Bacillus amyloliquefaciens NECC10723 and application thereof

Abstract

The invention relates to the technical field of microorganisms, in particular to bacillus amyloliquefaciens NECC10723 and application of the bacillus amyloliquefaciens NECC10723, the preservation number of the bacillus amyloliquefaciens NECC10723 is CGMCC No.36726, the bacillus amyloliquefaciens NECC10723 is preserved in the China General Microbiological Culture Collection Center, the preservation date is November 21, 2025, and the preservation address is No.3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The strain NECC10723 can increase the content of nutrient elements in crops and promote the growth of the crops under saline-alkali stress; osmotic regulation substances in crops are increased, and osmotic balance is maintained; accumulation of ROS and hydrogen peroxide of crops is reduced, and the content of antioxidant enzymes is increased, so that the antioxidant capacity of the crops is improved; the soil enzyme activity and the soil nutrient content are improved, and conversion and utilization of nutrient components in the soil are promoted.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and more specifically, to a Bacillus amyloliquefaciens NECC10723 and its applications. Background Technology

[0002] Soil salinization significantly impacts crop growth and yield, becoming a major factor restricting modern agricultural and economic development. Under saline-alkali stress, crops struggle to grow normally, leading to reduced yields or crop failure, impaired root growth, physiological drought, and lower seedling survival rates. Therefore, alleviating crop saline-alkali stress and promoting increased yields and efficiency in saline-alkali land is of great significance to the needs of the nation and its people.

[0003] Plant rhizosphere growth-promoting bacteria (PGPRs) are a class of bacteria that promote plant growth within the rhizosphere. Rhizosphere soil microorganisms are the second genome of plants, playing a crucial role in improving crop growth and yield in saline-alkali soils and in soil remediation. Studies have found that applying salt-tolerant PGPRs can alleviate the growth stress of salt and alkali on various crops, including peppers, tomatoes, soybeans, wheat, rapeseed, and lettuce. PGPRs can induce increased activity of antioxidant enzymes in crops under salt and alkali stress, a key mechanism for crops to reduce the damage caused by reactive oxygen species (ROS) under such stress. The mechanisms by which PGPRs help crops improve their salt and alkali tolerance and promote growth under salt and alkali stress mainly involve the synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, the biosynthesis of plant hormones, the induction of systemic tolerance, and osmotic protection. Therefore, developing plant rhizosphere growth-promoting bacteria with the function of alleviating the damage of salt and alkali stress to crops and improving the soil environment is of great significance to agricultural development. Summary of the Invention

[0004] To address the above-mentioned problems, this invention provides a Bacillus amyloliquefaciens NECC10723 and its applications.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a Bacillus amyloliquefaciens NECC10723, which has the accession number CCMCCNo.36726.

[0006] In a second aspect, the present invention provides a microbial inoculum containing the aforementioned Bacillus amyloliquefaciens NECC10723.

[0007] In a third aspect, the present invention provides an application of the above-mentioned Bacillus amyloliquefaciens NECC10723.

[0008] Under the preferred embodiment, the application of Bacillus amyloliquefaciens NECC10723 includes at least one of the following uses: 1) Promotes plant growth; 2) Improve the salt and alkali tolerance of plants; 3) Increase the activity of urease, alkaline phosphatase and / or sucrase in the soil; 4) Increase the content of total nitrogen, available phosphorus and / or available potassium in the soil.

[0009] In the preferred scheme, promoting plant growth means increasing plant height, stem diameter, aboveground dry weight, and / or root-to-shoot ratio.

[0010] Beneficial effects of the present invention The *Bacillus amyloliquefaciens* NECC10723 provided by this invention exhibits strong salt and alkali tolerance, and can grow normally in a high-salt-alkali environment with a salt concentration of 200 mg / L and a pH of 9. Pot experiments show that applying bacterial suspension of strain NECC10723 under salt and alkali stress has the following advantages: 1) Promotes the growth of corn seedlings, increasing seedling height, stem diameter, dry weight, and root-to-shoot ratio; 2) Reduce the accumulation of ROS and hydrogen peroxide in corn seedlings and increase the content of antioxidant enzymes, thereby improving the antioxidant capacity of corn seedlings; 3) Increase the content of osmotic regulators (soluble sugars, soluble proteins, and free proline) in corn seedlings, maintain osmotic balance, and alleviate the damage of salt and alkali stress to the plants.

