Application of honokiol in preparation of bactericide for preventing and treating plant fungal diseases

Abstract

The invention belongs to the technical field of agricultural biology, and particularly discloses application of honokiol in preparation of a bactericide for preventing and treating fungal diseases of plants, and honokiol is derived from plants, is a green, environment-friendly and high-safety small molecule compound, is wide in antibacterial spectrum and long in lasting period, and can be applied to prevention and treatment of fungal diseases of plants. The bactericidal composition can be used for effectively preventing and treating plant diseases of peanuts, corns, wheat, Chinese chives, soybeans, peppers, tomatoes and the like, can be applied to industrial crops such as various grains, melons and fruits, vegetables and the like, is safe to non-target organisms, meets the requirements of green sustainable development, and has a wide application value.

Description

Technical Field

[0001] This invention belongs to the field of agricultural biotechnology, and specifically discloses the application of magnolol in the preparation of fungicides for the prevention and control of plant fungal diseases. Background Technology

[0002] Plant diseases not only reduce crop yield and quality, but toxins also accumulate in food, endangering human and animal health. Diseases caused by plant pathogenic fungi account for over 70% of all plant diseases. These fungal diseases are widespread and cause serious damage in agricultural production, such as: 1. Peanut white mold, caused by *Sclerotium sclerotiorum* (… Sclerotium rolfsii 1. Diseases caused by infection with Rhizoctonia solani typically result in a 20% yield reduction in peanuts, with severe cases causing losses of up to 80% or even total crop failure; 2. Corn sheath blight is caused by Rhizoctonia solani. Rhizoctonia solani Caused by, characterized by a wide host range and high damage; 3. Wheat stem rot is a major disease that has seriously damaged wheat in the Huang-Huai region in recent years, mainly caused by Fusarium pseudograminearum (… Fusarium pseudograminearum Caused by Botrytis cinerea, resulting in losses exceeding 50% in severe cases, and even total crop failure; 4. Gray mold in chives is mainly caused by Botrytis cinerea (… Botrytis squamosa ) and Botrytis cinerea ( Botrytis cinerea 5. Soybean root rot is mainly caused by Fusarium spp. (…). Infected plants develop white or grayish-white spots on their leaves, affecting quality and economic value. Fusarium ) and Phytophthora ( Phytophthora Soil-borne diseases caused by anthracnose, with an incidence rate as high as 60-70%, can lead to large-scale yield reductions; 6. Anthracnose of peppers is caused by anthracnose fungus (… Colletotrichum This disease is caused by a fungus, primarily infecting leaves and fruits, causing seedling death in peppers, and reducing fruit quality and economic benefits; 7. Tomato black spot is caused by Alternaria alternata (… Alternaria alternate This disease, which primarily damages tomato fruits, can also cause plant wilting and chlorosis, severely impacting the tomato industry.

[0003] Currently, chemical agents are still the common means of controlling plant fungal diseases. However, long-term continuous use of a single chemical agent can not only lead to resistance in plant pathogens, but also cause pesticide residues, resulting in a series of problems such as environmental pollution and harm to human health. With the increasing emphasis on environmental protection, food safety and health in society, green and environmentally friendly plant-derived pesticides have gradually attracted people's attention.

[0004] Honokiol is a lignan compound derived from the bark, root bark, and branch bark of *Magnolia officinalis* or *Magnolia davidii*, deciduous trees belonging to the Magnoliaceae family. Its chemical name is 3',5-diallyl-[1,1'-biphenyl]-2,4'-diol, and its molecular formula is C2. 18 H 18 O2, CAS No.: 35354-94-6, structural formula:

[0005] This compound is a yellowish-brown to pale yellow or white powder with a fragrant odor and a pungent, slightly bitter taste. It is soluble in organic solvents such as methanol, ethanol, acetone, ethyl acetate, and chloroform. Clinically, it is mainly used to relieve chest and abdominal fullness, calm the central nervous system, relax muscles in athletes, and for antifungal, anti-ulcer, and psychotropic treatment. There are also reports that magnolol can be used as an agricultural fungicide, inhibiting the growth of mycelia of pathogens such as rice sheath blight, tobacco black shank, downy mildew, Solomon's seal root rot, wheat scab and wilt, cotton verticillium wilt, and rice blast fungus. However, there are currently no reports, either domestically or internationally, of magnolol inhibiting the growth of mycelia of pathogens such as peanut white mold, corn sheath blight, wheat stem base rot, leek gray mold, soybean root rot, pepper anthracnose, and tomato black spot. Summary of the Invention

