Salt-tolerant plant growth-promoting bacteria and application thereof in promoting growth of wheat under salt stress

Abstract

The present application belongs to the field of agricultural microorganism technology, and particularly relates to a salt-tolerant growth-promoting bacterium and application of the bacterium in promoting growth of wheat under salt stress. Bacillus cereus The present application is named as Bacillus cereus, and is referred to as strain STGP1 for short, is preserved in the China General Microbiological Culture Collection Center, and has a preservation number of CGMCC No.50114 and a preservation date of August 19, 2026. The strain STGP1 is isolated from rhizosphere soil of two-colored Limonium gmelinii in Dongying saline-alkali soil through enrichment culture and plate streaking technology. The present application has excellent salt tolerance and multiple growth-promoting characteristics. Potted and field tests prove that the strain STGP1 can significantly promote growth of wheat under salt stress and improve the yield of wheat in saline-alkali soil.

Description

Technical Field

[0001] This invention belongs to the field of agricultural microbial technology, specifically relating to a salt-tolerant growth-promoting bacterium and its application in promoting wheat growth under salt stress. Background Technology

[0002] Soil salinization is a significant limiting factor for global agricultural production and one of the major abiotic stresses affecting food security and sustainable agricultural development. High salinity can lead to osmotic stress, ion toxicity, and oxidative stress in plants, inhibiting root development, reducing nutrient absorption efficiency, and ultimately causing crop yield reduction.

[0003] Plant growth-promoting rhizobacteria (PGPR) have attracted widespread attention because they can promote plant growth and improve plant stress resistance. Numerous studies have shown that PGPR can promote plant growth and improve the plant's adaptability to salt stress through multiple mechanisms such as nitrogen fixation, phosphorus solubilization, potassium solubilization, and secretion of plant hormones. Therefore, the development of microbial agents using salt-tolerant PGPR has become an important research direction for green agriculture in saline-alkali land. Although a large number of salt-tolerant growth-promoting bacteria have been reported, existing strains generally have the following shortcomings: (1) Most existing strains lack a reference genome, and the genetic determinants of their functions such as salt tolerance, phosphorus solubilization, indoleacetic acid (IAA) production, and ACC deaminase production have not been systematically identified, and the salt tolerance and growth-promoting functions lack genetic basis support; (2) Due to the influence of multiple factors such as the colonization ability of strains, competitive exclusion by indigenous microorganisms, and salinity fluctuations, most strains have only completed the verification of salt tolerance or single growth-promoting function under laboratory conditions, and the role of the field environment has been greatly weakened; (3) Due to the multidimensional stress in the saline-alkali environment of the field, the growth-promoting effect of most strains in the saline-alkali environment is not stable enough.

[0004] To address the aforementioned problems, this invention provides a plant growth-promoting bacterium with excellent salt tolerance and plant growth-promoting abilities, and its application in improving crop growth and yield under salt stress conditions. This strain exhibits good salt tolerance and, under salt stress conditions, also possesses multiple plant growth-promoting characteristics such as nitrogen fixation, phosphorus solubilization, potassium solubilization, and indoleacetic acid production. Combined with whole-genome analysis, the genetic basis of its salt tolerance and growth-promoting functions is revealed, achieving a good integration of strain resources, functional analysis, and agricultural applications. It can be widely used for increasing crop yields in saline-alkali lands, developing microbial agents, and promoting green agricultural production in saline-alkali lands. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a salt-tolerant growth-promoting bacterium and its application in promoting wheat growth under salt stress.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a salt-tolerant growth-promoting bacterium, which is classified and named Bacillus cereus. Bacillus cereus (Abbreviated as STGP1), deposited at the China General Microbiological Culture Collection Center, China, Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 50114 and deposit date of August 19, 2026.

[0007] Furthermore, the Bacillus cereus Bacillus cereus It can tolerate a 6% NaCl stress environment and has growth-promoting functions such as nitrogen fixation, phosphorus solubilization, potassium solubilization, and secretion of indoleacetic acid (IAA).

[0008] Furthermore, the genome of Bacillus cereus is a circular chromosome with a length of 5,434,283 bp, a G+C content of 35.9%, and contains an extrachromosomal plasmid of 22 kb in size; genome annotation yielded 5,507 coding genes, 108 tRNA genes, and 42 rRNA genes.

