An essential oil composition for inhibiting the pathogen of chrysanthemum black spot disease

Abstract

The application discloses an essential oil composition for inhibiting Alternaria alternata. The essential oil used in the application is a volatile oil mixture extracted from natural aromatic plants, i.e., pelargonium and citronella, and has the advantages of safe source, no toxic side effect and effectiveness. The essential oil of pelargonium and the essential oil of citronella are combined to achieve synergistic effect, so that the inhibiting effect of the essential oil on Alternaria alternata is greatly improved. The essential oil composition of the application can be applied to the prevention and control of Alternaria alternata of chrysanthemum, so that the safety problems caused by chemical agents, the drug resistance problems and the environmental pollution problems caused by pesticide residues can be greatly reduced, and the essential oil composition is easy to popularize and apply.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of plant protection, and particularly relates to a kind of essential oil composition for inhibiting chrysanthemum black spot pathogen. BACKGROUND

[0002] Chrysanthemum morifolium belongs to the chrysanthemum family and is native to China. It is one of the world's four major cut flowers and one of China's ten traditional famous flowers, with high ornamental and economic value. In addition, chrysanthemum is an important category of food and medicinal functions in China, with the effects of dispelling wind and clearing heat, detoxifying, anti-inflammatory, antibacterial, and antioxidant, and is often used to treat wind-heat cold, headache, dizziness, red and swollen eyes, blurred vision, and other diseases, with high medicinal value.

[0003] In chrysanthemum production, various fungal pathogenic microorganisms cause infection, reducing or completely losing the yield, ornamental, medicinal, or edible value, and causing serious economic losses. Among them, black spot caused by Alternaria fungal infection of plant leaves is a widespread disease in chrysanthemum cultivars and production and transportation, with a large area of damage and a serious degree. Especially under the continuous cropping cultivation mode, the pathogenic microorganisms in the soil multiply and explode, which easily leads to the infection of plants or cuttings, and sometimes even threatens the entire production field.

[0004] Currently, black spot is mainly controlled by spraying fungicides. Unreasonable and unscientific use of pesticides has brought many problems: the rise of drug resistance, the increase of pesticide residues, soil pollution, and the destruction of the environment and ecological system, which threatens the safety of the local planting area and the ecological system. Therefore, seeking safe, efficient, and low-toxicity biological agents is an important measure for green prevention and control. Plant essential oils are volatile oil mixtures with specific fragrances extracted from the flowers, leaves, stems, roots, fruits, and seeds of aromatic plants in nature through different extraction methods, including alcohol, alkene, ester, ketone, and aldehyde compounds. Many studies have shown that some plant essential oils can be used to antagonize pathogenic fungi, kill insects, mites, and nematodes, etc., including lemon verbena, Chinese weeping willow, white spine branch, and grey basil essential oils, which have antibacterial activity against Colletotrichum, Monilinia fructicola, etc. Therefore, in-depth study of the mechanism of essential oils has far-reaching significance for the development of more efficient, stable, and specific green control products. SUMMARY

[0005] To solve the problems of pesticide misuse, abuse, pesticide residues, and increased drug resistance in the prevention and control of chrysanthemum black spot, the present application provides an essential oil composition for inhibiting chrysanthemum black spot pathogen, which is a combination of geranium and citronella essential oils, and has an inhibitory effect on the pathogenic fungus of the fungal disease Alternaria alternata.

[0006] The first object of the present application is to provide an essential oil composition for inhibiting Alternaria alternata, which is composed of geranium essential oil and citronella essential oil.

[0007] Preferably, the essential oil composition is composed of geranium essential oil and citronella essential oil in a volume ratio of 1:1.

[0008] The second object of the present application is to provide the use of geranium essential oil and citronella essential oil in combination for inhibiting Alternaria alternata.

[0009] The third object of the present application is to provide a method for preventing and treating chrysanthemum black spot, which comprises the step of using geranium essential oil and citronella essential oil in combination for inhibiting Alternaria alternata.

[0010] The present application has the following advantages:

[0011] Alternaria alternata, the pathogenic fungus of chrysanthemum black spot, is a fungus that can infect plants of multiple families and genera, has strong adaptability, and can harm more than one hundred crops and horticultural plants. Alternaria alternata mainly invades leaves, and after infection, multiple near-circular or irregular black-brown lesions are produced at the diseased site, causing serious damage.

[0012] The essential oil used in the present application is a volatile oil mixture extracted from the aromatic plant geranium and citronella in nature, which has the advantages of safe source, no toxic side effects, and effectiveness. By using geranium essential oil and citronella essential oil in combination, a synergistic effect is achieved, greatly improving the inhibitory effect of the essential oil on Alternaria alternata. The essential oil composition of the present application can be applied to the prevention and control of chrysanthemum black spot, greatly reducing the safety problems, drug resistance problems, and environmental pollution problems caused by pesticide residues, and is easy to popularize and apply. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 are the growth conditions of Alternaria mycelium on different culture media; wherein the sample labels on the figure: CK corresponds to the bottom and front of the control medium, geranium corresponds to the bottom and front of essential oil medium A, citronella corresponds to the bottom and front of essential oil medium B, and geranium + citronella corresponds to the bottom and front of essential oil medium C. DETAILED DESCRIPTION

[0014] The following examples are further illustrations of the present application and are not intended to limit the present application.

