Pseudomonas sp. AL4-3-1 with functions of dissolving phosphorus, releasing potassium, producing IAA and siderophore and application thereof

Abstract

The application provides a Pseudomonas AL4-3-1 with the functions of dissolving phosphorus, releasing potassium and producing IAA and iron carrier and an application thereof, and belongs to the technical field of microorganisms. The Pseudomonas (Pseudomonas sp.) AL4-3-1 is preserved in the Guangdong Microbial Culture Collection Center, and the preservation number is GDMCC No: 67689. The strain can efficiently dissolve inorganic phosphorus and release potassium nutrients, and can also secrete the plant growth hormone indole-3-acetic acid (IAA) and iron carrier. The microbial inoculant prepared from the strain is applied to agricultural planting, can effectively improve the bioavailability of phosphorus, potassium and other nutrients in the soil, promotes the growth of crop roots and nutrient absorption, thereby reducing the use of chemical fertilizers, and improving the crop yield and quality. The application has key significance for realizing the green production goal of "reducing fertilizers, increasing yield, improving quality and environmental protection".

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to a strain of Pseudomonas AL4-3-1 with functions of phosphate solubilization, potassium solubilization, IAA production, and siderophore production, and its applications. Background Technology

[0002] In the context of sustainable agricultural development, reducing reliance on chemical fertilizers, improving nutrient utilization efficiency, and ensuring ecological security have become major global challenges. Chemical phosphate and potash fertilizers are crucial in agricultural production, but their utilization rates are generally low. Phosphate fertilizers applied to the soil are easily fixed, forming insoluble phosphates that are difficult for plants to absorb; while approximately 90%-98% of potassium in the soil exists in mineral form and is released slowly. This leads to insufficient utilization by crops, and large amounts of fertilizer residue cause a series of environmental problems such as soil compaction, salinization, and water pollution.

[0003] Developing environmentally friendly microbial fertilizers using plant rhizosphere growth-promoting bacteria (PGPR) is one of the effective strategies for solving the above problems. *Pseudomonas* sp. is an important group of bacteria within PGPR, widely studied due to its strong rhizosphere colonization ability and diverse metabolic functions. Ideal growth-promoting strains should possess multiple synergistic mechanisms to stably exert synergistic effects in the complex rhizosphere environment, mainly including:

[0004] 1. Activate soil nutrients: By secreting organic acids, extracellular enzymes and other substances to dissolve insoluble phosphates (phosphorus solubilization) or decompose silicate minerals to release potassium ions (potassium release), the inherent unusable nutrients in the soil are transformed into available forms that can be used by plants.

[0005] 2. Promote growth: Synthesize plant growth hormones, such as indole-3-acetic acid (IAA), which directly stimulate root development and cell growth, expanding the nutrient absorption area.

[0006] 3. Indirect growth promotion and biological control: In iron-deficient environments, it secretes siderophores to efficiently chelate ferric iron. This provides iron nutrition to plants on the one hand, and on the other hand, it inhibits the growth of various pathogenic microorganisms through competitive iron chelation, thus playing a role in biological control.

[0007] Although numerous Pseudomonas strains with single or partial functions have been reported in existing technologies, technical bottlenecks remain in practical applications, such as limited functionality, low phosphorus solubilization and potassium solubilization efficiency, or low IAA yield. Therefore, screening a multifunctional Pseudomonas strain is of crucial significance for achieving the green production goals of "reducing fertilizer use, increasing yield, improving quality, and protecting the environment." Summary of the Invention

[0008] In view of this, the present invention provides a strain of Pseudomonas AL4-3-1 with functions of phosphate solubilization, potassium solubilization, IAA production, and siderophore production, and its applications, in order to solve the above problems.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] This invention provides a strain of Pseudomonas sp. AL4-3-1, deposited at the Guangdong Provincial Center for Microbial Culture Collection, with accession number GDMCC No:67689, deposit date of January 16, 2026, and deposit location at No. 100 Xianlie Middle Road, Yuexiu District, Guangzhou, Guangdong Academy of Sciences Institute of Microbiology.