[0009] Secondly, the present invention provides a microbial inoculant containing Bacillus cereus. Bacillus cereus Live bacteria.

[0010] Furthermore, the concentration of viable Bacillus cereus STGP1 in the bacterial agent is not less than 10. 8 CFU / mL.

[0011] Furthermore, the microbial agent is a liquid agent; or a solid agent, wherein the solid agent carrier is at least one of peat moss, humic acid, straw powder, and diatomaceous earth.

[0012] Thirdly, the present invention provides Bacillus cereus. Bacillus cereus Or the application of microbial agents to promote wheat growth under salt stress conditions.

[0013] Furthermore, the application can be any of the following: (1) Improve the plant height, spike length, number of grains per spike, thousand-grain weight, yield per plant and yield per plot of wheat in saline-alkali land; (2) Improve the physiological state of wheat under salt stress: increase the potassium level in wheat leaves + Content, proline content, reducing leaf Na + Content, Na + / K + Ratio, malondialdehyde content, hydrogen peroxide content.

[0014] Furthermore, the application methods include wheat seed soaking and root irrigation with a bacterial suspension during the growth period; the seed soaking involves soaking wheat seeds in OD...600 The value was 0.8 (the viable count was 10). 8 Soak in STGP1 bacterial suspension (CFU / mL) for 6 hours, air dry, and then sow.

[0015] Furthermore, the viable bacteria count of the bacterial suspension applied during root irrigation is 10. 8 CFU / mL; In addition to seed soaking, wheat plants were treated with bacterial suspension drenching twice during their growth period.

[0016] Compared with the prior art, the advantages of the present invention are as follows: This invention provides a rhizosphere growth-promoting bacterium that significantly promotes wheat growth under salt stress. Genome sequence analysis indicates that the strain belongs to the Bacillus cereus taxon. Bacillus cereus, This strain, abbreviated as STGP1, is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 50114, on August 19, 2026. *Bacillus cereus* was isolated from the rhizosphere soil of *Limonium spp.* in saline-alkali land in Dongying County via enrichment culture and streak plating. Phylogenetic analysis of the genome sequence confirmed that strain STGP1 is *Bacillus cereus*. GO and KEGG analyses showed that this strain contains multiple genes and metabolic pathways related to salt tolerance, environmental stress response, and plant growth promotion, providing a genetic basis for its salt tolerance and growth-promoting functions. *Bacillus cereus* exhibits excellent salt tolerance and multiple growth-promoting properties (nitrogen fixation, phosphorus solubilization, potassium solubilization, and IAA production, etc.). Pot and field trials demonstrated that strain STGP1 significantly promotes wheat growth under salt stress and increases wheat yield in saline-alkali land. Attached Figure Description

