Soybean composite growth-promoting microbial coating agent and coating method thereof

Abstract

The invention provides a soybean composite growth-promoting microbial coating agent and a coating method thereof, bacterial strains with a soybean growth-promoting effect are selected and compounded into a mixed bacterial agent according to a certain variety and proportion, biochar is innovatively used for seed coating, and the composite coating agent comprises an adsorbent, a nutritional agent, a binder and the bacterial composition. According to the invention, strains with a plant growth promoting effect are selected and compounded into a mixed microbial inoculum according to a certain variety and proportion, and the biochar is innovatively used for seed coating, so that plant growth is promoted by using the coating agent, and the abiotic stress resistance is improved. The coating agent is efficient, low in toxicity, safe and reliable, the preparation method is simple and feasible, and the coating agent has important practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of plant cultivation, and particularly relates to a soybean composite growth-promoting microbial coating agent and a coating method thereof. Background Art

[0002] At present, most of the domestic patent applications related to biochar and microbial coating agents only involve the separate use of biochar or microbial agents, or the application in combination with pesticides and fertilizers; there are relatively few patent applications using biochar as an adsorbent for microbial seed coating.

[0003] The patent document with the application number CN202010776820.5 and the title "A Fertilizer for Soybeans in Saline-Alkali Soil and a Fertilization Method for Improving the Nutrient Efficiency of Soybeans in Saline-Alkali Soil" expounds that by spreading a base fertilizer composed of biochar and a soil conditioner before soybean planting and then plowing the land, the physical and chemical properties of the soil can be improved, the soil productivity can be increased, and environmental pollution can be reduced; the patent document with the application number CN 202211465818.1 and the title "A Soybean Seed Coating Agent and Its Application" expounds the problem of preventing Phytophthora root rot of soybeans by preparing a seed coating with a composite bacterial solution in a specific ratio; the patent document with the application number CN202222011105.X and the title "A Planting Seed Wrapping Structure" expounds a method of using biochar as an antifreeze layer for seed wrapping; the patent document with the application number CN202211620591.3 and the title "A Soybean Rhizobium Biological Protectant and Its Preparation Method and Application" expounds a method of using Bacillus pumilus to mix with rhizobia to coat plant bare seeds or coated seeds, which can improve the seed coating efficiency and the survival rate of rhizobia during seed dressing and storage.

[0004] Based on the existing technology, the current coating agent products on the market mainly use pesticide coating. There are few reports on composite coating agents constructed with biochar - non-rhizobial soybean growth-promoting bacteria. Although the use of pesticide coating agents can effectively inhibit the occurrence of soil-borne diseases, it also brings problems such as soil pesticide residues and inhibition of the activity of soybean rhizosphere microorganisms, causing environmental pollution and being unfavorable to the development of agricultural ecological circular economy. Therefore, it is particularly important to develop a seed coating agent that can increase soybean yield. Summary of the Invention

[0005] The inventor collected soybean roots from arid areas and isolated strains with plant growth-promoting attributes such as nitrogen fixation, phosphorus solubilization, potassium solubilization, phytohormone production, siderophore production, and ACC deaminase production in the rhizosphere by means of the plate coating and streaking technique; a series of strains that can promote the stress-resistant growth of soybeans were obtained through isolation and purification. Through combined inoculation verification, strains A and B with excellent effects were finally screened out to construct a compound microbial inoculant. After species identification, they were Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 respectively, and the above-mentioned strains were preserved respectively. Among them, the preservation date of the Chryseobacterium daecheongense GraJ1: January 12, 2024, the preservation unit: China Center for Type Culture Collection (CCTCC), the address of the preservation unit: Wuhan University, Wuhan, China, the taxonomic name: Chryseobacterium daecheongense GraJ1, and the preservation number is CCTCC NO: M 2024089. The preservation date of the Massilia phyllostachyos JC3: January 12, 2024, the preservation unit: China Center for Type Culture Collection (CCTCC), the address of the preservation unit: Wuhan University, Wuhan, China, the taxonomic name: Massilia phyllostachyos JC3, and the preservation number is CCTCC NO: M 2024087.

[0006] On the other hand, the present invention provides a compound microbial inoculant, which comprises a composition of the above-mentioned strains, and the compound microbial inoculant is a liquid inoculant or a solid powder inoculant. The ratio of the above-mentioned microbial inoculants is preferably 1:9 to 9:1, the preferred ratio is (1-5):(1-5), and more preferably, the ratio is (0.5-2):(0.5-2).

