Biocontrol strain streptomyces rochei 7F2 as well as fungicide and application thereof

Abstract

The invention relates to a biocontrol strain streptomyces rochei 7F2 as well as a microbial inoculum and application of the biocontrol strain streptomyces rochei 7F2. The biocontrol strain is Streptomyces rochei 7F2, and the preservation number of the biocontrol strain is CGMCC (China General Microbiological Culture Collection Center) NO. 32196. The biocontrol inoculant contains the biocontrol strain or a fermentation broth thereof. The composition is specifically applied to prevention and treatment of wheat basal stem rot or wheat scab. The biocontrol strain can effectively inhibit fusarium pseudograminearum and fusarium graminearum, and is suitable for preventing and treating wheat stem rot and wheat scab.

Description

Technical Field

[0001] The invention relates to a biocontrol strain Streptomyces loucheri 7F2, a bacterial agent and application thereof, and belongs to the technical field of agricultural biocontrol bacteria. Background Art

[0002] Fusarium spp. are a large and diverse group of ascomycetes that produce sickle-shaped conidia, encompassing numerous plant pathogens. Fusarium graminearum, when infecting wheat, can cause wheat head blight, while Fusarium pseudograminearum, when infecting wheat, can cause wheat stem rot. These two Fusarium diseases in wheat not only cause severe yield losses but also produce a variety of mycotoxins, including 3-acetyl-deoxynivalenol (3AcDON), 15-acetyl-deoxynivalenol (15AcDON), and nivalenol (NIV), which can cause vomiting and immune impairment in humans and animals, posing a health threat.

[0003] Currently, the prevention and control of wheat stem rot and ergot mainly rely on chemical fungicides, but there are problems such as a small number of fungicides to choose from, large field dosages, and unstable control effects. As an environmentally friendly, safe for humans and animals, and cost-effective prevention method, biological control has been widely recognized in global agricultural production. Streptomyces is a commonly used biocontrol actinomycete that produces antibiotics, cell wall-degrading enzymes and other bioactive substances that can inhibit the growth of plant pathogens. Currently, there are limited biocontrol resources for wheat stem rot and ergot caused by Fusarium spp., and it is of great significance to find strains with high biocontrol effects against these two pathogenic Fusarium spp.

[0004] After searching, it was found that the invention patent with patent number 201810357031.0 and authorization announcement number CN108300681B disclosed a strain of Streptomyces rocheri Z331-A. Although this strain can prevent and control a variety of plant pathogenic fungi, Gram-negative bacteria and Gram-positive bacteria, the only one related to wheat is Fusarium graminearum (i.e., wheat fusarium rust), and its antibacterial rate is only 39.66%, and the antibacterial effect is not strong enough.

[0005] The inventor team of the present invention has achieved research results by developing biocontrol strains for preventing and treating wheat stem base rot and ergot. Excellent prevention and control effects can be achieved for wheat stem base rot and ergot. This achievement is now applied for a patent for the present invention. Summary of the Invention

[0006] The main purpose of the present invention is to overcome the problems of the prior art and provide a biocontrol strain, Streptomyces rocheri 7F2, that can effectively inhibit Fusarium graminearum and Fusarium graminearum, thereby controlling wheat stem rot and head blight. Also provided are corresponding biocontrol agents and applications.

[0007] The technical solution of the present invention to solve the technical problem is as follows:

[0008] The invention discloses a biocontrol strain, namely Streptomyces rochei 7F2, which is deposited in the China General Microbiological Culture Collection Center with a deposit number of CGMCC NO.32196.

[0009] Fermentation broth of the biocontrol strains mentioned above.

[0010] The present invention also provides:

[0011] A method for preparing a biocontrol strain fermentation broth comprises the following steps:

[0012] The first step is to culture the aforementioned biocontrol strain on a Gao's No. 1 medium plate, take a bacterial plate, place the bacterial plate into Gao's No. 1 liquid medium, and culture with shaking at 25°C ± 1°C to obtain a fermentation mixture.

[0013] The second step is to filter the fermentation mixture, centrifuge the obtained liquid to obtain the supernatant, and pass the supernatant through a bacterial filter to remove spores, thereby obtaining the biocontrol strain fermentation liquid.

