Aeromonas guinea, soil conditioner, plant growth-promoting microbial inoculum, method and application of aeromonas guinea, soil conditioner and plant growth-promoting microbial inoculum

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to Aeromonas guinea, a soil conditioner, a plant growth-promoting microbial agent, a method and application. The invention provides Aeromonas caviae PJ3-6, and the preservation number of the Aeromonas caviae PJ3-6 is CGMCC (China General Microbiological Culture Collection Center) No. 33770. The Aeromonas caviridis PJ3-6 provided by the invention can promote plant growth, has a growth promoting effect on wheat, and can improve soil, increase the content of available phosphorus in the soil and reduce the conductivity of the soil. The result of the embodiment shows that after the aeromonas caviridis PJ3-6 bacterial suspension is applied to wheat, the content of rapidly available phosphorus in soil can be increased, the conductivity of the soil is reduced, the fresh weight and dry weight of the overground part of a wheat plant, the leaf area and the leaf perimeter are remarkably increased, and the root volume and the root tip number of a wheat root system are also remarkably increased.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a strain of Aeromonas vaginalis, a soil conditioner, a plant growth promoter, a method, and its application. Background Technology

[0002] Soil salinization has become a global agricultural ecological and environmental problem, posing a major abiotic stress factor threatening global agricultural production and crop yields. High salt concentrations in soil significantly affect plant growth and development, even leading to plant death and reduced land utilization. Currently used methods for improving saline-alkali land include irrigation to leach salt, deep tillage with imported soil, and the use of chemical amendments. These methods can improve soil conditions to some extent, but they are costly and prone to causing secondary pollution. How to improve and efficiently utilize saline-alkali land, and how to protect and enhance the ability of important economic crops to withstand salt stress, are critical agricultural science and technology issues that the international community urgently needs to address.

[0003] Rhizosphere soil contains a rich variety of beneficial microorganisms that can directly or indirectly promote plant growth through one or more mechanisms. These mechanisms include promoting the absorption and utilization of mineral nutrients, producing plant growth hormones, secreting antibiotics to protect plants from pathogens, and activating plant defense systems to resist stress. Utilizing beneficial rhizosphere microorganisms to improve the physical and chemical properties of saline-alkali soils, enhance crop salt tolerance, and promote crop growth is characterized by low investment, rapid results, and high efficiency. Therefore, applying rhizosphere microorganisms or microbial fertilizers to the soil in agricultural production can effectively reduce the adverse effects of traditional soil improvement methods, and is more conducive to soil health and environmental protection.

[0004] The existing technology reports Aeromonas vaginalis for the degradation of typical fluoroquinolone antibiotics, the preparation of selenium nanoparticles, and the lysis of bacteriophages. Summary of the Invention

[0005] The purpose of this invention is to provide a strain of Aeromonas caviae, a soil conditioner, a plant growth promoter, a method, and applications. The Aeromonas caviae PJ3-6 provided by this invention can improve soil and promote plant growth.

[0006] To address the aforementioned technical problems, the following technical solutions are proposed:

[0007] This invention provides a strain of Aeromonas caviae PJ3-6, with accession number CGMCCNo.33770.

[0008] This invention provides the application of Aeromonas hydrophila PJ3-6 described in the above technical solution in at least one of the following 1) to 4):

[0009] 1) Soil improvement;

[0010] 2) Promote plant growth;

[0011] 3) Improve the salt and alkali tolerance of plants;

[0012] 4) Prepare bio-fertilizers.

[0013] Preferably, the soil improvement includes increasing the available phosphorus content of the soil and / or reducing the soil electrical conductivity.

[0014] Preferably, the plant growth promotion includes increasing the aboveground fresh weight, dry weight, leaf area, leaf circumference, and promoting root development, or one or more of these.

[0015] Preferably, promoting root development includes increasing root volume and / or increasing the number of root tips.

[0016] Preferably, the Aeromonas hydrophila PJ3-6 is administered in the form of a bacterial suspension.

[0017] This invention provides a soil conditioner and / or a plant growth promoter, comprising Aeromonas guinea pig PJ3-6 as described in the above technical solution.

[0018] The present invention provides a method for improving soil and / or enhancing the salt and alkali tolerance of plants, comprising: applying Aeromonas guinea pig PJ3-6 as described in the above-mentioned technical solution to planted plants.

