JP2011246447A - Plant disease controlling agent and plant disease controlling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plant disease controlling agent which comprises a compound reinforcing the defence force of plants as an effective component.SOLUTION: The plant disease controlling agent containing a terpenoid-related compound, particularly, sclareol as an effective component exhibits a plant disease controlling effect of increasing the defence force of plants and deriving disease resistance and is effective to various plant diseases such as a bacterial wilt disease, a damping-off disease, botrytis cinerea, burkholderia plantarii, burkholderia glumae and gibberella fujikuroi.

Description

  The present invention relates to a plant disease control agent and a plant disease control method. More specifically, the present invention relates to a plant disease control agent and a plant disease control method using the property of enhancing the protective power of terpenoid-related compounds.

Crop diseases caused by infection with pathogenic microorganisms such as viruses, bacteria, and filamentous fungi are one of the causes of reduced yield and are a major agricultural problem. In order to prevent such diseases, biological control, chemical control, physical control and the like have been implemented. However, there are many diseases that are difficult to control even with such attempts. One such difficult-to-control disease is bacterial wilt.
Bacterial wilt is a plant disease caused by bacteria that infect and die more than 200 kinds of plants such as eggplant and tomato. The bacterial wilt fungus survives deeply in the ground for a long time and reappears when a suitable host plant is planted. It is a disease that brings.
As methods for controlling bacterial wilt disease, soil fumigation with methyl bromide, biological control using Pseudomonas, etc., cultivated control such as avoiding continuous cropping and diseased strain removal, and using resistant varieties as rootstocks The grafting method has been tried, but there are still many problems to be solved in terms of labor and control effects.

  A possible means for solving such a problem is the use of a defensive power enhancer. The defensive power enhancer is also called a defensive factor enhancer, and is a drug exhibiting a disease control effect by enhancing the defensive power against diseases inherent in plants to induce disease resistance and fungal resistance. If the active ingredient of the drug is naturally derived, it can be considered that the burden on the environment can be reduced. Therefore, a control method using the drug has recently attracted attention as an environmental conservation type disease control method.

  As a defense power enhancer with respect to bacterial wilt, the defense power enhancer which uses the yeast extract described in the nonpatent literature 1 as a raw material is disclosed, for example.

Nikkatsu Disease Report 73: 94-101 (2007)

However, there are very few knowledge about the defense power enhancer with respect to bacterial wilt, and further improvement is needed in order to improve the physiological activity of a plant and to obtain the disease prevention effect.
Furthermore, since there are cases in which multiple diseases coexist in an actual agricultural field, as a characteristic of the defense-intensifying agent, it is more effective to control multiple diseases than to specifically control only one disease. desirable. For that purpose, it is important to search for a compound having an effective action not only as bacterial wilt but also as a defense-intensifier against a plurality of diseases.

  Under such circumstances, an object of the present invention is to provide a plant disease control agent comprising a compound that enhances the defense power of plants as an active ingredient, and a method for controlling plant diseases such as bacterial wilt disease using the compound. is there.

As a result of intensive studies to solve the above-mentioned problems, the present inventor is a substance that enhances the defense against bacterial wilt in a plant in which a resistance reaction against bacterial wilt is induced (protective power enhancer). Based on the hypothesis that a large amount is produced, we tried to search for a defense-increasing agent, and purified the target compound from the resistance-induced tobacco. It has been found that it has an effect of controlling bacterial wilt disease despite having no antibacterial activity.
Furthermore, when we investigated whether sclareol had a controlling effect on diseases other than bacterial wilt disease, sclareol was found to have gray mold disease other than bacterial wilt disease, rice seed infectious diseases (rice seedling bacterial disease, rice seedling disease, It has been found that it also has a controlling effect against plant diseases such as rice blast blight). Furthermore, the present inventors have found that terpenoid-related compounds other than sclareol also have the same action, leading to the present invention.

