Desert plant endophyte, microbial agent and application

Abstract

The invention relates to the technical field of microorganisms, in particular to a desert plant endophyte, a microbial agent and application, the desert plant endophyte is Pristeria aryabhattai HB-4 and is preserved in the China Center for Type Culture Collection on November 17, 2025, and the preservation number of the desert plant endophyte is CGMCC No.36665. The invention further relates to a method for preparing the desert plant endophyte. The strain can efficiently produce indoleacetic acid and has remarkable growth promoting and stress resistance functions. After the strain is inoculated, the fresh weight, the dry weight, the stem length, the chlorophyll content and the catalase activity of wheat are remarkably improved, and the malondialdehyde content is reduced. The invention further provides a microbial agent containing the strain and application of the microbial agent in the aspects of promoting plant growth and improving stress resistance, the microbial agent is particularly suitable for cultivation of crops such as wheat in drought and barren environments, and a new strain resource is provided for development of agricultural microbial preparations.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, specifically to an endophytic bacterium of desert plants, a microbial agent, and its application. Background Technology

[0002] Located in the heart of the continent, far from the ocean, Northwest China experiences sparse rainfall and a fragile ecosystem, making it a typical arid to semi-arid region. Vegetation in this area is sparse and slow-growing, with most of the land covered by desert and Gobi. Desert plants such as Haloxylon ammodendron and Caragana korshinskii have evolved unique stress-resistance physiological mechanisms, enabling them to adapt to extreme environments such as high temperatures, drought, salinity, and barrenness, playing a vital role in windbreak and sand fixation, soil improvement, and biodiversity maintenance.

[0003] As important carriers of plant genetic information and the co-evolution of microbial communities, seed endophytic fungi can achieve intergenerational inheritance through vertical dispersal mechanisms, and the stability of their community composition plays a crucial role in the adaptive evolution of host plants. Currently, research on desert plant endophytic fungi largely focuses on community diversity analysis, but the screening and application of endophytic strains with highly efficient growth-promoting functions remain insufficient. While some endophytic strains with growth-promoting potential have been isolated using existing technologies, most strains have limited growth-promoting abilities, especially in the production of indoleacetic acid (IAA), which is generally low, making it difficult to achieve significant effects in actual agricultural production. Furthermore, the overall performance of existing strains in promoting crop growth and improving physiological indicators is often not outstanding, and there is a lack of highly efficient strains that can simultaneously improve crop biomass, chlorophyll content, and stress resistance.

[0004] Therefore, developing endophytic strains of desert plants with high growth-promoting capabilities can not only provide a material basis for screening functional strains with stable genetic traits, but also provide technical support for building agricultural microbial germplasm resource banks and promoting sustainable agricultural development. Summary of the Invention

[0005] To address the above problems, this invention provides an endophytic fungus for desert plants, a microbial agent, and its application.

[0006] This invention is achieved through the following technical solution: An endophytic fungus of desert plants, wherein the endophytic fungus of desert plants is *Priscilla argentea* ( Priestia aryabhattai HB-4 ， It was deposited at the China Center for Type Culture Collection on November 17, 2025, with accession number CGMCC No. 36665.

[0007] A microbial inoculant, wherein the microbial inoculant is obtained by inoculating Priestella HB-4 as described in claim 1 into a culture medium and then culturing it.

[0008] Preferably, the specific preparation method includes the following steps: After inoculating Priestella HB-4 onto LB liquid medium and culturing, the bacterial culture was collected and centrifuged to obtain the supernatant, which is the microbial inoculum.

[0009] The application of the aforementioned desert plant endophytic bacteria or the aforementioned microbial agents in promoting plant growth.

[0010] Preferably, the promotion of plant growth is manifested as an increase in plant stem length, fresh weight, and dry weight.

[0011] The application of the desert plant endophytic bacteria or the microbial agent in the production of indoleacetic acid.

