Application of Artemisia argyi essential oil in prevention and treatment of soft rot of sweet potato

Abstract

The application belongs to the technical field of biological disease prevention and treatment, and particularly relates to application of wormwood essential oil in prevention and treatment of soft rot of sweet potato. The soft rot of sweet potato is caused by Rhizopus stolonifer. The wormwood essential oil is prepared by using a water vapor distillation method. In view of the broad-spectrum bacteriostasis of the wormwood essential oil, the wormwood essential oil is innovatively used in the prevention and treatment experiment of the soft rot of sweet potato. The preliminary experimental results show that the wormwood essential oil has a good bacteriostatic effect on the pathogenic bacteria Rhizopus stolonifer causing the soft rot of sweet potato. In view of the advantages of the wormwood essential oil such as safety, no pollution and natural source, based on the results, better technical reference and practical significance can be provided for the harvesting and preservation of sweet potato and the postharvest preservation of other crops.

Description

Technical Field

[0001] This application belongs to the field of biological disease prevention and control technology, specifically involving the application of Artemisia argyi essential oil in the prevention and control of sweet potato soft rot. Background Technology

[0002] sweet potato( Ipomoea batatas As a crop, (L.) Lam. contains abundant dietary fiber, sugar, vitamins, minerals and other essential nutrients. Because of its advantages such as drought resistance, tolerance to poor soil and stable yield, it is of great significance for ensuring food security and improving food structure.

[0003] Sweet potato soft rot is a common fungal disease during sweet potato storage. Studies have shown that *Rhizopus stolonifer* is the main pathogen causing sweet potato soft rot. Because the fungal spores are widely present in the air, they are highly prevalent in harvesting and storage environments. During storage, transportation, and sales, when the fungal spores come into contact with wounds on the sweet potato, the spores germinate and deliver fungal hyphae into the tissue, forming water-soaked lesions on the surface. This softens the affected tissue, causing a sour odor, and eventually leads to complete decay. Simultaneously, spores on the surface of the rotting sweet potato further infect surrounding sweet potatoes, resulting in extensive tuber rot and significant economic losses.

[0004] Current technologies commonly used to control postharvest diseases in sweet potatoes include the use of chemical fungicides such as 1-MCP and carbendazim, or surface heat sterilization and controlled atmosphere storage. However, the widespread use of chemical fungicides not only easily pollutes the environment, but studies have also shown that *Rhizopus spp.* is developing resistance to synthetic fungicides rapidly, thus increasing the cost of chemical control. Physical methods such as surface heat sterilization and controlled atmosphere storage are also costly, hindering their widespread adoption among farmers and limiting their application. Therefore, low-cost, green, safe, and efficient antimicrobial technologies have become a common goal in disease control in recent years. However, due to differences in disease types, crop types, and control effects, new control technologies and products still need to be explored for the control of sweet potato soft rot. Summary of the Invention

[0005] The purpose of this application is to provide a new application of Artemisia argyi essential oil in the prevention and control of sweet potato soft rot, thereby providing new prevention and control strategies for the storage and preservation of related agricultural products.

[0006] The technical solution adopted in this application is described in detail below.

[0007] Application of Artemisia argyi essential oil in the prevention and control of sweet potato soft rot; the sweet potato soft rot is caused by Rhizopus stolonifera; the sweet potato varieties are, for example: Shangshu 19, Xiguahong, and Hami; The mugwort essential oil mentioned above is, for example, mugwort leaf essential oil prepared by steam distillation; the specific preparation method is as follows: After drying, the mugwort leaves are crushed and soaked in water for 2 hours (mass ratio: mugwort leaves: water = 1:20). Then, the mixture is ultrasonically treated for 20 minutes. Subsequently, the soaked liquid is transferred to a distillation flask and distilled at 123°C for 6 hours. The fractions are collected, and the resulting product is mugwort essential oil.