[0011] 4) Increase the content of nutrients (nitrogen, phosphorus, and potassium) in corn seedlings to promote plant growth; 5) Increase soil enzyme activity and soil nutrient content (total nitrogen, available phosphorus, and available potassium), and promote the transformation and utilization of nutrients in the soil. Attached Figure Description

[0012] Figure 1 Gram staining results for strain NECC10723; Figure 2 The results of 16S rDNA amplification of strain NECC10723; Figure 3 A phylogenetic tree was constructed based on the 16S rDNA gene sequence of strain NECC10723; Figure 4 The growth of strain NECC10723 on Assumption nitrogen-free solid medium plates; Figure 5 The growth of strain NECC10723 on inorganic phosphorus solid medium plates; Figure 6 The secretion of IAA by strain NECC10723; Figure 7The growth status of maize seedlings after 25 days of culture in the Con group without bacterial treatment and the C1-C4 groups with bacterial treatment under salt-alkali stress; Figure 8 The root growth status of maize in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) after 25 days of culture under salt-alkali stress; Figure 9 The accumulation level of superoxide anions in maize seedling leaves after 25 days of cultivation under salt-alkali stress in groups Con (without bacterial treatment) and groups C1-C4 (with bacterial treatment). Figure 10 The accumulation level of hydrogen peroxide in maize seedling leaves after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 11 The superoxide anion content in the leaves and roots of maize seedlings after 25 days of culture under salt-alkali stress, in the Con group without bacterial treatment and in the C1-C4 groups with bacterial treatment. Figure 12 The hydrogen peroxide content in the leaves and roots of maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 13 The superoxide dismutase activity in the leaves and roots of maize seedlings after 25 days of culture under salt-alkali stress in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment). Figure 14 The catalase activity in the leaves and roots of maize seedlings under salt-alkali stress was measured after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment). Figure 15 The ascorbic acid peroxidase activity in the leaves and roots of maize seedlings under salt-alkali stress was measured after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment). Figure 16 The content of soluble sugar in the leaves and roots of maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 17 The content of soluble protein in the leaves and roots of maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress. Figure 18 The content of free proline in the leaves and roots of maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 19 The total nitrogen content in maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 20 The total phosphorus content in maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 21The total potassium content in maize seedlings after 25 days of culture in the Con group (without bacterial treatment) and the C1-C4 groups (with bacterial treatment) under salt-alkali stress; Figure 22 The soil urease activity was measured after 25 days of culture in the Con group (without bacterial application) and the C1-C4 groups (with bacterial application) under saline-alkali stress. Figure 23 The soil alkaline phosphatase activity was measured after 25 days of incubation in the Con group (without bacterial application) and the C1-C4 groups (with bacterial application) under saline-alkali stress. Figure 24 The soil sucrase activity was measured after 25 days of incubation in the Con group (without bacterial application) and the C1-C4 groups (with bacterial application) under saline-alkali stress. Figure 25 The total nitrogen content of soil in the Con group (without bacterial application) and the C1-C4 groups (with bacterial application) after 25 days of culture under saline-alkali stress; Figure 26 The available phosphorus content in the soil of the Con group (without bacterial application) and the C1-C4 groups (with bacterial application) after 25 days of culture under saline-alkali stress; Figure 27 The available potassium content in the soil of the Con group (without bacterial application) and the C1-C4 groups (with bacterial application) after 25 days of culture under saline-alkali stress; In the image, Bam723-L represents the leaves of a corn seedling, and Bam723-R represents the roots of a corn seedling. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0014] Unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Unless otherwise specified, the experimental methods used in the examples are conventional methods. Where specific conditions are not specified in the examples, they should be performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0015] Example 1: Origin and Identification of Strain NECC10723 (also known as Bam723) 1. Source of the strain The strain NECC10723 was isolated from the root soil samples of salt-tolerant plants in Daqing using the dilution plate method.

[0016] 2. Identification of strains 2.1 Morphological characteristics and Gram staining identification A single colony of strain NECC10723 was picked and inoculated onto an LB agar plate. The colony morphology was observed to be rod-shaped. Gram staining of strain NECC10723 revealed a purple stain, confirming that strain NECC10723 is a Gram-positive bacterium. Figure 1 As shown.

