WO2004064521A1

WO2004064521A1 - Plant disease controlling agent and method of controlling plant disease using the same

Info

Publication number: WO2004064521A1
Application number: PCT/JP2004/000217
Authority: WO
Inventors: Jinichiro Koga; Kenji Umemura; Shigeki Tanino; Hidetoshi Kubota
Original assignee: Meiji Seika Kaisha Ltd.
Priority date: 2003-01-17
Filing date: 2004-01-15
Publication date: 2004-08-05
Also published as: TW200503624A; JP2006219372A

Abstract

By treating a cultivated plant with a plant disease controlling agent containing bile acids or derivatives thereof, resistance to diseases is induced and thus infection with pathogenic microorganisms is prevented.

Description

Description Plant disease controlling agent and plant disease controlling method using the agent

The present invention relates to a plant disease controlling agent containing bile acids, having a low environmental load, and safe for users and consumers, and a method for controlling plant diseases using the controlling agent. Background art

Methods for controlling disease on agricultural crops include controlling pesticides by directly acting on phytopathogenic bacteria such as fungicides, and controlling crop diseases by increasing the disease resistance of the plants themselves (resistance-inducing pesticides). ) Is used.

Many pesticides that act directly on plant pathogens, such as fungicides, show a bactericidal effect on pathogenic bacteria, and in most cases, their use leads to the emergence of drug-resistant mutants. On the other hand, resistance-inducing pesticides do not act directly on pathogens, but control plant disease by inducing plant resistance.Therefore, there have been cases where resistant mutants of these drugs have appeared. Not been. Furthermore, resistance-inducing pesticides are considered to have a relatively low impact on the environment, including non-plant organisms, due to their low fungicidal activity on organisms.

At present, in agricultural production, it is required to establish sustainable agricultural production technology, and the development of environmentally friendly agricultural materials has become an important issue in order to achieve that goal. In addition, demand for organic agricultural products cultivated by taking advantage of the natural circulation function of agriculture has been increasing due to the recent increase in consumer-oriented food safety. Regarding the labeling of organic agricultural products, use of natural useful mineral materials, plants, animals and natural substances extracted, extracted or prepared from them for the purpose of pesticides, such as pest control, according to the guidelines provided by the Ministry of Agriculture, Forestry and Fisheries Indicates that the use of antibiotics is not allowed only when the pesticide is registered under the Pesticide Control Law. Therefore, if it has the aforementioned resistance-induced disease control effect of preventive control and can supply agricultural materials derived from natural products, the agricultural producer who is the user In addition, it is a pesticide that is safe for consumers and can reduce the environmental burden.

Until now, pesticides that are allowed to label organic agricultural products for the purpose of inducing plant disease resistance are limited to probenazole and benzobenzolaru S-methyl, which are registered as rice blast control agents. These pesticides for the purpose of inducing disease resistance do not act directly on plant pathogens, but show various crop disease control effects by inducing plant resistance. No emergence of resistant mutants has been reported. However, they are all chemically synthesized pesticides, and it is considered preferable to avoid excessive dependence on the environment and other factors. Examples of natural product-derived disease resistance inducers include polysaccharide degradation products (see, for example, JP-A-5-331016) and celeb mouthsides (see, for example, Japanese Patent No. 2846610). Publications, International Publication No. 98/47364, pamphlet and Koga J. et al., J. Biol. Chem., 1998, 48, 27, p. 31985-31991.), Jasmonic acid (for example, JP-A-11-29412 and Nojiri H. et al., Plant Physiol., 1996, 110, p.387-392.), Chitin oligosaccharides (for example, Yamada A. et al.) , Biosci. Biotech. Bio (see: 1 ^ 111., 1993, 57, 3, 0.405-409), / 3-1,3 and / 3-1,6-glucanoligosaccharides (eg, Sharp JK et al.). al., J. Biol. Chem., 1984, 259, p.11312-11320, Sharp JK et al., J. Biol. Chem., 1984, 259, p.11321-11336 and Yamaguchi T. et al. , Plant Cell, 2000, 12, p.817-826.) These substances are called elicitors. Phytoalexins, which have antibacterial activity against pathogenic bacteria, chitinase that dissolves the cell walls of pathogenic bacteria, PR proteins (pathogenesis-related proteins) such as β-1,3-glucanase, or hypersensitive cell death (Hypersensitive cell death) is known to establish disease resistance by inducing plants (eg, Yamada A. et al., Biosci. Biotech. Biochem., 1993, 57, 3, p. 405). — See 409 and Keen NT, Plant Mol. Biol., 1992, 19, p.109—122.)

