Rahnella RS86 and its application in controlling corn root rot

Abstract

The invention relates to the technical field of biocontrol bacteria, in particular to Rahnella RS86 and its application in preventing and controlling corn root rot. The deposit number of the Rahnella RS86 of the invention is CCTCC NO: M 20242043. The Rahnella RS86 provided by the invention is a biocontrol bacterium isolated from a farmland with serious corn root rot in Tongyu County, Baicheng City, Jilin Province, which can effectively inhibit the growth of Fusarium graminearum (Fg) and Fusarium pseudoverticillium (Fv), and has a good control effect on corn root rot. The control effect of Fusarium graminearum reaches 38.27%, and the control effect of Fusarium pseudoverticillium reaches 35.09%; accompanied by a good growth-promoting effect, the aboveground biomass of corn can be increased by 31.53% and 24.10% respectively compared with the plants treated with Fg and Fv; it has beneficial functions such as producing IAA, solubilizing phosphorus, fixing nitrogen, and producing iron carriers, and provides a new biocontrol bacterium for the prevention and control of corn root rot.

Description

Technical Field

[0001] The invention relates to the technical field of biocontrol bacteria, in particular to Rahnella RS86 and application thereof in preventing and controlling corn root rot. Background Art

[0002] Corn root rot is caused by a variety of pathogenic fungi (such as Fusarium verticillioides , Fusarium graminearum Common corn diseases caused by fungi (such as spores, mites, etc.), in which pathogenic fungi infect the root system and cause rot, seriously affecting the function of the root system and thus affecting the growth and development of the plant. This disease can cause problems such as stunted plants, yellowing leaves, small ears and few seeds. In severe cases, it can lead to a significant drop in yield or even a total crop failure.

[0003] Traditional prevention and control methods, such as soil fumigation and the application of chemical fungicides, have controlled the disease to a certain extent, but have also caused damage to the soil ecosystem and posed potential risks to environmental safety and human health. In addition, the use of chemical pesticides may cause drug resistance in pathogens and also inhibit the growth of key beneficial microorganisms in the soil.

[0004] As a green and environmentally friendly means of prevention and control, biological control can not only improve soil health but also enhance the disease resistance of plants by utilizing the competitive effects of beneficial microorganisms and the biological control mechanism of pathogens. However, there is currently a lack of biological control bacteria with good control effects on corn root rot. Summary of the invention

[0005] In order to solve the above problems, the present invention provides Raenella RS86 and its application in preventing and controlling corn root rot. The Raenella RS86 provided by the present invention can effectively inhibit Fusarium graminearum ( Fusarium graminearum ) and Pseudomonas verticillasters ( Fusarium verticillioides ) has a good preventive and therapeutic effect on corn root rot, providing a new biocontrol bacterium for the prevention and control of corn root rot.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a strain of Rahn's bacterium ( Rahnella sp.) RS86, the deposit number of the Rahn's sp. RS86 is CCTCC NO: M 20242043.

[0008] The present invention provides a microbial agent, which includes the Rahn's bacterium RS86 described in the above technical solution.

[0009] Preferably, the number of viable bacteria of Rahn's bacterium RS86 in the microbial agent is ≥ 1×10 8 CFU / mL.

[0010] The present invention provides a method for preparing the microbial agent described in the above technical solution, comprising the following steps:

[0011] The Rahn's bacterium RS86 described in the above technical scheme is cultured in a fermentation medium to obtain the microbial agent; the fermentation medium comprises: 1.5 g of citric acid, 10.0 g of glucose, 0.1 g of ferric citrate ammonium, 2.0 g of ammonium nitrate, 0.2 g of magnesium sulfate and 1 L of water.

[0012] Preferably, the culture temperature is 28-30° C. and the culture time is 5-7 d.

[0013] The present invention provides the use of Rahnella RS86 described in the above technical scheme or the microbial agent described in the above technical scheme or the microbial agent prepared by the preparation method described in the above technical scheme in preventing and controlling plant fungal diseases and / or promoting plant growth, wherein the fungi include Fusarium graminearum and / or Fusarium pseudoverticillium.

[0014] Preferably, the plant comprises corn.

