A type of rhizosphere probiotic BWJ5 and its application

Abstract

This application relates to the field of microbial technology, specifically disclosing a rhizosphere probiotic BWJ5 and its applications. The rhizosphere probiotic BWJ5 is *Pseudomonas rhizophila* BWJ5, deposited on May 19, 2025, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 34590, and classified as *Pseudomonas rhizophila*. Strain BWJ5 exhibits broad-spectrum antibacterial activity against 10 plant pathogens, including *Pseudomonas aeruginosa*, with inhibition rates ranging from 9.16% to 74.83%. It demonstrates outstanding phosphorus solubilization, iron chelation, and nitrogen fixation abilities, with D / d values ​​of 1.70, 4.41, and 2.84, respectively. It exhibits strong stress resistance, growing in media containing 15% NaCl or 10% PEG, and shows significant growth-promoting effects on melons and peppers, demonstrating promising application prospects.

Description

Technical Field

[0001] This application relates to the field of microbial technology, and more specifically, to a rhizosphere probiotic BWJ5 and its application. Background Technology

[0002] Soil salinization is a major threat to global agricultural sustainable development and ecological security, essentially a functional degradation caused by excessive accumulation of soil salt. This process is driven by natural factors (such as salt accumulation on the surface in arid regions) and can be exacerbated by human activities (such as improper irrigation). The high osmotic pressure of saline soils disrupts plant water balance, hinders nutrient absorption, and triggers a chain reaction of vegetation degradation and reduced biodiversity, ultimately leading to decreased arable land productivity, weakened grassland ecological functions, and reduced tree survival rates, severely restricting regional economic development. Some arid and semi-arid regions are severely affected by salinization, with evaporation far exceeding precipitation and scarce groundwater resources, resulting in large areas of saline-alkali land. Under this complex stress environment, cultivating crop varieties with both salt tolerance and drought resistance has become crucial for sustainable agricultural development.

[0003] Plant rhizosphere growth-promoting bacteria (PGPRs) have attracted much attention due to their growth-promoting and stress-resistance functions. Their mechanisms of action include secreting growth-regulating substances (such as IAA and ACC deaminases), activating soil nutrients, and inhibiting pathogenic microorganisms. However, most reported PGPR strains have limited growth-promoting effects under combined saline-alkali and drought stress, exhibiting insufficient salt tolerance and unstable drought resistance, leading to poor field application results. Furthermore, existing strains are mostly derived from the rhizosphere of common crops, exhibiting poor adaptability to extreme environments and difficulty in efficiently colonizing and functioning in saline-alkali soils. Therefore, screening PGPR strains from the rhizosphere of stress-tolerant plants that possess high growth-promoting activity, multiple stress resistance, and pathogen inhibition capabilities has become an important direction for overcoming the bottlenecks in saline-alkali soil biological improvement technology.

[0004] *Zygophyllum xanthoxylum* (Bunge) Maxim., a xerophytic shrub belonging to the genus *Zygophyllum* in the family Zygophyllaceae, is widely distributed in desert and semi-desert regions of western Inner Mongolia, Gansu, Ningxia, Xinjiang, and Qinghai in China, and is also found in Mongolia. This species exhibits extremely strong drought and salt tolerance, commonly found in barren habitats such as gravelly river terraces, low hills, scree slopes, and lakeside sandy areas, making it an important dominant species in arid ecosystems. The rhizosphere of halophytes harbors rich and diverse salt-tolerant and growth-promoting microbial resources. Recent studies have shown that these microorganisms not only enhance the stress resistance of host plants but also generally inhibit soil-borne pathogens. Utilizing these microorganisms through artificial screening, compounding, and enrichment can significantly improve their ecological benefits in saline-alkali land improvement, providing a new biological solution for sustainable agricultural development. Based on the above, this application provides a rhizosphere probiotic, BWJ5, from *Zygophyllum xanthoxylum* and its applications. Summary of the Invention

[0005] To address the common problems of poor growth promotion effect, weak salt tolerance, insufficient drought resistance, and limited ability to inhibit plant pathogens in the practical application of existing rhizosphere probiotics, this application provides a Bawang rhizosphere probiotic BWJ5 and its application.

[0006] In the first aspect, this application provides a BaWang rhizosphere probiotic BWJ5, which adopts the following technical solution:

[0007] A rhizosphere probiotic, BWJ5, is a type of Pseudomonas rhizophila. It was deposited on May 19, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, with accession number CGMCC No. 34590 and classified as Pseudomonas rhizophila.

