Compound biocontrol agent for preventing and treating banana wilt and application thereof

Abstract

The present application relates to the technical field of biological control, in particular to a compound biocontrol agent for preventing and treating banana wilt and application thereof.The compound biocontrol agent contains bacillus velezensis BG2001 and trichoderma harzianum T1-6; the preservation number of the bacillus velezensis BG2001 is CGMCC NO.21737; the preservation number of the trichoderma harzianum T1-6 is CGMCC NO.40943.The two biocontrol agents in the compound biocontrol agent provided by the present application have different biocontrol mechanisms and good compatibility, can play a synergistic effect in disease control, and can promote the growth of banana plants, and combined use can play a multi-functional advantage to inhibit the occurrence of banana wilt.The compound biocontrol agent has good preventive effect, improves the disease resistance of plants, simultaneously improves the micro-ecological environment in soil, and promotes the reproduction of the population number of beneficial microorganisms in soil, and the effect is better than that of a single strain, and the safety is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biological control, in particular to a compound biocontrol agent for preventing and treating banana wilt and application thereof. BACKGROUND

[0002] Banana is a perennial herb and an important economic crop in subtropical regions of southern China. In production, banana industry is threatened by various diseases and pests. Among them, banana wilt is a devastating vascular soil-borne disease in banana production, and its pathogen is Fusarium oxysporum.f.sp.cubense. Once the soil is infected by the pathogen, it is difficult to completely eliminate. The yield loss of severely diseased fields can be as high as more than 50%, and even the plantation is destroyed and the yield is lost. In recent years, in the banana planting areas in the southern part of Fujian Province, the occurrence, spread and damage of wilt have led to a decrease in planting area year by year, and the healthy and sustainable development of banana industry has been seriously threatened and challenged.

[0003] At present, there is no specific drug for the prevention and treatment of banana wilt, and biological control is more and more valued because of its advantages of no pollution, low cost, high efficiency and the like. Huang Jianfeng et al. obtained two strains of Bacillus subtilis H-2 and Bacillus amyloliquefaciens H-7 with good antagonistic effect on banana wilt pathogen from the rhizosphere soil of healthy banana plants in diseased banana plantations, which showed good control effect in the field.

[0004] However, biocontrol agents (fertilizers) often have unstable control effect and biocontrol bacteria are not easy to colonize in soil or host body during field application. In field investigation, the laboratory found that some wild bananas scattered in the corners and along the roads in the village in the main banana production areas grew well and no wilt occurred, which may be related to the long-term existence of some beneficial antagonistic indigenous microorganisms in the rhizosphere soil. It is reported that indigenous microorganisms have the ability to colonize efficiently in local habitat systems. At present, the production of biocontrol bacteria for banana wilt is mostly obtained from the body or rhizosphere soil of healthy plants in diseased and healthy banana plantations, and the exploitation and utilization of local indigenous antagonistic microbial resources in the rhizosphere soil of wild banana have not been reported. At present, the development of microbial agents in production is mostly towards the development trend of compound use of biocontrol bacteria, and the combination of different functional biocontrol strains can achieve functional complementation. Compared with single biocontrol agent (fertilizer), compound biocontrol agent can better adapt to complex environmental conditions to overcome the problems of large demand for viable bacteria and unstable control effect. In summary, the use of local indigenous biocontrol strains, the combination of different functional strains to prepare compound biocontrol agents with high antagonistic activity and good environmental adaptability, and the further development and popularization of new biocontrol agents (fertilizers) are of great significance for effectively controlling the occurrence of banana wilt. SUMMARY

[0005] In order to solve the above problems, the application provides a compound biocontrol agent for preventing and treating banana fusarium wilt and application thereof, the application combines two biocontrol strains with different sources and biological characteristics, the compound biocontrol agent can effectively prevent and treat banana fusarium wilt and has a growth promoting effect on plants.

[0006] In order to achieve the above purpose, the application provides the following technical scheme.

[0007] The application provides a compound biocontrol agent for preventing and treating banana fusarium wilt, wherein the compound biocontrol agent contains bacillus velezensis BG2001 and trichoderma harzianum T1-6.

[0008] The preservation number of the bacillus velezensis BG2001 is CGMCC NO.21737.

[0009] The preservation number of the trichoderma harzianum T1-6 is CGMCC NO.40943.