[0015] Preferably, the plant fungal disease is corn root rot.

[0016] The present invention provides a method for preventing and controlling plant fungal diseases and / or promoting plant growth, comprising: applying a microbial agent into soil planted with plants; the microbial agent is the microbial agent described in the above technical scheme or a microbial agent prepared by the preparation method described in the above technical scheme; the fungi include Fusarium graminearum and / or Fusarium pseudoverticillium.

[0017] Preferably, the amount of the microbial agent applied is ≥1×10 7 CFU / g soil.

[0018] Beneficial effects:

[0019] The present invention provides a strain of Raenella RS86, and the deposit number of the Raenella RS86 is CCTCC NO: M20242043. The Raenella RS86 provided by the present invention is a biocontrol bacterium isolated from a farmland with serious corn root rot in Tongyu County, Baicheng City, Jilin Province, and can effectively inhibit the growth of Fusarium graminearum (Fg) and Fusarium pseudoverticillium (Fv), and has a good control effect on corn root rot, with the control effect of Fusarium graminearum reaching 38.27% and the control effect of Fusarium pseudoverticillium reaching 35.09%; accompanied by a good growth-promoting effect, the aboveground biomass of corn can be increased by 31.53% and 24.10% respectively compared with the plants treated with Fg and Fv; it has beneficial biological functions such as producing IAA, solubilizing phosphate, fixing nitrogen, producing iron carriers, etc., and provides a new biocontrol bacterium for the control of corn root rot.

[0020] Biological Deposit Description

[0021] Rahnella RS86, taxonomically named Rahnella sp., deposited in China Center for Type Culture Collection (CCTCC) on September 23, 2024, with the deposit address at No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province, China Center for Type Culture Collection, Wuhan University, and the deposit number is CCTCC NO: M 20242043. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0023] Figure 1 This is a picture showing the culture results of Rahn's bacterium RS86 on LB plate;

[0024] Figure 2 is the phylogenetic tree of Rahnella RS86;

[0025] Figure 3 This is a graph showing the results of the inhibition test of Rahnella RS86 on Fusarium graminearum;

[0026] Figure 4 This is a graph showing the results of the inhibition test of Rahnella RS86 on Fusarium verticillium;

[0027] Figure 5 The results of the test of using a microbial agent of Rahnella RS86 to control corn root rot caused by the pathogen Fusarium graminearum;

[0028] Figure 6 The results of the test on the microbial agent of Rahnella RS86 for controlling the pathogen of corn root rot caused by Fusarium spp. DETAILED DESCRIPTION

[0029] The present invention provides a strain of Rahn's bacterium ( Rahnella sp.) RS86, the deposit number of the Rahn's sp. RS86 is CCTCC NO: M 20242043.

[0030] The Rahnella RS86 provided by the present invention is a biocontrol bacterium isolated from a farmland with serious corn root rot in Tongyu County, Baicheng City, Jilin Province. The colony appears light yellow on the LB plate, with neat edges, regular circles and a smooth surface (see Figure 1), can effectively inhibit the growth of Fusarium graminearum and / or Fusarium pseudo-verticillium, with inhibition rates of 21.92% and 20.46% respectively, and has a good control effect on corn root rot, with the control effect of Fusarium graminearum reaching 38.27% and the control effect of Fusarium pseudo-verticillium reaching 35.09%; accompanied by a good growth-promoting effect, the aboveground biomass of corn can be increased by 31.53% and 24.10% compared with the plants treated with Fg and Fv, respectively; it has beneficial functions such as producing IAA, solubilizing phosphate, fixing nitrogen, and producing iron carriers, providing a new biocontrol bacterium for the control of corn root rot.

[0031] The present invention provides a microbial agent, which includes the Rahn's bacterium RS86 described in the above technical solution.

[0032] As an embodiment, the number of viable bacteria of Rahn's bacterium RS86 in the microbial agent is ≥ 1×10 8 CFU / mL.

[0033] The present invention provides a method for preparing the microbial agent described in the above technical solution, comprising the following steps:

[0034] The Rahn's bacterium RS86 described in the above technical scheme is cultured in a fermentation medium to obtain the microbial agent; the fermentation medium comprises: 1.5 g of citric acid, 10.0 g of glucose, 0.1 g of ferric citrate ammonium, 2.0 g of ammonium nitrate, 0.2 g of magnesium sulfate and 1 L of water.

