Complex microbial inoculant and application thereof in prevention and treatment of citrus diseases and postharvest preservation

Abstract

The invention discloses a complex microbial inoculant and application of the complex microbial inoculant in prevention and treatment of citrus diseases and postharvest preservation. The complex microbial inoculant provided by the invention contains purpureocillium lilacinum and curcumin, and can effectively prevent and treat orange diseases and fungal diseases after fruit picking; when curcumin is independently used, no bacteriostatic effect is achieved, after the purpureocillium lilacinum and curcumin are compounded, the inhibiting effect of the purpureocillium lilacinum on citrus canker germs, penicillium italicum and penicillium digitatum can be further enhanced, and the synergistic interaction effect is achieved. Meanwhile, the composite microbial agent can prolong the refreshing time of the picked oranges and reduce the morbidity of green mold and green mold of the picked oranges, has preservative and fresh-keeping effects, is applied to the storage and transportation of the picked oranges as a preservative or preservative, not only widens the application of the purpureocillium lilacinum, but also improves the preservation effect after the purpureocillium lilacinum is combined with curcumin. Citrus diseases can be better prevented and treated, postharvest preservation of fruits can be better achieved, and more methods and products are provided for citrus planting and postharvest disease prevention and treatment.

Description

Technical Field

[0001] The present invention belongs to the technical field of microbial control, and more specifically, relates to a composite bacterial agent and its application in preventing and controlling citrus diseases and preserving citrus fruits after harvest. Background Art

[0002] Diseases of varying degrees will occur throughout the growth and cultivation process of citrus, and their severity cannot be ignored. They have a significant impact on the growth of citrus trees and the quality and yield of fruits. Among them, citrus canker is caused by Xanthomonas citri subsp.citri (Xcc), which is one of the most important bacterial diseases in the citrus cultivation process. When the disease occurs, it will cause citrus leaf and fruit drop, and corky spots on the fruit, which seriously affects the yield and quality of citrus. During the storage and transportation of citrus fruits after harvest, they are often infected by some fungi and cause rot, which can reach up to 50%. Among them, penicillium caused by Penicillium italicum and green mold caused by Penicillium digitatum are the main causes of citrus rot.

[0003] At present, the most important means to control citrus post-harvest infectious diseases is to use chemical fungicides, such as carbendazim, methyl thiophanate, thiabendazim, imazalil, prochloraz, etc. However, long-term and large-scale use of fungicides will cause pathogens to develop drug resistance, reduce control effects, exceed pesticide residues, endanger human and animal health, and pollute the environment. Therefore, it is very necessary to seek a new control method that is safe, efficient, and can replace or reduce the use of chemical fungicides.

[0004] With the development of biological control agents, more and more plant diseases can be controlled by microbial preparations. Among them, biocontrol bacteria have the advantages of not polluting the environment, being non-toxic to humans and animals, and having no side effects on plants, avoiding the environmental pollution and ecological damage that chemical pesticides may bring; and it is highly targeted and can effectively deal with soil-borne diseases. The use of biocontrol bacteria helps to maintain ecological balance and promote soil health, thereby providing a more favorable environment for plant growth. However, the control effect of existing biocontrol bacteria is generally not as significant as that of chemical pesticides, and the control effect is very limited by environmental conditions. For example, existing studies have shown that Purpureocillium lilacinum can inhibit Penicillium digitatum, but it has not been used for the control of Penicillium italicum and citrus canker, and its control effect needs to be improved. At present, there is an urgent need to improve the control effect of biocontrol bacteria and provide more products or methods for the control of citrus canker, citrus penicillium and citrus green mold. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the poor control effect of existing biocontrol bacteria and the shortcomings of products and methods for controlling citrus diseases, and to provide a composite bacterial agent and its application in controlling citrus diseases and post-harvest preservation.

[0006] The first object of the present invention is to provide the application of Pseudomonas lilacinus.

[0007] The second object of the present invention is to provide a composite bacterial agent.

[0008] The third object of the present invention is to provide a composition for preventing and controlling citrus diseases or preserving citrus after harvest.

[0009] The fourth object of the present invention is to provide an application of the composite bacterial agent or composition.

[0010] The fifth object of the present invention is to provide a method for preventing and controlling citrus diseases or preserving citrus after harvest.

