An endophytic dispersible pantothecin X24004 strain of maize and its application

Abstract

This invention discloses an endophytic dispersible pantothecin strain X24004 from maize and its applications. The dispersible pantothecin strain of this invention (… Pant disperse X24004, with its preservation number CGMCC No. 34510, exhibits strong antagonistic effects against various pathogenic fungi, including *Fusarium graminearum* (causal agent of corn stem rot), *Fusarium verticillatum* (causal agent of corn ear rot), and *Pythium styracifolium* (causal agent of corn stem rot). It demonstrates high efficiency and broad-spectrum control of plant fungal diseases while also promoting corn plant growth. It is a broad-spectrum biological agent, bio-fertilizer, and seed treatment agent with promising development and application prospects.

Description

Technical Field

[0001] This invention belongs to the field of biological control technology for plant diseases, specifically relating to an endophytic dispersible pantothecin X24004 of maize and its application. Background Technology

[0002] Maize stalk rot (MSR), also known as maize stem rot or bacterial wilt, is caused by single or combined infections of various pathogens. Infection points are primarily located at the roots and base of the stem, and it can occur throughout the entire growth and development period of the plant. The incidence rate is generally 10%-15%, but can reach 80% in severe cases, and under suitable conditions, it can even cause complete crop failure. Furthermore, the severity of the disease is increasing year by year. In recent years, due to straw return to the field leading to the accumulation of pathogens, and the prevalence of susceptible maize varieties and large-scale monoculture, maize stalk rot has become one of the major diseases in maize-growing areas of China, alongside maize leaf spot, maize head smut, and maize head smut.

[0003] Studies have shown that the pathogens causing maize stalk rot are influenced by various factors and conditions, and the types of pathogens vary significantly under different geographical environments and climatic conditions. In China, the main pathogen causing maize stalk rot is *Fusarium* (*Fusarium* spp.). Fusarium spp.) and Pythium genus ( Pythium spp.), Fusarium graminearum ( F. graminearum Currently, *Fusarium graminearum* is the dominant isolated pathogen causing corn stalk rot, capable of infecting the stems, stem bases, and roots of cereal crops such as corn. Corn stalk rot caused by *Fusarium graminearum* not only leads to reduced corn yields but also produces large amounts of toxins that threaten human and animal health, seriously impacting the development of the corn industry.

[0004] Currently, the most effective control method for maize stalk rot is seed coating. Seed treatment agents chosen primarily include 3.5% fludioxonil-metalaxyl suspension, 25% iprodione-thiram wettable powder, and 58% metalaxyl-thiram wettable powder. These agents show good control effects against maize stalk rot, reducing the incidence of the disease by 80%. They do not inhibit maize seed emergence or seedling growth and can even promote yield. Although chemical pesticides are currently the most commonly used pathogen control measure, this method may lead to the overuse of agricultural chemicals and chemical residues in agricultural products, resulting in both economic and environmental drawbacks.

[0005] Therefore, control methods are increasingly focusing on biological control, exploring the use of microorganisms and their secondary metabolites for disease control, promoting plant growth, increasing crop yield, and ultimately seeking sustainable green development. This indicates that the research and use of biological agents is a promising control method. Studies have shown that microorganisms can be used for the biological control of maize stalk rot. Inoculating diseased maize fields with *Trichoderma harzianum* strains can control stalk rot through multiple mechanisms, including fungal parasitism, induction of systemic resistance, enhancement of the maize rhizosphere microbiota, and improvement of soil fertility. The metabolites of *Trichoderma harzianum* can synthesize selenium and titanium dioxide, which can then be made into nanoparticles for use against *Fusarium oxysporum* (a type of spore). F. culmorum Control of Fusarium spore rot in maize. Some isolates of Bacillus can produce lysins such as glucanase, protease, or chitinase, as well as siderophores and auxins. This suggests that they may act as antagonists to inhibit Fusarium-induced stalk rot in maize. Some cyclic lipopeptides produced by Bacillus methyltrophicus TA-1 can cause Fusarium graminearum (Cephalospora graminearum) to stalk rot. F. graminearum The cell walls of microorganisms degrade, allowing them to invade pathogen cells and release their contents. This process can serve as an effective alternative to chemical fungicides in maize cultivation. Using microorganisms for the control of related diseases offers lower economic costs, higher cost-effectiveness, and greater safety. Furthermore, the broad-spectrum antifungal activity of microorganisms and their metabolites makes the exploration and exploitation of microbial resources a more attractive research direction at present.