[0010] Preferably, the content of the bacillus velezensis BG2001 in the compound biocontrol agent is 0.5-5*10 7 cfu / mL.

[0011] The content of the trichoderma harzianum T1-6 is 0.5-5*10 6 cfu / mL.

[0012] Preferably, the content of the bacillus velezensis BG2001 in the compound biocontrol agent is 3.00*10 7 cfu / mL.

[0013] The content of the trichoderma harzianum T1-6 is 1.75*10 6 cfu / mL.

[0014] The application also provides application of the compound biocontrol agent in the above technical scheme in preventing and treating banana fusarium wilt.

[0015] Preferably, the application comprises: irrigating the banana plants with the compound biocontrol agent.

[0016] Preferably, the irrigation amount of each banana plant is 100 mL.

[0017] The application also provides application of the compound biocontrol agent in the above technical scheme in promoting the growth of banana plants.

[0018] Preferably, the application promotes the number of leaves, the plant height and the length of the main root of the banana plants.

[0019] Preferably, the application comprises: irrigating the banana plants with the compound biocontrol agent.

[0020] Preferably, the amount of root irrigation per banana plant is 100 mL.

[0021] Beneficial effects:

[0022] 1) The complex biocontrol agent provided by the present application is isolated from the rhizosphere soil of wild banana plants in the local banana production area, has strong adaptability to the local soil microenvironment, is more likely to colonize the roots of banana plants to prevent the invasion of pathogenic bacteria, and has a good growth promoting effect on the plants. The Trichoderma harzianum T1-6 is also isolated from the rhizosphere soil of healthy banana plants in the local diseased banana garden, and can inhibit and avoid pathogenic bacteria by occupying the pathogenic bacteria infection site and producing metabolites.

[0023] 2) The two biocontrol agents in the complex biocontrol agent provided by the present application have different biocontrol mechanisms and good compatibility, can play a synergistic effect in disease control, and can promote the growth of banana plants. The combined use can play the advantages of multiple functions to inhibit the occurrence of banana wilt. It has good preventive effect, improves the disease resistance of plants, and at the same time improves the microecological environment in the soil and promotes the reproduction of the population number of beneficial microorganisms in the soil. Its effect is better than that of a single strain, and it is safe.

[0024] 3) The complex biocontrol agent provided by the present application is harmless to humans and animals, can reduce the use of chemical pesticides, delay the risk of pathogenic bacteria resistance, solve a series of environmental problems caused by it, and the growth promoting function of the plant can be mixed with organic fertilizer for application to save cost. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below.

[0026] Figure 1 The colony morphology of strains BG2001 and T1-6;

[0027] Figure 2 The plate antagonistic effect of strains BG2001 and T1-6 on banana wilt fungus;

[0028] Figure 3 The inhibitory effect of the fermentation liquor of strain BG2001 on banana wilt fungus;

[0029] Figure 4 The compatibility of strains BG2001 and T1-6 in the complex biocontrol agent;

[0030] Figure 5 The control effect of the complex biocontrol agent on banana wilt (corm part);

[0031] Figure 6It is the growth-promoting effect of composite biocontrol agents on banana.

[0032] Biological Deposit Description

[0033] Bacillus velezensis BG2001, Latin name Bacillus velezensis, was deposited on January 26, 2021 at the General Microbiology Center of China Culture Collection Administration, No. 3, Beichen No. 1, Chaoyang West Road, Beijing, with the deposit number CGMCC NO.21737.

[0034] Trichoderma harzianum T1-6, Latin name Trichoderma harzianum, was deposited on December 15, 2023 at the General Microbiology Center of the China Culture Collection Administration, located at No. 3, Beichen No. 1, Chaoyang West Road, Beijing, with the deposit number CGMCC NO.40943. DETAILED DESCRIPTION

[0035] The present invention provides a composite biocontrol agent for preventing and controlling banana wilt disease, comprising Bacillus velezensis BG2001 and Trichoderma harzianum T1-6; the Bacillus velezensis BG2001 has a deposit number of CGMCC NO. 21737; and the Trichoderma harzianum T1-6 has a deposit number of CGMCC NO. 40943. In the present invention, the bacterial content of Bacillus velezensis BG2001 in the composite biocontrol agent is preferably 0.5 to 5×10 7 cfu / mL; the bacterial content of Trichoderma harzianum T1-6 is preferably 0.5 to 5×10 6 In the present invention, the bacterial content of Bacillus velezensis BG2001 in the composite biocontrol agent is more preferably 3.00×10 7 cfu / mL; the bacterial content of Trichoderma harzianum T1-6 is more preferably 1.75×10 6 pieces / mL.