[0035] As one embodiment, the culture temperature is 28-30°C, and the culture time is 5-7 days. As another embodiment, the culture temperature is 30°C, and the culture time is 6 days.

[0036] The microbial agent provided by the invention has the advantages of simple preparation method, low cost, short fermentation cycle and easy storage.

[0037] Based on the above advantages, the present invention provides the use of the Rahnella RS86 described in the above technical solution or the microbial agent described in the above technical solution or the microbial agent prepared by the preparation method described in the above technical solution in preventing and controlling plant fungal diseases and / or promoting plant growth, wherein the fungi include Fusarium graminearum ( Fusarium graminearum ) and / or Pseudomonas verticillasters ( Fusarium verticillioides ).

[0038] As an embodiment, the plant may be corn.

[0039] As an embodiment, the plant fungal disease is corn root rot.

[0040] Based on the above advantages, the present invention provides a method for preventing and controlling plant fungal diseases and / or promoting plant growth, comprising: applying a microbial agent to soil planted with plants; the microbial agent is the microbial agent described in the above technical solution or the microbial agent prepared by the preparation method described in the above technical solution; the fungi include Fusarium graminearum ( Fusarium graminearum ) and / or Pseudomonas verticillasters ( Fusarium verticillioides ).

[0041] As an embodiment, the amount of the microbial agent applied is ≥1×10 7 CFU / g soil.

[0042] As an embodiment, the plant may be corn.

[0043] As an embodiment, the plant fungal disease is corn root rot.

[0044] To further illustrate the present invention, the Rahn's bacterium RS86 provided by the present invention and its application in preventing and controlling corn root rot are described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0045] The pathogenic fungus Fusarium graminearum ( Fusarium graminearum ) and Pseudomonas verticillasters ( Fusarium verticillioides ) are all commercially available strains. Among them, Fusarium graminearum was purchased from Mingzhoubio, product number BMZ097952; Fusarium pseudoverticillium was purchased from Mingzhoubio, product number BMZ075254.

[0046] Example 1

[0047] From the soil samples of farmland with serious corn root rot in Tongyu County, Baicheng City, Jilin Province, 10 g of the mixed soil samples were added to a 250 mL Erlenmeyer flask containing 100 mL of sterile water, placed on a shaker at 180 rpm for 30 minutes, and allowed to stand for 2 hours. 1 mL of the supernatant was placed in 9 mL of sterile water for dilution to 10 -3 , 10 -4 , 10 -5 , 0.1 mL of each concentration gradient was spread on LB medium plates and cultured at 30°C for 2-4 days. After the colonies grew, they were separated and purified, and antagonistic bacteria were screened against the pathogens Fusarium graminearum and Fusarium pseudoverticillium. A strain with significant inhibitory effects on both target pathogens was selected and named RS86.

[0048] Morphological characteristics of strain RS86: The colonies on the LB plate appear orange, with neat edges, regular circles and smooth surfaces (see Figure 1 ).

[0049] 16S rRNA gene sequence determination: Using the genomic DNA of strain RS86 as a template, universal primers 27F and 1492R were used to amplify the 16S rRNA gene sequence. The primer sequences are as follows:

[0050] 27F: 5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO.1;

[0051] 1492R: 5'-GGTTACCTTGTTACGACTT-3', SEQ ID NO. 2.

[0052] PCR reaction system (50 μL): Primer 27F 1.5 μL, Primer 1492R 1.5 μL, Template DNA 1 μL, 2×Repid Taq Master Mix 25 μL, Sterile water 21 μL. PCR reaction conditions: 95℃ pre-denaturation for 5 min; 94℃ denaturation for 30 s, 53℃ annealing for 30 s, 72℃ extension for 30 s, 30 cycles; finally 72℃ extension for 10 min. The amplified product was detected by agarose gel electrophoresis and sequenced by Beijing Qingke Biotechnology Co., Ltd. The sequencing results are shown in SEQ ID No. 3, as follows:

[0053]

[0054] The 16S rRNA gene sequence of strain RS86 obtained by sequencing was submitted to Genbank for sequence alignment and phylogenetic tree was constructed ( Figure 2 ), strain RS86 was found to be clustered with the genus Rahnella and with the type strain Rahnella aquatilis The sequence homology of CIP 78.65 was the highest, reaching 99.79%. Based on this, strain RS86 was classified as Rahnella ( Rahnella The strain RS86 was deposited in China Center for Type Culture Collection with the deposit number CCTCCNO: M 20242043.

