Proline leptosphaerophilus GLBv-Z4 with salt-tolerant growth-promoting function and application of proline leptosphaerophilus GLBv-Z4

Abstract

The invention relates to the technical field of agricultural microorganisms, in particular to a proline microphage GLBv-Z4 with salt-tolerant and growth-promoting functions and application of the proline microphage GLBv-Z4, and the proline microphage GLBv-Z4 is obtained by being separated and screened from beet rhizosphere soil in a comprehensive treatment and utilization trial project test field of saline-alkali cultivated land in Gansu County 2024. The strain has good salt resistance and acid and alkali resistance; the plant growth promoting agent has various plant growth promoting capacities including nitrogen fixation, phosphorus dissolution, potassium dissolution, siderophore production, auxin IAA production and the like. After the strain is inoculated, under salt stress, the salt tolerance of plant seedlings can be remarkably improved, the growth and development of plant roots are promoted, the leaf area and fresh weight of plants are increased, and the accumulation of soluble substances and the activity of an antioxidant enzyme system of the plants can be increased under the salt stress, so that the adverse effect of the salt stress on the plant seedlings is relieved; the method has a considerable application prospect in saline-alkali soil improvement.

Description

Technical Field

[0001] This invention relates to the field of agricultural microbial technology, specifically to the salt-tolerant proline-promoting bacterium GLBv-Z4 and its application technology. Background Technology

[0002] Soil salinization is a global environmental problem and has become a significant factor restricting plant growth and sustainable agricultural development. High-salinity soil environments cause plant roots to absorb excessive salt ions, leading to ion toxicity and osmotic stress, resulting in water loss, nutrient imbalance, and physiological dysfunction, severely impacting normal plant growth. High-salinity environments also reduce cell membrane stability, interfere with enzyme activity, further damage cell function, and may ultimately lead to stunted plant growth and even death. Saline-alkali land is an extremely important reserve of arable land in my country. Exploring the potential of saline-alkali land and carrying out its comprehensive utilization is of great strategic significance for ensuring national food security.

[0003] Plant growth-promoting rhizobacteria (PGPRs) are a class of beneficial soil bacteria that inhabit the rhizosphere of plants. They enhance plant vitality, improve nutrient utilization, and resist pathogens, forming a mutually beneficial symbiotic relationship with their host plants. PGPRs promote plant growth, improve soil health, and increase crop yield through various mechanisms. PGPRs possess abilities such as nitrogen fixation, phosphorus solubilization, potassium solubilization, and iron production. Through reactions such as acidolysis, chelation, and ion exchange, they can convert insoluble mineral elements in the soil into forms that plants can absorb, thereby promoting nutrient uptake and utilization. In addition, some PGPRs can secrete indole-3-acetic acid (IAA), cytokinins, and gibberellins to regulate plant hormone levels, directly promoting plant growth and development. Studies have shown that the application of PGPRs can optimize the plant rhizosphere ecological environment by increasing microbial community diversity, mitigating soil acidification, and enhancing nutrient transformation and cycling efficiency, thus effectively promoting plant nutrient acquisition. PGPR can also enhance plant stress resistance through various physiological and biochemical regulatory mechanisms, including increasing the activity of antioxidant enzymes, promoting the accumulation of osmotic regulators (such as proline and soluble sugars), secreting extracellular polysaccharides, and inducing the expression of salt stress-related resistance genes and proteins. These effects work together to help plants maintain cellular homeostasis, alleviate ion toxicity and oxidative damage caused by salt stress, and thus improve the plant's growth status under adverse conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a novel small-banded proline-eating bacterium, GLBv-Z4, which is salt- and acid- and alkali-tolerant and can promote plant growth and development. This strain can be used for saline-alkali land improvement and is an excellent component for developing biological agents that can promote plant growth and development and enhance plant salt and alkali tolerance.

[0005] To achieve the above objectives, the embodiments of the present invention are as follows: A salt-tolerant growth-promoting bacterium of this invention was screened from the rhizosphere soil of sugar beets in the experimental field of the 2024 pilot project for comprehensive management and utilization of saline-alkali farmland in Gulang County, Gansu Province. The strain number was GLBv-Z4, and it was identified as... Prolinoborus fasciculus This strain exhibits salt and acid / alkali tolerance. Pot experiments have demonstrated that this strain can promote the growth of sugar beet seedlings under salt stress, significantly increasing root length, leaf area, and fresh weight, thus providing a more beneficial microbial resource for saline-alkali land improvement.