[0011] The present invention also provides a method for preparing the bacterial culture of Pseudomonas AL4-3-1, comprising the following steps:

[0012] (1) Pick Pseudomonas AL4-3-1 on LB medium plates and incubate at 24-26 ℃ for 24-36 h to obtain slant culture;

[0013] (2) Pick the slant culture into LB liquid medium and shake it for 24-36 h to obtain seed culture;

[0014] (3) Inoculate the seed culture into the fermentation medium and culture with shaking until the temperature reaches 1~9×10⁻⁶. 9 CFU / mL, yielding Pseudomonas AL4-3-1 bacterial suspension.

[0015] Preferably, the fermentation culture temperature is 24~26℃ and the rotation speed is 180~220rpm.

[0016] Preferably, the inoculation amount of the seed liquid is 2-8%.

[0017] The present invention also provides the use of the aforementioned Pseudomonas AL4-3-1 in any one or more of the following:

[0018] (1) Applications in phosphorus dissolution and / or potassium solubilization;

[0019] (2) Application in iron-producing carriers and / or IAA;

[0020] (3) Application in promoting plant growth;

[0021] (4) Application in the preparation of products with phosphorus-solubilizing and / or potassium-solubilizing effects;

[0022] (5) Application in the preparation of products with the functions of iron carrier and / or IAA;

[0023] (6) Application in the preparation of products that promote plant growth.

[0024] Preferably, the product includes microbial agents, microbial fertilizers, or soil remediation agents.

[0025] The present invention also provides a microbial inoculant comprising a bacterial suspension of the aforementioned Pseudomonas, wherein the effective viable count in the bacterial suspension is 1~9×10⁻⁶. 9 CFU / mL.

[0026] Preferably, the microbial agent is in the form of a liquid or a solid.

[0027] The present invention also provides a method for promoting plant growth by applying the microbial agent to the roots of plants.

[0028] By adopting the above technical solution, the present invention has the following beneficial effects: The *Pseudomonas* sp. AL4-3-1 strain of the present invention is deposited at the Guangdong Provincial Microbial Culture Collection Center, with accession number GDMCC No: 67689, deposit date of January 16, 2026, and location: Institute of Microbiology, Guangdong Academy of Sciences, No. 100 Xianlie Middle Road, Yuexiu District, Guangzhou. This strain can efficiently dissolve inorganic phosphorus and release potassium nutrients, while also secreting the plant growth hormone indole-3-acetic acid (IAA) and siderophores. Applying the microbial agent prepared from this strain to agricultural planting can effectively improve the bioavailability of nutrients such as phosphorus and potassium in the soil, promote crop root growth and nutrient absorption, thereby reducing the use of chemical fertilizers and improving crop yield and quality. This invention is of key significance for achieving the green production goals of "reducing fertilizer use, increasing yield, improving quality, and protecting the environment." Attached Figure Description

[0029] Figure 1 This is a dynamic graph showing the changes in the amount of phosphorus dissolved in strain AL4-3-1 under different phosphorus sources (tricalcium phosphate, dicalcium phosphate, iron phosphate, and aluminum phosphate).

[0030] Figure 2 This is a colony characteristic diagram of strain AL4-3-1.

[0031] Figure 3 Phylogenetic tree of the 16S rDNA sequence of strain AL4-3-1.

[0032] Figure 4 The graph shows the soluble potassium content of strain AL4-3-1 in a culture medium containing potassium feldspar powder.

[0033] Biological Preservation Instructions

[0034] The Pseudomonas sp. AL4-3-1 of this invention, taxonomically named Pseudomonas sp., is deposited at the Guangdong Provincial Center for Microbial Culture Collection (GDMCC No.:67689), on January 16, 2026, at the Institute of Microbiology, Guangdong Academy of Sciences, No. 100 Xianlie Middle Road, Yuexiu District, Guangzhou. Detailed Implementation

[0035] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0036] PKO Inorganic Phosphorus Solid Culture Medium: 10.0 g glucose, 0.5 g ammonium sulfate, 0.5 g yeast extract, 0.3 g sodium chloride, 0.3 g potassium chloride, 0.3 g magnesium sulfate, 0.03 g ferrous sulfate, 0.03 g manganese sulfate, 0.2 g / L lecithin, 1.0 g / L calcium carbonate, 15 g / L agar, 1000 mL deionized water, pH 7.0-7.5.