[0006] Vascular tissue, as an efficient long-distance transport system, is driven by the hydrostatic pressure gradient between roots and branches. This driving force ensures the smooth transport of solutes and signals between plant organs. Furthermore, the pores in the perforated plates between xylem units are large enough to allow bacteria to pass through. Studies have shown that some systemic bacterial colonies can diffuse into the aboveground plant compartments via transpiration-driven xylem flow. Research has characterized the bacterial community inhabiting olive xylem sap using culture-dependent and independent methods, finding *Sphingomonas* to be the most representative genus. However, little is known about the functional relationship between the xylem microbial community and plant growth and development.

[0007] Maize specifically recruits a core microbial community in its xylem sap, which is conserved across environmental conditions and genotypes. This core microbial community promotes plant nitrogen nutrition through biological nitrogen fixation and root development. The interaction mechanisms and functions between the xylem sap microbial community and the host require further investigation. This core microbial community may be a promising resource for developing alternative microbial biotechnologies to improve the performance of sustainable agricultural crops. Studies have shown that the dominant γ-Proteobacterial OTUs in xylem tissue sap (VE) are Enterobacteriaceae, Erwiniaceae, and Pseudomonasceae, while Burkholderiaceae dominate the stem (SE) population. Klebsiella and Pantotheca are the dominant microbial groups in VE. Summary of the Invention

[0008] The technical problem to be solved by this invention is to overcome the gap in the existing technology for biological control methods of Fusarium stalk rot, a soil-borne disease of maize (caused by Fusarium graminearum), and to provide a maize endophytic bacterium, Panadol (… Pantoea dispersa X24004 (CGMCC No. 34510, deposit date: May 12, 2025, depositary code: CGMCC-China General Microbiological Culture Collection Center) and its applications. Strain X24004, isolated from the xylem tissue sap of maize, exhibits significant inhibitory activity against the pathogen Fusarium graminearum, demonstrating highly efficient and broad-spectrum antibacterial activity.

[0009] The experimental results of this invention show that dispersible pan-mycelium X24004 is effective against Fusarium graminearum, the pathogen of maize stalk rot. Fusarium graminearum This strain exhibits strong inhibitory effects on the mycelial growth of *Fusarium verticillatum*, the pathogen of corn ear rot. Fusarium verticillioides ), Pythium stalk rot pathogen of corn (Pythium spp.) Pythium arrhenomanes It exhibits strong antagonistic effects against various pathogenic fungi, with inhibition rates ranging from 44.72% to 59.70%. Strain X24004 demonstrates high efficiency and broad-spectrum control over plant fungal diseases, while also promoting maize plant growth, thus possessing certain application value and potential in the biological control of plant fungal diseases.

[0010] The first objective of this invention is to provide a strain of dispersible pantothenic acid (PVA) Pantoea dispersa X24004, with accession number CGMCC No. 34510.

[0011] A second object of the present invention is to provide a biological agent containing the aforementioned *Umbrella dispersans* X24004, a culture of the aforementioned *Umbrella dispersans* X24004, and / or metabolites obtained from culturing the aforementioned *Umbrella dispersans* X24004 as active ingredients.

[0012] Preferably, the culture of dispersible pantothenic acid X24004 is prepared by the following method: dispersible pantothenic acid X24004 is inoculated into LB liquid medium and cultured to obtain the culture of dispersible pantothenic acid X24004.

[0013] Preferably, the LB liquid medium culture is carried out under the following conditions: 28°C and 150-200 rpm for 18-24 h.

[0014] A third objective of this invention is to provide a bio-fertilizer containing the aforementioned dispersed pantothecin X24004 and fertilizer.

[0015] A fourth objective of this invention is to provide a seed treatment agent containing the aforementioned Pantothecin X24004 dispersible fungicide, fludioxonil, and seed coating agent excipients.

[0016] A fifth object of the present invention is to provide the use of the said dispersible pantothecin X24004 or the said biological agent in at least one of the following (1)-(2):

[0017] (1) Prevention and control of plant fungal diseases;

[0018] (2) Promote plant growth.

[0019] Preferably, the plant fungal disease is corn ear rot and / or corn stalk base rot. The corn stalk base rot is *Fusarium graminearum* stalk base rot. *Fusarium graminearum* stalk base rot is corn stalk base rot caused by *Fusarium graminearum*.