[0019] Preferably, the application method includes root irrigation and / or foliar spraying.

[0020] Preferably, when the application method is root irrigation, the application rate of the inoculant containing Aeromonas guinea pig PJ3-6 is 4-10 kg per mu; when the application method is foliar spraying, the application rate of the inoculant containing Aeromonas guinea pig PJ3-6 is 2-3 kg per mu.

[0021] The beneficial effects of this invention: This invention provides a strain of Aeromonas caviae, PJ3-6, with the preservation number CGMCC No. 33770. The Aeromonas caviae PJ3-6 provided by this invention can decompose insoluble phosphorus, increase the concentration of soluble phosphorus, and synthesize indoleacetic acid, promoting plant growth. It also has a growth-promoting effect on wheat, and can improve soil, increasing the available phosphorus content and reducing soil electrical conductivity. The results of the examples show that after applying the Aeromonas caviae PJ3-6 bacterial suspension to wheat, it can increase the available phosphorus content in the soil, reduce soil electrical conductivity, and significantly increase the fresh and dry weight of the aboveground parts of wheat plants, leaf area, and leaf perimeter. The root volume and root tip number of wheat roots also significantly increase.

[0022] In summary, the Aeromonas hydrophila PJ3-6 of this invention has broad application prospects in soil improvement and plant growth promotion.

[0023] Biological Preservation Instructions

[0024] Aeromonas caviae PJ3-6 was deposited on March 10, 2025, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCCNo.33770. The deposit address is No.3, No.1 Beichen West Road, Chaoyang District, Beijing. Attached Figure Description

[0025] Figure 1 Colony diagram and Gram staining diagram of strain PJ3-6;

[0026] Figure 2 Phylogenetic tree of strain PJ3-6;

[0027] Figure 3 Figure showing the effect of different salt concentrations on the growth of strain PJ3-6;

[0028] Figure 4 Figure showing the effect of different temperatures on the growth of strain PJ3-6;

[0029] Figure 5 Figure showing the effect of different initial pH values ​​on the growth of strain PJ3-6;

[0030] Figure 6 The figure shows the effect of different liquid volumes on the growth of strain PJ3-6. Detailed Implementation

[0031] This invention provides a strain of Aeromonas caviae, PJ3-6, with accession number CGMCC No. 33770. The 16S rDNA gene sequence of Aeromonas caviae PJ3-6 described in this invention is shown in SEQ ID NO. 1.

[0032] This invention collected soil samples from coastal saline soil in a rice-wheat rotation system in the Modern Agricultural Development Zone of Qianwan New Area, Ningbo City, Zhejiang Province, and screened out a growth-promoting strain, PJ3-6, capable of phosphorus solubilization and indoleacetic acid production. The 16S rDNA gene sequence of strain PJ3-6 was compared with the 16S rDNA sequences of other strains in NCBI's GenBank database to construct a phylogenetic tree for strain PJ3-6. Based on the colony morphology and physiological and biochemical characteristics of strain PJ3-6, it was identified as *Aeromonas caviae*.

[0033] This invention provides the application of Aeromonas hydrophila PJ3-6 described in the above-mentioned technical solution in soil improvement and / or plant growth promotion.

[0034] As an optional implementation, the soil improvement of the present invention includes increasing the available phosphorus content of the soil and / or reducing the soil electrical conductivity.

[0035] As an optional embodiment, the plant growth promotion of the present invention includes increasing the fresh weight, dry weight, leaf area, and leaf circumference of the aboveground parts of the plant, and promoting root development, or one or more of these. As an optional embodiment, the root development promotion of the present invention includes increasing root volume and / or increasing the number of root tips. As an optional embodiment, the plant of the present invention includes wheat.

[0036] In this embodiment of the invention, Aeromonas vaginalis PJ3-6, after being prepared into a bacterial suspension and applied to wheat, increased the available phosphorus content in the soil, reduced the soil electrical conductivity, and significantly increased the fresh and dry weight of the aboveground parts of wheat plants, leaf area, leaf perimeter, root volume, and root tip number. The Aeromonas vaginalis PJ3-6 described in this invention has a good growth-promoting effect on wheat.