[0006] Based on the above research, the salt-tolerant growth-promoting bacteria provided by this invention has been deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35752. The deposit address is Institute of Microbiology, Chinese Academy of Sciences, No. 3, Beichen West Road, Chaoyang District, Beijing. The deposit date is August 27, 2025. The classification name is Prolinoborus fasciculus.

[0007] Another objective of this invention is to provide a method for isolating and identifying small-banded proline-phages, the implementation strategy of which is as follows: (1) Strains isolated from the root system of sugar beets in the saline-alkali land of Gulang, Gansu Collected rhizosphere soil from saline-alkali land plants was placed in an Erlenmeyer flask with sterile water and incubated at 28℃ and 180 r / min for 10–12 h. 1 mL of the supernatant was then diluted to a concentration of 10. −3 10 −4 and 10 −5 Divide the bacterial suspension by 100 μL and spread it onto LB solid medium, incubating at 28°C until single colonies appear. Pick single colonies and incubate them on LB liquid medium. Perform streak plating three times to isolate and purify the cultured bacterial culture. Store the purified strain at −80°C for later use.

[0008] (2) Screening of salt-tolerant strains and detection of their growth-promoting properties Salt-containing media were prepared by adding NaCl to LB solid medium at concentrations of 0%, 1%, 4%, 6%, 8%, and 10%. The activated isolated strains were inoculated into these media with different NaCl concentrations using the streak plating method to screen for the highly salt-tolerant strain GLBv-Z4. The nitrogen-fixing, phosphorus-solubilizing, and potassium-solubilizing abilities of strain GLBv-Z4 were determined using nitrogen-fixing medium, phosphorus-solubilizing medium, and potassium-solubilizing medium, respectively. Siderophoresis was detected using the double-layer plate method, and the production of IAA was determined colorimetrically.

[0009] The third objective of this invention is to provide an application of a small-banded proline-eating bacterium GLBv-Z4 in promoting the growth of sugar beet seedlings under salt stress, and the experimental protocol is as follows: A bacterial agent containing the above-mentioned small-banded proline-phage GLBv-Z4 is prepared by the following method: A single colony of GLBv-Z4 was picked and inoculated into a sterile Erlenmeyer flask containing LB liquid medium. The flask was incubated overnight with shaking at 28 °C and 180 r / min to obtain a seed culture. 5 mL of the seed culture was then inoculated into 500 mL of LB liquid medium and incubated until the bacterial OD... 600 When the concentration is 1.0–1.2, the bacterial cells are collected by centrifugation at 6,000 r / min for 5 min. The supernatant is discarded and the cells are resuspended in an equal volume of sterile water or NaCl solution to prepare a bacterial agent for later use.

[0010] The above-mentioned biological agent is used to promote the growth and development of sugar beet seedlings under salt stress. The method is as follows: the prepared agent is inoculated around the rhizosphere soil of sugar beet seedlings under salt stress.

[0011] The present invention also relates to the use of the above-mentioned microbial agent in any of the following aspects: Growth-promoting effect on sugar beet seedlings under salt stress; Increase root length, fresh weight, leaf characteristics (leaf length and width), plant height, and stem diameter of sugar beet seedlings under salt stress; Increase the chlorophyll content of sugar beet seedlings under salt stress; Reduce malondialdehyde content in sugar beet seedlings under salt stress; Reduce abscisic acid content in sugar beet seedlings under salt stress; Increases the accumulation of soluble substances (proline and soluble sugars) in sugar beet seedlings under salt stress; Enhance the activity of antioxidant enzyme system in sugar beet seedlings under salt stress.