[0008] Secondly, this application provides a microbial biocontrol agent, which adopts the following technical solution:

[0009] A microbial biocontrol agent, wherein the microbial biocontrol agent contains the above-mentioned Bawang rhizosphere probiotic BWJ5.

[0010] Preferably, in the microbial biocontrol agent, the Bawang rhizosphere probiotic BWJ5 exists in the form of cultured live bacteria, fermentation broth, or bacterial suspension.

[0011] Preferably, the formulation of the microbial biocontrol agent is a wettable powder, a water dispersible agent, an aqueous suspension, or a dispersible oil suspension.

[0012] Thirdly, this application provides an application of BaWang rhizosphere probiotic BWJ5 or a microbial biocontrol agent, employing the following technical solution:

[0013] The application of the Bawang rhizosphere probiotic BWJ5 described in the first aspect or the microbial biocontrol agent described in the second aspect in inhibiting plant pathogens, promoting plant growth, and enhancing stress resistance.

[0014] Preferably, the plant pathogens include *Cytospora chrysosperma* QH2, *Fusarium sambucinum* GQGF3, *Acrostalagmus luteoalbus* CMGF-A, *Dactylonectria macrodidyma* CMGF-D, *Cytospora chrysosperma* YSFL4-2, *Colletotrichum scovillei* LJ1, *Botryosphaeria berengeriana* LLW, *Botrytis cinerea* LHM, *Monilinia fructigena* LHF, and *Rhizoctonia solani* MLS.

[0015] Preferably, the application method includes soaking the plants to be treated with the microbial biocontrol agent, or irrigating the roots or spraying the plants after transplanting the seedlings.

[0016] Preferably, the plant is an apple, goji berry, strawberry, tobacco, poplar, chili pepper, pear, potato, etc.

[0017] In summary, this application has the following beneficial effects:

[0018] (1) Outstanding multifunctional growth-promoting characteristics: Strain BWJ5 possesses highly efficient phosphorus solubilization (D / d value 1.7), iron complexation (D / d value 4.41), and nitrogen fixation (D / d value 2.84) capabilities, which can effectively activate insoluble nutrients in the soil and promote the absorption of nutrients by crops. After application, it can significantly improve plant growth indicators such as plant height, stem diameter, number of leaves, fresh weight, and dry weight, and its overall growth-promoting effect is superior to that of conventional strains.

[0019] (2) Excellent stress resistance: This strain can tolerate up to 15% NaCl salt stress and 10% PEG simulated drought environment. It can still maintain metabolic activity and play a growth-promoting function under extreme saline-alkali and drought conditions, providing a reliable microbial strategy for crop planting in arid and saline-alkali areas.

[0020] (3) Significant broad-spectrum biocontrol potential: It showed inhibitory activity against 10 common pathogens, including apple rot fungus, potato black spore fungus and strawberry root rot fungus. The inhibition rate against apple rot was as high as 92.4%, and the inhibition rates against potato black spore fungus and strawberry root rot reached 74.83% and 66.64%, respectively. It effectively reduced dependence on chemical pesticides and had both ecological benefits and economic value.

[0021] (4) Diverse formulations and wide applicability: It can be developed into liquid fermentation inoculants, solid inoculants or wettable powders (live count ≥ 1×10⁻⁶). 8 It comes in various forms such as CFU / g and is suitable for different application methods such as seed soaking, root irrigation, and foliar spraying, and can flexibly match the actual needs of various crops and cultivation modes.

[0022] (5) High value of green and sustainable application: By replacing part of the input of chemical fertilizers and pesticides through microbial pathways, it helps to reduce agricultural non-point source pollution and reduce the risk of soil degradation. It is especially suitable for ecologically fragile areas and green agricultural production areas, which is in line with the direction of sustainable development. Attached Figure Description

[0023] Figure 1 The images show the in-plate culture characteristics and scanning electron micrographs of strain BWJ5 in Example 1 of this application, where A is a frontal colony feature of strain BWJ5 on LBA medium; and B is a scanning electron micrograph of strain BWJ5.

[0024] Figure 2 Phylogenetic trees were constructed for the 16S rRNA sequence and whole genome sequence of strain BWJ5 in Example 1 of this application, where A is a phylogenetic tree constructed based on the 16S rRNA gene sequence and B is a phylogenetic tree constructed based on the whole genome sequence.

