Plant rhizosphere growth-promoting strain dy58 and its use

Abstract

The present invention relates to the field of microbial technology, and specifically discloses a plant rhizosphere growth-promoting strain dy58 and its use. The plant rhizosphere growth-promoting strain dy58 was deposited in the General Microbiology Center of the China Culture Collection Administration on March 26, 2024, and was classified and named as Pseudomonas resinophilus Pseudomonas resinovorans , the deposit number is CGMCC No.30150. Strain dy58 has a high ability to secrete siderophores and has a wide range of applications as an agricultural soil inoculant. In hydroponic experiments, exogenous application of the inoculum preparation of strain dy58 can effectively increase the growth rate of plants, the chlorophyll content of leaves, and the fresh weight of aboveground parts. In potted experiments, exogenous application of the inoculum preparation of this strain can effectively increase the growth rate of plants, the chlorophyll content of leaves, the yield per plant, increase the Fe and Zn content of tubers, and improve the quality of potato tubers.

Description

Technical Field

[0001] The present invention belongs to the field of microbial technology, and in particular relates to a plant rhizosphere growth-promoting strain dy58 and a use thereof. Background Art

[0002] potato( Solanum tuberosum L. ) is one of the world's important food crops. Its tubers are rich in carbohydrates, proteins, vitamins and mineral elements, and are the main source of food in many regions. However, potatoes have low efficiency in absorbing mineral elements such as iron (Fe) and zinc (Zn) during their growth, especially when the availability of these elements in the soil is insufficient, which can easily lead to a decrease in potato yield and quality. Iron and zinc are essential trace nutrients for plant growth and development, and are involved in various physiological metabolic processes, such as photosynthesis, respiration, and enzyme activity regulation. Iron and zinc deficiency not only affects plant growth, but also leads to a decrease in the content of mineral elements in the tubers, thereby affecting their nutritional value and edible quality.

[0003] Traditionally, chemical fertilizers have been used to replenish iron and zinc in the soil. However, this approach is associated with high costs, low utilization rates, and environmental pollution. Furthermore, long-term use of chemical fertilizers can negatively impact soil compaction and microbial community imbalance. Therefore, the development and rational utilization of efficient microbial fertilizers suitable for potato production is crucial.

[0004] Plant growth promoting rhizobacteria (PGPR) refer to a group of microorganisms that grow in the rhizosphere of plants and can promote crop growth through both direct and indirect mechanisms. PGPR provide nitrogen, phosphorus, and potassium, the three essential macronutrients required by plants, by fixing nitrogen, solubilizing phosphorus, and potassium. This directly increases the nutrient content in the soil, promoting plant nutrient absorption and growth. PGPR also synthesizes various plant hormones and other molecules, such as indole-3-acetic acid (IAA), cytokinins, gibberellins, and siderophores, to antagonize plant pathogens and enhance host disease resistance. PGPR can help plants more efficiently absorb elements such as iron and zinc from the soil and convert them into forms that can be used by the plant. This effect not only increases crop yield but also enhances the nutritional value of crops.

[0005] Under natural conditions, the plant rhizosphere is a complex environment. Inoculated microbial agents can be considered "invaders." To withstand multiple environmental stresses, they must compete for niches with populations within the native microbial community. Only by successfully colonizing can they exert their effectiveness. Naturally present within the soil microbiome are a range of specialized bacterial communities that can adapt to extreme environments, outperforming competition within the same ecological niche, thereby helping plants withstand adversity.

[0006] Screening and identifying PGPR strains with efficient siderophore secretion and other growth-promoting properties from the potato rhizosphere, and developing microbial fertilizers suitable for potatoes, can not only improve the potato's efficiency in absorbing mineral elements such as iron and zinc, but also promote plant growth, increase yield, and improve tuber quality. This method has the advantages of being environmentally friendly, sustainable, and low-cost, and meets the needs of green development in modern agriculture. Therefore, screening and developing efficient PGPR strains suitable for potatoes and their microbial fertilizer products are of great significance for solving the problem of low mineral element absorption efficiency in potatoes, and also provide a reference for the development of microbial fertilizers for other crops.