In addition, since these elicitors are contained only in small amounts in filamentous fungi, bacteria, and plants, their practical use as disease resistance inducers requires purification from a large amount of filamentous fungi, bacteria, and plants. Hampered by the cost difficulty of having to extract Was. Therefore, in order to provide a disease resistance inducer suitable for practical use, it was necessary to prepare a disease resistance inducer that can be easily prepared in large quantities from nature and that has a strong disease resistance induction activity.

In general, most of the above-mentioned naturally occurring elicitors are derived from filamentous fungi, bacteria, and plants, and there are no reports that they are derived from animals (eg, Cheong J.-J. ei al.). , Plant Cell, 1991, 3, p.127-136.)).

By the way, bile acids are known to have various effects on animals, but very little is known about the effects on microorganisms and plants. However, there are some findings that the growth of fungi and filamentous fungi is suppressed by the addition of high concentrations of bile acids, especially deoxycholic acid. For example, it is known that cholic acid, chenodeoxycholic acid, deoxycholic acid, and lithocholic acid at a concentration of 0.4% or more have a fungal effect on Candida yeast (for example, Refer to the official gazette of Japanese Patent Application Publication No. 4_7 8 6 16).

It is also known that 0.03-0.1% of deoxycholic acid has a growth inhibitory effect on plant pathogenic fungi (Ampuero E. et al., Adv. Front. Plant Sci., 1966, 16, p.85-90.)).

On the other hand, before 1930, it has been known that the application of latex to plants prevents the transmission of phytopathogenic bacteria by forming a film on the plant surface. Therefore, it has been shown that when bile acid is added to milky lotion and sprayed on plants, the bile acid achieves uniform coating with the milky lotion and makes the film last longer, thereby enhancing the sustainability of the infection control effect. (For example, see German Patent No. 5 336 11). However, although there is a description that bile acid plays an auxiliary role in improving the infection control effect of emulsion, there is no description that bile acid alone has a plant infection control effect.

Thus, although there is some knowledge about the action of bile acids, there is no knowledge to date that bile acids alone act on plants to control plant diseases. Furthermore, there is no finding that bile acids induce plant disease resistance. Disclosure of the invention The present inventors have searched for a plant disease resistance-inducing substance for a wide range of natural products, and surprisingly, bile acids, which are substances originally derived from vertebrates, induce disease resistance in rice. I discovered that. That is, it has been discovered that treatment with the substance induces phytoalexin (phytosan), an antibacterial substance, a lytic enzyme; 6-1,3-dalcanase, to rice.

The present inventors have also found that by treating plants such as rice, tomato, and lettuce with bile acids before the onset of the disease, a control effect on the disease can be obtained. Furthermore, bile acids were found to have a high control effect at surprisingly low concentrations of 1-20 O mg ZL.

The present invention has been made based on the above findings, and provides a plant disease controlling agent comprising one or more selected from bile acids and derivatives thereof.

The present invention also provides the bile acids, wherein the bile acids are cholic acid, arocholic acid, chenodeoxycholic acid, lithocholic acid, deoxycholic acid, hyocholic acid, muricholic acid, hydoxycholic acid, ursodeoxycholic acid, taurocholic acid, glycochol. Acid, tauroglycocholic acid, taurochenedoxycholic acid, taurodeoxycholic acid, taurolithocholic acid, glycochenodeoxycholic acid, glycodoxycholic acid, glycolicocholic acid, oxolitocolic acid, and the like The above-mentioned plant disease controlling agent comprising one or more selected from salts of the above.