[0007] In the above-mentioned compound microbial inoculant, preferably, the liquid inoculant or the solid powder inoculant comprises a protective agent and the above-mentioned strain composition; preferably, the effective viable count concentration of the strain composition in the liquid inoculant is 10 6 -10 13 CFU / mL; preferably, the effective viable count concentration of the strain composition in the solid powder inoculant is 10 6 -10 13 CFU / g. Preferably, the above-mentioned effective viable count concentration is not less than 10 6 、10 7 、10 8 、10 9 、10 10 、10 11 、10 12 、10 13 CFU / g.

[0008] In the above composite microbial inoculum, preferably, the protective agent includes a K2HPO4-KH2PO4 buffer solution with a pH of 7.2 and / or glycerol.

[0009] On the other hand, the present invention provides a composite coating agent, which includes: the above-mentioned bacterial composition or composite microbial inoculum, an adsorbent, and a binder.

[0010] In the above composite coating agent, preferably, the composite coating agent further includes a nutrient agent, and the nutrient agent includes one or a combination of trehalose crystals, molasses, phosphate rock powder, potassium ore powder, boron ore powder, ferrosilicate powder, composite trace elements, fulvic acid, and humic acid.

[0011] In the above composite coating agent, preferably, the binder includes carboxymethyl cellulose and maltodextrin; wherein, the weight ratio of carboxymethyl cellulose to maltodextrin is (40-60):(60-40); preferably, the weight ratio of carboxymethyl cellulose to maltodextrin is (0.5-2):1.

[0012] In the above composite coating agent, preferably, the adsorbent includes a combination of one or more of biochar, diatomaceous earth, and straw powder. More preferably, the adsorbent is composed of biochar and diatomaceous earth; further preferably, the weight ratio of biochar to diatomaceous earth is (1-9):(9-1); the weight ratio of diatomaceous earth to biochar is (1-4):(1-4); further preferably, the weight ratio of biochar to diatomaceous earth is (0.5-2):1.

[0013] In the above composite coating agent, preferably, the weight ratio of the bacterial composition or composite microbial inoculum, adsorbent, binder, and nutrient agent is (1-100):(200-500):(20-500):(100-200).

[0014] On the other hand, the present invention provides a method for preparing a composite coating agent. Specifically, the bacteria in the above bacterial composition are respectively subjected to strain activation, shake flask culture, and fermentation scale-up culture with a modified R2A medium, the cells are collected by centrifugation, freeze-dried and added with freeze-dried additives to make a solid-state inoculum, or directly added with a liquid protective agent to make a liquid inoculum, and mixed according to the above ratio to obtain the above composite microbial inoculum. According to the above formulas of the adsorbent, nutrient agent, and binder, the adsorbent, nutrient agent, and binder are respectively prepared; the adsorbent, nutrient agent, binder, and composite microbial inoculum are independently packaged to obtain the composite coating agent.

[0015] In the above method for preparing the composite coating agent, preferably, the following preparation steps are further included during the use of the composite coating agent: mixing an adsorbent, a nutrient agent and a binder, adding sterile water and stirring evenly to obtain a mixed matrix solution; then adding the composite microbial inoculum into the mixed matrix solution and mixing evenly to prepare a composite coating agent liquid solution. Preferably, in the composite coating agent liquid solution, the dosage ratio of the binder to the sterile water is (20-100) g: 1000 mL; the effective viable bacteria concentration of the composite microbial inoculum in the composite coating agent liquid solution is 10 6 -10 9 CFU / mL; preferably not less than 10 6 、10 7 、10 8 、10 9 CFU / mL.

[0016] In the above method for preparing the composite coating agent, preferably, for the modified R2A culture medium, the proportion of each component in the formula is: 1.3 g of glucose, 1.3 g of bacteriological peptone, 1.3 g of acid-hydrolyzed casein, 1.3 g of yeast extract, 0.8 g of K2HPO3·3H2O, 0.8 g of sodium pyruvate, 0.15 g of MgSO4·7H2O, adding 1000 mL of distilled water; for the agar solid culture medium, based on every 1000 mL of the culture medium, 15 g of agar can be additionally added.

[0017] In the above method for preparing the composite coating agent, preferably, the additive is an additive for maintaining the survival of the bacterial species.

