Application of lemon eucalyptus essential oil

Abstract

The invention discloses application of lemon eucalyptus essential oil, and particularly relates to application of the lemon eucalyptus essential oil in preparation of a product for preventing and treating phytophthora nicotianae. In order to realize green prevention and control of crop diseases, efficient bactericidal active components are screened from medicinal plants, and the bacteriostatic activity of the lemon eucalyptus essential oil to phytophthora nicotianae is determined by adopting a hypha growth rate method. The result shows that the lemon eucalyptus essential oil has a remarkable inhibition effect on the growth of phytophthora nicotianae hypha; in a direct contact mode, the inhibition efficiency of the lemon eucalyptus essential oil on phytophthora nicotianae is 7.33-60.86%. When the concentration of the essential oil is maximum, most of the mycelia are expanded, almost no obvious complete mycelia and sporophytes are found, and the mycelia are broken and distorted more seriously. The lemon eucalyptus essential oil has the advantages of high efficiency, environment friendliness, low cytotoxicity, low residue, easiness in degradation and the like, and is expected to become a novel environment-friendly pesticide for preventing and treating phytophthora nicotianae.

Description

Technical Field

[0001] The invention belongs to the technical field of biological applications, and further belongs to the technical field of biological pesticides, and specifically relates to an application of lemon eucalyptus essential oil. Background Art

[0002] Phytophthora nicotianae Phytophtora parasitica var. nicotianae Tucker is a soil-borne pathogen that mainly parasitizes on plants of the Solanaceae, Araceae and Passifloraceae families. It can cause rhizome rot, leaf wilt and other diseases in tobacco, konjac, passion fruit and other plants, especially in Yunnan tobacco-growing areas, causing serious economic losses to tobacco farmers. Tobacco phytophthora can cause root and stem rot and leaf wilt, and can infect and cause disease at all growth stages of tobacco growth. At present, the prevention and control of this disease mainly adopts the method of continuous and large-scale use of chemical pesticides, which leads to the production of resistant physiological subspecies of pathogens, the destruction of soil microbial communities, the destruction of farmland ecological environment and the excessive pesticide residues in agricultural products, which harms human health. Therefore, it is extremely important to develop safe, effective and environmentally friendly bio-source pesticides to replace chemical pesticides.

[0003] Essential oils are secondary metabolites derived from different parts of plants. In recent years, with the increasing demand for green and safe agricultural products, the use of essential oils as a substitute for traditional chemical pesticides has become a hot topic in the study of agricultural diseases. Eucalyptus citriodora Hook.) is an evergreen large tree of the Myrtaceae family and the genus Eucalyptus. It is native to Australia and is cultivated in southern China, Fujian, Sichuan and other places. Lemon eucalyptus essential oil contains citronellal, citronellol and other main aromatic substances. Existing studies have found that it has antibacterial, anti-inflammatory, nematicidal and insecticidal effects, but there is no report on whether lemon eucalyptus essential oil has the activity of inhibiting tobacco phytophthora. Summary of the invention

[0004] The first purpose of the present invention is to provide an application of lemon eucalyptus essential oil; the second purpose is to provide a fungicide for preventing and controlling tobacco blight.

[0005] The first object of the present invention is achieved by using the lemon eucalyptus essential oil in the preparation of a product for preventing and controlling tobacco phytophthora.

[0006] The second object of the present invention is achieved in that the fungicide for controlling tobacco blight is composed of lemon eucalyptus essential oil, an organic solvent or an emulsifier.

[0007] In order to achieve green prevention and control of crop diseases, the present invention screens efficient bactericidal active ingredients from medicinal plants, and uses the mycelium growth rate method to determine the antibacterial activity of lemon eucalyptus essential oil on tobacco phytophthora. The results show that lemon eucalyptus essential oil has a significant inhibitory effect on the growth of tobacco phytophthora hyphae: under direct contact, the efficiency of lemon eucalyptus essential oil on tobacco phytophthora inhibition is 7.33-60.86%. Lemon eucalyptus essential oil has a significant effect on the morphology of tobacco phytophthora hyphae, making the mycelium surface no longer smooth, the mycelium bending increases, and the germination on the mycelium increases, and the mycelium branching increases significantly. When the essential oil concentration is the highest, most of the mycelium shows swelling, and almost no obvious complete mycelium and spore body are seen, and the mycelium fracture and distortion phenomenon are more serious. The present invention finds that lemon eucalyptus essential oil has many advantages such as high efficiency, environmental protection, low cytotoxicity, low residue and easy degradation, and is expected to become a new environmentally friendly pesticide for preventing and controlling tobacco phytophthora. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Effect of eucalyptus citriodora essential oil on the colony size of Phytophthora nicotianae.

[0009] Figure 2 The inhibitory efficiency of different concentrations of lemon eucalyptus essential oil on tobacco phytophthora.

