Composition against viral diseases and method for enhancing plant resistance to viral diseases

Abstract

The present invention discloses a composition for preventing and treating viral diseases and a method for improving the antiviral disease ability of plants. The active ingredients of the composition for preventing and treating viral diseases are brassinolide and chitosan, and the concentration ratio of the brassinolide to the chitosan is 1:40 to 60. When in use, the above composition for preventing and treating viral diseases is sprayed on the front and back sides of the plant leaves until water droplets form on the surface and naturally fall off. The present invention combines brassinolide and chitosan in a certain concentration ratio to form a composition. After spraying the composition on the leaves of passion fruit plants, it can significantly increase the resistance of passion fruit plants to viral disease pathogens, reduce the accumulation of viral pathogens, significantly induce the accumulation level of plant resistance-related substances and the occurrence of defense reactions, thereby effectively reducing the damage caused by pathogens to plants and better protecting the plants.

Description

Technical Field

[0001] The present invention belongs to the technical field of plant protection. Specifically, the present invention relates to a composition for preventing virus diseases and a method for improving the virus disease resistance of plants. Background Art

[0002] During the growth process, plants are often damaged by various stresses from the environment, and there are particularly many types of disease stresses, including various viral, fungal, and bacterial diseases. Among them, virus diseases are known as "plant cancers" and pose a great threat to plant growth. Once a plant is infected with a virus disease, it is basically incurable. In actual production, the prevention of plant virus diseases is mainly emphasized. At different growth stages of plants, the use of certain exogenous substances to induce or enhance the immunity and resistance of plants to pathogens is the main prevention and control strategy for plant virus diseases. Substances that can induce or improve the immune and resistance abilities of plants usually include some growth regulators and immune induction preparations, etc. By spraying or root-irrigating these substances, some important resistance reactions of plants can be induced, or the synthesis and secretion of plant resistance substances can be promoted, so as to enhance the resistance ability of plants to pathogenic factors in the environment and minimize the damage caused by these pathogens to plants.

[0003] Passiflora edulis, as a typical tropical and subtropical fruit, contains a variety of essential nutrients for the human body and is even known as the "fruit with a hundred fragrances", being deeply loved by consumers.

[0004] Known literature shows that currently, more than 40 viruses can infect Passiflora edulis in the world. Among them, Telosma mosaic virus (TeMV) of the genus Potyvirus in the family Potyviridae and Cucumber mosaic virus (CMV) of the genus Cucumovirus in the family Bromoviridae are the main pathogens causing virus diseases in Passiflora edulis.

[0005] Therefore, how to improve the resistance ability of such plants and effectively control the occurrence and spread of virus diseases is required for the development of the Passiflora edulis industry. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to provide a composition for preventing virus diseases, its preparation method, and a method for improving the virus disease resistance of plants. By using the composition of the present invention, the occurrence and spread of virus diseases can be effectively controlled, and the virus disease resistance ability of plants can be improved.

[0007] The specific technical solutions for achieving the above invention purposes are as follows.

[0008] In the first aspect of the present invention, a composition for preventing virus diseases is provided, and its active ingredients are brassinolide and chitosan, and the concentration ratio of brassinolide to chitosan is 1:40 - 60.

[0009] In the second aspect of the present invention, a preparation method of the above composition for preventing and treating virus diseases is provided, including the following steps: using ethanol with a concentration of 94% - 96% as a solvent to prepare a brassinolide mother liquor, and diluting it with distilled water to obtain a brassinolide solution; using glacial acetic acid with a concentration of 0.8% - 1.2% as a solvent to prepare a chitosan mother liquor, and diluting it with distilled water to obtain a chitosan solution; mixing the brassinolide solution and the chitosan solution to obtain the composition.

[0010] In the third aspect of the present invention, an application of the above composition for preventing and treating virus diseases in improving the virus disease resistance of plants is provided.

[0011] In the fourth aspect of the present invention, a method for improving the virus disease resistance of plants is provided, including the following steps: spraying the above composition for preventing and treating virus diseases on both the front and back sides of plant leaves until water droplets form on the surface and naturally fall off.