[0012] The application of the desert plant endophytic bacteria or the microbial agent in increasing plant chlorophyll content, reducing plant malondialdehyde content, and / or increasing plant catalase activity.

[0013] Preferably, the plant is wheat.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention provides an endophytic strain of desert plants with growth-promoting effects, wherein the strain is *Priscilla argentea* (…). Priestia aryabhattai HB-4 ， It was deposited at the China Center for Type Culture Collection on November 17, 2025, with accession number CGMCC No. 36665.

[0015] (1) High IAA production capacity: After being cultured in LB medium containing L-tryptophan, strain HB-4 produced significantly more IAA than other known growth-promoting strains, reaching 18.48 μg·mL. -1 This highly efficient IAA synthesis capability gives it a unique advantage in promoting plant growth, far exceeding that of conventional strains.

[0016] (2) Significantly promotes crop growth: Through pot experiments, it was verified that after inoculation with strain HB-4, the fresh weight and dry weight of wheat increased significantly by 120.33% and 69.19%, respectively, and the stem length increased significantly by 29.20%. This indicates that HB-4 can effectively enhance the bioaccumulation and morphological development of crops.

[0017] (3) Improvement of physiological indicators: After inoculation with HB-4, the total chlorophyll content of wheat leaves increased by 36.02%, the malondialdehyde content decreased by 26.33%, the catalase activity increased by 98.02%, and the proline content increased by 26.47%. These results indicate that HB-4 can not only promote photosynthesis, but also enhance the plant's stress resistance, such as reducing membrane lipid peroxidation damage and improving antioxidant capacity.

[0018] (4) Comprehensive growth-promoting potential: HB-4 did not show positive results in functional screening such as nitrogen fixation, phosphorus solubilization and iron production, but its efficient IAA production and multiple physiological regulation capabilities make it a specific and efficient growth-promoting strain, suitable for promotion and application in barren and stressful soils.

[0019] Information on the preservation of biological materials Argentinella precatorius ( Priestia aryabhattai HB-4, classified as *Priscilla auriculata*. Priestia aryabhattai It was deposited on November 17, 2025 at the China Center for Type Culture Collection (CGMCC) with accession number CGMCC No. 36665, located at Institute of Microbiology, Chinese Academy of Sciences, No. 3, Beichen West Road, Chaoyang District, Beijing. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The images show electrophoresis diagrams of 16S rRNA from endophytic bacteria in Haloxylon ammodendron and Caragana korshinskii seeds, as presented in this invention. Specifically, a) shows the electrophoresis diagram of 16S rRNA from endophytic bacteria in Haloxylon ammodendron seeds, with strains HB-1 to HB-13 listed from left to right; b) shows the electrophoresis diagram of 16S rRNA from endophytic bacteria in Caragana korshinskii seeds, with strains HSA-1 to HSA-9 listed from left to right. Note: M is a 2000 bp marker.

[0022] Figure 2 This is a diagram showing the number of endophytic bacteria in each genera of bacteria in this invention.

[0023] Figure 3 This is a diagram showing the screening results of IAA-producing functional strains for this invention.

[0024] Figure 4 The diagram shows the effect of the inoculated strain of the present invention on wheat growth; where a) is a comparison diagram of the overall wheat plant; and b) is a comparison diagram of growth in pots.

[0025] Figure 5 The effects of HB-4 of the present invention on wheat fresh weight, dry weight, stem length and root length are shown in Figure 1. a) shows the effect of HB-4 on wheat fresh weight and dry weight; b) shows the effect of HB-4 on wheat stem length and root length. Note: fw represents fresh weight, dw represents dry weight, sl represents stem length, and rl represents root length.

[0026] Figure 6The following are graphs showing the effects of HB-4 of the present invention on wheat physiological indicators: Figure a) shows the effect on wheat chlorophyll content; Figure b) shows the effect on malondialdehyde (MDA) content; Figure c) shows the effect on catalase (CAT); Figure d) shows the effect on peroxidase (POD) activity; and Figure e) shows the effect on proline content. Detailed Implementation

[0027] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0029] The beneficial effects of the present invention will be illustrated below through specific embodiments.