[0007] Pseudomonas resinophilus ( Pseudomonas resinovorans ) is an aerobic Gram-negative bacterium of the genus Pseudomonas. It has been reported that Pseudomonas resinophilus has a highly effective degradation effect on aliphatic ester pollutants, relatively completely converting pollutants into harmless substances such as CO2 and H2O. It can be used to remediate aliphatic ester contamination in environmental media such as polluted water and soil. Literature reports that Pseudomonas resinophilus can be used to produce long-chain dicarboxylic acid (DCn), an important chemical intermediate. Literature also reports that Pseudomonas resinophilus can be used to produce borneol dehydrogenase (PrBDH). However, there are few reports on the use of Pseudomonas resinophilus in promoting plant growth. Summary of the Invention

[0008] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and provide a plant rhizosphere growth-promoting strain dy58 and its use. Strain dy58 is a resin-feeding Pseudomonas with excellent iron carrier secretion ability. Experiments have found that it has a significant promoting effect on potato growth and has prospects in the application of potato cultivation and agricultural soil inoculants.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The first aspect of the present invention is to provide a plant rhizosphere growth-promoting strain dy58, which was deposited in the General Microbiological Center of the China Culture Collection Administration on March 26, 2024, and was classified and named as Pseudomonas resinophilus Pseudomonas resinovorans , the deposit number is CGMCC No.30150.

[0011] The second aspect of the present invention is to provide a bacterial agent, which contains the above-mentioned plant rhizosphere growth-promoting strain dy58.

[0012] Furthermore, the bacterial agent is a bacterial agent that promotes plant growth and / or a bacterial agent that improves soil.

[0013] Furthermore, the improved soil is embodied as a siderophore-producing soil.

[0014] Furthermore, the promoting of plant growth is manifested as all or part of the following: increasing the plant height growth rate, the chlorophyll content in plant leaves, the yield per plant and / or the iron and zinc content in plant fruits.

[0015] Furthermore, the plant is potato.

[0016] The third aspect of the present invention is to provide the application of the above-mentioned plant rhizosphere growth-promoting strain dy58 or bacterial agent, including any of the following applications:

[0017] A1) Application in soil improvement;

[0018] A2) Application in promoting plant growth;

[0019] A3) Application in siderophore production;

[0020] A4) Application in the preparation of siderophore-producing products.

[0021] Furthermore, the promoting plant growth is embodied in whole or in part as follows: increasing the plant height growth rate, chlorophyll content in plant leaves, single plant yield and / or iron and zinc content in plant fruits, and the plant is potato.

[0022] The fourth aspect of the present invention is to provide a method for promoting plant growth, comprising the following steps: applying the above-mentioned plant rhizosphere growth-promoting strain dy58 or bacterial agent to plant plants, plant seeds or plant rhizosphere soil.

[0023] The fifth aspect of the present invention is to provide a method for improving soil, comprising the following steps: applying the above-mentioned plant rhizosphere growth-promoting strain dy58 or the above-mentioned bacterial agent to the soil to be improved; the improved soil is embodied as producing siderophores.

[0024] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0025] The plant rhizosphere growth-promoting strain dy58 screened by the present invention has a high ability to secrete siderophores and has broad applications as an agricultural soil inoculant. In hydroponic experiments, exogenous application of an inoculum preparation of strain dy58 can effectively increase plant growth rate, leaf chlorophyll content, and aboveground fresh weight. In potted experiments, exogenous application of an inoculum preparation of this strain can effectively increase plant growth rate, leaf chlorophyll content, single plant yield, increase the Fe and Zn content of potato tubers, and improve potato tuber quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a pale yellow transparent circle image of strain dy58 on CAS medium;

[0027] Figure 2 This is the colony image of strain dy58 on TSA medium;

[0028] Figure 3 This is a microscopic image of the colony of strain dy58 (10×100);

[0029] Figure 4 The figure shows the electrophoresis results of the PCR products of 16S rDNA of strain dy58; Note: M is the Maker DNA DL2000 marker (DL2000 band distribution: 2000, 1000, 750, 500, 250, 100 bp), 1 and 2 are PCR products;

[0030] Figure 5 This is the phylogenetic tree of dy58 based on 16S rDNA sequence;

[0031] Figure 6 This is the annotation analysis diagram of the homologous protein cluster (COG) of the whole genome sequencing of strain dy58;