[0008] The application of Artemisia argyi essential oil in the prevention and control of sweet potato soft rot can be combined with clove essential oil or carbendazim before application. When blending with clove essential oil, use concentrations of 2, 1, 1 / 2, 1 / 4, and 1 / 8 of the MIC value obtained during fumigation treatment, and employ the checkerboard dilution method for blending. The specific concentration and ratio reference is as follows: clove essential oil at a concentration of 0.2~1.0 g / L, and artemisia essential oil at a concentration of 1~2 g / L, with a volume ratio of clove essential oil: artemisia essential oil = 1~10:1. More specifically, examples include clove essential oil: artemisia essential oil ratios of 9:1, 7:3, 5:5, 3:7, or 1:9, or 4000mg / L:8000mg / L. When combined with carbendazim, the volume ratio of carbendazim (calculated as 98% wettable powder product) to 0.3~1.0g / L and artemisia essential oil to 4~8g / L is 0:10~10:0. Specific ratios are as follows: 10:0, 9:1, 7:3, 5:5, 3:7, 1:9, 0:10. The clove essential oil mentioned is, for example, clove essential oil prepared by steam distillation; the specific preparation method is as follows: After drying, the cloves are crushed and soaked in water for 2 hours (by mass ratio, mugwort:water = 1:20). Then, the mixture is ultrasonically treated for 30 minutes. Subsequently, the soaked liquid is transferred to a distillation flask and distilled at 120°C for 6 hours. The fractions are collected, and the resulting product is clove essential oil.

[0009] Sweet potato soft rot, as a storage-related disease, is directly related to human consumption. Therefore, its prevention and control face inherent demands related to food safety and natural, green, and natural methods. Cost-effectiveness is also a crucial technical consideration. Artemisia argyi, a traditional Chinese herbal medicine, has been shown to possess broad-spectrum antibacterial activity, leading to its widespread application in biomedicine and cosmetics. Given the broad-spectrum antibacterial properties of Artemisia argyi essential oil, this application innovatively conducted experiments on its use in the prevention and control of sweet potato soft rot. It was also combined with clove essential oil, a previously available technology. Preliminary experimental results show that Artemisia argyi essential oil alone has a good antibacterial effect against Rhizopus stolonifer, the pathogen causing sweet potato soft rot, and exhibits a more significant synergistic effect when combined with clove essential oil. Considering the safety, pollution-free nature, and natural origin of both Artemisia argyi and clove essential oils, these results provide valuable technical guidance and practical significance for the harvesting and preservation of sweet potatoes and the post-harvest preservation of other crops. Attached Figure Description

[0010] Figure 1 To determine the antibacterial effect of Artemisia argyi essential oil on Rhizopus spp. using the growth rate method; Figure 2 The antibacterial effect of mugwort essential oil obtained through fumigation on sweet potatoes; Figure 3 The effect of different concentrations of Artemisia argyi essential oil on the cell membrane integrity of Rhizopus stolonifera; A in the figure is CK; B, C, D, E, F, and G are the results of 1300, 1400, 1500, 1600, 1700, and 1800 mg / L, respectively; Figure 4 The effect of different concentrations of Artemisia argyi essential oil on the cell membrane permeability of Rhizopus stolonifera; Figure 5 The results show the malondialdehyde (MDA) content determination in Rhizopus crepus. Figure 6 The results show the catalase content determination of Rhizopus stolonifera; Figure 7 The effect of different mass concentrations of clove essential oil on the antibacterial effect in sweet potato; Figure 8 The effect of the optimal blend ratio of Artemisia argyi and clove essential oil on sweet potato soft rot. Detailed Implementation

[0011] The present application will be further explained below with reference to the accompanying drawings and embodiments. Before introducing specific embodiments, the experimental materials and reagents involved in the following embodiments will be briefly described below. The mugwort leaves come from the mature leaves of 'Wan'ai' in Nanyang, Henan Province (the leaves are harvested from late May to late June, specifically the middle and upper leaves and tender stems).

