Pseudomonas TaRb6 capable of preventing diseases and promoting growth and application of pseudomonas TaRb6

Abstract

The invention belongs to the technical field of microorganisms, and particularly relates to a pseudomonas TaRb6 capable of preventing diseases and promoting growth and application of the pseudomonas TaRb6. The TaRb6 strain provided by the invention belongs to a potential new species of pseudomonas, and the preservation number of the TaRb6 strain is CGMCC (China General Microbiological Culture Collection Center) No.36131. The strain TaRb6 and a fermentation inoculant prepared from the strain TaRb6 have good disease prevention and growth promotion functions on plants; the bacterial inhibition rate of sterile fermentation liquor of the strain TaRb6 on fusarium pseudograminearum reaches 46.54%-62.82%, and the bacterial colony diameter of the fusarium pseudograminearum can be reduced by 61.38% through metabolized volatile organic compounds of the strain TaRb6. After the TaRb6 bacterial suspension is used for seed soaking treatment of wheat, the incidence rate of wheat basal stem rot can be remarkably reduced, and the growth vigor of wheat can be promoted. In addition, the strain TaRb6 has broad-spectrum antibacterial ability, and the antibacterial rate of the strain TaRb6 on pathogenic bacteria of fusarium, botrytis cinerea, apical cyst and xanthomonas reaches 47.23%-67.02%.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a disease-preventing and growth-promoting Pseudomonas TaRb6 strain and its applications. Background Technology

[0002] Wheat crown rot, also known as crown rot, is a newly emerging and rapidly spreading plant disease. First reported in Australia in 1951, it has since occurred in major wheat-producing regions worldwide, including Asia, Africa, North America, South America, and Oceania. Since its initial report in Jiangsu Province, my country in 1996, it has rapidly become a significant disease in wheat-growing areas such as the Huang-Huai-Hai Plain, and shows a continuing trend of spread. When wheat is infected with crown rot, the base of the stem is damaged, hindering normal growth and development. In severe cases, it can lead to a significant decrease in wheat yield, or even total crop failure. Especially in rainy years, the incidence and severity of crown rot increase, potentially reducing wheat yield by about 10% to 20%, and in severely affected areas, yield reductions can even climb to 50%. This disease not only reduces wheat yield and quality, but the accumulation of toxins in the wheat ear can also seriously affect the health of humans and livestock, posing a serious threat to food security.

[0003] Currently, a complete and effective control technology system for wheat stem rot has not yet been established. Traditional control methods are difficult to achieve long-term and efficient control of the disease and are prone to exerting targeted selection pressure on the pathogen, thereby accelerating its genetic variation process and inducing mutant strains with stronger pathogenicity or drug resistance. At the same time, with the increasing global demand for food security, exploring innovative green control technologies has become a research hotspot in this field and has attracted widespread attention from academia and industry.

[0004] With the growing acceptance of the concept of sustainable agricultural development, biological control methods are playing an increasingly important role in plant disease control. The core of biological control is utilizing inter-organism relationships to inhibit or eliminate harmful organisms. Biological control not only effectively suppresses the development of pathogenic microorganisms, but more importantly, it does not pollute the environment or affect human health, thus possessing broad development prospects. Compared with chemical control, biological control is more in line with the requirements of ecological civilization and sustainable development. Previous studies have found that plant rhizosphere soil is a cradle for the growth of biocontrol strains, and researchers both domestically and internationally tend to screen biocontrol strains from plant rhizosphere soil, such as Bacillus (Bacillus). Bacillus spp.), Pseudomonas ( PseudomonasVarious plant probiotics, including *Pseudomonas* spp., have shown good disease prevention and growth-promoting effects. Among them, *Pseudomonas*, as one of the core microorganisms in the wheat rhizosphere, plays a crucial role in maintaining wheat health. However, the application of *Pseudomonas* in the biocontrol of wheat stem rot is still relatively limited, especially lacking highly efficient, multifunctional strains. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a disease-preventing and growth-promoting strain of *Pseudomonas* TaRb6 and its applications. This invention provides a strain of *Pseudomonas* (… Pseudomonas The new species TaRb6 strain (sp.) has good disease prevention and growth promotion effects, especially in effectively preventing wheat stem rot and promoting wheat growth.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows: The first aspect of this invention provides a disease-preventing and growth-promoting Pseudomonas TaRb6, which is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36131.