[0037] PKO Inorganic Phosphorus Liquid Culture Medium: 10.0 g glucose, 0.5 g ammonium sulfate, 0.5 g yeast extract, 0.3 g sodium chloride, 0.3 g potassium chloride, 0.3 g magnesium sulfate, 0.03 g ferrous sulfate, 0.03 g manganese sulfate, 0.2 g lecithin, 1.0 g calcium carbonate, 1000 mL deionized water, pH 7.0-7.5.

[0038] LB liquid medium: peptone 10 g / L, beef extract 3 g / L, sodium chloride 5 g / L, pH 7.2-7.4.

[0039] Solid culture medium for screening potassium-solubilizing bacteria: sucrose 5 g, MgSO4·7H2O 0.5 g, FeCl3 0.005 g, CaCO3 0.1 g, potassium feldspar 2 g, agar 20 g, pH=7.4, deionized water 1000 mL.

[0040] CCM medium: NH4NO3 1 g; MgSO4·7H2O 0.2 g; KH2PO4 0.2 g; mannitol 5.0 g; K2HPO4 0.8 g; CaCl2·2H2O 0.06 g; sucrose 5.0 g; NaMoO4·2H2O 2.5 mg; yeast extract 0.1 g; lactic acid 0.5 mL; NaCl 0.1 g; 1.64% sodium ferric ethylenediaminetetraacetate (Na·Fe·EDTA) 4 mL, distilled water to a final volume of 1000 mL.

[0041] CAS detection solution: Solution A: 0.605 g CAS added to 500 mL distilled water; 0.027 g FeCl3·6H2O added to 100 mL dilute hydrochloric acid; Solution B: 0.729 g HDTMA (hexadecyltrimethylammonium bromide) added to 400 mL distilled water. Then, slowly add Solution A to Solution B to obtain the blue CAS detection solution; this solution should be prepared and used immediately.

[0042] Example 1. Isolation and Identification of Strains

[0043] 1. Isolation and purification of strain AL4-3-1

[0044] The strain of this invention was isolated from the rhizosphere soil of alfalfa planted in paddy fields during winter. The test soil was collected in May 2023. The specific isolation steps are as follows:

[0045] Weigh 10 g of fresh rhizosphere soil and place it in an Erlenmeyer flask containing 90 mL of sterile distilled water. Shake at 150 rpm for 30 min to prepare a soil suspension. Use the standard dilution plating method to prepare 10... -1 10 -2 10 -3 10 -4 10 -5 10 -6 For each dilution, 100 μL of each gradient dilution was inoculated into sterile PKO inorganic phosphorus solid medium and then evenly spread using a spreader. Each dilution was repeated three times, and the cultures were incubated upside down in a 25 ℃ incubator for 3 days. After bacterial growth, the presence or absence of a phosphate-solubilizing clear zone around the bacterial cells was used to identify the phosphate-solubilizing strain. Strains with a clear clear zone were then picked using a sterile inoculation loop and purified multiple times on LB medium until a pure culture was obtained.

[0046] Phosphorus solubilization capacity determination: The bacterial cells that can produce phosphorus-solubilizing transparent zones on PKO inorganic phosphorus solid medium were inoculated into 8 mL of LB liquid medium and cultured in a shaker at 25°C for 24 h to obtain bacterial suspension; 5 mL of bacterial suspension was inoculated into 50 mL of sterilized PKO liquid medium and cultured in a shaker at 25°C and 180 rpm for 7 days. 2 mL of culture solution was then centrifuged at 4°C and 12000 rpm for 10 min, and the supernatant was retained. To verify the phosphorus-solubilizing ability of the screened phosphate-solubilizing bacteria, the retained supernatant was inoculated at a 2% inoculum into liquid culture media containing four poorly soluble phosphorus sources: tricalcium phosphate, dicalcium phosphate, ferric phosphate, and aluminum phosphate. A culture medium inoculated with an equal volume of sterile filtrate served as a blank control. Each treatment was repeated in triplicate. Cultures were continuously incubated at 25°C and 120 rpm for 5 days. Culture media were collected on days 1, 3, and 5, centrifuged at 4°C and 12000 rpm, and the available phosphorus content of the supernatant was determined using the molybdenum antimony colorimetric method. The results are as follows: Figure 1 As shown. The phosphorus solubility of the strain = the available phosphorus content of the inoculated group - the available phosphorus content of the control group.