[0030] Example 1 1.1 Materials and Methods 1.1.1 Experimental Materials All test materials were collected from Minqin County, Wuwei City, Gansu Province (102°58'E, 38°35'N).

[0031] Haloxylon ammodendron (CA Mey.) Bunge) and flower stick ( Hedysarumscoparium Collect 500 g of seeds and store them in a refrigerator at 4℃ for a long time.

[0032] The experimental reagents are shown in Table 1.

[0033] Table 1 Experimental Reagents Note: "—" indicates that this item is not available.

[0034] In this embodiment, the culture media used to isolate and culture endophytic fungi from Haloxylon ammodendron and Caragana korshinskii seeds are shown in Tables 2 to 8.

[0035] Table 2 LB medium Weigh the culture medium, boil it to a final volume, adjust the pH to 7.0, and autoclave at 121℃ for 20 minutes before use.

[0036] Table 3 R2A culture medium Weigh the culture medium, boil it to a final volume, adjust the pH to 7.2, and autoclave at 121℃ for 20 minutes before use.

[0037] Table 4 NA medium Weigh the culture medium, boil it, and bring it to a final volume. Adjust the pH to 7.3 ± 0.2, then autoclave at 121°C for 20 minutes before use.

[0038] Table 5 Oat Culture Medium Weigh the culture medium, boil it, and bring it to a final volume. Adjust the pH to 6.0±0.2, then autoclave at 121℃ for 20 minutes before use.

[0039] Table 6. Gao's No. 1 Culture Medium Weigh the culture medium, boil it, adjust the pH to 7.3, and autoclave it at 121℃ for 20 minutes before use.

[0040] Table 7 TSA culture medium Weigh the culture medium, boil it, adjust the pH to 7.3, and autoclave it at 121℃ for 20 minutes before use.

[0041] Table 8 PDA culture medium Weigh the culture medium, boil it, adjust the pH to 5.6, and autoclave it at 121℃ for 20 minutes before use.

[0042] The experimental apparatus is shown in Table 9.

[0043] Table 9 Main Instruments 1.1.2 Isolation, purification and preservation of endophytic bacteria (1) Seed surface disinfection.

[0044] (2) Seed embedding method: Seeds that have been verified by surface disinfection are placed on sterile filter paper to absorb surface moisture, and morphologically intact seeds are evenly distributed on the culture medium (9 seeds per dish), and incubated upside down at 28°C for 7 days.

[0045] (3) Tissue homogenization method: The remaining seeds were placed in a sterile mortar, 5 mL of sterile water was added and the mixture was ground into a homogenate. 1 mL of the supernatant was taken and diluted with 10 mL of water. -1 10 -2 and 10 -3 Spread onto the culture medium and incubate upside down at 28°C for 7 days.

[0046] (4) Strain purification and preservation: After colonies grow on the plate, select colonies of different shapes, colors and sizes and streak them 4 times on the LB plate until all single colonies on the plate are completely identical. The purified single colonies are cultured overnight in LB liquid medium (180 rpm, 28℃), mixed with an equal volume of 50% glycerol, and frozen in an ultra-low temperature freezer at -80℃ for subsequent experiments.

[0047] 1.1.3 Endophytic bacterial DNA extraction and PCR amplification (1) DNA extraction: The endophytic bacteria preserved in the previous experiment were activated on LB plates, and single colonies were picked and cultured overnight in LB liquid medium (180 rpm, 28℃). 1 mL of bacterial culture was transferred to a 1.5 mL sterile centrifuge tube and centrifuged at 12000g for 2 min to collect the bacterial cells. Bacterial DNA was extracted using a bacterial DNA extraction kit. The DNA product was analyzed by 1.0% agarose gel electrophoresis to determine the DNA fragment size and product quality.