[0018] On the other hand, the present invention provides the application of the above-mentioned bacterial composition, composite microbial inoculum and composite coating agent in promoting the stress-resistant growth of plants.

[0019] On the other hand, the present invention provides the application of the above-mentioned bacterial composition, composite microbial inoculum and composite coating agent in improving the biological performance of plants. Preferably, improving the biological performance of plants includes but is not limited to increasing the grain weight of plant seeds, increasing the number of seeds per unit area, increasing the number of seeds per plant and / or the thousand-grain weight, increasing the yield per mu and / or increasing the biomass.

[0020] Preferably, the plant is a dicotyledonous plant, preferably a leguminous plant, preferably a leguminous plant, more preferably a plant of the order Fabales; more preferably a leguminous plant; the leguminous plant is alfalfa, lotus corniculatus, soybean, pea, peanut, kidney bean, mung bean, adzuki bean, broad bean, cowpea, milk vetch, liquorice or astragalus membranaceus; more preferably a plant of the genus Glycine; more preferably soybean.

[0021] The beneficial effects of the present invention include but are not limited to:

[0022] In the present invention, diatomite / biochar is used to adsorb the bacteria in the composite microbial inoculant and provide a certain habitat environment for them; the coating agent fits closely with the plant seeds and is more suitable for providing beneficial microbial communities for plants in the initial stage of plant germination; the composite microbial community can promote plant growth, and at the same time, the competitive effect generated by the preemptive effect can reduce the occurrence of soil-borne diseases to a certain extent.

[0023] The present invention selects strains with plant growth-promoting effects, formulates them into a mixed inoculant according to a certain type and ratio, and innovatively uses biochar for seed coating, realizing the promotion of plant growth by the coating agent and improving its abiotic stress resistance. This coating agent is highly efficient, low-toxic, safe and reliable, and the preparation method is simple and feasible, with important practical value. Brief Description of the Drawings

[0024] Figure 1 Changes in the growth state of soybeans treated with the composite coating agent at the seedling stage compared with those without coating treatment. CK is the bare seeds directly planted; BC is the seeds treated with the bacteria-containing composite coating agent.

[0025] Figure 2 Comparison of the development states of soybeans treated with the composite coating agent at the jointing stage. CK is the bare seeds; BC is the treatment with the bacteria-containing coating agent; NK is the treatment with the bacteria-free coating agent.

[0026] Figure 3 Comparison of the development states of soybeans treated with different strains of the composite coating agent at the jointing stage. CK is the bare seeds; NK is the treatment with the bacteria-free coating agent.

[0027] Figure 4 Effect of drying the coated soybeans.

[0028] Figure 5 Effect of the coated soybeans at the jointing stage in the field environment. The left figure shows the roots of the uncoated V6 soybeans, and the right figure shows the roots of the coated V6 soybeans.

[0029] Figure 6 Plant state of the coated soybeans at the jointing stage in the field planting. Detailed Embodiments

[0030] Before further describing the specific implementation embodiments of the present invention, it should be understood that the protection scope of the present invention is not limited to the following specific implementation embodiments; it should also be understood that the terms used in the embodiments of the present invention are for describing specific implementation embodiments and not for limiting the protection scope of the present invention.

[0031] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value therebetween can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the technical field of the present invention. Except for the specific methods, equipment, and materials used in the embodiments, according to the knowledge of those skilled in the technical field of the present invention and the description of the present invention, any methods, equipment, and materials of the prior art similar to or equivalent to those described in the embodiments of the present invention can also be used to implement the present invention.

[0032] Unless otherwise specified, the experimental methods, detection methods, and preparation methods disclosed in the present invention all adopt the conventional techniques in the technical field.

[0033] Regarding the modified R2A medium involved in the present invention, the proportion of each component in the formula is as follows: 1.3 g of glucose, 1.3 g of bacteriological peptone, 1.3 g of acid-hydrolyzed casein, 1.3 g of yeast extract, 0.8 g of K2HPO3·3H2O, 0.8 g of sodium pyruvate, 0.15 g of MgSO4·7H2O, and add 1000 mL of distilled water; for the agar solid medium, based on every 1000 mL of the medium, 15 g of agar can be additionally added.