[0006] To address the problems in the background art, this invention discloses the application of magnolol in the preparation of fungicides for the prevention and control of plant fungal diseases. It has broad-spectrum antibacterial activity, long-lasting effect, is environmentally friendly, and has high safety, and can be applied to various grains, fruits, vegetables and other economic crops.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: Application of magnolol in the preparation of fungicides for the prevention and control of plant fungal diseases.

[0008] Furthermore, plant fungal diseases include peanut white mold, corn sheath blight, wheat stem base rot, leek gray mold, soybean root rot, pepper anthracnose, or tomato black spot.

[0009] Furthermore, the fungus is *Sclerotium guillezine*, the pathogen of peanut white mold; *Rhizoctonia solani*, the pathogen of corn sheath blight; *Fusarium graminearum*, the pathogen of wheat stem base rot; *Botrytis cinerea*, the pathogen of leek gray mold; *Fusarium graminearum*, the pathogen of soybean root rot; *Anthracnose*, the pathogen of pepper anthracnose; or *Alternaria alternata*, the pathogen of tomato black spot.

[0010] Furthermore, the inhibition rate of magnolol on the mycelial growth of plant pathogenic fungi is dose-dependent.

[0011] Furthermore, the concentration of the active ingredient and magnolol in the bactericide is 0.05-0.20 mg / mL.

[0012] Furthermore, the fungicide is applied by foliar spraying or root drenching.

[0013] Furthermore, the formulations of bactericides include emulsifiable concentrates, suspensions, water-in-oil emulsions, wettable powders, microemulsions, or water-dispersible granules.

[0014] Due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention discloses the application of magnolol in the preparation of fungicides for the prevention and control of plant fungal diseases. Magnolol is derived from plants and is a green, environmentally friendly, and highly safe small molecule compound with a broad antibacterial spectrum and long-lasting effect. It can effectively prevent and control plant diseases in peanuts, corn, wheat, leeks, soybeans, peppers, and tomatoes, and can be applied to various grains, fruits, vegetables, and other economic crops. Moreover, it is safe for non-target organisms, meets the requirements of green and sustainable development, and has broad application value. Attached Figure Description

[0015] Figure 1 The image shows the antibacterial effects of magnolol on peanut white mold, corn sheath blight, wheat stem base rot, leek gray mold, soybean root rot, pepper anthracnose, and tomato black spot. Figure 2 These are potted peanut plants with white mold disease in the magnolol treatment group and the sterile water spraying control group: A is a potted peanut plant with white mold disease in the sterile water spraying control group; B is a potted peanut plant with white mold disease in the magnolol treatment group; C is a peanut root and stem image in the sterile water spraying control group; D is a peanut root and stem image in the magnolol treatment group. Figure 3 These are potted wheat plants with stem base rot treated with magnolol and those treated with sterile water: A is a potted wheat plant with stem base rot in the sterile water control group; B is a potted wheat plant with stem base rot treated with magnolol; C is a root and stem image of wheat with stem base rot in the sterile water control group; D is a root and stem image of wheat with stem base rot treated with magnolol. Figure 4 These are potted maize plants with sheath blight in the magnolol treatment group and the sterile water spraying control group: A is a potted maize plant with sheath blight in the sterile water spraying control group; B is a potted maize plant with sheath blight in the magnolol treatment group; C is a root and stem image of maize with sheath blight in the sterile water spraying control group; D is a root and stem image of maize with sheath blight in the magnolol treatment group. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: Effects of magnolol on the mycelial growth of plant disease fungi

[0018] 1.1 Experimental Materials Honokiol was purchased from Maclean's Reagent Co., Ltd. 10 mg of honokiol was weighed and dissolved in 1 mL of anhydrous ethanol to prepare a 10 mg / mL honokiol stock solution. The solution was filtered to remove bacteria and stored at -20 °C for later use.