[0020] Preferably, the plant fungal disease is caused by *Fusarium oxysporum* (…). Fusarium verticillioides Fusarium graminearum ( ), Fusarium graminearum ) and / or Pythium styracifolium ( Pythium arrhenomanes Plant fungal diseases caused by fungi.

[0021] Preferably, the plant is corn.

[0022] The sixth objective of this invention is to provide a method for preventing and controlling fungal diseases in maize and promoting maize growth, comprising the following steps: applying the biological agent to maize seeds or maize plants.

[0023] Preferably, the method of application, for corn seeds, is to soak or coat the seeds with the biological agent; for corn plants, it is to drench the roots with the biological agent.

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

[0025] The dispersible pantothecin X24004 of the present invention can effectively inhibit Fusarium graminearum (… Fusarium graminearumIt inhibits mycelial growth, suppresses the occurrence of corn stalk rot, and promotes corn plant growth. At the same time, it has a strong inhibitory effect on the mycelial growth of pathogens such as Fusarium oxysporum and Pythium spp., with a broad spectrum of inhibition. It has antibacterial activity against a variety of plant pathogenic fungi that harm corn crops. It is a broad-spectrum biological agent, biological fertilizer, and seed treatment agent with good development and application prospects, and is of great significance for the biological control of fungal diseases in corn.

[0026] The dispersible pantothecin X24004 strain of the present invention was isolated and purified from the xylem tissue fluid inside corn. The strain itself is safe and non-toxic, safe for humans and animals, has good stability, is easy to preserve, and is environmentally friendly.

[0027] The dispersible pantothecin X24004 biological agent of the present invention has simple culture conditions and is easy to prepare, making it convenient for widespread application.

[0028] Preservation instructions:

[0029] The dispersible pantothecin of the present invention ( Pantoea dispersa X24004 was deposited on May 12, 2025, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 34510, depository code CGMCC-China General Microbiological Culture Collection Center, and address of the depository: No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing. Attached Figure Description

[0030] Figure 1 This is a photograph of the colony morphology of Pantotheca dispersa X24004.

[0031] Figure 2 This is a Gram-stained photograph of a Pantotheca X24004 colony.

[0032] Figure 3 This is a multi-site (16S rRNA, gyrB, rpoB) phylogenetic tree of Pantotheca dispersalis X24004.

[0033] Figure 4 It is the inhibition of dispersible pantothecin X24004 against a variety of plant pathogenic fungi; among them, A is the inhibition against strong male fungi (Pythium spp.). Pythium arrhenomanes The inhibitory effect of B on Fusarium oxysporum (inhibition rate 44.72%) was observed, while B showed an inhibitory effect on Fusarium oxysporum (inhibition rate 44.72%). Fusarium verticillioides The inhibitory effect of ) (inhibition rate 54.04%).

[0034] Figure 5 It is dispersible pantothecin X24004 against Fusarium graminearum ( Fusarium graminearium The inhibition rate was 59.70%.

[0035] Figure 6 The results show the inhibition of Fusarium graminearum conidia germination by Pantotheca X24004; where A represents the conidia germination status of Fusarium graminearum P067 spore suspension without Pantotheca X24004 activation solution, and B represents the conidia germination status of Fusarium graminearum P067 spore suspension inoculated with Pantotheca X24004 activation solution.

[0036] Figure 7 This study evaluates the inhibitory effect of Pantotheca dispersalis X24004 on maize stem base rot and its promoting effect on maize plant growth. A represents maize plant growth; B represents aboveground plant height; C represents aboveground fresh weight of maize plants; D represents the incidence of stem base rot in maize stems and roots; E represents the statistical results of the incidence rates of P067 and X24004+P067 treatments corresponding to D; CK is the blank control; X24004 represents treatment with Pantotheca dispersalis X24004 bacterial suspension; P067 represents treatment with Fusarium graminearum P067 spore suspension; and X24004+P067 represents treatment with both Pantotheca dispersalis X24004 bacterial suspension and Fusarium graminearum P067 spore suspension.

[0037] Figure 8 It is the resistance of Pantothecin X24004 to fludioxonil and fludioxonil seed coating agents.

[0038] Figure 9 This study shows the effect of Pantotheca dispersalis X24004 on maize seed germination; where A is a photograph of maize seed germination and B is the statistical results of root and stem length of germinating seedlings.