[0007] A second aspect of the present invention provides a fermentation agent, characterized in that the fermentation agent is a bacterial suspension, sterile fermentation broth, bacterial fermentation broth, or metabolite of Pseudomonas TaRb6 as described above.

[0008] Furthermore, the sterile fermentation broth contains antibacterial active substances secreted by Pseudomonas TaRb6; the metabolites are antibacterial active substances secreted by Pseudomonas TaRb6.

[0009] The bacterial fermentation broth is prepared by the following steps: inoculating the Pseudomonas TaRb6 in LB medium and culturing at 26℃~30℃ for 48h~72h to obtain the bacterial fermentation broth.

[0010] Furthermore, the viable count of Pseudomonas TaRb6 in each milliliter of the fermentation broth is 1 × 10⁻⁶. 9 CFU ~ 2.5 × 10 9 CFU.

[0011] Furthermore, the sterile fermentation broth is obtained by filtering and sterilizing the bacterial fermentation broth.

[0012] A third aspect of the present invention provides the application of the aforementioned Pseudomonas TaRb6 or fermentation agent in the prevention and control of plant pathogenic diseases.

[0013] Furthermore, the plant pathogen is any one or more of the following: Fusarium graminearum, Fusarium pseudograminearum, Fusarium asiaticum, Fusarium oxysporum watermelon-specific type, Fusarium oxysporum Cuban-specific type, Botrytis cinerea, Gramineae, and Xanthomonas chinensis.

[0014] Furthermore, the disease is wheat stem base rot.

[0015] The fourth aspect of the present invention provides an application of the above-mentioned Pseudomonas TaRb6 or fermentation agent in promoting plant growth: the bacterial suspension is used to soak the plants to be treated, spray the plants, or drench the roots after transplanting the seedlings.

[0016] Furthermore, the viable count of Pseudomonas TaRb6 in the bacterial suspension is 1 × 10⁻⁶. 6 CFU~1×10 8 CFU.

[0017] Furthermore, the bacterial suspension is obtained by diluting the bacterial fermentation broth.

[0018] Furthermore, the plant in question is wheat.

[0019] Furthermore, the application is to promote wheat root growth.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, a strain TaRb6 was isolated and screened, with the preservation number CGMCC No. 36131. ​​Further identification revealed that this strain had the highest ANI value of 92 with *Pseudomonas kanran*. However, based on the species-level classification threshold, it can be determined that strain TaRb6 does not belong to *Pseudomonas kanran*, and this strain is judged to be a potential *Pseudomonas* species. Pseudomonas A new species (spp.) has been discovered, further enriching the new resources of beneficial Pseudomonas bacteria.

[0021] (2) This invention also provides a fermentation agent, which is a bacterial suspension, sterile fermentation broth, bacterial fermentation broth, or metabolites of Pseudomonas TaRb6. Experiments show that strain TaRb6 and its prepared fermentation agent have good disease prevention and growth promotion functions for plants. The inhibition rate of different concentrations of sterile fermentation broth against Fusarium graminearum can reach 46.54%~62.82%, and its volatile organic compounds can reduce the colony diameter of Fusarium graminearum by 61.38%. In pot experiments, after soaking wheat seeds with TaRb6 bacterial suspension, the wheat growth in the treatment group was better than that in the control group, and the incidence of stem rot disease was significantly reduced. In addition, strain TaRb6 is effective against common plant pathogens: Fusarium graminearum ( F . grasses ), Fusarium tumefaciens ( F . AsianFusarium oxysporum watermelon-specific type ( F . oxysporum f. sp. snowy Fusarium oxysporum Cuban-specific type ( F . oxysporum f. sp. from Cuba Botrytis cinerea ( ), Botrytis cinerea ( Botrytis cinerea ), chrysanthemum husk ( Gaeumannomyces grass ) and wild rapeseed xanthomonium ( Xanthomonas campestris It has antagonistic ability, with an inhibition rate of 47.23%~67.02%. This strain and its fermentation agent can not only effectively prevent diseases, but also promote wheat growth, and can be used for plant disease prevention and growth promotion.