[0019] Test strain: *Sclerotium sclerotiorum*, the pathogen causing white mold disease in peanuts ( Sclerotium rolfsii ), the pathogen of corn sheath blight is Rhizoctonia solani ( Rhizoctonia solani ), Fusarium graminearum, the pathogen of wheat stem rot ( Fusarium pseudograminearum ), the pathogen of gray mold in chives, Botrytis cinerea ( Botrytis squamosa ), Fusarium tumefaciens, the pathogen of soybean root rot ( Fusarium Anthracnose, the pathogen of pepper anthracnose ( Colletotrichum ) and Alternaria alternata, the pathogen of tomato black spot disease ( Alternaria alternate ), among which, Fusarium, the pathogen of soybean root rot ( Fusarium Provided by the College of Plant Protection, South China Agricultural University, the pathogen of gray mold in leeks is *Botrytis cinerea* (allium bracteatum). Botrytis squamosa ) and Alternaria alternata, the pathogen of tomato black spot disease ( Alternaria alternate (This is a record kept by the laboratory of Henan University of Urban Construction.)

[0020] 1.2. The effect of magnolol on inhibiting fungal mycelial growth. (1) Preparation of drug-containing plates: Under aseptic conditions, 3000 μL, 2000 μL, 1000 μL, 500 μL, 250 μL and 125 μL of magnolol stock solution with a concentration of 10 mg / mL were respectively added to 100 mL of PDA medium at a temperature of about 50 ℃, and thoroughly mixed to prepare drug-containing medium with concentrations of 0.2 mg / mL, 0.1 mg / mL, 0.05 mg / mL, 0.025 mg / mL and 0.0125 mg / mL. The medium was poured into a petri dish with a diameter of 80 mm, with a PDA plate without drug-containing plate as a control. (2) Observation of antibacterial activity: After the drug-treated plates solidified, the inhibition of mycelial growth was measured using the mycelial growth rate assay. A mycelial cake with a diameter of 8 mm was taken from the edge of the pre-cultured test bacteria on the PDA plate and inoculated into the center of the drug-treated plate with the mycelial side facing down. Each treatment was repeated 3 times. *Gyromyces leekus* was cultured at 25 ℃, and other mycelial species were cultured at 28 ℃. When the control colonies covered more than two-thirds of the culture dish, the colony diameter (mm) was measured using the cross-sectional method, and the growth inhibition rate was calculated using the following formula:

[0021] The obtained data were analyzed and processed using SPSS 2024 software to derive the standard curve and EC50. 50 value; The antibacterial effects of magnolol on peanut white mold, corn sheath blight, wheat stem base rot, leek gray mold, soybean root rot, pepper anthracnose, and tomato black spot are as follows: Figure 1 As shown in Table 1, the inhibition rates of different concentrations of magnolol on the mycelial growth of the tested fungi are listed. The toxicity equation and EC50 of magnolol on fungal mycelium are also presented. 50 Listed in Table 2.

[0022] 1.3 Results and Analysis from Figure 1 Tables 1 and 2 show that the compound and magnolol can effectively control peanut white mold, corn sheath blight, wheat stem base rot, leek gray mold, soybean root rot, pepper anthracnose, and tomato black spot. The effective concentration of magnolol to inhibit the mycelial growth of these seven fungi is 0.05-0.2 mg / mL, and the concentration of EC50 for inhibiting these pathogens is [missing information]. 50 The concentration ranges from 0.008 to 0.055 mg / mL. Specific experimental results are shown in Tables 1 and 2.