[0012] Cloves are dried clove buds purchased from the Chinese medicine market; Rhizopus lanceolata, purchased from Henan Beina Biotechnology Testing and Inspection Co., Ltd.; Experimental sweet potato varieties such as Shang 19, Hami, and Xigua Hong were randomly purchased from farmers' markets. The relevant potato dextrose agar (PDA) and potato dextrose agar (PDB) media can be prepared using existing conventional techniques. Example 1

[0013] Given that existing research indicates that Artemisia argyi possesses broad-spectrum antibacterial properties, and considering the convenience and effectiveness of subsequent applications, this application primarily focuses on the experimental use of Artemisia argyi essential oil for the prevention and control of sweet potato soft rot. To facilitate subsequent evaluation of its application effects, this embodiment first briefly describes the preparation of Artemisia argyi essential oil as follows.

[0014] (I) Preparation of Artemisia argyi essential oil Artemisia argyi leaf essential oil was extracted using steam distillation; the specific extraction method is as follows: After drying, the mugwort leaves are crushed and soaked in water for 2 hours (mass ratio: mugwort leaves: water = 1:20). Then, the mixture is ultrasonically treated for 20 minutes. Subsequently, the soaked liquid is transferred to a distillation flask and distilled at 123°C for 6 hours. The fractions are collected, and the resulting product is mugwort essential oil.

[0015] (II) GC-MS Detection and Analysis For the Artemisia argyi essential oil prepared in step (I), take 10 μL of sample into a 10 mL volumetric flask and dilute to volume with anhydrous diethyl ether; for GC-MS detection and analysis, the chromatographic column used is an Agilent HP-5MS column (0.25 mm × 30 m, 0.25 μm), and the relative content of each chemical component is determined by the area normalization method; the specific detection parameters are as follows.

[0016] Inlet temperature 250℃; Temperature program: 70℃, hold for 10 min; increase to 95℃ at 10℃·min⁻¹, hold for 0 min; increase to 125℃ at 5℃·min⁻¹, hold for 0 min; increase to 240℃ at 6℃·min⁻¹, hold for 0 min; increase to 250℃ at 1℃·min⁻¹, hold for 0 min. Transmission line temperature 280℃; The carrier gas was high-purity helium, the flow rate was 1 mL·min⁻¹, and the injection volume was 1 uL. The ion source temperature is 200℃, the ionization source is E1, and the electron energy is 70eV; the quadrupole temperature is 150℃, and the scanning mass range is 20~450amu.

[0017] GC-MS analysis revealed 18 components in Artemisia argyi essential oil. The top seven main components were eucalyptol (26.15%), (1S,8aα)-decahydro-1,4aβ-dimethyl-7β-isopropenyl-1-naphthol (18.45%), 2-caryophyllene (13.14%), caryophyllene oxide (10.37%), camphor (8.00%), 1-caryophyllene (7.63%), and 4-terpene alcohol (7.17%). The top seven components with the highest content are shown in Table 1 below.

[0018] Table 1. Component analysis of Artemisia argyi essential oil Serial Number Peak time Relative content (%) Chinese name 1 9.254 26.15 Eucalyptol 2 25.987 18.45 (1S,8aα)-Decahydro-1,4aβ-dimethyl-7β-isopropenyl-1-naphthol 3 13.43 13.14 2-Ciol 4 24.213 10.37 Caryophyllene oxide 5 12.662 8.00 Camphor 6 20.193 7.63 1-Caryophyllene 7 13.721 7.17 4-Terpenol . The inventors further evaluated the specific control effects of the Artemisia argyi essential oil prepared in Example 1 on the pathogen Rhizopus spp. in vitro and in vivo. The specific experimental results are briefly described below. (I) Determination of in vitro antibacterial activity The growth rate method was used to determine and evaluate the antifungal activity of Artemisia argyi essential oil against Rhizopus creepingii. The specific determination method and results are briefly described below. (1) Growth rate method for determination First, take 50g of mugwort essential oil and dissolve it in 4% Tween-80 to prepare a 50g / L mugwort essential oil stock solution for later use.

