Trichoderma asperellum-bacillus synthetic flora as well as construction method and application thereof

Abstract

The invention provides bacillus cereus, the bacillus cereus is named as bacillus cereus, the bacillus cereus is registered and preserved in Guangdong Microbial Culture Collection Center, and the preservation number is GDMCC NO: 66395. The invention further provides a synthetic flora, and the synthetic flora contains the bacillus cereus and the trichoderma asperellum MM7. The invention further provides a preparation method of the bacillus cereus and the trichoderma asperellum MM7. A synthetic flora constructed by the bacillus cereus and Trichoderma asperellum MM7 has a better effect of promoting the growth of banana plants, can be used for preparing a mixed bacterial agent or a microbial fertilizer, is beneficial to improving the economic benefits of the banana planting industry, and has a wide application space in green and sustainable development of the banana industry.

Description

Technical Field

[0001] The present invention relates to the biological field, and in particular to a synthetic bacterial group of Trichoderma aspergillus and Bacillus, and a construction method and application thereof. Background Art

[0002] In the agricultural production system, the use of fertilizers and pesticides is a crucial link. For a long time, the irrational application of chemical fertilizers has brought a heavy burden to the environment. The large-scale use of chemical fertilizers not only causes soil compaction and acidification, reducing soil fertility, but also causes nitrogen, phosphorus and other elements in chemical fertilizers to flow into rivers and lakes with rainwater, causing eutrophication of water bodies, resulting in ecological disasters such as blue algae outbreaks and the death of fish and shrimp. In addition, the excessive use of pesticides has also led to increased pest resistance, and pesticide residues can also contaminate agricultural products and threaten human health. Therefore, in order to meet the needs of sustainable development, the use of fertilizers must strictly follow two major principles: (1) ensure that no harmful substances remain in agricultural products to protect the health of consumers; (2) ensure that the use of fertilizers does not have a negative impact on crop growth and the ecological environment.

[0003] Bananas are an important dual-use fruit and grain crop, widely cultivated in tropical and subtropical regions. They provide a source of income for smallholder farmers in approximately 150 tropical and subtropical countries. Bananas are also a highly popular fruit, consumed as a staple food in many countries. They rank first globally in fresh fruit trade and are the fourth-largest food crop after rice, wheat, and corn. Bananas are a rich source of important plant nutrients, including vitamins and phenolic compounds, and possess high medicinal value and processing potential. With rising living standards and increasing health awareness, demand for bananas is increasing annually. Increasing banana yields is crucial for improving the economic benefits of the banana industry. The negative impacts of excessive fertilizer use and high production costs in current agricultural production are becoming increasingly prominent, necessitating the urgent need to create more sustainable agricultural systems. This requires methods that promote banana growth, avoiding environmental pollution caused by excessive pesticide and fertilizer application, minimizing resource waste, and reducing production costs. An effective and feasible alternative approach is the development of environmentally friendly growth-promoting microbial agents, laying the foundation for the green and sustainable development of the banana industry. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a Trichoderma aculeatus-Bacillus synthetic bacterial consortium and a construction method and application thereof.

[0005] The first aspect of the present invention is to provide a Bacillus cereus, the Bacillus cereus is named Bacillus cereus It is registered and deposited in Guangdong Provincial Microbiological Culture Collection Center with the deposit number GDMCC NO: 66395.

[0006] The second aspect of the present application provides a fermentation broth of Bacillus cereus as described in the first aspect of the present application.

[0007] The third aspect of the present application provides a synthetic microbial flora comprising Bacillus cereus as described in the first aspect of the present application and Trichoderma aculeatum, which is named as Trichoderma aculeatum (T. Trichoderma asperellum ) MM7, and was preserved in the China Center for Type Culture Collection (CCTCC) on March 30, 2021, with a preservation number of CCTCC NO: M 2021302.

[0008] The method for constructing the synthetic microbial flora comprises the following steps: respectively taking a fermentation broth containing Bacillus cereus and a fermentation broth containing Trichoderma aculeatum, and inoculating into PDB medium to obtain the synthetic microbial flora.

[0009] The fourth aspect of the present application provides a mixed microbial agent comprising the synthetic microbial flora as described in the third aspect of the present application.