[0011] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0012] The invention provides use of Purpurosporium lilacinum in inhibiting Xanthomonas citri subspecies citri and / or Penicillium italium, or use of Purpurosporium lilacinum in preparing an antibacterial agent for inhibiting Xanthomonas citri subspecies citri and / or Penicillium italium.

[0013] The present invention shows that P. lilacinus can inhibit Xanthomonas citri subsp. citri, Penicillium italicum and Penicillium digitatum. Curcumin alone has no inhibitory effect on these fungi. However, the combination of P. lilacinus and curcumin can significantly enhance the antibacterial effect of P. lilacinus, and the antibacterial rates are increased to 3.7%, 13.6% and 14.5% respectively, which has a synergistic effect. Therefore, the composite bacterial agent prepared by combining Pseudomonas aeruginosa and curcumin can be used as an environmentally friendly green agent to replace chemical fungicides, and can be used for the prevention and control of citrus canker during citrus cultivation and the prevention and control of citrus fruit green and green mold after harvest. It not only broadens the application of Pseudomonas aeruginosa, but can also be better used in citrus disease prevention and control when combined with curcumin. It also provides more methods and products for citrus cultivation and post-harvest disease prevention and control as well as preservation, and has wide application value.

[0014] The invention provides the use of Purpurosporium lilacinum in inhibiting Penicillium digitatum and simultaneously inhibiting Xanthomonas citri subspecies citri and / or Penicillium italicum.

[0015] The invention provides a composite bacterial agent containing Pseudomonas lilacinus and curcumin.

[0016] In particular, the Pseudomonas lilacinus and curcumin in the composite bacterial agent are separately packaged products, and the Pseudomonas lilacinus contained therein needs to be fermented before being mixed with curcumin for use.

[0017] The invention provides a composition for preventing and treating citrus diseases or preserving citrus after harvest, which contains fermentation liquid or fermentation supernatant of Pseudomonas lilacinus and curcumin.

[0018] Furthermore, the fermentation liquid is obtained by fermentation of Pseudomonas lilacinus.

[0019] Furthermore, the fermentation supernatant is obtained by removing the bacterial cells from the fermentation liquid.

[0020] Preferably, the material-liquid ratio of curcumin: fermentation broth or fermentation supernatant is (10-30) mg: (80-150) mL.

[0021] Preferably, the material-liquid ratio of curcumin: fermentation broth or fermentation supernatant is 25 mg:100 mL.

[0022] As the most preferred embodiment, the present invention provides a method for preparing a fermentation supernatant: activating and culturing the purpurogenous spores of the purpurogenous spores in a PDA medium for 7 days, washing the spores of the purpurogenous spores from the PDA plate with 100 mL of sterile water, and diluting the spore solution to a concentration of 1.0×10 7 cfu / mL. After drying the lemon leaves at 60°C, crush them with a grinder and pass through a 40-mesh sieve. Add rove beetle powder to prepare a solid culture medium. Dispense the prepared solid culture medium into tissue culture bottles, cover them with filter caps, and sterilize them at high temperature and high pressure for 1 hour. Take another 15mL of spore liquid, add it to the tissue culture bottle, and culture it at 28°C for 7 days. Then use 75% ethanol to extract the solid culture medium cultured for 7 days at a ratio of 2:1 for 24 hours to obtain the fermentation liquid, centrifuge to obtain the supernatant, vacuum filter and concentrate, and filter and sterilize with a 0.22μm microporous filter membrane to obtain the active crude extract of Pseudomonas lilacinus, which is the fermentation supernatant.

[0023] The present invention provides the use of the above-mentioned composite bacterial agent or composition in inhibiting any one, any two or three of Xanthomonas citri subspecies citrus, Penicillium italium and Penicillium digitatum, or in the preparation of an antibacterial agent for inhibiting any one, any two or three of Xanthomonas citri subspecies citrus, Penicillium italium and Penicillium digitatum.

[0024] The present invention provides the use of the composite bacterial agent or composition in preventing and controlling citrus diseases, or in preparing citrus disease prevention and control products.

[0025] Furthermore, the citrus disease is citrus canker, citrus penicillium and / or citrus green mold.