[0037] This invention provides the application of Aeromonas vaginalis PJ3-6, as described in the above-mentioned technical solution, in improving the salt and alkali tolerance of plants. Aeromonas vaginalis PJ3-6 exhibits a certain degree of salt and alkali tolerance, growing well in a salt concentration range of 2% to 4%. Furthermore, Aeromonas vaginalis PJ3-6 grows well at pH levels of 5 to 11, demonstrating strong acid and alkali resistance, indicating that Aeromonas vaginalis PJ3-6 can grow well in most soils in my country, showing promising application prospects.

[0038] This invention provides the application of Aeromonas hydrophila PJ3-6 described in the above technical solution in the preparation of bio-fertilizer.

[0039] The Aeromonas guinea pig PJ3-6 provided by this invention can convert unavailable phosphorus into available phosphorus, promote the conversion of soil phosphorus, increase the content of available phosphorus in the soil, improve fertilizer utilization, promote plant growth and development, root development and fertilizer absorption, and also has the potential to improve saline-alkali soil.

[0040] This invention provides a plant growth-promoting bacterial agent, comprising *Aeromonas guinea pig* PJ3-6 as described in the above-mentioned technical solution. *Aeromonas guinea pig* PJ3-6 of this invention has the ability to secrete indoleacetic acid (IAA), reaching 24.96 μg / mL. *Aeromonas guinea pig* PJ3-6 of this invention can convert insoluble phosphorus into soluble phosphorus, with a phosphorus solubilization capacity of 108.71 μg / mL. Because *Aeromonas guinea pig* PJ3-6 can secrete indoleacetic acid and convert insoluble phosphorus into soluble phosphorus, it has a plant growth-promoting effect.

[0041] This invention provides a soil conditioner comprising Aeromonas guinea pig PJ3-6 as described in the above technical solution.

[0042] In this invention, the viable count of Aeromonas guinea pig PJ3-6 in the plant growth-promoting bacterial agent can be ≥1×10⁻⁶. 8 CFU / g or ≥1×10 8 CFU / mL, and can even be 1×10 8 CFU / g or 1×10 8 CFU / mL.

[0043] In this invention, the viable count of Aeromonas guinea pig PJ3-6 in the soil conditioner can be ≥1×10⁻⁶. 8 CFU / g or ≥1×10 8 CFU / mL, and can even be 1×10 8 CFU / g or 1×10 8 CFU / mL.

[0044] As an optional implementation, the Aeromonas hydrophila PJ3-6 can be used in the form of bacterial suspension.

[0045] As an optional embodiment, the method for preparing the bacterial suspension according to the present invention may include: inoculating the Aeromonas vaginalis PJ3-6 in a culture medium and culturing it to obtain the bacterial suspension. As an optional embodiment, the culturing temperature of the present invention may be 10–40°C, 15–35°C, 20–30°C, or more preferably 30°C. As an optional embodiment, the culturing time may be 12–36 h, or 18–30 h; in the embodiments of the present invention, the culturing time may be 18–24 h. As an optional embodiment, the culturing rotation speed may be 150–250 rpm, 180–230 rpm, or more preferably 200 rpm.

[0046] The present invention provides a method for improving soil and / or enhancing the salt and alkali tolerance of plants, comprising: applying Aeromonas guinea pig PJ3-6 as described in the above-mentioned technical solution to the soil in which the plants are grown.

[0047] As an optional implementation, the Aeromonas hydrophila PJ3-6 can be used in the form of bacterial suspension.

[0048] As an optional implementation, the soil conditioner and / or plant growth promoter of the present invention is applied by root irrigation and / or foliar spraying. The viable count of Aeromonas guinea pig PJ3-6 in the soil conditioner and / or plant growth promoter is 1×10⁻⁶. 8When the application method is root irrigation, the application rate of the soil conditioner or plant growth promoter is 4-10 kg per mu; when the application method is foliar spraying, the application rate is 2-3 kg per mu.

[0049] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0050] 1. Culture medium

[0051] (1) The composition of LB liquid medium is: 10.0g tryptone, 10.0g NaCl, 5.0g yeast extract, and 1L distilled water. Sterilize at 121℃ for 20min. If solid LB medium is required, add agar powder at a volume of 1.5% of the LB liquid medium volume.