[0010] Figure 3 The effect of lemon eucalyptus essential oil on the hyphal morphology of tobacco Phytophthora. DETAILED DESCRIPTION

[0011] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0012] The application of the lemon eucalyptus essential oil of the present invention is the application of the lemon eucalyptus essential oil in the preparation of a product for preventing and controlling tobacco phytophthora.

[0013] The product described is a pesticide.

[0014] The product is a microemulsion, an aerosol or an aqueous emulsion.

[0015] The tobacco bactericide of the present invention is composed of lemon eucalyptus essential oil and an organic solvent or an emulsifier.

[0016] The volume ratio of the lemon eucalyptus essential oil to the organic solvent or emulsifier is 1: (1-10).

[0017] The concentration of the lemon eucalyptus essential oil is above 42.35 μg / mL.

[0018] The organic solvent is acetone or ethanol, and the emulsifier is Tween-20 or Tween-80.

[0019] The lemon eucalyptus essential oil of the present invention comprises the steps of preparing the essential oil agent, using the lemon eucalyptus essential oil agent, and observing the disease-resistant morphology of the lemon eucalyptus essential oil agent when preparing the fungicide for preventing and controlling tobacco phytophthora. Specifically, the steps include: 1. Preparation of lemon eucalyptus essential oil: Mix lemon eucalyptus essential oil with Tween-20 or Tween-80 or acetone or ethanol in a ratio of 1:1 to 10 times, mix well and set aside; 2. Essential oil pharmaceutical treatment Under sterile conditions, first dissolve different volumes of essential oils of medicinal plants in organic solvents or emulsifiers, add 20 mL of sterilized rye solid culture medium, mix thoroughly, pour into a culture dish, and wait for it to cool naturally. Use a hole puncher to take a 5 mm diameter tobacco phytophthora cake under sterile conditions and insert it into the center of the culture medium. After sealing with a sealing film, place it at 25 ℃ for about 4 days, observe the size and shape of tobacco phytophthora plaques, measure the colony diameter, and calculate the antibacterial rate and effective medium concentration (EC50 value).

[0020] 3. Effect of lemon eucalyptus essential oil on mycelial morphological growth The mycelial morphology after treatment with lemon eucalyptus essential oil was observed using a scanning electron microscope. The bacterial cakes after 5 days of culture were inoculated on rye culture medium with / without lemon eucalyptus essential oil, and cultured for about 4 days until the mycelium of the control group approached the edge of the culture dish. The samples were placed under a scanning electron microscope to observe the mycelial morphology.

[0021] The present invention is further described below with specific implementation cases: Example 1 Preparation of lemon eucalyptus essential oil preparation: Mix lemon eucalyptus essential oil with Tween-20 at a ratio of 1:10, mix thoroughly, and then dilute with distilled water to make the final concentration of lemon eucalyptus essential oil 10 μg / mL.

[0022] Example 2 Preparation of lemon eucalyptus essential oil: Mix lemon eucalyptus essential oil with Tween-80 in a ratio of 1:7, mix thoroughly, and then dilute with distilled water to make the final concentration of lemon eucalyptus essential oil 25 μg / mL.

[0023] Example 3 Preparation of lemon eucalyptus essential oil preparation: Mix lemon eucalyptus essential oil with acetone in a ratio of 1:5, mix thoroughly, and then dilute with distilled water to make the final concentration of lemon eucalyptus essential oil 50 μg / mL.

[0024] Example 4 Preparation of lemon eucalyptus essential oil: Mix lemon eucalyptus essential oil with ethanol in a ratio of 1:1, mix thoroughly, and then dilute with distilled water to make the final concentration of lemon eucalyptus essential oil 250 μg / mL.

[0025] Example 5 Calculation of lemon eucalyptus essential oil concentration: Take 1, 2, 3, 4 and 5 μL of lemon eucalyptus essential oil, mix thoroughly with an appropriate amount of organic solvent or emulsifier, and add them to 20 mL of rye solid culture medium. Based on the density of lemon eucalyptus essential oil of 0.8470 g / mL, the final concentrations of lemon eucalyptus essential oil in the culture medium are 42.35 μg / mL, 84.70 μg / mL, 127.05 μg / mL, 169.40 μg / mL and 211.75 μg / mL, respectively.

[0026] Example 6 Observation of tobacco phytophthora plaques treated with essential oil agents: Under sterile conditions, different volumes of medicinal plant essential oils were first dissolved in 0.5% Tween 80 solution, added to 20 mL of sterilized rye solid culture medium, mixed thoroughly, poured into a culture dish (90 mm in diameter), and allowed to cool naturally. Use a hole puncher to take a 5 mm diameter tobacco phytophthora cake under sterile conditions and insert it into the center of the culture medium. After sealing with a sealing film, place it at 25 °C for about 4 days to observe the size and shape of tobacco phytophthora plaques.

