Plant growth-promoting rhizobacteria composition for improving salt stress resistance of plants and application of plant growth-promoting rhizobacteria composition

Abstract

The invention discloses a growth-promoting rhizobacteria composition for improving salt stress resistance of plants and application of the growth-promoting rhizobacteria composition, and belongs to the technical field of application of microorganisms. The growth-promoting rhizobacteria composition disclosed by the invention comprises bacillus subtilis BK73 of which the preservation number is CGMCC (China General Microbiological Culture Collection Center) NO.32725 and enterobacter lutei FZ20 of which the preservation number is CGMCC NO.32550. The invention further discloses a preparation method of the growth-promoting rhizobacteria composition. The bacillus subtilis BK73 has the activity of producing ACC deaminase and can be used for synthesizing gamma-polyglutamic acid, and the enterobacter lewis FZ20 has the capabilities of fixing nitrogen, dissolving phosphorus and producing IAA (Indoleacetic Acid). Plant experiments show that the plant growth-promoting bacterium composition provided by the invention exerts a synergistic effect among strains, and has an obvious promoting effect on germination of corn seeds, growth of corn plants and salt stress tolerance of the corn plants under salt stress. The invention provides a novel growth-promoting bacterium composition for improving the salt tolerance of plants, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of microbial application, and in particular to a rhizosphere growth-promoting bacteria composition for improving the salt stress tolerance of plants and an application thereof. Background Art

[0002] Soil salinization is one of the causes of desertification and a major threat to soil function. The accumulation of soil salt caused by salinization will reduce crop yields, forage quality and tree survival rate, affect the livelihood choices and land use strategies of farmers and herdsmen, and thus endanger the sustainable development of agriculture, animal husbandry and forestry. At the same time, salt accumulation will accelerate vegetation and soil degradation, destroy the self-regulation ability of ecosystems, endanger geology, resources and national security, and lead to imbalanced social and economic development. At present, the global land area affected by salinization is about 1.0×10 9 hm 2 The resulting economic losses are as high as 2.73×10 10 USD, and the area of ​​salinized land is still increasing at an annual rate of 1.5×10 7 -2.0×10 7 hm 2 The rate of growth of the soil is increasing. Excessive accumulation of any form of salt in the soil will have an adverse effect on plant growth and its physiological processes. Salt stress, as one of the main abiotic stresses in nature, causes osmotic stress, ion stress and oxidative stress to plants, hinders the absorption of water and nutrients by plants, and inhibits the normal conduct of photosynthesis. This not only interferes with the normal physiological metabolic processes of plants at various growth stages such as seed germination, seedling growth and reproduction, but also seriously affects the production potential and function of plants in the ecosystem. Therefore, enhancing plant salt tolerance, promoting plant growth and improving the utilization of salinized land are not only important contents of global land degradation and sustainable agriculture research in arid areas, but also an inevitable choice to ensure ecological security, stabilize economic growth, achieve a balance between cultivated land occupation and compensation, and solve population-resource-environment problems. Microbial measures are currently a hot topic in the research of salinized land improvement. It uses the combined action of plants and beneficial microorganisms in saline habitats to improve the soil. It improves plant growth potential and induces plant salt tolerance under the premise of respecting the original genetic background of plants. It has the advantages of low cost, high efficiency, quick results and environmental protection.

[0003] Plant growth-promoting rhizo bacteria (PGPR) refers to beneficial bacteria in the rhizosphere soil of plants that have the characteristics of inhibiting plant diseases and promoting plant growth. It is also the most widely used microorganism in current microbial improvement measures. A large number of independent experimental studies have proved that PGPR can change the physiological metabolic pathways of host plants by analyzing the changes in different salt tolerance indicators, thereby alleviating the harm caused by salt stress to host plants. Some scholars have also classified and sorted out the effective PGPR strains and their salt tolerance characteristics used in existing studies, laying the foundation for the research and development and application of microbial fertilizers. At present, the research on rhizosphere growth-promoting bacteria focuses on screening strains with more outstanding growth-promoting effects among known rhizosphere growth-promoting bacteria or developing new strains with growth-promoting effects. It is urgent to provide a rhizosphere growth-promoting bacteria composition obtained by compounding different strains to obtain a growth-promoting effect that is better than the effect of any single strain of the selected bacteria. Summary of the invention

