial agent is in the form of a wettable powder, a water-dispersible granule, a suspension concentrate, or a pellet.

[0013] Preferably, when the microbial agent is in the form of live bacteria or bacterial suspension, the bacterial concentration is 1×10⁻⁶. 7 cfu·mL -1 Up to 1×10 9 cfu·mL -1 .

[0014] Another aspect of the present invention provides the application of a strain of Burkholderia cepacia S16-7 or a microbial agent as described above in the prevention and control of plant diseases.

[0015] Preferably, the plant disease can be caused directly or indirectly by a plant pathogen. Preferably, the plant pathogen is a bacterium, fungus, or oomycete. For example, the plant pathogen can be Staphylococcus aureus (…). Staphylococcus aureus Rosenbach, rice blast fungus ( Magnaporthe oryzae ), Tobacco Phytophthora ( Phytophthora nicotianae ) and Escherichia coli ( Escherichia coli At least one of the following.

[0016] Preferably, the plant disease can be rice blast, tobacco blight, bacterial leaf spot, or soft rot.

[0017] Preferably, the application method is seed dressing, root irrigation, or foliar spraying, with an application concentration of 1×10⁻⁶. 7 cfu·mL -1 Up to 1×10 9 cfu·mL -1 .

[0018] Another aspect of the present invention provides the application of a strain of Burkholderia cepacia S16-7 or a microbial agent as described above in promoting plant growth.

[0019] Preferably, the plant is a legume, specifically soybean, peanut, broad bean, or pea.

[0020] Preferably, the application can be used in conjunction with a broad-spectrum fungicide, and the strain is resistant to the broad-spectrum fungicide.

[0021] Preferably, promoting plant growth involves regulating any one or more of the following: soybean plant height, root length, fresh weight, and dry weight.

[0022] Preferably, the Burkholderia cepacia S16-7 or the microbial agent produces a variety of beneficial metabolites such as proteases, cellulases, and siderophores, which synergistically promote plant growth and development through multiple pathways such as nitrogen fixation, IAA production, phosphorus solubilization, and cellulose degradation.

[0023] Another aspect of the present invention provides the application of Burkholderia cepacia S16-7 as described above in soil improvement.

[0024] Preferably, the application specifically involves applying the strain or its fermentation products to the soil to improve the soil micro-ecological environment through its phosphorus-solubilizing, IAA-producing, protease-producing, iron-carrier-producing, and cellulose-degrading abilities.

[0025] Compared with existing technologies, the advantages of this invention are: 1. A strain of Burkholderia cepacia S16-7 was isolated and screened for pesticide tolerance to PGPB using soybean root nodules under pesticide application conditions as the isolation material. The strain S16-7 was selected as a Burkholderia strain. Burkholderia cepacia S16-7 is a new species of strain with various beneficial effects; 2. Broad-spectrum antibacterial ability: S16-7 strain can simultaneously inhibit four different types of pathogens: Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), rice blast fungus (fungus), and Phytophthora indicum (oomycete). This overcomes the shortcomings of existing biological control strains with narrow antibacterial spectrum. A single strain can replace multiple biocontrol agents, reducing control costs. 3. Multifunctional growth-promoting effect: The strain of this invention not only has nitrogen-fixing ability, which can significantly increase the number of root nodules in soybean seedlings (increase by 82.32%), root nodule weight (increase by 70.00%), and chlorophyll content (26.19%), but also produces indoleacetic acid to promote plant growth, and produces a variety of beneficial metabolites such as protease, cellulase and siderophores. Through nitrogen fixation, production of plant nutrient factors, phosphorus solubilization and other multiple pathways, it synergistically promotes plant growth and development, which solves the problem of the single growth-promoting function of existing biological control strains. 4. High pesticide tolerance: The strain of this invention has a minimum inhibitory concentration of 12 mM to broad-spectrum fungicides, exhibiting high pesticide tolerance. It can grow and function normally in the presence of pesticides and can be used in conjunction with chemical pesticides to achieve an organic combination of biological and chemical control, thus solving the technical problem of poor pesticide tolerance of existing biological control strains. 5. Broad application prospects: Burkholderia S16-7 of the present invention can be used to prepare biocontrol agents, plant growth promoters and microbial fertilizers. It has broad application prospects in agricultural biological control, plant growth promotion and green agricultural production, and is of great significance to promoting sustainable agricultural development. Attached Figure Description