[0010] The fifth aspect of the present application provides a microbial bacterial fertilizer comprising Bacillus cereus as described in the first aspect of the present application, or the synthetic microbial flora as described in the third aspect of the present application, or the mixed microbial agent as described in the fourth aspect of the present application.

[0011] The sixth aspect of the present application provides an application of Bacillus cereus as described in the first aspect of the present application, or the fermentation broth as described in the second aspect of the present application, or the synthetic microbial flora as described in the third aspect of the present application, or the mixed microbial agent as described in the fourth aspect of the present application, or the microbial bacterial fertilizer as described in the fifth aspect of the present application in the preparation of a preparation for promoting the growth of bananas and / or promoting the germination of corn seeds.

[0012] The seventh aspect of the present application provides an application of Bacillus cereus as described in the first aspect of the present application, or the fermentation broth as described in the second aspect of the present application, or the synthetic microbial flora as described in the third aspect of the present application, or the mixed microbial agent as described in the fourth aspect of the present application, or the microbial bacterial fertilizer as described in the fifth aspect of the present application in the preparation of a preparation for increasing the chlorophyll content of bananas, and / or increasing the plant height of bananas, and / or increasing the stem diameter of bananas, and / or increasing the leaf area of bananas, and / or increasing the fresh weight of bananas, and / or increasing the dry weight of bananas, and / or increasing the germination rate of corn seeds, and / or increasing the length of corn seed germination.

[0013] The eighth aspect of the present application provides an application of Bacillus cereus as described in the first aspect of the present application, or the fermentation broth as described in the second aspect of the present application, or the synthetic microbial flora as described in the third aspect of the present application, or the mixed microbial agent as described in the fourth aspect of the present application in the preparation of a biological fertilizer.

[0014] The ninth aspect of the present application provides the use of the Bacillus cereus according to the first aspect of the present application or the fermentation liquor according to the second aspect of the present application in the preparation of a preparation for producing IAA and / or promoting the growth of Trichoderma asperellum MM7.

[0015] The Bacillus cereus of the present application can produce IAA, has good effects of promoting the growth of Trichoderma asperellum MM7 and promoting the growth of plants, can improve the chlorophyll content, plant height, stem diameter, leaf area, fresh weight and dry weight of plants, and has better effects of promoting the growth of banana plants, significantly improving the chlorophyll content, plant height, stem diameter, leaf area, fresh weight and dry weight of plants, and can be used to prepare a mixed microbial agent or a microbial fertilizer, which is conducive to the improvement of economic benefits of banana planting industry, has a wide application space in the green and sustainable development of banana industry, and has a wide development and application prospect in the field of microbial agents or microbial fertilizers. Trichoderma asperellum )MM7, can significantly improve the chlorophyll content, plant height, stem diameter, leaf area, fresh weight and dry weight of plants, and can be used to prepare a mixed microbial agent or a microbial fertilizer, which is conducive to the improvement of economic benefits of banana planting industry, has a wide application space in the green and sustainable development of banana industry, and has a wide development and application prospect in the field of microbial agents or microbial fertilizers. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A phylogenetic tree of Bacillus cereus CSH-9.

[0017] Figure 2 MM7+CSH-9 synthetic microbial flora plate interaction test, the left figure is inoculated with MM7, and the right figure is inoculated with MM7+CSH-9.

[0018] Figure 3 Spore quantity after co-culture of MM7+CSH-9.

[0019] Figure 4 Influence of MM7+CSH-9 synthetic microbial flora on corn seed germination. A, germination state of corn seeds under different treatments; B, germination rate of corn seeds under different treatments; C, length of corn seedlings under different treatments.

[0020] Figure 5 Effects of different microbial fertilizers on the growth of banana plants. Among them, CK is the treatment group CK (only watering); 9 is the treatment group T1 (only applying CSH-9); M7 is the treatment group T2 (only applying MM7); 9+M7 is the treatment group T3 (applying CSH-9 and MM7 in combination).