[0017] The present invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a circled diagram of the genome of Bacillus cereus (strain STGP1). Figure 2 This is the phylogenetic tree of the genome of Bacillus cereus, which is a phylogenetic tree of the genome based on whole genome analysis; Figure 3 GO analysis of the salt tolerance gene in strain STGP1; Figure 4 KEGG analysis of salt tolerance gene-related pathways in strain STGP1; Figure 5Salt tolerance analysis of STGP1 strain on LB agar plates; Figure 6 The purpose of this study was to detect the nitrogen-fixing, phosphorus-solubilizing, and potassium-solubilizing abilities of the STGP1 strain, and to quantitatively analyze its indoleacetic acid (IAA) production. Figure 6 A represents the detection of nitrogen fixation, phosphorus solubilization, and potassium solubilization abilities of strain STGP1. Figure 6 In the diagram, A represents nitrogen (N), P represents phosphorus (P), and K represents potassium (K). Figure 6 B represents the quantitative analysis of indoleacetic acid (IAA) produced by the STGP1 strain; Figure 7 To demonstrate the phenotype of STGP1 strain promoting salt tolerance and growth in wheat under pot conditions, pot experiments proved that STGP1 strain promoted salt tolerance and growth in wheat under pot conditions. Figure 8 The growth rate of the STGP1 strain in promoting salt tolerance and growth in wheat under pot cultivation conditions was measured; among them, Figure 8 Figure A shows the effect of different treatment groups on wheat plant height. Figure 8 Figure B shows the effect of different treatment groups on the root length of wheat. Figure 8 In the middle, C represents the effect of different treatment groups on the fresh weight of wheat; CK is the control group, NaCl is the salt stress treatment group, and STGP1 is the salt stress inoculated strain group. Figure 9 To compare the plant height of wheat at the grain-filling stage under different treatments in a field experiment (Dongying Agricultural High-tech Zone); Figure 10 This study compares the spike length of wheat during the grain-filling stage under different treatments in a field experiment (Dongying Agricultural High-tech Zone). Figure 11 To verify the effects of the STGP1 strain on wheat growth during the grain-filling stage (plant height, fresh weight of stems, dry weight of stems, and number of grains per ear under different treatments) in a field experiment (Dongying Agricultural High-tech Zone); among which, Figure 11 In Figure A, the quantitative determination of wheat plant height during the grain-filling stage under different treatments is presented. Figure 11 Figure B represents the quantitative determination of the fresh weight of wheat stems during the grain-filling stage under different treatments. Figure 11 C represents the quantitative determination of wheat stem dry weight during the grain-filling stage under different treatments. Figure 11 D represents the quantitative determination of the number of grains per ear during the grain-filling stage of wheat under different treatments; Figure 12 This study quantitatively measured the spike length, fresh spike weight, and dry spike weight of wheat during the grain-filling stage under different treatments in a field experiment (Dongying Agricultural High-tech Zone); among them, Figure 12 In section A, the quantitative determination of ear length during the grain-filling stage of wheat under different treatments is presented. Figure 12 Figure B represents the quantitative determination of the fresh weight of wheat spikes during the grain-filling stage under different treatments. Figure 12 C represents the quantitative determination of wheat spike dry weight during the grain-filling stage under different treatments; Figure 13 To verify the effects of the STGP1 strain on physiological indicators (Na2+) during the grain-filling stage of wheat in field experiments. + Content, K + Content, Na + / K + The impact of the analysis (Dongying Agricultural High-tech Zone); among which, Figure 13 A in A is Na + Content analysis; Figure 13 B is K + Content analysis; Figure 13 C is Na + / K + analyze; Figure 14 To verify the effects of the STGP1 strain on physiological indicators (MDA content, proline content, and hydrogen peroxide content) during the grain-filling stage of wheat in a field experiment (Dongying Agricultural High-tech Zone); among them, Figure 14 In the analysis of malondialdehyde (MDA) content, A represents the content of malondialdehyde (MDA). Figure 14 B represents the analysis of proline content. Figure 14 C represents the hydrogen peroxide content analysis; Figure 15 This study compares the plant height of wheat at maturity under different treatments in a field experiment (Dongying Agricultural High-tech Zone). Figure 16 This study compares the spike length at maturity of wheat under different treatments in a field experiment (Dongying Agricultural High-tech Zone). Figure 17 To verify the effect of the STGP1 strain on promoting wheat maturity in a field experiment (Dongying Agricultural High-tech Zone); among which, Figure 17 In section A, the plant height at maturity is compared under different treatments. Figure 17 Figure B shows a comparison of ear length at wheat maturity under different treatments. Figure 17 C represents the quantitative determination of the number of grains per ear at wheat maturity under different treatments; Figure 18 To verify the effect of the STGP1 strain on wheat yield in a field experiment (Dongying Agricultural High-tech Zone), the morphology of wheat grains under different treatments