[0026] Figure 1A phylogenetic tree constructed based on the 16S rRNA sequence of strain S16-7; Figure 2 The growth curve of strain S16-7 in this invention is shown. Figure 3 This is a positive ion chromatogram of the metabolites of strain S16-7 in this invention; Figure 4 This is a flow chromatogram of negative ions from the metabolites of strain S16-7 in this invention; Figure 5 This is a heatmap showing the relative content of metabolites of strain S16-7 in this invention. Figure 6 The results show the effect of strain S16-7 on crop seedling quality in a pot experiment with pesticide application; CK represents normal soil without S16-7 inoculant; S16-7 represents normal soil with S16-7 inoculant. Detailed Implementation

[0027] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.

[0029] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0030] Example 1: Isolation and Identification of Strains In 2024, soybean plants were collected from Longhe Village, Huili City, Liangshan Prefecture, Sichuan Province (26°64'61''N, 102°36'93''E). Soybean root nodule samples were stored at 4 ℃ for the isolation of pesticide-resistant soybean root nodule endophytic bacteria.

[0031] 2. Isolation of pesticide-resistant bacteria from soybean root nodules Using soybean root nodules as the isolation material, 10 large, plump, and pink soybean root nodules were selected and placed in a test tube. They were washed three times with sterile water, then surface-sterilized with 2.5% HgCl2 for 2 minutes, and then rinsed five times with sterile distilled water. 100 μL of sterile distilled water from the last rinse was spread on a YMA plate and incubated at 29 °C for 4 days. If no bacterial growth was observed, the surface was considered sufficiently sterilized.

[0032] The cleaned root nodules were ground using a sterile grinder to obtain a root nodule broth. The broth was streaked onto YMA medium and incubated at 28 °C for 4 days. Different colonies were isolated based on colony size, morphology, and color, and the process was repeated to purify the bacteria. A total of 102 bacterial strains with different phenotypes and colony sizes were obtained from the isolated material, and their names are shown in Table 1 below.

[0033] (1) Pesticide tolerance test The 102 isolated strains were inoculated onto LB agar plates supplemented with different concentrations of pyraclostrobin and cultured at 27 °C for 48 h. Colony growth was recorded at each concentration, and the lowest concentration that completely inhibited colony growth was defined as the minimum inhibitory concentration (MIC). The pesticide tolerance of the strains is shown in Table 1.

[0034] Table 1. Pesticide tolerance of bacterial strains

[0035] Pesticide tolerance was determined for 102 bacterial strains in a gradient range of 0 to 14 mM. The results showed that 56 strains exhibited tolerance to pyraclostrobin, of which 11 strains had MIC values ​​between 8 and 12 mM, with S16-7 having a MIC value of 12 mM.

[0036] (2) Protease activity Fifty-six pesticide-resistant strains were further isolated and inoculated into skim milk agar medium to determine their protease activity. After incubation at 30 °C for 2 days, the protease activity was assessed by observing the clear area surrounding the colonies. The Folin-Ciocalteu method was used for further quantification of protease activity. The strains were inoculated at a 1% inoculum in LB medium, and the fermentation broth was cultured at 30 °C and 180 rpm for 24 hours. Protease activity was then quantified in μmol·mg⁻¹. -1 ·h -1 The enzyme activity of different strains is shown in Table 2.

[0037] Table 2 Protease activity

[0038] The protease activity of 56 bacterial strains was determined (see Table 2). All isolated strains exhibited protease activity, with some exceeding 1.5 μmol·mg. -1 ·h -1 Of the 37 strains, accounting for 66% of the total isolated strains, 37 strains exhibited protease activity higher than 1.8 μmol·mg. -1 ·h -1 Sixteen strains were identified, accounting for 28% of the total isolated strains. Among them, strain S16-7 had a protease activity of 2.06 μmol·mg. -1 ·h -1 .

[0039] (3) IAA production capacity determination Fifty-six strains were inoculated into LB liquid medium supplemented with tryptophan and cultured at 28 °C for 2 days. The supernatant was collected by centrifugation, and the IAA yield was determined by Salkowski colorimetric method based on the IAA standard curve. The IAA yield of different strains is shown in Table 3.

