Biocontrol strains for controlling various plant diseases and application thereof

Abstract

The application discloses a biocontrol strain for preventing and treating various plant diseases and application thereof, and belongs to the field of microorganisms. The strain is isolated from soil in a watermelon planting base in Zhenping County, Nanyang City, and is preserved in the China General Microbiological Culture Collection Center on January 19, 2024, with a preservation number of CGMCC NO.29692. The strain is a Collimonas sp. bacteria, and is classified and named as Collimonas sp. A2. The biocontrol strain can be used for preventing and treating diseases caused by watermelon wilt and diseases caused by watermelon bacterial fruit spot, and has a good application prospect. A biocontrol agent prepared from the strain A2 can be used as a biological pesticide or a biological fertilizer to prevent and treat different soil-borne diseases.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microorganisms, and particularly relates to a biocontrol strain for preventing and treating watermelon fusarium wilt and watermelon bacterial fruit blotch and application thereof. BACKGROUND

[0002] Watermelon is one of the most popular fruits in the world and is widely planted in many places. During the growth cycle of watermelon, it is often infected by diseases. Common diseases include watermelon fusarium wilt, watermelon bacterial fruit blotch, watermelon powdery mildew, watermelon anthracnose and the like. Once the watermelon is infected by these diseases during the growth process, not only the yield of watermelon will be affected, but also the quality of watermelon will be affected.

[0003] Among them, watermelon fusarium wilt is a soil-borne disease caused by Fusarium oxysporum f. sp. niveum (FON), which is very destructive and can occur at all growth stages of watermelon. The incidence rate can reach more than 50% in severe cases, which seriously affects the growth and yield of watermelon. The pathogen of the disease can easily breed and multiply in the soil, which is difficult to control and has a high infection rate. Sometimes it can even lead to crop failure. For this kind of disease, timely response and treatment are needed during planting.

[0004] Watermelon bacterial fruit blotch (BFB) is a dangerous quarantine disease, also known as bacterial spot disease. This disease mainly harms fruits and can cause rotting and other adverse phenomena in watermelon fruits. In severe cases, it can cause devastating losses. Once the disease occurs, the use of drugs for prevention and treatment has basically no good effect, and the seed with the bacteria will become an important initial infection source the next year. The occurrence of the disease seriously affects the yield and quality of watermelon and becomes another difficult problem to be solved in watermelon production.

[0005] In the early years, chemical agents were often used to prevent and control watermelon diseases. After years of research and improvement, although the existing chemical agents can achieve relatively good preliminary treatment effect for most types of diseases, chemical control generally needs to follow the rules of early use of drugs, timely use of drugs and multiple and large use of drugs, which will enhance the drug resistance of pathogenic bacteria and lead to the problem of pesticide abuse. Excessive use of chemical agents will seriously pollute agricultural products and the ecological environment and endanger human and animal health. In addition to chemical control methods, the method commonly used to cope with watermelon diseases is crop rotation. Although crop rotation does not cause secondary pollution, the space available for crop rotation is extremely limited due to the large area required for watermelon cultivation, and this method has certain difficulty in implementation.

[0006] In view of the shortcomings of chemical control method and crop rotation method, more and more planters begin to choose biological control method to prevent and control diseases relying on the development of microbial technology. Plant disease biological control mainly refers to using beneficial microorganisms or their metabolites to inhibit pathogenic bacteria, thereby preventing and controlling diseases. The essence is to use the direct or indirect competition, antibiosis and bacteriolysis of microorganisms, or the metabolites produced by microorganisms to antagonize pathogenic bacteria, so as to inhibit pathogenic bacteria. Biological control technology has the advantages of not being easy to produce resistance, not polluting the environment, being safe to people and other organisms, and being easy to obtain biological control materials, and plays an important role in integrated pest control.

[0007] Microbial inoculant is a new type of fertilizer developed in recent years on the basis of the development of microbial technology. It is prepared from beneficial microorganisms that can improve soil structure, promote plant growth or inhibit plant pathogenic bacteria. Compared with fungicides, microbial inoculants have the characteristics of no pollution, small impact on ecological system and long duration. It is urgent to develop environmentally friendly, safe and efficient microbial inoculants by using beneficial microorganisms.

