JP2009298736A - Controlling agent of hardly controllable soilborne disease by gallic acid-related material, and method for controlling hardly controllable soilborne disease by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new controlling technique of a low environmental load-type by using a biologically active substance originated from a plant, and having excellent antimicrobial activity only against hardly controllable soilborne diseases such as bacterial wilt and actinomycosis. <P>SOLUTION: The controlling agent of the hardly controllable soilborne disease contains methyl gallate of one kind of a polyphenol or a derivative thereof as a main active ingredient. The hardly controllable soilborne disease of a target can selectively be controlled by the excellent antimicrobial activity possessed by the methyl gallate derivative. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control agent for difficult-to-control soil diseases (green wilt disease, actinomycosis) containing methyl gallate and derivatives thereof as an active ingredient, and a control method using the same.

The bacteria of the genus Pseudomonas, Ralstonia solanacearum, infects various crops such as cucurbits and solanaceae such as potatoes, tomatoes, eggplants, peppers, tobacco, etc., withering the plant body, and also leading to death It is a pathogenic bacterium. Since bacterial wilt spreads over the entire field due to rain, the amount of outbreak increases in areas with high rainfall, causing great damage. Streptomyces scabies belonging to the genus Streptomyces is a pathogenic fungus that forms scabs and bite-like lesions mainly on the surface of potatoes such as potatoes and sweet potatoes. It causes the problem of being damaged.
These pathogenic bacteria and disease actinomycetes are known as causative agents of diseases that are very difficult to control, and the establishment of countermeasures is an issue.

  Conventionally, soil disinfection with methyl bromide has been used to control such soil diseases. Methyl bromide has a wide range of bactericidal properties against many soil diseases such as viruses, bacteria, filamentous fungi, nematodes, soil pests and weeds, and is effective even under low temperature conditions. Since it is simple, it has been widely used.

  However, at the "Montreal Protocol Parties Meeting" held in 1992, methyl bromide was regulated as an ozone-depleting gas, and it was decided to abolish it on January 1, 2005. Therefore, there is a need for a control method that replaces methyl bromide.

As one of them, a method using a chloropicrin-containing preparation having excellent antibacterial and nematicidal properties is known. However, since chloropicrin is highly volatile and irritating, it cannot be used in places where residential areas and farms are close to each other, and it is relatively ineffective against pathogenic bacteria that live in deep parts of soil. Has drawbacks. Furthermore, with the recent revision of the Agricultural Chemicals Control Law and increasing consumer interest in “food safety and security”, the range of use tends to be limited. Under these circumstances, there is an increasing demand for development of new environmentally friendly control technologies at production sites.

Chemical pesticides such as methyl bromide and chloropicrin are generally excellent in immediate effect, but problems such as a decrease in productivity of farmland due to long-term continuous use and environmental burden have been pointed out. On the other hand, biological pesticides using natural enemies, microorganisms, and the like are derived from natural products and have little persistence in the environment, and are attracting attention as a means of sustained disease control. Biological pesticides have advantages such as a low possibility of emergence of resistant bacteria and high selectivity against pathogenic bacteria and pests compared to chemical pesticides, but they are difficult to use and are economical and have long-term storage stability. There are still many issues in this respect, so research and development is actively underway.

As a technique for controlling difficult-to-control soil diseases such as bacterial wilt disease and wilt disease using biological pesticides, the present inventor has developed the American Fluorobacterium Gerolinium L. It has been announced that the above-ground extract is effective in controlling the above-mentioned soil diseases (see Patent Document 1). American fuuro is a wild grass that grows naturally in Okinawa Prefecture and forms a community, and since it originally exists in nature, it can be considered to be able to provide control technology with less impact on the environment.

By the way, the biological pesticide sometimes refers to a special chemical substance such as an antibiotic or a toxin contained in an organism in a broad sense. So far, soil disease control methods using plants containing antibacterial components include, for example, extracts of cinnamon silicate and pepper, and oils using Phytophthora nicotianae, potato scab disease Streptomyces scabies by Geranium plate, and papaya seedlings by garlic Fusarium oxysporum f. Tomato wilt caused by blight Phytophthora palmivora sp. The effectiveness of lycopersici has been reported.

In the above-mentioned method for controlling soil diseases caused by American fulva, the present inventor mixed the raw grass and dry matter of the leaf portion of American fulosa with the soil and sprayed it, so that the components eluted in the soil act on the soil microorganisms. In addition, it has been confirmed at the field level that good antibacterial activity can be obtained (Non-patent Document 1). And when the active ingredient contained in this American Fu was isolated and identified, it became clear that ethyl gallate which is a kind of polyphenol has antibacterial activity (Non-patent Document 2).
However, the antibacterial property of ethyl gallate alone does not sufficiently explain the excellent control effect of American furo (Non-Patent Document 2), and in the development of control technology using American furo, its antibacterial action It is desired to elucidate the mechanism.