[0032] Figure 7 This is the Gene Ontology annotation (GO annotation) analysis diagram of the whole genome sequencing of strain dy58;

[0033] Figure 8 KEGG annotation analysis diagram for the whole genome sequencing of strain dy58;

[0034] Figure 9 This is a virulence factor analysis diagram of the whole genome sequencing of strain dy58;

[0035] Figure 10 This is the drug resistance gene analysis diagram of the whole genome sequencing of strain dy58;

[0036] Figure 11 Synthesize gene annotation map for the siderophore core of the whole genome sequence of strain dy58;

[0037] Figure 12 This is a graph showing the growth of the whole plant in the hydroponic control group in Example 2;

[0038] Figure 13 This is a graph showing the growth of the whole plant in the experimental group of DES plants inoculated with strain dy58 in hydroponic culture in Example 2;

[0039] Figure 14 This is a comparison of the whole plant growth of the experimental group and the control group of the DES plants inoculated with strain dy58 in the potted plants of Example 3. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions and advantages of the present invention clearer, the specific embodiments of the present invention are described in further detail below in conjunction with specific examples and accompanying drawings. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this field or the product specifications are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0041] Example 1

[0042] Isolation, identification and preservation of the plant growth-promoting rhizosphere strain dy58.

[0043] 1. Isolation, purification and screening of plant rhizosphere growth-promoting strain dy58

[0044] The potato rhizosphere soil with relatively low content of available nutrients was obtained by random sampling in Dayao County, Yunnan Province (25.85°N, 101.25°E). The collected rhizosphere soil was resuspended in sterile water and diluted in 10-fold gradients. -4 The soil suspension at a diluted concentration was evenly applied to TSA medium, and a single colony strain was isolated and purified. The single colony strain was inoculated onto CAS solid medium, and the effective strain was selected to further repeat the siderophore production experiment.

[0045] The preparation method of the culture medium used in the strain isolation, purification and screening process is as follows:

[0046] Tryptic soy peptone medium (TSB medium): TSB 30g / L, add 15 g / L agar to make tryptic soy peptone agar medium (TSA medium).

[0047] CAS medium: 30 g / L TSA medium, add filter-sterilized 10× CAS detection solution.

[0048] Determination of the siderophore secretion ability of the plant growth-promoting rhizosphere strain dy58.

[0049] Qualitative determination of the siderophore secretion capacity of strain dy58: After overnight activation, the test strain is inoculated onto CAS solid medium in triplicate. After the bacterial suspension on the solid medium has air-dried, the plate is incubated at 30°C for two days. Iron ions in the plate are competitively chelated by the siderophores secreted by the strain, causing the original bright blue chelate to turn pale yellow due to the loss of iron ions. The siderophore secretion capacity of the strain is calculated based on the ratio (D / d) of the pale yellow halo diameter (D) to the colony diameter (d). The diameters of the pale yellow halo and the transparent solubilization zone are accurately measured to calculate the solubilization index (SI).

[0050] SI = diameter of light yellow halo D (mm) / colony diameter d (mm)

[0051] Figure 1 The figure shows the siderophore secretion capacity of strain dy58. After inoculation on CAS solid medium and 2 days of static culture, a pale yellow halo was produced, indicating that the strain has the ability to secrete siderophores. The size of the pale yellow halo was measured using the cross-hatch method, and the ratio of the halo diameter (D) to the colony diameter (d) was calculated to be 2.87 ± 0.38, indicating that strain dy58 has a strong ability to secrete siderophores.

[0052] Quantitative determination of the siderophore secretion capacity of strain dy58: After overnight activation, the test strain was inoculated into TSB liquid medium in triplicate and incubated at 30°C and 180 rpm for 48 h. The culture was centrifuged at 12,000 rpm for 5 min, and the supernatant was collected. Using 3 mL of distilled water as a control for zero adjustment, 3 mL of the supernatant was collected as the experimental group, and 3 mL of uninoculated TSB medium was used as the control. Equal volumes of CAS colorimetric reagent were added, mixed, and incubated in the dark for 30 min. The absorbance of the experimental group (As) and the control group (Ar) was measured at 630 nm. The relative siderophore content in the culture medium was calculated according to the following formula.