[0004] The purpose of the present invention is to provide a rhizosphere growth-promoting bacteria composition for improving the salt stress tolerance of plants and its application, so as to solve the problems existing in the above-mentioned prior art. The rhizosphere growth-promoting bacteria composition provided by the present invention can adapt to saline-alkali environment, promote plant growth and improve the salt stress tolerance of plants under salt stress, and the growth-promoting effect is significantly stronger than that of single bacteria treatment.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a rhizosphere growth-promoting bacteria composition for improving the salt stress tolerance of plants, comprising Bacillus subtilis BK73 and Enterobacter ludwigii FZ20;

[0007] The Bacillus subtilis BK73 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC NO.32725, the deposit date is November 20, 2024, and the deposit address is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing;

[0008] The Enterobacter reuteri FZ20 is deposited in the General Microbiology Center of the China Microorganism Culture Collection Administration, with the deposit number CGMCC NO.32550, the deposit date November 11, 2024, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

[0009] The present invention also provides an application of the rhizosphere growth-promoting bacteria composition in the preparation of a bacterial agent for improving the salt stress tolerance of plants.

[0010] The invention also provides a growth-promoting bacterial agent for improving the salt stress tolerance of plants, which contains the rhizosphere growth-promoting bacterial composition.

[0011] Optionally, the absorbance of the growth-promoting bacteriostatic agent at a wavelength of 600 nm is not less than 1.

[0012] Optionally, the ratio of the viable cell count of the Bacillus subtilis BK73 to the viable cell count of the Enterobacter reuteri FZ20 is 1:1.

[0013] The present invention also provides an application of the rhizosphere growth-promoting bacteria composition or the growth-promoting bacteria agent in any of the following items:

[0014] (1) Application in the production of ACC deaminase;

[0015] (2) Application in the production of γ-polyglutamic acid;

[0016] (3) Application in promoting plant growth;

[0017] (4) Application in improving plant tolerance to salt stress.

[0018] Preferably, the plant is corn.

[0019] The present invention also provides a method for promoting plant growth and / or improving plant salt stress tolerance, comprising the step of applying the rhizosphere growth-promoting bacteria composition or the growth-promoting bacteria agent to the plant growth environment.

[0020] Preferably, the plant is corn.

[0021] Preferably, the plant growth environment is a saline environment.

[0022] The present invention discloses the following technical effects:

[0023] The rhizosphere growth-promoting bacteria composition provided by the present invention includes Bacillus subtilis BK73 with a preservation number of CGMCC NO.32725 and Enterobacter reuteri FZ20 with a preservation number of CGMCC NO.32550. Bacillus subtilis BK73 and Enterobacter reuteri FZ20 have no antagonistic effect and have good adaptability to saline-alkali soil. Bacillus subtilis BK73 has the activity of producing ACC deaminase and can synthesize γ-polyglutamic acid, and Enterobacter reuteri FZ20 has the ability to fix nitrogen, dissolve phosphorus and produce IAA. Plant experiments show that the rhizosphere growth-promoting bacteria composition provided by the present invention exerts a synergistic effect between bacterial species, and has a significant promoting effect on the germination of corn seeds under salt stress, the growth of plants, and the ability to tolerate salt stress. The present invention provides a new growth-promoting bacteria composition for improving plant salt tolerance, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a graph showing the antagonistic reaction test results of the rhizosphere growth-promoting bacteria composition of Bacillus subtilis BK73 and Enterobacter reuteri FZ20;

[0026] Figure 2 This is a graph showing the results of the determination of the ACC deaminase production capacity of Bacillus subtilis BK73 in the rhizosphere growth-promoting bacteria composition;

[0027] Figure 3 This is the infrared spectrum test result of γ-polyglutamic acid standard;

[0028] Figure 4 This is the infrared spectrum detection result of the fermentation liquid of Bacillus subtilis BK73 in the rhizosphere growth-promoting bacteria composition;

[0029] Figure 5 This is a graph showing the results of high performance liquid chromatography testing of γ-polyglutamic acid standards;

[0030] Figure 6 This is a graph showing the results of high performance liquid chromatography testing of the fermentation broth of Bacillus subtilis BK73 in the rhizosphere growth-promoting bacteria composition;

[0031] Figure 7 This is a graph showing the nitrogen fixation ability test results of Enterobacter reuteri FZ20 in the rhizosphere growth-promoting bacteria composition;

[0032] Figure 8 This is a graph showing the results of the test of the phosphorus solubilization ability of Enterobacter reuteri FZ20 in the rhizosphere growth-promoting bacteria composition;