[0012] Therefore, the beneficial effects of the present invention include, but are not limited to, the following aspects: The *GLBv-Z4* strain, a proline-producing bacterium with plant growth-promoting effects provided by this invention, has been identified as having strong salt and acid / alkali tolerance, with a maximum NaCl tolerance of 11%, and can grow normally within a pH range of 5–12. It exhibits growth-promoting characteristics such as nitrogen fixation, phosphorus solubilization, potassium solubilization, iron carrier production, and IAA production. Under salt stress, this strain can improve the salt tolerance of sugar beet seedlings, promote seedling growth and development by regulating hormone levels and increasing the accumulation of soluble substances, and mitigate the adverse effects of salt stress on sugar beet seedlings by enhancing the activity of antioxidant enzyme systems. The strain provided by this invention can provide excellent microbial resources and technical support for the development and application of microbial agents, and offer a new technical approach for saline-alkali soil improvement and sustainable agricultural development. Attached Figure Description

[0013] Figure 1 This is a morphological image of the small-banded proline-phage GLBv-Z4 on LB agar plates using the streak plating method according to the present invention. (Abstract Figure) Figure 2 - Figure 8 This is a graph showing the plant growth-promoting characteristics of the prolyphobic bacterium GLBv-Z4 according to the present invention. Figure 2 It is nitrogen fixation, Figure 3 It is potassium solubilization, Figure 4 It is a solution of organophosphates, Figure 5 It is a solution for inorganic phosphorus, Figure 6 It is an iron-producing carrier, Figure 7 This is the IAA standard curve; the numbers in the graph represent different concentrations of IAA. Figure 8 This is the IAA colorimetric reaction of strain GLBv-Z4. In the above figure, "CK" represents blank.

[0014] Figure 9 This invention is a phylogenetic tree constructed based on the 16S rRNA gene sequence of GLBv-Z4, a prolyptospira bacterium.

[0015] Figure 10 This invention relates to the detection of the salt tolerance of the prolyphobic bacterium GLBv-Z4. The percentages in the figure represent the NaCl concentration in the culture medium.

[0016] Figure 11 This invention relates to the detection of the acid and alkali resistance of the prolyphobic bacterium GLBv-Z4. The numbers in the figure represent the pH value of the culture medium.

[0017] Figure 12 This invention relates to the effect of the proline-eating bacterium GLBv-Z4 on the growth of sugar beet seedlings under different NaCl stresses. In the figure, "-GLBv-Z4" represents the uninoculated strain GLBv-Z4, and "+GLBv-Z4" represents the inoculated strain GLBv-Z4.

[0018] Figure 13 - Figure 18 This invention relates to the effect of the prolypeptidase GLBv-Z4 on the biomass of sugar beet seedlings under different NaCl stresses. Figure 13 It is fresh and heavy. Figure 14 Is it plant height, Figure 15 It is root long, Figure 16 It is a thick stem, Figure 17 Is it leaf length, Figure 18 The leaf width is represented by the error bars, which indicate the standard deviation. n= 3), lowercase letters indicate differences between different treatments reaching ( P <0.05) Significance level.

[0019] Figure 19 - Figure 26This invention relates to the effects of the prolyptotrophoblast GLBv-Z4 on the physiological indicators of sugar beet seedlings under different NaCl stresses. Figure 19 For ABA content, Figure 20 For MDA content, Figure 21 For soluble sugar content, Figure 22 For PRO content, Figure 23 For total chlorophyll content, Figure 24 For CAT activity, Figure 25 For POD activity, Figure 26 For SOD activity, the error bars represent the standard deviation. n= 3), lowercase letters indicate differences between different treatments reaching ( P <0.05) Significance level. Detailed Implementation

[0020] To more clearly illustrate the technical solution of the present invention, the present invention will now be described in further detail with reference to the specification and specific embodiments. The following embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of the present invention. Unless otherwise expressly stated, the experimental methods used in the embodiments of the present invention are all conventional methods known to those skilled in the art, and the raw materials, reagents, and equipment used can all be obtained through conventional commercial channels.