[0052] (2) The inorganic phosphorus medium consists of: Ca3(PO4)2 5.0g, NaCl 0.3g, KCl 0.3g, FeSO4·7H2O 0.03g, MgSO4·7H2O 0.3g, (NH4)2SO4 0.5g, MnSO4·4H2O 0.03g, glucose 10.0g, and distilled water 1000mL. The pH value is 7.0-7.5. The medium is sterilized at 121℃ for 20min. If a solid inorganic phosphorus medium is required, agar powder is added at 1.5% of the inorganic phosphorus medium volume.

[0053] Example 1

[0054] 1. Soil samples were collected from the Modern Agricultural Development Zone of Qianwan New Area, Ningbo City, Zhejiang Province. The soil samples were coastal saline soil from a rice-wheat rotation system (30.33236°N, 121.38936°E). The soil samples were sieved after root selection, and 1.0 g of soil was weighed and placed in an Erlenmeyer flask containing 20 small glass beads and 20 mL of sterile water. The flask was shaken at 200 rpm for 30 min at 30℃ and then allowed to stand for about 2 h. 1 mL of the supernatant was added to 20 mL of LB liquid medium and mixed well. The flask was then incubated at 200 rpm for 72 h. The bacterial suspension was then diluted to 10⁻¹⁰. -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 Different concentrations were diluted (100 μL each) and spread onto LB agar plates. After incubation at 30°C for 72 h, single colonies with different morphologies were picked and streaked continuously for purification and culture. Colony growth was observed. The purified strains were then inoculated onto LB agar plates and stored at 4°C for later use.

[0055] 2. Screening of phosphate-solubilizing bacteria: The strains isolated and purified in step 1 above were inoculated into inorganic phosphorus solid culture medium and cultured at 30°C for 7 days. Strains with phosphate-solubilizing ability were then screened.

[0056] 3. Screening of IAA-producing bacteria: The phosphate-solubilizing strains obtained in step 2 were inoculated into LB liquid medium containing 200 mg / L tryptophan and cultured at 30°C and 250 rpm for 2 days. 50 μL of the bacterial suspension was dropped onto a white ceramic plate, and an equal volume of Salkowski colorimetric solution was added. After standing for 30 minutes at room temperature in the dark, the color was observed. If the color turned red, it indicated the production of IAA. 50 μL of 50 mg / L IAA standard solution was added as a positive control. A phosphate-solubilizing strain capable of producing IAA was screened and named PJ3-6. The Salkowski colorimetric solution consisted of 50 mL of HClO4 solution and 1 mL of FeCl3 solution; the volume concentration of HClO4 solution was 35%, and the concentration of FeCl3 solution was 0.5 mol / L.

[0057] 5. Strain PJ3-6 was sequenced by Shanghai Jieli Biotechnology Co., Ltd. Based on the 16S rDNA sequencing results (as shown in SEQ ID No. 1), the results were analyzed online at the National Center for Biotechnology Information (NCBI) website (http: / / www.ncbi.nlm.nih.gov). Homology comparisons were performed with the 16S rDNA sequences of other strains in GenBank using Blast software. Similar sequences were selected and used with the PJ3-6 sequence to construct a 16S rDNA phylogenetic tree for PJ3-6 using MEGA 7 software.

[0058] SEQ ID No. 1:

[0059]

[0060] Strain PJ3-6 colonies appear milky white on LB solid medium. Figure 1 ), round, with a raised surface, neat, smooth, and moist edges; colonies are opaque; Gram-negative; phylogenetic tree shown. Figure 2 .

[0061] Example 2

[0062] The following physiological and biochemical parameters of strain PJ3-6 were determined.

[0063] 1. Aerobic performance test:

[0064] Pour sterilized LB solid medium into three sterilized test tubes, filling them approximately two-thirds full. On a sterile work surface, use an inoculation needle to pick up strain PJ3-6 from the agar slant culture and puncture it into the medium (the puncture must reach the bottom of the tube). Incubate at 30°C and observe the results from day 3 to day 7. Bacteria growing on the surface of the agar column are aerobic, while those growing along the puncture line are anaerobic or facultative anaerobic.

[0065] The test results showed that strain PJ3-6 colonies grew on the surface and were aerobic bacteria.