[0022] Instructions for the Preservation of Biological Materials The TaRb6 strain in this invention is classified and named as follows: Pseudomonas sp., Latin name is Pseudomonas sp. was deposited on September 30, 2025, at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36131. ​​The address of the depository is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, 100101, China. Attached Figure Description

[0023] 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.

[0024] Figure 1 The results of the confrontation culture between strain TaRb6 and the pathogen are shown. Figure 1 The pathogens in A, B, C, D, E, F, G, and H are, in order, Fusarium pseudobulbarum (…). F . pseudograsses Fusarium graminearum ( ), Fusarium graminearum F . grasses ), Fusarium tumefaciens ( F . Asian Fusarium oxysporum watermelon-specific type ( F . oxysporum f. sp. snowy Fusarium oxysporum Cuban-specific type ( F . oxysporum f. sp. from Cuba ), chrysanthemum husk ( Gaeumannomyces graminis Botrytis cinerea ( ), Botrytis cinerea ( Botrytis cinerea ) and wild rapeseed xanthomonium ( Xanthomonas campestrisIn each plate, the pathogen is located in the center, and strain TaRb6 is located on both sides.

[0025] Figure 2 The plate inhibition rate of strain TaRb6 against different pathogenic fungi is shown.

[0026] Figure 3 To detect the production of ironophile, amylase, and cellulase by strain TaRb6, Figure 3 A, B, and C in the table represent the results of the detection of iron-producing enzymes, amylase, and cellulase, respectively.

[0027] Figure 4 To construct based on 16S rRNA gene sequence Pseudomonas Phylogenetic tree of sp. TaRb6.

[0028] Figure 5 The effect of different concentrations of aseptic fermentation broth of strain TaRb6 on the growth of Fusarium pseudograss. Figure 5 In the table, A represents the plate antagonistic effect, and (a), (b), (c), and (d) represent sterile fermentation broths with concentrations of 5%, 10%, and 20%, respectively, and the control group. Figure 5 In this context, B represents the diameter of the colony. Figure 5 C in the figure represents the antibacterial rate.

[0029] Figure 6 The inhibitory effect of the metabolites (volatile organic compounds) of strain TaRb6 on Fusarium pseudobulbarum was investigated. Figure 6 In the diagram, A represents the control group treated with blank LB medium. Figure 6 In the diagram, B represents the experimental group treated with volatile organic compounds by strain TaRb6.

[0030] Figure 7 The effect of TaRb6 bacterial suspension soaking on wheat stem base rot was investigated. Figure 7 In the diagram, A represents the group that was immersed in LB broth alone. Figure 7 B in the text refers to the group that was soaked in TaRb6 bacterial suspension alone. Figure 7 C in the text represents the group treated with TaRb6 bacterial suspension soaked and inoculated with Fusarium graminearum. Figure 7 D in the diagram represents the LB-treated group that was inoculated with Fusarium graminearum. Detailed Implementation