The present invention also provides the plant disease controlling agent, wherein the concentration of the bile acid or a derivative thereof is 0.1 to 100 mg / L as applied to a plant.

The present invention also provides use of one or more selected from bile acids and derivatives thereof in the production of a plant disease controlling agent.

The present invention also provides a method for controlling plant diseases, comprising a step of treating a cultivated plant with the plant disease controlling agent.

The present invention further provides a method for controlling plant diseases, which comprises inducing disease resistance in the plant by treating the cultivated plant with the plant disease controlling agent.

To date, some bile acids have been found to contain fungi and filaments at very high concentrations,> 4 g ZL. It is known that it has antibacterial activity against fungi. Indeed, also in the present invention, an extremely high bile acid concentration of 5 g / L or more showed an effect of suppressing the growth of pathogenic bacteria. However, as described in the present invention, by treating rice with bile acids at a concentration 25 to 500 times lower than the concentration at which bile acids exhibit antibacterial activity against pathogenic bacteria, before the onset of the disease, It is surprising that there is no finding that it has a controlling effect on pathogens. Furthermore, this finding and the fact that no control effect was found even when bile acids were treated with rice immediately before infection with pathogenic bacteria were found by the present invention, indicating that the control effect of bile acids was not significant. It is not due to induction of disease resistance in plants, but to plants.

Many pesticides, such as fungicides, that act directly on plant pathogens show a bactericidal effect on the pathogenic bacteria, and drug resistant mutants emerge after continuous use. On the other hand, resistance-induced pesticides are known to be resistant to drug-resistant mutants and can be used for long periods of time. Thus, preventing bile acids from infecting pathogenic bacteria by inducing disease resistance rather than antibacterial activity means that resistant mutants are unlikely to appear and can be used for a long period of time. It is extremely useful in industry.

In addition, as described above, when bile acids are added to milky lotion and sprayed on plants, the bile acids realize uniform coating with the emulsion, and the film lasts longer, thereby enhancing the sustainability of the infection control effect. However, the discovery that bile acids themselves have a plant disease controlling activity without adding an emulsion as in the present invention is completely new. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, bile acids refer to bile acids, bile salts, conjugated bile acids, and conjugated bile salts, and refer to all bile acids contained in vertebrates such as mammals, birds, and fish. Here, a conjugated bile acid refers to one in which taurine, glycine, or the like is conjugated to the carboxyl group of the bile acid. Specific examples of these bile acids include, for example, cholic acid, arocholic acid, chenodeoxycholic acid, lithocholic acid, deoxycholic acid, hoocholic acid, muricholic acid, hydroxycholic acid, and ursodeoxycholic acid. , Taurocholic acid, glycocholic acid, tauroglycocholic acid, taurokenodeoxycholic acid, taurodeoxycolic acid, taurolithocholic acid, glycochenodeoxycholic acid, glycodoxycholic acid, glycolitolcholic acid Oxolithocholic acid or a salt thereof.

Bile acids are mainly produced in the liver of higher animals, are stored in the gall bladder, are excreted in the intestine, and are known to help the intestinal absorption by emulsifying fat and activating lipase. Have been. In humans, bile acids are primary bile acids synthesized directly in the liver, such as cholic acid and chenodeoxycholic acid, which are dehydrated by intestinal bacteria and are exposed to secondary acids such as lithocholic acid and deoxycholic acid. It becomes the next bile acid. In vivo, carboxyl groups of these bile acids are conjugated to lindaridicin. Conjugated bile acids are the major components. These bile acids are synthesized in large amounts in the body and are stored like bile, so they are extremely safe for humans, and at the same time, can be easily prepared as natural materials from livestock animals, etc. It is possible.

In the present invention, the bile acids are preferably prepared from natural materials, but can be used even if they are chemically synthesized.