[0012] In the present invention, the inventors found that by compounding brassinolide and chitosan at a certain concentration ratio (1:40 - 60) to form a composition and spraying it on the leaves of passion fruit plants, the resistance of passion fruit plants to virus disease pathogens TeMV or CMV can be significantly increased, the accumulation of virus pathogens (TeMV or CMV) can be reduced, and the accumulation level of plant endogenous resistance-related substances and the occurrence of defense reactions can be significantly induced, thereby effectively reducing the damage caused by pathogens to plants and better protecting the plants.

[0013] The composition for preventing and treating virus diseases of the present invention has simple raw material components, easy operation methods, is green and pollution-free, has no pollution to the environment, and is non-toxic to the human body. It is expected to replace or reduce the use of chemical pesticides and fertilizers, thereby promoting the green and sustainable development of agricultural production. Description of the Drawings

[0014] Figure 1 It shows the disease symptoms of passion fruit leaves under different treatments in Test Example 1 of the present invention; among them, CK is the healthy control group; TeMV is pretreatment with distilled water + TeMV; BR + TeMV is pretreatment with 0.4 mg / L BR + TeMV; CTS + TeMV is pretreatment with 20 mg / L CTS + TeMV; BR + CTS + TeMV is pretreatment with 0.4 mg / L BR + 20 mg / L CTS + TeMV.

[0015] Figure 2 It shows the detection results of the virus content in the diseased leaves of passion fruit under different treatments in Test Example 1 of the present invention.

[0016] Figure 3 It shows the results of the relative conductivity (a), malondialdehyde (b), and H2O2 (c) contents in the leaves of passion fruit under different treatments in Test Example 1 of the present invention.

[0017] Figure 4 Results of total chloroplast content (a), stomatal conductance (b), transpiration rate (c), and net CO2 assimilation (d) in passion fruit leaves under different treatments in Test Example 1 of the present invention.

[0018] Figure 5 Results of the contents of soluble sugar (a) and proline (b) in passion fruit leaves under different treatments in Test Example 1 of the present invention.

[0019] Figure 6 Results of the activities of antioxidant-related enzymes in passion fruit leaves under different treatments in Test Example 1 of the present invention.

[0020] Figure 7 Results of the resistance of passion fruit plants to the infection of Telosma mosaic virus TeMV by brassinolide and chitosan at different concentration ratios in Test Example 2 of the present invention.

[0021] Figure 8 Results of the resistance of passion fruit plants to the infection of Cucumber mosaic virus CMV by the antiviral composition in Test Example 3 of the present invention. Detailed implementation manners

[0022] For ease of understanding the present invention, the present invention will be described more comprehensively below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosed content of the present invention more thorough and comprehensive.

[0023] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments and are not used to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0024] If not specifically specified, the embodiments are carried out under conventional experimental conditions or according to the conditions recommended in the manufacturer's instructions. The raw materials and reagents used in the present invention are commercially available, and any biological germplasm materials can be provided for scientific research externally.

[0025] In the present invention, brassinolide and chitosan with a concentration ratio of 1:40 - 60 are compounded to form a composition. After spraying the composition on the leaves of passion fruit plants, it can reduce the symptoms and the accumulation amount of pathogens of passion fruit plants under the stress of virus disease (TeMV), reduce the damage to plant cells caused by virus infection (the content of relative conductivity, malondialdehyde and H2O2 decreases), relieve the photosynthetic damage to the leaves of the plants caused by virus infection (the content of total chlorophyll, stomatal conductance, transpiration rate and net CO2 assimilation), induce the content of secondary metabolites related to resistance (such as soluble sugar and proline) in the leaves of passion fruit plants, and increase the activities of plant endogenous antioxidant-related enzymes (ascorbate peroxidase, superoxide dismutase, catalase and peroxidase), so as to effectively reduce the damage caused by pathogens to the plants and better protect the plants.

[0026] In some embodiments of the present invention, an antiviral disease composition is disclosed, the active ingredients of which are brassinolide and chitosan, and the concentration ratio of the brassinolide and chitosan is 1:40 - 60.

[0027] In some embodiments, the concentration ratio of the brassinolide and chitosan is 1:45 - 55.

[0028] In some embodiments, the concentration ratio of the brassinolide and chitosan is 1:48 - 52.