[0039] Figure 10 This study investigated the synergistic effects of Panadol X24004 and Fludioxoni on maize seed germination. In the image, A shows photographs of maize seed germination in each treatment; B shows the root and stem lengths of the germinated seedlings in each treatment; CK is the blank control; X24004 represents seed soaking in bacterial solution of strain X24004; Fludioxoni represents seed coating with fludioxoni; and X+F or X24004+Fludioxoni represents simultaneous treatment of seed soaking in bacterial solution of strain X24004 and seed coating with fludioxoni. Detailed Implementation

[0040] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0041] Example 1

[0042] 1. Isolation, purification, identification, and antibacterial activity determination of *Panthera philoxeroides* X24004, an endophytic dispersible bacterium in maize, against *Fusarium graminearum*.

[0043] 1.1 Culture medium preparation

[0044] TSB medium: 17 g tryptone, 1.5 g glucose, 3 g soybean peptone, 2.5 g dipotassium hydrogen phosphate, 5 g sodium chloride, add water to a final volume of 1 L; autoclave at 121°C for 15 min.

[0045] LB medium: 10 g peptone, 5 g sodium chloride, 10 g yeast extract, 15 g agar powder, add water to a final volume of 1 L; autoclave at 121°C for 15 min.

[0046] PDA medium: Difco™ Potato Dextrose Agar 39 g, add water to a final volume of 1 L; autoclave at 121°C for 15 min.

[0047] 1.2 Isolation and purification of endophytic bacteria

[0048] After disinfecting the surface of the second and third internodes from the bottom to the top of the corn plant stem, the stem was cut off (about 30 cm from the ground). The cross-section of the stem was covered with sterile absorbent cotton, and the opening of the sterilization bag was sealed with sealing film. The mixture was left to stand for 24 hours. The absorbent cotton soaked in xylem tissue fluid was collected from the field, placed in a 50 mL centrifuge tube, centrifuged at 6000 g for 5 min, and the filtrate was collected to complete the extraction of xylem tissue fluid.

[0049] Under aseptic conditions, 4 mL of xylem tissue fluid was added to 36 mL of sterile water, and this step was repeated 5 times for serial dilution; at 10 -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 At each dilution gradient, 5 mL of each sample was added to 45 mL of tryptic soybean broth (TSB) medium, mixed thoroughly, and then transferred to a 96-well plate. The plates were incubated at 28°C for 7 days. Each dilution gradient was replicated in three groups. The optimal dilution was selected when the number of turbid wells was close to 1 / 3 of the plate.

[0050] At the optimal dilution, the bacterial cells from the turbid wells were transferred to new 96-well plates and numbered. 10 μL of bacterial suspension was streaked onto LB solid medium and incubated at 28°C for 24 h. Single colonies were picked and cultured overnight at 28°C with shaking at 150 rpm to obtain purified endophytic bacteria, including strain X24004. The bacterial suspension was transferred to cryovials, and 50% glycerol was added in equal proportion. The cryovials were then numbered and stored at -80°C.

[0051] 1.3 Test strains

[0052] Fusarium graminearum ( Fusarium graminearumStrain P067 was isolated from the stem base of maize plants infected with stem rot at the Jiangcheng Experimental Base in Yunnan Province and is preserved in the Maize Diseases Group of the Plant Protection Research Group of the Chinese Academy of Agricultural Sciences.

[0053] 1.4 Determination of the antibacterial activity of endophytic bacteria against Fusarium graminearum

[0054] The purified endophytic bacteria were inoculated into LB liquid medium and cultured overnight at 28°C and 200 rpm to obtain activated bacterial solution.

[0055] The antagonistic effect of screened rhizosphere bacterial strains on target strains was determined using the confrontation culture method. Target strains were inoculated into the center of PDA plates at 5 mm diameter discs, with 10 μL of activated bacterial solution inoculated at 25 mm intervals to the left and right. Three replicates were performed for each rhizosphere bacterial solution. The blank control consisted only of the target strain. Inhibition rate (%) = (control colony diameter - treated colony diameter) / control colony diameter × 100.

[0056] The results showed that the endophytic bacterial strain X24004 significantly inhibited the mycelial growth of Fusarium graminearum P067, producing a distinct inhibition zone with an inhibition rate of 59.70%.