[0026] At the same time, studies have shown that the above-mentioned composite bacterial agents or compositions can effectively slow down the loss of water and nutrients in post-harvest fruits, reduce the incidence of green and green mold diseases in sugar oranges after harvest, extend the shelf life of citrus after harvest, have good preservative and fresh-keeping effects, and can also be used as preservatives and antiseptics in the post-harvest preservation of citrus.

[0027] The present invention provides the use of the composite bacterial agent or the composition in preserving citrus after harvest, or in preparing a citrus preservative.

[0028] The present invention provides application of the composite bacterial agent or the composition in citrus preservation or in the preparation of a citrus preservative.

[0029] The present invention also provides a method for preventing and controlling citrus diseases or preserving citrus after harvest, wherein the composite bacterial agent or composition is used to spray citrus trees, or to treat citrus after harvest. Bubble treatment.

[0030] Preferably, the citrus fruits are soaked in the composite bacterial agent or composition for 1 to 3 minutes, and then taken out and dried.

[0031] The present invention has the following beneficial effects:

[0032] The invention provides a composite bacterial agent containing Purpurosporium lilacinum and curcumin, wherein Purpurosporium lilacinum can inhibit Xanthomonas citri subspecies citri, Penicillium italicum and Penicillium digitatum, and curcumin alone has no inhibitory effect on these bacteria. However, after Purpurosporium lilacinum and curcumin are used in combination, the antibacterial effect of Purpurosporium lilacinum is significantly enhanced, and the antibacterial rates are respectively increased to 3.7%, 13.6% and 14.5%, and the composite bacterial agent can be better used for the prevention and treatment of citrus canker in the process of citrus planting and green and blue mold diseases of citrus after harvest.

[0033] At the same time, studies have shown that the combination of purpurogenous spores and curcumin can effectively slow down the loss of water and nutrients in post-harvest fruits, reduce the incidence of green and green mold diseases of sugar oranges after harvest, and prolong the post-harvest preservation time of citrus, with good antiseptic and fresh-keeping effects. Therefore, the composite bacterial agent provided by the present invention can be used as an environmentally friendly green agent to replace chemical fungicides, and can be used in the prevention and treatment of citrus canker during citrus cultivation and the prevention and treatment of green and green diseases of citrus fruits after harvest. It can also be used as a preservative or antiseptic agent for post-harvest preservation of citrus, which not only broadens the application of purpurogenous spores, but also can be better used for citrus disease prevention and control and fruit preservation after harvest after purpurogenous spores and curcumin are used, which also provides more methods and products for citrus cultivation and post-harvest disease prevention, and has a wide range of application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The composite bacterial liquid has an inhibitory effect on citrus canker pathogens and blue and green molds.

[0035] Figure 2 The composite bacterial liquid has a preventive and therapeutic effect on post-harvest green mold and green mold diseases of sugar oranges.

[0036] Figure 3 The composite bacterial liquid has a preventive and therapeutic effect on citrus canker.

[0037] Figure 4 The application effect of composite bacterial liquid in the post-harvest preservation of sugar oranges. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0039] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0040] The culture medium used in the embodiment is:

[0041] NA medium: 5.0 g beef extract, 10.0 g peptone, 5.0 g NaCl, 20.0 g agar, dilute to 1000 mL with distilled water, sterilize at 121°C for 20 min.

[0042] NA liquid culture medium: 5.0 g beef extract, 10.0 g peptone, 5.0 g NaCl, 1000 mL distilled water, dilute to 1000 mL, 121°C, 20 min, sterilize for use.

[0043] PDA solid culture medium: 200.0 g peeled potatoes, 20.0 g sucrose, 20.0 g agar, dilute to 1000 mL with distilled water, sterilize at 121°C for 20 min.

[0044] The biocontrol fungus Purpureocillium lilacinum ZJPL1812 strain used in the embodiment has been deposited in the General Microbiological Center of China Microbiological Culture Collection Administration on November 5, 2019, with a deposit number of CGMCC No.18827. The address of the depository is No. 3, Yard No. 1, Beichen West Road, Chaoyang District, Beijing. The isolation and identification of the ZJPL1812 strain is recorded in the existing literature: Ke Xinru, Liu Dengyan, Tan Jianbin, Su Qi, Li Ya. Isolation, identification and biological characteristics of a strain of Purpureocillium lilacinum [J]. Guangdong Agricultural Science, 2022, 49(6): 108-117.

