A strain of chaetomium aureum ff21 promoting blueberry growth and application thereof

Abstract

The application discloses a strain of Chaetomium aureum FF21 for promoting growth of blueberries and application of the strain, the taxonomic name of the Chaetomium aureum FF21 is Arcopilus aureus, and the Chaetomium aureum FF21 is preserved in the China General Microbiological Culture Collection Center on September 19, 2024, and the preservation number is CGMCC No. 41521. The Chaetomium aureum FF21 has the functions of increasing the contents of soluble sugar, SOD enzyme, PPO enzyme and total phosphorus in blueberry plants, so that the growth of blueberry seedlings is promoted, and the Chaetomium aureum FF21 has great potential to be developed into a microbial agent.

Description

Technical Field

[0001] This invention belongs to the field of agricultural microbial technology and relates to a strain of golden chamomile FF21 that promotes blueberry growth and its application. Background Technology

[0002] blueberry( Vaccinium uliginosum ) belongs to the genus Vaccinium of the family Ericaceae ( Vaccinium Blueberries are a common name for blueberry-type plants. Wild blueberries are widely distributed throughout the world. They are mainly produced in the United States, and in China, they are primarily found in the Greater and Lesser Khingan Mountains forest areas. As a new fruit with high economic value and health benefits, blueberry cultivation has seen significant growth. However, most growers currently lack experience in greenhouse blueberry cultivation. Although tissue culture propagation systems for many blueberry varieties have been established, problems such as difficulty in seedling rooting and low transplant survival rates remain, becoming major obstacles to the large-scale tissue culture propagation of blueberry seedlings.

[0003] Blueberries are shallow-rooted, rootless plants that naturally form a mutualistic symbiotic relationship with symbiotic fungi. These fungi enhance plant growth, improve the root environment, and increase resistance to pests and diseases. Rhizosphere growth-promoting fungi are beneficial fungi that grow in the rhizosphere soil of plants and have various growth-promoting mechanisms, such as biological nitrogen fixation, phosphorus and potassium solubilization, production of plant hormones like IAA, antagonism of pathogens, and induction of systemic resistance. In particular, these fungi can increase the levels of osmotic regulators (such as sugars) during metabolism. Furthermore, the organic acids they produce can dissolve insoluble phosphorus in the soil, promoting plant growth and development. They can also improve soil circulation by increasing oxidase levels, thus promoting blueberry seedling growth. Research on blueberry growth promotion using blueberry root symbiotic fungi is an important aspect of the development of the blueberry green industry. Dark septate endophytes (DSEs) are a major group of plant endophytes, characterized by their ability to form dark-colored hyphal structures with distinct septa after forming a symbiotic relationship with plant roots. These structures create "microsclerotia" within plant cells and intercellular spaces. DSEs colonize the epidermis, cortex, and even the intercellular spaces of vascular tissues in healthy plant roots, forming symbionts, but they do not contribute to the pathological features caused by pathogens within healthy root tissues. DSEs have a wide host range and ecological distribution, primarily found in arid, cold, and heavy metal-polluted areas, as well as in specific habitats and unique plant species. They exhibit no host specificity and are highly adaptable. DSEs may possess functions similar to mycorrhizal fungi, establishing a mutually beneficial symbiotic relationship with their hosts and playing a crucial role in promoting plant growth, improving mineral absorption, controlling biological diseases, and enhancing plant stress resistance. *Chaetomium aureum*, a genus of dark septate endophytes, is specifically used for decomposing cellulose and exhibits broad-spectrum antagonism and good stress resistance. In the past, it has been mostly used for the prevention and control of diseases and pests, but there have been no reports on its development for the rapid growth of tissue culture seedlings, especially for promoting the growth of blueberry seedlings. Summary of the Invention

[0004] The purpose of this invention is to provide a *Chaetoceros fulvidracoides* strain FF21 that promotes blueberry growth and its applications. The *Chaetoceros fulvidracoides* strain FF21 of this invention increases plant biomass and enhances the content of soluble sugars, SOD enzymes, PPO enzymes, and total phosphorus in the plant, thereby promoting the growth of blueberry seedlings.

[0005] The technical solution of this invention: A golden scab FF21 that promotes blueberry growth and its application, wherein the taxonomic name of the golden scab FF21 is... Arcopilus aureus It was deposited at the China General Microbiological Culture Collection Center on September 19, 2024, with accession number CGMCC No. 41521.