[0014] Preferably, in the first step, the diameter of the bacterial plate is 5±1 mm, the number of bacterial plates is: the volume of Gao's No. 1 liquid culture medium = 5: 100±10 mL; the culture conditions are: rotation speed of 200-250 r / min, and time for at least 7 days.

[0015] Preferably, in the first step, Gao's medium No. 1 is composed of the following components: soluble starch 20 g, NaCl 0.5 g, KNO 3.1 g, K2HPO4·3H2O 0.5 g, MgSO4·7H2O 0.5 g, FeSO4·7H2O0.01 g, agar 20 g, ddH2O 1 L, and the pH is adjusted to 7.4-7.6.

[0016] Preferably, in the second step, at least three layers of sterile filter cloth are used for filtration; the centrifugation conditions are: 5000-6000 rpm at 25°C ± 1°C for at least 8 minutes; and the pore size of the bacterial filter is less than or equal to 0.22 μm.

[0017] The present invention also provides:

[0018] The biocontrol strain or its fermentation liquid is used to prepare a biocontrol agent for inhibiting pseudofusarium graminearum and Fusarium graminearum.

[0019] The biocontrol strain or its fermentation liquid is used to prepare a biocontrol agent for preventing and treating wheat stem base rot or wheat scab.

[0020] The present invention also provides:

[0021] A biocontrol agent contains the biocontrol strain or its fermentation liquid.

[0022] The biocontrol agent described above is used for preventing and controlling wheat stem base rot or wheat scab.

[0023] The biocontrol strain Streptomyces rochei (S. rochei) 7F2 of the present invention can effectively inhibit F. pseudograminearum (F. pseudograminearum) and F. graminearum (F. graminearum), and is suitable for preventing and controlling wheat stem base rot and wheat scab. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The colony morphology of strain 7F2 in Example 1 of the present invention is shown in the figure on the left, and the colony morphology of strain 7F2 in Example 1 of the present invention is shown in the figure on the right, wherein the colony morphology of strain 7F2 ...

[0025] Figure 2 This is the phylogenetic tree of actinomycetes constructed based on the 16S rDNA gene in Example 1 of the present invention.

[0026] Figure 3 This is the phylogenetic tree of actinomycetes constructed based on the gyrB gene in Example 1 of the present invention.

[0027] Figure 4 The results of the antagonistic effect of strain 7F2 on Fusarium graminearum and Fusarium pseudograminearum on plates in Example 2 of the present invention are shown. The Fusarium pseudograminearum is Fusarium pseudograminearum CF14047, the Fusarium graminearum is Fusarium graminearum PH-1, and the CK group is a blank control.

[0028] Figure 5 Figure 2 shows the inhibitory effects of different concentrations of fermentation broth of strain 7F2 on F. graminearum and F. graminearum in Example 2. Figure A shows the experimental results against F. graminearum CF14047, and Figure B shows the experimental results against F. graminearum PH-1. Group CK is a blank control.

[0029] Figure 6 This is a diagram showing the incidence of wheat coleoptile stem rot under different treatments in Example 2 of the present invention.

[0030] Among them, the CK group served as the blank control.

[0031] Figure 7This is a diagram showing the incidence of wheat stem rot under different treatments in Example 3 of the present invention.

[0032] Figure 8 This is a diagram showing the growth of wheat under different treatments according to Example 3 of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described below by way of examples, but the present invention is not limited to these examples. The reagents involved in the present invention are all commercially available. The experimental methods of the following examples, unless otherwise specified, are all conventional methods.

[0034] Example 1

[0035] This example is about bacterial strain isolation and identification.

[0036] The specific contents of this embodiment are as follows:

[0037] (1) Separation

[0038] The inventors' team collected soil samples from a wheat field at a base of the Jiangsu Academy of Agricultural Sciences. Debris and fallen leaves were removed using a 0.9mm soil sieve. 5g of each soil sample was weighed and placed into a conical flask containing 45mL of sterile water. The samples were shaken at 150 rpm for 30 minutes. The soil solution was then diluted in a gradient, and 100μL of the appropriate dilution was spread onto a plate of Gao's medium No. 1. The samples were incubated in the dark at 25°C for 4-7 days. Based on the color and morphology of the colonies, a pure strain was obtained after three streaking purifications, designated strain 7F2.