[0053] Siderophore relative content (%) = [(Ar-As) / Ar] × 100%

[0054] The As value was determined to be 1.204, the Ar value was 1.616, and the relative content of siderophore in the culture medium of strain dy58 was calculated to be 25.50%. Strain dy58 had a strong ability to secrete siderophore.

[0055] Using the dilution spread plate method, the streak plate method, and the siderophore secretion capacity assay, a bacterial strain, named dy58, was isolated and purified from potato rhizosphere soil samples collected from Dayao County, Yunnan Province. It has a high siderophore secretion capacity.

[0056] 2. Strain identification

[0057] 2.1 Identification of bacterial morphology, physiological and biochemical characteristics of strain dy58

[0058] Observe and describe the colony morphology, color, and physiological and biochemical determination of strain dy58 with reference to the "Common Bacterial System Identification Manual" and "Berger's Manual of Bacterial Identification".

[0059] Colony morphology: Figure 2 Figure 4 shows the colony morphology of strain dy58 on TSA medium. The colonies of strain dy58 are light yellow opaque colonies with a smooth surface, a slightly convex middle, and regular colony edges. Figure 3 The colony morphology of strain dy58 observed under an optical microscope is straight or slightly curved rod-shaped.

[0060] Physiological and biochemical characteristics: Strain dy58 was Gram-negative, had capsule and no spores.

[0061] 2.2 Molecular identification of strain dy58

[0062] The genomic DNA of strain dy58 was extracted and used as a PCR template. The universal primers of bacterial 16S rDNA were used. The sequences of primers are shown in SEQ ID NO: 2 and SEQ ID NO: 3, 27F: 5'-AGAGTTTGATCCTGGCTCAG-3',

[0063] 1492R:5'-TACGGCTACCTTGTTACGACTT-3', performed PCR amplification. Figure 4 The PCR products shown were tested by gel electrophoresis and then sent to Meiji Biopharmaceutical Technology Co., Ltd. for sequencing. The raw sequences obtained by Sanger sequencing were quality-controlled to remove low-quality bases. The clean sequences were then spliced ​​to obtain the assembled sequence. The species with the highest similarity obtained by blasting against the NT database was used as the bacterial identification result. 16S rDNA gene sequences of closely related species within the same genus were selected for homology analysis, and a phylogenetic tree was constructed using MEGA11.0, as shown in the following figure. Figure 5 shown.

[0064] 2.3 Whole genome analysis of strain dy58

[0065] Strain culture collection: The test strain was activated by overnight culture, and a single colony was picked and inoculated into 500 mL TSB medium. The culture was cultured at 220 rpm at 30°C overnight, and the OD was measured. 600 When the dapoxetine value was 0.5-0.7, the cells were collected and centrifuged at 5000 rpm for 10 minutes. The cells were washed twice with sterile 0.9% NaCl solution and harvested to a weight of 0.5-1.0 g. The collected cells were snap-frozen in liquid nitrogen, shipped at low temperature on dry ice, and sent to Meiji Biotechnology Co., Ltd. for whole-genome sequencing. The company's sequencing strategy employed complementary sequencing methods, combining second-generation (Illumina HiSeq) and third-generation (PacBio) sequencing. Preliminary sequencing results were quality-corrected using GC-depth distribution analysis, K-mer frequency distribution, and genome coverage analysis to obtain complete chromosome and plasmid sequences. Further analysis was performed using COG, GO, and KEGG annotation, as well as prediction of virulence genes, drug resistance genes, and siderophore genes.

[0066] COG (clusters of orthologous groups of proteins) annotation: COG can predict and classify the functions of individual microbial proteins and the functions of proteins in complete genomes through systematic evolutionary relationship classification. Figure 6 The results showed that a total of 5,420 proteins in strain dy58 were annotated with COG functions, accounting for 96.83% of all its genes. The number of genes annotated for amino acid transport, metabolic gene transcription, and general function prediction was 603, 503, and 457, respectively. In addition, 413 genes with signal transduction mechanisms and 310 genes with inorganic ion transport and metabolism functions were annotated.

