Biocontrol serratia rubra and application of biocontrol serratia rubra in postharvest disease control, storage and fresh-keeping of pear fruits

Abstract

The invention belongs to the technical field of biological prevention and control of postharvest diseases, and particularly relates to biocontrol serratia rubra and application thereof to postharvest disease control, storage and fresh keeping of pear fruits. The method comprises the following steps: activating and culturing serratia rubra, centrifuging after culturing to obtain thalli, and re-suspending by using sterile normal saline to obtain a bacterial suspension; the method comprises the following steps: punching holes in the surfaces of pears, injecting the holes, and then injecting penicillium expansum spore suspension with the same volume, thereby realizing effective control on penicilliosis caused by penicillium expansum; or uniformly spraying the serratia rubra suspension on the surfaces of the pears, and naturally airing, so as to realize the purposes of disease control, storage and fresh-keeping after the pears are picked. According to the method, the occurrence of penicilliosis after the pears are picked can be remarkably reduced, the natural rotting rate after the pears are picked is reduced, the method is safe and environmentally friendly, no remarkable adverse effect is generated on main quality indexes of the picked pears, the storage quality of the pears can be kept, a remarkable technical effect is achieved, and the application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of biological control of postharvest diseases, and particularly relates to a method for controlling postharvest penicillium disease of pear fruits and storing and preserving pear fruits using Serratia rubrum. Background Art

[0002] Pear is a world-famous fruit. As an excellent tonic fruit, it is known as the king of fruits. However, during the storage and transportation of pears after harvest, they rot and deteriorate due to the infection of pathogenic microorganisms, which greatly reduces the commercial value of pears and causes huge economic losses. Penicillium expansum is the main pathogen causing postharvest penicillium disease in pears. It not only causes the fruit to rot and deteriorate, but also the penicillin (PAT) it secretes has carcinogenic, teratogenic and mutagenic effects, which endangers the health of consumers. Therefore, it is necessary to study a safe and effective means to control the occurrence of postharvest penicillium disease in pears.

[0003] At present, the main methods for controlling post-harvest diseases of fruits and vegetables are physical methods, chemical methods and biological control methods. Physical methods include heat treatment, refrigeration, and controlled atmosphere storage, which can inhibit the activity of pathogens and the accumulation of toxins to varying degrees; however, they have high requirements for equipment and are difficult to industrialize, and have great limitations in practical applications. Chemical methods usually use chemical fungicides to control post-harvest diseases of fruits and vegetables. It is currently the most common prevention and control method. This method is low-cost, quick to take effect, and simple to operate, but its long-term use will cause pathogens to develop drug resistance and cause environmental pollution. Biological control is the use of antagonistic microorganisms of pathogens to prevent and control fruit and vegetable diseases. Compared with physical and chemical methods, it has the advantages of safety and environmental protection. However, the use of antagonistic microorganisms to control fruit and vegetable diseases currently faces the problem of poor results. Moreover, there are few reports on the use of antagonistic bacteria to control post-harvest diseases of pears. Summary of the invention

[0004] In view of the defects and shortcomings of the prior art, the present invention provides a bacterium - Serratia rubidaea, which is isolated and purified in this laboratory, and the strain preservation number is CCTCC NO: M 20241377, and the preservation unit is China Center for Type Culture Collection (CCTCC); the preservation address is: Wuhan University, Wuhan, China; the preservation date is June 26, 2024; the recommended classification name is: Serratia rubidaea B11.

[0005] The crimson serratia in the present invention is obtained by self-screening and identification, and has not been applied to the prevention and treatment of post-harvest diseases of pears. Research has shown that the bacterium has a strong antagonistic effect, and can effectively control the occurrence of post-harvest penicillium and natural rot of pears, reduce the rot rate, and reduce the losses caused by post-harvest diseases; and has no significant adverse effect on the quality of pears, and can slow down the quality deterioration of pears during storage, thereby achieving the effect of storage and preservation, and providing a theoretical basis for its application in post-harvest preservation.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] The Serratia rubrum provided by the present invention is separated and purified in this laboratory and is currently preserved in China Center for Type Culture Collection (CCTCC), and the strain preservation number is CCTCC NO: M 20241377.