[0008] Most of the biological agents for preventing and controlling watermelon diseases disclosed so far can only deal with a single disease. For example, Chinese patent CN 116849230 A discloses the application of a strain of Pseudomonas in preparing a biological agent for preventing and controlling watermelon fusarium wilt. The strain and its fermentation products can be applied in watermelon planting to inhibit the development of fusarium infection in watermelon and achieve a relatively ideal control effect. However, the strain and the microbial inoculant prepared from the fermentation products of the strain can only be used to prevent and control watermelon fusarium wilt. It is unknown whether the strain can inhibit watermelon bacterial fruit spot, and it cannot be directly inferred that the strain of Pseudomonas can be used to prevent and control both watermelon fusarium wilt and watermelon bacterial fruit spot. SUMMARY

[0009] The purpose of the present application is to find and provide a strain of Collimonas sp. A2, which can be used to prevent and control both watermelon fusarium wilt and watermelon bacterial fruit spot in the field, and has obvious effect and good application prospect.

[0010] The technical solution of the present application is: a biocontrol strain for preventing and controlling various plant diseases, which is isolated from the soil of a watermelon planting base in Zhenping County, Nanyang City. The strain was preserved in the China General Microbiological Culture Collection Center on January 19, 2024, and the preservation number is CGMCC NO. 29692. The strain is a bacterium of the genus Collimonas, and is named Collimonas sp. A2. The biocontrol strain is used to prevent and control diseases caused by watermelon fusarium wilt and watermelon bacterial fruit spot.

[0011] The 16S rRNA gene sequence of the biocontrol strain A2 is shown as SEQ ID NO. 1.

[0012] The concentration of the biocontrol strain A2 for preventing and treating the diseases caused by watermelon fusarium wilt and watermelon bacterial fruit spot is 10 7 CFU / mL.

[0013] The above-mentioned Collimonas sp. A2 can be applied in the preparation of a microbial agent for preventing and treating plant diseases.

[0014] Further, the Collimonas sp. A2 can be applied in the preparation of a microbial agent for preventing and treating watermelon fusarium wilt and watermelon bacterial fruit spot.

[0015] A biocontrol agent prepared by using the above-mentioned biocontrol strain for preventing and treating various plant diseases, wherein the biocontrol agent is a fermentation broth obtained by liquid fermentation culture of the biocontrol strain A2, and the viable cell count of the biocontrol agent is 1×10 9 CFU / mL.

[0016] The above-mentioned biocontrol agent can be applied in the preparation of a biological pesticide, which is a biological pesticide for preventing and treating watermelon fusarium wilt and watermelon bacterial fruit spot.

[0017] The beneficial effects of the present application are:

[0018] 1. The strain Collimonas sp. A2 isolated in the present application belongs to the genus Collimonas, and has the greatest advantage over the existing technology in that it has antagonistic effect on both watermelon fusarium wilt and watermelon bacterial fruit spot, and has obvious effect and good application prospect; the biological control preparation prepared from the Collimonas sp. can be used as a biological pesticide or a biological fertilizer, and can be used for efficiently preventing and treating various plant soil-borne diseases including watermelon fusarium wilt and watermelon bacterial fruit spot;

[0019] 2. The present application discloses an antagonistic strain having effect on both watermelon fusarium wilt and watermelon bacterial fruit spot, which provides a new strain resource for the development of microbial resources and the use in plant soil-borne disease prevention and treatment;

[0020] 3. The use of the strain A2 for treating watermelon fusarium wilt and watermelon bacterial fruit spot belongs to biological control means, and does not cause obvious secondary pollution problem, and has low overall treatment cost, low consumption, high efficiency, and various action conditions, and is suitable for large-scale popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a colony morphology diagram of the strain A2;

[0022] Figure 2The phylogenetic tree of strain A2;

[0023] Figure 3 The inhibition effect of S. montanicola A2 on Fusarium oxysporum f. sp. niveum is shown in the figure, and the left photo is the control pathogen, and the right photo is the inhibition effect of S. montanicola A2 on the pathogen;