In the present invention, the derivative of bile acids refers to those synthesized artificially or in the natural world using bile acids as starting materials, such as esterified products, hydroxides, and dehydrated oxides of bile acids. A plant disease resistance inducing activity that is equal to or less than the starting material. At this time, the plant disease resistance-inducing activity can be measured from the phytoalexin-inducing ability of rice according to the method described in Example 1.

In the present invention, the bile acids and their derivatives can be used alone or in a mixture of two or more.

In the present invention, the dosage form of the plant disease control agent, its use form and application method are not particularly limited, but it is preferably liquid when applied. The plant disease controlling agent of the present invention may be any one which can dissolve or dilute in a solvent at the time of use, so that bile acids or their derivatives can be formed into a suitable concentration and in a form suitable for application. The content of bile acids or their derivatives is not particularly limited.

The preferred application concentration of the pesticide is bile acids or plant bile acids at the time of application. Is 0.1 to 100 mg / L, more preferably 1 to 100 mg ZL, particularly preferably:! ~ 200 mg / L. However, it is preferable to adjust the application concentration to an appropriate concentration according to the type of plant, the growth stage, and the application method.

The plant disease controlling agent of the present invention can be prepared by mixing bile acids or their derivatives with an appropriate additive, and preparing a liquid, powder, granule, emulsion, wettable powder, oil, aerosol, flowable, etc. It may be used for. Further, if desired, the pH can be adjusted by adding a buffer or the like, and a surfactant or the like can be added to improve the permeability and spreadability to plants.

The method for controlling plant diseases of the present invention includes a step of treating a cultivated plant with the plant disease controlling agent. In a preferred aspect of the present invention, disease resistance is induced in the plant by treating the cultivated plant with the plant disease controlling agent. Examples of the method of treating a cultivated plant with the plant disease controlling agent of the present invention include spraying or applying to a plant, immersing in a root, and mixing with soil.

Further, since the method for controlling plant diseases of the present invention is aimed at preventing disease, it is preferable to use the method before the time when the disease occurs. However, the above object does not mean that the plant disease controlling agent of the present invention does not have an action of promoting disease healing after the disease has occurred.

The crops which can be targeted by the plant disease controlling agent of the present invention include all cultivated plants, for example, grasses (rice, corn, wheat, corn, junpa, etc.), solanaceous plants (tomato, eggplant, potato, etc.) ), Periphytes (e.g., cucumber, melon, kabochiya), legumes (e.g., endu, soybean, pingen bean, alfalfa, laccasei, faba bean), cruciferous plants (e.g. radish, Chinese cabbage, beetle, etc.) Family plants (strawberry, apple, pear, etc.), croaker (crop, etc.), aoaceae (crop, etc.), apiaceae (carrot, parsley, celery, etc.), asteraceae (burdock, sunflower, chrysanthemum, lettuce, etc.) , Grape family (such as grapes) and so on. Among these plants, preferable ones include grasses, solanaceous plants, and asteraceous plants, and particularly preferable ones include rice, tomato, and lettuce. Also, the general disease resistance response of plants is non-specific to pathogenic bacteria, The target diseases of the above crops include all plant diseases caused by fungi, bacteria and viruses. For example, rice blast fungus (Magnaporthe grisea), rice sesame leaf blight fungus (Cochl iobolus miyabeanus), shakaimo powdery power, disease fungus (Spongospora subterranea), jakai fungus (Phytophthora infestans), and diazbe ica sporamana Sp. Hordei), Kom Sentonko; (Eryshiphe graminis f. Sp.tritici), Wheat red mold (Gibberelia zeae), Endo brown spot fungus (Mycosphaerel la pi nodes), wheat (Sclerotinia borealis), wheat rust (Puccinia recondita), corn smut (Ustilago way d is), oo ォ ^ ¾ ¾¾ (Ceratobasi iuE gramineuE), potato black asa, rhizoctoni a solani, rice sheath blight (Rhizoctonia solani), potato summer blight fungus (Alte rnaria solani), soybean spot rot fungus Cercospora kikuchii ) Sp.batatas), Fusarium ox ysporum f. Sp. Me Ion is, Fusarium oxysporum f. Sp. Lact ucae, and Tomato Tribium Sp. Lycopersici), Fusarium oxysporum f. Sp. Spinaciae, Vert ici 11 iua dahliae, Plasmodiophora brassicae ae), Pythium debaryanum, strawberry gray mold, Botrytys cinerea, Colleiotrichwn phomoides, Pseudomonas syringae pv. syringae)