[0021] The culture medium and main reagents used in the embodiments of this invention are as follows: LB medium (g / L): peptone 10.0, yeast extract 5.0, NaCl 10.0; Nitrogen-fixing medium (g / L): CaCO3 10.0, mannitol 10.0, MgSO4•7H2O 0.2, K2HPO4 0.2, NaCl 0.2, FeSO4•7H2O 0.001, Na2MO4•H2O 0.005, agar powder 15.0; PKO medium (g / L): glucose 10.0, NH4SO4 0.5, NaCl 0.3, K2SO4 0.3, MgSO4 0.3, MnSO4 0.03, FeSO4 0.03, Ca3(PO4)2 5.0, agar powder 15.0; Lecithin medium (g / L): glucose 10.0, (NH4)2SO4 0.5, NaCl 0.3, K2SO4 0.3, MgSO4 0.3, MnSO4 0.03, FeSO4 0.03, Ca3(PO4)2 5.0, lecithin 0.2; Potassium-solubilizing medium (g / L): sucrose 5.0, MgSO4 0.5, Na2HPO3 2.0, FeCl3 0.005, CaCO3 0.1, soil minerals 1.0, agar powder 18.0; King liquid medium (g / L): tryptone 20, K2HPO4 1.5, MgSO4 1.5, glycerol 15mL, L-tryptophan 0.1; CAS medium (mg / L): Chrome azurite S (CAS) 60.5, hexadecyltrimethylammonium bromide (HDTMA) 72.9, FeCl3•6H2O 2.645, NaH2PO4•2H2O 295.25, Na2HPO4•12H2O 1213.5, NH4Cl 125, KH2PO4 37.5, NaCl 62.5, agar powder 9000; MKB medium (g / L): casein amino acids 5.0, glycerol 15mL, K2HPO4 2.5, MgSO4•7H2O 2.5, agar powder 20.

[0022] Reagents: Malondialdehyde (MDA) kit, proline (PRO) kit, soluble sugar kit, total chlorophyll kit, peroxidase (POD) kit, catalase (CAT) kit, and superoxide dismutase (SOD) kit (Beijing Solarbio Science & Technology Co., Ltd.); abscisic acid (ABA) kit (Shanghai Enzyme-Linked Biotechnology Co., Ltd.).

[0023] Example 1: Detection of growth-promoting characteristics of strain GLBv-Z4 (1) Detection of nitrogen fixation and potassium solubilization capabilities: After activation, strain GLBv-Z4 was inoculated into nitrogen fixation and potassium solubilization medium and incubated upside down in a 28 ℃ constant temperature incubator for 3–5 days. Colony growth was observed to assess its nitrogen fixation and potassium solubilization capabilities. The experiment was conducted in triplicate. Figure 2 and Figure 3 As shown, if the strain can grow normally on nitrogen-fixing and potassium-solubilizing media, then the strain has the ability to fix nitrogen and solubilize potassium.

[0024] (2) Phosphorus-solubilizing capacity test: After activation, strain GLBv-Z4 was inoculated onto PKO medium and lecithin medium, and incubated upside down in a 28℃ incubator for 3–5 days. Colony growth was observed to assess its nitrogen-fixing capacity. The experiment was conducted in triplicate. Figure 4 and Figure 5 As shown, if a transparent phosphorus-solubilizing zone is formed around the colony, then the bacterium has the ability to solubilize phosphorus. The ability of the strain to dissolve inorganic and organic phosphorus is determined by the ratio of the diameter of the transparent zone (D) to the diameter of the colony (d).

[0025] (3) Siderophore Production Capacity Assay: Siderophore production capacity was assessed using a double-layer plate method. The lower layer was MKB medium, and the upper layer was CAS medium. The strain GLBv-Z4, activated in LB medium, was inoculated onto the surface of MKB plates and incubated at 28 ℃ for 3–5 days, with three replicates per group. After significant colony growth, the plates were covered with CAS medium sterilized at approximately 50 ℃, and the colorimetric reaction was observed after 30 minutes. Figure 6 If an orange-yellow halo appears around the colony, it indicates that the strain has the ability to produce siderophores, and the level of siderophore production is detected by the ratio of the halo to the colony diameter.