[0031] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0032] The watermelon-specific Fusarium oxysporum strain of this invention ( F . oxysporum f. sp. snowy ) and Fusarium oxysporum Cuban-specific type ( F . oxysporum f. sp. from Cuba (This was a gift from Dr. Zhang Xiaoxiao of Guangxi University) Fusarium pseudograss ( F . pseudograsses For strain information, see: Hou Ying, Xin Hewen, Zhang Xin, et al. Sensitivity of Fusarium graminearum in wheat of Henan Province to flutriafol. Acta Phytopathologica Sinica, 2023, 53(2): 307-316. Fusarium graminearum ( F . grasses For strain information, see: Zhao Meirong, Li Yongchun, Zhang Zhichao. Screening and identification of a biocontrol strain antagonistic to Fusarium graminearum. Jiangsu Agricultural Sciences, 2024, 52(11): 128-133. Fusarium anaeroides (Asian Fusarium) F . Asian For strain information, please refer to: Zhao Qin, Zhang Xiangxiang, Deng Yuanyu, et al. Histopathological observation of Fusarium oxysporum Asiatum infection in resistant and susceptible wheat varieties. Acta Phytopathologica Sinica, 2017, 47(2): 203-213. Botrytis cinerea ( Botrytis cinerea For strain information, please refer to: Zhao Xinbei, Wang Juan, Shangguan Nini, et al. Identification, fermentation condition optimization and control effect of TD-7 biocontrol bacteria for tomato gray mold. Chinese Journal of Biological Control, 2019,(2): 226-239. Gramineae ( Gaeumannomyces graminis For strain information, please refer to: Yang Chunyun, Deng Yuanyu, Li Wei, et al. Screening and identification of biocontrol bacteria for wheat take-all disease. Chinese Journal of Biological Control, 2018, 34(6): 873-881. Wild rapeseed yellow monoclonal ( Xanthomonas campestrisFor strain information, see: Qu Jia, Sun Xiaoyu, Zhao Lingxia, et al. Identification and antibacterial activity determination of Streptomyces YNF36, a biocontrol agent against black spot disease of walnut. Bulletin of Microbiology, 2022, 49(11): 4727-4739.

[0033] Wheat stem rot can lead to a significant decrease in wheat yield, or even total crop failure, especially in rainy years when the incidence and severity increase, with yield reductions reaching 10% to 50%. It can also cause toxin accumulation in the wheat ear, seriously affecting human and livestock health and threatening food security. Currently, traditional control methods are difficult to achieve long-term, high-efficiency control and easily induce drug-resistant strains. With the deepening of the concept of sustainable agricultural development, the importance of biological control methods is increasingly prominent, especially the use of biocontrol strains in the plant rhizosphere, such as Bacillus and Pseudomonas. However, the application of Pseudomonas in the biological control of wheat stem rot is still limited, especially lacking highly efficient and multifunctional strains.

[0034] This invention provides a TaRb6 strain for disease prevention and growth promotion, a fermentation broth, a biocontrol agent, and their applications. A TaRb6 strain was isolated and screened, and identification results showed that the TaRb6 strain belongs to a potential new species of the genus *Pseudomonas*. The TaRb6 strain, its prepared fermentation broth, and the biocontrol agent exhibit good disease prevention and growth promotion functions in plants. Experiments show that different concentrations of sterile fermentation broth can achieve an inhibition rate of 46.54%–62.82% against *Fusarium graminearum*, and its metabolic volatile organic compounds can reduce the colony diameter of *Fusarium graminearum* by 61.38%. Soaking wheat seeds with a TaRb6 bacterial suspension significantly reduces the incidence of wheat stem rot and promotes wheat growth. Furthermore, strain TaRb6 has broad-spectrum antibacterial activity, achieving inhibition rates of 47.23%–67.02% against pathogens of the genera *Fusarium*, *Botrytis*, *Xanthomonas*, and *Xanthomonas*.

[0035] Example 1: Isolation and screening of Fusarium pseudobolus antagonistic strain TaRb6 *Fusarium graminearum* is one of the main pathogens of wheat basal rot, infecting the base of wheat stems, leading to disease, affecting wheat growth, and causing a decline in yield and quality. This invention collected 28 wheat rhizosphere soil samples from multiple regions and used a gradient dilution plating method to isolate 346 culturable bacterial strains with significant differences in morphology and color. Using the plate confrontation method for initial screening and secondary verification, a strain exhibiting optimal plate inhibition activity against *Fusarium graminearum* was obtained and named TaRb6.