[0048] (2) PCR amplification: Universal primers 27F (5'-AGAGTTTGATCCTGGCTCAG-3') and 1492R (5'-TACGGCTACCTTGTTACGACTT-3') were used, and the PCR reaction was completed according to the instructions of the 2×Rapid Taq Master Mix (20 μL). After amplification, 5 μL of the product was tested by 1% agarose gel electrophoresis. After passing the test, the product was sent to Suzhou Genewise Biotechnology Co., Ltd. in Jiangsu Province for bidirectional sequencing using the Sanger sequencing method with primers 27F and 1492R. The PCR reaction system is shown in Table 10.

[0049] Table 10 PCR Reaction System (8) Sequence analysis: The obtained sequences were aligned to the NCBI database (https: / / www.ncbi.nlm.nih.gov / ) using BLAST.

[0050] 1.1.4 Data Analysis All sequences were saved in FASTA format, aligned in NCBI, and uploaded to GENBANK to obtain accession numbers.

[0051] 1.2 Results and Analysis 1.2.1 Isolation of endophytic bacteria from seeds 1.2.1.1 PCR amplification results of endophytic bacteria After PCR amplification, the results were analyzed by 1% agarose gel electrophoresis (1×TAE buffer, 105V, 30min). Figure 1 Electrophoresis images of 16S rRNA from endophytic bacteria in seeds of Haloxylon ammodendron (A) and Caragana korshinskii (B) are shown. The PCR amplification bands were clear, without tails or diffuse bands. The size of the target band was consistent with the expected length of the 16S rRNA gene (≈1500 bp), and the band brightness was comparable to that of a 100 ng / μL marker. The amplification products met the sequencing quality requirements and could be used for subsequent sequencing.

[0052] 1.2.1.2 Identification of 16S rRNA in Endophytic Bacteria: Identification Results Thirteen and nine endophytic bacteria were isolated from Haloxylon ammodendron and Caragana korshinskii, respectively. The sequences of all strains were compared using the BLAST function in NCBI, and highly similar strains were selected for display. All strain sequences were then uploaded to GenBank to obtain the corresponding accession numbers (see Table 11 for details). Figure 2 The results showed that Bacillus spp. ( Bacillus A total of 15 strains were identified, accounting for 68.18%; *Priscilla* spp. Priestia A total of 3 plants were identified, accounting for 13.64%; Peribacillus 1 strain, genus Coccella ( Kocuria ), Bacillus subtilis ( Terribacillus ) and Bacillus spp. ( Paenibacillus One strain each of the two species was isolated, accounting for 4.55%. Among them, Bacillus was the dominant genus among the isolated strains.

[0053] Table 11. Identification of 16S rRNA gene sequence similarity of endophytic bacteria from seeds of Haloxylon ammodendron and Caragana korshinskii. This embodiment uses traditional isolation and culture techniques to obtain 22 endophytic bacteria belonging to 6 genera from the seeds of Haloxylon ammodendron and Caragana korshinskii, such as... Figure 2 As shown, they are Bacillus genus ( Bacillus ,), Priestella spp. ( Priestia ), Peribacillus genus Cochlea Kocuria ), Bacillus terrestris ( Terribacillus ) and Bacillus spp. ( Paenibacillus The dominant genus was Bacillus (68.18%, 15 / 22).

[0054] Example 2 Screening and functional validation of growth-promoting bacteria.

[0055] 2.1 Materials and Methods 2.1.1 Experimental Materials All bacterial strains used in the experiment were derived from endophytic bacteria previously isolated from the seeds of Haloxylon ammodendron and Caragana korshinskii. The wheat variety used in the experiment was Jimai 22.

[0056] The main reagents and preparation methods are shown in Table 12.

[0057] Table 12 Experimental Reagents Note: "—" indicates that this item is not available.

[0058] (1) Preparation of Salkowski reagent: 31 mL of 0.5 mol / L FeCl3, 30 mL of concentrated sulfuric acid, and distilled water to a final volume of 50 mL.

