A fungicidal composition for preventing and treating orchid root rot

Abstract

The present application belongs to the technical field of orchid disease prevention and treatment, and particularly relates to a fungicidal composition for preventing and treating orchid root rot. The fungicidal composition for preventing and treating orchid root rot comprises active ingredients of nerol and compound a, wherein the compound a is at least one selected from prochloraz, difenoconazole and carbendazim. When nerol is compounded with prochloraz, difenoconazole and carbendazim, the synergistic effect is shown by the co-toxicity coefficient (CTC) value of the compound combination to the pathogenic fungus of Rhizoctonia solani being greater than 120, which indicates that the compound combination can improve the prevention and treatment effect on orchid root rot. In addition, the fungicidal composition contains two effective ingredients, which can delay the generation and development of pathogenic fungi resistance and overcome the problems existing in long-term use of single component fungicides. In summary, the fungicidal composition can be used for developing fungicides for preventing and treating orchid root rot.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of orchid disease prevention and treatment, and particularly relates to a fungicidal composition for preventing and treating orchid root rot. BACKGROUND

[0002] Orchid is one of the largest families in plant taxonomy, with 800 genera and more than 35000 species, and its numerous horticultural varieties are of great ornamental value. Orchid root rot is a soil-borne disease that occurs universally in the process of orchid planting, and its pathogenic fungus is Rizoctonia solani. When orchids are harmed by root rot, brown lesions and necrosis occur on the roots at the initial stage, multiple lesions present a ring around the stem base in severe cases, and finally the entire root rots, even leading to no flowering of the orchid plant and greatly reducing its ornamental and commercial values.

[0003] The prevention and treatment of orchid root rot usually adopts a comprehensive strategy and method, but chemical control is still one of the indispensable measures, such as prochloraz, chlorothalonil, carbendazim, azoxystrobin and difenoconazole. Although some effective fungicides are available on the market, the pathogenic bacteria have developed resistance to single-component fungicides due to long-term unscientific use, resulting in poor control effect. The reasonable compounding or mixing of fungicide compounds has the advantages of improving the control effect and delaying the development of pathogenic bacteria resistance, and is one of the most effective methods to solve the problem of pathogenic bacteria resistance. Therefore, it is of great significance to screen a compound fungicide that is environmentally friendly and has good control effect on orchid root rot.

[0004] The synthesis and antibacterial activity of natural citral derivatives were studied, and it was found that nerol had strong antibacterial effect on a variety of plant pathogenic bacteria, such as EC 50 The EC50 values of nerol against P. capsici, G. cingulate, R. solani, S. sclerotivorum and V. theicola were 7.3421 mg / L, 8.6636 mg / L, 13.6902 mg / L, 13.6165 mg / L and 12.1684 mg / L, respectively. It can be seen that nerol has the potential to be developed into a biological pesticide.

[0005] At present, there is no related report on the compounding use of nerol with prochloraz, difenoconazole or carbendazim for preventing and treating orchid root rot. SUMMARY

[0006] The present application aims to provide a fungicidal composition for preventing and treating orchid root rot.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0008] A fungicidal composition for preventing and treating orchid root rot, wherein the active ingredient is a mixture of nerol and compound a, and the compound a is at least one selected from prochloraz, difenoconazole and carbendazim.

[0009] Further, the compound a is prochloraz, and the mass ratio of nerol to compound a is 3-7:1.

[0010] Further, the compound a is difenoconazole, and the mass ratio of nerol to compound a is 1-10:25-1.

[0011] Further, the compound is carbendazim, and the mass ratio of nerol to compound a is 1-4:20-1.

[0012] Further, the pathogenic bacteria of orchid root rot is Rizoctonia solani.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] When nerol is mixed with prochloraz, difenoconazole and carbendazim, the CTC value of the mixed combination to the pathogenic bacteria Rizoctonia solani of orchid root rot is greater than 120, which shows a synergistic effect. It is shown that the mixed combination of the present application can improve the prevention and treatment effect on orchid root rot. In addition, the fungicidal composition of the present application contains two effective components, which can delay the development of pathogenic bacteria resistance and overcome the problems existing in long-term use of single component fungicides. In summary, the fungicidal composition of the present application can be used for developing fungicides for preventing and treating orchid root rot. DETAILED DESCRIPTION

[0015] The technical solutions of the present application will be further described below in combination with specific embodiments, but the scope of the present application cannot be limited, and general modifications made by those skilled in the art to the present application will be equivalent to fall within the scope defined in the claims of the present application.

[0016] MATERIALS AND METHODS

[0017] 1.1 MATERIALS

[0018] 1.1.1 Test strains

[0019] Rizoctonia solani was isolated from orchid root rot disease strains.

[0020] 1.1.2 Test agents

[0021] 98% nerol (CAS: 106-25-2), 97% prochloraz technical, 96.5% difenoconazole technical, 98% carbendazim technical,

[0022] 1.1.3 Culture medium

[0023] PDA medium: peeled potato 200 g, glucose 15, agar 15 g, distilled water to 1 L, natural pH.

[0024] 1.2 Method

[0025] 1.2.1 Activation of test strains

[0026] A small amount of mycelium of Rhizoctonia solani, the pathogen of orchid root rot, was picked up with an inoculation needle and inoculated into a Petri dish (9 cm in diameter) of PDA medium, which was then cultured in a constant-temperature incubator at 22°C for 3 days for standby use.

[0027] 1.2.2 Preparation of agents

[0028] After the test agent was completely dissolved, it was diluted with a 0.1% volume fraction of Tween-80 aqueous solution to prepare a single-agent stock solution with an effective ingredient of 5000 mg / L.