[0025] Figure 3 This diagram shows the functional characteristics verification of strain BWJ5 in Example 2 of this application. A represents the nitrogen fixation ability test result, B represents the phosphorus solubilization ability test result, C represents the iron complexation ability test result, D represents the growth of the strain under no stress conditions, E represents the growth of the strain under 5% PEG conditions, F represents the growth of the strain under 10% PEG conditions, G represents the growth of the strain under 10% NaCl conditions, H represents the growth of the strain under 12% NaCl conditions, and I represents the growth of the strain under 15% NaCl conditions.

[0026] Figure 4The images show the effects of strain BWJ5 in Example 3 of this application on the growth promotion and salt tolerance of melon and pepper. In the images, A is a comparison of melon plant growth, B is a comparison of pepper plant growth, and C is a comparison of pepper plant growth. From left to right, the images are: CK; BWJ5 treatment group; CK + salt stress group; BWJ5 + salt stress group.

[0027] Figure 5 This is a diagram showing the effect of strain BWJ5 in Example 3 of this application on improving the drought resistance of melon and pepper. From top to bottom, the treatment groups are mild drought, moderate drought, and severe drought. From left to right, the plant growth status is shown after melon treatment without strain, melon treatment with BWJ5, pepper treatment without strain, and pepper treatment with BWJ5.

[0028] Figure 6 This is a diagram showing the antibacterial effect of strain BWJ5 in Example 4 of this application against 10 plant pathogens. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0030] The test materials involved in the embodiments of this application are as follows:

[0031] 1. Test pathogen:

[0032] The following fungi were isolated and identified in our laboratory: *Cytospora chrysosperma* QH2 (apple rot), *Fusarium sambucinum* GQGF3 (goji berry root rot), *Colletotrichum scovillei* LJ1 (pepper anthracnose), *Acrostalagmus luteoalbus* CMGF-A (strawberry root rot), *Dactylonectria macrodidyma* CMGF-D (strawberry root rot), and *Cytospora chrysosperma* YSFL4-2 (poplar rot) (Ma Qiang et al., 2020; Sun Pingping et al., 2023; Zhang Hongling et al., 2024; Jia Wei et al., 2022).

[0033] The fungi causing pear gray mold (Botrytis cinerea LHM), pear ring rot (Botryosphaeriaberengeriana LLW), and pear brown rot (Monilinia fructigena LHF) were isolated and identified by the Institute of Fruit Trees, Chinese Academy of Agricultural Sciences (Sun et al. 2017; Sun Pingping et al., 2018).

[0034] The Rhizoctonia solani MLS fungus for potato black scurvy was provided by Henan Agricultural University.

[0035] 2. Test culture medium:

[0036] (1) Potato glucose medium (PDA medium): 200g potato extract, 20g glucose, 20g agar powder, add deionized water to make up to 1L, pH 7.2.

[0037] (2) LBA medium: 10g tryptone, 5g yeast extract, 10g NaCl, 20g agar powder, add deionized water to make up to 1L.

[0038] (3) LB medium: Same as LBA medium, but without agar powder.

[0039] (4) Ashby nitrogen fixation medium: KH2PO4 0.2g, NaCl 0.2g, MgSO4·7H2O 0.2g, K2SO4·2H2O 0.2g, CaCO3 5g, glucose 5g, mannitol 5g, add deionized water to make up to 1L, pH 7.0.

[0040] (5) Mongkina phosphorus-solubilizing medium: 10g glucose, 0.5g (NH4)2SO4, 0.3g NaCl, 0.3g KCl, 0.3g MgSO4·7H2O, 0.03g FeSO4·7H2O, 0.03g MnSO4·7H2O, 2.5g Ca3(PO4)2, 0.4g yeast extract, add deionized water to a final volume of 1L, pH 7.0.

[0041] (6) CAS solid culture medium: Chromium azurite S 60.5 mg, hexadecyltrimethylammonium bromide 72.9 mg, FeCl3·6H2O 2.645 mg of NaH2PO4·2H2O, 295.25 mg of Na2HPO4·12H2O, 1213.5 mg of NH4Cl, 125 mg of KH2PO4, 37.5 mg of NaCl, and 9 g of agar were added to a final volume of 1 L with deionized water. The mixture was heated to boiling until completely dissolved, and the pH was adjusted to 6.8.

[0042] 3. Testing instruments:

[0043] Incubator (HPX-9162MBE, Shanghai Boxun Industrial Co., Ltd.);

[0044] Clean bench (SW-CJ-1FD);

[0045] Microscope (LEICA ICC50W, Leica Instruments GmbH, Germany);

[0046] Electrophoresis apparatus (BG-Power 600K450W, Beijing Baijing Biotechnology Co., Ltd.);

[0047] PCR instrument (624BR47696, Bio-Rad Laboratories, USA).