[0036] Among the composite biocontrol agents, the colonies of biocontrol bacterium BG2001 on LB medium plates are small, nearly round, and milky white with regular edges. The colonies are slightly convex and wrinkled around the edges, and the surface is moist and smooth. Microscopic observation reveals that the bacteria are rod-shaped and can produce spores. The mycelium of biocontrol fungus Trichoderma sp. T1-6 on PDA medium plates is initially dense and white, but later turns green or dark green, bearing numerous small, spherical conidia with tiny tubercles on the spore wall.

[0037] The physiological and biochemical test results show that the biocontrol bacteria BG2001 is a gram-positive bacteria, can secrete contactase, grows in pH 5.0 and 1% NaCl, and can utilize trehalose, sucrose, fructose, glucose and mannitol, and the D-malic acid, acetic acid, mucic acid and alpha-ketobutyric acid reactions are all negative. Through the molecular identification of 16S rRNA and gyrB gene sequences and the physiological and biochemical determination, the biocontrol bacteria BG2001 is identified as Bacillus velezensis.

[0038] The preparation method of the composite biocontrol agent is not particularly limited in the present application, and can be prepared by a conventional preparation method, for example, the conventional preparation of Bacillus velezensis BG2001 fermentation broth and Trichoderma harzianum T1-6 fermentation broth, and then mixed at a volume ratio of 1:1 to obtain the composite biocontrol agent. The bacterial content of the Bacillus velezensis BG2001 fermentation broth is 1-10 x 10 7 cfu / mL, and the bacterial content of the Trichoderma harzianum T1-6 fermentation broth is 1-10 x 10 6 In the present application, the formula of the liquid culture medium used in the culture process of the Bacillus velezensis BG2001 fermentation broth is: 10 g of tryptone, 5 g of yeast extract, 10 g of sodium chloride, and 1000 mL of water, and the pH is 7.0; the formula of the fermentation medium is: 20 g of corn flour, 40 g of soybean meal, 5 g of sodium chloride, 3 g of peptone, 5 g of yeast powder, 2 g of lactose, 2 g of calcium carbonate, 0.5 g of potassium dihydrogen phosphate, 0.3 g of magnesium sulfate, and 1000 mL of water, and the pH is 6.5-7.0. Further, the Bacillus velezensis BG2001 is activated on a plate, inoculated into the liquid culture medium, and cultured at 28°C and 180 rpm / min constant temperature oscillation for 24 h, and then inoculated into the fermentation medium at an inoculation amount of 1%, and cultured at 28°C and 180 rpm / min constant temperature oscillation for 24 h to obtain the Bacillus velezensis BG2001 fermentation broth. In the present application, the formula of the liquid culture medium used in the culture process of the Trichoderma harzianum T1-6 fermentation broth is: 200 g of potato, 15 g of glucose, and 1000 mL of water, and the pH is natural; further, the Trichoderma harzianum T1-6 is activated on a plate, inoculated into the liquid culture medium by punching the bacterial cake, and cultured at 28°C and 160 rpm / min constant temperature oscillation for 3 d to obtain the Trichoderma harzianum T1-6 fermentation broth.

[0039] The present application also provides the application of the composite biocontrol agent in the prevention and treatment of banana fusarium wilt. In the present application, the application preferably includes: irrigating the banana plant with the composite biocontrol agent. In the present application, the irrigation amount of each banana is preferably 100 mL.

[0040] The present invention also provides the use of the composite biocontrol agent described in the above technical solution for promoting the growth of banana plants. In the present invention, the use preferably promotes the number of leaves, plant height, and taproot length of banana plants. In the present invention, the use preferably includes: irrigating the banana plants with the composite biocontrol agent. In the present invention, the root irrigation volume per banana plant is preferably 100 mL.