On the other hand, gallic acid esters have been conventionally used in food additives as antioxidants. Mainly known as food additives are propyl gallate, octyl gallate, and dodecyl gallate, and the antibacterial activity of these gallic acid esters against Escherichia coli etc. is said to be higher as the carbon chain of the ester moiety is longer. It has been broken.
In addition, methyl gallate is used for disinfectants, astringents, or ophthalmology.
Furthermore, Patent Document 2 discloses that gallic acid derivatives obtained by reacting a gallic acid ester derived from a natural product with a halide or a sulfonic acid ester in an organic solvent in the presence of an alkali include Gram such as Bacillus subtilis and Staphylococcus aureus. It has been disclosed to exhibit selective antibacterial properties against positive bacteria.

Thus, although the antibacterial activity of gallic acid esters has been clarified so far, the effect is only confirmed in compounds having a large number of carbon atoms in the ester moiety and compounds insoluble in water. In addition, there is no mention of the possibility of controlling difficult-to-control soil diseases.

Japanese Patent No. 3831756 JP 2002-161075 A Weeds Research, 51, 28-30 (2006) Plant Protection, 62, 90-95 (2008)

Therefore, the present invention provides a novel low-environmental load-control technology using a bioactive substance derived from the American ful, which elucidates the bactericidal action of the American ful of hard-to-control soil diseases such as bacterial wilt and actinomycosis. The task is to do.

As a result of exhaustively isolating and identifying antibacterial components contained in American ful, the present inventors have clarified that the active ingredient is a gallic acid-related substance and investigated its structure-activity relationship. Contrary to predictions from the structure-activity relationship of gallic acid-related substances against pathogenic bacteria known to date, the antibacterial activity becomes stronger as the carbon chain of the ester site of gallic acid-related substances becomes shorter, and the remarkable antibacterial activity on methyl gallate As a result, the present invention has been completed.
That is, the present invention provides (I) the following general formula (1)

・・・（１）
［（１）式中、Ｒ₁，Ｒ₂，Ｒ₃は、水素原子、アルカリ金属、アルカリ土類金属、アンモニウム塩あるいは炭素数１から３のアルキル基のいずれか１つを表わし、Ｒ₁，Ｒ₂，Ｒ₃のうちの少なくとも1つは水素原子を表わす。］で示される水溶性没食子酸メチル誘導体のうち少なくとも１種を有効成分として含有する難防除土壌病害用防除剤を提供する。
本発明は、（II）没食子酸メチルを有効成分として含有する難防除土壌病害用防除剤を提供する。
また、本発明は、（III）前記難防除土壌病害が青枯病及び/又は植物放線菌病であることを特徴とする上記（I）又は（II）に記載の難防除土壌病害用防除剤を提供する。
更に、本発明は、（IV）上記（I）〜（III）のいずれか１項に記載の難防除土壌病害用防除剤を用いて土壌消毒を行うことを特徴とする難防除土壌病害防除方法を提供する。

... (1)
[In formula (1), R _1, R _2, R ₃ represents a hydrogen atom, an alkali metal, alkaline earth metal, any one of an alkyl group having from ammonium salt or C 1 -C 3, R _1, At least one of R ₂ and R ₃ represents a hydrogen atom. ] The control agent for a difficult-to-control soil disease containing at least 1 sort (s) among the water-soluble methyl gallate derivatives shown by this as an active ingredient.
The present invention provides (II) a difficult-to-control soil disease control agent containing methyl gallate as an active ingredient.
The present invention also provides (III) the control agent for difficult-to-control soil diseases as described in (I) or (II) above, wherein the soil-resistant disease is bacterial wilt and / or plant actinomycosis I will provide a.
Furthermore, the present invention provides (IV) a method for controlling a difficult-to-control soil disease, wherein soil disinfection is performed using the control agent for a difficult-to-control soil disease described in any one of (I) to (III) above. I will provide a.

In the present invention, disinfecting bacterial wilt fungi and soil disease actinomycetes using natural product-derived components having an excellent antibacterial action, resulting in a problem that occurs chronically in potato producing areas such as Okinawa. It becomes possible to effectively control blight. For this reason, it can replace with the damage avoidance method which relied on the rotation with the conventional gramineous crops, and can provide the countermeasure in which a continuous control is possible.
Moreover, according to this invention, since the target soil disease can be selectively controlled, the risk of disturbing the soil environment as in the conventional soil disinfection method using chemical pesticides can be reduced. Therefore, according to the present invention, it is possible to provide a new difficult control technology that is both environmentally friendly and highly effective, which has the advantages of biological pesticides and chemical pesticides.

