Application of lavender essential oil in preventing and controlling black rot of pineapple

Abstract

The invention belongs to the technical field of post-harvest disease prevention and control of fruits, and discloses an application of lavender essential oil in preventing and controlling the occurrence of pineapple black rot. The application method is: the lavender essential oil is diluted and used for surface treatment of pineapples after picking to prevent and control the occurrence of pineapple black rot. The lavender essential oil is prepared by the following method: lavender dried flowers are crushed and put into a distiller, distilled water is added for soaking, ultrasonic-assisted distillation reflux extraction is performed to obtain an oil-water mixture, and then oil-water separation is performed to obtain the lavender essential oil. The preparation method of the lavender essential oil of the invention is simple, fast and low in cost. The use of a single lavender essential oil can achieve an antibacterial effect of nearly 100% on pineapple black rot. The lavender essential oil is applied to the prevention and control of pineapple black rot, and has a significant effect, providing a safe and effective method for preventing and controlling the occurrence of pineapple black rot.

Description

Technical Field

[0001] The invention belongs to the technical field of post-harvest fruit disease prevention and control, and particularly relates to application of lavender essential oil in preventing and controlling the occurrence of pineapple black rot disease. Background Art

[0002] Pineapple (Ananas comosus L.) is the world's third largest tropical fruit after banana and mango as assessed by the Food and Agriculture Organization of the United Nations (FAO). my country is the world's fifth largest pineapple producer. In 2022, the national pineapple planting area exceeded 1 million mu, with a total output of about 1.72 million tons (FAO, 2022). my country's main pineapple producing areas are in Guangdong, Guangxi, Hainan, Fujian, Yunnan, Guizhou and Taiwan. Among them, Guangdong Province is the largest pineapple producing area in my country, with a planting area accounting for about 80% of my country's total pineapple planting area. The pineapple industry plays an important role in promoting rural revitalization and increasing farmers' income, and has become a pillar industry in my country's tropical agriculture. However, pineapple fruits are prone to rot and deterioration during storage and transportation after harvest, resulting in quality deterioration such as poor taste and flavor of the fruit, which seriously affects the healthy development of the pineapple industry.

[0003] The main factor leading to post-harvest pineapple fruit rot is the disease caused by pathogenic microorganisms, among which pineapple black rot is one of the main diseases, caused by Thielaviopsis paradoxa (de seyn.) V. Hohn. For a long time, the main measure to control pineapple black rot is the use of fungicides, such as carbendazim, methyl tobacillus and benomyl. Although traditional commercial chemical fungicides have low cost, fast bactericidal effect and convenient application, with the popularization and promotion of environmental protection concepts, the long-term and large-scale use of chemical fungicides has brought potential threats to agricultural ecology and consumer food safety. Therefore, it is necessary to find a safer, more environmentally friendly and efficient method to control pineapple black rot.

[0004] Patent CN 111345297 A discloses a pesticide composition for preventing and controlling pineapple black rot, wherein the active ingredients are compounded with thymol and fluopicolide, fluopicolide, syringoxystrobin, cyproconazole or dimethomorph. There is no cross-resistance between the two compounded active ingredients in the pesticide composition for preventing and controlling pineapple black rot, and the two active ingredients have obvious synergistic effect after compounding, which can improve the prevention and control effect of pineapple black rot, reduce the single use dosage of the agent, reduce the prevention and control cost, reduce pesticide residues; and delay the generation of pathogen resistance. However, its safety and environmental protection still need to be further improved. Patent CN 111602711A discloses a composition for preventing and controlling postharvest black rot of pineapple, wherein the composition includes an aqueous solution of sodium dehydroacetate and glacial acetic acid. Among them, the concentration of sodium dehydroacetate is 0.5g / L~2g / L, and the concentration of glacial acetic acid is 0.25%~0.5% (V / V). The composition has excellent control effect on postharvest black rot of pineapple. However, the composition requires the use of two components in combination, and the control effect of a single component is poor. In addition, sodium dehydroacetate is a synthetic food preservative, and its safety and acceptability are still inferior to those of natural products.