[0024] Figure 4 The inhibition effect of S. montanicola A2 on the pathogen of bacterial fruit blotch of watermelon is shown in the figure, and the left photo is the control pathogen, and the right photo is the inhibition effect of S. montanicola A2 on the pathogen;

[0025] Figure 5 The indoor control effect of S. montanicola A2 on Fusarium oxysporum f. sp. niveum is shown in the figure;

[0026] Figure 6 The indoor control effect of S. montanicola A2 on the pathogen of bacterial fruit blotch of watermelon is shown in the figure. DETAILED DESCRIPTION

[0027] The following examples further illustrate the content of the present application, but should not be understood as limiting the present application. Modifications and replacements of the methods, steps or conditions of the present application, without departing from the essence of the present application, all belong to the scope of the present application.

[0028] The pathogenic bacteria are Fusarium oxysporum f. sp. niveum and Bacterial fruit blotch of watermelon (BFB), and the Fusarium oxysporum f. sp. niveum is isolated from the roots of a field watermelon fusarium wilt plant, and the Bacterial fruit blotch of watermelon is isolated from the leaves of a diseased plant, and has undergone pathogenic identification and pathogenicity detection.

[0029] Test sample and culture medium

[0030] The antagonistic bacteria provided in the present application are derived from soil collected in a watermelon planting base in Zhenping County, Nanyang City in August 2022, and are obtained through artificial enrichment culture, pressure screening and isolation and purification. The bacteria belong to the genus S. montanicola bacteria, and are named Collimonas sp. A2.

[0031] KB liquid culture medium: 20 g of proteose peptone, 10 mL of glycerol, 1.5 g of K2HPO4, 3.075 g of MgSO4·7H2O, and distilled water to 1000 mL, sterilized at 121℃ for 20 min to obtain KB liquid culture medium.

[0032] KB solid medium: proteose peptone 20 g, glycerol 10 mL, K2HPO4 1.5 g, MgSO4·7H2O 3.075 g, agar 18 g, distilled water to 1000 mL, boil and mix, sterilize at 121℃ for 20 min, get KB solid medium.

[0033] LB liquid medium: tryptone 10 g, yeast extract 5.0 g, NaCl 5.0 g, distilled water to 1000 mL, sterilize at 121℃ for 20 min, get LB liquid medium.

[0034] LB solid medium: tryptone 10 g, yeast extract 5.0 g, NaCl 5.0 g, agar 18 g, distilled water to 1000 mL, boil and mix, sterilize at 121℃ for 20 min, get LB solid medium.

[0035] PDB liquid medium: peel potato 200 g, cut into small pieces, boil in water for 30 min, filter with 4 layers of gauze, add 20 g glucose, distilled water to 1000 mL, boil and mix, sterilize at 121℃ for 20 min, get PDB liquid medium.

[0036] PDA solid medium: peel potato 200 g, cut into small pieces, boil in water for 30 min, filter with 4 layers of gauze, add 20 g glucose and 18 g agar, distilled water to 1000 mL, boil and mix, sterilize at 121℃ for 20 min, get PDA solid medium.

[0037] 1. Strain screening and physiological and biochemical characteristics research

[0038] 1.1 Isolation and screening of strain A2

[0039] Put 10 g of soil sample into 90 mL of sterile water, shake evenly to get 10 -1 concentration of bacterial solution, use 1 mL of sterile pipette to transfer 1 mL of 10 -1 concentration of bacterial solution to 9 mL of sterile water, shake well to get 10 -2 concentration of bacterial solution, use the same method to dilute to 10 -4 , 10 -2 , 10 -3 and 10 -4 concentration of soil bacterial solution respectively, spread on LB plates, dry and invert in a 25℃ incubator for 5-7 days. Pick single colonies and transfer to LB plates for purification culture, identify as bacteria under microscope, number and transfer to KB slant for culture, store in refrigerator after growth. Take strain A2 numbered in the early test for further identification.

[0040] 1.2 Morphological, physiological and biochemical characteristics analysis of strain A2

[0041] The strain was cultured on LB plate for 24 h (30°C).