[0017] 2.2 Identification of Physiological and Biochemical Characteristics The physiological and biochemical characteristics of strain NECC10723 were identified, and the results are shown in Table 1.

[0018] Table 1. Identification results of physiological and biochemical characteristics of strain NECC10723

[0019] Note: "+" indicates a positive result; "-" indicates a negative result.

[0020] Table 1 shows that strain NECC10723 tested positive in glucose (anaerobic), 3% hydrogen peroxide solution, semi-solid agar, nitrate (reducing), lysozyme nutrient broth, quality control nutrient broth, mannitol, and glucose phosphate peptone solution. Consultation of the bacterial identification manual indicates that strain NECC10723 shares similar physiological and biochemical characteristics with Bacillus spp., and it can be preliminarily identified as belonging to the Bacillus spp.

[0021] 2.3 Molecular identification Using the universal primers 27F and 1492R for bacterial 16S rDNA as templates, strain NECC10723 was amplified. The amplification results are as follows: Figure 2 As shown, the amplified fragment was sent for sequencing. The nucleotide sequencing results were then compared using BLAST on the NCBI website (https: / / www.ncbi.nlm.nih.gov / ). The analysis results are as follows. Figure 3 As shown, strain NECC10723 and Bacillus amyloliquefaciens Bacillus amyloliquefaciens strain HS8 (NCBI accession number GU323369) showed the highest similarity (98.92%). Based on morphological characteristics, Gram staining, and the strain's physiological and biochemical results, this strain can be preliminarily identified as *Bacillus amyloliquefaciens*. Bacillus amyloliquefaciens ).

[0022] Strain NECC10723 is Bacillus amyloliquefaciens ( Bacillus amyloliquefaciens strain This strain was deposited on November 21, 2025, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36726. The deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0023] Example 2: Functional identification of strain NECC10723 1. Alkali resistance test Single colonies of strain NECC10723 were inoculated at a rate of 1% onto LB solid medium plates with pH values ​​of 7.5, 8, 8.5, and 9, respectively, and cultured at 28°C for 48–72 h. The growth of the colonies was observed every 24 h, and the results are shown in Table 2.

[0024] Table 2. Results of alkali resistance test for strain NECC10723

[0025] Note: "√" indicates that the strain has grown, and "×" indicates that the strain has not grown (the same applies below).

[0026] As shown in Table 2, strain NECC10723 can grow normally on LB solid medium plates with pH values ​​ranging from 7.5 to 9, indicating that strain NECC10723 has good alkali tolerance.

[0027] 2. Salt tolerance test Single colonies of strain NECC10723 were inoculated at a rate of 1% onto LB solid medium plates containing 100 g / L, 120 g / L, 140 g / L, 160 g / L, 180 g / L, and 200 g / L NaCl, respectively, and incubated at 30°C for 48–72 h. The growth of the colonies was observed every 24 h, and the results are shown in Table 2.

[0028] Table 3. Results of alkali resistance test for strain NECC10723

[0029] As shown in Table 3, strain NECC10723 can still grow normally on LB solid medium plates with a NaCl concentration of 200 g / L, indicating that strain NECC10723 has good salt stress tolerance.

[0030] 3. Nitrogen fixation capacity test 3.1 Qualitative Judgment Single colonies of the activated strain NECC10723 were inoculated onto Assoube nitrogen-free solid medium plates and incubated at 30°C for 3 days. Colony growth was observed and recorded. Figure 4 As shown. From Figure 4 It can be seen that strain NECC10723 grows well on the plate, and obvious hydrolysis zones appear around the colonies, indicating that strain NECC10723 has good nitrogen fixation ability.

[0031] 3.2 Quantitative Measurement The activated strain NECC10723 was inoculated into Assumption nitrogen-free liquid medium at an inoculation rate of 1% and cultured in a shaker at 30℃ and 180rpm for 3 days. Three replicates were set up, and the ammonia nitrogen content in the culture system was quantitatively detected by indigo blue spectrophotometry. The results are shown in Table 4.

[0032] Table 4. Results of ammonia nitrogen secretion test for strain NECC10723

[0033] As shown in Table 4, strain NECC10723 has the ability to secrete ammonia nitrogen, with a yield of 0.18±0.03 mg / L.