[0036] Meanwhile, in order to screen for broad-spectrum and highly effective biocontrol strains to simultaneously protect wheat from multiple diseases, *Fusarium graminearum* (…) was selected. F . pseudograsses Fusarium graminearum ( ), Fusarium graminearum F. grasses ), Fusarium tumefaciens ( F . Asian Fusarium oxysporum watermelon-specific type ( F . oxysporum f. sp. snowy Fusarium oxysporum Cuban-specific type ( F . oxysporum f. sp. from Cuba Botrytis cinerea ( ), Botrytis cinerea ( Botrytis cinerea ), chrysanthemum husk ( Gaeumannomyces grass ) and wild rapeseed xanthomonium ( Xanthomonas campestris Using pathogens as targets, the antagonistic effect of strain TaRB6 against different pathogens was determined by the plate confrontation method.

[0037] like Figure 1 and Figure 2 As shown, the experimental results indicate that strain TaRb6 exhibits significant antagonistic activity against various pathogenic fungi of the genera *Fusarium*, *Botrytis*, and *Tetranychus*, as well as *Xanthomonas spp.* It shows strong inhibitory effects against various *Fusarium* species, with inhibition rates ranging from 49.53% to 67.02%. Furthermore, it also shows significant inhibitory effects against *Xanthomonas spp.*, although the activity is relatively weak, with an inhibition zone radius of only 3.33 mm ± 1.15 mm. This demonstrates that strain TaRb6 is a broad-spectrum and excellent antagonistic bacterium.

[0038] Example 2: Determination of enzyme production activity of strain TaRb6 This invention utilizes selective culture media to detect plant growth-promoting characteristics of strain TaRb6, and the results are as follows: Figure 3 As shown, a clear hydrolysis zone was observed around the inoculated colony on CAS medium solid medium, but no hydrolysis zone was produced on starch medium and cellulase-producing solid medium, proving that the strain has the ability to produce ferophiles.

[0039] Example 3: Systematic identification of strain TaRb6 Strain TaRb6 forms regular, round colonies on LB agar plates. The surface is smooth and wrinkle-free, and the colonies are moist and viscous. Newly formed colonies are milky white, gradually darkening to yellowish-white after 48 hours. The colonies produce a pale green fluorescent pigment on King's B medium, with more pronounced fluorescence under ultraviolet light.

[0040] Table 1. Physiological and biochemical characteristics of strain TaRb6 Note: In the table, "+" indicates positive and "-" indicates negative.

[0041] The results of the physiological and biochemical index tests in Table 1 show that strain TaRb6 is positive for oxidase and catalase reactions, cannot hydrolyze gelatin, can grow normally in NaCl solution with a mass concentration of ≤5%, can produce arginine hydrolase, can utilize D-mannitol, D-serine, and citrate, but cannot utilize phenylethylamine, is positive for nitrate reduction, is resistant to ampicillin sodium, but sensitive to kanamycin.

[0042] All of the above results are consistent with those of Pseudomonas aeruginosa ( Pseudomonas (sp.) have similar physiological and biochemical characteristics.

[0043] Genomic DNA was extracted from strain TaRb6, and the 16S rRNA gene sequence of strain TaRb6 was amplified by PCR using universal primers 27F and 1492R. Multiple sequence alignment revealed that the 16S rRNA gene sequence of strain TaRb6 was consistent with that of strain [unclear - likely a specific strain or strain]. Pseudomonas koreensis LMG 21318 T The highest consistency was observed, reaching 99.25%. Further phylogenetic tree analysis using MEGA-X software confirmed that strain TaRb6 was similar to the model strain. P . Korean LMG 21318 T Clustered into a branch ( Figure 4 (This can identify strain TaRb6 as related to...) P . Korean The closest kinship.

[0044] Based on the morphological and physiological-biochemical identification results of the two strains, it is preliminarily inferred that strain TaRb6 is Pseudomonas koreanum.

