Bacillus velezensis Fjnp2 and application thereof

Abstract

The invention discloses bacillus velezensis Fjnp2 and application thereof, and belongs to the technical field of biological control. The strain is preserved in the China General Microbiological Culture Collection Center (CGMCC), the preservation number is CGMCC No.34418, the preservation date is May 6, 2025, and the strain is named as Bacillus velezensis in taxonomy. The bacillus velezensis Fjnp2 has broad-spectrum bacteriostatic activity and a remarkable control effect, has a good inhibition effect on four pathogenic fungi of the corn leaf spot disease, has an alternaria alternata bacteriostasis rate of 84.45%, breaks through the bottleneck of shortage of corn alternaria alternata leaf spot disease biocontrol strain resources, has high efficiency and environmental safety, and has a wide application prospect. The strain is a potential biocontrol strain for preventing and treating the disease, provides a high-quality strain resource for developing novel biological control products, promotes the development of an agricultural green control technology, and has an application value of being developed into a biological control preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of biological control, and more particularly to a strain of Bacillus velezensis Fjnp2 and application thereof. Background Art

[0002] Corn Alternaria leaf spot is an important plant disease caused by the fungus Alternaria alternata. Currently, relevant research reports on corn Alternaria leaf spot have been reported in Heilongjiang, Yunnan, Fujian, and Hainan provinces in my country. Corn Alternaria leaf spot mainly harms leaves, and in the later stages of the disease, it can also harm bracts and leaf sheaths. Early symptoms: Small, water-soaked, round spots appear on the diseased area. Mid-term symptoms: The spots gradually expand into oval or nearly circular lesions, and the expansion of the lesions is not restricted by leaf veins. The center of the lesion is grayish white to withered white, with purple or reddish brown edges, and is clearly demarcated from healthy tissue. Late symptoms: A black mold layer appears inside the lesion. In severe cases, the middle of the lesion will rupture and perforate, and multiple lesions will fuse together and spread throughout the leaf, causing large areas of the leaf to dry out, tear, or necrotize.

[0003] Because the pathogens of maize Alternaria leaf spot vary in their pathogenicity across different regions and environmental conditions, current chemical pesticide control methods, while effective in controlling crop diseases, also pose increasing environmental impacts and resistance issues. The use of chemical pesticides can also lead to pathogens developing resistance. Once established, this resistance poses greater challenges to future disease management, increasing control costs and potentially reducing treatment effectiveness. Therefore, to reduce the use of chemical pesticides, the development and application of safe, effective, and environmentally friendly biological control methods is a key direction for future agricultural production.

[0004] Faced with the environmental pressures and resistance challenges posed by chemical pest control, biological control technology, due to its environmentally friendly nature, has become a key development direction in disease prevention and control. Although studies have confirmed the significant control effects of biocontrol strains such as Monosporus, Streptomyces, and Bacillus against other plants, the availability of biocontrol strains specifically for controlling Alternaria leaf spot in maize remains relatively scarce, limiting the practical application of this technology.

[0005] Therefore, how to carry out biological control of corn Alternaria leaf spot is a problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a strain of Bacillus velezensis Fjnp2 and its application to address the deficiencies in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A strain of Bacillus velezensis Fjnp2 is characterized in that the strain is deposited in the China General Microbiological Culture Collection Center with a deposit number of CGMCC No. 34418 and a deposit date of May 6, 2025, and is taxonomically named Bacillus velezensis.

[0009] Strain Fjnp2 was inoculated on NA medium and cultured at 28°C for two days. The colonies were flat, milky white, opaque, with a dry surface and irregular edges. Microscopic examination revealed elliptical cylindrical cells and Gram-positive staining. Biochemical testing revealed a negative reaction to methyl red and a positive VP test. Its carbon source metabolic profile revealed efficient utilization of three carbohydrates: lactose, maltose, and glucose. It also possessed enzyme activities in nitrate reduction, starch hydrolysis, and gelatin liquefaction. Based on the classification criteria of the Bergey's Manual of Identification of Bacteria and the Manual of Systematic Identification of Common Bacteria, and considering its morphological, physiological, and biochemical characteristics, this strain was tentatively assigned to the genus Bacillus.