[0033] Fig. 9 This is a graph showing the IAA production capacity test results of Enterobacter reuteri FZ20 in the rhizosphere growth-promoting bacteria composition;

[0034] Fig.10 The figure shows the phenotypic observation results of the effects of Bacillus subtilis BK73, Enterobacter reuteri FZ20 and the rhizosphere growth-promoting bacteria composition on corn seed germination under 300 mM salt stress; wherein Control is the control group;

[0035] Fig.11 This is a statistical result diagram of the effects of Bacillus subtilis BK73, Enterobacter reuteri FZ20 and rhizosphere growth-promoting bacteria composition on the germination rate of corn seeds under 300mM salt stress; wherein Control is the control group; ###indicates P < 0.001 compared with the control group; *** indicates P < 0.001 compared with NaCl treatment;

[0036] Fig.12 Phenotypic observation results of the effects of Bacillus subtilis BK73, Enterobacter reuteri FZ20 and rhizosphere growth-promoting bacteria combination on corn growth under 300mM salt stress; Control is the control group;

[0037] Fig.13 The figure is a statistical result of the effects of Bacillus subtilis BK73, Enterobacter reuteri FZ20 and rhizosphere growth-promoting bacteria combination on corn biomass (root length, stem length, stem diameter, root weight and stem weight) under 300mM salt stress; wherein Control is the control group; # Compared with the control group, P < 0.05, ## =Indicates P < 0.01 compared with the control group; * indicates P < 0.05 compared with the NaCl treatment; ** indicates P < 0.01 compared with the NaCl treatment; *** indicates P < 0.001 compared with the NaCl treatment;

[0038] Fig.14 The figure is a statistical result of the effects of Bacillus subtilis BK73, Enterobacter reuteri FZ20 and rhizosphere growth-promoting bacteria composition on maize physiological and biochemical indices (malondialdehyde content, proline content, POD enzyme activity, SOD enzyme activity and soluble sugar content) under 300mM salt stress; wherein Control is the control group; # Compared with the control group, P < 0.05, ## Compared with the control group, P < 0.01, ### =Indicates P < 0.001 compared with the control group; * indicates P < 0.05 compared with the NaCl treatment; ** indicates P < 0.01 compared with the NaCl treatment; *** indicates P < 0.001 compared with the NaCl treatment;

[0039] Fig.15 This is a scanning electron microscope observation of the colonization of Bacillus subtilis BK73, Enterobacter reuteri FZ20 and the rhizosphere growth-promoting bacteria composition in the roots of corn plants; wherein Control is the control group. DETAILED DESCRIPTION

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0044] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0045] Bacillus subtilis is a kind of bacterium in the genus Bacillus. It is mesophilic, aerobic, and spore-forming. It has diverse physiological characteristics and is very easy to separate and culture. It is widely present in nature, non-toxic and harmless to humans and animals, and does not pollute the environment. It is a non-pathogenic bacterium. It can produce abundant antibacterial substances, such as lipopeptides, peptides, phospholipids, polyenes, amino acids, and nucleic acids, etc., which have good inhibitory effects on fungi, bacteria, viruses, and mycoplasmas. At the same time, it can produce growth hormones such as auxin, gibberellins, cytokinins, abscisic acid, and ethylene, which promote plant growth and then improve plant growth and development. Bacillus subtilis is one of the dominant microbial populations in soil and plant microecology, and has strong stress resistance and antibacterial, disease-preventing, and yield-increasing effects.

[0046] Enterobacter ludwigii is a Gram-negative bacterium belonging to the family Enterobacteriaceae. This strain is usually found in water bodies, soil, and plant root microecology. It has certain growth-promoting properties and has been studied for use in the agricultural field. It can help plants grow under adverse conditions through a variety of mechanisms, including the production of plant hormones (such as indoleacetic acid), nitrogen fixation, and decomposition of organic matter. Enterobacter ludwigii can also reduce the harm of salt stress to plants by regulating the osmotic balance in plants, thereby enhancing the growth ability of plants in high-salt environments. In addition, it has strong adaptability to the environment and is a plant growth-promoting strain with great potential.

[0047] In the previous study, the inventor isolated a strain of Bacillus subtilis from the rhizosphere soil of rice, named Bacillus subtilis BK73, and deposited it in the General Microbiological Center of China Microbiological Culture Collection Administration, with the deposit number CGMCCNO.32725, the deposit date is November 20, 2024, and the deposit address is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing;

[0048] At the same time, a strain of Enterobacter reuteri was isolated and named Enterobacter reuteri FZ20. It was deposited in the General Microbiology Center of China Culture Collection Administration, with the deposit number CGMCC NO.32550, the deposit date of November 11, 2024, and the deposit address of No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing.