[0008] The use of Serratia rubrum provided by the present invention for controlling post-harvest diseases of pear fruits is carried out according to the following steps:

[0009] (1) First, Serratia rubrum was inoculated into LB medium for the first activation culture to obtain an activation solution; then, the activation solution was transferred into a new LB medium for the second activation to obtain a bacterial culture solution, which was centrifuged to obtain bacterial mud, which was washed with sterile saline and prepared into a Serratia rubrum suspension with a concentration of 1×10 6 ~1×10 9 cells / mL, for later use;

[0010] (2) selecting pear fruits without diseases, mechanical damage, and uniform color and size, disinfecting them, then washing them with running water, and placing the washed pear fruits in a sterilized plastic basket to dry; forming wounds of uniform size and depth at the equatorial part of the dried pear fruits, adding the Serratia rubrum suspension prepared in step (1) to each wound, inoculating the suspension of Penicillium expansum spores after standing for a period of time, placing the wounds in a sterilized plastic basket after natural drying, sealing the baskets with plastic wrap, and placing the baskets in a constant temperature and humidity incubator to achieve control of postharvest penicillium disease of pear fruits by Serratia rubrum;

[0011] Alternatively, pears without disease, mechanical damage, uniform color and similar size are selected, and the pears are kept in their natural state without any disinfection treatment. The Serratia rubrum suspension prepared in step (1) is evenly sprayed on the surface of the pears, and the pears are naturally dried, thereby achieving the purpose of post-harvest disease prevention and control and storage and preservation of pears.

[0012] Preferably, the LB medium (1 L) in step (1) is: 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, distilled water to 1000 mL, natural pH, and sterilized at 115° C. for 20 min.

[0013] Preferably, the culture conditions for the first activation culture and the second activation culture in step (1) are: culture at 37° C. for 16 to 18 hours; and the centrifugation conditions are: 4° C., 8000 rpm, and time for 10 to 15 minutes.

[0014] Preferably, the inoculum amount of the activation solution in step (1) is 1-2% (v / v); the concentration of Serratia rubrum is 1×10 8 -1×10 9 CFU / mL.

[0015] Preferably, the disinfection treatment in step (2) is as follows: immersing the pears in water containing 0.2% sodium hypochlorite solution for disinfection for 2-4 minutes; the plastic basket is disinfected by washing it with clean water, drying it, and then spraying it evenly with 75% alcohol to obtain a disinfected plastic basket.

[0016] Preferably, the hole diameter punched in step (2) is 5 mm and the depth is 4 mm.

[0017] Preferably, in step (2), the volume ratio of the bacterial suspension added to each wound to the Penicillium expansum spore suspension is 1:1; the concentration of the Penicillium expansum spore suspension is 1×10 5 spores / mL; the standing period is 2h.

[0018] Preferably, the temperature of the constant temperature and humidity incubator in step (2) is 20-25° C., and the relative humidity is 90%.

[0019] Preferably, in step (2), the bacterial suspension of Serratia rubrum is evenly sprayed on the surface of the pear fruit, and the specific amount is 0.02-0.05 mL of the bacterial suspension per square centimeter.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The Serratia rubrum used in the present invention is isolated and purified in our laboratory and is verified to be a non-toxic bacterium by an acute toxicity test on mice, and is safe and harmless to the human body.

[0022] (2) The Serratia rubrum used in the present invention can effectively control the post-harvest penicillium and natural rot of pear fruits, with a small amount of use and significant effect. At the same time, it has no adverse effect on the quality of pear fruits during storage after harvest, such as hardness, soluble solids and ascorbic acid content. It can also slow down the quality deterioration during storage, thereby controlling the decline in tomato quality, which is beneficial to the storage and preservation of pear fruits.