[0029] 1.2.3 Method for determining the antibacterial activity of agents on Rhizoctonia solani, the pathogen of orchid root rot

[0030] The mycelial growth rate method was adopted. 1 mL of the agent solution and 9 mL of pre-melted PDA medium were mixed uniformly and poured into a Petri dish with a diameter of 9 cm, which was then left to stand. After the medium cooled down, a 5-mm-diameter mycelial cake was cut from the edge of the colony of the activated test strain and inoculated into the center of the Petri dish, with the treatment of 0.1% Tween-80 aqueous solution as the control, and each treatment was repeated 3 times. After covering the Petri dish with a lid and placing it in a constant-temperature incubator at 25°C, the colony diameter was measured by the cross method when the control colony diameter reached about 6 cm, and the mycelial growth inhibition rate of different treatments was calculated.

[0031]

[0032] 1.2.4. Determination of the virulence of single agents on Rhizoctonia solani, the pathogen of orchid root rot

[0033] The single-agent stock solution prepared in 1.2.2 was diluted with a 0.1% volume fraction of Tween-80 aqueous solution into 5 mass concentration gradients, and the mycelial growth inhibition rate of each single-agent treatment was determined according to the method of 1.2.3. Linear regression analysis was performed with the logarithmic value of the agent concentration as x and the corresponding mycelial growth inhibition rate as y, and the virulence regression equation and the EC 50 value of the single agent were obtained.

[0034] 1.2.5 Determination of the virulence of mixed agents on Rhizoctonia solani, the pathogen of orchid root rot

[0035] On the basis of single agent virulence determination, set multiple groups of matching, each matching mixture was diluted with 0.1% Tween-80 aqueous solution to 5 mass concentration gradients, according to the method of 1.2.3 to determine the mycelial growth inhibition rate of each matching mixture, and the logarithm of the concentration of the agent was taken as x, and the corresponding mycelial growth inhibition rate was taken as y to perform linear regression analysis, and the virulence regression equation and the EC 50 value of the matching mixture were obtained.

[0036] 1.2.6 Virulence evaluation of combined agents

[0037] The synergistic effect of the agents was evaluated according to the calculated synergistic coefficient (CTC value) of the mixture: synergistic coefficient (CTC) ≥ 120 showed synergistic effect; synergistic coefficient (CTC) ≤ 80 showed antagonistic effect; 80 < synergistic coefficient (CTC) < 120 showed additive effect.

[0038] 2. Results and analysis

[0039] 2.1 Single agent virulence determination of Rhizoctonia solani, the pathogen of orchid root rot

[0040] The results are shown in Table 1.

[0041] Table 1 Virulence determination of single agent on Rhizoctonia solani, the pathogen of orchid root rot

[0042]

[0043] As shown in Table 1, by linear regression analysis between the logarithm of the concentration of each agent and the corresponding mycelial growth inhibition rate, the virulence regression equation of orange flower alcohol, prochloraz, benzoxazol and carbendazim on Rhizoctonia solani, the pathogen of orchid root rot, was obtained, and the corresponding EC50 values were 18.4623 mg / L, 9.2234 mg / L, 4.3133 mg / L and 13.5496 mg / L, respectively.

[0044] 2.2 Virulence determination of orange flower alcohol and prochloraz matching on Rhizoctonia solani, the pathogen of orchid root rot

[0045] The results are shown in Table 2.

[0046] Table 2 Virulence determination results of orange flower alcohol and prochloraz matching on Rhizoctonia solani, the pathogen of orchid root rot

[0047]

[0048] Table 2 shows that within a mass ratio of 3-7:1, the co-toxicity coefficient (CTC) of the combined nerol and prochloraz against *Rhizoctonia solani*, the pathogen causing root rot in orchids, ranged from 122.3208 to 171.0184, all greater than 120, indicating a synergistic effect. This suggests that the combination of nerol and prochloraz can improve the control effect against root rot in orchids.

[0049] 2.3 Virulence determination of nerol and difenoconazole combination against Rhizoctonia solani, the pathogen causing root rot in orchids.

[0050] The results are shown in Table 3.

[0051] Table 3. Virulence test results of nerol and difenoconazole combination against Rhizoctonia solani, the pathogen causing root rot in orchids.

[0052]

[0053] Table 3 shows that within a mass ratio of 1-10:25-1, the co-toxicity coefficient (CTC) of the combination of nerol and difenoconazole against *Rhizoctonia solani*, the pathogen causing root rot in orchids, ranged from 122.2103 to 264.2957, all greater than 120, indicating a synergistic effect. This suggests that the combination of nerol and difenoconazole can improve the control effect against root rot in orchids.

[0054] 2.4 Virulence determination of nerol and carbendazim combination against Rhizoctonia solani, the pathogen causing root rot in orchids.

[0055] The results are shown in Table 4.

[0056] Table 4. Virulence test results of nerol and carbendazim combination for Rhizoctonia solani, the pathogen causing root rot in orchids.

[0057]

[0058] Table 4 shows that within a mass ratio of 1-4:20-1, the co-toxicity coefficient (CTC) of the combination of nerol and carbendazim against *Rhizoctonia solani*, the pathogen causing root rot in orchids, ranged from 120.3678 to 171.3349, all greater than 120, indicating a synergistic effect. This suggests that the combination of nerol and carbendazim can improve the control effect against root rot in orchids.

Claims

1. A fungicide composition for preventing and controlling root rot in orchids, characterized in that, Its active ingredient is composed of nerol and compound a, wherein compound a is imazalil, and the mass ratio of nerol to compound a is 3-7:1.

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