[0066] 2. Contact enzyme test:

[0067] Place one drop of 3% H2O2 solution on a clean glass slide. Take one loop of LB solid medium slant culture of strain PJ3-6, which has been cultured for 18-24 hours, and spread it in H2O2. If bubbles are produced, the result is positive; otherwise, the result is negative.

[0068] The test results showed that strain PJ3-6 was positive for catalase.

[0069] 3. Methyl red test (MR test):

[0070] (1) Culture medium and reagents:

[0071] The culture medium consists of 5g peptone, 5g glucose, 5g sodium chloride and 1L distilled water, adjusted to pH 7.0-7.2; the culture medium is dispensed into test tubes, 4-5mL per tube, and sterilized at 121℃ for 20min.

[0072] Reagents: 0.1g methyl red, 300mL 95% ethanol and 200mL distilled water, mixed thoroughly.

[0073] (2) Culture and observation of results:

[0074] Bacterial culture: Inoculate strain PJ3-6 into the above culture medium and incubate at 30℃ for 1-2 days. Add a few drops of methyl red reagent to the resulting culture solution. If the culture solution turns red, it is methyl red positive; if it turns yellow, it is negative (the color change range of methyl red is 4.4-6.0, from red to yellow).

[0075] The test results showed that strain PJ3-6 was positive for methyl red.

[0076] 4. Acetylmethylethanol test (VP test):

[0077] (1) Culture medium: The culture medium is the same as that used in the methyl red test.

[0078] (2) Culture and observation of results:

[0079] The bacterial culture is the same as the methyl red test. When performing the VP test, take about 2 mL of culture medium and mix it with an equal volume of NaOH solution (40% concentration). Then add 1 mg of creatine, shake thoroughly for 2-5 minutes, and if the culture medium turns red, the VP test is positive.

[0080] The test results showed that strain PJ3-6 was VP negative.

[0081] 5. Starch hydrolysis:

[0082] (1) Culture medium and reagents:

[0083] The broth peptone agar composition was: 3g beef extract, 10g peptone, 5g NaCl, and 1000mL water, pH 7.0–7.2.

[0084] Add 0.2% soluble starch to broth peptone agar to obtain culture medium 2. Dispense culture medium 2 into Erlenmeyer flasks and sterilize at 121℃ for 20 min for later use.

[0085] Lugol's iodine solution: 1g iodine tablets, 2g potassium iodide and water; preparation method: first dissolve potassium iodide in a small amount (3-5mL) of distilled water, then add iodine tablets, and after the iodine is completely dissolved, dilute with water to 300mL.

[0086] (2) Culture and observation of results:

[0087] Inoculate strain PJ3-6 onto a plate and incubate at 30°C for 2-4 days. After colonies form, add Lugol's iodine solution to the plate, ensuring it covers the area around the colonies. The plate should turn blue. If a colorless transparent zone appears around the colonies, it indicates that the starch has been hydrolyzed. The size of the transparent zone generally indicates the degree of starch hydrolysis.

[0088] The test results showed that strain PJ3-6 was positive for starch hydrolysis.

[0089] 6. Gelatin liquefaction:

[0090] (1) Culture medium and reagents: 5g peptone, 120g gelatin, 1000mL distilled water. Adjust the pH to 7.2-7.4, dispense into test tubes, the culture medium height is about 4-5cm, sterilize at 121℃ for 20min.

[0091] (2) Culture and observation of results: Inoculate strain PJ3-6 in the center of a test tube using the puncture method. Incubate at 30℃ for one month and observe whether the gelatin liquefies.

[0092] The test results showed that strain PJ3-6 was positive for gelatin liquefaction.

[0093] 7. Nitrate reduction test:

[0094] (1) Culture medium and reagents:

[0095] The nitrate liquid culture medium consists of 10g peptone, 1g KNO3 and 1000mL distilled water, pH 7.0-7.4, sterilized at 121℃ for 20min.

[0096] Reagents: Gries reagents: Solution A: 0.5g of p-aminobenzenesulfonic acid and 150mL of dilute acetic acid solution with a volume concentration of about 10%; Solution B: 0.1g of α-naphthol, 20mL of distilled water, and 150mL of dilute acetic acid solution with a volume concentration of about 10%.