[0019] Subsequently, PDA culture plates with Artemisia argyi essential oil concentrations (mass concentration, unit: mg / L) of CK (0 mg / L), 1300, 1400, 1500, 1600, 1700, and 1800 mg / L were prepared using the above mother liquor. Rhizopus stolonifera was inoculated onto the culture plates described above and then incubated at 28°C for approximately 36 hours. After the CK bacteria have fully grown on the plate, measure the colony diameter and calculate the inhibition rate using the following formula: Inhibition rate = (D1-D2) / D1×100%; In the formula: D1 is the colony growth diameter (cm) of the control group, and D2 is the colony growth diameter (cm) of the treatment group.

[0020] Specific results are as follows Figure 1 And as shown in Table 2 below.

[0021] Table 2. Inhibition rate of Rhizopus stolonifera by growth rate method Concentration (mg / L) CK 1300 1400 1500 1600 1700 1800 EC 50 ]]> Antibacterial rate 0% 17.3% 36.7% 53.3% 67.6% 87.9% 97% 1470mg / L The results above show that Artemisia argyi essential oil has a good antibacterial effect against Rhizopus creepingii, and this antibacterial effect is dose-dependent, with the inhibition rate increasing with increasing concentration of Artemisia argyi essential oil. In the growth rate method, EC... 50The value is 1470 mg / L. (2) Fumigation method for determination First, inoculate the center of the sterilized PDA culture plate with Rhizopus stolonifer; after inoculation, place the pre-sterilized filter paper into the petri dish lid; Subsequently, Artemisia argyi essential oil at concentrations of 1000, 2000, 4000, 6000, 8000, and 10000 mg / L was added to filter paper, respectively; a blank control group CK (0 mg / L) was set up at the same time. After the addition was completed, the plates were sealed and incubated at 28°C. The inhibition rate is calculated using the formula in the "Growth Rate Method".

[0022] The specific results are shown in Table 3 below.

[0023] Table 3. Inhibition rate of fumigation against Rhizopus cremastogyne Concentration (mg / L) CK 1000 2000 4000 6000 8000 10000 <![CDATA[EC 50 ]]> MIC Antibacterial rate 0% 15% 34.2% 56.7% 70.0% 93% 97% 3081mg / L 8000mg / L The results above show that Artemisia argyi essential oil has a good antibacterial effect against Rhizopus creepingii, and this antibacterial effect is dose-dependent, with the inhibition rate increasing with the concentration of Artemisia argyi essential oil. In the fumigation test, EC was measured... 50 The value was 3801 mg / L, and the minimum inhibitory concentration (MIC) was 8000 mg / L. This also indicates that the method of using mugwort essential oil directly affects the concentration used for antibacterial purposes. (II) In vivo antibacterial activity assay Wash the 'Watermelon Red' sweet potatoes (purchased randomly from the market), disinfect the surface with alcohol, cut them into pieces of similar size and thickness, and place 2 to 4 pieces into a petri dish with gauze at the bottom.

[0024] Mycelia were inoculated onto sweet potatoes (after the mycelia had covered the entire surface of the plate, holes were punched along the edge of the colony using a 6 mm diameter punch to collect mycelial cakes before inoculation). Different concentrations of Artemisia argyi essential oil (CK (0 mg / L), 1000, 2000, 4000, 6000, 8000, 10000 mg / L) were used. After fumigation, the plates were kept at a constant temperature of 28°C until the CK completely decomposed (approximately 3-4 days, during which time the surface of the sweet potatoes maintained 80-90% humidity). The in vivo antibacterial effects of different concentrations of Artemisia argyi essential oil were then observed and recorded. The results are as follows: Figure 2 As shown, the 10000 mg / L concentration had the best antibacterial effect, and Rhizopus cremastrae was basically in a dead state. (III) Cell morphology observation Based on the above results, the inventors conducted further cell morphology experiments to observe and analyze the mechanism of action of Artemisia argyi essential oil on the pathogen Rhizopus sylvestris. The specific experimental details are briefly described below. (1) Effects on cell membrane integrity After adding 10 μL of spore suspension to PDA, insert a sterilized coverslip at a 45° angle into the culture medium and incubate at 28°C for 24 h. Then, add Artemisia argyi essential oil to the culture dish (add CK (0 mg / L), 1300, 1400, 1500, 1600, 1700, and 1800 mg / L respectively).