[0059] (2) Preparation of 0.6% thiobarbituric acid (TBA): Dissolve a small amount of 1 mol / L NaOH and then make up to volume with 10% TCA.

[0060] (9) Preparation of acidic ninhydrin: Weigh 0.5 g of ninhydrin, add 12 mL of glacial acetic acid and 8 mL of 6 mol / L phosphoric acid, and heat at 60℃ to dissolve.

[0061] culture medium The culture media and formulations required for the functional strain screening experiment are shown in Tables 13 to 16.

[0062] Table 13 NBRIP Culture Medium Weigh the culture medium, boil it, adjust the pH to 7.0, and autoclave it at 121 ℃ for 20 min before use.

[0063] Table 14 Pikovskava Inorganic Phosphorus Medium Weigh the culture medium, boil it, adjust the pH to 7.0, and autoclave it at 121 ℃ for 20 min before use.

[0064] Table 15 CAS Culture Medium Weigh the culture medium, boil it, adjust the pH to 6.8, and autoclave it at 121 ℃ for 20 min before use.

[0065] Table 16 Ashbby Nitrogen-Free Medium Weigh the culture medium, boil it, adjust the pH to 7.2, and autoclave it at 121 ℃ for 20 min before use.

[0066] Main instruments The main instruments required for the experiment are shown in Table 17.

[0067] Table 17 Main Instruments and Equipment 2.1.2 Determination of reproductive function 2.1.2.1 IAA Production Capacity Measurement (1) Qualitative determination After activating the previously preserved bacterial strains on LB medium, single colonies were picked and inoculated into LB liquid medium containing 1 g / L L-tryptophan and cultured for 5 days (180 rpm, 28°C). ). Take 1 Centrifuge the bacterial culture (12000 g, 2 min) and collect the supernatant. For detection, take 100 μL of the supernatant and react it with an equal volume of Salkowski colorimetric solution in a clear 96-well plate in the dark for 30 min. Perform three technical replicates for each strain, and set up a culture medium without inoculation of the strain as a negative control. Compared with the control, a red color in the solution indicates a positive result, indicating that the strain has the ability to produce IAA; the redder the color, the stronger the IAA production ability.

[0068] (2) Quantitative determination Select strains that showed positive qualitative test results, centrifuge the bacterial culture (12000 g, 2 min), and collect the supernatant. Mix 1 mL of the supernatant with an equal volume of Salkowski colorimetric solution and react in the dark for 30 min. Analyze the reaction at OD0.05. 530 Absorbance was measured at the specified location, with three technical replicates for each strain. The culture medium used to inoculate the strain was mixed with Salkowski solution and zeroed.

[0069] (3) Standard Curve Prepare a 1 mg / mL stock solution using IAA standard, and serially dilute it. [Odolatry] 530 Measure the absorbance at the specified point, record the data, and plot the standard curve: y = 0.0251x + 0.0997, R0 2 =0.9971.

[0070] 2.1.2.2 Nitrogen fixation capacity determination The strains were cultured overnight (12 h) in LB liquid medium and streaked onto Ashbby nitrogen-free medium, with each strain being replicated three times. The ability of the strains to grow on Ashbby nitrogen-free medium indicates nitrogen-fixing capability.

[0071] 2.1.2.3 Determination of phosphorus solubility The strains were cultured overnight (12 h) in LB liquid medium. 10 μL of the bacterial culture was then inoculated onto PVK and NBRIP media, with each strain tested in triplicate. After 7 days of incubation at 28 ℃, the presence of a transparent phosphate-solubilizing zone was observed, and the diameter of the phosphate-solubilizing zone was measured precisely using calipers. D With colony diameter d ,use D / d The ratio measures the phosphorus-solubilizing ability of a strain; the higher the ratio, the stronger the phosphorus-solubilizing ability.

[0072] 2.1.2.4 Determination of Iron Production Capacity After activation on LB medium, single colonies were picked and transferred to CAS medium, with three replicates for each strain. The cultures were incubated at 28 °C for 7 days, and the presence of an orange-yellow halo was observed. The appearance of an orange-yellow halo indicated that the strain had the ability to produce siderophores.