[0021] The Bacillus cereus (strain number CSH-9) according to the present application is named Bacillus cereus , and was deposited in the Guangdong Microbial Culture Collection Center (GDMCC) on May 26, 2025, with the deposit number GDMCC NO: 66395, and the deposit address is the 5th floor of Building 59, Guangdong Academy of Sciences, 100 Middle Liangxie Road, Guangzhou. DETAILED DESCRIPTION

[0022] The present application will be further described in connection with the following specific examples and in comparison with the accompanying drawings so as to have a better understanding of the present application. In the examples, the specific techniques or conditions not mentioned are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The reagents or instruments used, if not specified by the manufacturer, are all conventional products that can be commercially available.

[0023] Bacillus cereus (Bacillus cereus) Bacillus cereus Strain CSH-9 was isolated from a banana rhizosphere soil sample collected from Haikou, Hainan, China (110°10' 41''E, 20°04' 52''N), named Bacillus cereus , and deposited at the Guangdong Microbial Culture Collection Center (GDMCC) on May 26, 2025, with the accession number GDMCC NO: 66395, and the address of the deposit is at the 5th floor of Building 59, Academy of Microbiology, Guangdong Academy of Sciences, 100 Middle Liangma Street, Guangzhou.

[0024] The colony morphology of strain CSH-9 was observed. The strain was inoculated on LB medium and activated, and then incubated at 37°C in a bacterial incubator for 48 h. After single colonies grew, the colony morphology was observed. The colonies of strain CSH-9 on LB medium were grayish white, nearly round, relatively densely distributed, rough on the surface, with clear but irregular edges, and some colonies had a tendency to merge.

[0025] The physiological and biochemical characteristics of strain CSH-9 were analyzed according to the methods of "Common Bacteria System Identification Manual" and "Berger Bacteria Identification Manual", and the results are shown in Tables 1 and 2.

[0026] Table 1 Physiological and biochemical characteristics of strain CSH-9 Characteristics Results Hydrogen sulfide - Gelatin liquefaction - Cellulose decomposition - Nitrate reduction ＋ Siderophore + pH tolerance test 6-10 (optimum 7) NaCl tolerance test (%) 1-3 (optimum 1) Starch hydrolysis - Phosphorus solubilization - Nitrogen fixation - Potassium solubilization - Note: "+" result is positive; "-" result is negative.

[0027] Table 2 Single carbon source and nitrogen source utilization Carbon source utilization Results Nitrogen source utilization Results Myo-inositol + Salicin + Dextrin + Histidine + L-arabinose + Thionine - L-rhamnose + Glutamic acid - D-galactose + Potassium nitrate - D-sorbitol - Valine - D-trehalose + L-asparagine + Xylan + Glycine + D-fructose + Tyrosine - D-mannobiose + Cysteine + Raffinose - Phenylalanine - Sucrose - Proline + Ribose + L-tyrosine - D-cellubiose - Note: "+" indicates good growth; "-" indicates weak growth.

[0028] The bacteria preserved in glycerol were reactivated with LB solid medium, and single colonies were picked up with a loop and inoculated into king B liquid medium containing 100 mg / L tryptophan in a clean bench, and then incubated at 30°C, 160 r / min in a shaker for 24 h. The IAA production activity of strain CSH-9 was tested. The specific operation is as follows: (1) Preliminary screening Take 1 mL of fermentation broth in a test tube, add 2 mL of Salksowski color developing liquid (1 mL of 0.5 mol / L FeCl3 and 50 mL of 35% perchloric acid mixed), wrap with tin paper, and place in the dark for 30 min. Observe whether it turns pink, and the deeper the red color, the higher the IAA yield (Glickmann et al., 1995).

[0029] (2) Rescreening The fermentation broth was centrifuged at 8000 r / min for 10 min, and then the supernatant was taken. An equal volume of Salkowski colorimetric solution was added, repeated three times, and placed in the dark for 30 min to develop color before measuring the OD530 value. Then the content of IAA was calculated according to the standard curve.

[0030] Prepare the IAA standard curve: weigh 0.01 g of analytical pure IAA on an analytical balance and add it to 100 ml of water to make a 100 µg / mL stock solution. Then use the stepwise dilution method to obtain standard solutions with concentrations of 0, 10, 20, 30, 40, 50, 60, 80, and 100 mg / L.

[0031] Through the color reaction of IAA with Salksowski reagent, it was found that the color change during the color development process was small. Further rescreening was carried out for quantitative determination, and the concentration of IAA produced by CSH-9 was calculated to be 98.14 mg / L according to the standard relationship curve.