[0005] Lavender (Lavandula angustifolia Mill.) is a plant of the genus Lavandula in the family Lamiaceae. It is mainly grown in Xinjiang and Shaanxi in China. It is a perennial subshrub with a strong aromatic smell. Essential oil can be extracted from the whole plant. Because the extracted essential oil has high quality, strong fragrance, pure smell, non-toxicity, hypnotic and sedative properties, it is widely used in the medical and skin care industries and is often used as a raw material for antibacterial agents. Studies have found that lavender is a potential broad-spectrum antibacterial substance that can inhibit the growth of a variety of fungi that cause fruit rot. At present, there are no reports on the use of lavender essential oil to prevent and control the pathogens of pineapple black rot. Summary of the invention

[0006] Based on the biological activity potential of lavender essential oil and its beneficial effects on human health, the present invention aims to provide an application of lavender essential oil in preventing and controlling the occurrence of pineapple black rot. Lavender essential oil is extracted and used in the study of pineapple preservation.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] Application of lavender essential oil in preventing and controlling pineapple black rot disease, wherein the lavender essential oil is prepared by the following method:

[0009] The dried lavender flowers are crushed and put into a distiller, and then soaked in distilled water, and ultrasonic-assisted distillation and reflux extraction are performed to obtain an oil-water mixture, and then the oil and water are separated to obtain lavender essential oil.

[0010] Furthermore, the application method is: diluting the lavender essential oil and using it for surface treatment of picked pineapples to prevent and control the occurrence of pineapple black rot.

[0011] Furthermore, the concentration of the diluted lavender essential oil is ≥700 μL / mL.

[0012] Furthermore, the maturity of the picked pineapples is 75% to 80%.

[0013] Furthermore, the material-liquid ratio of the distilled water soaking is 1:1-5 g / mL.

[0014] Furthermore, the distilled water soaking time is 15 to 60 minutes.

[0015] Furthermore, the temperature of the ultrasound-assisted distillation reflux extraction is 100-150° C., and the time is 0.5-1.5 h.

[0016] Furthermore, the oil and water are cooled to 0 to -10°C before separation.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The preparation method of the lavender essential oil of the present invention is simple, rapid and low in cost. The lavender essential oil is applied to the prevention and treatment of pineapple black rot with remarkable effect, which not only effectively delays the occurrence time of the disease, but also significantly inhibits the development of the pathogen.

[0019] (2) The present invention uses a single lavender essential oil to achieve a nearly 100% antibacterial effect on pineapple black rot fungi.

[0020] (3) The lavender essential oil of the present invention is 100% natural plant extract components, and has high safety and acceptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a graph showing the effect of different concentrations of lavender essential oil on the colony diameter of pineapple black rot fungus in the example.

[0022] Figure 2 The graph is a result of the inhibitory effect of different concentrations of lavender essential oil on pineapple black rot fungi in the example.

[0023] Figure 3 This is a diagram showing the control effect of different concentrations of lavender essential oil on pineapple fruit inoculated with T. paradoxa in the example.

[0024] Figure 4 This is a graph showing the effects of different concentrations of lavender essential oil on the fruit rot area and control effect after pineapple fruit was inoculated with T. paradoxa in the example. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] (1) Test materials

[0028] Pineapple fruit for testing: The pineapple variety is "Bali" (Ananas comosus L.cv.'Comte de Paris'), which grows in the pineapple standardized production demonstration garden in Xuwen County, Zhanjiang City, Guangdong Province. The pineapples were harvested when the maturity was 75% to 80%, and the fruits were immediately transported back to the laboratory after picking. The fruits with uniform maturity, no mechanical damage and pests were selected, and the fruits were rinsed with double distilled water and dried at room temperature for later use.

[0029] Test strains: T. paradoxa, which causes pineapple black rot, was isolated and preserved by the Postharvest Physiology and Preservation Laboratory of Tropical Horticultural Products, South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences.

[0030] (2) Preparation of essential oils

[0031] Weigh 500g of dried lavender flowers accurately, crush them with a grinder, put them into a distiller, add 1000mL of distilled water and soak for 30min, and extract them by ultrasonic assisted distillation at 120℃ for 1h. The oil-water mixture is formed by reflux, and then cooled at 5℃ for oil-water separation to obtain the finished lavender essential oil.

[0032] (3) Gas chromatography-mass spectrometry (GC-MS) analysis conditions

[0033] Take 10 μL of the lavender essential oil prepared in step (2) and dilute it in 10 mL of methanol. Then take 1 mL of the diluted sample and place it in a 20 mL headspace bottle. Add 10 μL of 0.948×10 -2 g / mL cyclohexanol was used as internal standard, balanced at 40℃ for 20min, and extracted for 30min. The prepared lavender essential oil was qualitatively analyzed by GC-MS.