That is, the present invention relates to the following inventions.
<1> A plant disease control agent comprising a terpenoid-related compound as an active ingredient.
<2> The plant disease control agent according to <1>, wherein the terpenoid-related compound is sclareol.
<3> The plant according to the above <1> or <2>, wherein the plant disease is bacterial wilt, blight, gray mold, rice seedling bacterial disease, rice blast bacterial disease or rice seedling disease Disease control agent.
<4> A method for controlling plant diseases in which a target plant absorbs a terpenoid-related compound.
<5> The method for controlling plant diseases according to <4>, wherein the terpenoid-related compound is sclareol.
<6> The plant according to <4> or <5>, wherein the plant disease is bacterial wilt, blight, gray mold, rice seedling bacterial disease, rice blast bacterial disease, or rice blast disease Disease control method.
<7> The plant disease control method according to any one of <4> to <6>, wherein the target plant is a solanaceous family, a cruciferous family, a grass family, or a cucurbitaceae.

  ADVANTAGE OF THE INVENTION By this invention, the chemical | medical agent and plant disease control method which show the plant disease control effect which raises the defense power of a plant and induces disease resistance are provided.

It is a photograph which shows the withering disease control effect of sclareol with respect to the tobacco cultivated hydroponically. It is a photograph which shows the withering disease control effect of sclareol with respect to the tobacco grown in soil. It is a photograph which shows the bacterial wilt disease control effect of sclareol with respect to the tomato grown in soil. It is a figure which shows the relationship between the number of days after inoculation with bacterial wilt and the disease symptom index in the tomato after processing sclareol. It is a photograph which shows the bacterial wilt disease control effect of sclareol with respect to Arabidopsis thaliana cultivated in soil. It is a photograph which shows the effect of sclareol on the growth of bacterial wilt. It is a figure which shows the withering disease control effect of (11E, 13E) -labda-11,13-diene-8α, 15-diol on tobacco cultivated in soil. It is a photograph which shows the effect of (11E, 13E) -labda-11,13-diene-8α, 15-diol on the growth of bacterial wilt.

The plant disease control agent of the present invention is characterized by containing a terpenoid-related compound as an active ingredient.
In the present invention, the “terpenoid-related compound” is a general term for compounds composed of isoprene having a basic skeleton of C ₅ H ₈ having a multiple of 5 carbon atoms. Specifically, monoterpenoids such as limonene, menthol, linalool, pinene, pyrethrin, thymol and real, sesquiterpenoids such as ipomemarone, abscisic acid, guaiazulene and santonin, sclareol, (11E, 13E) -labda-11,13 -Diterpenoids such as diene-8α, 15-diol, gibberellin and stevioside, saster terpenoids such as ophioborin and zerafarnesol, and triterpenoids such as hederagenin, amylin and limonin.
Among these, sclareol and (11E, 13E) -labda-11,13-diene-8α, 15-diol are preferable, and sclareol is more preferable in that it has a higher disease control effect.

Sclareol (sclareol, labda-14-ene-8,13-diol) is a kind of diterpenoid compound having the structure of the following formula (1), and resistance is induced by a conventionally known method. It can be isolated and purified from plants such as.
Sclareol is a known substance and is commercially available (for example, Sigma-Aldrich). Even without such separation and purification, it is possible to obtain a commercial product and subject it to a plant disease resistance test.

The terpenoid-related compounds (including solvates) including sclareol, which are active ingredients of the plant disease control agent of the present invention, have no or almost no anti-bacterial fungal activity per se. If the target plant is treated, bacterial wilt can be suppressed.
In the present invention, “green wilt” refers to a disease caused by infection with Ralstonia solanacearum, a soil pathogenic bacterium. In addition, when this bacterium is applied to tobacco, the disease caused by it is called “blight disease”. Furthermore, the “anti-blight fungus activity” means an action of inhibiting the growth and growth of bacteria by directly acting on the metabolism and the like of the bacterial blight fungus.
In addition, terpenoid-related compounds (especially sclareol) are also characterized by having a controlling action against various plant diseases such as gray mold disease, rice seedling blight disease, rice blast bacterial disease, and rice seedling disease. And
In the present invention, gray mold disease is caused by infection with Botrytis cinerea which is a filamentous fungus having pathogenicity to many kinds of plants, and rice seedling bacterial disease is caused by infection with Burkholderia plantarii which is a pathogenic bacterium. Bacterial blight is caused by infection with the pathogenic bacterium Burkholderia glumae, and rice seedling disease is caused by infection with the pathogenic fungus Fusarium moniliforme.