[0048] Example 1

[0049] Isolation, screening and identification of Pseudomonas rhizophila BWJ5

[0050] 1. Isolation and screening of strains

[0051] Rhizosphere soil samples were collected from *Euphorbia hirta* in Inner Mongolia. During the collection process, the top 5cm of soil was removed, and 25cm of rhizosphere soil was collected. The samples were wrapped in kraft paper and stored at 4℃.

[0052] Various bacteria in soil were isolated using the dilution-spread plate method. The specific isolation and screening methods are as follows: 10g of dried soil sample was ground and placed in 100mL of sterile water, shaken at 4℃ and 180rpm for 30min, and then serially diluted with sterile water to 100mL. -6 Take 100 μL of the diluent and spread it evenly on LBA medium. Incubate at 28°C for 48 h. Select individual bacterial colonies with different morphologies and colors for streaking purification. Select strain BWJ5 based on its high efficiency in phosphorus solubilization, iron complexation, and nitrogen fixation, as well as its strong resistance. Transfer purified colonies into LB medium and incubate at 28°C with shaking at 180 rpm for 24 h. Mix thoroughly with an equal volume of 50% glycerol (final concentration 25%), and store in preservation tubes at -80°C for later use.

[0053] 2. Identification of the morphological characteristics of the strain

[0054] The strain BWJ5 was plated on LBA medium and incubated statically at 28°C for 48 hours. The morphological characteristics of the colonies were observed, and colonies were picked and examined under a scanning electron microscope. The results are as follows: Figure 1As shown, strain BWJ5 showed uniform staining in LBA medium, with yellow, round, smooth, and moist colonies; scanning electron microscopy revealed that the bacteria were rod-shaped, non-spore-forming, and measured 1.16–2.21 μm in length and 0.45–0.72 μm in width. Figure 1 A shows the frontal colony characteristics of strain BWJ5 on LBA medium. Figure 1 Image B shows the morphological results of strain BWJ5 observed under a scanning electron microscope.

[0055] 3. Molecular biological identification

[0056] The whole genome of strain BWJ5 was sequenced using high-throughput sequencing technology. Genomic DNA was first extracted from the strain, and high-quality genomic sequence data were obtained by combining the advantages of Illumina and PacBio sequencing platforms. After obtaining the complete genome sequence through sequence assembly, genomic evolution analysis was performed using the Genome BLAST Distance Phylogeny approach (GBDP) on the Type Strain Genome Server online platform (https: / / tygs.dsmz.de). Based on the minimum evolutionary distance between genomes, a phylogenetic tree of 16 related strains, including strain BWJ5, was constructed using FASTME 2.1.6.1 software. The analysis included 16S rRNA gene sequences and whole genome sequences, with the numbers in each branch representing the confidence rate of 1000 bootstrap tests. Figure 2 Phylogenetic analysis revealed that strain BWJ5 forms a highly supported monophyletic group with *Pseudomonas rhizophila* S211, with a 99% confidence level. This result was validated in both 16S rRNA gene and whole-genome phylogenetic analyses. Based on this reliable molecular systematics evidence, combined with the strain's morphological characteristics and physiological and biochemical properties, strain BWJ5 was ultimately identified as *Pseudomonas rhizophila*.

[0057] The rhizosphere probiotic BWJ5 obtained in this application was deposited on May 19, 2025, at the China General Microbiological Culture Collection Center (CGMCC), Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 34590, and its classification name is Pseudomonas rhizophila.

[0058] Example 2

[0059] Verification of the growth-promoting and stress-resistance functions of strain BWJ5

[0060] 1. Nitrogen fixation capacity determination

[0061] Experimental method: BWJ5 strain was spread on LBA medium and incubated at 28℃ for 48 h. BWJ5 colonies were picked with sterile cotton swabs and inoculated onto Ashby nitrogen-fixing medium, with 3 replicates. After incubation at 28℃ for 48 h, the colony diameter (d) and the diameter of the surrounding transparent zone (D) were measured, and the D / d ratio was calculated.

[0062] Experimental results: BWJ5 formed a clear transparent zone on Ashby nitrogen-fixing medium (e.g., Figure 3 A) The colony diameter was measured to be d=5.35mm, the transparent zone diameter was D=15.19mm, and the D / d ratio was 2.84, indicating that strain BWJ5 has a significant nitrogen-fixing ability.