[0023]

[0024]

[0025] Example 2: Results of a pot experiment on the control of peanut white mold with magnolol Peanut seeds were germinated for 3 days in moist gauze. Peanut seeds of uniform growth were then buried in flowerpots 8 cm in diameter and 7 cm high. After 5 days, the roots were incised with a scalpel, and two 8 mm mycelium cakes were buried at the wounds. Two days after inoculation, the peanut plants were drenched in a 0.2 mg / mL magnolol solution. A water treatment served as a negative control. Each treatment involved at least 20 seedlings, and the treatment was repeated three times. All peanut plants were grown in a greenhouse at 25 ℃ with a 16-hour photoperiod. Peanut disease incidence was assessed after 14 days. The severity of peanut white mold disease was graded as follows:

[0026] Level 0: The plant shows no symptoms; Grade 1: Lesions only appear at the base of the stem; Grade 3: The stem base shows constriction symptoms, and the last 1 / 3 or less of the plant shows systemic symptoms such as wilting, death, and drooping. Level 5: Ultimately, less than 2 / 3 of the plants exhibit systemic symptoms, such as wilting, death, and drooping. Level 7: Ultimately, more than 2 / 3 of the plants exhibit systemic symptoms, such as wilting, death, and drooping. Level 9: The entire plant eventually dies.

[0027] Disease index = Σ (Number of diseased plants at each level × Disease value at that level) / (Total number of plants surveyed × Highest level value) × 100% Prevention and control effect = (Control disease index - Treatment disease index) / Control disease index × 100% The results of indoor control of peanut white mold by the control group and magnolol are listed in Table 3. Figure 2 As shown.

[0028]

[0029] Table 3 and Figure 2 The experimental results showed that the average disease incidence rate in the control group was 100%, while the disease incidence rates in the magnolol-treated groups were 76.92%, 76.00%, and 73.91%, with an average disease incidence rate of 75.61%. The disease indexes in the control group were 69.78%, 62.72%, and 63.49%, respectively, while those in the treated groups were 27.35%, 33.33%, and 53.61%, respectively. The control effects were 60.81%, 46.86%, and 53.61%, respectively, with an average control effect of 53.76%. This indicates that magnolol treatment has a good control effect on peanut white mold.

[0030] Example 3: Results of a pot experiment on the control of wheat stem base rot with magnolol After washing 100 g of wheat grains, soak them in water for 12 hours. Then, place them in an Erlenmeyer flask and sterilize them at 121 ℃ for 20 minutes. After cooling, inoculate 6 pieces of *Fusarium graminearum* mycelium cakes with a diameter of 8 mm that have been cultured for 3 days. Place them in an incubator at 28 ℃ and shake the flask every 12 hours to ensure that the mycelium fully infects the wheat grains. After all the wheat grains are infected by the mycelium, remove them and dry them. These are wheat grains with stem rot. Store them at 4 ℃ for use in infecting potted wheat.

[0031] Seeds were germinated for 2 days in moist gauze. Wheat seeds of uniform growth were buried in flowerpots 8 cm in diameter and 7 cm high. Two diseased wheat grains were buried at the base of the wheat plants. Two days after inoculation with the diseased grains, the wheat roots were drenched with a 0.2 mg / mL solution of magnolol. A water treatment served as a negative control. Each treatment had at least 20 seedlings, and the treatment was repeated three times. All wheat plants were grown in a greenhouse at 25 ℃ with a photoperiod of 16 h. After 14 days, the infection effect at the base of the wheat stem was observed. The seedling disease severity grading for wheat stem base rot is as follows: Level 0: The plant shows no symptoms; Grade 1: Browning appears on the leaf sheath; Level 3: The first leaf shows signs of browning; Level 5: The second leaf shows signs of browning; Level 7: The third leaf shows signs of browning; Level 9: Plant dead.

[0032] Disease index = Σ (Number of diseased plants at each level × Disease value at that level) / (Total number of plants surveyed × Highest level value) × 100% Relative efficacy = (Control disease index - Treatment disease index) / Control disease index × 100% The results of indoor control of peanut white mold by the control group and magnolol are listed in Table 4. Figure 3 As shown.