[0041] In order to further illustrate the present invention, the present invention is described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] Screening and identification of strain BG2001

[0044] 1. Isolation of strains

[0045] Rhizosphere soil samples of healthy wild bananas were collected from banana producing areas in Fujian Province, dried naturally, crushed, and sieved. 10 g of soil sample was weighed and poured into a triangular flask containing 90 mL of sterile water. After shaking, it was allowed to stand for 5 minutes to prepare a soil suspension. After gradual dilution with a 10-fold gradient, 10 -3 , 10 -4 100 μL of the soil suspension was spread on an LB medium plate and cultured at 28°C for 48 h. Single colonies of different bacteria were picked and purified based on the color, morphology, and size of the colonies on the plate.

[0046] 2. Screening of strains

[0047] The banana wilt pathogen was used as the target. A punch was used to obtain hyphae from the edge of the activated pathogen colony and transferred to the center of a blank PDA culture medium plate. An inoculation loop was used to inoculate the isolated bacterial strain 20 mm away from the center. The pathogen without the test strain was used as a control. After constant temperature cultivation at 28°C for 7 days, the confrontation effect between the test strain and the pathogen was observed. A strain with good antagonism to banana wilt pathogen was screened out and named BG2001.

[0048] 3. Identification of strains

[0049] The strain BG2001 was streaked onto LB medium and cultured for 48 h. Figure 1 As shown, the colonies of strain BG2001 on LB plates are small, nearly round, and milky white with regular edges. The colonies are slightly convex and wrinkled around the edges, and the surface is moist and smooth. Physiological and biochemical tests revealed that it is Gram-positive, secretes catalase, and grows in a pH 5.0 environment with 1% NaCl. It can utilize trehalose, sucrose, fructose, glucose, and mannitol, but is negative for D-malic acid, acetic acid, mucic acid, and α-ketobutyric acid.

[0050] Molecular identification: The bacterial DNA was amplified by PCR using 16S rRNA gene and gyrB gene primers by PCR instrument, and sequencing was performed. The sequencing results were subjected to BLAST comparison on the NCBI website to determine the taxonomic status of the strain. The results showed that the 16S rRNA (SEQ ID NO. 1) and gyrB sequence (SEQ ID NO. 2) of the strain BG2001 had high similarity with Bacillus velezensis by BLAST comparison. Combined with morphological, physiological and biochemical characteristics and 16S rRNA and gyrB genes, the strain BG2001 was identified as Bacillus velezensis. Bacillus velezensis BG2001 was preserved in China General Microbiological Culture Collection Center on March 1, 2021, with a preservation number of CGMCC NO. 21737 and a preservation address of No. 1, Xibahe West Road, Beijing Chaoyang District, China.

[0051] SEQ ID NO. 1 16S rRNA sequence:

[0052]

[0053] SEQ ID NO. 2 gyrB sequence:

[0054]

[0055] Example 2

[0056] Inhibition of F. oxysporum by biocontrol bacteria BG2001 and Trichoderma T1-6

[0057] The activated F. oxysporum was inoculated in the center of PDA medium plate, and the biocontrol bacteria BG2001 and Trichoderma T1-6 were inoculated at 20 mm from the center, respectively. The pathogenic bacteria without inoculation of the tested strains were used as control. After incubation at 28°C for 7 days, the confrontation effect of the biocontrol bacteria and the pathogenic bacteria was observed. The results showed that the biocontrol bacteria BG2001 exhibited good antagonism to F. oxysporum, and the inhibition zone width was 16.67 mm. The growth speed of Trichoderma T1-6 on the plate was obviously faster than that of F. oxysporum, and the colony of Trichoderma T1-6 surrounded the whole pathogenic bacteria colony after 7 days. Figure 2

[0058] In addition, after activation of the biocontrol bacteria BG2001, single colony was picked and inoculated in liquid medium, and incubated at 28°C with 180 r / min shaking overnight. The culture of the biocontrol bacteria was centrifuged at 8000 rpm for 10 min, and the supernatant was vacuum filtered through a bacterial filter with 0.22 μm membrane. Then, the PDA medium cooled to 45°C was mixed with the filtered supernatant at a ratio of 1:3 to prepare a plate. The F. oxysporum cake was inoculated in the center of the plate, and incubated at 28°C. After 7 days, the colony diameter was measured by cross method, and the inhibition rate was calculated. The sterile water treatment was used as control, and each treatment was repeated for 3 times. The inhibition rate (%) = [(control colony radius - treated colony radius) / control colony radius] x 100. The inhibition test showed that the metabolic product of the biocontrol bacteria BG2001 had good inhibition effect on the mycelial growth of F. oxysporum, and the inhibition rate was up to 37.73%.