  The target plant is not particularly limited as long as it is infected with bacterial wilt fungus (growth blight fungus), gray mold fungus, rice seedling blight fungus, rice blast fungus fungus, rice blast fungus, etc. , For example, eggplant, cruciferous, gramineous, leguminous, cucurbitaceae, convolvulaceae, liliaceae, chrysanthemum, taroaceae, ginger, serpentine, yam, rose, citrus, grape , Plants belonging to the family of pineapple family, scallop family, myrtaceae family, willow family family, red department family family, gentian family family and family family.

  In the plant disease control agent of the present invention, the terpenoid-related compound may be contained as a salt, and the form of the salt is not particularly limited. For example, an alkali metal salt (sodium salt, potassium salt, lithium salt, etc.) ), Alkaline earth metal salts (calcium salts, magnesium salts, etc.), metal salts (aluminum salts, iron salts, zinc salts, copper salts, nickel salts, etc.), inorganic salts (acetates, ammonium salts, etc.), organic amine salts (Dibenzylamine salt, glucosamine salt, ethylenediamine salt, diethylamine salt, triethylamine salt, dicyclohexylamine salt, diethanolamine salt, tetramethylammonia salt, etc.), amino acid salt (glycine salt, lysine salt, arginine salt, ornithine salt, asparagine salt, etc.) ) And the like.

  When the plant disease control agent of the present invention is used as an agricultural and horticultural control agent, a terpenoid-related compound which is an active ingredient can be used in an appropriate dosage form according to the purpose. Usually, terpenoid-related compounds, which are active ingredients, are diluted with an inert liquid or solid carrier, and surfactants, etc. are added as necessary, and powders, wettable powders, emulsions, granules, etc. Can be used in The blending ratio of the terpenoid-related compound, which is an active ingredient, is appropriately selected as necessary, but 0.1 to 20% (by weight) is used for powders and granules, and 5 to 5 is used for emulsions and wettable powders. 80% (weight) is appropriate.

Examples of suitable carriers include solid carriers such as talc, bentonite, clay, kaolin, diatomaceous earth, white carbon, vermiculite, slaked lime, silica sand, ammonium sulfate, and urea, and liquid carriers such as isopropyl alcohol, xylene, cyclohexanone, and methylnaphthalene. It is done.
Suitable surfactants and dispersants include, for example, dinaphthylmethane sulfonate, alcohol sulfate ester salt, alkylaryl sulfonate, lignin sulfonate, polyoxyethylene glycol ether, polyoxyethylene alkylaryl ether, polyoxyethylene Examples include ethylene sorbitan monoalkylate.
Suitable auxiliaries include carboxymethyl cellulose.

  The plant disease control agent of the present invention can be used by spraying these leaves as they are or by diluting them, foliage spraying, seed treatment, soil application, water surface application or nursery box application. These application rates vary depending on the type of compound used, target disease, occurrence tendency, degree of damage, environmental conditions, dosage form used, and the like. For example, when using it as it is like a powder agent and a granule, it is good to select suitably from the range of 0.1g-5kg per 10 ares in conversion of an active ingredient, Preferably it is 1g-1kg. When used in a liquid form, such as an emulsion and a wettable powder, it may be appropriately selected from the range of 0.1 ppm to 10,000 ppm, preferably 10 to 3,000 ppm in terms of active ingredients.

  Furthermore, the plant disease control agent of the present invention is an insecticide, other fungicide, herbicide, plant growth regulator, fertilizer, other known plant active agents, as long as the disease control activity is not inhibited. You may mix with arbitrary components, such as a growth promoter. Suitable agents include Daconil 1000, Techlead C flowable, Benlate wettable powder, Provoise granule wettable powder, Flupica flowable, Agrosulin emulsion, Admeier emulsion and the like.

  The plant disease control agent of the present invention is obtained by dissolving a terpenoid-related compound, which is an active ingredient, in a solvent. The solvent does not inhibit the dissolution and dispersion of the contained terpenoid-related compound, and the target plant A solvent that does not have an adverse effect may be used, and methanol, ethanol, and the like are appropriately used. Usually, a terpenoid-related compound solution dissolved in the aforementioned solvent is diluted with water and used.