[0055] Example 2 Inhibitory effect of Rahnella RS86 on the main pathogens of corn root rot

[0056] The plate confrontation culture method was used to test the inhibitory effect of Rahn's bacterium RS86 screened in Example 1 on the pathogenic fungi Fusarium graminearum and Fusarium pseudoverticella. Rahn's bacterium RS86 was inoculated into LB medium for activation; the two pathogenic fungi were inoculated into PDA medium for activation, and 60 μL of bacterial solution was evenly inoculated on the sterile filter paper on one side of the PDA medium, and cultured at 28°C for 2 days; a puncher with a diameter of 5 mm was used to punch out bacterial blocks of the same age at the edge of the pathogenic fungal colony, and the hyphae were placed downward at a distance of 2 cm from the filter paper. After constant temperature culture at 25°C for 5 days, the growth of the hyphae was evaluated and compared with the control group in which the bacterial solution was replaced with sterile water.

[0057] Results Figure 3 and Figure 4 The results showed that Rahn's bacterium RS86 had a good antagonistic effect on the pathogenic fungi Fusarium graminearum and Fusarium pseudoverticillium, reaching 21.92% and 20.46% respectively. This showed that Rahn's bacterium RS86 in the present invention had a good inhibitory effect on both corn root rot pathogenic fungi.

[0058] Example 3 Determination of the probiotic properties of Rahnella RS86

[0059] (1) Determination of nitrogen fixation ability of strains

[0060] Under sterile conditions, Rahn's bacterium RS86 was inoculated into a low nitrogen medium using an inoculation loop, incubated at 28°C for 7 days, and transferred three times to observe whether it grew and record the growth status; the formula of the low nitrogen medium is as follows:

[0061] 0.03 g calcium nitrate, 0.15 g disodium hydrogen phosphate, 0.1 g calcium chloride, 0.12 g magnesium sulfate, 0.1 g potassium dihydrogen phosphate, 0.05 g ferric citrate, 1.0 mL trace elements, 1000 mL distilled water; the trace element formula is: 2.86 g boric acid, 1.81 g manganese sulfate, 0.8 g copper sulfate, 0.02 g molybdic acid, and the volume is made up to 1000 mL with distilled water.

[0062] (2) ACC deaminase activity assay

[0063] Rahn's bacterium RS86 was inoculated into fresh YN medium for activation. After overnight culture for about 16 h, it was inoculated into 50 mL DF medium at a 5% (v / v) inoculation rate. After shaking culture for 24 h, the strain in DF medium was inoculated onto ADF solid medium and cultured in an incubator at 28°C for 7 days to observe the growth of the colonies.

[0064] YN medium: sucrose 10.0 g, ammonium sulfate 1.0 g, potassium hydrogen phosphate 1.0 g, magnesium sulfate heptahydrate 0.5 g, yeast extract 0.5 g, sodium chloride 0.1 g, calcium carbonate 0.5 g, distilled water 1 L, pH 7.2.

[0065] DF medium: 4 g potassium dihydrogen phosphate, 6 g disodium hydrogen phosphate, 0.2 g magnesium sulfate, 2 g glucose, 2 ml gluconic acid, 2 g citric acid, 2 g ammonium sulfate, 1 L distilled water, pH 7.2.

[0066] ADF medium: Add the filtered and sterilized 1-aminocyclopropanecarboxylic acid (ACC) to the DF solid medium without ammonium sulfate to a final concentration of 3 mmol / L, which is the ADF medium.