[0023] (3) The Serratia rubrum used in the present invention has not been reported to be used in the prevention and control of postharvest diseases of pears, and is original; it has a good biological control effect, can replace or reduce the use of chemical fungicides to control postharvest diseases of pears, and at the same time reduce the harm of chemical fungicides to consumer health and the environment, and has the advantages of being green and environmentally friendly and having good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Figure 2 shows the control effect of different concentrations of Serratia rubrum on postharvest Penicillium mold in pear fruits. (A) shows the rot rate of pear fruits, and (B) shows the rot diameter. CK is the control group, which is pear fruits treated with sterile saline. 10^6, 10^7, 10^8 and 10^9 respectively represent the control group with a concentration of 1×10 6 , 1×10 7 , 1×10 8 and 1×10 9 CFU / mL of Serratia rubrum was used to treat pear fruit; the concentration of pathogens used was 1×10 5 CFU / mL; Different lowercase letters represent significant differences (p<0.05).

[0025] Figure 2 (A) shows the control effect of Serratia rubrum on the natural decay of pear fruit; (B) is hardness; (C) is soluble solids; (D) is titratable acid; (E) is ascorbic acid; (F) is browning degree. Note: CK is the control group, pear fruit treated with sterile saline; B is 1×10 8 Pear fruits treated with CFU / mL Serratia rubrum suspension; “*” indicates significant difference (P<0.05). DETAILED DESCRIPTION

[0026] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0027] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art of the present invention generally understand. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and / or materials related to the documents. In the event of conflict with any incorporated document, the content of this specification shall prevail.

[0028] The Serratia rubrum provided by the present invention is separated and purified in this laboratory; it is currently preserved in the China Center for Type Culture Collection, and the strain preservation number is CCTCC NO: M 20241377.

[0029] The culture procedure for Serratia rubrum is:

[0030] (1) First activation: Pick 2 loops of Serratia rubrum from the LB slant and inoculate them into 50 mL of LB medium. Cultivate them at 37° C. and 180 rpm for 16 h to perform the first activation and obtain an activation solution.

[0031] (2) Secondary activation in liquid: Use a sterilized pipette tip to draw 1 mL of activation liquid into another 50 mL bottle of LB medium, and culture at 37°C and 180 rpm for 16 h to obtain bacterial culture liquid;

[0032] (3) Centrifugal separation and resuspension: The bacterial culture solution in (2) was centrifuged at 4°C and 8000 rpm for 10 min and washed twice with sterile saline to remove the culture matrix to obtain bacterial slurry. Finally, the slurry was resuspended with sterile saline and finally adjusted to the desired bacterial concentration (1×10 8 CFU / mL).

[0033] Safety of Serratia rubrum;

[0034] 1. Experimental plan

[0035] Preparation of Serratia rubrum slurry: Serratia rubrum was inoculated into a flask containing 50 mL of LB medium, and cultured in a shaking incubator at 37°C for 16 h. The slurry was obtained by centrifugation, washed, and diluted with pure water to a concentration of 500 mg / mL. The slurry for each oral administration of mice was diluted from fresh slurry.

[0036] The experimental species was SPF-grade KM mice. Twenty KM mice with a weight range of 18g to 22g were selected, half of which were male and half were female. Before the experiment, the mice were pre-fed in the laboratory barrier environment animal room for 3 days to adapt to the environment and quarantine observation, and fasted for 4 hours before the experiment. The test substance was given once, with an oral volume of 20mL / kg·bw, and then observed for 14 days. Throughout the experiment, the activity of the mice, abnormal behavior, poisoning or death were fully observed and recorded. If abnormalities and death occurred, the time, degree and duration of the animal changes were recorded to evaluate possible toxic target organs. The animal weight was weighed and recorded at the beginning of the experiment, and the animal weight was weighed once a week during the observation period.