The concentration of the terpenoid-related compound contained in the plant disease control agent of the present invention is not particularly limited as long as the disease control activity is expressed, taking into account the type of terpenoid-related compound, the balance between the plant disease control effect and the application amount, etc. It is appropriately determined and is usually about 50 to 500 μM, preferably 75 to 400 μM.
If the concentration of the terpenoid-related compound is too low, the disease control effect may not be sufficient, and if it is too high, problems such as yellowing leaves may occur.
In the case of sclareol, which is a suitable terpenoid-related compound, a sufficient disease control effect is obtained when the concentration is 50 μM or more, and a remarkable disease control effect (especially bacterial wilt control effect) is obtained at 75 μM, and 100 μM. With the above, a more remarkable disease control effect (especially bacterial wilt control effect) can be obtained.

  The plant disease control method of the present invention is characterized in that a target plant absorbs a terpenoid-related compound. Specifically, a method of immersing the plant disease control agent of the present invention in the root of the target plant can be mentioned. That is, the usual soil cultivation method and hydroponics method are mentioned.

  The method for controlling plant diseases of the present invention is effective against various plant diseases such as bacterial wilt disease, bacterial wilt disease, gray mold disease, rice seedling bacterial disease, rice blast bacterial disease, or rice blast disease. In particular, it is suitably applied to bacterial wilt and blight.

Examples of the target plant include plants infected with the above-mentioned bacterial wilt fungus (bacterial fungus), gray mold fungus, rice seedling bacterial fungus, rice blast fungus bacterial fungus, rice seedling fungus fungus, and the like.
Among them, the disease control method of the present invention is a solanaceous plant such as wolfberry, ashridokoro, physalis, eggplant, potato, tomato, pepper, tobacco, datura, tsukubanasagao, Arabidopsis thaliana, rape. , Cabbage, broccoli, Chinese cabbage, Japanese radish, wasabi, cucumber, watermelon, pumpkin, melon, which are cucurbitaceae, and rice, wheat, and corn, which are gramineous plants. Among these, it is particularly effective against tomato, tobacco, Arabidopsis, rice and cucumber.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is changed.

<Separation and purification of sclareol>
Sclareol was separated and purified from the resistance-induced tobacco by the following procedure.
10 kg of fresh heavy tobacco leaves inoculated with 8266 strains of bacterial wilt and cultured for 2 days were immersed and extracted in 40 L of 80% acetone at 4 ° C. for 24 hours. The extract was filtered, and the aqueous layer obtained after concentrating the filtrate was adjusted to pH 3 with hydrochloric acid and extracted three times with an equal amount of ethyl acetate. The extracted ethyl acetate layer was extracted twice with an equal amount of 5% sodium hydrogen carbonate, and the extracted ethyl acetate layer was recovered. The recovered ethyl acetate layer was added to a glass column (3 cm inner diameter × 50 cm length) previously packed with silica gel (Wakogel C-200; Wako Chemical Co., Ltd.), and hexane containing 10% ethyl acetate was allowed to flow through the column. The eluted fraction was collected and concentrated, added to a C ₁₈ Sep-Pak Vac cartridge (Waters), and eluted with methanol containing 20% distilled water. The eluate was collected and concentrated, and then separated by high performance liquid chromatography. Separation conditions were a CAPCELL PAK C ₁₈ column (10 mm inner diameter × 15 cm length; Shiseido), and a linear gradient from 25% to 100% of acetonitrile concentration for 60 minutes was flowed at 6 mL / min. Under this condition, a fraction eluted at a retention time of 55 to 60 minutes was collected, concentrated, and then separated again by high performance liquid chromatography. Separation conditions were a CAPCELL PAK C ₁₈ column (4.6 mm inner diameter × 25 cm length; Shiseido), 90% acetonitrile, flow rate 6 mL / min, and peak fraction appearing at a retention time of 11.1 min under these conditions. Includes sclareol.

  In order to confirm the suppressive effect of sclareol on plant diseases, experiments of Examples 1 to 7 below were conducted.