[0029] In some embodiments, in the composition, the concentration of brassinolide is 0.4 mg / L, and the concentration of chitosan is 20 mg / L.

[0030] In some embodiments, the pathogen of the virus disease is the tuberose mosaic virus or the cucumber mosaic virus.

[0031] In some other embodiments of the present invention, a preparation method of the above antiviral disease composition is disclosed, which includes the following steps: using 94% - 96% ethanol as a solvent to prepare a brassinolide mother liquor, and diluting it with distilled water to obtain a brassinolide solution; using 0.8% - 1.2% glacial acetic acid as a solvent to prepare a chitosan mother liquor, and diluting it with distilled water to obtain a chitosan solution; mixing the brassinolide solution and the chitosan solution to obtain the composition; the concentration ratio of the brassinolide solution and the chitosan solution is 1:40 - 60.

[0032] In some other embodiments of the present invention, the application of the above composition in improving plant antiviral disease is disclosed.

[0033] In some embodiments, the plant is passion fruit; and / or, the pathogen of the virus disease is the tuberose mosaic virus or the cucumber mosaic virus.

[0034] In some other embodiments of the present invention, a method for enhancing the antiviral disease resistance of plants is disclosed, which includes the following steps: spraying the above composition on both the front and back sides of the plant leaves until water droplets form on the surface and naturally fall off.

[0035] In some of these embodiments, the number of sprayings is 3 to 5 times.

[0036] In the following examples, the reagents or raw materials used include: brassinolide BR (purity ≥ 90%, Solarbio, using 95% ethanol as the solvent to prepare the BR stock solution, and diluting it with distilled water to the concentration required for the experiment when in use), chitosan CTS (purity ≥ 98%, Solarbio, using 1% glacial acetic acid as the solvent to prepare the CTS stock solution, and diluting it with distilled water to the concentration required for the experiment when in use), passion fruit seedlings (cultivated from the golden passion fruit seeds self-preserved in the applicant's laboratory, the fruits were purchased from the passion fruit digital orchard in Dapu County, Meizhou City, Guangdong Province. After collecting the fruit seeds, they were naturally air-dried and then stored in the laboratory for a series of basic scientific research), pathogen TeMV, CMV (virus sources self-preserved in the applicant's laboratory).

[0037] The following will specifically describe the present invention in conjunction with the accompanying drawings and specific examples.

[0038] Example 1 An antiviral disease composition and its preparation method

[0039] The effective components of the antiviral disease composition in this example are 0.4 mg / L of brassinolide and 20 mg / L of chitosan.

[0040] The preparation method of the antiviral disease composition in this example includes the following steps: using 95% ethanol as the solvent to prepare the brassinolide stock solution, and diluting it with distilled water to obtain a 0.4 mg / L brassinolide solution; using 1% glacial acetic acid as the solvent to prepare the chitosan stock solution, and diluting it with distilled water to obtain a 20 mg / L chitosan solution; mixing the brassinolide solution and the chitosan solution in a volume ratio of 1:1 to obtain the product.

[0041] The usage method of the antiviral disease composition in this example is: spraying the above composition on both the front and back sides of the plant leaves until water droplets form on the surface and naturally fall off, spraying once every two days, for 4 times.

[0042] Example 2 An antiviral disease composition and its preparation method

[0043] The effective components of the antiviral disease composition in this example are 0.4 mg / L of brassinolide and 16 mg / L of chitosan.

[0044] The preparation method of the anti-virus disease composition in this embodiment includes the following steps: using 95% ethanol as a solvent, preparing a brassinolide stock solution, and diluting it with distilled water to obtain a 0.4 mg / L brassinolide solution; using 1% glacial acetic acid as a solvent, preparing a chitosan stock solution, and diluting it with distilled water to obtain a 16 mg / L chitosan solution; mixing the brassinolide solution and the chitosan solution in a volume ratio of 1:1, thus obtaining the composition.

[0045] The usage method of the anti-virus disease composition in this embodiment is the same as that in Example 1.

[0046] Example 3 An anti-virus disease composition and its preparation method

[0047] The effective components of the anti-virus disease composition in this embodiment are 0.4 mg / L brassinolide and 24 mg / L chitosan.