[0042] Strain A2 was inoculated on KB solid medium and cultured at 28°C to observe the colony morphology. The results showed that strain A2 grew slowly on KB solid medium, and the colony was purple with water spot on the surface (see Figure 1). Figure 1

[0043] 1.3 Physiological and biochemical characteristics of strain A2

[0044] The optimum growth temperature of strain A2 was 28°C, the optimum growth pH was 7.0, and the activities of oxidase, catalase, alkaline phosphatase, leucine arylamidase, acid phosphatase and naphthol-AS-BI-phosphohydrolase were positive. Strain A2 could grow by itself using bromosuccinic acid, D-fructose, D-galactose, a-D-glucose, L-asparagine, D-glucuronate, L-glutamate, D-mannitol, b-hydroxybutyric acid and malic acid.

[0045] 1.4 Phylogenetic analysis

[0046] Phylogenetic analysis was performed based on 16S rRNA gene sequence to determine the accurate taxonomic position of strain A2. Strain A2 was cultured in KB liquid medium at 28°C for 48 h, and genomic DNA was extracted. The 16S rRNA gene sequence of the strain was amplified using universal bacterial primers: 27F: 5'-AGAGTTTGATCCTGGCTCAG-3' (SEQ ID NO. 2), 1492R: 5'-TACGGCTACCTTGTTACGACTT-3' (SEQ ID NO. 3). After purification of the amplification product, sequencing was performed in both directions, and phylogenetic tree was constructed by online alignment (www.ezbiocloud.net).

[0047] Using the genomic DNA of strain A2 as template and 16S rRNA gene universal primers as primers, PCR amplification was performed to obtain a total length of 1411 bp of gene sequence SEQ ID NO. 1.

[0048] The sequence of SEQ ID NO. 1 is as follows:

[0049] TAACATGCAGTCGACGGTAACAGGGAGCTTGCTCCGCTGACGAGTGG

[0050] CGAACGGGTGAGTAATATATCGGAACGTACCTTTGAGTGGGGGATAACTAG ​

[0051] TCGAAAGATTAGCTAATACCGCATACGATCTACGGATGAAAGTGGGGGATC

[0052] GCAAGACCTCATGCTCATAGAGCGGCCGATATCTGATTAGCTAGTTGGTGA

[0053] GGTAAAGGCTCACCAAGGCTTCGATCAGTAGCTGGTCTGAGAGGACGACC

[0054] AGCCACACTGGGACTGAGACACGGCCCAGACTCCTACGGGAGGCAGCAGT

[0055] GGGGAATTTTGGACAATGGGGGCAACCCTGATCCAGCAATGCCGCGTGAG

[0056] TGAAGAAGGCCTTCGGGTTGTAAAGCTCTTTTGTCAGGGAAGAAACGGGA

[0057] TGTCCTAATACGATGTCCTAATGACGGTACCTGAAGAATAAGCACCGGCTA

[0058] ACTACGTGCCAGCAGCCGCGGTAATACGTAGGGTGCAAGCGTTAATCGGAA

[0059] TTACTGGGCGTAAAGCGTGCGCAGGCGGTTATGTAAGACAGGTGTGAAATC

[0060] CCCGGGCTTAACCTGGGAATGGCATTTGTGACTGCATAGCTAGAGTGTGTC

[0061] AGAGGGGGGTAGAATTCCACGTGTAGCAGTGAAATGCGTAGAGATGTGGA

[0062] GGAATACCGATGGCGAAGGCAGCCCCCTGGGATAACACTGACGCTCATGC

[0063] ACGAAAGCGTGGGGAGCAAACAGGATTAGATACCCTGGTAGTCCACGCCC

[0064] TAAACGATGTCTACTAGTTGTCGGGTCTTAATTGACTTGGTAACGCAGCTAA

[0065] CGCGTGAAGTAGACCGCCTGGGGAGTACGGTCGCAAGATTAAAACTCAAA

[0066] GGAATTGACGGGGACCCGCACAAGCGGTGGATGATGTGGATTAATTCGATG

[0067] CAACGCGAAAAACCTTACCTACCCTTGACATGTACAGAATCCCGAAGAGAT

[0068] TTGGGAGTGTTCGAAAGAAAACTGTAACACAGGTGCTGCATGGCTGTCGT

[0069] CAGCTCGTGTCGTGAGATGTTGGGTTAAGTCCCGCAACGAGCGCAACCCTT

[0070] GTCATTAGTTGCTACGAAAGGGCACTCTAATGAGACTGCCGGTGACAAACC

[0071] GGAGGAAGGTGGGGATGACGTCAAGTCCTCATGGCCCTTATGGGTAGGGC

[0072] TTCACACGTCATACAATGGTACATACAGAGGGCCGCCAACCCGCGAGGGG

[0073] GAGCTAATCCCAGAAAGTGTATCGTAGTCCGGATTGTAGTCTGCAACTCGA

[0074] CTACATGAAGTTGGAATCGCTAGTAATCGCGGATCAGCATGTCGCGGTGAAT

[0075] ACGTTCCCGGGTCTTGTACACACCGCCCGTCACACCATGGGAGCGGGTTTT

[0076] ACCAGAAGTAGGTAGCCTAACCGTAAGGAGGGCGCTACCACGTAGAT

[0077] The sequence was aligned in EzBioCloud database (https: / / www.ezbiocloud.net), the results showed that the similarity of strain A2 with Collimonas pratensis Ter91 reached 99.2%, the similarity with Collimonas fungivorans Ter6 reached 98.6%, and the similarity with other strains was less than 98.5%. The phylogenetic tree of strain A2 was constructed according to the Neighbor-joining method, the results showed that strain A2 was located in the cluster of Collimonas genus, among which Collimonas fungivorans Ter6 and Collimonas pratensis Ter91 were on the same branch, the closest distance, combined with the colony morphological characteristics, strain A2 was classified as Collimonas sp. A2. T T T T

[0078] 1.5 Preservation information of strain A2

[0079] Strain A2 was preserved in China General Microbiological Culture Collection Center on January 19, 2024, with the preservation number of CGMCC NO. 29692, and the classification and naming of the strain is Collimonas sp. A2.

[0080] 2. Study on the biocontrol effect of Collimonas sp. A2:

[0081] Collimonas sp. A2 was inoculated in KB liquid medium and cultured at 28℃ with 180r / min shaking for 24h for standby.

[0082] The inhibition zone method was used, and Fusarium oxysporum f. sp. niveum was used as the pathogen. The pathogen was inoculated in PDB culture solution and cultured for 4d, then melted and cooled to about 40℃ PDA solid medium was added, the volume ratio of pathogen culture solution to solid medium was 1:200, 20mL medium was poured into a 9cm diameter flat plate. After cooling and solidification, a 7mm diameter hole was punched in the middle of the plate with a puncher, and 50μL of Collimonas sp. liquid was added in the hole. Place in a 28℃ constant temperature incubator for culture, record the inhibition zone diameter after 5d.

[0083] ​​​​The inhibition zone method was used, with bacterial fruit blotch of watermelon (BFB) as the pathogenic bacteria. The pathogenic bacteria were inoculated in LB culture solution and cultured for 16-24 h, then added to molten LB solid medium (the volume ratio of pathogenic bacteria culture solution to solid medium was 1:200) cooled to about 40°C, and poured into 20 mL of medium in a 9 cm diameter plate. After cooling and solidification, a 7 mm diameter hole was punched in the middle of the plate with a puncher, and 50 μL of S. montanum bacterial solution was added to the hole. The plate was placed in a 28°C constant temperature incubator for culture, and the diameter of the inhibition zone was recorded after 24 h.

[0084] The S. montanum was found to have inhibitory effects on both Fusarium oxysporum and BFB by the inhibition zone method.

[0085] The inhibitory rate of S. montanum on F. oxysporum was 32.64±2.16%, and the inhibitory rate on BFB was 38.42±4.36%, indicating that S. montanum had good inhibitory activity on both F. oxysporum and BFB.

[0086] 3. Verification of the indoor control effect of S. montanum A2 on F. oxysporum

[0087] 3.1 Preparation of S. montanum bacterial solution

[0088] The well-grown S. montanum A2 strain on the plate was picked up with a sterilized toothpick and inoculated into a 500 mL triangular flask containing 200 mL of KB liquid medium, and cultured at 28°C and 180 r / min for 1 d to obtain S. montanum bacterial solution (10 9 CFU / mL).