[0034] GC conditions: DB-WAX gas chromatography column (30m×250μm×0.25μm); injection volume 0.5μL; injection port temperature 250℃; carrier gas (He) flow rate 1.0mL / min. Column temperature program: 40℃ for 2min, increase to 200℃ at 4℃ / min and hold for 2min, increase to 230℃ at 5℃ / min and hold for 0min, the highest temperature is 250℃.

[0035] MS conditions: GC transfer line temperature 250°C; data acquisition mode full scan; EI ion source temperature 230°C; solvent delay 0 min; ion range 40-350u; scan time 0.35s; scan interval 0.05s.

[0036] The analysis results are shown in Table 1 below:

[0037] Table 1. Chemical composition analysis of lavender essential oil

[0038]

[0039]

[0040]

[0041] As can be seen from Table 1, the components of the prepared lavender essential oil were analyzed by GC / MS, and a total of 49 main compound components were detected, including 4 ethers, 9 alcohols, 21 alkenes, 9 esters, 3 alkanes and 3 aromatics. Some of these compounds, such as linalool and linalyl acetate, are considered to be the main antioxidant components of lavender essential oil, which were also confirmed in this experiment, proving that the extraction method of this experiment is authentic and reliable.

[0042] (4) Determination of antibacterial activity of lavender essential oil

[0043] The mycelium growth rate method was used to determine the inhibitory effect of lavender essential oil on the growth of pineapple black rot fungus T.paradoxa. A 7mm round sterile filter paper prepared in advance was placed in the center of the PDA culture medium, and 20μL of lavender essential oil with different dilutions (5% acetone solution as the dilution solvent) concentrations (200μL / mL, 300μL / mL, 400μL / mL, 500μL / mL, 600μL / mL and 700μL / mL) was dripped on the filter paper. Three replicates were set for each concentration, and the control contained only 5% acetone solution. Then, a number of bacterial cakes were punched out at the edge of T.paradoxa cultured for 3 days with a 5mm sterile puncher, and the cakes were pasted in the center of the filter paper, sealed with a sealing film, and cultured at 28±1℃ for 3 days. The colony diameter was measured every 24 hours using the cross method. The toxicity regression equation y=ax+b of lavender essential oil to T.paradoxa was calculated, and the effective median concentration (EC 50 value) and 95% effective concentration (EC 95 value).

[0044] Bacteria cake growth inhibition rate (%) = (control colony growth diameter - treatment colony growth diameter) / control colony growth diameter × 100%.

[0045] The results of the effects of different concentrations of lavender essential oil on the colony diameter of pineapple black rot fungus are as follows Figure 1 As shown in (different lowercase letters under the colony diameters at the same culture time indicate significant differences (p < 0.05)). Figure 1 The results showed that during the 3-day culture period, compared with the control, treatments with lavender essential oil at different concentrations including 300μL / mL, 400μL / mL, 500μL / mL, 600μL / mL and 700μL / mL all reduced the expansion rate of the colony diameter of pineapple black rot fungus, indicating that lavender essential oil had an inhibitory effect on the hyphae growth of pineapple black rot fungus, and this inhibitory effect showed an obvious concentration effect. With the increase of the concentration of lavender essential oil, the colony diameter gradually decreased. When the concentration of lavender essential oil reached 700μL / mL, the hyphae growth of pineapple black rot fungus was completely inhibited.

[0046] The results of the inhibitory effects of different concentrations of lavender essential oil on pineapple black rot fungi are as follows Figure 2 And as shown in Table 2.

[0047] Table 2. Analysis of the antibacterial effect of different concentrations of lavender essential oil on pineapple black rot bacteria

[0048]

[0049] Note: Different lowercase letters indicate significant differences (p<0.05)

[0050] Depend on Figure 2 As shown in the results of Table 2, with the increase of the concentration of lavender essential oil, the inhibitory effect becomes more and more obvious. When the volume concentration of lavender essential oil is 500 μL / mL, the inhibition rate is 37.5%, which shows weak inhibition; when the concentration is 600 μL / mL, the inhibition rate is 75.3%, which shows moderate inhibition; when the concentration is 700 μL / mL, the inhibition rate is the highest, which can be as high as 100%, showing strong inhibition, that is, the volume concentration of 700 μL / mL is the minimum inhibitory concentration (MIC) of lavender essential oil on pineapple black rot fungus.