[0006] The aforementioned golden scab FF21 was obtained from blueberry roots using a tissue isolation method.

[0007] The aforementioned tissue separation method is performed according to the following steps:

[0008] (1) Cleaning and disinfection: Select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to the ultra-clean workbench, immerse them in 75% ethanol solution for 2-4 seconds, rinse them with sterile water 4-6 times, disinfect them with 75% ethanol for 20-40 seconds, rinse them with sterile water 4-6 times and dry them to obtain product A;

[0009] (2) Culture, isolation and purification: Place the A-grade PDA medium in a constant temperature incubator at 28℃ for 3-5 days. After dark septate hyphae grow in the culture dish, pick the edge hyphae and transfer them to a new PDA culture dish for further culture. Repeat this process 3-5 times to obtain a pure culture strain, which is the golden scab FF21.

[0010] In the aforementioned step (1), cleaning and disinfection: select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to the ultra-clean workbench, soak them in 75% ethanol solution for 3 seconds, rinse them 5 times with sterile water, disinfect them with 75% ethanol for 30 seconds, rinse them 5 times with sterile water and dry them to obtain product A.

[0011] In step (2) above, the PDA culture medium is prepared by dissolving 200g of potato, 20g of glucose and 20g of agar in 1000mL of distilled water, with a natural pH.

[0012] A blueberry growth promoter comprising the aforementioned *Chaetoceros aubergine* FF21.

[0013] The aforementioned application of *Chaetoceros augrass* FF21, specifically its application in the preparation of formulations that promote blueberry growth.

[0014] A blueberry growth promoter product, wherein the active ingredient of the product includes the described Chaetomium aureum FF21.

[0015] A blueberry growth-promoting bacteria product, wherein the active ingredient of the product is the aforementioned Chaetoceros FF21.

[0016] A method for preparing a blueberry growth-promoting bacteria product, using the aforementioned *Chaetoceros aubergine* FF21 as an active ingredient or one of the active ingredients in the preparation of the product.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention discloses a strain of Chaetoceros FF21 and its application in promoting blueberry growth. Chaetoceros FF21 is isolated and cultured from blueberry roots using a tissue isolation method. Chaetoceros FF21 is then inoculated into blueberry potted seedlings. This strain of Chaetoceros FF21 can colonize blueberry roots and has no negative impact on the growth of blueberry seedlings.

[0019] 2. Biomass analysis results of blueberry plants using *Chaetoceros aubergine* FF21 showed that it increased the above-ground height of blueberry seedlings from 28.33cm to 36.00cm, and the ground diameter from 4.71cm to 6.92cm; the above-ground fresh weight increased from 4.98g to 8.61g, the underground fresh weight increased from 1.01g to 2.51g, the above-ground dry weight increased from 2.13g to 3.69g, and the underground dry weight increased from 0.57g to 1.18g.

[0020] 3. Results from the analysis of physiological indicators of blueberry plants by *Chaetoceros aubergine* FF21 showed that it increased the soluble sugar content of blueberry seedlings to 8.38 mg / g in the aboveground parts and 15.56 mg / g in the underground parts. In addition to increasing the soluble sugar content, it also increased the content of SOD, PPO enzymes, and total phosphorus in blueberry seedlings. Specifically, the SOD enzyme content in the aboveground parts increased from 104.72 U / g to 122.59 U / g, the PPO enzyme content increased from 95.8 U / mg to 493.8 U / mg, and the total phosphorus content increased from 4.58 g / kg to 5.63 g / kg.

[0021] In summary, the blueberry golden scab FF21 of the present invention can not only effectively promote blueberry biomass, but also effectively increase the content of soluble sugar, SOD enzyme, PPO enzyme and total phosphorus in blueberry seedlings. It has great potential to promote blueberry growth and be developed into a microbial agent. Moreover, this bacterium is golden scab FF21, which can be directly isolated from blueberry root tissue culture without the need to introduce other strains. Attached Figure Description

[0022] Figure 1 Colony morphology of FF21 (A, B) and septate hyphae (C);

[0023] Figure 2 ITS-based Arcopilus aureus FF21 phylogenetic tree;

[0024] Figure 3 : Colonization at the roots of blueberry tissue culture seedlings (A: blank; B: FF21);

[0025] Figure 4Effects of FF21 inoculation on root growth of blueberry potted seedlings (A: blank; B: FF21);