[0067] GO (Gene Ontology) Annotation: GO is an internationally standardized gene function classification system, divided into three ontologies, describing the molecular function, cellular component, and biological process of a gene. Each gene corresponds to one or more GO functions. GO annotation can be used to annotate genes across the entire genome of a strain, verify known functions, and uncover unknown, hidden functions. Figure 7 The results showed that 3,317 genes in strain dy58 were annotated with the GO function, accounting for 67.23% of all genes. Of these, 2,613, 1,612, and 1,603 genes were annotated with molecular function, 78.77%, 48.59%, and 48.32% of all GO-annotated genes, respectively. Among them, 296 genes were annotated with metal ion binding and 71 genes with zinc ion binding.

[0068] KEGG (Kyoto Encyclopedia of Genes and Genomes) Note: The KEGG database is often used to comprehensively understand the cellular metabolic pathways of strain secretion products and the functions of gene metabolites. Figure 8 The strain dy58 was annotated with genes belonging to six major categories: cellular processes, environmental information processing, genetic information processing, human diseases, metabolism, and organic systems. A large number of genes related to environmental response were enriched, with dy58 enriched in 245 membrane transport genes and 248 signal transduction genes.

[0069] Prediction of virulence genes: Microorganisms can invade and attach to specific host plants through specific virulence genes and virulence factors, thus forming an interactive microenvironment between microorganisms and host plants. Figure 9The results showed that a total of 747 virulence genes were annotated in dy58, and the virulence factors could be divided into four categories: offensive, defensive, nonspecific and conventional virulence factors. Among them, there were 145 genes related to iron uptake, 7 genes related to magnesium uptake and 46 genes related to the secretion system.

[0070] Prediction of drug-resistant genes: comparative analysis of drug-resistant genes of strain dy58, Figure 10 The strain dy58 was enriched for 326 total resistance genes, annotated to 10 different antibiotic classes. Tetracyclines, macrolides, and fluoroquinolones were predominant, with 113, 101, and 97 genes recruited, respectively. Strain dy58 exhibits broad-spectrum resistance and strong adaptability, suggesting potential for broad-spectrum applicability.

[0071] Siderophore gene prediction: The whole genome sequence of strain dy58 was analyzed on the antiSAMSH website for secondary metabolite synthesis gene clusters, which were rich in siderophore synthesis gene clusters (NRP-metallophore). The siderophore core synthesis genes of strain dy58 were annotated. Figure 11 It was shown that strain dy58 was annotated with five siderophore core synthesis genes (2335, 2336, 2341, 2344, and 2350).

[0072] Based on the bacterial morphology, physiological and biochemical characteristics and molecular detection results of strain dy58, the strain was identified as Pseudomonas Pseudomonas resinovorans ), the 16S rDNA gene sequence of which is shown in SEQ ID NO: 1.

[0073] 3. Strain preservation

[0074] The plant rhizosphere growth-promoting strain dy58 is classified as Pseudomonas resinophilus ( Pseudomonas resinovorans The strain (CGMCC No. 30150) has been deposited at the China General Microbiology Center, Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. The deposit number is CGMCC No. 30150, and the deposit date is March 26, 2024.

[0075] Example 2

[0076] The hydroponic experiment investigated the growth-promoting effect of the plant rhizosphere growth-promoting strain dy58 on potato plants.

[0077] 1. Hydroponic experiment

[0078] Test plants: potato ( Solanum tuberosumSterile tissue-cultured seedlings of the Solanum tuberosum L. cultivar Desiree (hereinafter referred to as DES) were propagated via axillary buds and grown in an artificial climate chamber using MS30 solid medium. The culture temperature was set at 20°C ± 1°C, humidity at 60% ± 5%, a light intensity of 3000-4000 lx, and a photoperiod of 16 h light / 8 h dark. Potato plants with normal, uniform growth were selected 15-20 days after propagation.

[0079] Using 1 / 2 Hoagland's broth as the basal medium, 50 mL centrifuge tubes with planting baskets served as hydroponic colonization devices. 35 mL of broth was added to each centrifuge tube, and one potato seedling of similar growth was planted in each tube. Each treatment was replicated 20 times and randomly grouped.

[0080] After one week of hydroponic culture, the original plant height was measured with a vernier caliper. After the hydroponic culture was completed, samples were taken from the terminal buds of the potato plants to determine the chlorophyll content in the leaves.

[0081] The specific measurement method is as follows:

[0082] Plant height: Use a ruler to measure the height from the top of each potato plant to the surface of the absorbent cotton in the planting basket. Calculate the average of these repeated measurements as the plant height. Calculate the Δ7-day growth rate using the following formula:

[0083] Δ7d growth rate = (7d plant height - initial plant height) / initial plant height.