[0057] 1.5 Identification of endophytic bacteria X24004

[0058] 1.5.1 Morphological identification

[0059] The purified endophytic bacteria X24004 were streaked onto LB agar plates and incubated at 28°C for 24 h. The morphology of single colonies was observed. Gram staining of the strain was performed using a Gram staining kit (Beijing Solarbio Science & Technology Co., Ltd.), and the morphology of the strain and the staining results were observed.

[0060] The results showed that the colonies of the endophytic bacteria X24004 were yellow, round, with a smooth, moist, slightly convex surface and neat edges. Figure 1 Gram-negative bacteria, staining red; cell morphology is straight or slightly curved bacilli ( Figure 2 ).

[0061] 1.5.2 Molecular Identification

[0062] Genomic DNA of endophytic bacteria X24004 was extracted from activated bacterial culture using a bacterial genomic DNA extraction kit (Beijing Solarbio Science & Technology Co., Ltd.). PCR amplification was performed using universal primers for the bacterial 16S rRNA gene (27F / 1492R), the gyrB gene (gyrB_F / R), and the rpoB gene (rpoB_F / R). Primer sequences: 27F / 1492R (forward: AGAGTTTGATCCTGGCTCA; reverse: GGTTACCTTGTTACGACTT), gyrB_F / R (forward: GAAGTCATCATGACCGTTCTGCAYGCNGGNGGNAARTTYGA; reverse: AGCAGGGTACGGATGTGCGAGCCRTCNACRTCNGCRTCNGTCAT), rpoB_F / R (forward: GGYTWYGAAGTNCGHGACGTDCA; reverse: TGACGYTGCATGTTBGMRCCCATMA).

[0063] After splicing the amplified sequences using Phylosuite, the following sequences were obtained: 16S rRNA sequence (nucleotide sequence shown in SEQ ID NO.1), gyrB sequence (nucleotide sequence shown in SEQ ID NO.2), and rpoB sequence (nucleotide sequence shown in SEQ ID NO.3). A phylogenetic tree was constructed using MEGA 11, and the endophytic bacterium X24004 and *Ureaplasma dispersum* were located on the same branch. Figure 3 The results showed that strain X24004 was a dispersible pantothenic acid (Pantothenic acid). Pantoea dispersa Therefore, it was named Pantotheca dispersa ( Pantoea dispersa )X24004.

[0064] 2. Determination of the antibacterial activity of dispersible pantothecin X24004 against multiple pathogens

[0065] 2.1 Culture medium preparation

[0066] Same as 1.1.

[0067] 2.2 Test strains

[0068] The pathogen of corn ear rot is *Fusarium verticillatum* (… Fusarium verticillioides ), Fusarium graminearum, the pathogen of corn stem rot. Fusarium graminearum ), Pythium stalk rot pathogen of corn (Pythium spp.) Pythium arrhenomanes (Provided by the Maize Diseases Research Group of the Institute of Plant Protection, Chinese Academy of Agricultural Sciences)

[0069] 2.3 Determination of the antibacterial activity of dispersible pantothecin X24004 against multiple pathogens

[0070] The tested pathogenic strains were inoculated into PDA medium for activation and plate antagonism test, and the determination method was the same as in 1.4.

[0071] The results showed that *Pantotheca dispersalis* X24004 had broad-spectrum antibacterial activity (Table 1). Figure 4 , Figure 5 ).

[0072] Table 1. Inhibitory effects of Pantothecin X24004 on various pathogens.

[0073]

[0074] 3. Effect of Pantotheca dispersalis X24004 on the germination of Fusarium graminearum conidia.

[0075] 3.1 Culture medium preparation

[0076] Mung bean soup culture medium: Boil 10 g of mung beans in boiling water for 20 min, filter to obtain the liquid, add water to make up to 1 L, and autoclave at 121℃ for 15 min.

[0077] 3.2 Test strains

[0078] Same as 1.3.

[0079] 3.3 Observation of the effect of dispersed pantothenic acid X24004 on the germination of Fusarium graminearum conidia using hydrophobic glass slides

[0080] Dispersed Pantothenia X24004 was inoculated into LB liquid medium and incubated at 28°C and 200 rpm for 24 h, adjusting OD... 600 =1, activated bacterial solution for later use; the tested strain Fusarium graminearum P067 was inoculated into mung bean soup medium for sporulation and cultured at 25℃ and 150 rpm for 7 days for later use. The spore suspension of the shaken-cultured Fusarium graminearum P067 was centrifuged at 8000 rpm for 10 min at room temperature, washed three times with sterile water, and two treatment groups, A and B, were set up: A - blank control, B - inoculated with activated Pantothenia glutinosa X24004 bacterial solution. 20 μL of spore suspension from each group was added to a hydrophobic glass slide, with 5 replicates per treatment. The culture was carried out at 25℃ for 3 h under constant temperature and humidity, and the spore germination of the tested strain Fusarium graminearum P067 was observed.