[0067] (3) Acidity

[0068] Rahn's bacterium RS86 was inoculated into a conical flask containing YN liquid medium at a 1% (v / v) inoculation volume, and three replicates were set. The flask was placed on a shaker at 30°C and cultured at 150 rpm for 72 h. Centrifuged at 8000 rpm for 10 min, and the pH value of the supernatant was measured using a pH meter.

[0069] (4) Experiment on the determination of the production of elongin by strains

[0070] Activate and prepare bacterial suspension of Rahn's bacterium RS86 in YN liquid medium (OD 600=1), inoculated into YN medium with a tryptophan concentration of 0.5 mg / mL at a 1% (v / v) inoculum, cultured in a shaker at 30°C and 200 rpm for 3 d, centrifuged at 6000 rpm for 10 min, took 500 μL of supernatant, added 25 μL of 10 mM orthophosphoric acid, and then added 1 mL of Sackowki's color developer and mixed thoroughly, reacted in the dark for 30 min, and measured the absorbance at 530 nm; the Sackowki's color developer was prepared as follows: 150 mL of concentrated sulfuric acid was slowly added to 250 mL of deionized water along the wall of the cup, and after cooling, 7.5 mL of 0.5 mol / L FeCl3 solution was added.

[0071] (5) Experiment on determination of iron carrier production by strains

[0072] Take OD 600 =1 Rahn's RS86 bacterial suspension was inoculated into MKB liquid culture medium (TOPBIO, MD193) at a 1% (v / v) inoculation rate. After culturing in a shaker at 30°C and 200 rpm for 48 h, the mixture was centrifuged at 10,000 rpm for 10 min. 1 mL of the supernatant was mixed with 1 mL of CAS detection solution and diluted to 15 mL. After 1 h of reaction, the absorbance (As) was measured at 630 nm. The uninoculated MKB culture medium was used as the reference value (Ar). Siderophore activity units (SAU) = [(Ar−As) / Ar] × 100.

[0073] (6) Experiment on the determination of the amount of phosphorus solubilized by the strain

[0074] Take OD 600 =1 Rahnella RS86 bacterial suspension was inoculated into NBRIP inorganic phosphorus (REBIO, T3037) and Montana organic phosphorus liquid medium (Coolaber, MM5060+Y) at a 1% (v / v) inoculum amount, cultured at 30°C, 200 rpm for 7 days, centrifuged at 3000 rpm for 10 min, 1 mL of supernatant was mixed with 2 mL of molybdenum antimony anti-color developer and shaken, and placed in a 40°C water bath for 20 min. After cooling, the absorbance of the solution was measured at 820 nm, and the phosphorus content of the sample was calculated from the standard curve; the molybdenum antimony anti-color developer was prepared as follows: a solution containing 0.4% ammonium molybdate and 0.5 mol / L H2SO4 was mixed with a 10% ascorbic acid solution in a volume ratio of 6:1, stored at 4°C in the dark, and prepared on the same day.

[0075] (7) Measurement results

[0076] A series of preliminary qualitative determinations were made on properties such as acid production, IAA production, siderophore production, nitrogen fixation, phosphate solubilization, and ACC deaminase, and the final results are shown in Tables 1 and 2.

[0077] Table 1 Results of the determination of the probiotic properties of Rahnella RS86

[0078]

[0079] Note: "+" indicates that the strain has this property, and "-" indicates that the strain does not have this property. Acidogenicity means that the pH of the strain is below 5.0; IAA production means that the IAA content is above 5 mg / L.

[0080] Table 2 Quantitative determination results of the probiotic properties of Rahnella RS86

[0081]

[0082] The results show that RS86 is acidic, with a pH of about 4.74, indicating that RS86 has a good ability to decompose organic and inorganic phosphorus. At the same time, RS86 has a good ability to produce IAA, reaching 39.61 mg / L. RS86 also has the ability to produce siderophores, which indicates that RS86 has growth-promoting potential.

[0083] Example 4 Preparation of Microbial Agent of Rahnella RS86

[0084] The production process of the microbial agent of Rahn's bacterium RS86 is as follows: plate inoculation - shake flask seed solution - fermentation agent production. The culture medium used in the present invention is:

[0085] LB medium: peptone 10.0 g, yeast powder 5.0 g, sodium chloride 5.0 g, deionized water 1 L. Add 1.5% agar powder to the solid medium.