(Erwinia subsp. Atrosept ica), Rice leaf blight fungus (Xanthomonas c estr is p v. Oryzae), potato scab fungus (Streptomyces scabies), wheat atrophy (Soil— borne wheat mosaic virus), soybean Diseases caused by soybean mosaic virus, Alfalfa mosaic virus, potato leafroll virus, etc.

Hereinafter, the present invention will be described more specifically with reference to Examples. It is not limited to the embodiment. Example 1: Induction of phytoalexin by bile acids in rice

Sprout seeds of rice (variety: Akitakomachi) were sown in paddy rice cultivation and cultivated in a glass cultivation case installed in a climate chamber. The climate chamber was set for a cycle consisting of 12 hours at 22 ° C, 30, OOOLux and 12 hours at 18 ° C / 0Lux. When the 5-leaf leaf was 60 to 70% developed, 20 samples (2 L per spot) were placed on 10 surfaces of the 4-leaf leaf. The sample (bile acids) was dissolved in a 0.1% Tween 20, 20 mM potassium phosphate buffer (pH 6.0) solution, but the insoluble bile acids were dissolved by adding an appropriate amount of ethanol. I let it. After applying the sample, rice was cultivated for 2 days in a climate chamber, cut six leaf portions applying the specimen, acetate Echiru solution 5 mL and 0. 2M N a C_〇 ₃ solution (ρΗ Ι Ο. 8 Phytoalexin contained in the leaves was extracted by adding 5 mL and mixing. After the extraction, the ethyl acetate layer was evaporated to dryness, 1.6 mL of ethanol was added to dissolve, and 2.4 mL of 0.02M HC1 was further added and mixed. 0.2 mL of the supernatant obtained by centrifuging this sample was subjected to HPLC analysis to determine phytosan, a rice phytoalexin. The quantification of phytocasans was determined according to the method of Koga et al. (Koga J. et al., Tetrahedron, 1995, 51, .7907-7918; Koga J. et al., Phytochemistry, 1997, 44, 249-253). Performed by analysis. That is, a TSKgel®DS-120T column (4.6 mm d. X 30 cm; manufactured by Tosoh Corporation) was used under the conditions of 45% acetonitrile, a flow rate of 1.2 mLZmin, and a column temperature of 50 ° C. The sample was poured, and the peaks of phytokasan A and phytokasan B were detected at UV 280 nm. The preparations of Huaitosan A and B were isolated and purified from rice according to the method of Koga et al., And the amount of Huaitokasan A and Huaitokasan B induced per rice leaf was repeated 5 times. It was calculated as the average value of the reversion test.

The results are shown in Table 1. It has been confirmed that phytoalexins such as phytosan, etc. have strong antibacterial activity against disease fungi on rice such as blast fungus and sheath blight fungus (Koga J. et al., Tetrahedron, 1995, 51, .7907-7918), rice It is known to be one of the factors of disease resistance. From the results in Table 1, it was found that bile acids and their derivatives, cholic acid methyl ester, have an activity of inducing rice phytoalexin. Here, 0.1% Tween 20 as a spreading agent and 20 mM potassium phosphate buffer (pH 6.0) as a pH adjusting agent were added to the solution containing bile acids. Even without adding both, bile acids alone were able to induce phytocasan.

table 1

Type of bile acids Bile acid concentration Huytokasan induced amount Z leaf)