[0059] Example 3

[0060] Detection of affinity between biocontrol bacteria

[0061] The mycelial block was punched from the edge of the colony of Trichoderma T1-6 cultured for 2 days by a 5 mm diameter puncher, and inoculated in the center of PDA medium plate. The activated biocontrol bacteria BG2001 was inoculated at 20 mm from the center, and the Trichoderma T1-6 without inoculation of the tested bacteria was used as control. After incubation at 28°C for 5 days, whether the biocontrol bacteria BG2001 and Trichoderma T1-6 produced inhibition zone was observed. The results showed that the biocontrol bacteria BG2001 and Trichoderma T1-6 did not produce inhibition zone when they were co-cultured on PDA medium. Figure 4

[0062] Example 4

[0063] ​​Prevention and treatment effect of complex biocontrol agent on banana fusarium wilt

[0064] Preparation of fermentation broth of biocontrol bacteria BG2001: after activation, the biocontrol bacteria BG2001 was inoculated into LB liquid medium, and cultured at 28℃ with 180r / min shaking overnight. Then, 1mL of the culture was inoculated into fermentation medium, and cultured at 28℃ with 180r / min shaking for 24h to obtain the fermentation broth of the strain. The fermentation broth was diluted with sterile water to obtain a concentration of 6.0×10 7 cfu / mL.

[0065] Preparation of fermentation broth of Trichoderma harzianum T1-6: after activation, the Trichoderma harzianum T1-6 was inoculated into PB medium, and cultured at 28℃ with 160r / min shaking for 3d to obtain the fermentation broth. The fermentation broth was diluted with sterile water to obtain a concentration of 3.5×10 6 cfu / mL.

[0066] The fermentation broth of Bacillus velezensis BG2001 and the fermentation broth of Trichoderma harzianum T1-6 were mixed in a volume ratio of 1:1 to prepare the complex biocontrol agent.

[0067] Preparation of banana fusarium wilt spore suspension: banana fusarium wilt pathogen No. 4 physiological race was inoculated into PDA medium plate, and cultured at 28℃ for 7d. The spore suspension was washed with sterile water, filtered with double sterile gauze, and obtained. The pathogenic fungus spore suspension was diluted with sterile water to obtain a concentration of 1.00×10 5 cfu / mL.

[0068] Under the condition of a greenhouse, banana bagged seedlings were transplanted into nutrient pots filled with healthy vegetable garden soil, and one banana seedling was planted in each pot. After the banana seedlings grew to 6-7 leaves, the root irrigation method was used to inoculate the complex biocontrol agent, and 100mL was irrigated in each pot. On the second day, the banana fusarium wilt spore suspension was inoculated, and 100mL was irrigated in each pot. At the same time, single biocontrol agent and water were set as controls, and each treatment was repeated three times. After inoculation, the environmental temperature in the greenhouse was maintained at 28-32℃, and routine fertilization and irrigation management was carried out. After 30d of inoculation, the whole banana seedling was dug out, washed clean with water, cut open the corm tissue, and graded according to the browning area ratio of the longitudinal section of the corm tissue. The disease index and disease prevention effect of each treatment were calculated.

[0069] Grading standard: 0 grade for no browning of corm; 1 grade for corm browning area≤25%; 3 grade for 25%<corm browning area≤50%; 5 grade for 50%<corm browning area≤75%; and 7 grade for corm browning area>75%.

[0070] Disease index =∑(number of strains of each grade × representative value of this grade) / (total number of strains × representative value of the highest grade) × 100;

[0071] Control effect (%) = (disease index of control - disease index of treatment) / disease index of control x 100.

[0072] The results of the control test showed that 30 days after inoculation with the pathogen, the leaves of the control plants inoculated with the pathogen only turned yellow, some wilted, and the corms were brown to varying degrees when the corms were cut open, with a disease index of 78.91. However, the disease index of the plants treated with the complex biocontrol agent, biocontrol bacteria BG2001 and Trichoderma harzianum T1-6 was only 14.97, 25.40 and 36.39, respectively. Most of the leaves of the banana seedlings remained green, and the corms were rarely brown. The control effect of the complex biocontrol agent on banana fusarium wilt was 81.03%, 67.81% and 53.88%, respectively. Compared with single biocontrol bacteria, the control effect of the complex biocontrol agent was significantly improved (Table 1, Figure 5 ).