[0063] 2. Determination of phosphorus solubility

[0064] Experimental method: The strain BWJ5 was spread on LBA medium and incubated at 28℃ for 48 h. BWJ5 colonies were picked with sterile cotton swabs and inoculated onto Monkina phosphate-solubilizing medium, with 3 replicates. After incubation at 28℃ for 48 h, the colony diameter (d) and the diameter of the surrounding transparent zone (D) were measured, and the D / d ratio was calculated.

[0065] Experimental results: BWJ5 formed a distinct clear zone on Monkina phosphate-solubilizing medium (e.g., Figure 3 B); The colony diameter was measured to be d=7.52mm, the transparent zone diameter was D=12.8mm, and the D / d ratio was 1.7, indicating that strain BWJ5 has significant phosphate solubilization ability.

[0066] 3. Determination of complexing iron capacity

[0067] Experimental method: The strain BWJ5 was spread on LBA medium and incubated at 28℃ for 48 h. BWJ5 colonies were picked with sterile cotton swabs and inoculated onto CAS solid medium, with 3 replicates. After incubation at 28℃ for 48 h, the formation of orange halo was observed and the colony diameter (d) and the diameter of the surrounding transparent zone (D) were measured. The D / d ratio was calculated.

[0068] Experimental results: BWJ5 colonies showed a distinct orange halo around them (e.g., Figure 3 C); The colony diameter was measured to be d=2.15mm, the transparent zone diameter was D=9.49mm, and the D / d ratio was 4.41, indicating that strain BWJ5 has a significant iron complexing ability.

[0069] 4. Drought resistance performance test

[0070] Experimental methods: BWJ5 strain was inoculated into LB medium and cultured at 28℃ and 180 rpm for 24 h to obtain BWJ5 bacterial suspension; LBA medium containing different concentrations of PEG-6000 (0%, 5%, 10%) was prepared, with LBA medium containing 0% PEG-6000 serving as the control (CK); 5 μL of BWJ5 bacterial suspension was taken (OD adjusted with sterile water). 600 =1.0) was spot-inoculated onto LBA medium, with 3 replicates; after static incubation at 28℃ for 48h, the survival status of the colonies was observed.

[0071] Experimental results: BWJ5 can still grow under 10% PEG conditions (e.g., Figure 3 F), indicating that BWJ5 has strong drought resistance.

[0072] 5. Salt tolerance test

[0073] Experimental methods: BWJ5 strain was inoculated into LB medium and cultured at 28℃ and 180 rpm for 24 h to obtain BWJ5 bacterial suspension; LBA medium containing different concentrations of NaCl (10%, 12%, 15%) was prepared; 5 μL of BWJ5 bacterial suspension was taken (OD adjusted with sterile water) 600 =1.0) was spot-inoculated onto LBA medium, with 3 replicates; after static incubation at 28℃ for 48h, the survival status of the colonies was observed.

[0074] Experimental results: BWJ5 can still grow under 15% NaCl conditions (e.g., Figure 3 I) indicates that BWJ5 has strong salt tolerance.

[0075] Example 3

[0076] BWJ5's effects on plant growth promotion and stress resistance

[0077] 1. Experiments on the growth promotion and salt tolerance of BWJ5 in melons and peppers.

[0078] BWJ5 strain was inoculated into LB medium and cultured at 28°C with shaking at 180 rpm for 24 h. The bacterial culture was then adjusted to OD using sterile water. 600 =1.0 (approximately 10) 8 (CFU / mL) for later use.

[0079] Seeds of melon (Jinmi No. 6) and chili pepper (Xiangla No. 5) were sown in seedling pots containing a 1:2 mixture of fine sand and vermiculite. The following treatment groups were established:

[0080] ①BWJ5 treatment group (inoculation + normal growth conditions): After sowing melon / pepper seeds, treatment began when the seeds germinated and broke through the soil; 50mL of BWJ5 bacterial solution was added to each pot, and another 50mL of BWJ5 bacterial solution was added to each pot 14 days after the first addition of bacterial solution, and the moisture content of the leech mixed substrate was maintained at 65% daily;

[0081] Objective: To test the growth-promoting effect of strain BWJ5 on plant growth.