[0025] After culturing for another 36 h, the coverslip was removed, washed twice with 0.1 mol / L phosphate buffer solution (PBS, pH 7.0), and then stained for 20 min with 5 mg / mL PI solution (dissolved in PBS) at room temperature in the dark. Finally, the mycelium was washed three times with PBS, the liquid on the slide was blotted dry with filter paper and washed three times with PBS, and then observed under a fluorescence microscope.

[0026] The results are as follows Figure 3 As shown, the red fluorescence gradually increases with the increase of the concentration of Artemisia argyi essential oil, while the control group shows no fluorescence at all. This indicates that as the concentration of Artemisia argyi essential oil increases, the integrity of the cell membrane of Rhizopus stolonifer is gradually damaged, and the higher the concentration of essential oil, the more severe the damage. (2) Effects of cell membrane permeability Artemisia argyi essential oil with final mass concentrations of CK (0 mg / L), 1300, 1400, 1500, 1600, 1700, and 1800 mg / L was added to PDB culture medium. The pathogen Rhizopus stolonifera (approximately 1 g of mycelium) was inoculated and cultured at a constant temperature of 28℃. Samples were taken at 0 h, 2 h, 4 h, 6 h, and 8 h of culture to measure conductivity.

[0027] The results are as follows Figure 4 As shown in the figure, the analysis reveals that the conductivity gradually increases with the increase of the concentration of Artemisia argyi essential oil. This result indicates that the permeability of the cell membrane is gradually damaged, and the damage worsens over time. (iv) Changes in relevant physiological indicators Add 10 μL of bacterial culture to 100 mL of PDB culture medium and incubate at 28 °C for 3 days. Then add Artemisia argyi essential oil (Artemisia argyi essential oil concentrations were CK (0 mg / L), 1300, 1400, 1500, 1600, 1700, and 1800 mg / L, respectively), and continue incubating at 28 °C for 3 days before taking samples for testing.

[0028] During the assay, the malondialdehyde and catalase content were determined using a malondialdehyde and catalase detection kit (a product of Suzhou Greens Biotechnology Co., Ltd.; please refer to the instruction manual for specific operation).

[0029] The measurement results are as follows Figure 5 , Figure 6 As shown. Analysis reveals that: Generally speaking, malondialdehyde (MDA) content is closely related to aging and stress damage in organisms. The results of this physiological indicator test show that as the concentration of Artemisia argyi essential oil increases, the MDA content increases. Based on this, it can be determined that Artemisia argyi essential oil can destroy the mycelium of creeping rhizomycetes and the damage is aggravated with increasing concentration. On the other hand, catalase (CAT) activity is generally considered to be related to the metabolic intensity and cold resistance and disease resistance of organisms. The results of the measurement of this physiological indicator show that as the concentration of Artemisia argyi essential oil increases, the catalase content decreases. Therefore, it can be concluded that Artemisia argyi essential oil can reduce the CAT content of Rhizopus stolonifera, causing oxidative stress, and the metabolic intensity of Rhizopus stolonifera is reduced under the action of Artemisia argyi essential oil. Example 3 Considering that some existing studies have reported the application of other plant extracts in the storage and anti-mold treatment of sweet potatoes, the inventors conducted a compounding experiment with clove essential oil, which is already used in the prior art, and the artemisia essential oil of this application to examine whether the two have a synergistic effect, thereby contributing to further improvements to the existing product. A brief summary of the specific experimental results is as follows.