[0097] (2) Culture and Observation of Results: Strain PJ3-6 was inoculated into nitrate liquid medium and cultured at 30℃ for 1 day to obtain culture solution 1, culture solution 2 for 3 days at 30℃, and culture solution 3 for 5 days at 30℃. 50 μL of culture solution 1 to 3 was poured into the small holes of a white porcelain dish, and then 1 drop of solution A and 1 drop of solution B were added to each. If the culture solution turned pink, rose red, orange, or brown, it indicated the presence of nitrite, indicating a positive result for nitrate reduction; otherwise, it was negative.

[0098] The test results showed that strain PJ3-6 was positive for nitrate reduction.

[0099] 8. Citrate utilization test:

[0100] (1) Culture medium and reagents: Citrate medium: 2g sodium citrate, 5g NaCl, 0.2g MgSO4·7H2O, 1g (NH4)2·HPO4, 10mL 1% bromothymol blue aqueous solution, 20g agar, 1L water, pH 6.8-7.0, dispensed into test tubes, sterilized at 121℃ for 20min, and placed at an angle.

[0101] (2) Culture and observation of results: Young strains (cultured for 18-24 hours) were inoculated onto slant test tubes and cultured at 30°C for 3-7 days. A positive reaction was indicated by an alkaline (blue) culture medium, while a negative reaction was indicated by no change in the culture medium.

[0102] The test results showed that strain PJ3-6 was positive for citrate utilization.

[0103] The results are shown in Table 1. Strain PJ3-6 was Gram-negative, aerobic, catalase-positive, MR test-positive, VP test-negative, starch hydrolysis-positive, nitrate reduction test-positive, citrate utilization test-positive, and gelatin liquefaction-positive.

[0104] Table 1. Physiological and biochemical characteristics of strain PJ3-6

[0105] project result project result Gram staining - VP test - Aerobic test aerobic Starch hydrolysis test + Catalase test + Gelatin liquefaction test + Methyl red (MR) test + Citrate utilization test + Nitrate reduction test +

[0106] Note: "+" indicates positive; "-" indicates negative.

[0107] Based on the above-mentioned physiological and biochemical characteristics of this strain and the phylogenetic tree in Example 1, this strain PJ3-6 was identified as Aeromonas caviae, i.e., Aeromonas caviae PJ3-6.

[0108] Example 3

[0109] To further verify the optimal fermentation conditions of strain PJ3-6 obtained in Example 1, clarify the salt and alkali tolerance of PJ3-6, and explore the effects of different salt concentrations, temperatures, liquid volumes, and initial pH on the growth of the strain.

[0110] Preparation of PJ3-6 seed culture: The strain PJ3-6 was inoculated into LB liquid medium and cultured at 30℃ and 250rpm for 18h to the logarithmic growth phase to obtain the seed culture.

[0111] 1. Analysis of bacterial growth conditions

[0112] (1) Effects of different salt concentrations on the growth of strain PJ3-6

[0113] NaCl was added to LB liquid medium to achieve concentrations of 2%, 4%, 6%, 8%, and 10%, with three replicates for each NaCl concentration treatment. PJ3-6 seed culture was inoculated at a 1% (v / v) inoculum and cultured at 30℃ and 250 rpm for 2 days, after which the OD was measured. 600 To compare the growth of the strains. The results are as follows: Figure 3 As shown in Table 2, PJ3-6 has a certain salt tolerance and grows well in the salt concentration range of 2% to 4%.

[0114] Table 2. Growth of Aeromonas guinea pig PJ3-6 under different salt concentrations.

[0115]

[0116] Note: Different letters indicate significant differences at the P<0.05 level.

[0117] (2) Effects of different temperatures on the growth of strain PJ3-6

[0118] LB medium was placed in Erlenmeyer flasks, and PJ3-6 plants in the logarithmic growth phase were inoculated at a 1% (v / v) inoculum. The plants were cultured at 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, and 45℃ at 250 rpm for 2 days, after which the OD was measured. 600 To compare the growth of the strains, three parallel experiments were set up for each temperature treatment. The results are as follows: Figure 4 As shown in Table 3, PJ3-6 grows well at a culture temperature of 10–40℃, with the best growth at 30℃.

[0119] Table 3. Growth of Aeromonas guinea pig PJ3-6 at different culture temperatures.

[0120]

[0121] Note: Different letters indicate significant differences at the P<0.05 level.