[0037] 2. Test results

[0038] According to the above test steps, the statistical results of the safety test of Serratia rubrum are as follows:

[0039] The mice that were gavaged with Serratia crimsonense did not die within 14 days, and the mice did not show poisoning or other abnormal phenomena during the whole experiment. As can be seen from Table 1, the acute oral LD ​​50 of this strain for female and male KM mice in the experiment was greater than 10000 mg / kg·bw. According to the acute toxicity classification standard, Serratia crimsonense belongs to the safe and non-toxic bacteria and can be used in the control of post-harvest diseases of pear fruits and storage and preservation.

[0040] Table 1 Results of oral acute toxicity test of Serratia rubrum on mice

[0041]

[0042] As can be seen from Table 1, the animal acute toxicity test confirmed that it is safe and non-toxic.

[0043] Embodiment 1:

[0044] Serratia rubrum is used to control postharvest Penicillium mold in pear fruit;

[0045] 1. Experimental plan

[0046] Select pears without disease, mechanical damage, uniform color and size, soak them in 0.2% sodium hypochlorite solution for 2 minutes, then rinse with running water, put the washed pears in a sterilized plastic basket to dry (the plastic basket is disinfected by washing with water, drying, and then spraying evenly with 75% alcohol). Use a sterile punch to make a 5mm×4mm (diameter×depth) wound at the equatorial part of the dried pears, add 30μL of Serratia rubrum suspension (1×10 8 After 2 h at room temperature, 30 μL of Penicillium expansum spore suspension (1×10 5 CFU / mL). After drying at room temperature, place in a constant temperature and humidity incubator (25°C, relative humidity 90%) for 3-4 days, and record the incidence of pear fruit and the diameter of lesions. Pear fruit treated with sterile saline instead of Serratia rubrum suspension was used as a control. Each treatment was repeated 3 times, and each parallel had 12 pear fruits.

[0047] Decay rate = number of rotten holes / total number of holes × 100%

[0048] 2. Test results

[0049] Depend on Figure 1 As shown in Figure (A), after 3 days of storage, the decay rate of the control group has reached 100%, 1×10 6 , 1×10 7 , 1×10 8 and 1×10 9The incidence of penicillium disease in pear fruits treated with CFU / mL crimson Serratia was 52.38%, 25.40%, 15.87% and 15.87%, respectively, which were significantly lower than those in the control group. After 4 days of storage, the rot rate of pear fruits treated with different concentrations of crimson Serratia was significantly lower than that in the control group, and the control effect increased with the increase of concentration. 8 and 1×10 9 The rot rates of pear fruits treated with CFU / mL of Serratia rubrum were 38.09% and 20.63%, respectively, which were significantly lower than those of the control group (p<0.05).

[0050] Depend on Figure 1 As shown in Figure (B), similar to the decay rate results, on the third day of storage, 1×10 6 , 1×10 7 , 1×10 8 and 1×10 9 The rot diameter of pear fruits treated with CFU / mL Serratia rubrum was significantly lower than that of the control group (15.38 mm) (p<0.05); on the 4th day of storage, 1×10 8 and 1×10 9 The rot diameters of pear fruits treated with CFU / mL were 11.76 mm and 11.55 mm, respectively. 6 and 1×10 7 The rot diameters of pear fruits treated with different CFU / m concentrations were 21.71mm, 14.21mm and 13.14mm, respectively, with significant differences.

[0051] Considering that different concentrations of Serratia rubrum can significantly reduce the occurrence of postharvest Penicillium rot in pear fruits, considering the actual cost and combining the rot diameter index, 1×10 8 CFU / mL of Serratia rubrum can be used for the prevention and treatment of Penicillium pyrifolium and for subsequent experiments.