[0047] Figure 1 The results showed that strain AL4-3-1 could effectively dissolve phosphorus from tricalcium phosphate, dicalcium phosphate, iron phosphate, and aluminum phosphate sources. On day 5, the phosphorus dissolution amounts were 62.66±1.21, 395.51±2.83, 492.23±4.13 mg / L, and 388.23±1.57 mg / L, respectively, with the fastest phosphorus dissolution rate occurring between day 1 and day 3.

[0048] 2. Identification of AL4-3-1 strain

[0049] (1) Microbiological identification

[0050] The obtained strain was inoculated onto LB agar plates and incubated at 25°C for 48 h. Colony characteristics were then observed. Single colonies were 3–5 mm in diameter, round, milky white, with a smooth surface and regular edges, and Gram-negative.

[0051] (2) Molecular biological characteristics

[0052] Single colonies were picked and placed in 1.5 mL centrifuge tubes containing 1 mL of LB medium. The cultures were incubated at 25°C and 200 rpm for 24 h with shaking. Using this bacterial culture as a template, 16S rDNA sequences were amplified using universal primers 27F / 1492R. The primer sequences are as follows:

[0053] 27F: 5'-AGAGTTTGATCCTGGCTCAG-3' (SEQ ID NO. 1);

[0054] 1492R: 5'-GGTTACCTTGTTACGACTT-3' (SEQ ID NO. 2);

[0055] The PCR amplification reaction system consisted of 10 μL 2×Taq enzyme, 1 μL 27F primer, 1 μL 1492R primer, 1 μL bacterial culture, and 12 μL ddH2O. The PCR amplification conditions were: 94℃ pre-denaturation for 3 min; 94℃ denaturation for 30 s, 55℃ annealing for 30 s, 72℃ extension for 90 s, 30 cycles; and 72℃ extension for 10 min. The amplified products were separated and identified by 1% agarose gel electrophoresis, and the PCR products were sent to Beijing Qingke Biotechnology Co., Ltd. for bidirectional sequencing. The 16S rDNA of strain AL4-3-1 is shown in SEQ ID NO. 3.

[0056] 16S rDNA:

[0057] GATGTGAAATCCCCGGGCTCAACCTGGGAACTGCATTCAAAACTGACGAGCTAGAGTATGGTAGAGGGTGGTGGAATTTCCTGTGTAGCGGTGAAATGCGTAGATATAGGAAGGAACACCAGTGGCGAAGGCGACCACCTGGACTGATACTGACACTGAGGTGCGAAAGCGTGGGGAGCAAACAGGATTAGATACCCTGGTAGTCCACGCCGTAAACGATGTCAACTAGCCGTTGGGAGCCTTGAGCTCTTAGTGGCGCAGCTAACGCATTAAGTTGACCGCCTGGGGAGTACGGCCGCAAGGTTAAAACTCAAATGAATTGACGGGGGCCCGCACAAGCGGTGGAGCATGTGGTTTAATTCGAAGCAACGCGAAGAACCTTACCAGGCCTTGACATCCAATGAACTTTCCAGAGATGGATTGGTGCCTTCGGGAACATTGAGACAGGTGCTGCATGGCTGTCGTCAGCTCGTGTCGTGAGATGTTGGGTTAAGTCCCGTAACGAGCGCAACCCTTGTCCTTAGTTACCAGCACGTTATGGTGGGCACTCTAAGGAGACTGCCGGTGACAAACCGGAGGAAGGTGGGGATGACGTCAAGTCATCATGGCCCTTACGGCCTGGGCTACACACGTGCTACAATGGTCGGTACAGAGGGTTGCCAAGCCGCGAGGTGGAGCTAATCCCATAAAACCGATCGTAGTCCGGATCGCAGTCTGCAACTCGACTGCGTGAAGTCGGAATCGCTAGTAATCGCGAATCAGAATGTCGCGGTGAATACGTTCCCGGGCCTTGTACACACCGCCCGTCACACCATGGGAGTGGGTTGCACCAGAAGTAGCTAGTCTAACCTTCGGGAGGACGGT(SEQ ID NO.3).