[0032] Universal primers 27F (5ʹ-AGAG TTTG ATCC TGGC TCAG-3ʹ) and 1492R (5ʹ-TACG GCTACCTT GTTA CGAC TT-3ʹ) were used for PCR amplification. The PCR reaction system is shown in Table 3, and the PCR amplification reaction conditions are shown in Table 4. After purification, the gene sequence was determined, and the measured 16S rRNA gene sequence was compared with the known 16S rRNA sequence stored in the public database GenBank and EzBiocloud server (https: / / www.EzBiocloud.net / identify) (Kim et al., 2012). Twenty standard strains with high homology were selected, and a neighbor-joining method was used to construct a phylogenetic tree using MEGA version X software ( Figure 1 ). Strain CSH-9 was determined to be Bacillus, and had a high homology with standard strain Bacillus cereusATCC 14579 (AE016877) was the closest relative, and combined with the results of morphological, cultural, physiological and biochemical characteristics, CSH-9 was further identified as Bacillus cereus.

[0033] Table 3 PCR reaction system for Bacillus cereus CSH-9 16S rRNA sequence Reaction system Volume Template DNA 1 μL 2x Taq PCR MasterMix 12.5 μL Upstream primer 27F 0.5 μL Downstream primer 1492R 0.5 μL ddH2O 10.5 μL Total volume 25 μL Table 4 PCR amplification reaction conditions for Bacillus cereus CSH-9 16S rRNA sequence

[0034] Example 2 Trichoderma aspergillus-Bacillus synthetic bacterial consortium

[0035] 1 Test materials

[0036] 1.1 Test instruments and equipment The main instruments and equipment required for this experiment are shown in Table 5.

[0037] Table 5 Instruments and equipment Name Model Manufacturer Biochemical incubator SPX-150 Beijing Hengrui Tianchuang Electromechanical Equipment Co., Ltd. pH meter Delta 320 Mettler-Toledo Instruments Constant temperature water bath HHS-11-2 Hangzhou Hui'er Instrument Co., Ltd. High-pressure steam sterilization pot HVE-2510 HIRAYAMA, Japan PCR amplifier TAdvanced 96 SG Biometra, Germany Gel imaging analysis system UVP EC3 UVP, USA Horizontal electrophoresis apparatus HR / 022 Beijing Hengrui Tianchuang Electromechanical Equipment Co., Ltd. Scanning electron microscope Sigma VP Zeiss, Germany Electric heating air drying oven DHG-9140A Shanghai Yiheng Scientific Instruments Co., Ltd. Single-person single-sided horizontal clean bench SW-CF-1F Suzhou Suji Purification Equipment Co., Ltd. Tabletop refrigerated centrifuge ST16R Thermo, Germany Laser confocal laser microscope ZEISS Axio Scope A1 Carl Zeiss, Germany

[0038] 1.2 Main culture medium The main culture media tested in this study are shown in Table 6.

[0039] Table 6 Main culture media and formulas Culture medium name Culture medium formula Potato glucose agar (PDB) Potato 200.0 g, glucose 20.0 g, water 1000 mL. LB medium Yeast powder 5 g, tryptone 10 g, NaCl 10 g, agar 20 g, water 1000 mL, pH 7.2~7.5

[0040] 1.3 Banana seedlings for testing The banana tissue culture seedlings are all healthy Brazilian banana cup seedlings with relatively uniform growth and 3-4 leaves, provided by the Danzhou Tissue Culture Center of the Chinese Academy of Tropical Agricultural Sciences.

[0041] 1.4 Test soil The soil used in the experiment was red loam from a banana plantation in Danzhou City, Hainan Province (109°54'66"E, 19°44'63"N).

[0042] 1.5 Information on the functional strains tested The test strains for this experiment are shown in Table 7.

[0043] Table 7 Information of tested strains Strain number Species Classification Function Source CSH-9 Bacillus cereus Bacteria Ability to reduce nitrate; growth promotion Isolated from banana rhizosphere soil MM7 Trichoderma asperellum Fungi Predation of banana wilt; growth promotion Isolated from banana rhizosphere soil Trichoderma aculeatus ( Trichoderma asperellum) MM7, deposited at China Center for Type Culture Collection on March 30, 2021, with the accession number CCTCC NO: M2021302, located at Wuhan University, Wuhan, Hubei, China. Isolated from banana rhizosphere soil. See Chinese patent application No. 202111570689.8, entitled "Trichoderma asperellum for predating Fusarium oxysporum f. sp. cubense and application thereof" for the mycological characteristics of Trichoderma asperellum MM7 and the like.