[0030] Sweet potato varieties: Shangshu 19, Xiguahong, and Hami are all common sweet potato varieties with existing technology. The sweet potatoes used in the experiment were all harvested in 2024 and purchased randomly from the market. Experimental materials: clove flower buds (randomly purchased from a medicinal herb market); clove flower essential oil was extracted using steam distillation; the specific extraction method is as follows: After drying, the cloves are crushed and soaked in water for 2 hours (by mass ratio, cloves:water = 1:20). Then, the mixture is ultrasonically treated for 30 minutes. Subsequently, the soaked liquid is transferred to a distillation flask and distilled at 120°C for 6 hours. The fractions are collected, and the resulting product is clove essential oil. (I) GC-MS detection and analysis

[0031] For the clove essential oil prepared in step (I), take 10 μL of sample into a 10 mL volumetric flask and dilute to volume with anhydrous diethyl ether; for GC-MS detection and analysis, the chromatographic column used is an Agilent HP-5MS column (0.25 mm × 30 m, 0.25 μm), and the relative content of each chemical component is determined by the area normalization method; the specific detection parameters are as follows: Inlet temperature 250℃; transfer line temperature 280℃; The carrier gas is high-purity helium, with a flow rate of 1 mL·min⁻¹ and an injection volume of 1 uL; The ion source temperature is 200℃, the ionization source is E1, and the electron energy is 70eV; the quadrupole temperature is 150℃, and the scanning mass range is 20~450amu.

[0032] GC-MS analysis showed that the relative content of eugenol was 86.68%, the relative content of 1-caryophyllene was 11.22%, and the relative content of eugenol was 1.29%.

[0033] Table 4. Component analysis of clove essential oil Serial Number Peak time Relative content (%) Chinese name 1 18.4 86.68 Eugenol 2 20.1 11.22 1-Caryophyllene 3 21.1 1.29 Caryophyllene (ii) Application of clove essential oil alone Following the aforementioned procedures, the fumigation method was used to experimentally test the bactericidal effect of clove essential oil on Rhizopus cremastrae. The results are shown in Table 5 below.

[0034] Table 5. Antibacterial rate of different concentrations of clove essential oil against Rhizopus cremastrae determined by fumigation method Concentration (mg / L) 0 1000 2000 4000 6000 8000 10000 <![CDATA[EC 50 ]]> MIC Fumigation method antibacterial rate 0% 6.67% 33.3% 50% 80% 96.7% 100% 4000mg / L 8000mg / L The results in the table above show that clove essential oil alone also has a good antibacterial effect against Rhizopus creepingii, and this antibacterial effect is dose-dependent, with the inhibition rate increasing with increasing clove essential oil concentration. In the fumigation test, EC was measured... 50 The value was 4000 mg / L. The minimum inhibitory concentration (MIC) was 8000 mg / L. Furthermore, following the aforementioned procedures, an in vivo experiment was conducted to test the antibacterial effect of clove essential oil against Rhizopus stolonifer, and the results were as follows... Figure 7 As shown, the inhibitory effect gradually increases with the increase of clove essential oil concentration. When the clove essential oil concentration reaches 10000 mg / L, Rhizopus cremastrae is in a dead state. (III) Verification of Compound Combinations The checkerboard dilution method was used to screen the blends of Artemisia argyi and clove essential oils. Five levels were selected: 2x, 1x, 1 / 8, 1 / 4, and 1 / 2 of their respective minimum MICs. Each experiment was repeated three times. The combined MIC was calculated using the following formula: Is = [ρMICU(A) / ρMICS(A)] + [ρMICU(B) / ρMICS(B)];

[0035] In the formula: I S ρ is the Synergy Index (SI value); ρMICS is the MIC of the plant essential oil when used alone, in mg / L; ρMICU is the multiple of the MIC of the best antibacterial effect when the plant essential oil is compounded, in mg / L.