was compared; among them, Figure 18 In the middle, A represents a length comparison. Figure 18 In the middle, B represents a height comparison; Figure 19 To verify the effect of the STGP1 strain on wheat yield in a field experiment (Dongying Agricultural High-tech Zone), the yield per square meter, thousand-grain weight, and yield per plant were quantitatively determined under different treatments; among them, Figure 19 In Figure A, the yield per square meter of wheat under different treatments is quantitatively determined. Figure 19 Figure B represents the quantitative determination of the thousand-grain weight of wheat under different treatments. Figure 19 C represents the quantitative determination of wheat yield per plant under different treatments; Figure 20 To verify the effect of STGP1 strain on wheat growth during the grain-filling stage (wheat plant height during the grain-filling stage under different treatments) in a field experiment (Lijin County, Dongying City). Figure 21 Comparison of spike length during the grain-filling stage of wheat under different treatments in a field experiment; Figure 22 This study involved a field experiment (Lijin County, Dongying City) to quantitatively determine wheat plant height, stem fresh weight, number of grains per ear, and stem dry weight during the grain-filling stage under different treatments. Figure 22 In Figure A, the quantitative determination of wheat plant height during the grain-filling stage under different treatments is presented. Figure 22 Figure B represents the quantitative determination of the fresh weight of wheat stems during the grain-filling stage under different treatments. Figure 22 C represents the quantitative determination of the number of grains per spike during the grain-filling stage of wheat under different treatments. Figure 22 D represents the quantitative determination of wheat stem dry weight during the grain-filling stage under different treatments; Figure 23 This study, conducted in a field experiment (Lijin County, Dongying City), quantitatively measured the fresh weight, dry weight, number of grains per ear, and ear length of wheat during the grain-filling stage under different treatments. Figure 23 Figure A represents the quantitative determination of the fresh weight of wheat spikes during the grain-filling stage under different treatments. Figure 23 Figure B represents the quantitative determination of wheat spike dry weight during the grain-filling stage under different treatments. Figure 23 C represents the quantitative determination of ear length during the grain-filling stage of wheat under different treatments; Figure 24 To verify the effects of the STGP1 strain on physiological indicators (Na2+) during the grain-filling stage of wheat in field experiments. + Content analysis, B:K + Content analysis, C:Na + / K + The impact of the analysis (Lijin County, Dongying City); among which, Figure 24 A in A is Na + Content analysis, Figure 24 B is K + Content analysis, Figure 24 C is Na + / K + analyze; Figure 25 To verify the effects of the STGP1 strain on physiological indicators (MDA content analysis, proline content analysis, and hydrogen peroxide content analysis) during the grain-filling stage of wheat in a field experiment (Lijin County, Dongying City); among them, Figure 25 In the analysis of malondialdehyde (MDA) content, A represents the content of malondialdehyde (MDA). Figure 25 B represents the analysis of proline content. Figure 25 C represents the hydrogen peroxide content analysis; Figure 26To verify the effect of STGP1 strain on wheat growth at maturity (plant height at maturity under different treatments) in field experiments (Lijin County, Dongying City). Figure 27 To verify the effect of STGP1 strain on wheat growth at maturity (ear length at maturity under different treatments) in field experiments (Lijin County, Dongying City). Figure 28 To verify the effects of the STGP1 strain on wheat growth at maturity (plant height, number of grains per ear, and ear length) in a field experiment (Lijin County, Dongying City); among which, Figure 28 In Figure A, the quantitative determination of wheat plant height at maturity under different treatments is presented. Figure 28 B represents the quantitative determination of wheat spike length at maturity under different treatments. Figure 28 C represents the quantitative determination of the number of grains per ear at wheat maturity under different treatments; Figure 29 To verify the effect of the STGP1 strain on wheat yield (wheat grain morphology under different treatments) in a field experiment (Lijin County, Dongying City); among which, Figure 29 Figure A shows a comparison of wheat grain length under different treatments. Figure 29 Figure B shows a comparison of wheat grain height under different treatments; Figure 30 To verify the effect of the STGP1 strain on wheat yield (quantitative determination of wheat yield per square meter, thousand-grain weight, and yield per plant under different treatments) in a field experiment (Dongying Agricultural High-tech Zone), the quantitative determination of wheat yield per square meter, thousand-grain weight, and yield per plant under different treatments was conducted. Figure 30 In Figure A, the yield per square meter of wheat under different treatments is quantitatively determined. Figure 30 Figure B represents the quantitative determination of the thousand-grain weight of wheat under different treatments. Figure 30 C represents the quantitative determination of wheat yield per plant under different treatments. Detailed Implementation