[0034] 4. Inorganic phosphorus solvent desorption capacity test 4.1 Qualitative Judgment Single colonies of the activated strain NECC10723 were inoculated onto inorganic phosphorus solid medium plates at an inoculum rate of 1% and cultured at 30°C for 7 days. Three replicates were set up, and the colony growth was observed and recorded. Figure 5 The diameters of the phosphate-solubilizing zone (D) and colony diameters (d) were measured, and the average D / d ratio was calculated (Table 5). Figure 5 As can be seen from the average D / d ratio in Table 5, a distinct phosphate-solubilizing zone appears around the colony, indicating that strain NECC10723 has the ability to solubilize inorganic phosphorus.

[0035] Table 5 Results of inorganic phosphorus-scraping ability test of strain NECC10723

[0036] 4.2 Quantitative Measurement The activated strain NECC10723 was inoculated at a rate of 1% into an inorganic phosphorus liquid medium with an initial pH of 7.5. After culturing at 30℃ and 180 rpm for 7 days, the amount of dissolved phosphorus and pH in the fermentation broth were measured using the molybdenum antimony colorimetric method. This experiment used calcium phosphate as the sole inorganic phosphorus source and was conducted in triplicate. The results are shown in Table 6.

[0037] Table 6. Inorganic phosphorus solubility and pH in fermentation broth of strain NECC10723

[0038] As shown in Table 6, the phosphorus solubilization activity of strain NECC10723 is greater than 200 mg / L, indicating that strain NECC10723 has a good ability to solubilize inorganic phosphorus; and the pH of the fermentation broth is significantly reduced, indicating that strain NECC10723 has a good ability to reduce alkali.

[0039] 5. Organophosphate detoxification capacity test 5.1 Qualitative Judgment Single colonies of the activated strain NECC10723 were inoculated onto organophosphate solid medium plates at an inoculum rate of 1% and cultured at 30°C for 7 days. Three replicates were set up, and colony growth was observed and recorded. The diameter of the phosphate-solubilizing zone (D) and the colony diameter (d) were measured, and the average D / d ratio was calculated (Table 7). Observations revealed a distinct phosphate-solubilizing zone around the colonies, and the average D / d ratio was above 2, indicating that strain NECC10723 possesses a strong ability to solubilize organophosphates.

[0040] Table 7 Results of organophosphate solubilization test for strain NECC10723

[0041] 5.2 Quantitative Measurement The activated strain NECC10723 was inoculated at a rate of 1% into an organic phosphorus liquid medium with an initial pH of 7.5. After culturing at 30℃ and 180 rpm for 7 days, the amount of dissolved phosphorus and pH in the fermentation broth were measured using the molybdenum antimony colorimetric method. This experiment used lecithin as the sole phosphorus source for organic phosphorus and was conducted in triplicate. The results are shown in Table 8.

[0042] Table 8. Inorganic phosphorus solubility and pH in fermentation broth of strain NECC10723

[0043] As shown in Table 8, the organic phosphorus solubility of strain NECC10723 is 14.15±0.94 mg / L, indicating that strain NECC10723 has a good ability to solubilize organic phosphorus; and the pH of the fermentation broth is significantly reduced, further indicating that strain NECC10723 has a good ability to reduce alkali.

[0044] 6. Ability to secrete IAA 6.1 Qualitative Judgment Strain strain NECC10723 was inoculated into King liquid medium at a 1% inoculum and cultured in a constant temperature shaking incubator at 30℃ and 180rpm for 3 days. After centrifugation, the supernatant of the fermentation broth was collected and analyzed using the Salkowski colorimetric method. If the supernatant turned red, it could secrete IAA. The results were as follows. Figure 6 As shown. Figure 6 In the above, Bam723 is the supernatant of the fermentation broth, Bam723+S2 is the supernatant of the fermentation broth with added colorimetric solution, S2 is the colorimetric solution, and IAA+S2 is the positive control. Figure 6 It can be seen that the supernatant of the fermentation broth was milky white before the colorimetric solution was added, and the solution turned red after the colorimetric solution was added, indicating that strain NECC10723 has the ability to secrete IAA.