Example 1
A drug having a concentration of sclareol of 100 mM was obtained by adding an appropriate amount of sclareol to methanol and stirring until uniform.
Next, the 4-week-old tobacco seedling (Samsung NN) previously hydroponically cultivated in the nutrient solution was added to the nutrient solution so that the sclareol was 100 μM and hydroponically cultivated for 2 days. Cultivated. Thereafter, the roots of the seedlings were inoculated with 8225 strains of blight fungus equal to the formation of 10 ⁸ colonies per mL, and observed for several days. In addition, as a control, tobacco seedlings treated in the same manner were inoculated with a nutrient solution containing 0.1% methanol but no drug added, and the same observation was performed.
FIG. 1 shows a photograph of a tobacco seedling 7 days after inoculation with a blight fungus. The white line in the figure indicates that the length is 2 cm. By injecting sclareol into the nutrient solution, we were able to suppress the occurrence of blight.

Example 2
An appropriate amount of sclareol was added to methanol and stirred until uniform, thereby obtaining a drug having a concentration of sclareol of 100 mM and diluted with water to a final concentration of 100 μM.
Subsequently, the tobacco diluted in the above-described manner was poured into tobacco seedlings (variety name: Samsung NN) previously cultivated in the soil for about 2 months, and the soil was continuously cultivated for 2 days.
Thereafter, the root of the plant body was inoculated with 8225 strains of blight fungus equal to the formation of 10 ⁸ colonies per mL, and observed for several days. In addition, as a control, tobacco seedlings treated in the same manner were inoculated with a nutrient solution containing 0.1% methanol but no drug added, and the same observation was performed.
FIG. 2 shows a photograph of the tobacco plant 7 days after inoculation with the withering fungus. The white line in the figure indicates that the length is 10 cm. Sclareol also showed control effects against the occurrence of withering disease in tobacco grown in soil.

Example 3
An appropriate amount of sclareol was added to methanol and stirred until uniform, thereby obtaining a drug having a concentration of 100 mM and diluted with water to a final concentration of 50, 75, and 100 μM. Subsequently, the tomato plant (variety name: Ponderosa) previously cultivated in the soil for about 2 months was poured into the soil with the diluted chemical as described above, and the soil was continuously cultivated for 2 days.
Thereafter, the root of the plant body was inoculated with 8107 strains of bacterial wilt disease equivalent to the formation of 10 ⁸ colonies per mL, and observed for several days. Further, as a control, tomato plants treated in the same manner were inoculated with a nutrient solution containing 0.1% methanol, but no chemical was added, and the same observation was performed.
FIG. 3 shows a photograph of a tomato plant 6 days after inoculation with bacterial wilt using a drug having a sclareol concentration of 100 μM. The white line in the figure indicates that the length is 10 cm.
In addition, FIG. 4 shows the relationship between the number of days after inoculation with bacterial wilt and the disease symptom index when drugs of each sclareol concentration are used. The disease symptom index (onset index) means the degree of damage caused by the disease. In other words, the higher the value, the greater the damage caused by the disease.
Occurrence of bacterial wilt could be remarkably suppressed by direct administration to nutrient solution or soil at a concentration of 75 μM or more.

Example 4
An appropriate amount of sclareol was added to methanol and stirred until uniform, thereby obtaining a drug having a concentration of sclareol of 100 mM and diluted with water to a final concentration of 100 μM.
Next, the Arabidopsis seedlings (variety name: Colombia) previously cultivated in soil for about 2 months were poured into the soil with the above-diluted drug and cultivated in soil for 2 days.
Thereafter, the plant root was inoculated with RS1000 strain of bacterial wilt disease in an amount equal to 10 ⁸ colonies per mL, and observed for several days. In addition, as a control, Arabidopsis plants treated in the same manner were inoculated with a nutrient solution containing no drug but containing 0.1% methanol, and the same observation was performed.
FIG. 5 shows a photograph of Arabidopsis seedlings 7 days after inoculation with bacterial wilt.
Sclareol was effective in controlling bacterial wilt of Arabidopsis grown in soil.

Example 5
<Antimicrobial activity against bacterial wilt>
The following experiment was conducted to confirm the presence or absence of antibacterial activity of sclareol against bacterial wilt of bacterial wilt.
An agar medium containing 100 μM sclareol or 0.1% methanol as a control was inoculated with the B. subtilis 8225 strain and cultured. Photo on the first day after inoculation.
FIG. 6 shows a photograph on the first day after inoculation. There was no clear difference between them, and sclareol itself did not show antibacterial activity against bacterial wilt.