[0058] BLAST homology alignment of the 16S rDNA sequence showed that this strain had the highest similarity to Pseudomonas sp., reaching 99.93%. A phylogenetic tree was constructed using the Neighbor-Joining (NJ) method with MEGA 12.0 software. The position of strain AL4-3-1 in the constructed library is shown below. Figure 3 As shown, this strain was named *Pseudomonas sp.* AL4-3-1. It was deposited on January 16, 2026, at the Guangdong Provincial Microbial Culture Collection Center, located at No. 100 Xianlie Middle Road, Yuexiu District, Guangzhou, Guangdong Academy of Sciences, Institute of Microbiology. The strain name is *Pseudomonas sp.* AL4-3-1, and the accession number is GDMCC No: 67689.

[0059] Example 2. Determination of potassium-solubilizing ability of Pseudomonas AL4-3-1

[0060] 1. Qualitative testing

[0061] Using an inoculation loop, AL4-3-1 bacterial cells were evenly scraped from the preservation slant and crossed on the potassium-solubilizing bacteria selection medium. The plate was then inverted and placed in an incubator at 25°C. The growth was observed daily. The results showed that the bacterial cells could grow well on the potassium-solubilizing bacteria selection medium and exhibit a cross-shaped surface, indicating that the bacterial cells could utilize the insoluble mineral potassium.

[0062] 2. Quantitative detection

[0063] Pseudomonas AL4-3-1 was inoculated into 8 mL of LB liquid medium and cultured in a shaker at 25℃ for 24 h to obtain a bacterial suspension. 2 mL of the bacterial suspension was inoculated into 50 mL of sterile liquid medium containing potassium feldspar powder (insoluble potassium) and cultured in a shaker at 25℃ and 180 rpm for 5 days. On days 1, 3, and 5, 2 mL of the culture solution was centrifuged at 4℃ and 12000 rpm for 10 min, and the supernatant was collected. The soluble potassium content was determined by atomic absorption flame spectrophotometry, repeated three times. Potassium solubilization amount = soluble potassium content in the inoculated group - soluble potassium content in the control group. The results showed that Pseudomonas AL4-3-1 has potassium-soothing activity. On day 5, the soluble potassium content reached 432.71 ± 19.79 mg / L, and the potassium solubilization rate from day 3 to day 5 was much higher than that from day 1 to day 3. Figure 4 ).

[0064] Example 3. Determination of IAA production capacity of Pseudomonas AL4-3-1

[0065] 1. Qualitative testing

[0066] Pseudomonas AL4-3-1 bacterial suspension was inoculated at a ratio of 3% into 20 mL of LB liquid medium and cultured at 25℃ and 180 rpm for 5 days. After centrifugation at 10000 rpm for 10 min, the precipitate was discarded and the supernatant was collected. 1 mL of the supernatant was placed in a test tube, and an equal volume of Salkowski colorimetric solution was added and thoroughly mixed. Using sterile LB medium as a control, the color changes of each treatment were observed after incubation at room temperature in the dark for 30 min. A red color indicated a positive reaction, meaning the strain could secrete IAA; the deeper the color, the stronger the IAA production capacity. No significant color change indicated a negative reaction, meaning the strain lacked the ability to produce IAA. The results showed that Pseudomonas AL4-3-1 showed a positive reaction, indicating that Pseudomonas AL4-3-1 has the ability to secrete IAA.