[0049] The culture medium components and preparation method of the present invention are as follows:

[0050] LB liquid medium: 10 g tryptone, 5 g yeast extract, 10 g NaCl, dilute to 1 L with ddH2O, and sterilize with high pressure steam at 121°C for 30 min;

[0051] ADF medium was prepared according to the literature “Methods for isolating and characterizingACCdeaminase-containing plant growth-promoting rhizobacteria[J].PhysiologiaPlantarum,2003,118(1):10-15.”;

[0052] Ashuber nitrogen-free medium: KH2PO4 0.2 g, MgSO4·7H2O 0.2 g, NaCl 0.2 g, CaCO3 5.0 g, mannitol 10 g, CaSO4·2H2O 0.1 g, make up to 1 L with ddH2O, adjust pH to 7.0-7.5, and sterilize by high-pressure steam at 121°C for 30 min.

[0053] PKO medium: glucose 10 g, (NH4)2SO4 0.5 g, yeast extract 0.5 g, NaCl 0.2 g, KCl 0.3 g, MgSO4·7H2O 0.1 g, FeSO4 0.003 g, MnSO4 0.03 g, Ca3(PO4) 25.0 g, agar 20.0 g, make up to 1 L with distilled water, adjust the pH to 6.8-7.0, and sterilize by high-pressure steam at 115°C for 30 min.

[0054] Example 1

[0055] 1. Preparation of rhizosphere growth-promoting bacteria composition

[0056] 1. Antagonistic reaction test between strains

[0057] The two strains to be tested were crossed and the growth of the two strains was observed after 1 day. If the growth was good, it meant that the strains had no antagonism, and if the growth was bad, it meant that there was antagonism.

[0058] Test results such as Figure 1 , Bacillus subtilis BK73 and Enterobacter reuteri FZ20 grew well, indicating that the two strains had no antagonism, could coexist, and could be mixed cultured.

[0059] 2. Preparation of rhizosphere growth-promoting bacteria composition

[0060] Bacillus subtilis BK73 and Enterobacter reuteri FZ20 were streaked into LB medium at a culture temperature of 30°C for 12 h.

[0061] Single colonies were picked and inoculated into LB liquid medium and cultured in a shaking incubator (30°C, 220 r / min) for 5 h. After the strains were fully grown, the OD value of the strain suspension was measured with an ultraviolet spectrophotometer. 600 The absorbance was measured at room temperature, and Bacillus subtilis BK73 and Enterobacter reuteri FZ20 were mixed at a bacterial cell number ratio of 1:1.

[0062] 2. Detection of functional activity of rhizosphere growth-promoting bacteria

[0063] 1. Determination of ACC deaminase activity of Bacillus subtilis

[0064] Inoculate the strain on ADF medium, place the plate upside down at 30℃ and observe whether the strain grows. If it can grow on ADF medium with only ACC (1-aminocyclopropane-1-carboxylic acid) as the only nitrogen, it means that it can produce ACC deaminase, which inhibits the production of ethylene precursor α-ketobutyric acid. This reduces ethylene production and reduces the inhibition of plants.

[0065] Test results such as Figure 2 As shown, Bacillus subtilis BK73 can grow in ADF medium, indicating that it can produce ACC deaminase.

[0066] 2. Qualitative and quantitative detection of γ-PGA produced by Bacillus subtilis

[0067] γ-PGA is a high molecular weight glutamic acid polymer obtained by polymerizing α-amine and γ-carboxyl groups via γ-amide bonds. Polyamide has a series of characteristic absorption peaks and can be easily identified by infrared spectroscopy (FTIR). By comparing the infrared spectra of the fermentation broth of Bacillus subtilis BK73 with the infrared spectra of the γ-PGA standard, it can be seen whether the infrared spectrum of the fermentation broth overlaps with the infrared spectrum of the standard. If there is an overlap, it means that Bacillus subtilis BK73 produces γ-PGA.