(g / mL; phytocasan A phytosan B) 0 0. 04 0.02 cholic acid 25 0.12 0.06 cholic acid 50 0.19 0.09 cholic acid 100 0.28 0.1 1 Deoxycholic acid 400 0.28 0.10 Chenodeoxycholic acid 200 0.29 0.10 Cholic acid methyl ester 400 0.22 0.10 Hydoxycholic acid 800 0.12 0.05 Taurocholic acid , 200 0.32 0.20 Glycocholate 200 0.16 0.08 Tauroglycocholate 200 0.2 1 0.08 Example 2: Induction of 3_1,3-dalcanase by bile acids in rice

Sprout seeds of rice (variety: Akitakomachi) were sown on paddy rice cultivation soil and cultivated in a glass cultivation case installed in a climate chamber. The climate chamber was set to cycle at 1 day at 22 ° C / 25, 12 hours at OOOLux and 12 hours at 18 / 0Lux. When the true leaf at the age of 5 leaves expanded from 60 to 70%, a 20 L sample (2 L per location) was placed at 10 locations on the surface of the true leaf at the age of 4 leaves. The cholate supplemented group was prepared by dissolving sodium cholate at a concentration of 20 Omg / L in a 0.1% Tween 20, 20 mM potassium phosphate buffer (pH 6.0) solution. Only a 0.1% Tween 20, 20 mM potassium phosphate buffer (ρH 6.0) solution was used. After applying the sample, the rice was cultivated for 2 days in a climate chamber, and 6 leaves were cut off from the area where the sample was applied. 0.3% of pre-chilled leaves The solution was placed in 5 mL of Triton X-100, 5 OmM acetate buffer (pH 5.0) solution, homogenized with a polytron, and the centrifuged supernatant was subjected to enzyme activity measurement. ) The 3-1 and 3-dalcanase activities were performed according to the method of Inui et al. (Inui H. et al., Biosci. Biotech. Biochem., 1997, 61, 6, p. 975-978). That is, 1% of curdlan (curdlan), put an enzyme solution 0. 2 mL to 5 0 mM N a ₂ HP_〇 ₄ _ Kuen acid buffer one (PH 5. 0), as a solution of total volume 2 mL, 3 7 X: Shaking reaction was performed for 60 minutes. The amount of reducing sugars generated in the reaction solution was measured by the DNS method (Mi Her GL et al., Anal. Chem., 1959, 31, 426-428) and determined as β-1,3-dulcanase activity. . The activity unit is defined as 1 U, the amount of enzyme that produces 1 / mo 1 of glucose-reducing sugar per minute, and is induced per leaf; 3-1, 3-dalcanase activity is 5 units. It was determined as the average of repeated tests.

Table 2 shows the results. J3_l, 3-Dulcanase, a kind of PR protein (pathogenesis-related proteins), is induced as a bacteriolytic enzyme and is known to be one of the disease resistance of plants. These results clearly show that cholic acid, one of the bile acids, has an activity of inducing rice] 3-1,3-glucanase. Table 2

Example 3: Effect of Bile Acid Spraying on Infection Control of Rice Blast Fungus

