A method for improving the pathogenicity of metarhizium anisopliae cqm a421 to nilaparvata lugens by using the body surface hydrocarbons of the nilaparvata lugens

Abstract

The present application relates to the technical field of biological control of agricultural pests, and particularly relates to a method for improving pathogenicity of Metarhizium rileyi CQMa421 to Nilaparvata lugens by using carbon-hydrogen compounds on the body surface of the brown planthopper. The method for improving pathogenicity of Metarhizium rileyi to Nilaparvata lugens comprises mixing an effective dose of n-undecane liquid agent with the Metarhizium rileyi. The present application adopts the mixed use of n-undecane and Metarhizium rileyi, shortens the median germination time of Metarhizium rileyi, accelerates the initial process of infection, improves the pathogenicity to Nilaparvata lugens, and is conducive to rapid pest control. The n-undecane is a natural compound carried by insects, and the compound is safe to the environment and non-target organisms, and meets the development needs of green agriculture. The method only needs to simply mix the existing Metarhizium preparation with n-undecane before application, without the need to change the existing application equipment and process, and is easy to popularize and apply.

Description

Technical Field

[0001] This invention relates to the field of biological control technology for agricultural pests, specifically to a method for enhancing the pathogenicity of Metarhizium anisopliae CQMa421 against brown planthoppers using hydrocarbons on the surface of the brown planthopper. Background Technology

[0002] Brown planthopper ( Nilaparvata lugens Brown planthoppers (Brown planthoppers) are animals belonging to the family Planthopperidae in the order Hemiptera. They are one of the major destructive pests in rice-producing areas of my country and other parts of Asia, often leading to severe yield reductions or even crop failure. For a long time, the control of brown planthoppers has relied mainly on chemical pesticides, but this has resulted in increasingly prominent problems such as pesticide residues, environmental pollution, pest resistance, and resurgence. Therefore, the development of environmentally friendly and sustainable green control technologies is urgently needed.

[0003] Insect pathogenic fungi, such as Metarhizium anisopliae (… Metarhizium anisopliae Insecticidal fungi (ICFs) are an important class of biological insecticides that infect pests through contact with their body walls, without harming natural enemies and are environmentally safe, making them a strong candidate for the biological control of brown planthoppers. However, compared to chemical pesticides, they have drawbacks such as relatively slow insecticidal speed and efficacy greatly affected by environmental conditions, which to some extent limits their large-scale application. Improving the infection efficiency and insecticidal speed of entomopathogenic fungi is a research hotspot in the field of biological control.

[0004] In the paper "Insecticidal Activity and Toxin Production Condition Optimization of Secondary Metabolites of Metarhizium anisopliae," Yang Laying et al. conducted experiments and analyses on the effects of different culture medium components, temperature, and humidity on toxin production. In the paper "Factors Affecting Sporulation of Metarhizium anisopliae on Three Different Culture Media," experiments and studies were conducted on the conditions for culturing Metarhizium anisopliae on different culture media. These articles primarily study the physical conditions for the survival and reproduction of Metarhizium anisopliae; research on substances that can interact with Metarhizium anisopliae to further enhance its pathogenicity against pests remains insufficient.

[0005] Insect surface hydrocarbons ( Cuticular Hydrocarbons Hydrocarbons (CHCs) are an important component of the body wall barrier. Previous research by the inventors found that n-undecane is a key marker component of CHCs on the surface of the brown planthopper, with a relatively stable content of approximately 1%. However, research on the interaction between the hydrocarbons on the surface of the brown planthopper and its pathogenic fungus, *Metarhizium anisopliae*, is still limited, particularly regarding its development as a synergist for biocontrol practices, which has not yet been reported. Summary of the Invention

[0006] To overcome the shortcomings of the slow insecticidal speed of Metarhizium anisopliae in the existing technology, this invention adopts a method to significantly improve the pathogenicity and lethality of Metarhizium anisopliae against brown planthoppers using the hydrocarbon compound on the insect body surface, n-undecane. A technical solution is proposed to improve the pathogenicity of Metarhizium anisopliae CQMa421 against brown planthoppers by utilizing hydrocarbon compounds on the body surface of brown planthoppers.