[0026] (4) IAA production capacity: such as Figure 7 and Figure 8As shown, the IAA production capacity of the strain was qualitatively and quantitatively analyzed using a colorimetric method. After activation, strain GLBv-Z4 was inoculated into IAA medium at a ratio of 1:100 and cultured at 28 ℃ and 180 r / min for 2–3 days. 100 μL of the bacterial suspension was placed in a colorimetric plate, and an equal volume of Spot chromogenic solution was added. After reacting in the dark for 30 min, the color change was observed. If the solution turned red, it indicated that the strain had the ability to produce IAA, and the color intensity was positively correlated with the yield. Each experiment was repeated three times. For strains with IAA production capacity, 2 mL of the bacterial suspension was taken, centrifuged at 6000 rpm for 8 min, and 200 μL of the supernatant was collected. This supernatant was mixed with an equal volume of Spot chromogenic solution and reacted in the dark for 30 min. The absorbance was measured at 530 nm, with the culture medium serving as a blank control. IAA standard solutions of 0, 15, 30, 45, 60, 75, and 100 μg / mL were added to the blank colorimetric solution, respectively. The absorbance was measured and a standard curve was plotted to establish the IAA standard equation. Based on this, the IAA yield of strain GLBv-Z4 can be calculated to be 21.916 mg / L.

[0027] Example 2: Identification of strain GLBv-Z4 (1) 16S rRNA gene sequencing and phylogenetic analysis Centrifuge 1 mL of bacterial culture at 6000 r / min for 8 min, discard the supernatant, add 1 mL of sterile water, and mix thoroughly by pipetting. Use this mixture as a template to amplify the 16S rRNA gene of the strain using universal primers 27F (5′-AGAGTTTGATCCTGGCTCAG-3′) and 1492R (5′-GGTTACCTTGTTACGACTT-3′). The PCR product was sent to Sangon Biotech Shanghai Co., Ltd. for sequencing, and the results were analyzed by BLAST comparison on NCBI (www.ncbi.nlm.nih.gov). A phylogenetic tree was constructed using MEGA 64 software. Figure 9 It can be seen that strain GLBv-Z4 is related to small bundles of proline-phages ( Prolinoborus fasciculus CIP 103579 is the most closely related, with a similarity of 99.86%, and was identified as a small bundle of proline-phages.

[0028] (2) Salt tolerance test of strain GLBv-Z4 Prepare 100 mL of LB liquid medium with NaCl concentrations of 1%, 2%, 3%, 5%, 6%, 7%, 8%, 10%, 11%, and 12%, respectively, and inoculate each medium with bacterial culture of strain GLBv-Z4 at a 1:100 ratio (OD). 600=1.0), and three replicates were set up for each concentration. The cells were incubated at 28 ℃ with constant temperature shaking at 180 r / min, and the OD of the bacterial culture was measured at 0, 2, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 95 h. 600 .Depend on Figure 10 It can be seen that the strain grows fastest at a NaCl concentration of 1%, and the OD value reaches a maximum of 1.850 after 50 hours of growth. The maximum NaCl tolerance concentration is 11%.

[0029] (3) Detection of acid and alkali resistance of strain GLBv-Z4 Prepare 100 mL of LB liquid medium with pH values ​​of 4.5, 5, 6, 7, 8, 9, 9.5, 10, 11, 12, and 13 respectively, and inoculate each medium with bacterial culture of strain GLBv-Z4 at a 1:100 ratio (OD). 600 =1.0), and three replicates were set up for each concentration. The culture was carried out at 28 ℃ with constant temperature shaking at 180 r / min, and the OD of the bacterial culture was measured at 0, 2, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, and 80 h. 600 .Depend on Figure 11 It can be seen that the strain can grow in the pH range of 5-12. The strain does not grow at pH 4.5 and 13. The OD value reaches the maximum of 1.678 after 40 hours of growth in a medium with pH 7.