[0081] The results showed that after 3 h of constant temperature and humidity incubation at 25℃, the conidia of *Fusarium graminearum* P067 tested in group A germinated normally, and the mycelial growth was vigorous; the germination of conidia of *Fusarium graminearum* P067 tested in group B was significantly inhibited. Figure 6 ).

[0082] 4. Determination of the growth-promoting ability of Pantotheca dispersalis X24004 on maize plants

[0083] 4.1 Culture medium preparation

[0084] Same as 1.1.

[0085] 4.2 Pot experiment to verify the growth-promoting effect of Pantothecin X24004 on maize plants.

[0086] Mix nutrient soil and vermiculite at a volume ratio of 3:1, and sterilize by dry heat at 121℃ for 3 hours. Plant 3 corn seeds in each pot, with 15 pots forming one treatment group. Two treatment groups were established: A - blank control, and B - inoculated with dispersible pantothenic acid X24004 bacterial suspension. Dispersible pantothenic acid X24004 was inoculated into LB liquid medium, incubated overnight at 28℃ and 160 rpm with shaking, centrifuged at 8000 rpm for 10 minutes at room temperature, washed three times with sterile water, and the OD was adjusted. 600 =1, reserved; at sowing, inoculate the group B corn with the bacterial suspension, and drench the roots of each corn plant with 10 mL of dispersed Pantotheca X24004 bacterial suspension; for group A corn, drench the roots of each corn plant with 10 mL of sterile water. Maintain soil moisture throughout the growing process, using tap water for irrigation. Observe plant growth 20 days after inoculation.

[0087] The results showed that, compared with the blank control group A, the aboveground fresh weight of maize plants in group B increased by 12.77%, and the aboveground plant height increased by 3.76%. Figure 7 AC in the middle.

[0088] 5. Efficacy determination of dispersible pantothecin X24004 against maize Fusarium stalk rot

[0089] 5.1 Culture medium preparation

[0090] Same as 1.1 and 3.1.

[0091] 5.2 Test strains

[0092] Same as 1.3.

[0093] 5.3 Pot experiment to verify the control efficacy of Pantothecin X24004 against Fusarium wilt of maize stem base.

[0094] Mix nutrient soil and vermiculite at a volume ratio of 3:1, and sterilize by dry heat at 121℃ for 3 hours. Plant 3 corn seeds in each pot, with 15 pots forming one treatment group. There are three treatment groups: A (blank control), B (inoculated with a suspension of *Fusarium graminearum* P067 spores), and C (inoculated with *Panthera philoxeroides* X24004 bacterial suspension and a suspension of *Fusarium graminearum* P067 spores). *Panthera philoxeroides* X24004 was inoculated in LB broth and incubated overnight at 28℃ and 160 rpm. *Fusarium graminearum* P067 was inoculated in mung bean soup sporulation medium and incubated at 25℃ and 150 rpm for 7 days. At sowing time, centrifuge the *Panthera philoxeroides* X24004 bacterial suspension at 8000 rpm for 10 minutes at room temperature, wash three times with sterile water, and adjust the OD value. 600 =1, inoculate group C corn by drenching the roots of each corn plant with 10 mL of dispersed Panax notoginseng X24004 suspension. Simultaneously, drench the roots with Fusarium graminearum P067 spore suspension, adjusting the spore suspension concentration to 3 × 10⁻⁶. 5 The spores were inoculated at a rate of 10 mL / mL into corn plants in groups B and C. The roots of each corn plant were drenched with 10 mL of spore suspension. Moisture was maintained throughout the growing process. Plant growth and disease incidence were observed 20 days after inoculation.