[0082] ②BWJ5 + Salt Stress Group (Inoculation + Salt Stress): After sowing melon / pepper seeds, treatment began when the seeds germinated and broke through the soil; 50mL of BWJ5 bacterial solution was added to each pot. 14 days after the first addition of bacterial solution, another 50mL of BWJ5 bacterial solution was added to each pot. 2 days after the first addition of bacterial solution, 50mL of 1% NaCl solution was added. The moisture content of the leech-infused substrate was maintained at 65% daily.

[0083] Objective: To test the growth-promoting and stress-resistance capabilities of strain BWJ5 in plants under salt stress.

[0084] ③ Blank control group (CK, no inoculation + normal growth conditions): After sowing melon / pepper seeds, treatment began when the seeds germinated and broke through the soil; 50mL LB medium was added to each pot, and another 50mL LB medium was added to each pot 14 days after the first addition of LB medium, and the moisture content of the leech mixed substrate was maintained at 65% daily;

[0085] Objective: To compare the growth-promoting effect of strain BWJ5 as a blank control.

[0086] ④ Blank control + salt stress group (no inoculation + salt stress): After sowing melon / pepper, treatment began when the seeds germinated and broke through the soil; 50mL LB medium was added to each pot, and 50mL LB medium was added to each pot again 14 days after the first addition of LB medium. 2 days after the first addition of LB medium, 50mL of 1% NaCl solution was added, and the moisture content of the leech mixed substrate was maintained at 65% daily;

[0087] Objective: To compare the protective effect of strain BWJ5 under salt stress as a stress control.

[0088] After 30 days of treatment, plants from each group were harvested, and various growth indicators of the plants were measured and recorded, including the following indicators:

[0089] ① Plant height (cm): Measured from the base of the stem to the top;

[0090] ② Stem diameter (mm): Measure the diameter at the cotyledon node using vernier calipers;

[0091] ③Fresh weight (g): After washing the roots, let them air dry naturally and weigh the whole plant;

[0092] ④ Dry weight (g): Blanch at 105℃ for 10 minutes, dry at 60℃ to constant weight, and weigh the whole plant.

[0093] The recorded data were analyzed using SPSS 26.0 using one-way ANOVA, and the significance of differences was determined using Duncan's multiple comparisons (*p<0.05). The results are shown in Table 1 below. Figure 4 .

[0094] Table 1. Effects of different treatments on growth promotion and salt tolerance of melon / pepper

[0095]

[0096] Note: Different letters in the same column indicate significant differences between the control group and the treatment group at the P<0.05 level; the quality of melons was not measured, but the growth chart clearly shows that BWJ5 has a significant growth-promoting effect.

[0097] Combining Table 1 and Figure 4 The results show that strain BWJ5 can significantly improve plant growth and stress resistance. Figure 4 A is a comparison chart of melon plant growth; Figure 4 B is a comparison chart of chili plant growth; Figure 4 C is a comparison of the growth of the entire chili plant; from left to right in the figure are: CK; BWJ5 treatment group; CK + salt stress group; BWJ5 + salt stress group.

[0098] Under no stress conditions, the plant height, stem diameter, and number of leaves of melons treated with strain BWJ5 were significantly higher than those of the control, increasing by 32.25%, 11.92%, and 19.90%, respectively. Under salt stress conditions, the plant height, stem diameter, and number of leaves of melons treated with strain BWJ5 were also significantly higher than those of the stress control, increasing by 10.56%, 13.07%, and 15.47%, respectively, compared to the stress control.

[0099] Under no stress conditions, the plant height, stem diameter, number of leaves, fresh weight, and dry weight of peppers treated with strain BWJ5 were significantly higher than those of the control, increasing by 15.82%, 8.78%, 24.26%, 48.3%, and 36.76%, respectively, compared to the control. Under salt stress conditions, the plant height, stem diameter, number of leaves, fresh weight, and dry weight of peppers treated with strain BWJ5 were also significantly higher than those of the stress control, increasing by 10.62%, 3.53%, 19.41%, 31.43%, and 25.93%, respectively, compared to the stress control.

[0100] Based on the above data, it can be seen that strain BWJ5 can not only promote plant growth under normal conditions, but also maintain high growth indicators in plants under salt stress, indicating that it has dual functions of promoting growth and resisting stress.

[0101] 2. Drought resistance experiment of BWJ5 on melons and peppers

[0102] To evaluate the effect of strain BWJ5 on improving the drought resistance of melon and pepper, this study conducted treatment experiments with different gradients of drought stress on melon and pepper, with the specific groups as follows:

[0103] T0 (mild drought control group): Water daily to maintain soil moisture content at 65% of field capacity. Add 50 mL of LB medium to each pot 14 days after seed germination, and add another 50 mL of LB medium to each pot 14 days later.