[0045] Considering the conservation of the 16S rRNA gene, to more accurately identify the taxonomic position of TaRb6, whole-genome sequencing was performed on strain TaRb6. The full-length genome of strain TaRb6 is 6244441 bp, with a G+C content of 60.26%. By calculating the average nucleotide similarity (ANI) between this strain and closely related species, it was found that the strain is similar to... P . Korean LMG 21318 T The ANI value was the highest, but only 92.08 (Table 2). However, based on the species-level classification threshold (ANI value ≤ 95%: classified as different species), it can be determined that strain TaRb6 does not belong to Pseudomonas koreanum, and it is speculated that this strain is a potential new species of Pseudomonas.

[0046] Table 2 Pseudomonas ANI analysis of sp. TaRb6 and the Pseudomonas type species Example 4: A bacterial fermentation broth, prepared by the following steps: Freshly cultured strain TaRb6 was inoculated onto LB liquid medium and cultured with shaking at 28℃ and 200 r / min for 48 h to obtain a viable fermentation broth. The viable count concentration of Pseudomonas TaRb6 in the fermentation broth was approximately 1.5 × 10⁻⁶. 9 CFU / mL.

[0047] Example 5: A bacterial fermentation broth, prepared by the following steps: Freshly cultured strain TaRb6 was inoculated into LB liquid medium and cultured with shaking at 26℃ and 200 r / min for 48 h to obtain a viable fermentation broth. The viable count concentration of Pseudomonas TaRb6 in the viable fermentation broth was approximately 1 × 10⁻⁶. 9 CFU / mL.

[0048] Example 6: A bacterial fermentation broth, prepared by the following steps: Single colonies of freshly cultured strain TaRb6 were inoculated into LB liquid medium and cultured with shaking at 30℃ and 200 r / min for 72 h to obtain a viable fermentation broth. The viable count concentration of Pseudomonas TaRb6 in the viable fermentation broth was approximately 2.5 × 10⁻⁶. 9 CFU / mL.

[0049] Since Examples 4 to 6 have similar effects, for the convenience of subsequent discussion and reference, the bacterial fermentation agent prepared in Example 4 will be used as an example for further investigation.

[0050] Example 7: Antibacterial activity of sterile fermentation broth of Pseudomonas TaRb6 Preparation of sterile fermentation broth: The bacterial fermentation broth prepared in Example 4 was centrifuged at 12000 r / min at room temperature for 2 min. The supernatant was collected and filtered through a 0.22 μm filter membrane to remove bacteria, thus obtaining sterile fermentation broth.

[0051] Aseptic fermentation broth was added to melted PDA medium at volume ratios of 5%, 10%, and 20%, respectively. After thorough mixing, the mixture was poured into plates. LB liquid medium with a final concentration of 20% was added as a control. Each treatment had three biological replicates. After the medium solidified, a 5 mm diameter Fusarium oxysporum mycelium was inoculated in the center of the plate and incubated at 25°C. Colony growth was observed and recorded daily. The inhibition rate was calculated when the diameter of the pathogen colony in the control group reached 3 / 4 of the petri dish area.

[0052] Inhibition rate / % = (diameter of control group - diameter of treatment group) / (diameter of control group - diameter of mycelium cake) × 100%.

[0053] After 5 days of cultivation, when the colony diameter of the pathogen in the control group reached 82.38 mm ± 1.35 mm, the 5%, 10%, and 20% sterile fermentation broth in the treatment groups all significantly inhibited the mycelial growth of *Fusarium graminearum*, with corresponding inhibition rates of 46.54%, 53.8%, and 62.82%, respectively. Figure 5 The experimental results showed that the sterile fermentation broth prepared by strain TaRb6 inhibited the mycelial growth of Fusarium pseudograss, and the antibacterial effect increased with the increase of the concentration of sterile fermentation broth.