[0007] The present invention is specifically implemented using the following technical solutions:

[0008] In a first aspect, the present invention proposes a method for improving the pathogenicity of Metarhizium anisopliae against brown planthoppers, wherein an effective dose of n-undecane liquid is added to Metarhizium anisopliae and mixed before or during application to brown planthoppers.

[0009] Furthermore, the n-undecane liquid is n-undecane liquid with a purity of 98% or higher.

[0010] Furthermore, the final volume concentration of the n-undecane liquid is 1 μL / mL - 50 μL / mL.

[0011] Secondly, the present invention provides a biological pesticide synergist for controlling brown planthoppers, wherein the synergist is an effective dose of n-undecane liquid, and the n-undecane liquid is n-undecane liquid with a purity of 98% or higher.

[0012] Thirdly, the present invention provides a biological pesticide composition for controlling brown planthoppers, comprising an effective dose of Metarhizium anisopliae spores and an effective dose of n-undecane liquid, wherein the n-undecane liquid is n-undecane liquid with a purity of 98% or higher.

[0013] Furthermore, the final volume concentration of the n-undecane is 1 μL / mL - 50 μL / mL.

[0014] Furthermore, the spore content of the *Metarhizium anisopliae* species is 4 × 10⁻⁶. 7 spores / mL.

[0015] Fourthly, the present invention provides the use of n-undecane in the preparation of an synergist for enhancing the pathogenicity of Metarhizium anisopliae against brown planthopper.

[0016] Fifthly, the present invention provides the application of a biological pesticide composition for controlling brown planthoppers in the control of brown planthoppers.

[0017] The present invention has the following beneficial effects:

[0018] (1) This invention uses a mixture of n-undecane and Metarhizium anisopliae to shorten the half-maximum germination time (GT) of Metarhizium anisopliae. 50This accelerates the initial infection process, increases pathogenicity to brown planthoppers, and facilitates rapid pest control.

[0019] (2) The n-undecane described in this invention is a natural compound carried by insects. This compound is safe for the environment and non-target organisms, which meets the development needs of green agriculture.

[0020] (3) The method described in this invention only requires simple mixing of the existing Metarhizium anisopliae preparation with n-undecane before application, without changing the existing application equipment and process, and is easy to promote and apply.

[0021] (4) The method described in this invention is simple, easy to operate, and low in cost, making it suitable for application in daily life and production. Attached Figure Description

[0022] Figure 1 A graph showing the comparison of spore germination rates of Metarhizium anisopliae with the addition of n-undecane (10 μL / mL) and the control group (CK).

[0023] Figure 2 Comparison curves of cumulative corrected mortality rates of brown planthoppers in different treatment groups (n-undecane + Metarhizium anisopliae, Metarhizium anisopliae treatment alone, and blank control). Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. Unless otherwise specified, the methods used in the embodiments of the present invention are conventional methods, and the reagents used are commercially available.

[0025] Example 1: The promoting effect of n-undecane on the in vitro germination of Metarhizium anisopliae spores

[0026] I. Experimental Methods

[0027] 1. Culture medium preparation: Prepare Potato Dextrose Broth (PDB) medium.

[0028] 2. Experimental Groups:

[0029] a. Treatment group: Add n-undecane solution to sterilized PDB medium to achieve a final concentration of 10 μL / mL.

[0030] b. Control group (CK): Sterilized PDB culture medium was not treated in any other way.

[0031] 3. Spore inoculation: Add 100 μL of Metarhizium anisopliae spore suspension (4 × 10⁻⁶) to each culture medium. 7 spores / mL).

[0032] 4. Cultivation and Observation: Incubate the culture medium at 26°C in a shaker at 160-180 rpm. Observe at least 200 spores randomly under a microscope every hour. The germination rate is calculated based on the germ tube length exceeding the short radius of the spore.