[0039] Note: Gao's medium No. 1 has the following formula: soluble starch 20 g, NaCl 0.5 g, KNO 3.1 g, K₂HPO₄·3H₂O 0.5 g, MgSO₄·7H₂O 0.5 g, FeSO₄·7H₂O 0.01 g, agar 20 g, ddH₂O 1 L, pH adjusted to 7.4-7.6. Same below.

[0040] (2) Identification

[0041] According to the method of "Berger's Manual of Bacterial Identification" (8th edition), the morphological characteristics of strain 7F2 were identified, and the specific results are as follows:

[0042] (i) Morphological characteristics:

[0043] The single colony of strain 7F2 on Gao's medium No. 1 is round, smooth, and protrudes toward the surface of the medium. The colony is white or light yellow as a whole and no soluble pigment is produced. Figure 1 shown.

[0044] (ii) Gene sequence characteristics:

[0045] The genomic DNA of strain 7F2 was extracted using a bacterial genomic DNA extraction kit (Beijing Solebaugh Technology Co., Ltd.) and used as a template. PCR amplification was performed using universal primers for the 16S rRNA gene and primers for the gyrB gene as follows.

[0046] The universal primers for the 16S rRNA gene are:

[0047] 27F: 5'-agagtttgatcctggctcag-3' (SEQ ID NO: 1)

[0048] 1492R: 5'-ggttaccttgttacgactt-3' (SEQ ID NO: 2)

[0049] The 25 μL reaction system consisted of: 12.5 μL Taq PCR Mix premix (Sangon Biotech (Shanghai) Co., Ltd.); 1 μL each of primers 27F and 1492R; 1 μL of strain 7F2 genomic template; and 9.5 μL ddH2O.

[0050] The reaction conditions were: 95°C for 10 min; 95°C for 30 s, 55°C for 30 s, and 72°C for 45 s, 30 cycles; and 72°C for 10 min.

[0051] The primers for the gyrB gene are:

[0052] PF-1: 5'-gaggtcgtgctgaccgtgctgcacgcgggcggcaagttcggc-3' (SEQ ID NO: 3)

[0053] PR-2: 5'-gttgatgtgctggccgtcgacgtcgacgtcggcgtccgccat-3' (SEQ ID NO: 4)

[0054] The 25 μL reaction system consists of: 12.5 μL Taq PCR Mix premix; 1 μL each of primers 27F and 1492R; 1 μL of strain 7F2 genomic template; and 9.5 μL ddH2O.

[0055] The reaction conditions were: 94°C for 5 min; 95°C for 30 s, 60°C for 1 min, 72°C for 1 min, 35 cycles; 72°C for 5 min.

[0056] The PCR amplification products were sequenced (Shanghai Sangon Biotech Co., Ltd.) to obtain 1425 bp 16S rRNA gene sequence and 1303 bp gyrB gene sequence.

[0057] 16S rRNA gene sequence (SEQ ID NO: 5):

[0058] gcatgggggtcttacacatgcagtcgacgatgaaccacttcggtggggattagtggcgaacgggtgagtaacacgtgggcaatctgccctgcactctgggaca

[0059] agccctggaaacggggtctaataccggatactgatcctcgcaggcatctgcgaggttcgaaagctccggcggtgcaggatgagcccgcggcctatcagctagt

[0060] tggtgaggtaacggctcaccaaggcgacgacgggtagccggcctgagagggcgaccggccacactgggactgagacacggcccagactcctacgggagg

[0061] cagcagtggggaatattgcacaatgggcgaaagcctgatgcagcgacgccgcgtgagggatgacggccttcgggttgtaaacctctttcagcagggaagaag

[0062] cgaaagtgacggtacctgcagaagaagcgccggctaactacgtgccagcagccgcggtaatacgtagggcgcaagcgttgtccggaattattgggcgtaaag

[0063] agctcgtaggcggcttgtcacgtcggttgtgaaagcccggggcttaaccccgggtctgcagtcgatacgggcaggctagagttcggtaggggagatcggaatt

[0064] cctggtgtagcggtgaaatgcgcagatatcaggaggaacaccggtggcgaaggcggatctctgggccgatactgacgctgaggagcgaaagcgtggggag

[0065] cgaacaggattagataccctggtagtccacgccgtaaacggtgggcactaggtgtgggcaacattccacgttgtccgtgccgcagctaacgcattaagtgcccc