Sprout seeds of rice (variety: Akitakomachi) were sown in paddy rice cultivation and cultivated in a glass cultivation case installed in a climate chamber. The climate chamber was set to cycle at 1 day at 22 ° C / 25, 12 hours at OOOLux, and 12 hours at 18Τ0 LuX. When the true leaf 3 leaf age is 100% expanded, the setting of the climate chamber is 12 hours at 22 ° C / 20, OOOLux, and 12 hours at 18 ° C / 0Lux Changed to cycle conditions. When the true leaf 5 leaf age is expanded to 10 to 20%, 0.01 % Tween 20 and 4 mM potassium phosphate buffer (pH 6.2) solutions of various concentrations of cholate Na, chenodeoxycholic acid Na and taurocholic acid Na dissolved in rice leaves Sprayed. For the control, only a solution of 0.01% Tween 20 and 4 mM potassium phosphate buffer (pH 6.2) was sprayed. After cultivation again in the climate chamber for 2 days, infection treatment was performed by spraying and inoculating a conidia suspension of rice blast fungus (scientific name: Magnaporthe gris ea race 07 strain). After inoculation, the blast fungus was infected by leaving for 36 hours in a dark place and in a humidified condition. After that, the plants were transferred to a climate chamber and cultivated. After 6 days from the inoculation, the control value was calculated by measuring the number of diseased lesions that had developed on the fourth true leaf of each plot. 200 rice plants in each section were infected, and the control value was calculated by the following formula. Control value = (1 average number of lesions per leaf in each section Z average number of lesions per leaf in control section) X 100 The results are shown in Table 3. From Table 3, it was found that spraying bile acids at a very low concentration of 1 to 20 Omg_L was effective in controlling rice blast fungus. Here, 0.01% Tween 20 was added as a spreading agent and 4 mM potassium phosphate buffer (pH 6.2) was added as a pH adjusting agent to a solution containing bile acids. However, even without the addition of both, bile acids alone were effective in controlling rice blast fungus.

Table 3

Example 4: Bile acid suppresses germination of rice blast fungus.

Conidia of rice blast fungus (scientific name: Magnaporthe grisea race 07 strain) were converted to 0.05% Tween 20%, 4 mM potassium phosphate buffer (ρH7), and various concentrations of cholic acid. The mixture was suspended and mixed in a solution of Na and incubated at 28 ° C. for 16 hours. Then, the number of spores that had germinated and the number of spores that had not germinated were counted, and the spore germination rate of the blast fungus was determined. The spore germination rate of the blast fungus was calculated by the following formula, and calculated as an average value of five repeated tests. Spore germination rate of blast fungus = (number of germinated spores Z total number of spores) XI 0 0 The results are shown in Table 4. As is clear from Table 4, a high concentration of cholic acid of 500 mg ZL or more exhibited an effect of inhibiting the germination of the blast fungus, while a choline having a concentration of 200 mg / L or less produced the blast fungus. No germination inhibitory effect was observed. From this, it was found that the effect of spraying bile acids at a very low concentration of 1 to 20 OmgZL on the control of rice blast infection was not due to the antibacterial activity of bile acids. Table 4

Example 5: Effect of Bile Acid Spraying Immediately before Infection with Rice Blast Infection Control Effect

Sprout seeds of rice (variety: Akitakomachi) were sown in paddy rice cultivation and cultivated in a glass cultivation case installed in a climate chamber. The climate chamber was set for a cycle consisting of 22 hours at 22 ° CZ25, 12 hours at OOOLux, and 12 hours at 18 ° C / 0 Lux. When the true leaf 3 leaf age is expanded to 100%, the setting of the climate chamber is set at 22 ° C / 20, OOOh lux for 12 hours, and 18 ^ / 0 lux for 12 hours. Changed to conditions. When the true leaf 5 leaf age develops 40-50%, various concentrations of cholic acid N dissolved in a solution of 0.01% D-ween 20 and 4 mM potassium phosphate buffer (pH 6.2) a was sprayed on the whole rice leaf. One hour later, infection treatment was performed by spraying a conidia suspension of a rice blast fungus (scientific name: Magnaporthe grisea race 07 strain). After the spray inoculation, the blast fungus was infected by leaving for 36 hours in a dark place and in a humidified condition. After that, the plants are transferred to the artificial climate room and cultivated.After 6 days from the inoculation, the number of diseased lesions on the fourth true leaf of each section is measured. And the control value was calculated. 200 rice plants were infected in each zone, and the control value was calculated by the following formula. Control value = (1 average number of lesions per leaf in each section Z average number of lesions per leaf in section without addition of cholic acid) X 100 The results are shown in Table 5. As is clear from the results, it was found that under the above conditions, even if cholic acid was sprayed immediately before infection with the rice blast fungus, there was no infection control effect in the concentration range of 1 to 200 OmgZL. On the other hand, as shown in Example 3, spraying bile acids two days before infection with the blast fungus, even at a concentration as low as 1 to 200 mg / L, has an effect of controlling infection. It was found that bile acids, not the activity, induced the resistance to the plant by inducing resistance to the plant. Table 5