[0122] (3) Effect of different initial pH on the growth of PJ3-6

[0123] The initial pH of LB liquid medium was adjusted to 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14, with three replicates for each pH value. PJ3-6 seed culture in the logarithmic growth phase was inoculated at a 1% (v / v) inoculum. After culturing at 30℃ and 250 rpm for 2 days, OD was measured. 600 To compare the growth of the strains. The results are as follows: Figure 5 As shown in Table 4, PJ3-6 grows well at pH 5 to 11 and has strong resistance to acid and alkali. It can grow well in most soils in my country.

[0124] Table 4. Growth of Aeromonas guinea pig PJ3-6 at different initial pH values.

[0125]

[0126]

[0127] Note: Different letters indicate significant differences at the P<0.05 level.

[0128] (4) Effect of different liquid contents on the growth of PJ3-6

[0129] LB liquid medium was dispensed into Erlenmeyer flasks at volume ratios of 20%, 30%, 40%, and 50%, with three replicates for each treatment. PJ3-6 seed culture in the logarithmic growth phase was inoculated at a 1% (v / v) inoculum. After culturing at 30°C and 250 rpm for 2 days, OD was measured. 600 To compare the growth of the strains. The results are as follows: Figure 6 As shown in Table 5, PJ3-6 grew well at liquid contents ranging from 20% to 50%.

[0130] Table 5. Growth of Aeromonas vaginalis PJ3-6 with different liquid volumes in guinea pigs.

[0131] Liquid volume (%) 20 30 40 50 <![CDATA[OD 600 ]]> 2.729±0.124a 2.721±0.213a 2.177±0.162b 2.849±0.088a

[0132] Note: Different letters indicate significant differences at the P<0.05 level.

[0133] Example 4

[0134] The strain PJ3-6 of this invention has a significant growth-promoting effect on wheat, increasing the content of available phosphorus in the soil and reducing soil electrical conductivity. This is illustrated below through a pot experiment.

[0135] 1. The test soil was taken from the Modern Agricultural Development Zone of Qianwan New Area, Ningbo City, Zhejiang Province. The soil sample was coastal saline soil of rice-wheat rotation (30.33236°N, 121.38936°E). The basic physicochemical properties of the test soil are as follows: total carbon 12.93 g / kg, total nitrogen 1.06 g / kg, available phosphorus 31.86 mg / kg, available potassium 417.90 mg / kg, pH 8.93. 110 g of air-dried soil that had passed through a 4 mm sieve was dispensed into 100 mL plastic beakers, sealed with plastic wrap, and sent to Nanjing Zhenglong Biotechnology Co., Ltd. for irradiation sterilization. The beakers were then dispensed into beakers for the PJ3-6 treatment group and the blank control group.

[0136] 2. Sterilize the surface of wheat seeds, then place them on a sterile culture medium and germinate them in the dark at 28°C for 2 days.

[0137] 3. Set up a PJ3-6 treatment group and a blank control group (CK). The only difference between the PJ3-6 treatment group and the CK was that the PJ3-6 treatment group had the addition of strain PJ3-6, and the inoculum size of strain PJ3-6 was 10. 6 cfu / g dry soil; CK group did not receive strain PJ3-6. Five replicates were performed for each treatment group and CK group.

[0138] Both the treatment group and the control (CK) were pre-cultured at 28℃ for 2 days, and then the soil moisture content was adjusted to 60% of the field capacity. Pre-germinated wheat seeds were then planted in beakers, with two seeds per beaker. After germination, the best-growing plant was retained. The wheat was cultured at 25℃ under conditions of 16 h / d light and 8 h / d darkness, and was regularly watered with sterile water to maintain consistent moisture content across treatments. Destructive sampling was performed on days 15 and 30 of culture to determine soil available phosphorus, pH, and electrical conductivity. Three plant samples were randomly selected for analysis of wheat biomass and root morphology.

[0139] The determination of available phosphorus in soil is based on the standard NY / T1121.7-2014, "Soil Testing Part 7: Determination of Available Phosphorus in Soil"; the determination of soil pH is based on the potentiometric method (HJ 962-2018); and the determination of soil electrical conductivity is based on the electrode method (HJ 802-2016).

[0140] Three plant samples were randomly selected to measure indicators such as wheat biomass and root morphology.