[0066] gcctggggagtacggccgcaaggctaaaactcaaaggaattgacgggggcccgcacaagcggcggagcatgtggcttaattcgacgcaacgcgaagaacc

[0067] ttaccaaggcttgacatacaccggaaaaccctggagacagggtcccccttgtggtcggtgtacaggtggtgcatggctgtcgtcagctcgtgtcgtgagatgttg

[0068] ggttaagtcccgcaacgagcgcaacccttgtcccgtgttgccagcaggcccttgtggtgctggggactcacgggagaccgccggggtcaactcggaggaagg

[0069] tggggacgacgtcaagtcatcatgccccttatgtcttgggctgcacacgtgctacaatggccggtacaatgagctgcgataccgcgaggtggagcgaatctcaa

[0070] aaagccggtctcagttcggattggggtctgcaactcgaccccatgaagtcggagtcgctagtaatcgcagatcagcattgctgcggtgaatacgttcccgggcct

[0071] tgtacacaccgcccgtcacgtcacgaaagtcggtaacacccgaagccggtggcccaaccccttgtgggagggagcttcgaagttgactgactt

[0072] gyrB gene sequence (SEQ ID NO:6):

[0073] ctaggcgctattccagcgatgatcttgtgatagcggagcttctcgatgtcgaagtcctcgtgcacgcccgtgccgaacgcggagatcatcgcctggatctcctggt

[0074] tctgcaggatgcggtcgatgcgcgccttctcgacgttgaggatcttgccgcggatcgggaggatcgcctggtactgcgggttgcggccggacttggccgagcc

[0075] gccggcggagtcgccctcgacgatgaagatctcgcacttggtcgggtcgttcgactggcagtcggacagcttgcccggcagcgacgccgtctccagcaggcc

[0076] cttgcgacgcgtcaggtcgcgggccttgcgggccgccacgcgcgcgtgggccgcctggatgcccttgcggatgatgtccgcggcctcgttcgggttgcggtc

[0077] gagccagtcggtcaggtgctcgtagacgaccttctggacgaaggtcttcacctcggtgttgccgagcttcgtcttggtctggccctcgaactggggctcgctcag

[0078] cttcaccgagatgatcgcggtcagaccctcgcggatgtcgtcgcccgtgaggttgtcgtccttctcgcgcagcagcttcttgtcgcgcgcgtacttgttgatcagc

[0079] gaggtgagcgccgcgcggaagccctcctcgtgggtgccgccctcgtgggtgtggatgatgttggcgaaggagtagacaccctcggtgtagccgccgttccac

[0080] tgcatggccacctcgagggacaggttcttgtccttgtcctcggcctcgaggtcgatcacggtggggtgcaccagctctcccttgcggggagttgaggtacttcacg

[0081] aagtcgacgatgccgccctcgtagtggtacgagacgctcttgacctcgtgcttctcgtcctcaccggcctcgtccgcaccggcggtggccttggccgactcgcg

[0082] ctcgtcggtgaggttgatcctcaggcccttgttgaggaaggccatctcctggaagcgccggggagagcgtctcgaaggagtagtcggtggtctcgaagatgtcgc

[0083] cgtcggcccagaaggtgaccgacgtgccggtctcctcggtggcctcgtgccgggcgagcgacgccgtggggacacccagcttgtagtcctgggtccagcgg

[0084] tagccgtcggtcttgacctccaccgcgaccctcgtggagagggcgttgacgacggagacgcccacaccgtgcagaccaccggagaccgcgtagccgccgc

[0085] ccccgaacttgccgcccgcgtgcagcacggtcacaacgacctcacctcgctatcaaacaagta

[0086] Phylogenetic methods were used to identify 7F2. The 16S rRNA gene sequences were subjected to BLAST analysis and comparison, and strain 7F2 was preliminarily identified as an actinomycete of the genus Streptomyces. The gyrB gene sequences were then compared, and sequences of different strains with high homology were taken and the sequences of actinomycetes were used to construct a phylogenetic tree using the neighbor-joining method using MEGA 11. Finally, 7F2 and Streptomyces rochei were clustered in the same branch. The results are as follows Figure 2 and Figure 3 shown.

[0087] Based on morphological and gene sequence characteristics, strain 7F2 was finally identified as Streptomyces rochei (S. rochei).