[0051] The toxicity equation and EC of lavender essential oil were fitted based on the results of mycelium growth inhibition method. 50 and EC 95 See Table 3 for values.

[0052] Table 3. Effect of lavender essential oil on the EC of pineapple black rot fungus 50 Value and EC 95 value

[0053]

[0054] The results in Table 3 show that the EC50 and EC95 values ​​of lavender essential oil against pineapple black rot fungus are 411.34 μL / mL and 617.87 μL / mL, respectively.

[0055] (5) Test on the efficacy of lavender essential oil against challenge inoculation of pineapple black rot

[0056] The challenge inoculation method was used to determine the control effect of lavender essential oil treatment on the lesion diameter of pineapple black rot fungus. 50 and EC 95 Therefore, three lavender essential oil concentrations were set in the challenge inoculation experiment: 500 μL / mL, 600 μL / mL and 700 μL / mL, to detect the appropriate lavender essential oil concentration for controlling pineapple black rot fungus.

[0057] Materials and methods: 240 pineapple fruits obtained from the experimental materials in (1) were randomly divided into 4 groups, with 60 fruits in each group. A sterile toothpick was used to pierce an inoculation point about 2 mm deep in the middle of the surface of each pineapple. When the inoculation point no longer oozes juice, 10 μL of T. paradoxa spore suspension (1.0×10 7 Spores / mL). 2 hours after inoculation with T.paradoxa spore suspension, 15 μL of sterile water (containing 5% acetone) was injected into the inoculation point of the first group of fruits, which served as the control group; 15 μL of lavender essential oil with a concentration of 500 μL / mL, 600 μL / mL and 700 μL / mL was injected into the inoculation point of the fruits of the second to fourth groups, respectively. The fruits were then placed in a plastic basket, covered with a 0.02 mm thick perforated polyethylene film bag, and stored in a 25°C constant temperature box to observe the disease. The control effect of different concentrations of lavender essential oil on pineapple fruits inoculated with T.paradoxa on the 6th day was as follows Figure 3 The diameter of the lesions was measured, and SPSS26.00 software was used to perform statistical analysis on the antibacterial activity of lavender essential oil against pineapple black rot and the lesion diameter data.

[0058] Decay area (cm 2 ) = π × (lesion radius) 2 ;

[0059] Control effect (%) = (rot area of ​​control group - rot area of ​​treatment group) / rot area of ​​control group × 100;

[0060] Effects of different concentrations of lavender essential oil on the fruit rot area and control effect after pineapple inoculation with T. paradoxa Figure 3 and 4From the appearance of the fruit, the lesion area of ​​the control group was significantly larger than that of the treatment group. The control effects of 500μL / mL, 600μL / mL and 700μL / mL lavender essential oil on pineapple black rot were 43.5%, 56.8% and 75.2%, respectively. In comparison, the 700μL / mL lavender essential oil treatment had the best control effect on the challenge inoculated pineapple black rot disease.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An application of lavender essential oil in preventing and controlling the occurrence of pineapple black rot disease, characterized in that: The application method comprises: diluting the lavender essential oil and applying it to the surface of the harvested pineapple to prevent and control the occurrence of the pineapple black rot disease; The concentration of the diluted lavender essential oil is ≥700 µL / mL; The lavender essential oil is prepared by the following method: The dried lavender flowers are crushed and put into a distiller, and then distilled water is added for soaking, and ultrasonic-assisted distillation and reflux extraction are performed to obtain an oil-water mixture, and then the oil and water are separated to obtain lavender essential oil; The material-liquid ratio of the distilled water soaking is 1:1~5 g / mL; The temperature of the ultrasonic-assisted distillation reflux extraction is 100-150° C. and the time is 0.5-1.5 h; The oil and water are first cooled to 0~-10°C before separation.

2. The application of lavender essential oil in preventing and treating pineapple black rot disease according to claim 1, characterized in that: The maturity of the pineapple after picking is 75% to 80%.

3. The application of lavender essential oil in preventing and treating pineapple black rot disease according to claim 1, characterized in that: The distilled water soaking time is 15 to 60 minutes.

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