[0045] 6.2 Quantitative Measurement The OD of the fermentation broth after 3 days of culture (section 6.1) was determined using the Salkowski colorimetric method. 530nm The values ​​were substituted into the IAA standard curve to calculate the IAA secretion of strain NECC10723. The results are shown in Table 9.

[0046] Table 9. Results of IAA secretion test for strain NECC10723

[0047] As shown in Table 9, the IAA secretion of strain NECC10723 is above 5 mg / L, indicating that strain NECC10723 has a strong ability to secrete IAA.

[0048] 7. Protease production capacity Strains NECC10723 were inoculated at a rate of 1% onto skim milk powder solid medium plates and cultured at 30°C for 3 days. The diameters of the lysis zone (D) and colonies (d) were measured, and the average D / d ratio was calculated. The results are shown in Table 10. A higher average D / d ratio indicates a stronger protease production capacity of strain NECC10723.

[0049] Table 10. Results of protease production capacity test of strain NECC10723

[0050] As shown in Table 10, the average D / d ratio of strain NECC10723 is above 2, indicating that strain NECC10723 has good protease production ability.

[0051] Example 3: Pot Experiment 1. Pot experiment The soil used for the potted plants was natural saline-alkali soil from Daqing City, Heilongjiang Province. After thorough sun-drying, the soil was sieved through a 2mm sieve to remove withered grass, roots, and stones. The mixture was then thoroughly combined, and 600g of soil was placed in each pot. Basic soil chemical properties: pH 9.0, total salt content 0.85%, total nitrogen content 0.98 g·kg⁻¹. -1 Alkaline nitrogen content: 115.23 mg·kg -1 Available phosphorus content: 3.70 mg·kg -1 Available potassium content: 243.68 mg·kg -1 Organic matter content: 27.52 g·kg -1 Each treatment was performed in triplicate, with 10 pots per replicate. Plump, uniformly sized corn seeds were selected, disinfected, and sterilized before being sown in saline-alkali soil, with 5 seeds per pot. Strains NECC10723 were inoculated into LB broth (pH 7.5) and fermented at 28°C and 180 rpm until reaching a density of 1 × 10⁻⁶.8 cfu·mL -1 Set aside, dilute the bacterial suspension with sterile water to a concentration of 1 × 10⁻⁶. 4 cfu·mL -1 (C1) 1 × 10 5 cfu·mL -1 (C2) 1 × 10 6 cfu·mL -1 (C3) 1 × 10 7 cfu·mL -1 (C4) The inoculation method was to inoculate the bacterial solution into the pots one day in advance using a layered method, that is, to divide the potting soil into 3 layers, each layer containing 200 g of soil and 50 mL of bacterial solution, for a total inoculation volume of 150 mL per pot. The control was watered with sterile water (Con). After that, watering was done regularly and quantitatively. The day and night temperature was (25±2)℃ / (20±2)℃, the light was 12 h per day, and the light intensity was 1000 µmol·2·s. -1 The humidity is 60%~80%.

[0052] 2. Test Results 2.1 Effects of strain NECC10723 on maize seedling growth 1) Effects of strain NECC10723 on maize seedling growth Figure 7 The growth status of maize seedlings after 25 days of culture in groups Con (without bacterial treatment) and groups C1-C4 (with bacterial treatment). After applying Bam723, maize reached the three-leaf-one-heart stage after 25 days of growth. Figure 7 Visually, Bam723 application significantly increased maize plant height, and maize plant leaves were significantly larger than the control (Con). Under salt-alkali stress, leaves without any treatment showed obvious wilting and yellowing. With the increase of Bam723 bacterial concentration, maize seedling height, leaf size, and leaf chlorophyll retention all increased.

[0053] After applying Bam723, the corn reached the three-leaf stage 25 days later. The roots were then thoroughly cleaned. Figure 8 As shown, it can be clearly seen that after applying Bam723 bacterial solution, the root system of maize seedlings increased significantly. The dry weight of the roots of maize seedlings in groups C1 to C4 increased by 37.21%, 96.67%, 132.56%, and 162.80%, respectively. Moreover, the root length also increased with the increase of concentration, which significantly alleviated the inhibition of root length by salt and alkali stress and increased root vitality.