[0027] The results are as follows Figure 1 As shown: Different concentrations of lemon eucalyptus essential oil had a significant inhibitory effect on tobacco phytophthora, inhibiting the growth of tobacco phytophthora hyphae. Compared with the blank control group, lemon eucalyptus essential oil treatment caused the tobacco phytophthora colony to become significantly smaller, and the higher the concentration, the more significant the inhibitory effect.

[0028] Example 7 The inhibitory effect of different concentrations of lemon eucalyptus essential oil on tobacco phytophthora: A 5 mm diameter tobacco phytophthora cake was taken with a hole punch under sterile conditions and inoculated into the center of a rye culture medium containing different essential oil concentrations (0, 1, 2, 3, 4 and 5 μL). After sealing with a sealing film, it was cultured at 25 ℃ for about 5 days. The colony diameter was measured and the inhibition rate was calculated. Each treatment was repeated 3 times. The inhibition rate was calculated according to the following formula: Inhibition rate (%) = (dC - dT) / (dC - 5) × 100. In the formula: dC is the control colony diameter; dT is the colony diameter under different treatment conditions. For the antibacterial activity of the above essential oils of different mass concentrations against tobacco phytophthora, the regression equation y = a + bx and the effective median concentration (EC50 value) were calculated.

[0029] The results are as follows Figure 2As shown in the figure, by calculating the mycelial growth inhibition rate, it was found that lemon eucalyptus essential oil had a significant inhibitory effect on the mycelial growth of tobacco phytophthora, and it was concentration-dependent. With the increase of concentration, its inhibitory effect increased. At a higher concentration (211.75 μg / mL), the inhibition efficiency of lemon eucalyptus essential oil reached 60.86%. At a lower concentration (42.35 μg / mL), its inhibition rate on tobacco phytophthora was 7.33%. According to the inhibition rate of different concentrations, the regression equation was obtained as Y = 0.3129*X - 8.155 ( R ²=0.9771), the EC50 value of lemon eucalyptus essential oil against tobacco phytophthora was 185.9 μg / mL, indicating that it has a good inhibitory effect on tobacco phytophthora.

[0030] Example 8 Effect of lemon eucalyptus essential oil on hyphae morphology of tobacco phytophthora: The hyphae morphology after treatment with lemon eucalyptus essential oil was observed using a scanning electron microscope. The bacterial cakes after 5 days of culture were inoculated on rye culture medium with / without lemon eucalyptus essential oil, and cultured for about 4 days until the hyphae of the control group approached the edge of the culture dish. The samples were placed under a scanning electron microscope to observe the hyphae morphology.

[0031] The results are as follows Figure 3 It was shown that lemon eucalyptus essential oil had a great influence on the growth state of tobacco phytophthora hyphae. The hyphae of the blank control group were uniformly filamentous, with a smooth surface, uniform distribution of internal substances, longer hyphae, fewer branches, no obvious abnormal swelling, and no obvious conidia. The surface of the hyphae of tobacco phytophthora treated with lemon eucalyptus essential oil was no longer smooth, the hyphae were more curved, and the number of germinations on the hyphae increased, and the number of hyphae branches increased significantly. When the concentration of essential oil was the highest, most of the mycelium showed swelling, and almost no obvious complete mycelium and spores were seen, and the mycelium was broken and deformed more seriously. Vacuoles appeared inside some mycelium, which may be caused by the destruction of the internal structure of the mycelial cells, the damage of the cell membrane, and the release of endolysates to the outside of the cells after the treatment of lemon eucalyptus essential oil.

Claims

1. An application of lemon eucalyptus essential oil, characterized in that: The application of the lemon eucalyptus essential oil in preparing a product for preventing and treating tobacco blight.

2. The use of lemon eucalyptus essential oil according to claim 1, characterized in that: The product described is a pesticide.

3. The use of lemon eucalyptus essential oil according to claim 1 or 2, characterized in that: The product is a microemulsion, an aerosol or an aqueous emulsion.

4. A fungicide for controlling tobacco phytophthora, characterized in that: The fungicide for preventing and controlling tobacco blight is composed of the lemon eucalyptus essential oil according to claim 1 and an organic solvent or an emulsifier.

5. The agent for controlling tobacco phytophthora according to claim 4, characterized in that: The volume ratio of the lemon eucalyptus essential oil to the organic solvent or emulsifier is 1: (1-10).

6. The agent for controlling tobacco phytophthora according to claim 4 or 5, characterized in that: The concentration of the lemon eucalyptus essential oil is above 42.35 μg / mL.

7. The agent for controlling tobacco phytophthora according to claim 4 or 5, characterized in that: The organic solvent is acetone or ethanol, and the emulsifier is Tween-20 or Tween-80.

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