[0052] Embodiment 2:

[0053] The use of Serratia rubrum for controlling natural decay of pear fruits after harvest and preserving them during storage;

[0054] 1. Experimental plan

[0055] Select pears without disease, mechanical damage, uniform color and size. Do not sterilize them. Keep the pears in their natural state. Spray (1) sterile saline solution (indicated by CK in the figure) and (2) Serratia rubrum suspension (1×10 8CFU / mL), represented by the letter B in the figure; the spraying standard is to spray 0.05mL of bacterial suspension per square centimeter (the volume of bacterial suspension used for each pear fruit is 1-1.5mL according to statistics); after spraying, the fruits are placed in a sterilized plastic basket (the plastic basket is sterilized by washing it with clean water, drying it, and then spraying it evenly with 75% alcohol). After the pear fruit is naturally dried, the plastic basket is sealed with plastic wrap and placed in a constant temperature and humidity incubator (relative humidity 90%) for different days (0, 13, 26, 39, 52d), and the natural decay rate of the pear fruit is counted, and the hardness, soluble solid content, titratable acid content, ascorbic acid content and browning degree of the pear fruit are measured. Each treatment has 3 parallels, and each parallel has 12 pear fruits.

[0056] Natural decay rate (%) = number of rotten fruits / total number of fruits × 100%

[0057] The specific determination methods of quality indicators are as follows:

[0058] 1. Hardness: Use TA-XT2i physical property analyzer to measure the hardness of pear fruit. Use P5 probe, test speed of 5mm / s, test depth of 5mm. Select three points at equal distances at the equator of the pear fruit for testing. The maximum resistance encountered when the probe is inserted into the pear fruit is recorded as hardness (N).

[0059] 2. Soluble solid content: 5.0 g of fruit sample was ground into a homogenate under low temperature conditions, centrifuged at 4°C and 4000 rpm for 10 min, and the supernatant was aspirated. The soluble solid content of pear fruit was determined using a handheld refractometer.

[0060] 3. Titratable acid content: Determine by sodium hydroxide titration. Weigh about 10g of sample, add appropriate amount of distilled water, grind into a mortar into a homogenate, transfer to a 50mL centrifuge tube and let stand for 30min, shaking every 10min. Centrifuge for 10min at 4℃, 8000rpm, aspirate the supernatant into a 25mL volumetric flask and dilute to the scale. Pipette 10mL of sample solution into a conical flask, add 3 drops of 1% phenolphthalein, and titrate with 0.1mol / L NaOH. Titrate until the solution begins to show light pink and does not fade within 0.5min as the end point. Distilled water is used as the blank control, and the results are expressed as mass fraction (%).

[0061] Titratable acid content (%) = (V×c×(V1-V0)×0.067) / (Vs×m)×100%

[0062] Where V is the total volume of the sample extract (mL), c is the NaOH concentration (mol / L), V1 is the volume of sodium hydroxide solution consumed in titrating the sample solution (mL), V0 is the volume of sodium hydroxide solution consumed in titrating distilled water (mL), Vs is the volume of the sample solution taken during titration (mL), m is the sample mass (g), and 0.067 is the malic acid conversion coefficient (g / mmol).

[0063] 5. Ascorbic acid content: Determine by 2,6-dichlorophenol indophenol titration method. Weigh about 10g of pear fruit tissue sample and place it in a mortar, add an appropriate amount of 1% oxalic acid solution, grind it into a homogenate in a mortar under light-proof ice bath conditions, transfer it to a 100mL volumetric flask and make up the volume with oxalic acid, shake it well, let it stand at 4℃ for 10min, then centrifuge and collect the filtrate. Pipette 10mL of filtrate into a conical flask and titrate it with a calibrated 2,6-dichlorophenol indophenol solution until a light red color appears and the solution does not fade within 15s as the end point. At the same time, use 10mL of 20g / L oxalic acid solution as a blank for titration and zero adjustment, three parallels per group. According to the amount of 2,6-dichlorophenol indophenol, calculate the ascorbic acid content in pear fruit, expressed as the mass of ascorbic acid contained in every 100g sample, that is, mg / 100g.