[0010] Genomic DNA from strain Fjnp2 was extracted, and the 16S rDNA gene was amplified using 16S rDNA primers. Electrophoresis revealed that all bands were over 1000 bp in length. Sequencing yielded a 1445-bp fragment. BLAST analysis was performed on the 16S rDNA gene sequence of strain Fjnp2, and phylogenetic trees were constructed using the Newton-Joint Joint (NJ) method based on the alignment results. The results showed that strain Fjnp2 clustered with four strains of Bacillus velezensis in the 16S rDNA-based phylogenetic tree. Combined with morphological, physiological, and biochemical characteristics, strain Fjnp2 was ultimately identified as Bacillus velezensis.

[0011] Strain Fjnp2 showed varying degrees of inhibition against four common corn leaf spot pathogens, with the most pronounced inhibition against Alternaria alternata, with an inhibition band of 19.25 mm. It also showed good inhibition against the other three pathogens, with inhibition bands ranging from 3.25 mm to 17.30 mm. This indicates that strain Fjnp2 exhibits excellent inhibitory activity against a variety of common corn leaf spot pathogens.

[0012] The strain Fjnp2 has a good inhibitory effect on Alternaria leaf spot caused by Alternaria alternata.

[0013] The present invention also seeks to protect a use of the above-mentioned Bacillus Velezii Fjnp2 in preparing a biological agent for preventing and treating corn Alternaria leaf spot disease.

[0014] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] The Bacillus Velezii Fjnp2 of the present invention has broad-spectrum antibacterial activity and significant prevention effect, has a good inhibitory effect on four pathogenic fungi of corn leaf spot disease, and has an inhibition rate of 84.45% on Alternaria alternata. It breaks through the bottleneck of the shortage of biocontrol strain resources for corn Alternaria alternata leaf spot disease, has both high efficiency and environmental safety, is a potential biocontrol strain for preventing and controlling the disease, provides high-quality strain resources for the development of new biological control products, promotes the development of agricultural green control technology, and has application value in being developed into a biological control preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The antibacterial effect of strain Fjnp2 on the target pathogen Alternaria alternata (7 days), where A: pure culture Alternaria alternata (CK), B: strain Fjnp2 against Alternaria alternata;

[0017] Figure 2 The morphological characteristics (A) and Gram staining (B) of strain Fjnp2;

[0018] Figure 3 This is the phylogenetic tree of strain Fjnp2 constructed based on the neighbor-joining method of 16S rDNA gene sequences;

[0019] Figure 4 The antibacterial effect of strain Fjnp2 on E. nigricans (A), Helminthosporium maydis (B), Alternaria alternata (C) and Helminthosporium macrosporum (D) (7d). DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] Example 1

[0022] Screening and identification of a highly effective biocontrol strain against Alternaria alternata leaf spot in fresh corn

[0023] In response to the spread of corn Alternaria leaf spot caused by Alternaria alternata and the environmental pressure and resistance problems brought about by chemical pesticide control, this study used the plate dilution method to isolate biocontrol strains from the rhizosphere soil of corn-growing areas in Fujian, screened the biocontrol strains by the plate confrontation method, combined morphological, physiological and biochemical tests and 16S rDNA gene sequence analysis for strain identification, and determined the strain's antibacterial spectrum and potted control effect, aiming to screen efficient and environmentally friendly biocontrol strains to promote green disease control; the study isolated 63 single colonies from the soil, screened out 3 strains with antibacterial activity, among which strain Fjnp2 had the best antibacterial effect, with an inhibition bandwidth of 19.25 mm, and was identified as Bacillus velezensis. velezensis, which has a good inhibitory effect on four pathogenic fungi of corn leaf spot disease, and the inhibition rate against Alternaria alternata is 84.45%; pot experiments showed that its fermentation liquid had a 7-day control effect of 79.79% and a 14-day control effect of 60.75% on the variety "Mintiannuo 707", which is significantly better than the conventional chemical agent pyraclostrobin; the research results show that Bacillus velezensis Fjnp2 has broad-spectrum antibacterial activity and significant control effect, breaking through the bottleneck of the lack of biocontrol strain resources for corn Alternaria alternata leaf spot, and has both high efficiency and environmental safety. It is a potential biocontrol strain for the prevention and control of this disease, providing high-quality strain resources for the development of new biological control products, promoting the development of agricultural green control technology, and has application value in being developed into a biological control agent.