[0104] T1 (moderate drought control group): Water every 3 days to maintain soil moisture content at 45% of field capacity. After 14 days of seed germination, add 50 mL of LB medium to each pot. After another 14 days, add another 50 mL of LB medium to each pot.

[0105] T2 (severe drought control group): Water every 5 days to maintain soil moisture content at 25% of field capacity. Add 50 mL of LB medium to each pot 14 days after seed germination, and add another 50 mL of LB medium to each pot 14 days later.

[0106] T3 (Mild Drought Treatment Group): Water daily to maintain soil moisture content at 65% of field capacity. Add 50 mL of BWJ5 bacterial solution (1×10⁻⁶) to each pot 14 days after seed germination. 8 After 14 days, add 50 mL of BWJ5 bacterial solution (1×10⁻⁶ CFU / mL) to each pot. 8 (CFU / mL)

[0107] T4 (Moderate drought treatment group): Water every 3 days to maintain soil moisture content at 45% of field capacity. Add 50 mL of BWJ5 bacterial solution (1×10⁻⁶) to each pot 14 days after seed germination. 8 After 14 days, add 50 mL of BWJ5 bacterial solution (1×10⁻⁶ CFU / mL) to each pot. 8 (CFU / mL)

[0108] T5 (severe drought treatment group): Water every 5 days to maintain soil moisture content at 25% of field capacity. Add 50 mL of BWJ5 bacterial solution (1×10⁻⁶) to each pot 14 days after seed germination. 8 After 14 days, add 50 mL of BWJ5 bacterial solution (1×10⁻⁶ CFU / mL) to each pot. 8 (CFU / mL).

[0109] The recorded data were analyzed using SPSS 26.0 using one-way ANOVA, and the significance of differences was determined using Duncan's multiple comparisons (*p<0.05). The results are shown in Tables 2 and 3. Figure 5 As shown, Figure 5 From top to bottom, the groups are: mild drought treatment group, moderate drought treatment group, and severe drought treatment group. From left to right, the groups are: cantaloupe without bacterial treatment, cantaloupe with BWJ5 treatment, pepper without bacterial treatment, and pepper with BWJ5 treatment, showing the plant growth status.

[0110] Table 2. Effects of strain BWJ5 on drought resistance in melon.

[0111]

[0112] Note: Different letters in the same column indicate significant differences between the control group and the treatment group at the P<0.05 level.

[0113] Table 3. Effects of strain BWJ5 on drought resistance in chili peppers.

[0114]

[0115] Note: Different letters in the same column indicate significant differences between the control group and the treatment group at the P<0.05 level.

[0116] According to the data in Tables 2 and 3, under different degrees of drought stress, the plant height, number of leaves, fresh weight, and dry weight of the BWJ5 treatment groups (T3, T4, T5) were significantly higher than their corresponding uninoculated control groups (T0, T1, T2). Specifically, under severe drought conditions, the plant height and fresh weight of the melon BWJ5 treatment group increased by 72.85% and 40.17% respectively compared to the control group, while the plant height and fresh weight of the pepper BWJ5 treatment group increased by 9.72% and 31.95% respectively compared to the control group. This indicates that BWJ5 can effectively alleviate the inhibitory effect of drought on plant growth and promote biomass accumulation.

[0117] Regarding stem diameter, most BWJ5 treatment groups showed no significant difference from the control group, but the values ​​remained stable or slightly increased. Notably, the growth-promoting effect of the BWJ5 treatment groups was particularly pronounced as drought severity increased. Especially under mild and moderate drought conditions, the plant height of the melon BWJ5 treatment group increased by 77.90% and 98.85% compared to the control group, respectively, while the fresh weight of the pepper BWJ5 treatment group increased by 18.64% and 38.20% compared to the control group, respectively. This demonstrates that the BWJ5 strain has a strong potential to enhance crop drought resistance.

[0118] Example 4

[0119] Antibacterial spectrum determination of Pseudomonas rhizophila BWJ5

[0120] The antagonistic effect of BWJ5 against 10 important tree and crop pathogens was determined using the in-plate antagonism method: Cytospora chrysosperma QH2 (apple rot), Fusarium sambucinum GQGF3 (goji berry root rot), Botryosphaeria berengeriana LLW (pear ring rot), Botrytis cinerea LHM (pear gray mold), Monilinia fructigena LHF (pear brown rot), Acrostalagmus luteoalbus CMGF-A (strawberry root rot), Dactylonectriamacrodidyma CMGF-D (strawberry root rot), Rhizoctonia solani MLS (potato black spore), Cytospora chrysosperma YSFL4-2 (poplar rot), and Colletotrichum scovillei LJ1 (pepper anthracnose).