[0064] Titer T = (c × V) / (V1-V0)

[0065] Where c is the mass concentration of ascorbic acid standard solution (mg / mL), V is the volume of ascorbic acid standard solution absorbed (mL), V1 is the volume of 2,6-dichlorophenol indophenol solution consumed when titrating the standard liquid (mL), and V0 is the volume of 2,6-dichlorophenol indophenol solution consumed when titrating the blank (1% oxalic acid) (mL).

[0066] Ascorbic acid content (mg / 100g) = (V×(V1-V0)×T) / (Vs×m)×100

[0067] Where V is the total volume of the sample extraction solution (mL), V1 is the volume of the dye consumed in the sample titration (mL), V0 is the volume of the dye consumed in the blank titration (mL), Vs is the volume of the sample solution taken during the titration (mL), and m is the sample mass (g).

[0068] 6. Browning degree

[0069] Take 10g of pear sample and homogenize it with 20mL of distilled water. After centrifugation, take 10mL of supernatant and mix it with 15mL of 95% ethanol. Centrifuge again and measure the absorbance of the supernatant at 420nm to indicate the degree of browning.

[0070] 2. Test results

[0071] Depend on Figure 2 As can be seen from Figure (A), after 1×108 The pear fruits treated with CFU / mL crimson Serratia were stored at 20°C for 13 days, and like the control group, no rot occurred. On the 26th day of storage, the rot rate of the treatment group was 0.00%, and the rot rate of the control group was 9.09%; on the 39th day, the rot rate of the treatment group was still 0.00%, and the rot rate of the control group reached 18.18%; on the 52nd day, the rot rates of the treatment group and the control group were 9.09% and 31.82%, respectively. On the 26th, 39th, and 52nd days of storage, the natural rot rate of the crimson Serratia treatment group was significantly lower than that of the control group (p<0.05). It can be seen that crimson Serratia has a significant control effect on the natural rot of post-harvest pear fruits. Therefore, it is shown that the crimson Serratia of the present application has a good preventive and therapeutic effect on the natural rot of post-harvest pear fruits.

[0072] Depend on Figure 2 As can be seen in Figure (B), the hardness of pears during postharvest storage has a consistent trend, showing a decreasing trend with increasing storage time. However, the hardness of the group treated with Serratia rubrum is always higher than that of the control group, and there is a significant difference on the 13th day of storage.

[0073] Depend on Figure 2 As can be seen from Figure (C), during the post-harvest storage process, the overall change in the soluble solids content of pear fruit basically showed a trend of first increasing, then decreasing, and then increasing again. On the 13th and 39th days of storage, the soluble solids content of the treatment group was higher than that of the control group, and there was a significant difference on the 13th day.

[0074] Depend on Figure 2 As can be seen from Figure (D), during the post-harvest storage of pear fruits, the titratable acid content of the treatment group showed a trend of first decreasing and then increasing. The trends of the treatment group and the control group were basically consistent, and there was no significant difference between the two.

[0075] Depend on Figure 2 As can be seen from Figure (E), during the storage process of pear fruits after harvest, the ascorbic acid content showed a trend of first increasing and then decreasing. During the entire storage period, the ascorbic acid content of pear fruits treated with Serratia rubrum was slightly higher than that of the control group, but there was no significant difference between the two.

[0076] Depend on Figure 2 (F) It can be seen that during the entire storage process after the pear fruit was harvested, the browning degree of the pear fruit treated with Serratia crimsonii was always lower than that of the control group. On the 52nd day, there was a significant difference between the browning resistance of the pear fruit treated with Serratia crimsonii and the control group, indicating that the browning degree can be slowed down after treatment with Serratia crimsonii.

[0077] In summary, Serratia rubrum has a good preventive and therapeutic effect on the natural decay of pear fruit, and has no significant adverse effect on the quality of pear fruit. It can also alleviate the deterioration of pear fruit quality to a certain extent, and can be used for the storage and preservation of post-harvest pear fruit.