[0024] This study focused on corn cultivation bases in Youyang Town, Xianyou County, Putian City, Fujian Province, and Yanghou Town, Yanping District, Nanping City, Fujian Province. Using Alternaria as the target pathogen, the study sought to identify strains with inhibitory effects on the pathogen from rhizosphere soil. Potted plant experiments were conducted to verify the efficacy of fermentation broths of the isolated strains against Alternaria leaf spot disease in maize, providing an important strain resource and practical basis for the development of new biocontrol agents.

[0025] 1 Materials and Methods

[0026] 1.1 Test materials

[0027] 1.1.1 Source of Test Soil Samples Soil samples were collected from a corn planting base in Youyang Town, Xianyou County, Putian City, Fujian Province (latitude: 25°37'26.4", longitude: 118°49'8.4") and Yanghou Town, Yanping District, Nanping City, Fujian Province (latitude: 26°37'51.272", longitude: 118°31'1.960"). During sampling, the topsoil around the corn rhizosphere was removed, and healthy corn rhizosphere soil samples were collected 5-10 cm below the soil surface.

[0028] 1.1.2 Test Pathogens and Plants The maize pathogens used were Epicoccum nigrum, the pathogen causing corn leaf spot; Bipolaris maydis, the pathogen causing corn leaf spot; Alternaria alternata, the pathogen causing corn leaf spot; and Exserohilum turcicum, the pathogen causing corn leaf spot. The maize variety used for the tests was "Mintiannuo 707" (National Approved No. 20210652). All materials were provided by the Institute of Plant Protection, Fujian Academy of Agricultural Sciences.

[0029] 1.1.3 Reagents and instruments 30% pyraclostrobin (Henan Yongguan Qiaodi Agricultural Technology Co., Ltd.) is a commonly used agent for the prevention and control of corn Alternaria leaf spot in production; bacterial genomic DNA extraction kit (Tiangen Biochemical Technology Beijing Co., Ltd.); D2000 DNA Marker molecular weight standard (Lanjieke Technology Co., Ltd.); Gram staining solution kit (Qingdao High-tech Industrial Park Haibo Biotechnology Co., Ltd.); T100 PCR instrument (Bio-Rad Life Sciences Products Co., Ltd.); SPX-250BSH-Ⅱ biochemical incubator (Shanghai Xinmiao Medical Equipment Manufacturing Co., Ltd.); E200MV biological microscope (Nanjing Nikon Jiangnan Optical Instrument Co., Ltd.); KDC-140HR high-speed refrigerated centrifuge (Anhui Zhongke Zhongjia Scientific Instrument Co., Ltd.); small-capacity QYC-2102C fully constant temperature double-layer incubation shaker (Shanghai Xinmiao Medical Equipment Manufacturing Co., Ltd.).