[0073] 2.1.2.5 Verification of reproductive function After disinfection, wheat seeds that germinated for 4 days in sterile vermiculite (sterilized three times at 121 ℃ for 45 min) with uniform growth were selected and transplanted into flowerpots, 10 plants per pot. The experimental group consisted of wheat plants inoculated with HB-4 bacterial solution; the control group (CK) consisted of wheat plants not inoculated with the strain. HB-4 strain was inoculated into LB liquid medium and cultured with shaking at 28 ℃ and 180 rpm for 12 h. The bacterial solution was then centrifuged, and the supernatant obtained was collected as the HB-4 bacterial solution.

[0074] (1) Stem length and root length: After wheat harvest, select 3 plants and measure the stem length and root length with a ruler with an accuracy of 1 mm.

[0075] (2) Fresh weight: Dig out the seedlings, carefully clean the soil, wash the seedlings with tap water to remove the attached substances, vermiculite and nutrient soil, and then use filter paper to absorb the surface moisture and weigh them.

[0076] (3) Dry weight: After drying at 60 ℃ for 72 h, weigh the dry weight. The dry weight is based on the biomass (i.e. the dry weight of the whole).

[0077] 2.1.2.6 Measurement of physiological indicators In the physiological index measurement, the experimental group consisted of wheat leaves or tissues inoculated with HB-4 bacterial solution; the control group (CK) consisted of wheat leaves or tissues without bacterial inoculation. HB-4 strain was inoculated into LB liquid medium and cultured with shaking at 28℃ and 180 rpm for 12 h. The bacterial solution was then centrifuged, and the supernatant obtained was the HB-4 bacterial solution.

[0078] (1) Determination of total chlorophyll content Chlorophyll content was determined using an ethanol extraction method. 0.1 g of fresh wheat leaves were washed, dried, and placed in a mortar. 0.1 g of silica sand (SiO2), 0.05 g of calcium carbonate (CaCO3), and 3 mL of 95% ethanol were added. The mixture was ground into a homogenate until the tissue turned white and allowed to stand for 3 minutes. The homogenate was transferred to a 10 mL centrifuge tube and centrifuged at 4000 g for 10 minutes. The supernatant was collected and diluted to a 25 mL amber volumetric flask with 95% ethanol. (OD...) 645 OD 649 Absorbance was measured at the specified concentration. Each treatment was repeated three times. Chlorophyll concentration (mg / L) was calculated using the following formula:

[0079] .

[0080] .

[0081] Chlorophyll content is calculated using the following formula .

[0082] Where: c: chlorophyll concentration, V: extract volume, D: dilution factor, m: sample fresh weight.

[0083] (2) Determination of malondialdehyde content The malondialdehyde content was determined using the thiobarbituric acid method.

[0084] The specific procedures are as follows: Weigh 0.1 g of wheat leaves, wash them, absorb the water, cut them into small pieces, and place them in a 2 mL centrifuge tube. Repeat this process three times for each sample. Add grinding beads and 1 mL of 10% TCA (total dissolved in water), and grind into a homogenate (4 ℃, 50 Hz, 5 min). Transfer the homogenate to a 10 mL centrifuge tube, add 8 mL of TCA, centrifuge at 4000 g for 10 min, and collect 2 mL of the supernatant. Mix this with 2 mL of 0.6% TBA (total dissolved in water) to prepare the test solution. Simultaneously, set up a reagent blank control by replacing the supernatant with 2 mL of distilled water and mixing it with an equal volume of 0.6% TBA (total dissolved in water). Boil the test solution and the blank control together in a water bath for 15 min. After boiling, immediately cool in an ice bath and centrifuge at 4000 g for 10 min. Zero the instrument using the blank control solution and measure the absorbance of the test solution at 450 nm and 532 nm. Repeat this process three times for each treatment.