[0086] Fermentation medium: 1.5 g citric acid, 10.0 g glucose, 0.1 g ferric citrate ammonium, 2.0 g ammonium nitrate, 0.2 g magnesium sulfate, 1 L deionized water.

[0087] The present invention implements the steps in detail:

[0088] (1) Streak the strain RS86 on an LB plate and culture it at 30°C for 2 days.

[0089] (3) Pick a single colony of the cultured strain and place it in liquid LB medium. Cultivate it in a shaking flask at 30°C and 180 rpm until the logarithmic growth phase. This is used as the seed liquid.

[0090] (3) The seed liquid was inoculated into a 25 L fermenter at a 5% (v / v) inoculation rate to expand the culture. After reaching the logarithmic growth phase, the seed liquid was inoculated into a 500 L fermenter at a 5% (v / v) inoculation rate to continue the fermentation culture. The culture medium was used as the fermentation medium. The fermentation culture temperature was 30°C, the volume ratio of sterile air to fermentation medium was 1:0.8~1.2, the stirring speed was controlled at 180~200 rpm, and the total production time of the inoculant was 5~7 days. After the fermentation, the concentration was 10 8 CFU / mL, and the fermented bacterial liquid was packaged in plastic buckets to make liquid bacterial agent.

[0091] Example 5 Experiment on the Control of Corn Root Rot by Microbial Agent of Rahnella RS86

[0092] The susceptible corn seeds, Jidan 37, were selected and germinated at 25°C after sterilization. Seedlings with consistent growth were selected and divided into 5 groups, namely blank control group (denoted as CK), control group 1 (denoted as Fg), control group 2 (denoted as Fv), treatment group 1 (denoted as Fg+RS86) and treatment group 2 (denoted as Fv+RS86). The specific treatments are as follows:

[0093] CK group: no pathogen Fusarium graminearum inoculation, no liquid bacterial agent prepared in Example 4 was applied;

[0094] Fg group: inoculated with Fusarium graminearum (denoted as Fg), the inoculation amount was 10 7 spores / g soil, without applying the liquid bacterial agent prepared in Example 4;

[0095] Fg+RS86 group: inoculated with Fusarium graminearum (denoted as Fg), with an inoculation amount of 10 7 spores / g soil, the liquid bacterial agent prepared in Example 4 was applied at an application rate of 10 7 CFU / g soil.

[0096] Fv group: inoculated with Fusarium spp. (denoted as Fv), with an inoculation volume of 10 7 spores / g soil, without applying the liquid bacterial agent prepared in Example 4;

[0097] Fv+RS86 group: inoculated with Fusarium verticillium (denoted as Fv), with an inoculation amount of 10 7 spores / g soil, the liquid bacterial agent prepared in Example 4 was applied at an application rate of 10 7 CFU / g soil.

[0098] After culturing for 3 weeks under the conditions of 16 h daytime / 25°C and 8 h nighttime / 22°C, the 5 groups of seedlings were photographed, and the root fresh weight, aboveground fresh weight, disease index, relative protection effect and hydrogen peroxide content of the plants were measured to evaluate the disease inhibition effect. The calculation method of disease index and relative protection effect is as follows:

[0099] Disease index = (root length of diseased root / total root length) × 100%.

[0100] Relative prevention effect = [(disease index of control group - disease index of treatment group) / disease index of control group] × 100%, where the control group and treatment group are the results of treatment with the same pathogen.

[0101] The hydrogen peroxide content in the aboveground part of corn was determined by the method of Velikova et al. [Velikova V, Yordanov I, Edreva A. Oxidative stress and some antioxidant systems in acid rain-treated bean plants: protective role of exogenous polyamines. Plant Science, 2000, 151(1): 59-66.]. The results are shown in Figure 5 and Figure 6 , where different letters represent significant differences among different groups.