[0036] According to the determination method of SI, when SI ≤ 0.75, it shows a synergistic effect; when 0.75 < SI ≤ 1.00, it shows an additive effect; when SI > 2.00, it shows an antagonistic effect. The measurement results show that when 1 times the MIC value of Artemisia argyi essential oil is selected, the concentration of Artemisia argyi essential oil is 8000 mg / L, and 1 / 2 times the MIC value of Eugenia caryophyllata essential oil is selected, the concentration of Eugenia caryophyllata essential oil is 4000 mg / L. After the two are compounded, the value of the synergistic index SI is 0.575. For other dilution methods and compound combinations, the values of the synergistic index SI are all greater than 0.75. The results show that the combination of 8000 mg / L of Artemisia argyi essential oil and 4000 mg / L of Eugenia caryophyllata essential oil has a synergistic effect on inhibiting Rhizopus stolonifer.

[0037] According to the determination method of SI, when SI ≤ 0.75, it shows a synergistic effect; when 0.75 < SI ≤ 1.00, it shows an additive effect; when SI > 2.00, it shows an antagonistic effect. The measurement results show that when 1 times the MIC value of Artemisia argyi essential oil is selected, the concentration of Artemisia argyi essential oil is 8000 mg / L, and 1 / 2 times the MIC value of Eugenia caryophyllata essential oil is selected, the concentration of Eugenia caryophyllata essential oil is 4000 mg / L. After the two are compounded, the value of the synergistic index SI is 0.575. For other dilution methods and compound combinations, the values of the synergistic index SI are all greater than 0.75. The results show that the combination of 8000 mg / L of Artemisia argyi essential oil and 4000 mg / L of Eugenia caryophyllata essential oil has a synergistic effect on inhibiting Rhizopus stolonifer.

[0038] Before storing sweet potatoes, select the optimal concentration of the compound of Artemisia argyi essential oil (8000 mg / L) and Eugenia caryophyllata essential oil (4000 mg / L) with a synergistic inhibitory effect. After mixing 1000 mL of 8000 mg / L Artemisia argyi essential oil solution and 1000 mL of 4000 mg / L Eugenia caryophyllata essential oil with an ultrasonic atomization fumigator, put them into a cellar of about 2 tons of sweet potatoes in a 9-cubic-meter space, place them at 4 positions, and each position has 500 mL of essential oil complex. Conduct sealed fumigation. During storage, the temperature is kept at 10 - 15 °C and the humidity is kept at 80% - 90%. The rot rate is counted after 20 days, 30 days, and 35 days of storage, and a blank control group is set up at the same time.

[0039] The experimental results are as Figure 8 shown. It can be seen from the analysis that during the storage of sweet potatoes in the control group, the soft rot of sweet potatoes increased relatively fast with the extension of the storage period. During the storage of the group treated with the compound essential oil of Artemisia argyi and Eugenia caryophyllata, the increase rate of soft rot of sweet potatoes was inhibited with the extension of the storage period.

[0040] Example 4 On the basis of Example 3, considering reasons such as the cost and convenience of preventing soft rot, the inventor further compounded and applied Artemisia argyi essential oil with carbendazim, which is commonly used to prevent soft rot of sweet potatoes in the prior art, in different sweet potato varieties. The specific experimental situation is briefly introduced as follows.

[0041] Sweet potato varieties: Shangshu 19, Xiguahong, and Hami are all common sweet potato varieties with existing technology. The sweet potatoes used in the experiment were all harvested in 2024 and purchased randomly from the market. Experimental procedure: Before storing sweet potatoes, carbendazim (a product of Linyi Qingfengnian Agricultural Materials Co., Ltd., 98% wettable powder (0.5g / L)) and artemisia oil (6g / L) were mixed in different volume ratios (artemisia oil: carbendazim: = 10:0, 9:1, 7:3, 5:5, 3:7, 1:9, 0:10). The mixture was then sprayed onto the surface of the sweet potatoes. After spraying, the surface of the sweet potatoes was inoculated with soft rot pathogen (Rhizopus stolonifera). After spraying, the sweet potatoes were stored (storage conditions: temperature 10-15℃, humidity maintained at 75%-85%). The rot rate was counted after 45 days of storage. The specific statistical results are shown in Table 6 below.