[0054] Table 11 Effects of strain NECC10723 on morphological parameters of maize seedlings under salt-alkali stress

[0055] Note: Data in the table are mean ± standard deviation. Different lowercase letters in the same column indicate significant differences between ANOVA and Duncan's new multiple range test. P <0.05).

[0056] Table 11 shows the test results of morphological indicators of maize seedlings after 25 days of inoculum treatment in groups Con (without inoculum) and groups C1-C4 (with inoculum). As shown in Table 11, compared with Con, the plant height, stem diameter, aboveground dry weight, underground dry weight, and root-to-shoot ratio of maize seedlings in groups C1-C4 increased significantly. Specifically, the plant height of maize seedlings in groups C1-C4 increased by 18.47%, 26.60%, 32.18%, and 43.45%, respectively; the stem diameter increased by 30.96%, 45.56%, 50.05%, and 64.47%, respectively; the aboveground dry weight increased by 14%, 67.44%, 110.47%, and 119.77%, respectively; the underground dry weight increased by 26.86%, 90.70%, 153.49%, and 183.72%, respectively; and the root-to-shoot ratio increased by 17.81%, 15.18%, 23.08%, and 23.29%, respectively. The results showed that applying Bam723 could significantly alleviate the inhibitory effect of salt-alkali stress on maize seedling growth and reduce the damage caused by salt-alkali stress to maize seedlings.

[0057] 2) Effects of strain NECC10723 on ROS accumulation and lipid peroxidation in maize seedlings NBT staining can reflect the level of superoxide anion accumulation in plant tissues, by Figure 9 It can be seen that under salt-alkali stress, compared with Con, the blue color of the leaves gradually becomes lighter and less as the concentration of Bam723 increases, indicating that the content of superoxide anions in maize leaves decreases with the increase of the concentration of Bacillus subtilis. Applying Bam723 can improve the antioxidant capacity of maize seedlings.

[0058] DAB staining can reflect the accumulation of hydrogen peroxide in plant tissues, by... Figure 10 It can be seen that under salt-alkali stress, compared with Con, the yellowing of leaves gradually becomes lighter and less as the concentration of Bam723 increases, indicating that the content of superoxide anions in maize leaves decreases with the increase of Bam723 concentration, and the application of Bam723 can improve the antioxidant capacity of maize seedlings.

[0059] Depend on Figures 11-12It was found that under salt-alkali stress, the contents of superoxide anion and malondialdehyde (MDA) in the leaves and roots of maize seedlings treated with Bam723 were significantly lower than those in the control group (Con), with the contents in the leaves being higher than those in the roots. After Bam723 inoculation, the superoxide anion contents in the leaves and roots of each treatment decreased by 8.72%, 17.12%, 17.50%, and 23.16% and 22.74%, 28.54%, 33.01%, and 45.22% compared to Con, respectively; the MDA contents in the leaves and roots of each treatment decreased by 6.41%, 7.33%, 16.75%, and 32.25% and 31.38%, 45.05%, 54.35%, and 71.75% compared to Con, respectively. The effect was most significant under the C4 treatment. The results indicate that the application of Bam723 can reduce the content of superoxide anions in plant leaves and root tissues, alleviate membrane lipid peroxidation induced by salt and alkali stress, and thus significantly reduce the content of malondialdehyde in maize seedlings.

[0060] 3) Effects of strain NECC10723 on antioxidant enzymes in maize seedlings SOD, CAT, and APX are all protective enzymes of the cell membrane system, which help maintain metabolic balance in plants when they are subjected to salt and alkali stress. Figures 13-15 It was found that under salt-alkali stress, the application of Bam723 significantly increased the activities of SOD, CAT, and APX enzymes in maize seedlings, and the activities of SOD, CAT, and APX enzymes in the leaves of maize seedlings treated with Bam723 were higher than those in the roots. At lower concentrations of Bacillus subtilis, there were no significant differences in enzyme activity among the treatments, but the activities of SOD, CAT, and APX enzymes all increased with increasing bacterial concentration, reaching their highest levels in the C4 treatment. The SOD activities in the leaves and roots of maize seedlings treated with Bam723 increased by 32.12% and 39.51%, and 32.08% and 37.34%, respectively; the CAT activities increased by 42.32% and 39.51%, and 50.27% and 77.95%, respectively; and the APX activities increased by 36.13% and 27.74%, and 73.36% and 76.43%, respectively.