[0030] Example 3: Effects of inoculation with strain GLBv-Z4 on the growth of sugar beet seedlings under different salt concentrations Plant culture and inoculum preparation: A single colony of GLBv-Z4 was picked and inoculated into a sterile Erlenmeyer flask containing LB liquid medium. The flask was incubated overnight with shaking at 28 ℃ and 180 r / min to obtain the seed culture. 5 mL of the seed culture was inoculated into 500 mL of LB liquid medium and cultured until the OD of the inoculum was reached. 600 When the concentration is 1.0–1.2, the bacterial cells are collected by centrifugation at 6000 r / min for 5 min. The supernatant is discarded, and the cells are resuspended in an equal volume of sterile water or NaCl solution to prepare the bacterial agent for later use. Vermiculite and water are added to the breeding trays, and seeds of similar shape and size are sown in the trays to germinate. The nutrient soil and vermiculite are mixed in a 3:1 ratio, sterilized, cooled, and then divided into flower pots (10 cm long, 10 cm wide, and 12 cm high). Beetroot seedlings with uniform growth are selected and transplanted into the soil, with 6 seedlings per pot. The bacterial agent is injected into the soil around the roots of the beetroot seedlings. The control group is treated with an equal volume of sterile water or NaCl solution. The inoculum is injected once every 3 days. Samples are taken after 2 weeks of treatment to determine physiological and biochemical indicators. Root length, fresh weight, stem diameter, plant height, and leaf traits are measured after 30 days of treatment.

[0031] (1) Effects of inoculation with strain GLBv-Z4 on beet phenotype under different salt stress concentrations like Figure 12 As shown, compared with the uninoculated group, inoculation with strain GLBv-Z4 significantly promoted the growth of sugar beet seedlings at NaCl concentrations of 0, 200, and 400 mmol / L. Under normal conditions (0 mmol / L NaCl), compared with the control group (uninoculated), inoculation with strain GLBv-Z4 increased the fresh weight, plant height, root length, stem diameter, leaf length, and leaf width of sugar beet seedlings by 42.4%, 23.8%, 54.9%, 23.9%, 37.7%, and 21.8%, respectively. P <0.05)( Figure 13 - Figure 18 Under 200 mmol / L NaCl treatment, compared with uninoculated plants, the inoculation with strain GLBv-Z4 increased the fresh weight, plant height, root length, stem diameter, leaf length, and leaf width of beet seedlings by 105.6%, 17.5%, 51.9%, 34.0%, 23.0%, and 69.2%, respectively. P <0.05); Under 400 mmol / L NaCl treatment, compared with uninoculated, the inoculation with strain GLBv-Z4 increased the fresh weight, root length, leaf length, and leaf width of beet seedlings by 73.5%, 52.0%, 27.2%, and 70.3%, respectively. P <0.05), with no significant difference in stem diameter and plant height. These results indicate that inoculation with strain GLBv-Z4 can both promote the growth of sugar beet seedlings and enhance their salt tolerance.

[0032] (2) Effects of inoculation with strain GLBv-Z4 on physiological parameters of sugar beet under different salt stress concentrations Under normal conditions (0 mmol / L NaCl), compared with the control group (no inoculation), inoculation with strain GLBv-Z4 resulted in ABA (amino acid) reduction in beet seedlings. Figure 19 ), MDA Figure 20 The contents decreased by 52.8% and 36.7% respectively. P <0.05), total chlorophyll content ( Figure 23 Increased by 16.2% P <0.05), CAT, POD and SOD activities ( Figure 24 , Figure 25 , Figure 26 The increases were 62.5%, 52.3%, and 80.2% respectively. P <0.05), soluble sugars ( Figure 21 ) and PRO Figure 22 There was no significant difference in ABA and MDA content. Under 200 mmol / L NaCl treatment, compared to uninoculated seedlings, the inoculated strain GLBv-Z4 reduced the ABA and MDA content in sugar beet seedlings by 26.7% and 32.1%, respectively. P<0.05), the contents of soluble sugar, PRO, and total chlorophyll increased by 79.3%, 148.2%, and 33.3%, respectively. P <0.05), CAT and POD activities increased by 71.7% and 54.2%, respectively. P <0.05), SOD activity showed no significant difference; under 400 mmol / L NaCl treatment, compared with uninoculated, the inoculated strain GLBv-Z4 reduced the ABA and MDA contents of sugar beet seedlings by 27.8% and 21.7%, respectively, while increasing the soluble sugar and total chlorophyll contents by 58.7% and 35.5%, respectively. P <0.05), SOD activity increased by 54.0% ( P <0.05), with no significant differences in PRO content, CAT, and POD activity. These results indicate that inoculating with strain GLBv-Z4 not only alters hormone levels and accumulates soluble substances to enhance the growth and development of sugar beet seedlings, but also increases antioxidant enzyme activity to mitigate the damage caused by salt stress to sugar beet seedlings.