[0088] (3) Preservation

[0089] The strain 7F2 was sent to the China General Microbiological Culture Collection Center (CGMCC) for preservation, whose address is No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, Postal Code 100101, with the deposit number CGMCC NO.32196 and the deposit date being October 12, 2024.

[0090] Example 2

[0091] This example is an antibacterial test against Fusarium graminearum PH-1 and Pseudomonas graminearum CF14047.

[0092] The specific contents of this embodiment are as follows:

[0093] (1) The plate confrontation culture method was used to test the inhibitory effect of strain 7F2 on Fusarium graminearum PH-1 and Pseudomonas graminearum CF14047. The specific method is as follows.

[0094] The antibacterial spectrum of strain 7F2 was determined by plate standoff method. Strain 7F2 was streaked on both sides of the PDA plate 3 cm from the center and cultured at 25℃ for 3 days before the pathogen plate was inoculated in the center. A pathogen plate alone was used as a control.

[0095] Inhibition rate (%) = (control pathogen diameter - treated pathogen diameter) / control pathogen diameter × 100.

[0096] Note: F. graminearum PH-1 and F. pseudograminearum CF14047 were provided by the Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences. The same applies below. The results are shown in Table 1 and Figure 4 shown.

[0097] Table 1. Inhibitory effect of strain 7F2 on different pathogens (%)

[0098]

[0099] As shown in Table 1, strain 7F2 exhibited different degrees of inhibitory effect on Fusarium spp., with an inhibition rate of 83.57% against pseudofusarium graminearum CF14047 and 72.16% against Fusarium graminearum PH-1, and both produced inhibition zones in the confrontation experiment.

[0100] exist Figure 4In the 7F2 group, PH-1 and CF14047 were located in the center of the plate, and strain 7F2 was located on the left and right sides. The PH-1 and CF14047 colonies close to strain 7F2 were obviously inhibited.

[0101] The above results show that: the plate confrontation method was used to detect that strain 7F2 had a significant inhibitory effect on Fusarium graminearum PH-1 and Pseudofusarium graminearum CF14047.

[0102] (2) The fermentation broth of strain 7F2 was used to inhibit the growth of F. graminearum and F. graminearum. The specific method is as follows.

[0103] Strain 7F2 was cultured on Gao's medium No. 1 plates, and then five 5 mm bacterial plates were placed in 100 mL of Gao's liquid medium No. 1. After culturing at 25°C and 200 rpm for 7 days, the culture was filtered through three layers of sterile filter cloth and centrifuged at 5000 rpm for 8 minutes at 25°C. The supernatant was passed through a 0.22 μm bacterial filter to remove spores, and the resulting fermentation broth was stored at 4°C for later use.

[0104] The fermentation broth of the above strain 7F2 was mixed with cooled autoclaved PDA to obtain mixed culture media with a volume ratio of 25%, 50% and 75% (v / v), and then 15 mL of the mixed culture media was poured into a culture dish. After the culture medium was cooled and solidified, PH-1 and CF14047 bacterial plates were inoculated in the center of the plate, with 3 replicates for each concentration. At the same time, PDA culture medium without mixed fermentation broth was used as a blank control. After culturing for 5 days under dark conditions at 25°C, the colony diameter was measured in a cross-sectional manner and the inhibition rate was calculated. The results are shown in Table 2 and Figure 5 shown.

[0105] Table 2. Inhibitory effect of 7F2 fermentation broth on the growth of Fusarium spp. (%)

[0106]

[0107] The results showed that as the concentration of the fermentation broth of strain 7F2 increased, its inhibitory effect on pathogens also increased. At a concentration of 25%, the fermentation broth of strain 7F2 significantly inhibited the growth of CF14047 mycelium, and at a concentration of 50%, the inhibition rate exceeded 70%. The fermentation broth of strain 7F2 also significantly inhibited PH-1 at a concentration of 50%, and at a concentration of 75%, the inhibition rate exceeded 70%.

[0108] (3) The strain 7F2 inhibited the germination rate of Fusarium graminearum spores. The specific method is as follows.