[0068] FTIR test results are as follows Figure 3 and Figure 4 As shown, compared Figure 3 and Figure 4 The two infrared spectra show that the characteristic absorption peaks of the two samples are basically consistent. -l The absorption peak at is the NH symmetric stretching oscillation band. Due to the presence of a large number of hydrogen bonds on the γ-PGA molecule, VNH moves toward the low frequency direction, and the peak is strong and wide; the wave number (σ / cm -1 ) The 2000-1500 region is mainly the stretching vibration of double bonds such as C=C, C=O, and C=N. The extract is 1636.00 cm -1 The absorption peak at is the stretching vibration band of C=O; the extract is 1403.47cm -1 The absorption peak at 1223.68cm is the symmetrical vibration absorption peak of carboxyl (COOH); -1 This indicates the presence of -CH2 or -CH3 (bending vibration) in the molecular structure, at 2935.60 cm -1 The saturated CH bond stretching vibration band is at 900-500cm-1, and the broad absorption peak at the low frequency region is due to the plane rocking vibration and in-plane bending vibration of (CH2)n (n>4). By analyzing the spectrum and comparing with the standard spectrum, it can be known that the polymer is γ-PGA.

[0069] Next, γ-PGA in the fermentation broth of Bacillus subtilis BK73 was quantitatively analyzed by high performance liquid chromatography (HPLC).

[0070] HPLC identification results are as follows Figure 5 and Figure 6As shown, by comparing the HPLC spectra of the fermentation solution of Bacillus subtilis BK73 and the commercial γ-polyglutamic acid standard, it was found that the UV spectrum and the HPLC retention time of the target metabolite were consistent with the γ-polyglutamic acid standard. The results showed that the metabolite secreted by Bacillus subtilis BK73 was γ-polyglutamic acid.

[0071] 3. Determination of the functional activity of E. reuteri FZ20

[0072] The Enterobacter reuteri FZ20 was activated, placed in a shaker at 220 rpm and 30°C for 12 hours, and the nitrogen fixation, phosphorus solubilization and IAA production abilities of the Enterobacter reuteri FZ20 were measured.

[0073] Nitrogen fixation: The screened strain is inoculated onto Ashuber's nitrogen-free culture medium. The large, raised, mucus-like colonies are nitrogen-fixing bacteria.

[0074] Phosphorus solubilization: Inoculate the screened strains onto PKO culture medium plates, culture at 30°C for 3-5 days, and observe whether transparent circles appear in the corresponding strains.

[0075] IAA production: The screened strains were inoculated in a medium supplemented with 100-400 μg mL -1 LB medium containing L-tryptophan was cultured at (25±2)℃ for 48h. After the culture was completed, the LB bacterial culture was centrifuged (8000r / min, 10min) and the supernatant was collected for determination. 2mL of supernatant and 4mL of Salkowski reagent (50mL 35% H2SO4 and 1mL 0.5mol·L -1 Mix the two and leave them in the dark for 30 minutes. Observe. If the color turns pink, it indicates the production of IAA.

[0076] Nitrogen fixation test results Figure 7 The results of the dissolved phosphorus test are shown in Figure 8 As shown, the IAA production test results are as follows Fig. 9 As shown, the above results indicate that Enterobacter reuteri FZ20 has the ability to fix nitrogen, solubilize phosphate and produce IAA.

[0077] 3. Detection of plant growth-promoting function of rhizosphere growth-promoting bacteria composition

[0078] 1. Corn seed germination experiment

[0079] OD 600=1 Bacillus subtilis BK73 solution, Enterobacter reuteri FZ20 solution or Bacillus subtilis BK73 + Enterobacter reuteri FZ20 solution (live bacteria count 1:1) at 22°C overnight. The next day, the liquid on the surface of the seeds was absorbed and the seeds were placed in a covered glass culture dish with a double layer of filter paper. 100 corn seeds were evenly placed in each dish. 20 mL of 300 mmol / L NaCl solution was added respectively, and each group was repeated 3 times.

[0080] The culture dish was then placed in an incubator with a light duration of 16h / 8h (day / night) and a temperature of 22°C for seed germination test. The germination status of the corn seeds was observed regularly. During the test, the NaCl treatment solution was replaced every 24h to ensure the consistency of salt concentration between treatments.

[0081] Test results such as Fig.10 and Fig.11 As shown, the results showed that the growth-promoting bacteria combination had a better effect on corn seed germination than a single bacteria.

[0082] 2. Corn pot experiment

[0083] Select corn seeds with full appearance and uniform size, soak the seeds in 75% alcohol for 2 minutes for disinfection, then treat the seeds with 10% sodium hypochlorite for 10 minutes and rinse thoroughly with sterile water 5-6 times.