[0121] The specific testing procedure is as follows: BWJ5 bacterial cells were picked up with a sterile cotton swab and spotted onto both sides of a PDA plate. Ten pathogenic bacterial colonies (6 mm in diameter) were inoculated in the center of the plate. The treatment with pathogens inoculated only in the center of the plate served as a control. Each treatment was repeated three times, and the plates were incubated statically at 28°C. Once the control colonies had completely covered the plate, the diameter of the lesions was observed and recorded, and the inhibition rate was calculated.

[0122] Inhibition rate (%) = (1 - diameter of antagonistic lesion / diameter of control lesion) × 100.

[0123] The specific results are shown in Table 4 and... Figure 6 As shown.

[0124] Table 4. Results of the efficacy test of strain BWJ5 against 10 pathogens.

[0125]

[0126] Note: An inhibition zone diameter of 0 mm indicates the absence of a transparent zone, but an inhibition band is present at the colony junction. The inhibition rate is calculated by measuring the growth diameter of the pathogen colony.

[0127] The results showed that strain BWJ5 had a significant inhibitory effect on all 10 pathogens mentioned above. Figure 6The inhibition zone ranged from 0.00 to 5.29 mm, and the inhibition rate ranged from 9.61% to 74.83%, indicating that strain BWJ5 has a broad antibacterial spectrum and good antibacterial effect.

[0128] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A Bacopa jambu phytobiome probiotic BWJ5, characterized in that, The said rhizosphere probiotic BWJ5 is Pseudomonas radicales BWJ5, which was preserved in China General Microbiological Culture Collection Center on May 19, 2025, at address: No. 1, Yihuang 3rd, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, with a preservation number of CGMCC No. 34590, and a classification name of Pseudomonas radicales Pseudomonas rhizophila .

2. A microbial biocontrol agent, characterized in that, The microbial biocontrol agent contains the rhizosphere probiotic BWJ5 of claim 1.

3. The microbial biocontrol agent of claim 2, characterized in that, In the microbial biocontrol agent, the rhizosphere probiotic BWJ5 exists in the form of cultured live bacteria.

4. The microbial biocontrol agent of claim 2, characterized in that, The dosage form of the microbial biocontrol agent is wettable powder, water dispersible agent, water suspension or dispersible oil suspension.

5. The use of the microbial biocontrol agent of any one of claims 2-4 for inhibiting plant pathogenic bacteria and plant growth promotion, characterized in that, The plant pathogen is Valsa mali, Phellinus laevigatus, Phellinus robustus, Botryosphaeria berengeriana, Botrytis cinerea, Monilinia fructigena, Rhizoctonia solani, Fusarium sambucinum, Cytospora chrysosperma, Colletotrichum scovillei, and Alternaria alternata; The apple rot pathogen is ( Cytospora chrysosperma )QH2; The pathogen causing root rot in wolfberry is ( Fusarium sambucinum GQGF3; the pathogen causing strawberry root rot is ( Acrostalagmus luteoalbus CMGF-A or ( Dactylonectria macrodidyma CMGF-D; the pathogen causing poplar rot is ( Cytospora chrysosperma YSFL4-2; the anthracnose pathogen of pepper is ( Colletotrichum scovillei LJ1; the pathogen causing pear ring rot is ( Botryosphaeria berengeriana )LLW; the fungus causing pear gray mold is ( Botrytis cinerea LHM; the pathogen causing pear brown rot is ( Monilinia fructigena LHF; the pathogen causing black scurvy in potatoes is ( Rhizoctonia solani MLS.

6. Use of the microbial biocontrol agent of any one of claims 2-4 in enhancing the stress resistance of plants, wherein the stress resistance is salt tolerance or drought tolerance, and the plants are melon or pepper.

7. The use of the microbial biocontrol agent according to claim 5 for inhibiting plant pathogenic bacteria and plant growth promotion, characterized in that, The application mode includes seed soaking, root irrigation after seedling planting, and plant spraying of the microbial biocontrol agent to the plants to be treated.

8. The use of the microbial biocontrol agent according to claim 5 for inhibiting plant pathogenic bacteria and plant growth promotion, characterized in that, The plants are apple, wolfberry, strawberry, poplar, pepper, pear, and potato.

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