[0095] The results showed that, observing the growth of the three groups of maize plants, the outer stems of group B maize plants infected with the tested strain Fusarium graminearum P067 withered and the roots showed signs of rot. The outer stems of groups A and C plants showed a healthy purplish-red color. Figure 7 (D) Compared with the blank control group A, the aboveground fresh weight of maize plants in group B decreased by 46.20%, and the aboveground plant height decreased by 29.42%; compared with group B, the aboveground fresh weight of maize plants in group C increased by 26.09%, the aboveground plant height increased by 13.14%, and the incidence of stem rot decreased by 24.57% (D). Figure 7 (E in the text).

[0096] 6. Determination of resistance of Pantothecin X24004 to fludioxonil

[0097] 6.1 Culture medium preparation

[0098] Preparation of LB-fludioxonil-containing culture medium:

[0099] LB medium: 10 g peptone, 5 g sodium chloride, 10 g yeast extract, 15 g agar powder, add water to a final volume of 1 L; autoclave at 121°C for 15 min.

[0100] Dissolve 0.1 g of fludioxonil technical grade in 10 mL of dimethyl sulfoxide (DMSO) to obtain a fludioxonil concentration of 10. 4ppm, take 1 mL of this concentration solution and add it to 9 mL of 0.02% Tween 80, then further dilute to obtain a fludioxonil concentration of 10. 3 Prepare ppm drug-containing solutions for later use. Add 400 μL, 300 μL, 200 μL, 100 μL, and 20 μL of fludioxonil solution to 20 mL of LB medium, respectively, and then pour the plates to obtain LB-fludioxonil drug-containing media with final concentrations of 20 ppm, 15 ppm, 10 ppm, 5 ppm, and 1 ppm, respectively.

[0101] In addition, 10 μL of fludioxonil suspension seed coating agent (trade name: Shileshi, active ingredient 25g / L) was added to 20 mL of LB medium to make the final concentration of fludioxonil seed coating agent 12.5 ppm, thus obtaining a medium containing fludioxonil seed coating agent.

[0102] 6.2 Determination of resistance of Pantotheca dispersalis X24004 to fludioxonil

[0103] Dispersed Pantothenia X24004 was inoculated into LB liquid medium and incubated overnight at 28°C and 160 rpm with shaking. 10 μL of activated bacterial solution was streaked onto drug-treated medium in four zones, with five replicates for each concentration gradient. A control group was set up by streaking 10 μL of bacterial solution onto drug-free LB medium and incubating overnight at 28°C. Colony growth was observed.

[0104] The results showed that, compared with the control group, *Panthera philoxeroides* X24004 could grow normally on various concentrations of drug-containing media and media containing fludioxonil seed coating agent, without exhibiting a fludioxonil-inhibited growth phenotype; indicating that *Panthera philoxeroides* X24004 can coexist with fludioxonil and possesses fludioxonil resistance. Figure 8 ).

[0105] 7. Determination of the effect of Pantotheca dispersalis X24004 on maize seed germination

[0106] 7.1 Culture medium preparation

[0107] Same as 1.1.

[0108] 7.2 Germination paper test to observe the effect of Pantotheca dispersalis X24004 on maize seed germination

[0109] Soak germination paper in sterile water for 3 hours and set aside. Inoculate dispersible pantothenic acid X24004 into LB liquid medium and incubate overnight at 28°C and 160 rpm with shaking. Wash off the medium and adjust OD using sterile water. 600=1, prepare the dispersed pantothecin X24004 bacterial solution for later use. Take corn variety B73 seeds, disinfect the surface with 75% alcohol, rinse thoroughly with sterile water, and set aside. The treatment group soaked the corn seeds in the dispersed pantothecin X24004 bacterial solution for 2 hours, while the control group soaked the corn seeds in sterile water for 2 hours. Place 10 corn seeds neatly in a germination paper at 2 / 3 of its width, cover with another sheet of germination paper, roll up from one side, and place in a self-sealing bag for moisture retention. Observe the germination and seedling emergence of the corn seeds after 8 days.

[0110] The results showed that, compared with the blank control group, maize seeds germinated normally under the treatment of Pantotheca dispersalis X24004 bacterial solution, without any inhibited phenotype, demonstrating biological safety. Simultaneously, maize root length increased by 31.43% and stem length increased by 36.61%, exhibiting a significant growth-promoting effect. Figure 9 ).

[0111] 8. Effects of synergistic treatment with Pantothecin X24004 and Fludioxonil on maize seed germination.

[0112] 8.1 Culture medium preparation

[0113] Same as 1.1.