[0019] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention. Unless otherwise specified, the examples are conducted under conventional experimental conditions.

[0020] Reagents: The following reagents are for illustrative purposes only. LB solid medium: 10.0g tryptone, 5.0g yeast extract, 5.0g NaCl, 15.0g agar powder, distilled water to a final volume of 1L, adjust pH to approximately 7.2, autoclave at 121℃ for 20min.

[0021] LB liquid medium: 10.0g tryptone, 5.0g yeast extract, 5.0g NaCl, distilled water to a final volume of 1L, adjust pH to approximately 7.2, autoclave at 121℃ for 20min.

[0022] Example 1: Screening and genomic sequence analysis of strains 1.1 Screening and Preservation of Strains Weigh 10g of fresh rhizosphere soil from the saline-alkali land of Dongying, add it to 90mL of sterile physiological saline, shake thoroughly for 30min, and then dilute to 10000g using a serial dilution method. -1 10 -2 10 -3 10 -4 10 -5 10 -6 and 10 -7 Concentrations were determined by aseptically spreading the culture medium onto LB agar plates, marking them, and incubating at 28°C for 1-3 days. Single colonies were selected based on colony color (milky white or pale yellow), colony diameter (1-3 mm), edge morphology (regular or wavy), surface characteristics (smooth), and transparency (translucent or opaque). These colonies were then purified by streak purification 3-5 times to obtain stable pure cultures. During the screening process, selective enrichment with a high NaCl concentration was used for initial screening. Subsequent screening at different salt concentrations and quantitative analysis of IAA production enabled efficient and targeted acquisition of target strains from complex samples. One bacterium, STGP1, exhibited strong salt tolerance and was selected as the target strain for subsequent functional validation. The morphological characteristics of strain STGP1 were: pale yellow colonies with irregular, frosted glass-like edges, and a rough, opaque surface. The strain STGP1 has been deposited at the China General Microbiological Culture Collection Center (CGMCC), located at Institute of Microbiology, Chinese Academy of Sciences, No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 50114 and deposit date of August 19, 2026.

[0023] 1.2 Genomic Characterization of Strains The strain was sent to BGI Genomics for genome sequencing. Basic characterization analysis was performed on the sequence. The genome consists of a single circular chromosome of 5,434,283 bp in length, with an average G+C content of 35.9%. A total of 5,507 coding genes, 108 tRNAs, and 42 rRNA genes were annotated. The genome circular map is shown below. Figure 1 As shown, the concentric circles from the outside to the inside represent the CDS distribution, COG functional classification, G+C content, and G+C bias on the positive and negative strands, providing crucial information for understanding the strain's genetic potential, genome composition, and replication characteristics. Simultaneously, a 22kb extrachromosomal plasmid was detected. Furthermore, the sequence was submitted to the Type Strain Genome Server website for genomic phylogenetic tree analysis, determining that the strain's closest ancestor is *Bacillus cereus* (…). Figure 2Based on GO analysis, this strain not only possesses single salt tolerance or growth-promoting characteristics, but also a systematic, multi-gene synergistic functional network. GOs related to salt tolerance and growth promotion include: potassium ion transport (GO: 0006813, GO: 0008556, etc.), sodium ion transport (GO: 0006814, GO: 0015655), proline synthesis (GO: 0006561, GO: 0004735), betaine / polyamine synthesis (GO: 0008295, GO: 0006526), ​​and antioxidant activity. Defense (GO:0004096, GO:0004601 and GO:0016209, etc.), stress response and signal transduction (GO:0009651, GO:0006970), tryptophan synthesis (GO:0000162, GO:0004834), nitrogen metabolism (GO:0006807, GO:0006541 and GO:0004359), phosphorus uptake (GO:0006817, GO:0005315) and siderophore synthesis (GO:0019290) Figure 3 KEGG analysis showed that these GO functional categories were enriched in metabolic pathways (such as amino acid metabolism pathways, energy metabolism pathways, and biosynthetic pathways of other secondary metabolites), environmental adaptation pathways (such as membrane transport pathways), and cellular process pathways (such as transport and catabolism pathways). Figure 4 This indicates that the strain possesses the genetic basis for salt tolerance and crop growth promotion.

[0024] The specific 16S rRNA gene sequence (SEQ ID NO: 1) of strain STGP1 is as follows:

[0025] Sequence analysis showed that the 16S rRNA gene sequence of strain STGP1 had 99.67% homology with Bacillus cereus sequences registered in the NCBI database. Further, the STGP1 whole genome sequence was uploaded to the JSpeciesWS website for genome-wide mean nucleotide identity (ANI) analysis, and compared with the genomes of closely related Bacillus cereus strains. The results showed that the ANI values ​​of STGP1 with closely related Bacillus cereus strains BcFL2013, FT9, and 13061 were 91.43%, 91.34%, and 91.34%, respectively, all below the 95% threshold for bacterial species classification.