Example 6
<Control effect against cucumber gray mold>
In order to examine the control effect of sclareol against diseases other than bacterial wilt, the following experiment was conducted.
First, an appropriate amount of sclareol was added to methanol and stirred until uniform, whereby a drug having a concentration of sclareol of 100 mM was obtained and diluted with water to a final concentration of 100 μM. Next, with respect to cucumbers in the cotyledon stage (variety: Sagamihanjiro) grown in a 5.5 cm plastic pot to which fertilizer soil was added in advance, 100 μM sclareol or a control group with water alone at a rate of 10 mL per pot Irrigated.
On the second day after sclareol irrigation, spores of gray mold fungus (Botrytis cinerea 26-1 strain) were suspended in PDB medium diluted 8-fold with sterilized water, and the spore suspension (no spreader added, 1 × per mL) 10 ⁵ spores) were prepared, and the obtained spore suspension was spray-inoculated on the whole plant body with a hand sprayer and managed in a 20 ° C. humid chamber until the time of investigation.
Four days after inoculation, the degree of disease in the cotyledons was indexed according to the following criteria, and the disease severity and control value were calculated.
Survey criteria: 0: No disease
1: Less than 5% lesion area
2: Disease area 5% or more and less than 25%
3: Disease area 25% or more and less than 50%
4: More than 50% lesion area
Disease severity = Σ (number of diseased leaves by degree × index) × 100 / (number of leaves studied × 4)
Control value = 100− (degree of disease in treated area / degree of disease in untreated area) × 100

Table 1 shows the control value of sclareol against cucumber gray mold. In addition, it shows that the control effect is so high that the numerical value of control value is high. That is, a control value of 0 indicates that the disease was not able to be controlled at all, and a control value of 100 indicates that the disease was completely controlled. Sclareol showed moderate but not complete control effects.

Example 7
<Control effect on rice seed infectious diseases>
In order to examine the control effect of sclareol against diseases other than bacterial wilt, the following experiment was conducted.
An appropriate amount of sclareol was added to methanol and stirred until uniform, thereby obtaining a drug having a sclareol concentration of 100 mM and diluted with water to a concentration of 100, 200, or 400 μM.
Next, the rice seedling bacterial disease infected rice cake “Koshihikari”, the rice seedling bacterial disease infected rice cake “Koshihikari”, and the rice blast seedling disease infected rice cake “short silver shaved” are put in a plastic pot, and twice the volume of water. Was added, and the sputum was completely immersed and cultured at 15 ° C. for 5 days. The water in the pot was discarded, and the diluted sclareol equal in volume ratio or water alone was newly injected as a control, transferred to 30 ° C. to promote germination, and cultured for 24 hours. Next, the straw was taken out from the pot, seeded on Ube soil, and subsequently cultured at 30 ° C. After the cultivation, the following investigations (1) to (3) were conducted on the seedlings with leaves.
(1) Rice Seedling Bacterial Disease Regarding rice seedling blight disease, all seedlings in each ward are investigated according to the following disease symptom index (onset index), and the disease severity and diseased seedling rate are obtained. Calculated.
(Symptom index)
0: Healthy
1: Third leaf whitening seedling
2: Second leaf whitening seedling
3: First leaf whitening seedling
4: Sprouting dead seedlings Disease incidence = Σ (number of diseased leaves by degree × index) × 100 / (number of leaves investigated × 4)
Control value = 100− (degree of disease in treated area / degree of disease in untreated area) × 100

(2) Rice Bacterial Blight Disease Regarding rice blight bacterial disease, all seedlings in each ward were investigated according to the following symptom index (morbidity index) to determine the disease severity and disease seedling rate, and the control value was calculated from the disease severity. .
(Symptom index)
0: Healthy
1: Whitening of the second leaf, strong hatching
2: Whitening of the second leaf, poor extraction of the second leaf
3: Withering or just before withering Disease severity = Σ (number of diseased leaves by index x index) x 100 / (number of leaves surveyed x 3)
Control value = 100− (degree of disease in treated area / degree of disease in untreated area) × 100

(3) Bone Seedling Disease With regard to rice shoot seedling disease, the number of healthy seedlings or the number of seedlings with illness seedling disease was investigated for all seedlings in each ward, and the control value was calculated from the rate of seedlings with illness seedling disease.