[0044] 2 Test method and result

[0045] 2.1 Construction of synthetic microbial consortium Prepare PDA medium, sterilize at 121 ℃ for 20 min, and then use. Draw a line in the center of the PDA plate, and then connect CSH-9 to the middle of the central line. After 2 days of culture at 28 ℃, connect MM7 to the middle position. The control group is inoculated with MM7 alone on the sterilized PDA medium. Invert and culture at 28 ℃ for 5 days, and observe the growth of each strain to confirm whether each functional strain can coexist.

[0046] As shown in Figure 2 , it is found that CSH-9 can coexist well with MM7, and there is no antagonism between them. The coexistence is strong, and it is suitable for constructing a stable functional microbial synthetic microbial consortium.

[0047] 2.2 Co-culture of synthetic microbial consortium Seed liquid culture: pick fresh colonies of CSH-9 and MM7 from the plate, inoculate in LB and PDB liquid medium respectively, CSH-9 is cultured overnight at 37 ℃, 180 rpm / min on a shaker, and MM7 is cultured for 3 days at 28 ℃, 180 rpm / min on a shaker.

[0048] The fresh seed liquid of CSH-9 and MM7 cultured is inoculated into PDB liquid medium at a ratio of 1:1 for co-culture, MM7 cultured alone is used as a control, and it is cultured at 28 ℃, 180 rpm / min on a shaker. After 3 days and 5 days of culture, the number of spores of MM7 is counted under a microscope by using a hemocytometer.

[0049] As shown in Figure 3 , co-culture of CSH-9 and MM7 can significantly increase the number of spores of MM7, and this promoting effect exists on the 3rd day and the 5th day. In the MM7 treatment group, the number of spores on the 3rd day is about 40 spore / mL, and on the 5th day it is about 85 spore / mL; while in the MM7+CSH-9 treatment group, the number of spores on the 3rd day is about 90 spore / mL, and on the 5th day it is about 250 spore / mL. It shows that the addition of CSH-9 can significantly promote the growth of MM7.

[0050] 2.3 Preparation of synthetic microbial flora Preparation of raw materials: potato, glucose, microbial agent (as shown in Table 8).

[0051] A single colony of CSH-9 was inoculated into a king B liquid medium containing 100 mg / L tryptophan and incubated at 30°C, 160 rpm / min for 24 h to obtain a CSH-9 fermentation broth.

[0052] MM7 cake was inoculated into PDB medium and incubated at 30°C, 160 rpm / min for 24 h to obtain a MM7 fermentation broth.

[0053] PDB liquid medium was prepared and divided into 250 mL flasks, sterilized at 121°C for 20 min, and then inoculated with fresh test strains at a ratio of 1% of the medium volume (V / V) according to the strain combination in Table 8. After incubation at 28°C for 5-7 days at 180 rpm / min, the synthetic microbial flora was prepared.

[0054] Table 8 Strain combination Strain number Strain combination Proportion of effective viable bacteria of inoculated bacteria CK No bacteria added / T1 MM7 100% T2 CSH-9 100% T3 MM7 + CSH-9 50%；50%

[0055] 2.4 Synthetic microbial flora promotes seed germination experiment In this experiment, corn seeds were used as materials to evaluate the ability of synthetic microbial flora to promote seed germination. The corn seeds were purchased from China Haikou Chengmai Agricultural Supply Store. After washing and sterilizing, the corn seeds were placed on filter paper in a culture dish. The above T1, T2, T3 fermentation broth was diluted 10 times with sterile water, and then the sterilized corn seeds were treated as follows (each treatment group contained 30 seeds, with 3 replicates): the glass culture dish containing corn seeds was incubated at 26±1°C, and 3 mL of each treatment liquid was sprayed on the filter paper every day to keep the seeds moist. The physiological changes of the seeds were recorded, and the whole experiment was conducted under controlled conditions using a completely randomized design.