[0084] After disinfection, soak the seeds in sterile water for 24 hours, and place the disinfected seeds on a filter paper plate with water for germination. After observing for 1-2 days, select the seeds that have germinated and grown uniformly, and transfer them to separate pots. Each pot contains only one seed. After transfer, add an appropriate amount of sterile water to each pot. The experimental group used 5mL of bacterial fermentation liquid (OD 600 =1.0) treatment. The flower pots were cultured in an incubator at 22°C for 21 days, ensuring that sterile water was added regularly to maintain adequate humidity.

[0085] At the beginning, 300mM NaCl solution was irrigated every day for 7 days. Then, 5mL of bacterial fermentation liquid was evenly poured around the roots every 2 days. The corn seedlings were cultured at 22℃ with a photoperiod of 16h light / 8h dark for 21 days, and then various biomass tests and various physiological and biochemical index tests were performed.

[0086] The phenotypic observation results of corn seedlings are as follows Fig.12 As shown in the figure, from the phenotypic observation, the rhizosphere growth-promoting bacteria combination (Bacillus subtilis BK73 + Enterobacter reuteri FZ20) has a better effect on the growth of corn seedlings than a single bacteria. Fig.13 and Fig.14As shown, the biomass (root length, root weight, stem diameter, stem length, stem weight) and physiological and biochemical indicators (malondialdehyde content, proline content, POD enzyme activity, SOD enzyme activity and soluble sugar content) were detected. According to the test results, when Bacillus subtilis and Enterobacter reuteri acted on corn separately, they had a significant promoting effect on the growth and stress resistance response of corn seedlings. When Bacillus subtilis and Enterobacter reuteri were combined and compounded, they were applied to corn seedlings. It was found that the growth-promoting bacteria composition significantly promoted the increase of corn biomass, and was significantly better than the single bacteria in most physiological and biochemical indicators.

[0087] 3. Observation of the colonization of the strain in the root

[0088] The results are as follows Fig.15 As shown, through electron microscope observation, it was found that the number of rhizosphere microorganisms in the rhizosphere growth-promoting bacteria composition (Bacillus subtilis BK73 + Enterobacter reuteri FZ20) was significantly greater than that in the single bacteria group. This shows that the rhizosphere growth-promoting bacteria composition provided by the present invention plays a role in the physiological function of the plant rhizosphere and enhances the salt stress tolerance of corn seedlings.

[0089] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A rhizosphere growth-promoting bacteria composition for improving plant tolerance to salt stress, characterized in that: Including Bacillus subtilis BK73 and Enterobacter ludwigii FZ20; The Bacillus subtilis BK73 is deposited in the General Microbiology Center of China Microorganism Culture Collection Administration, with the deposit number CGMCC NO.32725, the deposit date is November 20, 2024, and the deposit address is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing; The Enterobacter reuteri FZ20 is deposited in the General Microbiology Center of the China Microorganism Culture Collection Administration, with the deposit number CGMCC NO.32550, the deposit date November 11, 2024, and the deposit address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing.

2. Use of the rhizosphere growth-promoting bacteria composition according to claim 1 in the preparation of a bacterial agent for improving the salt stress tolerance of plants.

3. A growth-promoting agent for improving the salt stress tolerance of plants, characterized in that: Contains the rhizosphere growth-promoting bacteria composition according to claim 1.

4. The growth-promoting bacterial agent according to claim 3, characterized in that The absorbance value of the growth-promoting bacteriostatic agent at a wavelength of 600 nm is not less than 1.

5. The growth-promoting bacterial agent according to claim 3, characterized in that The ratio of the viable bacterial count of the Bacillus subtilis BK73 to that of the Enterobacter reuteri FZ20 is 1:

1.

6. Use of the rhizosphere growth-promoting bacteria composition according to claim 1 or the growth-promoting bacteria agent according to any one of claims 3 to 5 in any of the following: (1) Application in the production of ACC deaminase; (2) Application in the production of γ-polyglutamic acid; (3) Application in promoting plant growth; (4) Application in improving plant tolerance to salt stress.

7. The use according to claim 6, characterized in that The plant is corn.

8. A method for promoting plant growth and / or improving plant salt stress tolerance, characterized in that: The method comprises the step of applying the rhizosphere growth-promoting bacteria composition according to claim 1 or the growth-promoting bacteria agent according to any one of claims 3 to 5 to the plant growth environment.

9. The method according to claim 8, characterized in that The plant is corn.

10. The method according to claim 8, characterized in that The plant growth environment is a salt-containing environment.

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