[0045] Example 1 Antibacterial Activity Determination

[0046] 1. Preparation of composite bacterial agent:

[0047] The ZJPL1812 strain of Pseudomonas lilacinus was activated and cultured in PDA medium for 7 days. The ZJPL1812 spores were washed off the PDA plate with 100 mL of sterile water and the spore solution was diluted to a concentration of 1.0 × 10 7 cfu / mL. After drying the lemon leaves at 60°C, crush them with a grinder and pass them through a 40-mesh sieve. Add rove beetle powder to prepare a solid culture medium. Dispense the prepared solid culture medium into tissue culture bottles, cover them with filter caps, and sterilize them at high temperature and high pressure for 1 hour. Take another 15mL of spore liquid, add it to the tissue culture bottle, and culture it at 28°C for 7 days. Use 75% ethanol to extract the solid culture medium cultured for 7 days at a ratio of 2:1 for 24 hours to obtain the fermentation liquid, centrifuge to obtain the supernatant, vacuum filter and concentrate, and filter and sterilize with a 0.22μm microporous filter membrane to obtain the active crude extract of strain ZJPL1812, which is the sterile fermentation liquid of strain ZJPL1812.

[0048] Then, 25 mg of curcumin was added to every 100 mL of sterile fermentation liquid, and the mixture was thoroughly mixed to obtain a composite bacterial agent.

[0049] 2. Preparation of bacterial plates:

[0050] The citrus canker pathogen used was Xanthomonas citrisubsp.citri, the Penicillium was Penicillium italicum, and the green mold was Penicillium digitatum, all of which were isolated and preserved by the Plant Protection Teaching and Research Section of Guangdong Ocean University.

[0051] Take 15 mL of unsolidified PDA solid medium at about 50°C and add 1.0×10 7 200 μL of Penicillium spore suspension and 1 mL of Chlorella spore suspension were poured into sterile culture dishes to prepare plates containing Penicillium and Chlorella respectively. 7 cfu / mL of citrus canker pathogen Xcc was mixed with molten NA solid culture medium cooled to about 50°C in a volume ratio of 1:10, shaken thoroughly and poured into a sterile culture dish to prepare a plate containing Xcc. The above-mentioned bacteria-containing plate was dried and set aside.

[0052] 3. Determination of antibacterial rate:

[0053] An Oxford cup (with an inner diameter of 6 mm, an outer diameter of 8 mm, and a height of 10 mm) was placed in the center of the bacterial plate, and 100 μL of the above-prepared biocontrol agent was added thereto. After culturing at a constant temperature of 28°C for 7 days, the diameter of the inhibition zone was measured by the "cross" method, and the inhibition rate of the biocontrol agent against Xcc and blue and green molds was calculated. An equal amount of sterile water was added to the Oxford cup as a control, and a separate ZJPL1812 strain group and a curcumin group were set up at the same time. The strain group used the sterile fermentation broth of the strain ZJPL1812, and the curcumin group added 25 mg of curcumin to 100 mL of deionized water.

[0054] Inhibition rate = diameter of inhibition zone / diameter of culture dish × 100%

[0055] The antibacterial results of different treatment groups are as follows Figure 1 As shown, curcumin alone has no inhibitory effect on Xcc, Penicillium (P.italicum), and Green Mold (P.digitatum), while the ZJPL1812 strain component has good inhibitory activity against the above three pathogens, with the maximum inhibition zone diameters of 265mm, 163mm, and 325mm, and the inhibition rates of 29.4%, 18.1%, and 36.1%, respectively. In the composite bacterial agent group, the ZJPL1812 sterile fermentation liquid and curcumin significantly increased the inhibitory activity of pathogens, with the inhibition zone diameters of 298mm, 286mm, and 457mm, and the inhibition rates of 33.1%, 31.7%, and 50.6%, respectively.

[0056] In summary, it was shown that the ZJPL1812 strain of Pseudomonas lilacinus had a good inhibitory effect on Xcc, Penicillium, and Chlorella, and that the antibacterial activity of Pseudomonas lilacinus could be further enhanced after being compounded with curcumin.