[0034] Example 1 Screening, Isolation and Identification of Strains

[0035] Collect the soybean roots planted in arid soil, brush off the rhizosphere soil with a sterilized brush, add 1 g of the test soil to a test tube with glass beads and containing 9 mL of sterile water, shake it on a vortex shaker for 10 min, and then perform dilution in sequence.

[0036] Using the dilution coating method, coat them on the Mengjina medium, Aleksandrov medium, Ashby medium, associative nitrogen fixation medium, and PKO medium respectively, and culture at 30°C. According to the growth situation of the strains on the selective medium, select the single colonies with faster and better growth, repeatedly purify them by the streak plate method, inoculate them into the corresponding liquid medium for culture, centrifuge the bacterial liquid after 3 d, and store it at -80°C for standby.

[0037] Inoculate the bacteria on the Ashby medium, associative nitrogen fixation medium, Mengjina medium, and PKO medium, and judge their nitrogen fixation, phosphorus solubilization, and phosphorus dissolution activities by the growth situation of the strains on the selective medium and the presence or absence of clear zones: inoculate the potassium-solubilizing bacteria on the Aleksandrov medium (added with bromothymol blue), culture in an incubator at 30°C for 3 - 5 d, and observe whether the colonies turn yellow to judge the potassium-solubilizing ability of the strains.

[0038] A series of strains that can promote the stress-resistant growth of soybeans are obtained through isolation and purification. Through combined inoculation verification, strains with excellent effects are finally selected to construct a bacterial composition. The results are shown in Table 1, Table 2, and Table 3.

[0039] Table 1 Effects of single strain inoculation on the growth of soybean seedlings

[0040]

[0041]

[0042] Table 2 Synthetic community construction plan

[0043]

[0044] Table 3 Effects of synthetic community on the growth of soybean seedlings

[0045]

[0046]

[0047] Through considerations of various factors such as the results of plant experiments, it was determined to construct the artificial synthetic community SynCom-01 with mr002 as the core strain supplemented by the mr011 strain.

[0048] After obtaining the pure culture of the strain, the Chelex-100 resin method was used to heat-lyse the bacterial cells to extract the bacterial genomic DNA. The specific operation is as follows: Pick an appropriate amount of purified single bacterial community into 100 μL of 10% Chelex-100 resin suspension, vortex to fully mix the bacterial cells with the resin suspension, break the cells in a boiling water bath to release the bacterial genomic DNA. Centrifuge at 10000 rpm for 10 min, and take the supernatant as the PCR template.

[0049] Amplify the 16S rRNA gene according to the PCR reaction system in Table 4 and the amplification program in Table 5.

[0050] Table 4 PCR reaction system for 16S rRNA gene

[0051] Reagent Name Volume (20 μL) 10× Buffer 2.0 μL dNTP 1.6 μL 27F 0.2 μL 1492R 0.2 μL Taq Polymerase 0.1 μL Bacterial DNA Template 1.0 μL ddH2O 14.9 μL

[0052] Table 5 PCR amplification program for 16S rRNA gene

[0053]

[0054]

[0055] The PCR products were sent to Shanghai Sangon Biotech Co., Ltd. for sequencing. After obtaining the results, the sequence fragments with better sequencing quality (about 700 bp) were intercepted, and the 16S sequences were aligned using the web version of BLAST (https: / / blast.ncbi.nlm.nih.gov / Blast.cgi) program with reference to the NCBI rRNA / ITS databases. After identification, the two plant growth-promoting bacteria were Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 respectively.

[0056] Example 2: Activation, culture, collection and preparation of microbial bacterial liquid of bacteria

[0057] 100 mL of glycerol-preserved bacterial liquid (Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 isolated in Example 1) were respectively pipetted and spread on the modified R2A medium, and cultured at 25 °C. Single colonies with typical colony characteristics and rapid growth were picked and placed in the corresponding liquid medium of modified R2A and cultured at 25 °C. When cultured to the middle and late logarithmic phase, centrifuged at a centrifugal force of 8000 g, washed repeatedly 3 times with K2HPO4-KH2PO4 buffer (pH 7.2), and then resuspended in the same buffer to a cell concentration of 10 9 CFU / mL, and the bacterial liquids of Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 were respectively prepared.