[0026] Figure 5 Effects of FF21 on blueberry plant biomass (* indicates significant difference) p <0.05);

[0027] Figure 6 Effects of FF21 on blueberry plant growth (* indicates significant difference) p <0.05, ns indicates no significant difference);

[0028] Figure 7 Effects of FF21 on root activity of blueberry plants (* indicates significant difference) p <0.05);

[0029] Figure 8 Effects of FF21 on soluble sugars in blueberry plants (* indicates significant difference) p <0.05);

[0030] Figure 9 Effects of FF21 on SOD and POD enzyme activities in blueberry plants (* indicates significant difference) p <0.05, ns indicates no significant difference);

[0031] Figure 10 Effects of FF21 on total phosphorus in blueberry plants (* indicates significant difference) p <0.05). Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0033] Example 1: Tissue isolation of Chaetomium aureum FF21

[0034] (1) Cleaning and disinfection: Select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to the ultra-clean workbench, soak them in 75% ethanol solution for 3 seconds, rinse them with sterile water 5 times, disinfect them with 75% ethanol for 30 seconds, rinse them with sterile water 5 times and dry them to obtain product A.

[0035] (2) Culture, isolation and purification: Place the A-grade PDA medium in a constant temperature incubator at 28℃ for 4 days. After dark septate hyphae grow in the culture dish, pick the edge hyphae and transfer them to a new PDA culture dish for further culture. Repeat this process 4 times to obtain a pure culture strain, which is the golden scab FF21.

[0036] PDA culture medium formula: made by dissolving 200g of potato, 20g of glucose and 20g of agar in 1000mL of distilled water, with natural pH.

[0037] Example 2: Tissue isolation of Chaetomium aureum FF21

[0038] (1) Cleaning and disinfection: Select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to the ultra-clean workbench, soak them in 75% ethanol solution for 4 seconds, rinse them with sterile water 4 times, disinfect them with 75% ethanol for 40 seconds, rinse them with sterile water 6 times and dry them to obtain product A.

[0039] (2) Culture, isolation and purification: Place the A-grade PDA medium in a constant temperature incubator at 28℃ for 5 days. After dark septate hyphae grow in the culture dish, pick the edge hyphae and transfer them to a new PDA culture dish for further culture. Repeat this process 3 times to obtain a pure culture strain, which is the golden scab FF21.

[0040] PDA culture medium formula: made by dissolving 200g of potato, 20g of glucose and 20g of agar in 1000mL of distilled water, with natural pH.

[0041] Example 3: Tissue isolation of Chaetomium aureum FF21

[0042] (1) Cleaning and disinfection: Select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to the ultra-clean workbench, soak them in 75% ethanol solution for 2 seconds, rinse them with sterile water 6 times, disinfect them with 75% ethanol for 20 seconds, rinse them with sterile water 4 times and dry them to obtain product A.

[0043] (2) Culture, isolation and purification: Place the A-grade PDA medium in a constant temperature incubator at 28℃ for 3 days. After dark septate hyphae grow in the culture dish, pick the edge hyphae and transfer them to a new PDA culture dish for further culture. Repeat this process 5 times to obtain a pure culture strain, which is the golden scab FF21.

[0044] PDA culture medium formula: made by dissolving 200g of potato, 20g of glucose and 20g of agar in 1000mL of distilled water, with natural pH.

[0045] This invention has undergone extensive analytical verification experiments, and the following are the results of the experimental research of this invention:

[0046] 1. Isolation and identification of Chaetomium ff. FF21

[0047] 1.1 Isolation and identification methods for Chaetomium aureum FF21

[0048] Dark septate endophytes (DSE) were isolated and cultured from blueberry roots collected from the Huaxi Gaopo Ecological Blueberry Garden (106°50′14″E, 26°16′46″N) in Guiyang City, Guizhou Province, using a tissue isolation method. Healthy, lesion-free blueberry roots were selected, washed with clean water, and dried. In a clean bench, the roots were immersed in 75% ethanol solution for 3 seconds, rinsed 5 times with sterile water, sterilized in 3% (v / v) NaClO solution for 3 minutes, rinsed 5 times with sterile water, sterilized in 75% ethanol for 30 seconds, rinsed 5 times with sterile water again, and then blotted dry. Five blueberry root segments were placed in each PDA (potato 200g, glucose 20g, agar 20g, distilled water 1000mL) medium, repeated 20 times, and incubated at 28℃ for 3-5 days. Using the edge-picking method of fungal colonies, fungi with typical growth morphological differences were picked from PDA agar plates and transferred to PDA agar, cultured in a constant temperature incubator at 28℃, and purified 3-5 times.