[0141] Separate the above-ground and underground parts of the plant after cleaning, and dry the surface moisture with absorbent paper. Immediately weigh each part using an electronic balance and record the fresh weight.

[0142] After cleaning, place the above-ground and underground parts of the plant separately in an 80℃ oven for 2-3 days to dry to constant weight, and record the dry weight.

[0143] Leaf area was measured using a Jieyu high-definition camera and Wanshen LA-S leaf analysis software, and root morphology and structure were measured using a root scanner and Wanshen LA-S root analysis software.

[0144] The results are shown in Tables 6-9. Table 6 shows that inoculation with PJ3-6 significantly increased the content of available phosphorus in the soil, significantly reduced soil electrical conductivity, and also showed a decreasing trend in soil pH, which has a positive effect on the improvement of saline-alkali land. Table 7 shows that inoculation with PJ3-6 significantly increased the fresh and dry weight of wheat aboveground biomass, and the fresh and dry weight of underground parts also showed an increasing trend compared to the control (CK). Table 8 shows that inoculation with PJ3-6 significantly increased wheat leaf area and leaf perimeter, promoting leaf development. Table 9 shows that inoculation with PJ3-6 significantly promoted wheat root development, resulting in a significant increase in root volume and root tip number compared to the control (CK). Therefore, it can be seen that the strain PJ3-6 of this invention has multiple functions including salt tolerance, phosphorus solubilization, and IAA production, and can be applied in saline-alkali soils to increase the content of available phosphorus, reduce soil electrical conductivity, and promote plant leaf growth and root development.

[0145] Table 6. Effects of inoculated strain PJ3-6 on soil physicochemical properties.

[0146]

[0147] Note: * represents P<0.05, ** represents P<0.01.

[0148] Table 7. Effects of inoculated strain PJ3-6 on wheat plant biomass.

[0149]

[0150] Note: * represents P<0.05, ** represents P<0.01.

[0151] Table 8. Effects of inoculated strain PJ3-6 on wheat leaf parameters.

[0152]

[0153] Note: * represents P<0.05, ** represents P<0.01, and *** represents P<0.001.

[0154] Table 9. Effects of inoculated strain PJ3-6 on wheat root morphology and structure.

[0155]

[0156] Note: * represents P<0.05, ** represents P<0.01.

[0157] In summary, the Aeromonas hydrophila PJ3-6 provided by this invention has multiple functions such as salt tolerance, phosphorus solubilization, and indoleacetic acid production. It can adapt to saline-alkali soils, increase the available phosphorus content of the soil, reduce soil electrical conductivity, and promote wheat leaf growth and root development. It has good application prospects in promoting plant growth and improving soil in saline-alkali lands.

[0158] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A strain of Aeromonas caviae PJ3-6, with accession number CGMCC No. 33770.

2. The use of Aeromonas hydrophila PJ3-6 of claim 1 in at least one of the following 1) to 4): 1) Soil improvement; 2) Promote plant growth; 3) Improve the salt and alkali tolerance of plants; 4) Prepare bio-fertilizer.

3. The application according to claim 2, characterized in that, The soil improvement includes increasing the available phosphorus content of the soil and / or reducing the soil electrical conductivity.

4. The application according to claim 2, characterized in that, The plant growth promotion includes increasing the aboveground fresh weight, dry weight, leaf area, leaf circumference, and promoting root development, or one or more of these factors.

5. The application according to claim 2, characterized in that, The promotion of root development includes increasing root volume and / or increasing the number of root tips.

6. The application according to claim 2, characterized in that, The Aeromonas vaginalis PJ3-6 was administered in the form of a bacterial solution.

7. A soil conditioner and / or plant growth promoter, characterized in that, Includes Aeromonas guinea pig PJ3-6 as described in claim 1.

8. A method for improving soil and / or enhancing plant salt and alkali tolerance, characterized in that, include: Apply Aeromonas guinea pig PJ3-6 as described in claim 1 to plant cultivation.

9. The method according to claim 8, characterized in that, The application methods include root irrigation and / or foliar spraying.

10. The method according to claim 9, characterized in that, When the application method is root irrigation, the application rate of the inoculant containing Aeromonas guinea pig PJ3-6 is 4-10 kg per mu; when the application method is foliar spraying, the application rate of the inoculant containing Aeromonas guinea pig PJ3-6 is 2-3 kg per mu.

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