[0030] 1.2 Test methods

[0031] 1.2.1 Isolation and screening of biocontrol strains The maize rhizosphere microorganisms were isolated by dilution and spreading method. 1 g of air-dried healthy maize rhizosphere soil sample was added to a 10 mL test tube containing 9 mL of sterile water. The tube was placed in a shaker at 28°C and 180 rpm for 30 min to obtain a soil suspension. After standing for 10 min, the suspension was diluted 10-fold to 10-fold. -2 , 10 -3 and 10 -4100 μL of each serial dilution was spread onto nutrient agar (NA) plates, which were then incubated at 28°C for 6 days. Individual colonies with distinct morphology and color were selected and transferred to NA plates for purification. The purified strains were stored in a refrigerator at 4°C until further use. The purified strains were tested for their antagonistic effects against plant pathogens using the plate standoff method. Initial screening: Isolated biocontrol strains were inoculated at four locations 25 mm from the center of the plate. After incubation at 28°C for 7 days, strains with an inhibition band greater than 5 mm were selected for rescreening. Rescreening: Strains that showed efficacy in the initial screening were rescreened. A pathogen cake (5 mm in diameter) was inoculated in the center of a PDA plate. Effective strains were placed approximately 2.5 cm above, below, and to the left and right of the center. A plate inoculated with only the pathogen cake served as a control. The plates were incubated at 28°C for 7 days. The inhibition bandwidth of the treatment group was measured and its inhibition rate was calculated according to the formula. Each treatment was repeated 3 times to screen out the biocontrol strains with excellent antibacterial effect on pathogens.

[0032] 1.2.2 Identification of Biocontrol Strains Observation of colony characteristics and Gram staining of biocontrol strains: Inoculate biocontrol bacteria onto NA medium and incubate in a 37°C incubator for 2 days. Observe colony morphology, odor, and changes in culture medium color. Observe size and morphology under a microscope. Gram staining is also performed to determine whether the strain is Gram-positive or Gram-negative. Determination of the physiological and biochemical characteristics of biocontrol strains: Referencing the Bergey's Manual of Bacterial Identification and the Manual for Systematic Identification of Common Bacteria, conduct tests to assess the physiological and biochemical characteristics of biocontrol strains using sugar (alcohol) fermentation, gelatin liquefaction, nitrate reduction, starch hydrolysis, VP, methyl red, and H2S production assays. Molecular Identification of the Biocontrol Strain: The extracted DNA solution was used to amplify the bacterial genome using primers specific for the 16S rDNA gene. The universal 16S rDNA primers used were 27F (5′-AGAGTTTGATCCTGGCTCAG-3′) and 1492R (5′-TACGGCTACCTTGTTACGACTT-3′). The PCR amplification reaction system consisted of 1 μL of each upstream and downstream primer, 12 μL of 2× Taq premix, 2 μL of DNA template, and 9 μL of ddH2O. PCR amplification conditions were: 94°C denaturation for 3 min, followed by 35 cycles of denaturation at 94°C for 45 s, annealing at 55°C for 90 s, and extension at 72°C for 2 min, with a final extension at 72°C for 5 min. After PCR amplification, products were analyzed by 1% agarose gel electrophoresis. Sequencing of the PCR products was commissioned to Sangon Biotech (Shanghai) Co., Ltd. The resulting sequencing data were assembled using DNAman 9.0 software. After BLAST homology analysis, the sequences were uploaded to the GenBank database on the NCBI platform. 16S rDNA gene sequences of congener strains were also obtained from this database. A phylogenetic tree was then constructed using the neighbor-joining analysis method (NJ) in MEGA 12.0.

[0033] 1.2.3 The antibacterial spectrum of biocontrol strains was based on the antibacterial effects of four maize leaf spot pathogens, including Ephemerococcus nigricans, Ephemerococcus spp., Alternaria alternata, and Alternaria spp., respectively. Each treatment was repeated three times. All plates were placed in an incubator at 28°C for 7 days. The inhibition bandwidth of the test group was measured and recorded, and an inhibition bandwidth greater than 5 mm was defined as the inhibition index.