[0084] Chlorophyll content: Samples of young leaves from the terminal buds of potato plants were collected 21 days after inoculation and hydroponics. An 8 mm pore punch sampler was used to collect the young leaves. 1 mL of chlorophyll extract (acetone: anhydrous ethanol: water = 4.5:4.5:1) was added to every two leaves. The leaves were kept in the dark and extracted until the leaf tissue was transparent. The absorbance of the extract was measured at wavelengths of 645 nm and 663 nm. The chlorophyll content was calculated according to the following formula:

[0085] Total chlorophyll content (mg / gFW1) = (20.2×Abs645 nm+8.02×Abs 663 nm)×V / (1000×W)

[0086] V is the volume of the extract used (mL);

[0087] W is the leaf sampling area (dm 2 ) or sample fresh weight (g).

[0088] Bacterial solution preparation:

[0089] (1) After overnight activation of strain dy58, single colonies were picked and placed in LB medium. The culture was incubated at 30°C and 200 rpm for 10-12 h as seed inoculum. The seed solution was transferred to LB medium at a 1% (volume ratio) concentration and incubated at 36°C and 200 rpm overnight.

[0090] (2) Collect the cells by centrifugation at 6000 rpm for 5 min, resuspend and wash the cells 1-2 times with sterile 0.9% sodium chloride solution, and then resuspend the cells with sterile 0.9% sodium chloride solution to adjust the OD 600 After the dilution reaches 1.0, it is used as the bacterial solution for inoculation.

[0091] Each tube of potato plants was inoculated with 1 mL of the bacterial inoculum preparation, and the bacterial inoculum preparation was mixed with the liquid culture medium.

[0092] Table 1 shows the growth index measurements of potato DES seedlings in the control and experimental groups during the hydroponic experiment. Calculations based on the data in the table indicate that the 7-day plant height growth rate and chlorophyll content per unit area of ​​the experimental group increased by approximately 148.04% and 123.53%, respectively, compared to the control group.

[0093] Table 1 Growth status of potato DES seedlings in hydroponic experiment

[0094]

[0095] like Figure 12 and Figure 13 The figure shows a comparison of potato DES plants in the experimental and control groups after hydroponic inoculation with strain dy58. As can be seen, the experimental group showed faster growth, taller plants, and greener leaves. These results demonstrate that hydroponic inoculation with strain dy58 significantly increases the plant height growth rate and chlorophyll content per unit area of ​​potato DES plants.

[0096] Example 3

[0097] A pot experiment was conducted to investigate the growth-promoting effect of the plant rhizosphere growth-promoting strain dy58 on potato plants.

[0098] Test plants: potato ( Solanum tuberosum L.) Common commercial cultivar Desiree seed potato tubers.

[0099] Pre-treatment of potato tubers: Select healthy potato tubers of uniform size and without mechanical damage, soak the tubers in a 10 mg / L gibberellin solution for 1 hour, take out the tubers, wipe the surface dry, and store them in a dark and ventilated place until buds and small sprouts appear, then they can be used for potted planting.

[0100] After germination, tubers were sown in rigid plastic pots filled with 15 L of field soil from a potato cultivation base and buried at a depth of 10 cm for cultivation. Two treatments were set up: a control group (DES-CK) and an experimental group (DES-dy58), with 15 potted plants in each treatment in parallel.

[0101] 1. Preparation of bacterial liquid inoculation preparation: the method is the same as Example 2.

[0102] Strain application: 10 mL of the inoculum was applied per potato. Dilute the inoculum to 250 mL and pour it over the potato plant roots. For the blank treatment, dilute the inoculum to the same proportion with 10 mL of sterile 0.9% NaCl solution and apply it to the plant roots.

[0103] Application period: Start applying the bacterial liquid inoculum preparation when all the plants have emerged from the soil for 7 days. Apply once every 14 days for 3 consecutive times. Apply in the morning or evening on sunny days or on cloudy days to avoid direct sunlight at noon which may cause failure in the application of the bacterial liquid inoculum preparation.

[0104] 2. Determination of potato yield and quality.