[0049] Colony characteristics (colon color, shape, and edge features) were observed and photographed using a camera. Mycelial morphology and spores of the strain were observed under a microscope for morphological identification. DNA was extracted from the strain using a Fungal DNA Midi Kit. The strain sequence was obtained using universal primers ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3'), and the DNA was amplified by polymerase chain reaction (PCR). The PCR amplification products were directly sent to Chongqing Qingke Biotechnology Testing Co., Ltd. for gel cutting, purification, and sequencing.

[0050] 1.2 Isolation and identification results of Chaetomium aureum FF21

[0051] On PDA medium, the mycelium is abundant, and the colonies are golden yellow. The production of red metabolites turns both the colonies and the medium red, indicating the presence of septate mycelium. Figure 1 The ITS sequence was compared with sequences belonging to different species in the Blast alignment results using multiple sequence alignment analysis, and at the same time, multiple sequence alignment analysis was performed. Colletotrichum fructicola As an exogenous bacterium, sequence alignment was performed using ClustalW in MEGA 11.0 software, and a phylogenetic tree was constructed using the Neighbor-Joining method in MEGA 11.0. Strain FF21 was found to be located in one branch of the phylogenetic tree with 100% support, clustering into one group (…). Figure 2 Based on colony morphology and microscopic morphology, this DSE strain was identified as... Arcopilus aureus (Named as *Trichoderma aureum* FF21).

[0052] 2. Re-inoculation experiment of Chaetoceros FF21 on blueberry tissue culture seedlings

[0053] 2.1 Reconnection Test Method

[0054] The isolated golden chamomile FF21 was inoculated onto sterile blueberry seedlings and cultured for one month. The colonization of the strain was then observed under a microscope.

[0055] MEA liquid medium: 20g glucose, 3g soybean peptone, 30g malt extract, pH 5.4±0.2. Pour 200mL of MEA liquid medium into a 500mL Erlenmeyer flask and autoclave at 121℃ for 20min.

[0056] Moss culture medium: Soak the dried moss in distilled water for 24 hours, then remove the moss and remove about 50% of the water. Then, dispense the moss into tissue culture bottles, with the amount of moss occupying about 1 / 3 of the volume of the tissue culture bottle. Then, wipe the tissue culture bottles clean and sterilize them in a high-temperature and high-pressure autoclave at 121℃ for 2 hours.

[0057] The specific method is as follows: Sterilize tissue culture bottles by filling them 1 / 3 full with moss substrate. Wash the roots of the rooted blueberry tissue culture seedlings to remove any remaining agar, and transplant two seedlings into each bottle. After one week of acclimatization, add 3 ml of MEA culture medium containing a block of FF21 strain to the tissue culture bottles containing the sterile seedlings. Observe the colonization of the strain after 30 days.

[0058] Colonization observation: The sterile seedling roots were washed with distilled water, placed in 10% KOH solution at 100℃ for 1 hour for hydrolysis, transferred to a plate containing lactic acid for 10 minutes for neutralization, and then stained in 0.5% acid fuchsin for 30 seconds. After that, they were transferred to lactic acid glycerol solution (lactic acid: glycerol: distilled water = 1:1:1) for decolorization. Finally, they were placed on a glass slide and pressed to prepare a slide. The infection status of Chaetomium aureum FF21 was observed under a microscope.

[0059] 2.2 Results of the reconnection test

[0060] Compared with the control treatment, the blueberry tissue culture seedlings inoculated with *Chaetoceros augrass* FF21 showed no obvious abnormalities in growth, and dark septate hyphae could be observed in the seedling tissues inoculated with *Chaetoceros augrass* FF21 (Figure 3). This indicates that *Chaetoceros augrass* FF21 can colonize the blueberry roots and has no negative effect on the growth of blueberry seedlings.

[0061] 3. Inoculation Trial

[0062] 3.1 Method for inoculating with Chaetomium oxysporum FF21

[0063] Under aseptic conditions, five DSE bacterial cakes (d=5mm) were taken using a punch and inoculated into an autoclaved Erlenmeyer flask containing 100 ml LDB. The flasks were then incubated at 28°C and 170 rpm for 14 days. The inoculum was then broken up using a mixer to prepare 1×10⁻⁶ cells / flasks. 6 FF21 bacterial suspension at CFU / mL.