[0058] Example 3: Comparative test on the effect of different bacterial compositions coating on soybean growth

[0059] 1. Preparation of the liquid solution of the composite coating agent used in this example

[0060] a) Preparation of the mixed matrix: 200 g of adsorbent (100 g of diatomaceous earth + 100 g of biochar), 20 g of binder (10 g of carboxymethyl cellulose + 10 g of maltodextrin), 100 g of nutrient agent (50 g of molasses + 50 g of humic acid) were mixed, and 1000 mL of sterile water was added and stirred evenly to obtain a mixed matrix solution.

[0061] b) Preparation of the liquid solution of the composite coating agent: Then, according to the method in Example 2, Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 were respectively made into bacterial liquids, and the effective viable bacteria concentration in both bacterial liquids was 10 9CFU / mL. Subsequently, 5 mL of each of the Chryseobacterium daecheongense GraJ1 and Massiliaphyllostachyos JC3 bacterial solutions was added to the mixed matrix solution and mixed evenly to prepare a composite coating agent. Among them, the effective viable bacteria concentration in the liquid solution of the composite coating agent was not less than 10 7 CFU / mL.

[0062] 2. Coating and planting of soybean seeds

[0063] The dry wheat seeds were added to a seed coating machine / stirrer. After starting the stirring, the composite coating agent was added. Among them, the weight ratio of wheat seeds to the dosage of the liquid solution of the composite coating agent was 1 kg: 25 mL. Stir until the coating agent was evenly wrapped on the surface of the seeds, and then sun-dried for 120 min before sowing.

[0064] In this example, the effect of different bacterial composition coatings on soybean growth was further explored. A fixed adsorbent combination was used, where the weight ratio of diatomite to biochar was 5:5 as the adsorbent. After seed coating, with or without the addition of different strain combinations of bacterial compositions, the soybean growth indexes were measured. The results are shown in Table 6.

[0065] Table 6 Effects of different bacterial composition coatings on soybean growth

[0066]

[0067] Using diatomite:biochar weight ratio of 5:5 as the adsorbent for seed coating, after adding growth-promoting microbial strains, compared with the coating treatment without adding strains, both the above-ground dry weight and the underground dry weight of soybeans increased. Using the bacterial composition of Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 for microbial coating, compared with coating with the above strains added separately, the growth-promoting effect on soybeans was further improved.

[0068] Example 4: Optimization of abiotic coating components

[0069] In this example, the abiotic coating components were further optimized. Different adsorbent formulations were prepared as shown in Table 7, and the soybean growth indexes were further measured.

[0070] 1. Preparation of the liquid solution of the composite coating agent used in this example

[0071] a) Mixed matrix preparation: Mix 200 g of adsorbent (prepared as shown in Table 7), 20 g of binder (10 g of carboxymethyl cellulose + 10 g of maltodextrin), and 100 g of nutrient agent (50 g of molasses + 50 g of humic acid), add 1000 mL of sterile water and stir evenly to obtain a mixed matrix solution.

[0072] b) Preparation of liquid solution of composite coating agent: Then, according to the method in Example 2, make Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 into bacterial solutions respectively. The effective viable bacteria concentration in both bacterial solutions is 10 9 CFU / mL. Then add 5 mL of each of the Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 bacterial solutions to the mixed matrix solution and mix evenly to prepare a composite coating agent. Among them, the effective viable bacteria concentration in the liquid solution of the composite coating agent is not less than 10 7 CFU / mL.

[0073] 2. Coating and planting of soybean seeds

[0074] Add dry soybean seeds to the seed coating agent and place them in a 1.5 kw feed mixer. After starting the stirring, add the composite coating agent. Among them, the weight ratio of soybean seeds to the dosage of the liquid solution of the composite coating agent is 1 kg: 25 mL; stir until the coating agent is evenly wrapped on the seed surface, and then sun-dry for 120 min before sowing.

[0075] Table 7 Influence of adsorbent on soybean growth

[0076]

[0077] After passing through a 1 mm sieve, soybean straw powder and wood chip powder used as adsorbents cannot adhere well to the surface of soybean seeds; while using a compound of diatomite and biochar in different proportions as adsorbents, the biomass of soybeans in the seedling stage has increased, and the increase range has been optimized from about 3% to 12 - 14%. Among them, the equal proportion compound of diatomite and biochar has the best effect.

[0078] Example 5: Influence of coating on soybean growth under stress resistance conditions

[0079] 1. Preparation of the liquid solution of the composite coating agent used in this example

[0080] a) Mixed matrix preparation: Mix 200 g of adsorbent (100 g of diatomite + 100 g of biochar), 20 g of binder (10 g of carboxymethyl cellulose + 10 g of maltodextrin), and 100 g of nutrient agent (50 g of molasses + 50 g of humic acid), add 1000 mL of sterile water and stir evenly to obtain a mixed matrix solution.