[0105] Plant height: Use a ruler to measure the height of the plant from the ground surface to the top at the start of inoculation. Measure every 14 days and calculate the Δ14 d growth rate using the following formula:

[0106] Δ14-day growth rate = (14-day plant height - initial plant height) / initial plant height

[0107] Chlorophyll content: During the period of high nutritional demand when potato plants are in full bloom and potatoes are forming, use a hole punch to punch holes in the tender leaves at the top of the plants to take samples. The chlorophyll content determination method is the same as that of the hydroponic experiment.

[0108] Yield per plant: Tubers were collected after the above-ground parts of potato plants withered, and all plants in each treatment were harvested individually. The yield per plant was measured using a 100-day balance.

[0109] Mineral element content determination: Medium-sized potato tubers from each individual plant were randomly selected, peeled, and freeze-dried to prepare powder for analysis of mineral elements such as iron and zinc. A quantitative amount of 0.3 g of freeze-dried potato powder was weighed and placed in a polytetrafluoroethylene digestion vessel. 7 mL of high-grade nitric acid and 2 mL of 30% hydrogen peroxide were added. The sample was sealed and digested in a microwave digester according to the procedure in Table 3. After digestion, the tube was opened and placed in an infrared acid remover for acid removal (180°C, 30–60 min) until approximately 2 mL of sample remained. The sample was then diluted to 25 mL and prepared for analysis of mineral element content. Flame atomic absorption spectrophotometry was used to determine the content of the sample according to the instrument's parameters. The iron and zinc contents of the sample were determined using a standard curve method.

[0110] Table 3. Microwave digestion program

[0111]

[0112] Table 3 shows the growth index measurements of potato DES in the control and experimental groups in the potted experiment. Calculations based on the data in the table indicate that, compared with the control group, the experimental group's potato DES had increased 14-day plant height growth rate, chlorophyll content per unit area, yield per plant, and Fe and Zn contents in tubers by approximately 66.34%, 18.67%, 36.67%, 30.83%, and 171.24%, respectively.

[0113] Table 3. Growth status of potato DES seedlings in pot experiment.

[0114]

[0115] like Figure 14 Figure 2 shows a comparison of potato DES plants in the experimental and control groups after inoculation with strain dy58 in a potted experiment. The figure shows that the control potato plants exhibited chlorosis of the top leaves and smaller plant size. This chlorosis was alleviated by exogenous addition of strain dy58. The growth-promoting effect of the strain on plant growth was reflected in three indicators: plant height growth rate, chlorophyll content, and yield per plant. After harvest, the Fe and Zn content of the tubers were measured to reflect the nutritional quality of the potatoes. These results demonstrate that inoculation with strain dy58 significantly improved the plant height growth rate, chlorophyll content per unit area, yield per plant, and Fe and Zn content of the tubers in DES potato plants in the potted experiment.

[0116] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A plant rhizosphere growth-promoting strain, characterized in that: The strain is a plant rhizosphere growth-promoting strain dy58, which was deposited in the General Microbiology Center of the China Culture Collection Administration on March 26, 2024, and was classified as Pseudomonas resinophilus Pseudomonas resinovorans , the deposit number is CGMCC No.30150.

2. A bacterial agent, characterized in that The bacterial agent comprises the plant rhizosphere growth-promoting strain dy58 according to claim 1.

3. The use of the plant rhizosphere growth-promoting strain dy58 according to claim 1 or the bacterial agent according to claim 2, characterized in that: This includes any of the following applications: A1) Application in soil improvement; A2) Application in promoting plant growth; A3) Application in siderophore production; A4) Application in the preparation of siderophore-producing products.

4. The use according to claim 3, characterized in that The plant growth promotion is embodied in whole or in part as follows: increasing the plant height growth rate, the chlorophyll content in the plant leaves, the single plant yield and / or the iron and zinc content in the plant tubers, and the plant is potato.

5. A method for promoting plant growth, characterized in that: The method comprises the following steps: applying the plant rhizosphere growth-promoting strain dy58 according to claim 1 or the bacterial agent according to claim 2 to the rhizosphere soil of the plant.

6. A method for improving soil, characterized in that: The method comprises the following steps: applying the plant rhizosphere growth-promoting strain dy58 according to claim 1 or the bacterial agent according to claim 2 to the soil to be improved; the improved soil is embodied as producing siderophores.

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