[0048] The preparation method of the anti-virus disease composition in this embodiment includes the following steps: using 95% ethanol as a solvent, preparing a brassinolide stock solution, and diluting it with distilled water to obtain a 0.4 mg / L brassinolide solution; using 1% glacial acetic acid as a solvent, preparing a chitosan stock solution, and diluting it with distilled water to obtain a 24 mg / L chitosan solution; mixing the brassinolide solution and the chitosan solution in a volume ratio of 1:1, thus obtaining the composition.

[0049] The usage method of the anti-virus disease composition in this embodiment is the same as that in Example 1.

[0050] Comparative Example 1 An anti-virus disease composition and its preparation method

[0051] The effective components of the anti-virus disease composition in this comparative example are 0.4 mg / L brassinolide and 10 mg / L chitosan. The preparation method of the anti-virus disease composition in this comparative example is the same as that in Example 1.

[0052] Comparative Example 2 An anti-virus disease composition and its preparation method

[0053] The effective components of the anti-virus disease composition in this comparative example are 0.4 mg / L brassinolide and 40 mg / L chitosan. The preparation method of the anti-virus disease composition in this comparative example is the same as that in Example 1.

[0054] Test Example 1 The composition of the present invention improves the resistance of passion fruit to virus diseases

[0055] This test example verifies that the composition of the present invention can improve the resistance of passion fruit to virus diseases, including the following steps:

[0056] 1. In a plant light incubator (light density is 100 μM m -2 s -1, 16-h light / 8-h dark cycle, average temperature 27 °C), passion fruits were planted using soil cultivation method. After the plants grew to 4-5 leaves, they were used for subsequent experiments;

[0057] 2. Spray the leaves of the plants with 0.4 mg / L BR, 20 mg / L CTS, 0.4 mg / L BR + 20 mg / L CTS (volume ratio 1:1) respectively, and the control group was sprayed with distilled water. For foliar spraying, spray both the front and back of the leaves until water droplets naturally fall on the surface to ensure sufficient and uniform spraying. The first spraying treatment was at 8 am in the morning, and the second spraying was carried out after 48 hours. The total number of spraying times was 4 times;

[0058] 3. On the 9th day, the leaves of the plants in each group were inoculated with the virus TeMV by mechanical friction inoculation;

[0059] 4. Observe the disease development of the plants in each group and carry out relevant detections. The detection indicators mainly include the accumulation of pathogens, as well as some physiological and biochemical indicators closely related to the plant's response to pathogen infection.

[0060] (1) Disease symptoms of passion fruit leaves

[0061] The results of the disease symptoms of passion fruit leaves under different treatments are as Figure 1 shown. It can be seen from Figure 1 that compared with the healthy control group (CK) without virus and reagent treatment, after the leaves of passion fruit were infected with the virus (TeMV) alone, the leaves were severely wrinkled and showed mosaic. Compared with the single TeMV inoculation, the wrinkling and mosaic symptoms of the leaves of passion fruit pretreated with 0.4 mg / L BR + TeMV (BR + TeMV), 20 mg / L CTS + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS + TeMV (BR + CTS + TeMV) were significantly reduced, and only slight wrinkling and a little mosaic appeared near the veins. It shows that pretreatment of passion fruit seedlings with 0.4 mg / L BR, 20 mg / L CTS, and 0.4 mg / L BR + 20 mg / L CTS can effectively inhibit the development of TeMV on passion fruit plants, effectively reduce the damage of virus infection to the plants, and improve the resistance of the plants to the virus. Among them, the combined treatment of 0.4 mg / L BR + 20 mg / L CTS can further improve this inhibitory effect, and the symptoms of the plant leaves are the lightest, and the control effect on the occurrence of virus diseases on passion fruit plants is the most significant.

[0062] (2) Pathogen accumulation

[0063] The accumulation of pathogens in the leaves was detected by enzyme-linked immunosorbent assay, and the results are as Figure 2As shown in the figure, the results showed that compared with the treatment of TeMV alone, the virus content in the treatment groups of 0.4 mg / L BR pretreatment + TeMV (BR + TeMV), 20 mg / L CTS pretreatment + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) was significantly reduced, and the virus content in the treatment group of 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) was the lowest. This result was consistent with the disease symptom results of passion fruit leaves.