[0061] 4) Effects of strain NECC10723 on osmotic regulators in maize seedlings Osmotic regulation is a crucial mechanism for crop stress resistance. Under salt-alkali stress, the content of soluble sugars plays a vital role in maintaining osmotic balance between vacuoles and protoplasm, as well as the activity of various enzymes in the cytoplasm. Soluble proteins can lower the osmotic potential within maize plants, preventing excessive water loss. Free proline in plants can increase the concentration of cell sap, thus protecting the protoplasm. Figures 16-18It was found that under salt-alkali stress, inoculation with Bam723 significantly increased the contents of soluble sugar, soluble protein, and free proline in maize seedlings. Furthermore, after inoculation with Bacillus subtilis, the content of osmotic regulators in maize seedling leaves was higher than that in roots. Inoculation with Bacillus subtilis increased the content of osmotic regulators in maize seedling leaves and roots. Compared with Con, the increase in the contents of soluble sugar, soluble protein, and free proline increased with the increase in the concentration of Bacillus subtilis. The C4 treatment showed the best effect, significantly higher than other treatments. The proline content in the leaves and roots of maize seedlings treated with Bam723 increased by 60.84% ​​and 52.87%, and 72.70% and 71.49%, respectively; the soluble sugar content increased by 40.26% and 36.18%, and 47.19% and 34.53%, respectively; and the soluble protein content increased by 43.11% and 25.33%, and 42.03% and 45.26%, respectively.

[0062] 5) Effects of strain NECC10723 on plant nutrients The content of common nutrients such as nitrogen, phosphorus, and potassium in plants can determine the soil's supply status, and can be used to diagnose crop nutrient levels, fertilization effects, and fertilizer utilization rates. Figures 19-21 It was found that after applying Bam723, the nitrogen, phosphorus, and potassium contents of plant leaves and roots increased significantly, and the increasing trend increased with the increase of the concentration of the applied bacterial solution. The nitrogen and potassium contents of plant leaves were higher than those of roots, while the phosphorus content of plant leaves was lower than that of roots. At low concentrations (C1 treatment), the total nitrogen, total phosphorus, and total potassium contents after applying Bam723 were not significantly different from those in Con, possibly because the concentration was too low for significant plant absorption. However, with the increase of the bacterial solution concentration, the total nitrogen, total phosphorus, and total potassium contents increased significantly, reaching the maximum in the C4 treatment. Compared with Con, Bam723 application increased the total nitrogen content in leaves by 36.21%, total phosphorus by 205.1%, and total potassium by 26.58%; and increased the total nitrogen content in roots by 21.69%, total phosphorus by 93.47%, and total potassium by 52.82%.

[0063] 2.2 Effects of strain NECC10723 on soil enzyme activity 1) Effects of strain NECC10723 on soil urease activity Soil urease activity can be used as an important indicator to measure nitrogen use in soil and has a significant impact on improving the salt and alkali tolerance of maize seedlings. Figure 22 It was found that saline-alkali stress (Con) significantly reduced urease activity in the rhizosphere soil of maize seedlings. In saline-alkali soil, the application of Bam723 significantly increased urease activity in all treatments compared to Con. After Bam723 application, the C4 treatment showed the highest urease activity, increasing by 19.31% compared to the Con treatment. This indicates that Bacillus has the effect of increasing urease activity in saline-alkali soil.

[0064] 2) Effects of strain NECC10723 on soil alkaline phosphatase activity Soil alkaline phosphatase participates in the decomposition of phosphorus-containing compounds in the soil and the phosphorus cycle, and can be used to indicate soil phosphorus levels. Figure 23 It was found that, compared with Con, treatments C1, C2, C3, and C4 significantly increased soil alkaline phosphatase activity. Compared with Con, the soil alkaline phosphatase activity in the C4 treatment group, which was treated with Bam723, reached the highest level, increasing by 31.77%, indicating that the application of Bam723 can effectively improve soil alkaline phosphatase activity under saline-alkali stress and promote the transformation and utilization of soil phosphorus.