The difficult-to-control soil disease control agent of the present invention contains methyl gallate or a derivative thereof (hereinafter referred to as methyl gallate derivative), which is a kind of polyphenol, as a main active ingredient. Thereby, it becomes possible to selectively control the target difficult-to-control disease by the excellent antibacterial action of the methyl gallate derivative.
In addition, such methyl gallate derivatives have been found in the extract, focusing on the antibacterial properties of American fus. Therefore, because it is derived from a natural product, the advantages of both biological and chemical pesticides are low environmental impact and easy to use and economical by using it as an active ingredient of a control agent. It is expected that it will be possible to provide innovative new pesticides with
As the methyl gallate derivative, any of the methyl gallate derivatives represented by the following general formula (1) that can be solubilized in water can be used.

・・・（１）
ここで、（１）式中、Ｒ₁，Ｒ₂，Ｒ₃は、水素原子、アルカリ金属、アルカリ土類金属、アンモニウム塩あるいは炭素数１から３のアルキル基のいずれか１つを表わし、Ｒ₁，Ｒ₂，Ｒ₃のうちの少なくとも1つは水素原子を表わす。

... (1)
Here, in the formula (1), R ₁ , R ₂ and R ₃ represent any one of a hydrogen atom, an alkali metal, an alkaline earth metal, an ammonium salt or an alkyl group having 1 to 3 carbon atoms, and R _At least one of ₁ , R ₂ and R ₃ represents a hydrogen atom.

Specifically, methyl gallate, gallic acid methyl ester-3-methyl ether, gallic acid methyl ester-4-methyl ether, gallic acid methyl ester-3-ethyl ether, gallic acid methyl ester-3,5- Any of methyl ether and the like can be used, and methyl gallate is particularly preferred from the viewpoint of easy availability of raw materials and production costs. These may be used individually by 1 type, or may use 2 or more types together.

Such a methyl gallate derivative is found in plants in the same manner as the methyl gallate derivative, and is combined with ethyl gallate which is already known to have antibacterial activity against bacterial wilt fungus and soil disease actinomycetes. May be used. Thereby, the more excellent antimicrobial effect can be acquired.
Examples of the methyl gallate derivative include those produced by chemical synthesis, those extracted, separated and purified from plant bodies such as American fulu, or extracts such as lignin obtained from plant bodies as chemical raw methods and biosynthesis. Any of those synthesized by a method in which these are appropriately combined can be used, and is not particularly limited.

When extracting from a plant body, the plant body is not particularly limited as long as it contains a methyl gallate derivative, and any conventionally known one can be used. What is necessary is just to select suitably what is excellent in these.
In the case of using American ful as the plant body, it is preferable to use leaves and stems because many active ingredients are contained in the above-ground part. At this time, either fresh grass or dry matter may be used.
Such a methyl gallate derivative can be used as a control agent by appropriately blending with liquid and solid carriers, as well as components necessary for effectively exerting a bactericidal effect against diseases such as stabilizers and formulation adjuvants. It becomes possible.

Examples of the control method using the difficult-to-control soil disease control agent include a method of disinfecting the soil by mixing and irrigating the difficult-to-control soil disease control agent in the soil.
The above mixing treatment and irrigation treatment may be performed at the time of planting, or additional irrigation may be performed at an appropriate time. In addition, since the root depth varies depending on the crop, it is desirable to appropriately set conditions such as the depth to be applied and the amount of drug used.
Furthermore, after mixing the control agent for difficult-to-control soil diseases in the soil, it is possible to more effectively control the difficult-to-control soil diseases by using solar heat soil disinfection, covering straw covering, or the like.

Thus, the methyl gallate derivative in the control agent for difficult-to-control soil diseases soaked in the soil elutes into the soil at a constant rate, and selectively kills the target pathogen. Demonstrate. Therefore, according to the present invention, it is possible to provide a new environment-friendly difficult control technique with less risk of disturbing the soil environment.

EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, the technical scope of this invention is not limited to these illustrations.
Example 1
In the case of using methyl gallate as an active ingredient as a control agent for difficult-to-control soil diseases according to the present invention, the control effect against bacterial wilt and phytopathogenic actinomycetes was examined.

[Preparation of methyl gallate from American furo]
First, methyl gallate used as an antibacterial component in this example was prepared by separation and purification of wild grass native to Okinawa Prefecture from American ful.
That is, 100 g of above-ground parts (leaves and stems) of raw grass (Geranium carolinianum L.) were immersed in 1,200 ml of 70% ethanol at room temperature for 2 weeks to extract the active ingredients contained in American fuol. .

The obtained 70% ethanol extract was filtered, and the filtrate was concentrated. The concentrated solution was partitioned with hexane at room temperature to remove low-polarity inert substances, and then partitioned with ethyl acetate for activity. A fraction was obtained.
The obtained ethyl acetate extract was purified by silica gel column chromatography and then reverse phase column chromatography to prepare methyl gallate.