[0015] The geranium essential oil stock solution was purchased from Guangzhou Yazi Cosmetics Co., Ltd., product model: geranium (special grade FA-025-2), purity 100%; the citronella essential oil stock solution was purchased from Guangzhou Yazi Cosmetics Co., Ltd., product model: citronella (special grade FA-012), purity 100%.

[0016] Example 1

[0017] I. Preparation of culture medium

[0018] Control culture medium: add tween80 to the PDA culture medium solution which has been sterilized and slightly cooled but not yet solidified to a final concentration of 0.1% by volume, and then add PDA culture medium solution to 50 mL; then pour into a sterilized culture dish and solidify for use.

[0019] Essential oil culture medium A: dilute the geranium essential oil stock solution (mass fraction 100%) to 3200 times to obtain a geranium essential oil diluent, add 15.62 μL of the geranium essential oil diluent to the PDA culture medium solution which has been sterilized and slightly cooled but not yet solidified, then add tween80 as a cosolvent to a final concentration of 0.1% by volume, and then add PDA culture medium solution to 50 mL; then pour into a sterilized culture dish and solidify for use.

[0020] Essential oil culture medium B: dilute the citronella essential oil stock solution (mass fraction 100%) to 3200 times to obtain a citronella essential oil diluent, add 15.62 μL of the citronella essential oil diluent to the PDA culture medium solution which has been sterilized and slightly cooled but not yet solidified, then add tween80 as a cosolvent to a final concentration of 0.1% by volume, and then add PDA culture medium solution to 50 mL; then pour into a sterilized culture dish and solidify for use.

[0021] Essential oil culture medium C: dilute the geranium essential oil stock solution (mass fraction 100%) to 3200 times to obtain a geranium essential oil diluent, dilute the citronella essential oil stock solution (mass fraction 100%) to 3200 times to obtain a citronella essential oil diluent, mix the geranium essential oil diluent and the citronella essential oil diluent in a volume ratio of 1:1 to obtain an essential oil mixture, add 15.62 μL of the essential oil mixture to the PDA culture medium solution which has been sterilized and slightly cooled but not yet solidified, then add tween80 as a cosolvent to a final concentration of 0.1% by volume, and then add PDA culture medium solution to 50 mL; then pour into a sterilized culture dish and solidify for use.

[0022] II. Preparation of fungi for testing

[0023] In advance, inoculate the Alternaria alternata mycelium on ordinary PDA culture medium and cultivate at 25°C for 6 days; then use a puncher (diameter 5 mm) to punch to prepare an Alternaria alternata cake.

[0024] III. Experimental Methods

[0025] With sterilized inoculation stick, pick up single pie of Alternaria alternata, inoculate to the center of control medium or essential oil medium A, B, C respectively, make sure the mycelium of pie is downward in each dish. Seal the medium with sealing film, cultivate at 25℃ for 6 days. Result evaluation and analysis

[0026] After 6 days cultivation at 25℃, measure the colony diameter (reflecting mycelium growth), calculate the inhibition rate of mycelium growth of Alternaria alternata in different medium, inhibition rate (%) = (control colony diameter - treatment colony diameter) / (control colony diameter - pie diameter).

[0027] The joint action of two drugs is evaluated by King's formula. King's formula expression: q = E(A+B) / (EA+EB-EA*EB), where EA, EB represent the effect of A and B respectively when used alone; E(A+B) represents the effect of component A and component B when used in combination. The effect of two components after joint use is evaluated by interpreting the value of q. The meaning of q value: less than 0.55 is obvious antagonism; greater than 0.55 and less than 0.85 is antagonism; between 0.85-1.15 is simple addition; greater than 1.15 and less than 20 is enhancement; greater than 20 is significant enhancement.

[0028] IV. Experimental Results

[0029] The results are shown in Table 1, Figure 1 The inhibition rate of Alternaria alternata mycelium growth by 3200-fold diluted Pelargonium hirsutum L. essential oil (essential oil medium A) is 0.06, the inhibition rate of Alternaria alternata mycelium growth by 3200-fold diluted Citronella essential oil (essential oil medium B) is 0.24, and the inhibition rate of Alternaria alternata mycelium growth by combined use of 3200-fold diluted Pelargonium hirsutum L. essential oil and 3200-fold diluted Citronella essential oil (essential oil medium C) can reach 0.47; the q value calculated by King's formula is 1.60, that is, the inhibition rate effect after joint use of two essential oils is enhanced relative to the effect of Pelargonium hirsutum L. essential oil and Citronella essential oil used alone, and has obvious synergistic effect.

[0030] Table 1 Inhibition of 3200-fold diluted two essential oils and their mixture on Alternaria alternata growth

[0031]

Claims

1. The application of an essential oil composition in controlling Alternaria alternata, the pathogen causing black spot disease in chrysanthemums, characterized in that, The essential oil composition consists of geranium essential oil and lemongrass essential oil in a volume ratio of 1:

1.

2. A method for preventing and controlling black spot disease in chrysanthemums, characterized in that, The method includes the step of using an essential oil composition consisting of geranium essential oil and lemongrass essential oil in a volume ratio of 1:1 to control Alternaria alternata, the pathogen causing black spot disease in chrysanthemums.

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