[0057] Example 2: Control of postharvest penicillium and green mold disease in citrus fruits by using composite bacterial agent

[0058] After the sugar oranges were harvested, a sterile punch was used to pierce a hole of uniform size and moderate depth (without exposing the flesh) on the surface of the citrus. After the hole surface was dried, 50 μL of ZJPL1812 sterile fermentation liquid and 50 μL of composite bacterial agent were added respectively. After the bacterial liquid was dried, 50 μL of Penicillium and Green mold pathogenic bacteria liquid (containing Penicillium and Green mold spores at a concentration of 1.0×10 7 cfu / mL), waited for natural drying and then placed in a plastic box with a lid, and observed the disease situation of sugar oranges every day. Each group contained 10 sugar oranges. An equal amount of sterile water was used instead of the composite bacterial solution as a control, and the experiment was completed under indoor natural environment conditions.

[0059] The results are as follows Figure 2As shown, the sterile fermentation liquid of ZJPL1812 can inhibit the development of green and green mold diseases of sugar oranges after harvest, while the composite bacterial agent can significantly slow down the occurrence of green and green mold diseases of sugar oranges after harvest. The effect of the composite bacterial agent is better than that of the sterile fermentation liquid of ZJPL1812, and it can be better used to prevent and control the occurrence of green and green mold diseases of citrus after harvest.

[0060] Example 3: Control of citrus canker by composite bacterial agent

[0061] The leaves of sugar oranges with the same color, maturity and size were randomly selected, washed with sterile water, disinfected with 75% ethanol for 5 minutes, and then rinsed with sterile water for later use. The experimental groups were as follows: (1) 300 μL Xcc (1×10 7 cfu / mL) bacterial suspension; (2) first spray 300μL of ZJPL1812 strain sterile fermentation liquid on the leaf surface, and then spray 300μL Xcc bacterial suspension after the moisture on the leaf surface is dry; (3) first spray 300μL of composite bacterial agent on the leaf surface, and then spray 300μL Xcc bacterial suspension after the moisture on the leaf surface is dry. After 3h, cover the leaves with sterile plastic bags and keep them at 25℃ and 90% relative humidity for 3d. Five leaves were treated in each group, and three plants were used as experimental objects in each group. After 30d, the disease prevention efficiency was calculated based on the number of lesions formed on the leaves, and the formula is as follows:

[0062]

[0063] Among them, N1 represents the number of lesions on the leaves sprayed with Xcc alone, and N2 represents the number of lesions on the leaves after treatment.

[0064] The results are as follows Figure 3 As shown, according to statistics, the disease prevention efficiency of ZJPL1812 sterile fermentation liquid against citrus canker is 50.6%, and the disease prevention efficiency after treatment with composite bacterial agent is 67.9%, indicating that compounding curcumin in the purpurogenous spore liquid can enhance the prevention and treatment effect of citrus canker.

[0065] Example 4 Effect of the composite bacterial agent on extending the shelf life of citrus fruits after harvest

[0066] Use 75% alcohol to disinfect the surface of the purchased tangerines that are not damaged and are of uniform size. After standing for two minutes, use running water to clean the surface of the tangerines. Place them in a ventilated place to let them dry naturally and set aside. After soaking for 1-2 seconds, take it out and put it in a plastic box after it is naturally dried. Observe the sugar oranges every day to see if they are sick (green mold or blue mold), and record the changes in fruit weight and the incidence rate. Sterile water treatment is also used as a control. The experiment is completed under indoor natural environment conditions.

[0067] Fruit weight loss rate (%) = (fruit weight before storage - fruit weight at different storage periods / fruit weight before storage) / fruit weight before storage × 100%

[0068] Fruit morbidity rate (%) = cumulative number of fruits with disease in this group / total number of fruits in this group × 100%

[0069] The results are as follows Figure 4 As shown in the figure, with the increase of treatment time, the weight loss rate of the fruit in the control group increased from 2.52% on the third day to 8.84% on the tenth day, while the weight loss rate of the sugar orange fruit treated with the composite bacterial agent increased from 0.72% on the third day to 3.68% on the tenth day. It can be seen that the use of composite bacterial agents can effectively slow down the loss of water and nutrients in post-harvest fruits.