[0089] 3.2 Indoor control effect of S. montanum on F. oxysporum

[0090] The watermelon was conventionally sowed and grown in a greenhouse nursery tray, and the watermelon variety was Meidu. Three treatments of 100-fold and 200-fold dilution of the bacterial agent and CK were set up, and the watermelon seedlings with uniform growth were transplanted into flowerpots, 5 pots for each treatment. The treatment groups were respectively irrigated with 20 mL of S. montanum bacterial solution diluted 100-fold and 200-fold, and the control group CK was irrigated with an equal amount of water, and then inoculated with 5 mL of F. oxysporum (FON) spore suspension (10 7 / mL). At 14 d, the treatment groups were respectively irrigated with 20 mL of S. montanum bacterial solution diluted 100-fold and 200-fold, and the control group CK was irrigated with an equal amount of water. At 26 d, the disease index of watermelon fusarium wilt was investigated and counted, and the control effect of S. montanum was calculated.

[0091] The watermelon wilt grading standard: 0 level is normal stem vascular bundle, no symptoms outside; 1 level is stem vascular bundle 25% or less discoloration; 3 level is stem vascular bundle 25%-50% discoloration; 5 level is stem vascular bundle 51%-75% discoloration; 7 level is stem vascular bundle 75% or more discoloration, partial leaf wilting; 9 level is whole plant dead.

[0092] Disease index = Σ (number of each level of diseased plants x the value of the disease level) / (total number of plants surveyed x the value of the highest level) x 100%;

[0093] Relative control efficiency (%) = (disease index of the control group - disease index of the treatment group) / disease index of the control group x 100%.

[0094] The pot experiment results are as follows, and the statistical results show that the 100-fold dilution of the S. montanum bacterial liquid has the best prevention and control effect on watermelon wilt, which is 75.47%, therefore, the 100-fold dilution is the best dilution for the bacterial agent to prevent and control watermelon wilt.

[0095]

[0096] The lower case letters are significant difference analysis.

[0097] 4. Verification of the field control effect of S. montanum A2 on watermelon Fusarium wilt

[0098] The better dilution concentration in the above indoor pot experiment is used for field test, and the field test is carried out in a watermelon planting base in Zhenping County, Nanyang City, Henan Province. The preparation method of the S. montanum bacterial liquid is the same as above. Three treatments of 100-fold S. montanum A2 bacterial liquid, 1000-fold 30% hymexazol aqueous agent and water control (CK) are set, each treatment is repeated 3 times. After the watermelon seedlings emerge for 15 days, the 100-fold bacterial liquid, 1000-fold 30% hymexazol aqueous agent and water are drip irrigated once, after 30 days, the three treatments are drip irrigated again according to the above concentrations, 30 days after the last root irrigation, 20 plants are randomly taken from each repeat of each treatment, the disease index is counted, the control efficiency is calculated, and the grading standard and calculation method are the same as those in Example 3.

[0099] The test results are as follows, and the field prevention and control effect test shows that the 100-fold dilution of the S. montanum bacterial liquid has a field control efficiency of 77.77%, which is not much different from the control efficiency of 81.79% of the conventional 30% hymexazol aqueous agent, and both can effectively prevent and control the occurrence of watermelon wilt, and have good popularization and utilization value in production.

[0100]

[0101] The lower case letters are significant difference analysis

[0102] 5. Verification of the indoor control effect of S. montanum A2 on watermelon bacterial fruit spot

[0103] Watermelon was conventionally sowed in greenhouse seedling tray, and the watermelon variety was Meidu. The preparation method of Pseudomonas monteilii bacterial liquid was the same as above. Three treatments of 100 times, 200 times dilution of bacterial agent and CK were set, and the watermelon seedlings with uniform growth were transplanted into flowerpots, 5 pots for each treatment. 20 mL of Pseudomonas monteilii bacterial liquid diluted 100 times and 200 times was poured into each flowerpot of the treatment group, and then the flowerpots were placed in the greenhouse for culture, 28°C, relative humidity above 70%, and 16 / 8h photoperiod. Only a small amount of water was poured to keep the soil moist on the second and third days, and then regular watering was carried out. The biocontrol bacteria were sprayed on the plant leaves again at 15d, and the pathogenic bacteria were inoculated 5 days after the second inoculation of antagonistic bacteria, the inoculation concentration of pathogenic bacteria was 10 7 CFU / mL, 10d after inoculation, the incidence rate was counted, and the control effect was calculated.