[0033]

[0034] Table 4 and Figure 3 The experimental results showed that the average disease incidence rate in the control group was 97.15%, while the disease incidence rates in the magnolol-treated groups were 75.00%, 80.00%, and 76.00%, respectively, with an average disease incidence rate of 77.00%. The disease indexes in the control group were 62.22%, 57.27%, and 59.09%, respectively, while those in the treated groups were 26.11%, 31.11%, and 29.78%, respectively. The control effects were 58.04%, 45.68%, and 49.60%, respectively, with an average control effect of 51.11%. This indicates that magnolol treatment has a good control effect on wheat stem rot.

[0035] Example 4: Results of a pot experiment on the control of maize sheath blight with magnolol Corn seeds were germinated for 3 days by placing them in moist gauze. Seeds of uniform growth were then buried in flowerpots with a diameter of 8 cm and a height of 7 cm. Simultaneously, two 8 mm pieces of corn sheath blight fungal cake were buried at the base of the corn plants. Two days after inoculation, the corn plants were treated with a 0.2 mg / mL solution of magnolol, with a water treatment serving as a negative control. Each treatment had at least 20 seedlings, and the treatment was repeated three times. All corn plants were grown in a greenhouse at 25 ℃ with a photoperiod of 16 h. The infection effect at the base of the corn stem was observed after 10 days. The seedling disease severity grading for corn sheath blight is as follows: Level 0: The plant shows no symptoms; Grade 1: Leaf sheaths have lesions, the area of ​​which is less than 1 / 4 of the leaf sheath; Grade 2: Leaf sheath lesions cover 1 / 4 to 1 / 2 of the leaf sheath area; Grade 3: Leaf sheath lesions cover 1 / 2-3 / 4 of the leaf sheath area, and the lower leaves of the plant are affected; Level 4: Leaf sheath lesions cover more than 3 / 4 of the leaf sheath, and the lower leaves of the ear are affected; Level 5: Severe disease in leaf sheaths, leading to plant death.

[0036] Disease index = Σ (Number of diseased plants at each level × Disease value at that level) / (Total number of plants surveyed × Highest level value) × 100% Relative efficacy = (Control disease index - Treatment disease index) / Control disease index × 100% The results of indoor control of peanut white mold by magnolol are shown in Table 5. Figure 4 As shown.

[0037]

[0038] Table 5 and Figure 4 The experimental results showed that the average disease incidence rate in the control group was 100%, while the disease incidence rates in the magnolol-treated groups were 63.64%, 64.00%, and 65.38%, respectively, with an average disease incidence rate of 64.34%. The disease indexes in the control group were 75.93%, 71.56%, and 75.11%, respectively, while those in the treated groups were 19.19%, 23.11%, and 23.50%, respectively. The control effects were 74.73%, 67.71%, and 68.71%, respectively, with an average control effect of 70.38%. This indicates that magnolol treatment has a good control effect on maize sheath blight.

[0039] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. Application of magnolol in the preparation of fungicides for the prevention and control of plant fungal diseases.

2. The application according to claim 1, characterized in that: Plant fungal diseases include peanut white mold, corn sheath blight, wheat stem base rot, leek gray mold, soybean root rot, pepper anthracnose, or tomato black spot.

3. The application according to claim 2, characterized in that: The fungi mentioned are: *Sclerotium sclerotiorum*, the pathogen of peanut white mold; *Rhizoctonia solani*, the pathogen of corn sheath blight; *Fusarium graminearum*, the pathogen of wheat stem base rot; *Botrytis cinerea*, the pathogen of leek gray mold; *Fusarium graminearum*, the pathogen of soybean root rot; *Anthracnose*, the pathogen of pepper anthracnose; or *Alternaria alternata*, the pathogen of tomato black spot.

4. The application according to claim 2, characterized in that: The inhibition rate of magnolol on the mycelial growth of plant pathogenic fungi was dose-dependent.

5. The application according to claim 2, characterized in that: The concentration of the active ingredient and magnolol in the bactericide is 0.05-0.20 mg / mL.

6. The application according to claim 2, characterized in that: The fungicide is applied by foliar spraying or root irrigation.

7. The application according to claim 2, characterized in that: The formulations of bactericides include emulsifiable concentrates, suspension concentrates, water-in-oil emulsions, wettable powders, microemulsions, or water-dispersible granules.

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