[0085] Malondialdehyde concentration is calculated using the following formula: .

[0086] .

[0087] Where: c: MDA concentration, V: extract volume, D: dilution factor, W: sample mass.

[0088] (3) Assay of catalase (CAT) activity The catalase (CAT) activity assay was performed according to Solarbio's "Catalase (CAT) Activity Assay Kit Instruction Manual".

[0089] Weigh 0.1 g of fresh wheat leaves, wash and dry them, then chop them and place them in a 2 mL centrifuge tube. Add grinding beads and 1 mL of extraction solution, and grind into a homogenate. Centrifuge at 8000 g, 4 ℃ for 10 min, collect the supernatant, and place it on ice for analysis. Add 10 μL of sample and 190 μL of working solution to a microquartz cuvette, mix immediately, and start timing. Record the initial absorbance value A1 at 240 nm and the absorbance value A2 after 1 min. Calculate ΔA = A1 - A2. Each treatment was repeated three times.

[0090] Catalase (CAT) activity is calculated using the following formula: .

[0091] W: Sample quality.

[0092] (4) Peroxidase (POD) activity assay Peroxidase (POD) activity was measured according to Solarbio's "Peroxidase (POD) Activity Assay Kit Instructions".

[0093] Weigh 0.1g of fresh wheat leaves, wash and dry them, then chop them and place them in a 2mL centrifuge tube. Add grinding beads and 1mL of extract, and grind into a homogenate. Centrifuge at 8000g, 4℃ for 10min, collect the supernatant, and place it on ice for testing. Add reagents according to Table 18, sequentially adding reagents to 1mL glass cuvettes. Each treatment is repeated 3 times.

[0094] Table 18 Sample Addition Table for Peroxidase (POD) Activity Assay Mix immediately and start timing. Record the absorbance value A1 at 470 nm for 30 s and the absorbance value A2 after 1 min 30 s. Calculate ΔA = A2 - A1. Reagents 1, 2, and 3 are described in Solarbio's "Peroxidase (POD) Activity Assay Kit Instruction Manual".

[0095] POD activity is calculated using the following formula: .

[0096] W: Sample quality.

[0097] (5) Determination of proline content The proline content was determined using the sulfosalicylic acid method.

[0098] Weigh 0.1 g of wheat leaves, wash them, pat dry, chop them, and place them in a 2 mL centrifuge tube. Add grinding beads and 1 mL of 3% sulfosalicylic acid solution, and grind into a homogenate. Incubate at 90 ℃ for 10 min, then centrifuge at 4000 g for 10 min. Take 500 μL of the supernatant, 500 μL of glacial acetic acid, and 500 μL of acidic ninhydrin into 5 mL centrifuge tubes and incubate in a boiling water bath for 30 min, shaking twice while wearing heat-resistant gloves during the process. After the reaction is complete, cool to room temperature, add 1 mL of toluene to the centrifuge tube, and shake thoroughly until homogenized. After the solution separates into layers, measure the absorbance of the supernatant at 520 nm (zero with distilled water). Each treatment was repeated three times.

[0099] Proline standard curve determination: A standard curve was plotted using proline standard solutions of different concentrations (0-50 μg / mL). y = 0.0296x + 0.0059, R0 2 = 0.999. The proline content in wheat leaves was calculated according to the standard curve.

[0100] (6) Data processing All data were recorded using Excel 2019, and one-way ANOVA and graphing were performed using R software. 2.2 Results and Analysis

[0101] 2.2.1 Results of screening for fertility-promoting function 2.2.1.1 Analysis of IAA Characteristics IAA Qualitative Analysis: such as Figure 3 As shown, the leftmost layer is blank LB medium without inoculation of the strain, and the rightmost layer is the experimental group. When the strain was mixed with an equal volume of Salkowski colorimetric solution, the solution turned red, indicating that the strain had the ability to produce IAA; the darker the color, the stronger the IAA production ability. The results showed that the endophytic bacteria HB-4, HB-5, HB-7, HB-8, and HB-9 of Haloxylon ammodendron seeds had IAA production function; however, HB-7 had a lighter color, indicating a lower yield. No IAA-producing strains were screened from the endophytic bacteria of Caragana korshinskii seeds. Quantitative IAA analysis: A total of 5 strains (22.73%, 5 / 22) producing IAA were screened, with yields ranging from 0.25 μg·mL⁻¹. -1 -18.48 μg·mL -1 Between (Table 19). The yield of strain HB-4 was significantly higher than that of the other four strains ( P <0.05).