[0040] Table 3. Measurement of IAA Production Capacity

[0041] The results of the IAA production capacity determination of 56 strains are shown in Table 3. All isolated strains have the ability to produce IAA. Among them, 6 strains have an IAA production capacity of more than 25.00 mg / L, accounting for 10.71% of the total number of isolated strains. The IAA production capacity of S16-7 is 21.57 mg / L.

[0042] (4) Inorganic phosphorus degradation capacity The 56 isolated strains were inoculated into PVK solid medium and cultured at 28 ℃ for 2 days. The ratio of the diameter of the transparent zone to the diameter of the colony was measured for initial screening. The phosphorus solubility (mg / L) of the fermentation broth of the strains after culturing at 30 ℃ and 180 rpm for 24 h was further quantitatively determined by the molybdenum antimony colorimetric method. The phosphorus solubility of different strains is shown in Table 4.

[0043] Table 4. Degradation capacity of inorganic phosphorus

[0044] Note: nd: not detected, meaning the activity was not detected.

[0045] As shown in Table 4, 47 out of the 56 strains had the ability to degrade inorganic phosphorus, accounting for 84% of the total isolated strains. Among them, the phosphorus solubility of S16-7 was 1.67 mg / L.

[0046] (5) Cellulase production capacity The 56 isolated strains were inoculated onto CMC solid medium and cultured at 28 ℃ for 2 days. After Congo red staining, the diameter of the clear zone was measured for preliminary screening. Further quantitative determination of cellulose solubility was performed using the DNS colorimetric method. The strains were inoculated at a 1% inoculum in cellulose liquid fermentation medium (CMC liquid medium), and the fermentation broth of the strains cultured at 28 ℃ and 180 rpm for 3 days was quantitatively measured to calculate the cellulose solubility (mg / L). The cellulose solubility of different strains is shown in Table 5.

[0047] Table 5 Cellulase Activity

[0048] As shown in Table 5, 22 out of the 56 strains had a cellulose solubility of more than 5.00 mg / L, accounting for 39.3% of the total isolated strains. Among them, strain S16-7 had a cellulose solubility of 5.13 mg / L.

[0049] (6) Determination of iron production capacity The 56 isolated strains were inoculated into CAS liquid medium and cultured at 28 ℃ for 2 days. The siderophore activity units (%) were quantitatively determined by CAS colorimetric method. The results are shown in Table 6.

[0050] Table 6. Iron Production Capacity

[0051] Siderophore production capacity was determined for 56 strains (see Table 6). It can be seen that all isolated strains have siderophore production capacity. Among them, 9 strains have a siderophore production capacity of more than 50%, accounting for 16% of the total isolated strains. Among them, the siderophore production capacity of strain S16-7 is 56.45%.

[0052] (7) Nitrogen fixation capacity determination The 56 isolated strains were inoculated into Ashube solid medium and cultured at 28°C for 2 days. The growth of the strains was observed, and the specific results are shown in Table 7.

[0053] Table 7. Nitrogen fixation capacity measurement results

[0054] The nitrogen fixation capacity of the 56 isolated strains is shown in Table 7. The results show that all 56 isolated strains have nitrogen fixation capacity.

[0055] (8) Antibacterial activity assay The antagonistic effects of the 56 isolated strains against five indicator bacteria—Escherichia coli, Staphylococcus aureus Rosenbach, Magnaphalthe oryzae, Phytophthora nicotianae, and Rhizoctonia solani—were determined using the plate confrontation method. The diameter of the inhibition zone (HD) and the colony diameter (CD) were measured, and strains with inhibitory effects were screened by calculating the HD / CD ratio, as detailed in Table 8.

[0056] Table 8. Results of Antibacterial Ability Measurement

[0057] Note: In the table, indicator strain 1 is *Escherichia coli*; 2 is *Staphylococcus aureus* Rosenbach; 3 is *Magnaporthe oryzae*; 4 is *Phytophthora nicotianae*; and 5 is *Rhizoctonia solani*. ++ indicates an HD / CD value between 2. 3; + indicates that the HD / CD value is between 1 and 2; This indicates that the HD / CD value is less than 1.