[0054] Example 8: Antibacterial activity of antagonistic strain TaRb6 metabolites (volatile organic compounds) The plate-on-plate test was used to investigate whether the volatile organic compounds of the antagonistic strain TaRb6 inhibited the mycelial growth of Fusarium pseudograss.

[0055] Preparation of TaRb6 bacterial suspension: The fermentation broth prepared in Example 4 was diluted to a viable count concentration of Pseudomonas TaRb6 of 1 × 10⁻⁶. 8 CFU / mL was used to obtain a TaRb6 bacterial suspension.

[0056] Add TaRb6 bacterial suspension to the melted LB medium at a volume ratio of 1%, mix thoroughly, and pour into plates. Inoculate a 5 mm diameter Fusarium graminearum mycelium cake in the center of a PDA medium plate, invert the two plates together and seal, and set up a blank LB medium as a control. Each treatment has 3 biological replicates. Incubate at 25℃, observe and record colony growth daily. When the colony diameter in the control group reaches 3 / 4 of the petri dish area, calculate the inhibition rate. The formula for calculating the inhibition rate is the same as in Example 7.

[0057] The experimental results showed that in the control group, *Fusarium graminearum* colonies grew rapidly, with a diameter of 53.33 mm ± 0.58 mm when the colonies covered 3 / 4 of the petri dish. In contrast, the TaRb6 suspension treatment group significantly inhibited the mycelial expansion of the pathogen, with a colony diameter of only 23.67 mm ± 12.34 mm, achieving an inhibition rate of 61.38%. Figure 6 (and Table 3).

[0058] Table 3. Inhibition rate of volatile organic compounds (VOCs) of strain TaRb6 against Fusarium pseudobulbarum. The TaRb6 bacterial suspension not only produces diffusible substances that significantly inhibit the growth of Fusarium pseudograss hyphae, but may also interfere with the development of pathogenic hyphae through volatile metabolites. This result demonstrates that strain TaRb6 has multiple biocontrol mechanisms, providing a basis for further investigation into its underlying mechanisms.

[0059] Example 9: Effects of strain TaRb6 on wheat growth promotion and stem rot control Preparation of pathogenic fungal conidial suspension: Five fungal cakes were collected from the edge of *Fusarium graminearum* colonies using a 5 mm punch. These cakes were inoculated into Erlenmeyer flasks containing 50 mL of 3% mung bean soup medium and cultured on a shaker at 25°C and 200 r / min for 5 days. Mycelium was removed by filtration through four layers of sterile gauze. The conidial precipitate was obtained by centrifugation. The conidia were collected and resuspended in 3% mung bean soup medium. Counting was performed using a hemocytometer. The medium was then diluted to a concentration of 1 × 10⁻⁶. 6 1 conidia / mL.

[0060] Wheat seed surface disinfection: Select plump wheat seeds and soak them in a 2% NaClO solution for 2 minutes for surface disinfection, followed by rinsing three times with sterile water. The surface-disinfected seeds were divided into four treatment groups: soaking alone in the TaRb6 bacterial suspension prepared in Example 8 (denoted as TaRb6 group), soaking in the TaRb6 bacterial suspension followed by root irrigation with a pathogen conidia suspension (denoted as TaRb6+). F . pseudograsses Group 1), LB culture medium soaking alone (referred to as LB group), and LB culture medium soaking followed by root irrigation with pathogen conidia suspension (referred to as LB+). F . pseudograsses (Groups). Each treatment lasted 30 minutes. After air drying, the seeds were planted in 9 cm diameter pots at a density of 15 seeds per pot, with 5 pots planted per treatment. Cultivation and management were carried out under standardized culture conditions in an artificial climate chamber (light / dark duration 16 / 8 h, relative humidity 65%, temperature 25℃).