[0033] In summary, strain GLBv-Z4 possesses growth-promoting properties such as nitrogen fixation, phosphorus solubilization, potassium solubilization, and plant hormone production, and can survive in environments with high salt concentrations and strong acidity / alkalinity. Inoculation with strain GLBv-Z4 under salt stress can enhance root development and increase biomass. ABA inhibits plant growth and development by suppressing cell division and photosynthesis, inducing leaf senescence, delaying seed germination, and interfering with hormone balance. Excessive MDA disrupts cell membrane structure, inhibits protein and enzyme activity, induces DNA damage, and interferes with metabolic processes, leading to cellular dysfunction and decreased physiological activity, resulting in plant wilting. Inoculation with strain GLBv-Z4 can reduce the content of MDA and ABA in plant seedlings, minimizing their damage and promoting plant growth and development. Under salt stress, the accumulation of soluble substances not only maintains cellular water balance through osmotic regulation but also stabilizes biomembrane structure, protects enzyme activity, and scavenges reactive oxygen species (ROS), thus mitigating oxidative damage. Inoculation with strain GLBv-Z4 increases the accumulation of soluble substances in plant seedlings, improves cellular physiological state, enhances plant physiological metabolism and stress resistance, and promotes plant growth recovery under salt stress. Salt stress induces excessive accumulation of reactive oxygen species (ROS) in plants, causing cell membrane lipid peroxidation and metabolic disorders. Antioxidant enzyme systems play a role in scavenging hydrogen peroxide, maintaining cellular redox balance, and stabilizing membrane structure and enzyme activity, thereby mitigating oxidative damage caused by salt stress. Inoculation with strain GLBv-Z4 significantly enhances the activity of antioxidant enzymes in plants, helping to reduce MDA content, stabilize cell membrane structure, and mitigate oxidative damage, thereby improving plant resistance and physiological vitality under salt stress. Therefore, strain GLBv-Z4 can be applied to the development of microbial agents, biofertilizers, and saline-alkali land improvement products, providing new microbial resources and technical support for saline-alkali land ecological restoration and sustainable agricultural development.

[0034] It should be noted that the above embodiments of the present invention are merely illustrative of the technical principles of the invention and are not intended to limit the invention. All equivalent substitutions, variations, or improvements made in accordance with the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. Small bundle proline-phage GLBv-Z4, characterized in that, It is deposited at the China General Microbiological Culture Collection Center, with accession number CGMCC No. 35752.

2. A salt-tolerant growth-promoting bacterial agent, characterized in that: The salt-tolerant growth-promoting bacterial agent contains the small-banded proline-eating bacterium GLBv-Z4 or its bacterial solution as described in claim 1.

3. The application of the small-banded proline-eating bacterium GLBv-Z4 in growth-promoting properties according to claim 1.

4. The application of the small-banded proline-eating bacterium GLBv-Z4 according to claim 1 or the salt-tolerant growth-promoting agent according to claim 2 in promoting plant growth under salt stress.

5. The application of the small-banded proline-eating bacterium GLBv-Z4 according to claim 1 or the salt-tolerant growth-promoting agent according to claim 2 in promoting plant root development, increasing leaf area and fresh weight under salt stress.

6. The application of the small-banded proline-eating bacterium GLBv-Z4 according to claim 1 or the salt-tolerant growth-promoting agent according to claim 2 in increasing the accumulation of soluble substances in plants under salt stress.

7. The application of the small-banded proline-eating bacterium GLBv-Z4 according to claim 1 or the salt-tolerant growth-promoting agent according to claim 2 in enhancing the activity of plant antioxidant enzyme systems under salt stress.

8. The application according to claims 4, 5, 6, and 7, characterized in that, The plant in question is a sugar beet.

9. A method for improving the salt tolerance of plants, characterized in that, The small-banded proline-eating bacteria GLBv-Z4 of claim 1 or the salt-tolerant growth-promoting bacteria of claim 2 are inoculated into the root soil of beet seedlings growing in a salt environment.

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