[0033] II. Experimental Results

[0034] As shown in Table 1, the GT50 (half-maximum germination time) of the treatment group was 10 hours, while that of the control group was 11 hours. The addition of n-undecane significantly accelerated the germination rate of *Metarhizium anisopliae*.

[0035] Table 1. Effects of n-Undecane on Metarhizium anisopliae spore germination

[0036]

[0037] Example 2: Synergistic effect of n-undecane on Metarhizium anisopliae infection of brown planthopper

[0038] I. Experimental Methods

[0039] 1. Test insects: Adult brown planthoppers with consistent physiological states were obtained by raising them in a greenhouse with rice seedlings.

[0040] 2. Preparation of microbial agents:

[0041] a. Treatment group: *Metarhizium anisopliae* spore suspension (4 × 10⁻⁶) 7 spores / mL, containing 0.05% Tween-80) + n-undecane (10 μL / mL).

[0042] b. Fungal control group: *Metarhizium anisopliae* spore suspension (4 × 10⁻⁶) 7 spores / mL, containing 0.05% Tween-80.

[0043] c. Blank control group: 0.05% Tween-80.

[0044] 3. Inoculation treatment: Quantitative spray inoculation was performed to ensure that each brown planthopper was evenly covered with a layer of droplets. Each treatment group was repeated at least 3 times, with 50 test insects per replicate.

[0045] 4. Feeding and observation: After inoculation, brown planthoppers were transferred to clean rearing boxes and fed with fresh rice seedlings. The conditions were 26°C, photoperiod L:D=16:8, and relative humidity 85%. The number of dead planthoppers was observed and recorded daily, and dead planthoppers were removed. This process was continued for 10 days.

[0046] II. Experimental Results

[0047] like Figure 2 As shown in Table 2, the mortality rate of brown planthoppers in the treatment group (n-undecane + Metarhizium anisopliae) increased the fastest, with a cumulative corrected mortality rate reaching 95% on day 6 and a LT50 (median lethal time) of 3.3 days. In contrast, the cumulative corrected mortality rate in the Metarhizium anisopliae-only treatment group was 60% on day 6, with an LT50 of 5.3 days. The mortality rate in the blank control group was less than 5%. These results indicate that n-undecane can significantly increase the pathogenicity rate of Metarhizium anisopliae.

[0048] Table 2. Pathogenicity of different treatments to brown planthoppers

[0049]

Claims

1. A method for improving the pathogenicity of Metarhizium anisopliae on brown planthoppers, characterized in that, When or before applying Metarhizium anisopliae to brown planthoppers, an effective dose of n-undecane liquid is added to the Metarhizium anisopliae and mixed.

2. The method for improving the pathogenicity of Metarhizium anisopliae against brown planthopper as described in claim 1, characterized in that, The n-undecane liquid is n-undecane liquid with a purity of 98% or higher.

3. A method for improving the pathogenicity of *Metarhizium anisopliae* to brown planthoppers as described in any one of claims 1 and 2, characterized in that, The final volume concentration of the n-undecane liquid is 1 μL / mL - 50 μL / mL.

4. A biological pesticide composition for controlling brown planthoppers, characterized in that, It contains an effective dose of Metarhizium anisopliae spores and an effective dose of n-undecane liquid, wherein the n-undecane liquid is n-undecane liquid with a purity of 98% or higher.

5. The biological pesticide composition for controlling brown planthoppers as described in claim 4, characterized in that, The final volume concentration of n-undecane is 1 μL / mL - 50 μL / mL.

6. A biological pesticide composition for controlling brown planthoppers as described in claim 4 or 5, characterized in that, The content of Metarhizium anisopliae spores in the scarab beetle is 4 × 10⁻⁶. 7 spores / mL.

7. The application of the biological pesticide composition for controlling brown planthoppers as described in claim 4 in the control of brown planthoppers.

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