[0034] 1.2.4 Potted Control Efficacy of Biocontrol Strains The control efficacy of Alternaria alternata, a common leaf spot pathogen in corn, was determined using healthy corn plants with uniform growth of approximately 20 cm. Three treatment groups were set up in each experiment, with three pots in each treatment and three seeds in each pot. High-temperature sterilized peat soil was used as the culture medium. 50 mL of Alternaria alternata spore suspension (1×10 7 CFU / mL, culture conditions see 1.2.1), and one day later, the corresponding reagents were sprayed on the corn leaves, 20 mL of sterile water (CK), Bacillus Velez Fjnp2 fermentation liquid (1×10 7 CFU / mL, culture conditions are the same as 1.2.1) (treatment 1) and 1000 times 30% pyraclostrobin (treatment 2). Routine management was carried out during the experiment. The disease index was calculated on the 7th and 14th days after inoculation, and the prevention effect was calculated. The disease grading standard refers to the "Technical Specifications for Identification of Disease and Insect Resistance of Corn" in the agricultural industry standards of the People's Republic of China. Level 0: Immunity, no disease; Level 1: There are sporadic lesions on the leaves, and the lesion area is ≤5%; Level 3: There are a small number of lesions on the leaves under the ear, accounting for 6% to 10% of the leaf area, and there are sporadic lesions on the leaves on the ear; Level 5: There are more lesions on the leaves under the ear, accounting for 11% to 30% of the leaf area, and there are a small number of lesions on the leaves on the ear; Level 7: There are a large number of lesions on the leaves under the ear and on the ears, accounting for 31% to 70% of the leaf area; Level 9: All leaves are basically covered with lesions, and the leaves are dead.

[0035] 1.3 Data and Analysis

[0036] Experimental data were entered into Excel 2019 and analyzed using IBM SPSS Statistics 27 for univariate analysis. Duncan's method was used to analyze the inhibitory bandwidth and potted efficacy of the biocontrol strain Fjnp2 against different maize leaf spot pathogens. Inhibition rate = (control colony diameter - treated colony diameter) / control colony diameter × 100%. Disease index was calculated based on disease level: disease index = Σ (number of diseased plants at each level × number of disease levels) / (total number of plants surveyed × highest disease index) × 100. Control efficacy (%) = (control disease index - treated disease index) / control disease index × 100.

[0037] 2 Results and Analysis

[0038] 2.1 Isolation and screening of biocontrol strains

[0039] According to experimental method 1.2.1, 63 single colonies were isolated and 3 strains with an inhibition band greater than 5 mm were obtained in the initial screening for rescreening. After the initial screening strains were cultured against the target pathogen Alternaria alternata for 5 days, it was found that strain Fjnp2 had the largest inhibition band, reaching 19.25 mm ( Figure 1 ), and finally the strain was selected for further classification and identification.

[0040] 2.2 Identification of biocontrol strains

[0041] The strain Fjnp2 was inoculated on NA medium at 28℃ for 2 days. The colonies were flat, milky white, opaque, dry, and with irregular edges. Figure 2 Middle A). Staining microscopy results ( Figure 2 B), the bacteria are oval-cylindrical and show positive Gram staining characteristics. Biochemical testing revealed that this strain was negative for methyl red and positive for the VP test. Its carbon source metabolic profile revealed efficient utilization of three carbohydrates: lactose, maltose, and glucose. It also possesses enzyme activities such as nitrate reduction, starch hydrolysis, and gelatin liquefaction. Based on the classification criteria of the Bergey's Manual of Identification of Bacteria and the Manual of Systematic Identification of Common Bacteria, and considering its morphological, physiological, and biochemical characteristics, this strain is tentatively classified as a Bacillus.

[0042] Table 1 Physiological and biochemical characteristics of strain Fjnp2

[0043]

[0044]

[0045] Note: “+” indicates a positive result; “-” indicates a negative result.

[0046]

[0047] The 16S rDNA gene sequence of Fjnp2 strain was subjected to BLAST analysis, and the phylogenetic trees were constructed using the NJ method according to the 16S rDNA gene sequence alignment results ( Figure 3 The results showed that strain Fjnp2 clustered with four strains of Bacillus velezensis in the phylogenetic tree based on 16S rDNA. Combined with morphological and physiological and biochemical characteristics, strain Fjnp2 was ultimately identified as Bacillus velezensis and deposited in the China General Microbiological Culture Collection with the deposit number CGMCC No. 34418 and the deposit date of May 6, 2025.