[0065] 3) Effects of strain NECC10723 on soil sucrase activity Soil sucrase plays a crucial role in soil nutrient transformation and utilization, as well as carbon cycling; its activity reflects the transformation and decomposition of organic carbon in the soil. Figure 24 It can be seen that when Bam723 is applied to saline-alkali soil, the soil sucrase activity generally increases with the increase of the concentration of Bacillus spp. Compared with Con, the C1, C2, C3 and C4 treatments significantly increased the soil sucrase activity. In particular, the soil sucrase activity reached the highest level under the C4 treatment, which was 45.78% higher than that of Con. This indicates that Bam723 can help corn seedlings alleviate saline-alkali stress, which shows that Bacillus spp. can improve soil sucrase activity.

[0066] 2.3 Effects of strain NECC10723 on soil nutrients 1) Effects of strain NECC10723 on total nitrogen in soil The level of total nitrogen content in soil reflects the nitrogen status of the soil and is correlated with crop growth. Figure 25 It was found that after inoculating saline-alkali soil with Bam723, compared with Con, treatments C1, C2, C3, and C4 significantly increased the total nitrogen content of the soil, by 96.32%, 104.95%, 111.45%, and 137.54%, respectively. Inoculation with Bam723 significantly increased the total nitrogen content of the soil under saline-alkali stress, with treatment C4 showing the best increase of 137.54% compared to Con. This indicates that Bam723 can significantly increase the total nitrogen content in the rhizosphere soil of maize seedlings in saline-alkali soil, which may be related to the nitrogen-fixing function of Bacillus itself.

[0067] 2) Effects of strain NECC10723 on available phosphorus in soil The content of available phosphorus in soil reflects the soil's phosphorus supply status and is of great significance for maize growth in saline-alkali environments. Figure 26It was found that the application of Bam723 significantly increased the available phosphorus content in the soil. After inoculation with Bam723 in saline-alkali soil, compared with Con, the available phosphorus content in treatments C1, C2, C3, and C4 increased by 53.57%, 112.01%, 181.81%, and 295.49%, respectively. The available phosphorus content in the soil was directly proportional to the strain concentration, and the available phosphorus content reached its maximum under treatment C4, increasing by 295.49% compared to Con. This indicates that Bacillus can significantly increase the available phosphorus content in the rhizosphere soil of maize seedlings in saline-alkali soil, which is closely related to the phosphorus-solubilizing function and phytase production of Bacillus itself.

[0068] 3) Effects of strain NECC10723 on available potassium in soil Potassium is an essential element for crop growth, and the content of available potassium in the soil is an important indicator of potassium supply. Figure 27 It was found that, compared with Con, the application of Bam723 significantly increased the available potassium content in treatments C1, C2, C3, and C4. After applying Bam723, the available potassium content in treatments C1, C2, and C3 increased by 1.32%, 1.40%, and 2.22%, respectively, significantly higher than Con. However, the differences among treatments C1, C2, and C3 were not statistically significant. The results indicate that applying the bacterial solution increases the available potassium content in the soil, and the available potassium content increases with the concentration of the bacterial solution. Compared with Con, the available potassium content in soil reached its maximum under treatment C4, increasing by 3.19%, which was statistically significant. The results show that Bam723 can significantly increase the available potassium content in soil, but the effect is less pronounced at low concentrations.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A type of Bacillus amyloliquefaciens ( Bacillus amyloliquefaciens NECC10723, characterized in that, Its accession number is CGMCC No.36726, and it is deposited at the China General Microbiological Culture Collection Center on November 21, 2025. The deposit address is No.3, No.1 Beichen West Road, Chaoyang District, Beijing.

2. A microbial inoculum containing Bacillus amyloliquefaciens NECC10723 as described in claim 1.

3. The application of Bacillus amyloliquefaciens NECC10723 as described in claim 1.

4. The application of Bacillus amyloliquefaciens NECC10723 according to claim 3, characterized in that, It should include at least one of the following uses: 1) Promotes plant growth; 2) Improve the salt and alkali tolerance of plants; 3) Increase the activity of urease, alkaline phosphatase and / or sucrase in the soil; 4) Increase the content of total nitrogen, available phosphorus and / or available potassium in the soil.

5. The application of Bacillus amyloliquefaciens NECC10723 according to claim 4, characterized in that, Promoting plant growth means increasing plant height, stem diameter, aboveground dry weight, and / or root-to-shoot ratio.

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