[0114] 8.2 Germination paper test to observe the effect of synergistic treatment of dispersible pantothecin X24004 and fludioxonil on maize seed germination

[0115] Soak germination paper in sterile water for 3 hours and set aside. Inoculate dispersible pantothenic acid X24004 into LB liquid medium and incubate overnight at 28°C and 160 rpm with shaking. Wash off the medium and adjust OD using sterile water. 600 =1, prepare strain X24004 bacterial solution for later use. Take corn variety B73 seeds and set up four treatment groups: (1) blank control, (2) soaking in strain X24004 bacterial solution, (3) coating with fludioxonil seed coating agent, (4) soaking in strain X24004 bacterial solution + coating with fludioxonil seed coating agent. The strain X24004 bacterial solution soaking treatment is: soak corn seeds in X24004 bacterial solution for 2 h. The control group is soaked in sterile water for 2 h. The fludioxonil seed coating agent treatment is: 50 μL of fludioxonil suspension seed coating agent (trade name: Shileshi, active ingredient 25 g / L) is dissolved in 2 mL of sterile water, added to 50 g of corn seeds, shaken evenly, and dried in a fume hood. Place 10 corn seeds neatly at 2 / 3 of the width of the germination paper, cover with another sheet of germination paper, roll it up from one side, and place it in a resealable bag to keep it moist. Observe the germination and seedling status of the corn seeds after 8 days.

[0116] The results showed that, compared with the blank control group, all three treatment groups exhibited growth-promoting phenotypes. The root length of maize seeds increased by 52.75%, 82.24%, and 72.64% respectively under the treatment of seed soaking in strain X24004, seed coating with fludioxonil, and simultaneous treatment of seed soaking in strain X24004 and seed coating with fludioxonil; the stem length increased by 25.84%, 58.61%, and 65.79% respectively. Figure 10 ).

[0117] In summary, strain X24004 is an endophytic dispersible pantothecin fungus of maize, a Gram-negative bacterium, exhibiting broad and highly effective antifungal activity against a variety of plant pathogenic fungi. The suspension of strain X24004 significantly inhibits the mycelial growth and spore germination of *Fusarium graminearum*, demonstrating high antagonistic activity. Pot experiments showed that the suspension of strain X240048 can control maize *Fusarium graminearum* stem rot; strain X24004, applied through root irrigation, promotes maize plant growth; strain X24004, used as a seed treatment agent through seed soaking, promotes maize plant growth; strain X24004 can coexist with existing chemical seed dressing agents, synergistically promoting maize seed germination and plant growth. Applying strain X24004 for biological control of soil-borne diseases like stem rot can reduce or avoid the environmental pollution caused by chemical control, making it more environmentally friendly and efficient.

Claims

1. A strain of dispersible pantothenic acid ( Pantoea dispersa X24004, characterized in that, CGMCC No. 34510.

2. A biological agent, characterized in that, A culture of the Pantoea dispersa X24004 according to claim 1 or the Pantoea dispersa X24004 according to claim 1 as an active ingredient.

3. A bio-bacterial fertilizer, characterized in that, A fertilizer containing the Pantoea dispersa X24004 according to claim 1.

4. A seed treatment agent characterized in that, A seed coating agent containing the Pantoea dispersa X24004 according to claim 1, fludioxonil and a seed coating agent adjuvant.

5. Use of the Pantoea dispersa X24004 according to claim 1 or the biological agent according to claim 2 in at least one of the following (1)-(2): (1) preventing and treating plant fungal diseases; the plant fungal diseases are plant fungal diseases caused by Pseudocercospora paspali (Zimm.) Jenkins et al. Fusarium verticillioides , F. graminearum (Schweinitz) Sace, and / or P. thomsporum (Shear) Lehm. Fusarium graminearum Pythium arrhenomanes , F. graminearum (Schweinitz) Sace, and / or P. thomsporum (Shear) Lehm.​ (2) promoting the growth of corn.

6. A method of controlling fungal diseases of corn and promoting the growth of corn, characterized by, The method comprises the following steps: applying to corn seeds or corn plants the biological agent of claim 2; the corn fungal disease being a corn fungal disease caused by Fusarium verticillioides F. pseudograminearum, Fusarium graminearum F. graminearum, and / or Pythium arrhenomanes P. irregular.

7. The method of claim 6, wherein, The mode of application to corn seeds is seed soaking or coating with the biological agent; the mode of application to corn plants is root irrigation with the biological agent.

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