[0061] Efficacy test of wheat growth promotion and stem base rot control: When wheat grows to the one-leaf-one-heart stage, the two treatment groups that need to be inoculated with the pathogen were each inoculated with 20 mL of 1×10⁻⁶ solution via root irrigation. 6 One conidia / mL; the other two treatment groups were each inoculated with an equal volume of 3% mung bean soup medium to observe the growth-promoting effect of strain TaRb6 on wheat. After continuous observation for 30 days, the incidence and severity of wheat stem rot were systematically counted, and the disease index and control effect were calculated; at the same time, the growth of wheat in the two treatment groups that were not inoculated with the pathogen was observed.

[0062] The disease severity grading criteria are as follows: Grade 0, no symptoms; Grade 1, browning of the blastodisc nodes; Grade 2, browning of the blastodisc nodes, subsoil stems, and leaf sheaths; Grade 3, dry and rotten stems; Grade 4, withered seedlings or rotten seeds.

[0063] Disease index = (∑(disease level × corresponding number of diseased plants)) / (highest disease level × total number of plants investigated) × 100.

[0064] Prevention and control effect / % = (disease index of control group - disease index of treatment group) / disease index of control group × 100%.

[0065] Table 4 Pseudomonas The control effect of sp. TaRb6 on wheat sheath blight The results showed that, in both uninoculated groups, wheat treated with TaRb6 bacterial suspension showed significantly better growth than the control group, with a significantly increased stem base diameter and more vigorous root system, indicating that strain TaRb6 can promote wheat seedling growth. Furthermore, treatment with TaRb6 bacterial suspension significantly reduced the incidence and severity of wheat stem base rot. Figure 7 (See Table 4). The disease incidence and disease index of wheat pretreated with TaRb6 bacterial suspension were only 16.00% and 4.85, respectively, while those of wheat not treated with TaRb6 bacterial suspension reached 82.67% and 17.67, respectively. Calculations show that the indoor control efficacy of TaRb6 bacterial suspension seed soaking against wheat stem rot reached 72.55%, proving that Pseudomonas TaRb6 has good disease control effects and is a biocontrol strain with good application prospects.

[0066] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A strain of Pseudomonas TaRb6 that promotes disease prevention and growth, characterized in that, The Pseudomonas TaRb6 strain is deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36131.

2. A fermentation agent, characterized in that, The fermentation agent is a bacterial suspension, sterile fermentation broth, bacterial fermentation broth, or metabolite of Pseudomonas TaRb6 as described in claim 1.

3. The fermentation agent according to claim 2, characterized in that, The bacterial fermentation broth is prepared by the following steps: inoculating the Pseudomonas TaRb6 into LB medium and culturing at 26℃~30℃ for 48h~72h to obtain the bacterial fermentation broth.

4. The fermentation agent according to claim 2, characterized in that, The viable count of Pseudomonas TaRb6 in each milliliter of the fermentation broth was 1 × 10⁻⁶. 9 CFU ~ 2.5 × 10 9 CFU.

5. The fermentation agent according to claim 2, characterized in that, The sterile fermentation broth is obtained by filtering and sterilizing the bacterial fermentation broth.

6. The application of the Pseudomonas TaRb6 of claim 1 or the fermentation agent of claim 2 in the prevention and control of plant pathogenic diseases.

7. The application according to claim 6, characterized in that, The plant pathogens are any one or more of the following: Fusarium graminearum, Fusarium pseudograminearum, Fusarium asiaticum, Fusarium oxysporum watermelon-specific type, Fusarium oxysporum Cuban-specific type, Botrytis cinerea, Gramineae, and Xanthomonas chinensis.

8. The application according to claim 6, characterized in that, The disease in question is wheat stem base rot.

9. The application of the *Pseudomonas TaRb6* of claim 1 or the fermentation agent of claim 2 in promoting plant growth, characterized in that, The bacterial suspension is used to soak the plants to be treated, spray the plants, or irrigate the roots after transplanting the seedlings.

10. The application according to claim 9, characterized in that, The viable count of Pseudomonas TaRb6 in the bacterial suspension was 1 × 10⁻⁶. 6 CFU~1×10 8 CFU; The plant in question is wheat.

Images