[0026] Example 2: Identification of salt tolerance and growth-promoting function of the strain 2.1 Salt tolerance test of the strain The STGP1 strain was inoculated into LB medium containing 1%, 2%, 4%, and 6% NaCl, respectively. The strain was able to grow stably in the 6% NaCl medium. The growth status of strain STGP1 on LB solid medium with different salt concentrations is shown in [Figure showing the growth status]. Figure 5 The results showed that as the salt concentration increased, the growth status of the colonies decreased over the same period of time. However, under the hyperosmolar stress of 6% NaCl, the strain could still form plump, uniform, and stable colonies. Although there have been reports on the salt tolerance of Bacillus cereus, such as the strain disclosed in CN115261283B which can still grow at a concentration of 25% NaCl, the strains grow slowly, have poor passage ability, and significantly reduced functional metabolic activity. The advantage of STGP1 in this invention is that it can maintain a highly active proliferation state and complete biological morphology even in a high-salt environment of 6% NaCl. This indicates that STGP1 has an excellent physiological mechanism for tolerating hyperosmolar stress, and is particularly suitable for maintaining high survival rates and functionality in medium-to-high salt applications such as microbial remediation of saline-alkali land.

[0027] 2.2 Detection of nitrogen fixation, phosphorus solubilization, potassium solubilization, and indoleacetic acid (IAA) production by the strain Qualitative detection of nitrogen fixation, phosphorus solubilization, and potassium solubilization, as well as quantitative detection of IAA production, were performed on strain STGP1. Strain STGP1 was cultured in LB liquid medium until it reached the logarithmic growth phase (OD2). 600=Approximately 0.8), take 5 μL of activated bacterial solution and spot it in the center of a modified Assumption solid medium for nitrogen-fixing bacteria (Beijing Kulaibo Technology Co., Ltd.). Incubate at 30℃ inverted for 3-7 days. The strain can grow normally on nitrogen-free medium, forming visible colonies with a clear zone around them. The D / d value is 2.35, indicating that the strain has nitrogen-fixing ability. Take 5 μL of activated bacterial solution and spot it in the center of a phosphate-solubilizing bacteria inorganic phosphorus solid medium (Beijing Kulaibo Technology Co., Ltd.). Incubate at 30℃ inverted for 3-7 days. A clear zone forms around the colonies, with a D / d value of 1.52, indicating that strain STGP1 has the ability to dissolve inorganic phosphorus. Take 5 μL of activated bacterial solution and spot it in the center of a potassium-solubilizing bacteria solid medium (Beijing Kulaibo Technology Co., Ltd.). Incubate at 30℃ inverted for 3-7 days. The colonies appear as oil droplets, preliminarily indicating that strain STGP1 has potassium-solubilizing ability. Figure 6 The results showed that strain STGP1 possesses nitrogen-fixing, inorganic phosphorus-solubilizing, and potassium-solubilizing abilities. The Salkowski colorimetric method was used to detect the strain's IAA production capacity. A series of IAA standard solutions with known concentrations (0, 5, 10, 20, 50 mg / L) were prepared. Each concentration of standard solution was mixed with the Salkowski colorimetric solution in the same proportion as the sample, and the absorbance was measured at 530 nm. A standard curve was plotted with IAA concentration on the x-axis and absorbance at 530 nm on the y-axis. Strain STGP1 was cultured in LB liquid medium, and samples were taken at different time points. The test bacterial solution was reacted with the Salkowski reagent following the same procedure as in the standard curve preparation, and the OD was measured. 530 The measured OD 530 Substituting the values ​​into the standard curve equation, the IAA concentration in the sample can be calculated. The IAA yield of the strain after 48 hours was 22.06 mg / L. Figure 6 The results of the study (B) demonstrated the dynamic changes in IAA production by strain STGP1. Although there are reports on the nitrogen-fixing, phosphorus-solubilizing, potassium-solubilizing, and IAA-producing abilities of Bacillus cereus, these strains tolerate NaCl concentrations of 0-2%, lower than STGP1's ability to grow in a hypertonic environment of 6% NaCl. Other Bacillus cereus strains reported in the literature exhibit salt tolerance and phosphorus-solubilizing abilities, but none have explicitly demonstrated nitrogen fixation, potassium-solubilizing, or IAA-producing capabilities. Bacillus(Strains isolated from a salt-marshland area under salinity stress). Literature reports that Bacillus cereus YL6 possesses phosphate-solubilizing and IAA-producing abilities, but does not explicitly report its nitrogen-fixing and potassium-solubilizing abilities. (Root colonization and growth promotion of soybean, wheat, and Chinese cabbage by...) Bacillus cereus YL6). Literature reports that Bacillus cereus YN917 can produce IAA and has mineral phosphorus solubilizing ability; its nitrogen fixation ability has not been reported as a primary function, and the strain's potassium solubilizing ability is unclear. (Efficacy of Plant Growth-Promoting Bacteria) Bacillus cereus YN917 for Biocontrol of Rice Blast).