[0102] The results showed that compared with the control group where only Fg pathogens were applied (disease index was 81%), the bacterial agent RS86 significantly reduced the disease index of corn roots (disease index was 50%), and the relative control effect reached 38.27% ( Figure 5 ). The application of the fungicide significantly reduced the accumulation of hydrogen peroxide in the aboveground part of corn (Fg: 8.38 mmol / g; CK: 5.02 mmol / g; Fg+RS86: 4.60 mmol / g). This also shows that the fungicide RS86 can significantly inhibit corn root rot caused by Fusarium graminearum. Compared with the control group where only the Fv pathogen was applied (the disease index was 57%), the fungicide RS86 significantly reduced the disease index of the corn roots (the disease index was 37%), and the relative prevention effect reached 35.09% ( Figure 6 ). This shows that the fungicide RS86 can significantly inhibit corn root rot caused by Fusarium spp.

[0103] At the same time, compared with the Fg-treated plants, RS86 promoted the growth of the aboveground and roots of corn. Compared with the aboveground fresh weight of corn treated with the Fg pathogen alone (5.90g), strain RS86 increased the aboveground biomass by 31.53% to 7.76g. Compared with the blank control group (6.42g), the RS86-treated group increased the aboveground biomass by 20.87% ( Figure 5 ). Under the treatment of Fv pathogen, the fresh weight of the aboveground part of corn was 4.73g. After applying RS86, the fresh weight of the aboveground part of corn reached 5.87g, which significantly promoted the growth of the aboveground part of corn ( Figure 6 ).

[0104] In maize roots, RS86 significantly increased root fresh weight to 1.89 g compared with the pathogen Fg treatment (1.49 g), but had no significant difference compared with the blank control group (1.81 g). Figure 5 Compared with the pathogen Fv treatment (0.98 g), RS86 significantly promoted root growth, reaching 1.57 g, which was slightly lower than the blank control group, with no significant difference ( Figure 6 ).

[0105] In summary, the Rahn's bacterium RS86 described in the present invention has a good control effect on corn root rot, with a control effect of 38.27% on Fg and 35.09% on Fv; it has a good growth-promoting effect, and can increase the aboveground biomass of corn by 31.53% compared with the Fg-treated plants and 24.10% compared with the Fv-treated plants; it has beneficial functions such as producing IAA, solubilizing phosphate, fixing nitrogen, and producing iron carriers, providing a new way for the control of corn root rot.

[0106] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A strain of Rahn's bacteria ( Rahnella sp.) RS86, the deposit number of the Rahn's sp. RS86 is CCTCC NO: M20242043.

2. A microbial agent, characterized in that: The microbial agent includes the Rahn's bacterium RS86 described in claim 1.

3. The microbial agent according to claim 2, characterized in that: The number of viable bacteria of Rahn's bacterium RS86 in the microbial agent is ≥ 1×10 8 CFU / mL.

4. The method for preparing the microbial agent according to claim 2 or 3, characterized in that: The following steps are involved: The Rahn's bacterium RS86 described in claim 1 is cultured in a fermentation medium to obtain the microbial agent; the fermentation medium comprises: 1.5 g citric acid, 10.0 g glucose, 0.1 g ferric citrate ammonium, 2.0 g ammonium nitrate, 0.2 g magnesium sulfate and 1 L water.

5. The preparation method according to claim 4, characterized in that: The culture temperature is 28-30°C; the culture time is 5-7 days.

6. Use of the Rahnella RS86 according to claim 1 or the microbial agent according to claim 2 or 3 or the microbial agent prepared by the preparation method according to claim 4 or 5 in preventing and controlling plant fungal diseases and / or promoting plant growth, wherein the fungi include Fusarium graminearum ( Fusarium graminearum ) and / or Pseudomonas verticillasters ( Fusarium verticillioides ).

7. The use according to claim 6, characterized in that: The plants include corn.

8. The use according to claim 7, characterized in that: The plant fungal disease is corn root rot.

9. A method for preventing and controlling plant fungal diseases and / or promoting plant growth, characterized in that: include: The microbial agent is applied to soil planted with plants; the microbial agent is the microbial agent described in claim 2 or 3 or the microbial agent prepared by the preparation method described in claim 4 or 5; the fungi include Fusarium graminearum and / or Fusarium pseudoverticillium.

10. The method according to claim 9, characterized in that The amount of the microbial agent applied is ≥1×10 7 CFU / g soil.

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