[0067] 2. Quantitative detection

[0068] IAA Standard Curve Construction: Accurately weigh 10 mg of IAA, dissolve it in a small amount of anhydrous ethanol, and then add distilled water to a final volume of 100 mL to prepare a 100 μg / mL IAA solution as a stock solution. Then, dilute the stock solution to prepare a series of standard solutions with concentrations of 0 (blank), 0.5 μg / mL, 1.0 μg / mL, 5.0 μg / mL, 10.0 μg / mL, 15.0 μg / mL, 20.0 μg / mL, and 25.0 μg / mL, as working solutions. Take 2 mL of each of the above working solutions and add them sequentially to eight test tubes. Add twice the volume of Salkowski colorimetric solution, incubate at 40℃ in the dark for 30 min, and then measure the absorbance at a wavelength of 530 nm. Measure the absorbance using OD... 530 Plot the IAA standard curve with the x-axis as the horizontal axis and the IAA concentration as the y-axis.

[0069] Pseudomonas AL4-3-1 was inoculated into CCM medium containing 100 mg / L tryptophan, repeated three times. The control was inoculated with inactivated AL4-3-1 culture medium. Both the control and inoculated cultures were cultured at 25 ℃ and 180 rpm on a shaker for 3 days. After the culture was complete, the culture was centrifuged at 4 ℃ and 12000 rpm for 5 min. 5 mL of the supernatant was mixed with an equal volume of Salkowski's reagent, and the mixture was allowed to stand for 30 min in the dark at room temperature before being shaken well. The absorbance of the sample was measured at 530 nm, and the IAA concentration (mg / L) of the test solution was verified on the standard curve. The results showed that Pseudomonas AL4-3-1 had the ability to secrete IAA, reaching 84.64±4.66 mg / L, while the control group had 3.51±0.88 mg / L. The treated group was significantly higher than the control group (P<0.05).

[0070] Example 4. Verification of the siderophore-producing ability of Pseudomonas AL4-3-1

[0071] 1. Qualitative determination

[0072] Prepare CAS solid medium according to the instructions of the siderophore detection kit (Shanghai Zeye Biotechnology Co., Ltd.). Take 2 μL of the AL4-3-1 bacterial fermentation broth prepared in Example 1 and spot it onto a CAS plate. After standing in a 25°C incubator for 48 h, a yellow halo was observed around the colony, indicating that the strain can secrete siderophores.

[0073] Siderophore production index determination: CAS solid medium was prepared according to the instructions of the siderophore detection kit (Shanghai Zeye Biotechnology Co., Ltd.). Activated bacterial cells were inoculated into the CAS solid medium, with 4 replicates. The plates were inverted and incubated in a constant temperature incubator at 25℃ for 7 days. After the incubation, the results were observed. The diameter of the transparent zone (HD) and the diameter of the colony (CD) were measured using the cross-cross method. The siderophore production index was calculated as follows: siderophore production index = diameter of transparent zone (HD) / diameter of colony (CD).

[0074] Siderophore secretion assay: A single colony was picked and inoculated into LB liquid medium. The culture was carried out at 30℃ and 200 rpm for 5 days with shaking. After the culture, the bacterial suspension was centrifuged at 10,000 rpm for 8 min. 5 mL of the supernatant was taken and mixed thoroughly with 5 mL of CAS detection solution. The mixture was allowed to stand at room temperature in the dark for 1 h. The absorbance (As) was measured at 630 nm using a spectrophotometer. Deionized water was used as a control to zero the sample. The absorbance (Ar) of the reaction between 5 mL of sterile LB liquid medium and 5 mL of CAS detection solution was used as a reference value. The siderophore activity units (su) of Pseudomonas AL4-3-1 were measured, where su = [(Ar - As) / Ar] × 100%.

[0075] The results showed that the siderophore production index of Pseudomonas AL4-3-1 was 3.26, and the siderophore activity units (su) reached 95.17%.

[0076] Example 5. Pot Experiment

[0077] 1. Preparation of Pseudomonas AL4-3-1 bacterial suspension

[0078] (1) Pick Pseudomonas AL4-3-1 on LB medium plates and incubate at 25 ℃ for 24 h to obtain slant culture;

[0079] (2) Pick the slant culture into LB liquid medium and culture at 25℃ and 200 rpm for 24 h to obtain seed culture;

[0080] (3) Inoculate the seed culture into the fermentation medium at a rate of 5%, and culture at 25°C with shaking at 200 rpm until the culture reaches 1×10⁻⁶. 9 CFU / mL, yielding Pseudomonas AL4-3-1 bacterial suspension.