[0056] To further explore the potential of synthetic microbial flora to promote seed germination, the germination rate and germination length of corn seeds were counted after 7 days. The results are shown in Figure 4 Figure 4 A, 4B). The germination length also showed similar differences Figure 4 ​C). The average germination length of corn seeds in the T3 treatment group was 12.20 cm, which was significantly higher than that in the T2 treatment group (4.88 cm), the T1 treatment group (6.25 cm), and the control group (8.27 cm); the average germination length of corn seeds in the control group was significantly higher than that in the T1 treatment group and the T2 treatment group. In summary, the synthetic microbial consortium plays an important role in promoting corn seed germination.

[0057] 2.5 Pot experiment

[0058] 2.5.1 Cultivation of banana The pot experiment was conducted at the Institute of Tropical Biological Science and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, from April to May 2025. The greenhouse conditions were 25°C, 75% humidity, and natural light. Healthy soil from a banana field in Danzhou, Hainan Province, was collected and sieved to 20 mesh. Banana seedlings with consistent growth and 3-4 leaves were selected, washed clean with sterile water, and planted in plastic pots containing 1400 g of soil, with 30 plants per treatment. Four treatment groups were set up: CK: water only; T1: MM7 alone; T2: CSH-9 alone; T3: combined application of CSH-9 and MM7. Every 7 days, 100 mL of each treatment was applied after 10-fold dilution, and other management measures were consistent during the experiment. Sampling was conducted after two months of treatment.

[0059] 2.5.2 Measurement of banana seedling physiological indicators The physiological indicators of banana seedlings after transplanting were measured according to the method of Chen et al. (2018), including chlorophyll content, plant height, stem diameter, leaf area, fresh weight, and dry weight.

[0060] (1) Measurement of chlorophyll content in banana seedlings The SPAD-502 portable chlorophyll meter was used for measurement. The second unfolded leaf at the top of the banana seedling was selected, and the chlorophyll content was measured at the bottom, middle, and upper edge of both sides of the leaf.

[0061] The content of chlorophyll in leaves is closely related to the healthy growth of banana plants, because it is directly related to photosynthesis. When banana plants are diseased, the synthesis of chlorophyll in leaves will be disturbed, or even destroyed, reducing the efficiency of photosynthesis of the plant and inhibiting the growth and development of the plant. The experimental results of the effects of different bacterial flora treatments on the chlorophyll content of banana seedling leaves are shown in Table 9. Compared with CK, the chlorophyll content of T1, T2 and T3 treatments all had significant differences, among which the difference of T3 treatment was more significant, and the chlorophyll content was 48.94 mg / g, which was 1.11 times that of T1 and T2. The results showed that CSH-9 and MM7 could significantly increase the chlorophyll content of banana leaves, and the synthetic bacterial flora of the two was more conducive to increasing the chlorophyll content of banana leaves, indicating that CSH-9 and MM7 could effectively increase the chlorophyll content of leaves, enhance the photosynthetic efficiency of the plant, and promote the healthy growth of the plant.

[0062] Table 9 Effects of different bacterial flora treatments on chlorophyll content and leaf area of banana Treatment Chlorophyll content (mg / g) Leaf area (cm 2 / plant) CK 40.92 ± 0.88c 239.26 ± 4.82b T1 44.12 ± 0.79b 428.78 ± 10.18a T2 44.18 ± 0.67b 412.52 ± 8.58a T3 48.94 ± 0.92a 461.01 ± 10.19a Note: Different lowercase letters after each column indicate significant differences (P<0.05) between different treatments (2) Leaf area of banana seedlings The leaf area of banana seedlings was obtained by the formula of banana seedling leaf area of Chen Zhijie (2018), and the third unfolded leaf on the top of the banana seedling was selected, and the formula was: leaf length x leaf width x 0.75. The leaf length is the distance from the leaf base to the leaf tip, and the leaf width is the distance between the two sides of the widest part of the middle of the leaf.