[Evaluation of antibacterial activity of methyl gallate against bacterial wilt of bacterial wilt]
10 ml of a potato semi-synthetic medium was solidified in a 9 cm petri dish, and 100 μl of a bacterial solution of bacterial wilt was added dropwise, and the mixture was spread evenly with a conical rod. Methyl gallate was soaked in a paper disk as a methanol solution, and then the solvent was removed under reduced pressure. The paper disc was placed in the inoculated petri dish and allowed to stand at 28 ° C. for 3 days, and the diameter of the formed growth inhibition circle was measured. The results are shown in Table 1 below.
In Table 1, the numerical value represents the diameter (cm) of the growth inhibition circle of bacterial wilt.

Comparative Examples 1-5
Methyl gallate used as an antimicrobial component in Example 1 was gallic acid (referred to as Comparative Example 1), ethyl gallate (Comparative Example 2), propyl gallate (Comparative Example 3), octyl gallate (Comparative Example 4) In addition, the antibacterial activity against bacterial wilt fungus was investigated in the same manner as in Example 1 except that each was replaced with dodecyl gallate (Comparative Example 5). The results are also shown in Table 1 above.
In Table 1, the case where no growth inhibition circle was observed is represented as “-(minus)”.

As is clear from Table 1, the antibacterial activity of gallic acid and its alkyl ester against bacterial wilt fungus depends on the difference in the carbon chain of the ester moiety, and the acid (Comparative Example 1) and the ester moiety having a large number of carbon atoms In (Comparative Examples 2 to 5), sufficient antibacterial activity was not observed.
On the other hand, in Example 1 using methyl gallate, it was clarified that extremely excellent antibacterial activity was obtained, and that there was a sufficient effect even at a relatively low dose of 0.5 μmol. . This result shows that the antibacterial activity against bacterial wilt fungus has the opposite tendency, unlike the antibacterial activity of gallic acid-related substances known in the past.

Examples 2 and 3 and Comparative Examples 6 to 12
Next, the antibacterial spectrum of methyl gallate other than bacterial wilt disease was examined.
That is, in the case where the bacterial wilt used as a difficult-to-control soil disease in Example 1 was changed to various pathogens, the antibacterial activity was evaluated in the same manner as described above. Examples of the test bacteria include potato scab (Streptomyces scabies: Ss (Example 2), S. acidiscabies: Sa (Example 3)), sweet potato charcoal fungus (Macrophomina phaseolina: Mp (Comparative Example 6)), lettuce Sclerotinia sclerotiorum (Ssc (Comparative Example 7)), Fusarium oxysporum f. Sp. , Chrysanthemum spot bacteria (Pseudomonas chicholli: Pc (Comparative Example 10)), Rakkyo soft rot fungus (Erwinia carotovora: Ec (Comparative Example 11)) It was. The results are shown in Table 2.

As shown in Table 2, methyl gallate showed antibacterial activity against two bacterial species of potato scab (Ss, Sa), which are difficult-to-control disease actinomycetes, but as shown in Comparative Examples 6-11 Phytopathogenic filamentous fungi such as sweet potato charcoal fungus (Mp), lettuce sclerotia fungus (Ssc), vine rot fungus (Fo), papaya soft rot fungus (Pn), chrysanthemum spot fungus (Pc) and rakki soft rot fungus It was found that the growth of phytopathogenic bacteria such as (Ec) was not inhibited.

From the above results, it was revealed that the antibacterial spectrum is limited to bacterial wilt and phytopathogenic actinomycetes.
Therefore, the methyl gallate derivative contained in American fulu has an excellent antibacterial action selectively against bacterial wilt and phytopathogenic actinomycetes, so use a control agent for difficult-to-control soil diseases using this as an active ingredient. By doing so, it is expected that it will be possible to develop a new chemical pesticide with a low environmental load that does not disturb the soil environment.

Claims (4)

The following general formula (1)

... (1)
[In formula (1), R _1, R _2, R ₃ represents a hydrogen atom, an alkali metal, alkaline earth metal, any one of an alkyl group having from ammonium salt or C 1 -C 3, R _1, At least one of R ₂ and R ₃ represents a hydrogen atom. ] The control agent for difficult-to-control soil disease characterized by containing at least 1 sort (s) among the water-soluble methyl gallate derivatives shown by this. A control agent for difficult-to-control soil diseases, comprising methyl gallate as an active ingredient. The hard-to-control soil disease control agent according to claim 1 or 2, wherein the hard-to-control soil disease is bacterial wilt disease and / or plant actinomycete disease. A difficult-to-control soil disease control method, wherein soil disinfection is performed using the control agent for difficult-to-control soil diseases according to any one of claims 1 to 3.