  Table 1 shows the control value of sclareol against rice seedling blight disease, rice blast bacterial disease, and rice seedling disease. In addition, it shows that the control effect is so high that the numerical value of control value is high. That is, a control value of 0 indicates that the disease was not able to be controlled at all, and a control value of 100 indicates that the disease was completely controlled. Sclareol showed a high degree of control effect against the above three diseases.

  In order to confirm the inhibitory effect of (11E, 13E) -labda-11,13-diene-8α, 15-diol on plant diseases, the following experiments of Examples 8 and 9 were conducted.

Example 8
(11E, 13E) -Rabda-11,13-diene-8α, 15-diol was purified from tobacco. The purification method was based on the method described in non-patent literature (The Plant Cell, Volume 15, Page: 863-873 DOI: 10.1105 / tpc.010231).
By adding an appropriate amount of (11E, 13E) -labda-11,13-diene-8α, 15-diol to methanol and stirring until homogeneous, (11E, 13E) -labda-11,13-diene A drug having a concentration of -8α, 15-diol of 100 mM was obtained.
Next, for the tobacco (variety name: Samsung NN) previously cultivated in the soil for about one month, the drug obtained as described above in the nutrient solution is (11E, 13E) -Rabda-11,13-diene-8α , 15-diol was added to a concentration of 100 μM, and hydroponically cultivated for 2 days. Thereafter, the roots of tobacco plants were inoculated with 8225 strains of blight fungus equivalent to the formation of 10 ⁸ colonies per mL. One week after inoculation, the stem was collected and ground in an appropriate amount of sterile distilled water using a mortar, and then the milled solution was diluted with an appropriate amount of sterile distilled water. Spread the diluted solution on CPG medium (1% bactopeptone, 0.05% glucose, 0.001% casamino acid, 0.9% agar) containing 50 ppm tetrazolium chloride, and culture at 30 ° C. for 2 to 3 days. Colonies with a pink center were counted. In addition, as a control, the same treatment was performed by inoculating the tobacco treated in the same manner with a nutrient solution to which 0.1% of methanol was added but no chemical was added.
FIG. 7 shows the degree of growth of the bacterial wilt 7 days after the inoculation of the bacterial wilt. In tobacco treated with (11E, 13E) -Rabda-11,13-diene-8α, 15-diol, it was found that the growth of blight fungus was suppressed.

Example 9
<Antimicrobial activity against bacterial wilt>
The following experiment was conducted to confirm the presence or absence of antibacterial activity of (11E, 13E) -Rabda-11,13-diene-8α, 15-diol against bacterial wilt.
The agar medium containing 100 μM (11E, 13E) -Rabda-11,13-diene-8α, 15-diol or 0.1% methanol as a control was inoculated with the bacterial strain 8225 and cultured.
FIG. 8 shows a photograph on the first day after inoculation. There was no clear difference between the two, and (11E, 13E) -Rabda-11,13-diene-8α, 15-diol itself did not exhibit antibacterial activity against bacterial wilt.

  The present invention is for cultivating healthy crops by controlling various plant diseases such as bacterial wilt, blight, gray mold, rice seedling bacterial disease, rice blast bacterial disease, rice blast blight, etc. It can be expected to be used as an effective material for control agents as agricultural materials.

Claims (7)

  A plant disease control agent comprising a terpenoid-related compound as an active ingredient.   The plant disease control agent according to claim 1, wherein the terpenoid-related compound is sclareol.   The plant disease control agent according to claim 1 or 2, wherein the plant disease is bacterial wilt disease, bacterial wilt disease, gray mold disease, rice seedling bacterial disease, rice blast bacterial disease, or rice blast disease.   A plant disease control method characterized by causing a target plant to absorb a terpenoid-related compound.   The plant disease control method according to claim 4, wherein the terpenoid-related compound is sclareol.   The plant disease control method according to claim 4 or 5, wherein the plant disease is bacterial wilt disease, blight disease, gray mold disease, rice seedling bacterial disease, rice blast bacterial disease, or rice blast disease.   The plant disease control method according to any one of claims 4 to 6, wherein the target plant is a solanaceous family, a cruciferous family, a grass family, or a cucurbitaceae.