[0058] Table 3 shows that 10 strains exhibited antagonistic effects against *Escherichia coli*, 17 against *Staphylococcus aureus*, 23 against *Oryza sativa*, 18 against *Phytophthora indicum*, and 25 against *Rhizoctonia solani*. 24 strains (42.86% of the total isolates) simultaneously inhibited two or more pathogens; 12 strains (21.43% of the total isolates) simultaneously inhibited three or more pathogens; and 2 strains (3.57% of the total isolates) simultaneously inhibited four or more pathogens. Among these, strain S16-7 simultaneously inhibited four pathogens: *Escherichia coli*, *Staphylococcus aureus*, *Oryza sativa*, and *Phytophthora indicum*.

[0059] Based on the combined characteristics and assay results of the strain, strain S16-7 was selected as the target strain for further research.

[0060] 3. Identification of strain S16-7 DNA was extracted from strain S16-7 using a bacterial genome extraction kit and diluted 10-fold as a template for PCR amplification of the bacterial 16S rRNA gene fragment. Primers 1492R (SEQ ID NO.1: 5'-TACGGCTACCTTGTTACGAC-3') / 27F (SEQ ID NO.2: 5'-GAGAGTTTGATCCTGGCTCAG-3') were selected to amplify the 16S rRNA gene fragment isolated from strain S16-7. The sequence obtained by sequencing the amplified 16S rRNA gene fragment is shown in SEQ ID NO.3. The 16S rRNA gene sequence has been uploaded to NCBI, and the gene accession number is PX622701.1.

[0061] 16S rRNA (SEQ ID NO.3):

[0062] The sequence of strain S16-7 was uploaded to NCBI for BLAST alignment. The top ten sequences with the highest similarity to this strain were selected and used to construct a phylogenetic tree with this strain. The results are shown below. Figure 1 As shown. Based on the above characteristics, strain S16-7 was identified as Burkholderia viminalis (…). Burkholderia cepacia This strain was deposited on August 21, 2025, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing, with accession number CGMCC NO. 35697. Colonies of strain S16-7 on agar plates are medium-sized, yellow, opaque, moist, and raised.

[0063] Example 2: Growth curves under pesticide stress The isolated strain S16-7 was inoculated into LB liquid medium containing neither pyraclostrobin nor 12 mM pyraclostrobin, and cultured in a dark shaker at 28 ℃ and 180 r / min. Samples were taken every 6 h, and the culture was zeroed using uninoculated LB liquid medium. The OD600 value of the bacterial culture was measured at 600 nm. A growth curve of S16-7 was plotted with the OD600 value at each time point as the ordinate and the culture time as the abscissa. (See figure) Figure 2 .

[0064] Depend on Figure 2 It can be seen that S16-7 can grow in LB medium containing 12mM pyraclostrobin, and its growth trend is consistent with that in medium without pyraclostrobin, indicating that the strain has pesticide resistance.

[0065] Example 3: Metabolite Study of S16-7 1. Separation and purification of secondary metabolites The isolated strain S16-7 was inoculated into LB liquid medium and cultured in a constant temperature shaker at 28℃ and 180 r / min in the dark for 72 h. After culturing, the culture was centrifuged at 28℃ and 8000 r / min for 5 min, and the fermentation broth was retained.

[0066] The fermentation broth was added to 10 times its volume of 90% methanol pre-cooled to 4 °C (i.e., 1 mL of 90% methanol for every 100 mg of sample), homogenized, and dried. The supernatant was then treated with an ethanol-water solution and injected for analysis. Chromatographic analysis was performed using an Agilent 1290 Infinity LC system with automated injection at 4 °C throughout. Mass spectrometry identification was performed using both positive and negative ion modes. Raw data were converted to mz ML format using Proteo Wizard, then processed using XCMS and SIMCA-P 14.1 software. After Pareto-scaling preprocessing, unidimensional and multidimensional statistical analyses were performed.

[0067] 2. Results of metabolites Using thresholds VIP>1 and P<0.05 as criteria, the identified metabolites were screened, resulting in 898 differential metabolites (the positive and negative ion currents of the metabolites are shown in [reference]). Figure 3 , Figure 4 The top 10 metabolites are listed below. Figure 5 The alkaloids are L-Isoleucine, phenylethanolamine, ethylphosphonic acid, 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, glycylglycyl-L-valine, adenosine, zinecard, gly-Ile, L-methionine, and leucylproline.