[0048] 2.3 Antibacterial spectrum of biocontrol strains

[0049] The results of the antibacterial spectrum determination of strain Fjnp2 are as follows Figure 4 As shown in the table, strain Fjnp2 exhibited varying degrees of inhibitory activity against four common corn leaf spot pathogens, with the most pronounced inhibitory effect against Alternaria alternata, with an inhibition band of 19.25 mm. It also exhibited significant inhibitory activity against the other three pathogens, with inhibition bands ranging from 3.25 mm to 17.30 mm (Table 2). This indicates that strain Fjnp2 exhibited significant inhibitory activity against a variety of common corn leaf spot pathogens.

[0050] Table 2 Inhibitory bandwidth and inhibition rate (7 days) of strain Fjnp2 against four corn leaf spot pathogens

[0051]

[0052] 2.4 Efficacy of biocontrol strains against Alternaria leaf spot disease in maize

[0053] The results of a potted experiment on the efficacy of strain Fjnp2 against Alternaria leaf spot disease of corn showed that the leaves of corn in the control group had more chlorotic spots, a severe disease severity, and a large number of wilted leaves; the corn plants treated with pyraclostrobin had a lower disease severity; and the corn plants inoculated with the fermentation liquid of the biocontrol strain Fjnp2 had thick stems, good leaf growth, and significantly fewer leaf spots and wilted leaves than those in the control group and the pesticide-treated group.

[0054] As can be seen from Table 3, on the 7th day of inoculation, the fermentation filtrate of strain Fjnp2 had a control effect of 79.79% on the Alternaria leaf spot disease of corn "Mintiannuo 707", while the control effect of 1000 times 30% pyraclostrobin was only 59.43%; on the 14th day of inoculation, the fermentation filtrate of strain Fjnp2 had a control effect of 60.75% on the Alternaria leaf spot disease of corn "Mintiannuo 707", while the control effect of 1000 times 30% pyraclostrobin was only 50.05%; the results showed that the antagonistic bacteria had a good inhibitory effect on the Alternaria leaf spot disease caused by Alternaria.

[0055] Table 3. Control effect of Fjnp2 on Alternaria leaf spot of maize “Mintiannuo 707” in potted plants

[0056]

[0057]

[0058] Note: - indicates empty.

[0059] 3 Discussions

[0060] In the field of plant disease biological control research, Bacillus, as an important member, has a mechanism of action in controlling plant fungal diseases that mainly covers three aspects: competition for nutrients and space, secretion of antimicrobial substances, and induction of systemic resistance in plants. From the perspective of competition mechanism, Bacillus significantly inhibits the reproductive capacity of pathogens by competing with them for essential nutrients and occupying ecological niches. For example, Bacillus velezensis can synthesize siderophores, which, by chelating iron ions in the environment, restrict the pathogens' access to iron while providing nutrition to the plant, thereby establishing a competitive advantage. In terms of antimicrobial substance secretion, this type of biocontrol fungus can produce metabolites with broad-spectrum antimicrobial activity, including lipopeptides (such as surfactant) that destroy the cell wall / cell membrane structure of pathogens, peptide antibiotics, and hydrolases such as cellulase and protease that directly degrade the mycelial wall, inhibiting the growth and development of pathogens through multi-target effects. Furthermore, some Bacillus strains can activate salicylic acid (SA) or jasmonic acid (JA) signaling pathways in plants by secreting signaling molecules such as systemin, inducing the production of defense substances such as pathogenesis-related proteins (PR proteins) and phytoalexins, thereby forming systemic resistance and enhancing the plant's overall disease resistance. These mechanisms constitute a highly effective and sustainable biocontrol strategy for Bacillus species, providing an important theoretical basis for the green prevention and control of fungal diseases. In this study, the antagonistic strain Fjnp2 was isolated and screened from soil in a corn production base. This strain exhibited significant antagonism against Alternaria alternata, the pathogen of corn leaf spot disease, with an inhibition band of 19.25 mm. Through observation of its morphological, physiological, and biochemical characteristics, combined with 16s rDNA phylogenetic analysis, strain Fjnp2 was ultimately identified as Bacillus velezensis.