[0063] The size of the leaf area of the plant is an important trait in the growth process of the plant, which directly affects the photosynthetic effect of the plant, and has key significance to the physiological function, ecological adaptation and agricultural production of the plant. As can be seen from Table 9, the leaf area of T1, T2 and T3 treatments was significantly higher than that of CK, among which the leaf area of T3 treatment was the largest, which was 461.01 cm 2 . Comprehensive analysis, T1 and T2 treatments can significantly improve the chlorophyll content and leaf area of the plant, and the effects of the two are equivalent; while T3 treatment has the best effect in improving the chlorophyll content and increasing the leaf area, which is significantly better than other treatments, indicating that there may be a synergistic effect between the two, which has great potential in promoting plant growth. The size of the leaf area of the plant is an important trait in the growth process of the plant, which directly affects the photosynthetic effect of the plant, and has key significance to the physiological function, ecological adaptation and agricultural production of the plant. As can be seen from Table 9, the leaf area of T1, T2 and T3 treatments was significantly higher than that of CK, among which the leaf area of T3 treatment was the largest, which was 461.01 cm 2chlorophyll content and leaf area, and both of them had similar effects. The T3 treatment had the best effect on increasing chlorophyll content and leaf area, and was significantly better than other treatments, which indicated that there might be a synergistic effect between the two, and they had great potential in promoting plant growth. The size of plant leaf area is an important trait in the process of plant growth, which directly affects the photosynthesis effect of plants, and has key significance for the physiological function, ecological adaptation and agricultural production of plants. As shown in Table 9, the leaf area of T1, T2 and T3 treatments was significantly higher than that of CK, and the leaf area of T3 treatment was the largest, which was 461.01 cm 2 chlorophyll content and leaf area, and both of them had similar effects. The T3 treatment had the best effect on increasing chlorophyll content and leaf area, and was significantly better than other treatments, which indicated that there might be a synergistic effect between the two, and they had great potential in promoting plant growth. The size of plant leaf area is an important trait in the process of plant growth, which directly affects the photosynthesis effect of plants, and has key significance for the physiological function, ecological adaptation and agricultural production of plants. As shown in Table 9, the leaf area of T1, T2 and T3 treatments was significantly higher than that of CK, and the leaf area of T3 treatment was the largest, which was 461.01 cm 2 chlorophyll content and leaf area, and both of them had similar effects. The T3 treatment had the best effect on increasing chlorophyll content and leaf area, and was significantly better than other treatments, which indicated that there might be a synergistic effect between the two, and they had great potential in promoting plant growth.

[0064] (3) Stem diameter of banana seedlings The stem diameter of banana seedlings was measured at 3 cm from the potting substrate using a vernier caliper with the smallest scale of 0.01.

[0065] As shown in Table 10, the stem diameter of banana seedlings treated with different microbial populations increased to some extent, and the stem diameter of banana seedlings treated with T1, T2 and T3 was significantly different from that of CK. The stem diameter of banana seedlings treated with T3 was the largest, which was 21.83 mm, and was significantly higher than that of other treatments. Therefore, T1 and T2 could significantly increase the stem diameter of banana seedlings, and both of them had similar effects. The T3 treatment had the best effect on increasing the stem diameter of banana seedlings, which indicated that CSH-9 and MM7, especially the synthetic microbial population, had good growth-promoting effect, and could significantly increase the stem diameter of banana seedlings.

[0066] (4) Fresh weight and dry weight of banana seedlings The banana seedlings were washed with clean water, dried on newspaper, and the fresh weight of the banana seedlings was measured. The banana seedlings with measured fresh weight were placed in an oven at 80°C for 3 days, and then taken out for weighing.

[0067] As shown in Table 10, the dry weight and fresh weight of banana plants on each treatment group remained consistent. Compared with CK, the fresh weight and dry weight of T1, T2 and T3 treatments were significantly different, and the fresh weight and dry weight of T3 treatment were the highest, reaching 128.18 g and 26.63 g, respectively, which were significantly higher than those of other treatments, and increased by 50.64% and 77.30%, respectively, compared with the control. Therefore, CSH-9 and MM7, especially the synthetic microbial flora of the two, can significantly improve the biomass of banana, which is suitable for subsequent production and utilization.

[0068] (5) Height of banana seedlings The height of banana seedlings was measured from the surface of the potted substrate to the intersection of the top expanded leaf petiole and pseudostem with a minimum scale of 0.1 cm ruler.