[0064] (3), Contents of relative electrical conductivity, malondialdehyde and H2O2

[0065] Under stress environments, plant cells are often severely damaged, and the relative electrical conductivity and the content of malondialdehyde (MDA) are often used as indicators reflecting the degree of damage to plant cells under stress environments. The content of H2O2 can be used to characterize the degree of oxidative damage suffered by plant cells under stress environments.

[0066] The results are as Figure 3 shown.

[0067] The results showed that the treatment groups of 0.4 mg / L BR pretreatment + TeMV (BR + TeMV), 20 mg / L CTS pretreatment + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) could all significantly reduce the damage to plant cells caused by pathogen infection. Among them, in the treatment group of 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV), the degree of such cell damage caused by virus infection was the lowest. After TeMV infection, the accumulation of relative electrical conductivity and MDA content was the lowest (see Figure 3 a and b in it).

[0068] The treatment groups of 0.4 mg / L BR pretreatment + TeMV (BR + TeMV), 20 mg / L CTS pretreatment + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) could all reduce the accumulation of endogenous H2O2 content in plants caused by pathogen infection. Among them, the treatment group of 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) could further reduce the accumulation of H2O2 content caused by virus infection and reduce the oxidative damage of plant cells caused by virus invasion (see Figure 3 c in it).

[0069] (4), Total chloroplast content, stomatal conductance, transpiration rate and net CO2 assimilation

[0070] Photosynthesis is one of the most important life activities of plants, and chlorophyll is the most important pigment closely related to plant photosynthesis. Usually, the infection of pathogens will affect the photosynthesis of plants, and thus affect the growth of plants. Considering that the stomatal conductance, transpiration rate and net CO2 assimilation rate of plant leaves are also physiological indicators closely related to photosynthesis, they were also detected and analyzed.

[0071] The results of the total chloroplast content, stomatal conductance, transpiration rate and net CO2 assimilation in passion fruit leaves under different treatments are as Figure 4 shown.

[0072] The results showed that compared with the virus inoculation control group (TeMV-), the chlorophyll content decreased in all virus treatment groups. Compared with the distilled water treatment group (CK), the 0.4 mg / L BR pretreatment + TeMV (BR + TeMV), 20 mg / L CTS pretreatment + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) treatment groups could significantly alleviate the decrease in chlorophyll content in plant leaves caused by virus infection (see Figure 4 a) in it).

[0073] TeMV infection significantly reduced the stomatal conductance, transpiration rate and net CO2 assimilation of plant leaves. However, 0.4 mg / L BR pretreatment + TeMV (BR + TeMV), 20 mg / L CTS pretreatment + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) could significantly alleviate the decrease in stomatal conductance, transpiration rate and net CO2 assimilation caused by virus infection ( Figure 4 b-d) in it). Among them, the 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) composite treatment group had the best effect and could minimize the impact of virus infection on the photosynthetic performance of plant leaves. This may indicate that BR + CTS enables plants to produce more energy and nutrients through photosynthesis by protecting the plant photosynthetic system, and then supplies them for growth and synthesis of more compounds to resist environmental stress.

[0074] (5) Content of soluble sugar and proline

[0075] When plants face environmental stress, they will initiate their own defense-related responses. For example, they will synthesize some secondary metabolites related to stress resistance to improve their resistance ability. Among them, soluble sugars and proline play important roles in the plant's resistance response. For instance, soluble sugars, on the one hand, act as osmotic regulators, and on the other hand, they also serve as protectants for enzymes and cell structures. In addition to acting as an osmotic regulator, proline also plays a very important role in maintaining the integrity of the cell membrane structure and eliminating the excessive accumulation of ammonia in plants. Generally speaking, the higher the content of soluble sugars and proline, the stronger the plant's stress resistance.