[0064] The inoculation experiment used one-year-old blueberry potted plants with two treatments: a control group (CK) and a control group (CK). One plant was inoculated with FF21 bacterial suspension in each pot, for a total of 12 experimental pots. The potted experiments were conducted in a greenhouse. Healthy, disease-free, and uniformly growing blueberry seedlings were selected and inoculated using the root wound irrigation method: a sterilized scalpel was inserted into the soil near the plant to create a root wound, and each blueberry plant was irrigated with 100 mL of FF21 bacterial suspension. Seedlings inoculated with an equal volume of sterile distilled water served as the control group. No fertilizer was applied during the growing season, and watering was carried out every three days. Harvesting was conducted after 90 days of uniform cultivation and management.

[0065] 3.2 Effects of inoculation with Chaetomium ff. FF21 on blueberry growth

[0066] The root system structure was scanned using a root scanner; biomass was measured by weighing (dry weight and fresh weight): drying time was 48 hours in a 45℃ oven; plant height and diameter at ground level were measured for each pot using a ruler and vernier calipers; soluble sugar, SOD enzyme, PPO enzyme, and total phosphorus content of blueberry seedlings were determined.

[0067] 3.2.1 Effects of inoculation with Chaetomium ff. FF21 on blueberry biomass

[0068] Blueberry potted seedlings were harvested 90 days after cultivation management according to item "3.1". The growth-promoting effect of *Chaetoceros aubergine* FF21 on blueberry potted seedlings was similar to that on tissue-cultured seedlings. Compared with the control, inoculation with FF21 significantly promoted the growth of blueberry potted seedlings. Figure 4-10 ).

[0069] Table 1. Effects of different treatments on the growth of blueberry tissue culture seedlings by *Chaetoceros aubergine* FF21.

[0070] Note: Data are mean ± standard error.

[0071] Result: From Figures 4-6 As shown in Table 1, the root growth of blueberry potted seedlings inoculated with *Chaetoceros augrass* FF21 was better than that of seedlings not inoculated with *Chaetoceros augrass* FF21.

[0072] 3.2.2 Effects of inoculation with *Chaetoceros augrass* FF21 on root vigor of blueberry plants

[0073] Blueberry potted seedlings were taken 90 days after cultivation management according to item "3.1", and root vigor was determined by TTC reduction method.

[0074] Result: See Figure 7 After using *Chaetoceros aubergine* FF21, the root activity of blueberry plants reached 13.08 μg / (g·h), an increase of 133.57% compared with the control group.

[0075] 3.2.3 Effect of inoculation with Chaetomium aureum FF21 on soluble sugars in blueberry plants

[0076] Blueberry potted seedlings were taken after 90 days of cultivation management according to item "3.1", and the soluble sugar content of the above-ground and underground parts of the blueberry plants was determined by the anthrone method.

[0077] Result: See Figure 8 After using *Chaetoceros aubergine* FF21, the soluble sugar content in the aboveground parts of blueberry plants reached 15.56 mg / g, an increase of 85.68% compared to the control group, and the soluble sugar content in the underground parts reached 8.48 mg / g, an increase of 88.84% compared to the control group.

[0078] 3.2.4 Effects of inoculation with *Chaetoceros aubergine* FF21 on SOD and PPO enzyme activities in blueberry plants

[0079] Blueberry potted seedlings after 90 days of cultivation management according to item "3.1" were used to determine the SOD and PPO contents of the aboveground and underground parts of the blueberry plants using the nitroblue tetrazol (NBT) photoreduction method and the catechol colorimetric method.

[0080] Table 2. Effects of *Chaetoceros aubergine* FF21 on SOD and PPO enzyme activities in blueberry seedlings.

[0081] 3.2.5 Effect of inoculation with Chaetomium 'Aureum' FF21 on total phosphorus in blueberry plants

[0082] Blueberry potted seedlings were taken 90 days after cultivation management according to item "3.1", and the total phosphorus content of the blueberry plants was determined by semi-micro Kjeldahl method.

[0083] Result: See Figure 10 After using *Trichoderma flavonoides* FF21, the total phosphorus content of blueberry plants reached 5.63 g / kg, which is 22.93% higher than the control group.