[0109] Pseudomonas graminearum CF14047 was cultured on PDA medium at 25°C for 3 days, the mycelia were scraped into 100 mL of mung bean soup medium, and the culture was shaken at 25°C and 175 rpm for 3 days. The spores were filtered through two layers of sterile filter cloth and centrifuged (5000 rpm, 8 min). The supernatant was removed and diluted with sterile water. The spore concentration was calculated using a hemocytometer and adjusted to 5 × 10 6 pieces / mL.

[0110] 5 mL of the fermentation broth of strain 7F2 (obtained according to the method in (2) above) was mixed with 5 mL of the spore solution of F. graminearum CF14047 (5 × 10 6 Spores / mL) were mixed at a 1:1 (v / v) ratio and placed in a 50 mL sterile tube. Gao's liquid medium No. 1 was also used as a control. All tubes were shaken (180 rpm) at 25°C in the dark, and spore germination rates were measured 7 and 10 hours after incubation. Nc is the number of germinated spores in the control group, and Nt is the number of germinated spores in the treated group.

[0111] Conidia germination inhibition rate: I (%) = [(Nc-Nt) / Nc] × 100%.

[0112] The results are shown in Table 3.

[0113] Table 3. Inhibitory effect of strain 7F2 fermentation broth on CF14047 spore germination (%)

[0114]

[0115] The results show that compared with the control group, the fermentation broth of strain 7F2 significantly inhibited the germination of CF14047 spores. After 7 hours of treatment, the germination of spores was 100% inhibited. After 10 hours of treatment, the inhibition rate was as high as 93.79%, indicating that the fermentation broth of strain 7F2 has a good inhibitory effect on the germination of CF14047 spores.

[0116] (4) The inhibitory effect of the fermentation liquid of strain 7F2 on the stem base rot pathogen on wheat coleoptiles was determined as follows:

[0117] Soak Huaimai 33 seeds for 2 hours and rinse with sterile water three times. Place three sterile filter papers at the bottom of the culture dish and soak them. Each dish has 11 wheat seeds and is covered with soil. Place the dish in a 25°C incubator with 12 hours of light and 12 hours of darkness for cultivation. After the wheat coleoptile grows to 3 cm, cut a small wound at the top of the coleoptile and drop 2 μL of spore solution of Fusarium graminearum CF14047 (spore solution concentration is 5×10 6Spores / mL, spore solution was obtained by the method in (3) above). 2 μL sterile water was added to the blank control. On the second day, the coleoptile was wrapped with a sterile cotton ball. 150 μL of the fermentation liquid of strain 7F2 (the fermentation liquid was obtained by the method in (2) above) was added to the cotton ball. The control group was not wrapped with cotton balls. After 6 days of growth, the height and fresh weight of the wheat seedlings were measured, and the length of the lesions was measured. The results are shown in Table 4 and Figure 6 shown.

[0118] Table 4. Effect of strain 7F2 fermentation broth on the growth of stem base rot pathogens on coleoptiles (cm)

[0119]

[0120] The results show that compared with the control group (CK), the length of wheat lesions (0.07 cm) after treatment with the fermentation liquid of strain 7F2 was significantly lower than that of CK (0.75 cm), and the difference between the two was significant, indicating that the fermentation liquid of strain 7F2 significantly reduced the infection of F. graminearum CF14047 on wheat plants.

[0121] Example 3

[0122] This example is a potted plant protection test of the fermentation broth of strain 7F2 against Fusarium graminearum CF14047.

[0123] The specific contents of this embodiment are as follows:

[0124] (1) Preparation of diseased rice grains

[0125] The pseudo-Fusarium graminearum CF14047 was activated on PDA medium, and a bacterial cake was taken from the edge of the colony. The bacterial cake was inoculated into mung bean soup and cultured at 25°C and 175 rpm for 3 days. The mycelium was filtered through three layers of sterile filter cloth, and the conidia concentration was adjusted to 5×10 5 Conidia / mL: Inoculate 10 mL of spore solution per 50 g of millet and incubate in the dark at 25°C for 5-7 days to obtain diseased rice kernels. Sterilize seedling culture medium (purchased from Jiangsu Xingnong Matrix Technology Co., Ltd.) in a 121°C oven for 6 hours to obtain a sterile medium. Mix the diseased rice kernels with the sterile medium at a 0.5% mass ratio to obtain a contaminated medium, which is then set aside.