[0078] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A biocontrol agent for Serratia rubrum, characterized in that: The biocontrol Serratia rubidaea is Serratia rubidaea B11, which is preserved in China Center for Type Culture Collection with a preservation number of CCTCC NO: M20241377.

2. Use of the biocontrol Serratia rubrum according to claim 1 for postharvest disease control and storage and preservation of pear fruit.

3. The use of the biocontrol Serratia rubrum for postharvest disease control and storage and preservation of pear fruits according to claim 2, characterized in that: The specific steps are as follows: (1) First, Serratia rubrum was inoculated into LB medium for the first activation culture to obtain an activation solution; then, the activation solution was transferred into a new LB medium for the second activation to obtain a bacterial culture solution, which was centrifuged to obtain bacterial mud, which was washed with sterile saline and prepared into a Serratia rubrum suspension with a concentration of 1×10 6 ~1×10 9 cells / mL; (2) selecting pear fruits without diseases, mechanical damage, and uniform color and size, disinfecting them, then washing them with running water, and placing the washed pear fruits in a sterilized plastic basket to dry; forming wounds of uniform size and depth at the equatorial part of the dried pear fruits, adding the Serratia rubrum suspension prepared in step (1) to each wound, inoculating the suspension of Penicillium expansum spores after standing for a period of time, placing the wounds in a sterilized plastic basket after natural drying, sealing the baskets with plastic wrap, and placing the baskets in a constant temperature and humidity incubator to achieve control of postharvest penicillium disease of pear fruits by Serratia rubrum; Alternatively, pears without disease, mechanical damage, uniform color and similar size are selected, and the pears are kept in their natural state without any disinfection treatment. The Serratia rubrum suspension prepared in step (1) is evenly sprayed on the surface of the pears, and the pears are naturally dried, thereby achieving the purpose of post-harvest disease prevention and control and storage and preservation of pears.

4. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits by using Serratia rubrum according to claim 1, characterized in that: The LB medium described in step (1) is composed of 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, and distilled water to 1000 mL, with a natural pH and sterilized at 115° C. for 20 min.

5. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits using Serratia rubrum according to claim 1, characterized in that: The centrifugation conditions in step (1) are: 4°C, 8000 rpm, and time 10-15 min; the conditions for the first activation culture and the second activation culture are: temperature 37°C, time 16-18 h.

6. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits using Serratia rubrum according to claim 1, characterized in that: The inoculum volume of the activation solution in step (1) is 1-2% (v / v); the concentration of Serratia rubrum is 1×10 8 -1×10 9 CFU / mL.

7. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits using Serratia rubrum according to claim 1, characterized in that: The disinfection treatment in step (2) is as follows: the pears are immersed in water containing 0.2% sodium hypochlorite solution for disinfection for 2-4 minutes; the plastic baskets are disinfected by washing with clean water, drying them, and then spraying them evenly with 75% alcohol to obtain disinfected plastic baskets.

8. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits using Serratia rubrum according to claim 1, characterized in that: The hole diameter of the punch in step (2) is 5 mm and the depth is 4 mm; 30 μL of the Serratia rubrum suspension and the Penicillium expansum spore suspension are added to each wound; and the standing period is 2 h; The concentration of the Penicillium expansum spore suspension is 1×10 5 CFU / mL.

9. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits using Serratia rubrum according to claim 1, characterized in that: The temperature of the constant temperature and humidity incubator in step (2) is 20-25° C., and the relative humidity is 90%.

10. The method for preventing and controlling post-harvest diseases of pear fruits and storing and preserving pear fruits using Serratia rubrum according to claim 1, characterized in that: In step (2), the Serratia rubrum suspension is evenly sprayed on the surface of the pear fruit, with a specific amount of 0.02-0.05 mL of the suspension per square centimeter.

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