[0061] Pot experiments serve as a key verification link between indoor antibacterial activity screening and practical field application, and are an important means of evaluating the actual control efficacy of antagonistic bacteria. Wang Bingce confirmed through pot experiments that a 60% sterile fermentation broth of Bacillus velez WL-23 had a 62.27% control effect on kiwifruit leaf canker, and its bacterial suspension treatment had a control effect of up to 77.29%, significantly better than the chemical treatment group, and had a growth-promoting effect on kiwifruit seedlings (Wang Bingce. Screening of biocontrol bacteria for kiwifruit canker and evaluation of their biocontrol potential [D]. Guiyang: Guizhou University, 2024.); Yan Lixia found that a suspension of Bacillus velez ZF513 (concentration 1×10 8 CFU / mL) against cucumber damping-off disease, achieving an 86.64% efficacy, significantly higher than chemical agents (58.19%) (Yan Lixia. Screening and application of antagonistic Bacillus against cucumber damping-off disease [D]. Beijing: Chinese Academy of Agricultural Sciences, 2024.); Cao Hui et al. demonstrated through potted plant experiments that treatment with a suspension of Bacillus Velezii reduced the incidence of mango anthracnose by 42.3% and achieved a 65.5% efficacy (Cao Hui, Yang Weiyan, Na Qiting, et al. Inhibitory effect of Bacillus Velezii on mango anthracnose and fruit preservation effect [J / OL]. Acta Botanica Sinica, 1-10 [2025-06-09].

[0062] http: / / kns.cnki.net / kcms / detail / 11.5705.Q.20250224.1419.006.html.); Cheng Zhiyong et al. demonstrated in potted plant experiments that Bacillus velezensis ZS5-1 achieved a 63.20% control rate against peanut white rot (Cheng Zhiyong, Song Wanduo, Yu Dongyang, et al. Screening and efficacy of highly pathogenic biocontrol bacteria against peanut white rot [J / OL]. Chinese Journal of Oil Crops, 1-9 [2025-06-09]. https: / / doi.org / 10.19802 / j.issn.1007-9084.2025012.). These studies, through potted plant experiments, validated the effectiveness of Bacillus velezensis in controlling various crop diseases, providing a key practical basis for its field application. The results of the potted experiment in this study showed that 14 days after inoculation, the fermentation liquid of strain Fjnp2 had a control effect of 60.75% on Alternaria leaf spot of corn variety 'Mintiannuo 707', which was higher than the control effect after treatment with 1000 times 30% pyraclostrobin. It can be seen that the fermentation liquid of strain Fjnp2 has a better control effect on Alternaria leaf spot of corn, indicating that the biocontrol strain Bacillus velezensis Fjnp2 has an inhibitory effect on Alternaria leaf spot of corn, indicating that strain Fjnp2 has certain biocontrol potential in practical applications.

[0063] In practical applications, the biocontrol effectiveness of Bacillus spp. is influenced by numerous factors, including environmental conditions, strain characteristics, and the type of target pathogen. Environmental factors such as temperature, humidity, and soil pH significantly impact Bacillus spp.'s colonization ability and the secretion of antimicrobial substances. Therefore, the next step should focus on optimizing Bacillus spp. culture conditions to enhance their stability and persistence in field environments, thereby providing a more solid foundation for the widespread application of Bacillus spp. in plant disease biocontrol.

[0064] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A strain of Bacillus velezensis Fjnp2, characterized in that: The strain was deposited in the China General Microbiological Culture Collection Center with the deposit number CGMCC No.34418 and the deposit date May 6, 2025. The taxonomic name is Bacillus velezensis.

2. A use of the Bacillus Velezii Fjnp2 according to claim 1 in the preparation of a biological agent for preventing and treating corn Alternaria leaf spot.

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