[0084] 3.3 Conclusion: Since blueberries are shallow-rooted plants with slow growth, this study primarily investigated the growth-promoting function of endophytic fungi in blueberries. The selected dominant strain FF21, known for its good growth-promoting effect, was inoculated onto blueberry tissue culture seedlings, and its inoculation effect was observed. Results showed that endophytic fungal hyphae structure could be observed in the roots of blueberries inoculated with FF21. Furthermore, the seedling height, diameter at root, above-ground fresh weight, below-ground fresh weight, above-ground dry weight, and below-ground dry weight of the inoculated blueberry seedlings were significantly higher than those of the control group. Root activity in the treatment group was also significantly higher than that in the uninoculated group, indicating that FF21 inoculation significantly promoted root growth in blueberry seedlings. Plant roots are the main organs for absorbing and transporting nutrients, and their growth status largely determines the plant's ability to acquire water and nutrients. Therefore, root activity is an important indicator for assessing the physiological condition of plant roots. Phosphorus is an essential nutrient element for plant growth and development, and the amount of phosphorus absorbed by plants is crucial for fruit formation. The phosphorus levels in blueberry seedlings in the treatment groups were significantly increased, indicating that inoculation with strain FF21 can improve blueberry yield. When plants are under stress, the content of osmotic regulators within them changes directly. Therefore, one of the important indicators for evaluating plant metabolism and physiological state is the content of soluble sugars in the plant. In this study, the soluble sugar content in the treatment groups was higher than that in the control group. Antioxidant enzymes in plants maintain a dynamic balance between the production and removal of reactive oxygen species within their cells. In this study, inoculation with FF21 significantly increased the content of SOD and PPO enzymes in blueberry seedlings. These results indicate that inoculation with FF21 can promote the growth of blueberry seedlings and increase the activity of antioxidant enzymes and the content of osmotic regulators in blueberry seedlings.

Claims

1. A golden chamomile fungus FF21 that promotes blueberry growth, characterized by: The taxonomic name of the golden chamomile FF21 is Arcopilus aureus It was deposited at the China General Microbiological Culture Collection Center on September 19, 2024, with accession number CGMCC No. 41521; The golden scab FF21 was obtained from blueberry roots by tissue isolation method.

2. The golden chamomile FF21 according to claim 1, characterized in that: The tissue separation method is performed according to the following steps: (1) Cleaning and disinfection: Select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to the ultra-clean workbench, immerse them in 75% ethanol solution for 2-4 seconds, rinse them with sterile water 4-6 times, disinfect them with 75% ethanol for 20-40 seconds, rinse them with sterile water 4-6 times and dry them to obtain product A; (2) Culture, isolation and purification: Place product A in PDA medium and incubate in a constant temperature incubator at 28℃ for 3-5 days. After dark septate hyphae grow in the culture dish, pick the edge hyphae to a new PDA culture dish and continue to culture. Repeat 3-5 times to obtain pure culture strain and obtain golden scab FF21.

3. The golden chamomile FF21 according to claim 2, characterized in that: In step (1), cleaning and disinfection: select the roots of blueberries with healthy surfaces and no disease spots, wash them with clean water, drain them with filter paper, transfer them to a clean bench, soak them in 75% ethanol solution for 3 seconds, rinse them 5 times with sterile water, disinfect them with 75% ethanol for 30 seconds, rinse them 5 times with sterile water and dry them to obtain product A.

4. The golden chamomile FF21 according to claim 2, characterized in that: In step (2), the PDA culture medium is prepared by dissolving 200g of potato, 20g of glucose and 20g of agar in 1000mL of distilled water, with a natural pH.

5. A blueberry growth promoter comprising the golden chrysogenum FF21 as described in claim 1.

6. The application of *Chaetoceros flavonoides* FF21 as described in claim 1, characterized in that: The application of the golden chamomile FF21 in the preparation of a blueberry growth-promoting agent, wherein the method of promoting blueberry growth is to increase the content of soluble sugars, SOD enzymes, PPO enzymes and total phosphorus in blueberries.

7. A blueberry growth-promoting bacteria product, characterized in that: The active ingredient of the product includes the *Chaetoceros aubergine* FF21 as described in claim 1.

8. A blueberry growth-promoting bacteria product, characterized in that: The active ingredient of the product is the *Chaetoceros aubergine* FF21 as described in claim 1.

9. A method for preparing a blueberry growth-promoting bacteria product, characterized in that: The *Chaetoceros flavonoids* FF21 described in claim 1 is used as an active ingredient or one of the active ingredients in the preparation of the product.

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