[0070] The statistical data of fruit morbidity also confirmed that the compound bacterial agent can reduce the morbidity of sugar oranges after harvest and reduce the number of diseased fruits. The morbidity of sugar oranges treated with the compound bacterial agent was only 27.6%, while the morbidity of untreated sugar oranges reached 100% on the 10th day. It can be seen that the compound bacterial agent prepared by combining Psoralea corylifolia with curcumin can not only reduce the morbidity of green mold and green mold after harvest, but also delay the loss of water and nutrients in the fruit, prolong the shelf life of citrus after harvest, and has the effect of antiseptic preservation.

[0071] In summary, the present invention provides a composite bacterial agent containing Pseudomonas lilacinus and curcumin, wherein Pseudomonas lilacinus can inhibit Xanthomonas citri subspecies citri, Penicillium italicum and Penicillium digitatum, while curcumin alone has no inhibitory effect on these fungi, but the combined use of Pseudomonas lilacinus and curcumin significantly enhances the antibacterial effect of Pseudomonas lilacinus, and the antibacterial rates are increased to 3.7%, 13.6% and 14.5%, respectively, and can be better used for the prevention and treatment of citrus canker during citrus cultivation and citrus post-harvest green and green mold diseases.

[0072] At the same time, studies have shown that the combination of purpurogenous spores and curcumin can effectively slow down the loss of water and nutrients in post-harvest fruits, reduce the incidence of green and green mold diseases of sugar oranges after harvest, and prolong the post-harvest preservation time of citrus, with good antiseptic and fresh-keeping effects. Therefore, the composite bacterial agent provided by the present invention can be used as an environmentally friendly green agent to replace chemical fungicides, and can be used in the prevention and treatment of citrus canker during citrus cultivation and the prevention and treatment of green and green diseases of citrus fruits after harvest. It can also be used as a preservative or antiseptic in the post-harvest preservation of citrus, which not only broadens the application of purpurogenous spores, but can also be better used in citrus disease prevention and control and fruit post-harvest preservation, and also provides more methods and products for citrus cultivation and post-harvest disease prevention, and has a wide range of application value.

[0073] 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. Use of Purpureocillium lilacinum in inhibiting Xanthomonas citri subsp. citri and / or Penicillium italicum, or in preparing an antibacterial agent for inhibiting Xanthomonas citri subsp. citri and / or Penicillium italicum.

2. Use of Purpurosporium lilacinum in inhibiting Penicillium digitatum and simultaneously inhibiting Xanthomonas citri subspecies citri and / or Penicillium italica.

3. A composite bacterial agent, characterized in that: Contains Psoralea corylifolia and curcumin.

4. A composition for preventing and treating citrus diseases or preserving citrus after harvest, characterized in that: The invention relates to a fermentation broth or fermentation supernatant containing Psoralea corylifolia and curcumin.

5. The composition according to claim 4, characterized in that The material-liquid ratio of the curcumin: fermentation liquid or fermentation supernatant is (10-30) mg: (80-150) mL.

6. Use of the composite bacterial agent according to claim 3 or the composition according to any one of claims 4 to 5 in inhibiting any one, any two or three of Xanthomonas citri citri subsp. citri, Penicillium italium, and Penicillium digitatum, or in the preparation of an antibacterial agent that inhibits any one, any two or three of Xanthomonas citri citri subsp. citri, Penicillium italium, and Penicillium digitatum.

7. Use of the composite bacterial agent according to claim 3 or the composition according to any one of claims 4 to 5 in preventing and controlling citrus diseases, or in preparing citrus disease prevention and control products.

8. Use of the composite bacterial agent according to claim 3 or the composition according to any one of claims 4 to 5 in preserving citrus fruits after harvest, or in preparing a citrus preservative.

9. Use of the composite bacterial agent according to claim 3 or the composition according to any one of claims 4 to 5 in citrus preservation or in the preparation of citrus preservatives.

10. A method for preventing and controlling citrus diseases or preserving citrus after harvest, characterized in that: The composite bacterial agent according to claim 3 or the composition according to any one of claims 4 to 5 is sprayed on citrus trees, or the citrus fruits after harvest are treated. Bubble treatment.

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