[0068] Example 4: Potted plant verification of PGPB performance Based on the experimental results above, the pesticide-resistant and growth-promoting strain S16-7 was activated and inoculated into LB liquid medium. It was cultured in a constant-temperature shaker at 28 ℃ and 180 r / min for 72 h. After culturing, it was used as a seed culture and inoculated into LB liquid medium at a 1:1 volume ratio. Then, it was cultured with shaking in a constant-temperature shaker at 28 ℃ and 180 r / min for 108 h to achieve a yield of 1×10⁻⁶ cells / mL. 8 cfu·mL -1 The bacterial suspension was taken out and set aside for later use.

[0069] The experimental soil was collected from farmland surrounding Sichuan Agricultural University. The top 0-20 cm layer had a pH of 7.51, a moisture content of 16.12%, and an organic carbon content of 22.84 g·kg⁻¹. -1Total nitrogen 82 g·kg -1 Alkaline nitrogen content: 42.49 mg·kg -1 Available phosphorus 72.52 mg·kg -1 Available potassium 38.33 mg·kg -1 Soybeans of uniform growth were planted in flowerpots, with 2 kg of soil sample in each pot. The S16-7 inoculant was inoculated into the soybean roots by watering. The inoculant suspension (1×10⁻⁶) was added weekly. 8 cfu·mL -1 ), 2.5 mL each time, with sterile water as a control (CK). Plant growth was measured after 30 days, and the results are shown in Table 9. Figure 6 .

[0070] Table 9. Effects of strain S16-7 on soybean seedling growth

[0071] Based on pesticide tolerance and PGP tolerance, S16-7 was selected for pot experiments (location: Light-Cultivated Room, College of Resources, Sichuan Agricultural University). The results are shown in Table 9 and... Figure 6 As shown in the figure. Compared with the control (CK) on the right, the S16-7 treatment on the left significantly promoted the growth of soybean plants. Compared with the control (CK), soybean seedlings treated with S16-7 showed significant increases in the number of root nodules, root nodule weight, and chlorophyll content, with increases of 82.32%, 70.00%, and 26.19%, respectively.

[0072] In summary, this invention comprehensively evaluated the pesticide tolerance, protease activity, IAA production capacity, inorganic phosphorus degradation capacity, cellulase activity, siderophore production capacity, nitrogen fixation capacity, and antibacterial ability of soybean rhizosphere growth-promoting bacteria, and screened out strain S16-7 with excellent comprehensive performance. Strain S16-7 can promote plant growth, inhibit plant pathogenic fungi, and increase the plant height, root length, fresh weight, and dry weight of soybean seedlings under pesticide stress.

[0073] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A strain of Burkholderia cepacia S16-7, characterized in that, This strain was deposited on August 21, 2025, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, Beijing, with accession number CGMCC NO. 35697.

2. A microbial inoculant, characterized in that, The product comprises live cells, suspensions or fermentation broths of Burkholderia cepacia S16-7 as described in claim 1, and agriculturally acceptable carriers or adjuvants.

3. The microbial inoculant according to claim 2, characterized in that, The microbial agent is formulated as a wettable powder, water-dispersible granule, suspension concentrate, or granule.

4. The application of a Burkholderia cepacia S16-7 strain as described in claim 1 or a microbial agent as described in any one of claims 2-3 in the prevention and control of plant diseases.

5. The application according to claim 4, characterized in that, The plant disease can be caused directly or indirectly by plant pathogens, which are bacteria, fungi, or oomycetes.

6. The application according to claim 5, characterized in that, The plant diseases mentioned can be rice blast, tobacco blight, bacterial leaf spot, or soft rot.

7. The application of a Burkholderia cepacia strain S16-7 as described in claim 1 or a microbial agent as described in any one of claims 2-3 in promoting plant growth.

8. The application according to claim 7, characterized in that, The plant in question is a legume.

9. The application according to claim 7, characterized in that, The promotion of plant growth refers to regulating any one or more of the following: soybean plant height, root length, fresh weight, and dry weight.

10. The application of Burkholderia cepacia S16-7 as described in claim 1 in soil improvement.

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