[0081] 2. All indoor pot experiments used the "Zhengdan 958" maize variety as the research object. Healthy, uniformly sized, mature, and plump maize seeds were selected, disinfected with 75% alcohol for 1 minute, rinsed 5 times with sterile water, and germinated in the dark for 2 days. When the maize sprouts reached 1 cm in length, they were transplanted into flowerpots, with 4 plants per pot. Watering was done every 2 days. Five days after transplanting, 30 mL of the above-mentioned Pseudomonas AL4-3-1 bacterial solution was used for root drenching. The same method was repeated 7 days later. The control group was drenched with an equal volume of LB medium. After 15 days, 4 plants from each group were randomly selected to measure various agronomic indicators such as plant height, stem diameter, and root length, and the average values ​​were calculated. The results are shown in Table 1.

[0082] Table 1. Growth Indicators of Maize in Each Group

[0083] Pseudomonas AL4-3-1 27.92±1.32a 0.79±0.02a 31.62±1.55a Comparison 23.38±0.51b 0.66±0.03b 25.65±0.50b

[0084] Note: The data in the table are mean ± SE. Different letters in the same column indicate significant differences (P < 0.05).

[0085] As shown in Table 1, the growth indicators of corn treated with Pseudomonas AL4-3-1 bacterial solution were significantly better than those of the control group, indicating that Pseudomonas AL4-3-1 has a growth-promoting effect on plants.

[0086] As can be seen from the above embodiments, the present invention provides a strain of Pseudomonas AL4-3-1 with functions of phosphorus solubilization, potassium solubilization, and IAA and siderophore production, and its application. This strain has the ability to solubilize phosphorus, potassium, and produce IAA and siderophores, and can promote plant growth.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A strain of Pseudomonas ( Pseudomonas sp AL4-3-1, characterized in that, It is deposited at the Guangdong Provincial Center for Microbial Culture Collection, with accession number GDMCC No:67689, deposit date January 16, 2026, and deposit location No. 100 Xianlie Middle Road, Yuexiu District, Guangzhou, Guangdong Academy of Sciences Institute of Microbiology.

2. The method for preparing the bacterial suspension of Pseudomonas AL4-3-1 according to claim 1, characterized in that, Includes the following steps: (1) Pick Pseudomonas AL4-3-1 on LB medium plates and incubate at 24 ~ 26℃ for 48 h to obtain slant culture; (2) Pick the slant culture into LB liquid medium and shake it for 24 to 36 hours to obtain the seed culture; (3) Inoculate the seed culture into the fermentation medium and shake to culture until 1 ~ 9 × 10⁻⁶. 9 CFU / mL, to obtain Pseudomonas AL4-3-1 bacterial suspension; The fermentation culture temperature is 24 ~ 26℃, and the rotation speed is 180 ~ 220 rpm; The inoculation amount of the seed solution is 2-8%.

3. The use of Pseudomonas AL4-3-1 as described in claim 1 in any one or more of the following: (1) Applications in phosphorus dissolution and / or potassium solubilization; (2) Application in iron-producing carriers and / or IAA; (3) Application in promoting plant growth; (4) Application in the preparation of soluble phosphorus and / or potassium-solubilizing products; (5) Application in the preparation of iron carriers and / or IAA products; (6) Application in the preparation of products that promote plant growth.

4. The application according to claim 3, characterized in that, The product is a microbial agent, microbial fertilizer, or soil remediation agent.

5. A microbial inoculant, characterized in that, A bacterial suspension containing the *Pseudomonas* strain of claim 1, wherein the effective viable count in the bacterial suspension is 1 to 9 × 10⁻⁶. 9 CFU / mL.

6. The microbial agent according to claim 5, characterized in that, The microbial agent is in the form of a liquid or a solid.

7. A method for promoting plant growth, characterized in that, The microbial agent described in claim 5 is used to treat the roots of plants by root irrigation.

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