[0104] Incidence rate % = number of diseased plants in the treatment / total number of plants in the treatment x 100%;

[0105] Control effect % = (disease incidence rate of the control - disease control rate of the treatment) / disease incidence rate of the control x 100%;

[0106] The results of the pot experiment are as follows, which show that the 100 times diluted Pseudomonas monteilii bacterial liquid has the best control effect on watermelon bacterial fruit spot disease, which is 72.44%, therefore, 100 times is the best dilution multiple of the bacterial agent for controlling watermelon bacterial fruit spot disease.

[0107]

[0108]

[0109] The lower case letters are significant difference analysis.

[0110] 6. Verification of field control effect of Pseudomonas monteilii A2 on watermelon bacterial fruit spot pathogen

[0111] According to the better dilution concentration of the above indoor pot experiment, field experiments were carried out in a watermelon planting base in Zhenping County, Nanyang City, Henan Province, and the preparation method of Pseudomonas monteilii bacterial liquid was the same as above. Two treatments of Pseudomonas monteilii bacterial liquid 100 times and water control were set, and each treatment had 3 repeats. After the watermelon seedlings emerged for 15 days, the bacterial liquid 100 times and water were drip irrigated once, and after 30 days, the two treatments were drip irrigated again according to the above concentration. 30 days after the last irrigation, 20 plants were randomly selected from each repeat of each treatment, the disease index was counted, the control effect was calculated, and the grading standard and calculation method were the same as in Example 3.

[0112] The results of the field control experiment are as follows, which show that the Pseudomonas monteilii bacterial liquid diluted 100 times has a control effect of 59.97%, which can effectively control the occurrence of watermelon bacterial fruit spot disease, and has good popularization and utilization value in production.

[0113]

[0114] The essential principles, main features and advantages of the present application are shown and described above. However, the above description is only specific embodiments of the present application, and the technical features of the present application are not limited thereto. Any other embodiments obtained by those skilled in the art without departing from the technical solutions of the present application should be covered in the patent scope of the present application.

Claims

1. Biocontrol bacterial strains for controlling a plurality of plant diseases, characterized in that, The strain is isolated from a watermelon planting base soil in Zhenping County, Nanyang City, and the strain is preserved in China General Microbiological Culture Collection Center on January 19, 2024, with a preservation number of CGMCC NO.29692; the strain is a Shigamonsaurella bacterium, and is classified and named as Shigamonsaurella sp. Collimonas A2. The biocontrol strain is used for preventing and treating the diseases caused by watermelon fusarium wilt and watermelon bacterial fruit spot.

2. The biocontrol bacterial strain for controlling various plant diseases according to claim 1, wherein, The 16S rRNA gene sequence of the biocontrol strain is shown as SEQ ID NO.

1.

3. The biocontrol bacterial strain for controlling various plant diseases according to claim 1, wherein, The biocontrol strain can be used to prevent and treat watermelon wilt and watermelon bacterial fruit spot caused by the pathogen, and the concentration of the pathogen is 10 7 CFU / mL.

4. Use of a biocontrol strain according to any one of claims 1 to 3, characterized in that, Application of the mountain lake single cell A2 in preparing a bacterial agent for preventing and treating watermelon fusarium wilt and watermelon bacterial fruit spot.

5. A biocontrol agent, characterized in that, The biocontrol agent is prepared according to any one of claims 1-3 for preventing and treating various plant diseases, wherein the biocontrol agent is a fermentation broth obtained by liquid fermentation culture of the biocontrol strain A2, and the viable cell count of the biocontrol agent is 1 x 10 9 CFU / mL.

6. Use of the biocontrol agent according to claim 5 for the preparation of a biopesticide, characterized in that, The biological pesticide is a biological pesticide for preventing and treating watermelon fusarium wilt and watermelon bacterial fruit spot.

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