[0102] Table 19 Statistics on the growth-promoting function of bacterial strains Note: "-" indicates that the corresponding function was not detected; "+" indicates that the corresponding function is present; different letters indicate significant differences.

[0103] 2.2.1.2 Effects of inoculated strains on wheat seedling growth Figure 4 The results of phenotypic differences in wheat plants from different treatment groups 30 days after inoculation were presented. Morphological comparison revealed that the control group (CK) inoculated with the endophytic growth-promoting strain Priestia aryabhattai HB-4 showed better growth and more developed secondary roots, demonstrating a significant growth advantage.

[0104] Figure 5 Quantitative analysis showed that, compared with the uninoculated control group (CK), HB-4 inoculation had a highly significant effect on both the fresh weight and dry weight of wheat. Under the influence of HB-4, the fresh weight and dry weight of wheat seedlings increased by 120.33% and 69.19%, respectively. P <0.01%. Strains HB-4 had a significant effect on wheat stem length but no effect on wheat root length. P =0.06). After inoculation with strain HB-4, the wheat stem length increased by 29.20% ( P <0.05%. This indicates that the inoculated strain HB-4 (Priscilla auriculata, Priestia aryabhattai It has a certain promoting effect on wheat growth.

[0105] 2.2.1.3 Effects of inoculated strains on wheat physiological indicators Figure 6 The results showed that the inoculated strain had a positive effect on wheat growth. Compared with the control, inoculation with HB-4 increased the total chlorophyll content of wheat leaves by 36.02% ( P <0.05). However, under the action of strain HB-4, the malondialdehyde (MDA) content in wheat leaves decreased by 26.33 ( ). P <0.05%. HB-4 increased CAT activity in wheat leaves by 98.02% ( P <0.01). HB-4 did not significantly increase the POD activity of wheat. HB-4 increased the proline content of wheat by 26.47% ( P <0.05).

[0106] In conclusion, the pot experiment confirmed that the inoculated strain HB-4 has a promoting effect on the growth and development of wheat.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. An endophytic fungus of desert plants, characterized in that, The endophytic bacteria of the desert plants are *Priscilla argentea* (…). Priestia aryabhattai HB-4 was deposited at the China Center for Type Culture Collection (CGMCC) on November 17, 2025, with accession number CGMCC No. 36665.

2. A microbial inoculant, characterized in that, The microbial agent is obtained by inoculating Priestella HB-4 as described in claim 1 into a culture medium and then culturing it.

3. The microbial agent as described in claim 2, characterized in that, The specific preparation method includes the following steps: After inoculating Priestella HB-4 onto LB liquid medium and culturing, the bacterial culture was collected and centrifuged to obtain the supernatant, which is the microbial inoculum.

4. The application of the desert plant endophytic bacteria as described in claim 1 or the microbial agent as described in claim 2 in promoting plant growth.

5. The application as described in claim 4, characterized in that, The promotion of plant growth is manifested in the increase of plant stem length, fresh weight, and dry weight.

6. The use of the desert plant endophytic bacteria as described in claim 1 or the microbial agent as described in claim 2 in the production of indoleacetic acid.

7. The application of the desert plant endophytic bacteria as described in claim 1 or the microbial agent as described in claim 2 in increasing plant chlorophyll content, reducing plant malondialdehyde content, and / or increasing plant catalase activity.

8. The application as described in any one of claims 4 to 7, characterized in that, The plant in question is wheat.

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