[0028] Example 3: Identification of the ability of the strain to alleviate wheat salt stress under pot cultivation conditions 3.1 Disinfection and germination of wheat seeds Select plump wheat seeds of uniform size. Disinfect the surface of the seeds with 2% sodium hypochlorite for 10 minutes, then rinse them three times with sterile water. Soak the seeds in sterile water in a petri dish and vernalize them at 4℃ for 48 hours. Then place them in a 9*9 cm black square pot (100% vermiculite) for germination. Transplant the seeds after about 3-4 days of germination, selecting those with uniform germination height.

[0029] 3.2 Detection of the strain's salt tolerance and growth-promoting properties in wheat Selected Fengmai No. 1 wheat seedlings were transplanted into 9*9cm pots containing nutrient soil (a 1:1 mass ratio of substrate and vermiculite), with 3 seedlings per pot and 6 pots per treatment. Three treatment groups were established: a control group (CK), a salt stress treatment group (NaCl), and a salt stress inoculated strain group (NaCl+STGP1). The CK group was sown and watered. The NaCl group was treated with a 400mg NaCl solution for root drenching the day after transplanting, with 100mL per pot every 7 days. The NaCl+STGP1 group was treated with a 400mg NaCl solution for root drenching the day after transplanting, with 100mL per pot every 7 days. Simultaneously, the STGP1 strain was cultured in LB broth, and a bacterial suspension (103 viable cells) was prepared. 8The root drenching treatment was performed with 60 mL of the strain per pot, applied every 7 days. Three weeks after transplanting, agronomic traits such as plant height, root length, and fresh weight of wheat in different groups were measured. The results showed that compared with the salt stress treatment group, the salt stress treatment group treated with the STGP1 strain significantly increased the plant height, root length, and fresh weight of wheat, indicating that the STGP1 strain treatment can improve the salt tolerance and growth ability of wheat under salt stress. Figure 7-8 ).

[0030] Example 4: Field validation of the salt tolerance and growth-promoting properties of strain STGP1 in wheat. 4.1 Disinfection and soaking of wheat seeds Select plump, uniformly sized wheat seeds. Disinfect the seeds with 2% sodium hypochlorite for 10 minutes, then rinse three times with sterile water. Soak the disinfected wheat seeds in a bacterial suspension (OD value adjusted to approximately 0.8) for 6 hours, then air-dry them in a cool, dry place. Plant the dried wheat seeds in two areas of the Dongying saline-alkali land (Dongying Agricultural High-tech Zone and Lijin County). Each area was divided into two treatment groups: a control group (CK) and an STGP1 treatment group. Each treatment group consisted of three plots, each plot measuring 1 m². 2 .

[0031] 4.2 Root irrigation with STGP1 bacterial suspension Preparation of STGP1 bacterial suspension (10 viable cells) 8 / mL), each plot was irrigated with 5L of bacterial suspension, while the control group was irrigated with the same volume of water. Apart from one time when the seeds were soaked in bacterial suspension, the wheat was irrigated with bacterial suspension twice during its growth period.

[0032] 4.3 Detection of the strain's salt tolerance and growth-promoting properties in wheat The plant height, stem fresh weight, ear length, single ear fresh weight, and spikelet number of wheat during the grain-filling stage were statistically analyzed. Physiological indicators during the grain-filling stage were also measured, as well as plant height, ear length, number of grains per ear, yield per plant, thousand-grain weight, and plot yield at maturity. Compared with the control group, STGP1 inoculant treatment significantly increased plant height, stem fresh weight, ear length, single ear fresh weight, and spikelet number of Fengmai 1 wheat during the grain-filling stage in Dongying Agricultural High-tech Zone. p <0.05), the increases were 5.49%, 35.6%, 17.31%, 32.22%, and 17.42%, respectively. Figure 9-12 ); and Fengmai No. 1 leaves K during the grouting period + The content of proline and sodium was significantly higher in the control group compared to the control group, while sodium content was lower. + Na + / K + The contents of malondialdehyde and hydrogen peroxide all decreased. Figure 13-14Compared with the CK group, the STGP1 inoculant treatment group showed significantly increased plant height, spike length, and number of grains per spike at maturity. Figure 15-17 Furthermore, the yield per plant, thousand-seed weight, and plot yield were significantly higher than those of the control group, with the thousand-seed weight increasing by 36.26% and the plot yield increasing by 14.60%. Figure 18-19 ).