[0076] The results of the contents of soluble sugars and proline in passion fruit leaves under different treatments are as Figure 5 shown. The results show that after the plants were infected with TeMV, the contents of both soluble sugars and proline increased significantly. Among them, compared with the CK group, the contents of soluble sugars and proline in the three groups of 0.4 mg / L BR pretreatment + TeMV (BR + TeMV), 20 mg / L CTS pretreatment + TeMV (CTS + TeMV), and 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV) increased significantly, and the content increased the most after the combined treatment of 0.4 mg / L BR + 20 mg / L CTS pretreatment + TeMV (BR + CTS + TeMV). This indicates that exogenous application of BR and CTS may improve the plant's resistance to pathogens by promoting the synthesis of resistance substances such as soluble sugars and proline in plants.

[0077] (6) Activity of antioxidant-related enzymes

[0078] The antioxidant enzyme system is an important defense-related factor in the process of plants responding to pathogen infection and is often positively correlated with the plant's resistance ability.

[0079] The results of the activities of antioxidant-related enzymes in passion fruit leaves under different treatments are as Figure 6 shown. Figure 6The results showed that compared with the CK group, the three treatments of 0.4mg / LBR pretreatment + TeMV (BR+TeMV), 20mg / L CTS pretreatment + TeMV (CTS+TeMV), and 0.4mg / LBR+20mg / L CTS pretreatment + TeMV (BR+CTS+TeMV) significantly increased the activities of antioxidant-related enzymes in passion fruit plants after responding to TeMV, including ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Among them, the 0.4mg / LBR+20mg / L CTS pretreatment + TeMV (BR+CTS+TeMV) composite treatment had the highest increase in the activities of these four antioxidant enzymes in plant leaves. This shows that the induction of plant resistance by BR and CTS is closely related to their ability to increase the activity of endogenous antioxidant-related enzymes in plants, and this induction ability is enhanced in the BR+CTS composite treatment, thereby effectively improving the resistance of plants to pathogens. In addition, the test results also show that in the TeMV-treated group, that is, in the absence of pathogen infection, the three pretreatments of 0.4mg / LBR pretreatment + TeMV (BR+TeMV), 20mg / L CTS pretreatment + TeMV (CTS+TeMV), and 0.4mg / LBR+20mg / LCTS pretreatment + TeMV (BR+CTS+TeMV) can also induce the increase of antioxidant enzyme activity in plant leaves to varying degrees. The induction level was the highest in the BR+CTS composite treatment group, which further shows that these two substances have an additive effect on the induction of plant resistance.

[0080] In summary, this test case used the method of foliar spraying to study the effects of BR, CTS, and BR+CTS combined application on the resistance induction and defense against virus disease stress in passion fruit plants. The analysis results showed that the single and combined application of BR and CTS can increase the resistance of passion fruit plants to viruses, reduce the symptoms and accumulation of pathogens in passion fruit plants under virus disease stress, reduce the damage of virus infection to plant leaves, alleviate the photosynthetic damage of virus infection to plant leaves, and induce the content of secondary metabolites related to resistance in passion fruit plant leaves. Compared with the use of BR and CTS alone, the combined application of BR+CTS has a more obvious induction effect on plant resistance, the mildest symptom, and more significantly reduces the effects of pathogen invasion on plant leaf chlorophyll content, stomatal conductance and transpiration rate, and resistance-related metabolites such as soluble sugar and proline content, and the activity of antioxidant-related enzymes are further improved. The combined application of BR+CTS can better protect plants, improve their resistance and reduce the damage of pathogens to plants.

[0081] Experimental Example 2 Effect of the Concentration Ratio of Brassinolide and Chitosan on the Inhibitory Effect of Pathogen TeMV

[0082] This test example investigated the inhibitory effects of different concentration ratios of brassinolide and chitosan on the pathogen TeMV, including the following steps:

[0083] 1. In a plant light incubator (light density of 100 μM m -2 s -1 , 16-h light / 8-h dark cycle, average temperature of 27 °C), passion fruits were planted using soil culture. After the plants grew to 4 - 5 leaves, they were used for subsequent experiments;

[0084] 2. The compositions of Example 1, Comparative Example 1, and Comparative Example 2 were respectively used to spray the leaves of the plants, and the control group was treated with distilled water spraying. For foliar spraying, the front and back sides of the leaves were sprayed until water droplets naturally fell on the surface to ensure sufficient and uniform spraying. The first spraying treatment was at 8 am in the morning, and the second spraying was carried out after 48 hours. The total number of spraying times was 4 times;