[0073] Table 1 Control effect of different treatment groups on banana fusarium wilt

[0074] Treatment Disease index Control effect (%) Compound biocontrol agent 14.97±1.18Cd 81.03±1.49Aa Biocontrol bacteria BG2001 25.40±3.64BCc 67.81±4.61Bb Trichoderma harzianum T1-6 36.39±4.13Bb 53.88±5.23Cc Control 78.91±7.16Aa -

[0075] Note: Different letters in the same column represent extremely significant difference (P < 0.01) and significant difference (P < 0.05), respectively. The same below.

[0076] Example 5

[0077] Promoting effect of the complex biocontrol agent on banana

[0078] The complex biocontrol agent, the fermentation broth of biocontrol bacteria BG2001 and the fermentation broth of Trichoderma harzianum T1-6 were prepared according to Example 4. The complex biocontrol agent, the fermentation broth of biocontrol bacteria BG2001 and the fermentation broth of Trichoderma harzianum T1-6 were irrigated respectively, and water was set as the control. Each pot was irrigated with 100 mL, and each treatment was repeated 3 times. After inoculation, the temperature in the greenhouse was maintained at 28-32℃, and the plants were managed regularly. 30 days after inoculation, the whole banana seedlings were dug up and rinsed with clean water, and the number of leaves, plant height and main root length were counted.

[0079] The results of the test showed that compared with the control, the number of leaves and the length of the main root of the banana seedlings treated with the complex biocontrol agent, biocontrol bacteria BG2001 and Trichoderma harzianum T1-6 were significantly increased, and the plants were healthy. The length of the main root of the banana seedlings treated with the three biocontrol agents was 44.68 mm, 38.31 mm and 34.87 mm, respectively, and the plant height was 61.87 mm, 54.63 mm and 52.86 mm, respectively. The length of the main root and the plant height of the banana seedlings treated with the complex biocontrol agent were significantly better than those treated with biocontrol bacteria BG2001 and Trichoderma harzianum T1-6.

[0080] Table 2 Promoting effect of different treatment groups on banana

[0081] Treatment Leaf number (piece) Main root length (mm) Plant height (mm) Compound biocontrol agent 7.61±0.17Aa 44.68±1.66Aa 61.87±0.76Aa Biocontrol bacteria BG2001 7.50±0.49Aab 38.31±1.88Bb 54.63±1.62Bb Trichoderma harzianum T1-6 6.97±0.21ABb 34.87±1.11Bc 52.86±0.77Bb Control 6.39±0.26Bc 29.74±1.92Cd 48.76±1.33Cc

[0082] Although the above embodiments have been described in detail, they are only some embodiments of the present application, not all embodiments. Other embodiments can be obtained on the basis of the above embodiments without creativity, and these embodiments also belong to the protection scope of the present application.

Claims

1. Application of composite biocontrol agents in promoting the growth of banana plants; The composite biocontrol agent contains Bacillus Velezii BG2001 and Trichoderma harzianum T1-6; The deposit number of the Bacillus velezinis BG2001 is CGMCC NO.21737; The deposit number of the Trichoderma harzianum T1-6 is CGMCC NO.40943.

2. The use according to claim 1, characterized in that The bacterial content of Bacillus Velezii BG2001 in the composite biocontrol agent is 0.5-5×10 7 cfu / mL; The bacterial content of the Trichoderma harzianum T1-6 is 0.5 to 5×10 6 pieces / mL.

3. The use according to claim 1, characterized in that The bacterial content of Bacillus Velezii BG2001 in the composite biocontrol agent is 3.00×10 7 cfu / mL; The bacterial content of Trichoderma harzianum T1-6 was 1.75×10 6 pieces / mL.

4. The use according to claim 1, characterized in that Promote the number of leaves, plant height and taproot length of banana plants.

5. The use according to claim 1, characterized in that The application comprises: irrigating the roots of banana plants with the composite biocontrol agent.

6. The use according to claim 5, characterized in that The root irrigation volume for each banana plant is 100 mL.

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