[0081] b) Preparation of the liquid solution of the composite coating agent: Then, according to the method in Example 2, make the Chryseobacterium daecheongense GraJ1 and Massilia phyllostachyos JC3 into bacterial solutions respectively. The effective viable bacteria concentration in both bacterial solutions is 10 9 CFU / mL. Then add 5 mL of each of the Massilia phyllostachyos JC3 bacterial solution and the Chryseobacterium daecheongense GraJ1 bacterial solution to the mixed matrix solution and mix evenly to prepare the composite coating agent. Among them, the effective viable bacteria concentration in the liquid solution of the composite coating agent is 10 7 CFU / mL.

[0082] 2. Coating and planting of soybean seeds

[0083] Add dry soybean seeds to a seed coating machine / stirrer. After starting stirring, add the composite coating agent. Among them, the weight ratio of soybean seeds to the dosage of the liquid solution of the composite coating agent is 1 kg: 25 mL; stir until the coating agent is evenly wrapped on the surface of the seeds, and then sun-dry for 120 min before sowing.

[0084] (1) Results of the strain pot experiment:

[0085] The pot experiments were all completed under drought stress conditions. The simulated drought stress condition was to pour 60 mL of 15% peg-6000 solution once a week. Measure the growth indexes of soybeans at the V6 stage, and the results are shown in Table 8

[0086] Table 8 Effects of coating on the growth of soybeans at the V6 stage under stress resistance conditions

[0087]

[0088]

[0089] Compared with the uncoated treatment, the emergence rate of soybeans treated with the composite coating agent increased by 22.22%, the dry weight of the above-ground part increased by 38.55%, and the dry weight of the underground part increased by 19.89%.

[0090] (2) Results of the field demonstration experiment:

[0091] In the 2024 field experiment, the soybean roots treated with the composite coating agent were more developed than those of the uncoated treatment, with an increase in lateral fibrous roots and a significant increase in the number of nodules as Figure 4 shown. The grain weight per unit area and the number of grains per unit area increased by 10.47% and 16.15% respectively, and the number of grains per plant and the 1000-grain weight increased by 7.26% and 3.74% respectively; the yield per mu increased from 473 kg to 540 kg, an increase of 14.16%.

[0092] It can be seen from the above data that the physiological indexes of the soybeans treated with the composite coating agent are significantly improved compared with those of the uncoated soybeans.

[0093] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A Chryseobacterium daecheongense GraJ1, characterized in that The strain has the function of protecting plant root systems and is preserved in China Center for Type Culture Collection (CCTCC) with a preservation number of CCTCC NO: M 2024089.

2. A Massilia phyllostachyos JC3, characterized in that: The strain has the function of protecting plant roots and is preserved in the China Center for Type Culture Collection (CCTCC) with a preservation number of CCTCC NO: M 2024087.

3. A composite bacterial agent, characterized in that: It comprises the Chryseobacterium as claimed in claim 1 and / or the Massillaria as claimed in claim 2.

4. A composite coating agent, characterized in that: The composite bacterial agent is prepared according to claim 3.

5. The composite coating agent according to claim 4, characterized in that It also contains adsorbents, binders and / or nutrients.

6. The composite coating agent according to claim 4 or 5, characterized in that: The effective live bacterial concentration of the strain is not less than 10 7 CFU / ml.

7. The composite coating agent according to claim 6, characterized in that The adsorbent comprises diatomaceous earth and biochar in a weight ratio of (1-4):(1-4); the binder is carboxymethyl cellulose and / or maltodextrin; and the nutrient is molasses and / or humic acid.

8. Use of the strain according to claim 1 or 2, the composite bacterial agent according to claim 3 or the composite coating agent according to any one of claims 4 to 7 in improving the biological performance of plants.

9. The use according to claim 8, characterized in that The improvement of the biological performance of the plant includes but is not limited to increasing the grain weight of the plant, increasing the number of grains per area, increasing the number of grains per plant and / or the thousand-grain weight, increasing the yield per mu and / or increasing the biomass.

10. The use according to claim 8 or 9, characterized in that: The plant is a leguminous plant.

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