[0126] (2) Inhibitory effect of the fermentation liquid of strain 7F2 on wheat stem rot

[0127] Huaimai 33 seeds were placed in a culture dish lined with moist filter paper, and germinated at 26°C and 12h / 12h alternating light and dark conditions until the seeds turned white. The white seeds were sown in the matrix, one of which was sown in a sterile matrix and subsequently irrigated with Gao's No. 1 liquid culture medium as a negative control, and the other treatments were sown in a fungal matrix and subsequently divided into 7F2 treatment group, blank control group, and drug control group; 16 seeds were sown in each pot, and 3 pots were per treatment; cultured at 26°C, 12h light, and 12h dark conditions. When the wheat grew to about 3cm, the 7F2 treatment group was irrigated with 20mL / pot of strain 7F2 fermentation liquid (the fermentation liquid was obtained according to the method in (2) of Example 2); the blank control group was irrigated with Gao's No. 1 liquid culture medium; the drug control group was irrigated with a thiophanate-methyl suspension (Zhengzhou Leading Chemical Co., Ltd.). After 30 days of growth, the occurrence of wheat stem base rot and the growth of wheat were investigated. The results are shown in Table 5. Figure 7 and Figure 8 shown.

[0128] Table 5. Effect of strain 7F2 fermentation broth on wheat growth (cm)

[0129]

[0130] The results showed that compared to the untreated control (CK), the incidence of wheat stem rot was reduced to varying degrees after treatment with fludioxonil and 7F2. The length of root lesions in wheat treated with fludioxonil and 7F2 was lower than that in the CK, and the disease incidence in wheat treated with fludioxonil was lower than that in the 7F2 treatment. Furthermore, the fresh weight and plant height of wheat treated with fludioxonil and 7F2 were higher than those in the CK, indicating that strain 7F2 had no effect on wheat growth.

[0131] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A biocontrol strain, which is Streptomyces rochei 7F2, deposited in China General Microbiological Culture Collection Center with a deposit number of CGMCC NO.32196.

2. The fermentation liquid of the biocontrol strain according to claim 1.

3. A method for preparing a biocontrol strain fermentation liquid, characterized in that: The following steps are involved: The first step is to culture the biocontrol strain according to claim 1 on a Gao's No. 1 medium plate, and then take a bacterial plate; put the bacterial plate into Gao's No. 1 liquid medium, and culture it at 25°C ± 1°C with shaking to obtain a fermentation mixture. The second step is to filter the fermentation mixture, centrifuge the obtained liquid to obtain the supernatant, and pass the supernatant through a bacterial filter to remove spores, thereby obtaining the biocontrol strain fermentation liquid.

4. The method for preparing a biocontrol strain fermentation broth according to claim 3, characterized in that, in the first step, the diameter of the bacterial plate is 5±1 mm, the number of bacterial plates: the volume of Gao's No. 1 liquid culture medium = 5: 100±10 mL; the culture conditions are: the rotation speed is 200-250 r / min, and the time is at least 7 days.

5. The method for preparing a biocontrol strain fermentation liquid according to claim 3 is characterized in that, in the first step, the Gao's No. 1 medium is composed of the following components: soluble starch 20g, NaCl 0.5g, KNO 3.1g, K2HPO4·3H2O0.5g, MgSO4·7H2O 0.5g, FeSO4·7H2O 0.01g, agar 20g, ddH2O 1L, and the pH is adjusted to 7.4-7.

6.

6. The method for preparing a biocontrol strain fermentation liquid according to claim 3, characterized in that: In the second step, at least three layers of sterile filter cloth are used for filtration; the centrifugation conditions are: at 25°C±1°C, 5000-6000 rpm for at least 8 minutes; the pore size of the bacterial filter is less than or equal to 0.22 μm.

7. Use of the biocontrol strain according to claim 1 or the fermentation liquid according to claim 2 for preparing a biocontrol agent for inhibiting Pseudomonas graminearum and Fusarium graminearum.

8. Use of the biocontrol strain according to claim 1 or the fermentation liquid according to claim 2 for preparing a biocontrol agent for preventing and controlling wheat stem base rot or wheat fusarium head blight.

9. A biocontrol agent comprising the biocontrol strain according to claim 1 or the fermentation liquid according to claim 2.

10. Use of the biocontrol agent according to claim 9 for preventing and controlling wheat stem base rot or wheat fusarium head blight.

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