[0042] Table 6. Inhibitory effect of mugwort essential oil combined with carbendazim on soft rot disease. Mugwort: Carbendazim 10:0 9:1 7:3 5:5 3:7 1:9 0:10 Inhibition rate of 19-potato gluten (%) 53.5±3.1 58.8±4.1 73.9±2.9 64.6±3.5 55.27±4.2 51.7±4.0 50.6±3.3 Watermelon red inhibition rate (%) 53.1±2.5 56.2±3.4 72.5±7.4 63.4±5.1 56.31±3.8 52.1±2.9 51.3±5.7 Hami inhibition rate (%) 54.0±4.91 57.5±2.2 75.9±3.8 64.7±3.7 57.49±5.5 55.3±3.9 52.8±4.0 Analysis of the results in the table above shows that, in practical applications, the effect of Artemisia argyi essential oil on the control of sweet potato soft rot is only slightly improved compared to the use of carbendazim alone. However, when the two are combined, especially in a 7:3 or 5:5 ratio, the control effect on sweet potato soft rot is significantly improved, indicating a clear synergistic effect. Based on this result, it can also provide a good technical reference for reducing the amount of chemical agents used in the control of soft rot in existing technologies.

Claims

1. The application of Artemisia argyi essential oil in the prevention and control of sweet potato soft rot, characterized in that, The sweet potato soft rot disease mentioned is caused by Rhizopus spp.

2. The application of Artemisia argyi essential oil as described in claim 1 in the prevention and control of sweet potato soft rot, characterized in that, The sweet potato varieties mentioned are: Shangshu 19, Xiguahong, or Hami.

3. The application of Artemisia argyi essential oil as described in claim 1 in the prevention and control of sweet potato soft rot, characterized in that, The mugwort essential oil is mugwort leaf essential oil prepared by steam distillation; the preparation method is as follows: After drying, the mugwort leaves are crushed and soaked in water. The ratio of mugwort leaves to water is 1:20 (g / mL) by mass. After soaking for 2 hours, the mixture is ultrasonically treated for 20 minutes. The soaked liquid is then transferred to a distillation flask and distilled at 123℃ for 6 hours. The fraction obtained is mugwort essential oil.

4. The application of Artemisia argyi essential oil as described in claim 1 in the prevention and control of sweet potato soft rot, characterized in that, When applying, mugwort essential oil and clove essential oil are blended together. When blending, the clove essential oil is at a concentration of 0.2~1.0g / L and the mugwort essential oil is at a concentration of 1~2g / L, with a volume ratio of clove essential oil: mugwort essential oil = 1~10:

1.

5. The application of Artemisia argyi essential oil as described in claim 4 in the prevention and control of sweet potato soft rot, characterized in that, The volume ratio is clove essential oil: artemisia essential oil = 9:1, 7:3, 5:5, 3:7 or 1:

9.

6. The application of Artemisia argyi essential oil as described in claim 4 in the prevention and control of sweet potato soft rot, characterized in that, The clove essential oil is prepared by steam distillation; the preparation method is as follows: After drying, the cloves are crushed and soaked in water for 2 hours. The ratio of mugwort leaves to water is 1:20 by mass. The mixture is then sonicated for 30 minutes. The soaked liquid is then transferred to a distillation flask and distilled at 120°C for 6 hours. The fractions are collected, and the resulting product is clove essential oil.

7. The application of Artemisia argyi essential oil as described in claim 1 in the prevention and control of sweet potato soft rot, characterized in that, When applying, mugwort essential oil is mixed with carbendazim. When mixing, carbendazim is at a concentration of 0.3~1.0g / L and mugwort essential oil is at a concentration of 4~8g / L. The volume ratio is mugwort essential oil: carbendazim = 0:10~10:

0.

8. The application of Artemisia argyi essential oil as described in claim 7 in the prevention and control of sweet potato soft rot, characterized in that, By volume ratio, the ratio of Artemisia argyi essential oil to carbendazim is 10:0, 9:1, 7:3, 5:5, 3:7, 1:9, and 0:10.

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