[0085] 3. On the 9th day, the virus TeMV was inoculated on the leaves of each group of plants by mechanical friction inoculation;

[0086] 4. Observe the disease symptom phenotypes of the leaves of each group of plants, and the results are as Figure 7 shown. As Figure 7 can be seen, after the leaves of passion fruits were infected by the virus (TeMV) alone, the leaves were severely wrinkled and showed mosaic ( Figure 7 a in). Treating the leaves with compositions of brassinolide and chitosan at different concentration ratios could inhibit the occurrence of the disease. Compared with the compositions of Comparative Example 1 and Comparative Example 2 ( Figure 7 b and d in), the composition of Example 1 (the concentration ratio of brassinolide and chitosan is 1:50) had the most obvious inhibitory effect on the pathogen, and the disease symptom phenotype was the mildest ( Figure 7 c in).

[0087] Test Example 3 Inhibitory effect of the composition of the present invention on the pathogen CMV

[0088] This test example investigated the inhibitory effect of the composition of Example 1 of the present invention on the pathogen CMV, including the following steps:

[0089] 1. In a plant light incubator (light density of 100 μM m -2 s -1 , 16-h light / 8-h dark cycle, average temperature of 27 °C), passion fruits were planted using soil culture. After the plants grew to 4 - 5 leaves, they were used for subsequent experiments;

[0090] 2. Spray the leaves of the plants with the composition of Example 1 and distilled water respectively. For foliar spraying, spray both the front and back sides of the leaves until water droplets form on the surface and fall naturally, ensuring sufficient and uniform spraying. The first spraying treatment is carried out at 8:00 in the morning, the second spraying is carried out after an interval of 48 hours, and the total number of spraying times is 4 times;

[0091] 3. On the 9th day, inoculate the virus CMV on the leaves of each group of plants by mechanical friction inoculation;

[0092] 4. Observe the disease phenotypes of the leaves of each group of plants, and the results are as Figure 8 shown. It can be seen from Figure 8 that compared with the healthy control group (CK) without virus and reagent treatment, after the leaves of passion fruit are infected with the virus (CMV) alone, the leaves are severely wrinkled and show mosaic. After treating the leaves with the composition of Example 1, the wrinkling and mosaic symptoms of passion fruit leaves are significantly reduced. It shows that the antiviral composition of the present invention can significantly inhibit the occurrence of CMV virus disease on passion fruit plants.

[0093] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0094] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. An antiviral composition, characterized in that, Its active ingredients are brassinolide and chitosan, and the concentration ratio of brassinolide to chitosan is 1:40 - 60.

2. The antiviral composition according to claim 1, characterized in that, The concentration ratio of brassinolide to chitosan is 1:45 - 55.

3. The antiviral composition according to claim 2, characterized in that, The concentration ratio of brassinolide to chitosan is 1:48 - 52.

4. The antiviral composition according to claim 3, characterized in that, In the composition, the concentration of brassinolide is 0.4 mg / L, and the concentration of chitosan is 20 mg / L.

5. A method for preparing the antiviral composition according to any one of claims 1 to 4, characterized in that, It includes the following steps: using 94% - 96% ethanol as the solvent to prepare the brassinolide stock solution, and diluting it with distilled water to obtain the brassinolide solution; using 0.8% - 1.2% glacial acetic acid as the solvent to prepare the chitosan stock solution, and diluting it with distilled water to obtain the chitosan solution; mixing the brassinolide solution and the chitosan solution to obtain the product.

6. The application of the composition according to any one of claims 1 - 4 in enhancing plant antiviral disease; the pathogen of the viral disease is the tuberose mosaic virus.

7. A method for enhancing a plant's resistance to viral diseases, characterized in that, It includes the following steps: Spraying the composition according to any one of claims 1 - 4 on the front and back sides of the plant leaves until water droplets naturally fall from the surface. The pathogen of the viral disease is the tuberose mosaic virus.

8. The method for improving plant antiviral disease according to claim 7, wherein The number of spraying times is 3 - 5 times.

9. The method for enhancing plant antiviral disease according to claim 7, characterized in that, The plant is passion fruit.

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