[0069] As shown in Table 10, there was a significant difference in the height of banana seedlings treated with different microbial flora, and the height of banana seedlings treated with different microbial flora was significantly higher than that of the sterile fertilizer treatment. The height of banana seedlings treated with T3 was the highest, which was significantly higher than that of other treatments, reaching 20.40 cm, which increased by 64.38% compared with the control. Therefore, CSH-9 and MM7, especially the synthetic microbial flora of the two, have the best growth-promoting effect on banana.

[0070] Table 10 Effect of different microbial flora on the growth of banana Treatment Plant height (cm) Stem diameter (mm) Fresh weight (g·plant -1 )]]> Dry weight (g·plant -1 )]]> CK 12.41 ± 0.28d 14.15 ± 0.28c 85.09 ± 2.34c 15.02 ± 0.94c T1 17.24 ± 0.26c 18.16 ± 0.43b 99.06 ± 1.01b 19.35 ± 0.37b T2 18.83 ± 0.26b 18.73 ± 0.36b 106.15 ± 2.67b 17.58 ± 0.40b T3 20.40 ± 0.36a 21.83 ± 0.35a 128.18 ± 3.31a 26.63 ± 0.37a Note: Different lowercase letters after each column indicate significant difference (P<0.05) between different treatments The above detailed description of the specific embodiments of the present application, but it is only as an example, the present application is not limited to the above described specific embodiments. For those skilled in the art, any equivalent modification and alternative to the present application are also within the scope of the present application. Therefore, any equivalent transformation and modification without departing from the spirit and scope of the present application should be covered within the scope of the present application.

Claims

1. A Bacillus cereus, characterized in that Named Bacillus cereus It is registered and deposited in Guangdong Provincial Microbiological Culture Collection Center with the deposit number GDMCC NO: 66395.

2. The fermentation liquid of Bacillus cereus as claimed in claim 1.

3. A synthetic bacterial community, characterized in that: Contains the Bacillus cereus and Trichoderma aculeatus according to claim 1, wherein the Trichoderma aculeatus is named Trichoderma aculeatus ( Trichoderma asperellum )MM7, deposited in the China Center for Type Culture Collection on March 30, 2021, with the deposit number CCTCC NO: M 2021302.

4. The method for preparing a synthetic bacterial consortium according to claim 3, wherein: The following steps are involved: The fermentation liquid of the strain containing Bacillus cereus and the fermentation liquid of the strain containing Trichoderma aspergillus are respectively taken, inoculated into PDB culture medium, and cultured to obtain the product.

5. A mixed bacterial agent, characterized in that: Contains the synthetic bacterial flora according to claim 3.

6. A microbial fertilizer comprising the Bacillus cereus according to claim 1, or the fermentation liquid according to claim 2, or the synthetic bacterial consortium according to claim 3, or the mixed bacterial agent according to claim 5.

7. Application of Bacillus cereus as claimed in claim 1, or the fermented liquid as claimed in claim 2, or the synthetic flora as claimed in claim 3, or the mixed bacterial agent as claimed in claim 5, or the microbial fertilizer as claimed in claim 6 in preparing a preparation for promoting banana growth and / or promoting corn seed germination.

8. bacillus cereus as claimed in claim 1, or the fermented liquid as claimed in claim 2, or the synthetic flora as claimed in claim 3, or the mixed microbial agent as claimed in claim 5, or the microbial fertilizer as claimed in claim 6 are used in the preparation of improving banana chlorophyll content, and / or improving banana plant height, and / or improving banana stem thickness, and / or improving banana leaf area, and / or improving banana fresh weight, and / or improving banana dry weight, and / or improving corn seed germination rate, and / or improving corn seed germination length.

9. Use of the Bacillus cereus according to claim 1, or the fermentation liquid according to claim 2, or the synthetic bacterial consortium according to claim 3, or the mixed bacterial agent according to claim 5 in the preparation of a biofertilizer.

10. Use of the Bacillus cereus according to claim 1 or the fermentation broth according to claim 2 in preparing a preparation for producing IAA and / or promoting the growth of Trichoderma aspergillus MM, wherein the Trichoderma aspergillus is named Trichoderma aspergillus ( Trichoderma asperellum )MM7, deposited in the China Center for Type Culture Collection on March 30, 2021, with the deposit number CCTCCNO: M 2021302.

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