[0033] The plant height, stem fresh weight, ear length, single ear fresh weight, and spikelet number of wheat in Lijin County, Dongying City, were statistically analyzed during the grain-filling stage, as well as the plant height, ear length, number of grains per ear, yield per plant, thousand-grain weight, and plot yield at the maturity stage. Compared with the control group, STGP1 inoculant treatment significantly increased the plant height, stem fresh weight, ear length, single ear fresh weight, and spikelet number of Fengmai No. 1 wheat in Lijin County, Dongying City, with increases of 13.89%, 25.25%, 5.28%, 23.88%, and 21.26%, respectively. Figure 20-23 ); and Fengmai No. 1 leaves K during the grouting period + The content of proline and sodium was significantly higher in the control group compared to the control group, while sodium content was lower. + Na + / K + The contents of malondialdehyde and hydrogen peroxide all decreased. Figure 24-25 Compared with the CK group, the STGP1 inoculant treatment group showed significantly increased plant height, spike length, and number of grains per spike at maturity. Figure 26-28 The yield per plant, thousand-grain weight, and plot yield were also significantly higher than those of the control group, with the thousand-grain weight increasing by 22.05% and the plot yield increasing by 44.31%. Figures 29-30 ).

Claims

1. A salt-tolerant growth-promoting bacterium, characterized in that, The salt-tolerant growth-promoting bacteria were classified and named Bacillus cereus. Bacillus cereus It is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 50114 and deposit date of August 19, 2026.

2. The salt-tolerant growth-promoting bacteria according to claim 1, characterized in that, The Bacillus cereus Bacillus cereus It can tolerate a 6% NaCl stress environment and has growth-promoting functions such as nitrogen fixation, phosphorus solubilization, potassium solubilization, and secretion of indoleacetic acid (IAA).

3. The salt-tolerant growth-promoting bacteria according to claim 1, characterized in that, The Bacillus cereus Bacillus cereus The genome is a circular chromosome with a length of 5,434,283 bp, a G+C content of 35.9%, and contains an extrachromosomal plasmid of 22 kb. Genome annotation yielded 5,507 coding genes, 108 tRNA genes, and 42 rRNA genes.

4. A microbial inoculant, characterized in that, The microbial agent contains Bacillus cereus as described in any one of claims 1-3. Bacillus cereus Live bacteria.

5. The microbial agent according to claim 4, characterized in that, Bacillus cereus in microbial inoculants Bacillus cereus The concentration of live bacteria is not less than 10. 8 CFU / mL.

6. The microbial agent according to claim 5, characterized in that, The microbial agent is a liquid agent or a solid agent; the carrier of the solid agent is at least one of peat moss, humic acid, straw powder, and diatomaceous earth.

7. The Bacillus cereus according to any one of claims 1-3 Bacillus cereus Or the application of the microbial agent according to any one of claims 4-5 to promote wheat growth under salt stress conditions.

8. The Bacillus cereus according to claim 7 Bacillus cereus The application of microbial agents to promote wheat growth under salt stress conditions is characterized by, The application is any one of the following: (1) Improve the plant height, spike length, number of grains per spike, thousand-grain weight, yield per plant and yield per plot of wheat in saline-alkali land; (2) Increase the potassium content of wheat leaves + Content, proline content, reducing leaf Na + Content, Na + / K + Ratio, malondialdehyde content, hydrogen peroxide content.

9. The Bacillus cereus according to claim 7 Bacillus cereus The application of microbial agents to promote wheat growth under salt stress conditions is characterized by, Application methods include wheat seed soaking and root irrigation with bacterial suspension during the growth period; the seed soaking refers to soaking wheat seeds in OD... 600 Bacillus cereus with a concentration of 0.8 Bacillus cereus Soak the bacteria in the bacterial suspension for 6 hours, then air dry before sowing.

10. The Bacillus cereus according to claim 9 Bacillus cereus The application of microbial agents to promote wheat growth under salt stress conditions is characterized by, In addition to seed soaking, wheat should undergo two additional root irrigation treatments with bacterial suspension during its growing season.

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