Example 6: Effect of Bile Acid Root Treatment on Infection Control of Rice Blast Fungus

Sprout seeds of rice (variety: Akitakomachi) were sown on paddy rice cultivation soil and cultivated in a glass cultivation case installed in a climate chamber. Artificial weather room is 22 ° C / 2 a day 5. The cycle condition was set to consist of 12 hours with OOOLux and 12 hours with 180Lux. When the true leaf 3 leaf age is expanded to 100%, the setting of the climate chamber is changed to the condition of 222 hours, 12 hours at OOOLux, and 12 hours at 18 ° CZ 0Lux. did. When the true leaf at the age of 5 leaves expanded to 10% to 20%, the rice plants were immersed together with the pots in solutions containing various concentrations of cholate Na to allow bile acids to be absorbed from the roots.

After cultivation again in the artificial climate room for 2 days, infection treatment was carried out by spraying and inoculating a conidia spore suspension of the rice blast fungus (scientific name: MagnaporiAe grisea race 007). After the spray inoculation, the blast fungus was infected by leaving for 36 hours in the dark and in a humidified condition. After that, the plants were transferred to the artificial weather chamber and cultivated, and the control value was calculated by measuring the number of diseased lesions on the fourth true leaf of each section 6 days after inoculation. 200 rice plants were infected in each zone, and the control value was calculated by the following formula. Control value = (1—average number of lesions per leaf in each section / average number of lesions per leaf in section without cholate) X 100 The results are shown in Table 6. As is clear from Table 6, the bile acids at a very low concentration of 5 to 5 OmgZL have an effect of controlling rice blast infection not only by spraying but also by immersion. Table 6

Example 7: Control effect of bile acid on lettuce root rot

Seedlings of lettuce (cultivar: Patriot) in which three true leaves have been developed are immersed in a solution containing various concentrations (10, 5 Omg / L) of cholic acid Na for 24 hours to remove bile acids from the roots. After absorption, lettuce root rot fungus (Fusarium oxysporum f. Sp. Laciucae race SB 1-1) contaminated soil (dilution plate method to determine bacterial density was 2 X 10 ³ C FUZg soil) ) Was transplanted for infection treatment.

Twenty-eight days after transplantation, an onset of external symptoms was investigated. The criteria for the severity of the external symptom are 0 for healthy leaves, 1 for cases where the lower 1-2 leaves have a symptom, 2 for cases where all outer leaves have a symptom, and about half of the leaves 3 were evaluated for the presence of a symptom, 4 for those with a symptom on most of the leaves and deciduous leaves, and 5 for those in which the plants died. The control value was calculated by the following formula. Control value = (average disease incidence in control plots-average disease incidence in test plots) / (average disease incidence in control plots) X 100 The results are shown in Table 7. As is evident from Table 7, it was found that immersion treatment of bile acids at a very low concentration of 10 to 5 Omg / L was effective in controlling lettuce root rot infection.

Example 8: Effect of controlling bile acid on tomato wilt

Tomato seedlings (cultivar: Ponterosa) with two true leaves developed are immersed in a solution containing various concentrations (10, 5 Omg / L) of colic acid Na for 72 hours to remove bile acids from the roots. After being absorbed from the soil, the bacterial infection of tomato wilt (Fi / sarii / ffl oxysporuffl ί · sp. Lycopersic i race J_l) is transferred to a contaminated soil of 5 × 10 ⁴ C FUZg soil for infection treatment. went.

37 days after transplantation, the control effect was examined by investigating the onset of external symptoms. The criteria for the severity of external symptom are 0 for healthy leaves, 1 when there are symptom in lower 1-2 leaves, and half The evaluation was given by giving an index of 2 for those with a symptom on the leaf, 3 for those with a symptom on most of the leaves and deciduous leaves, and 4 for the dead plant. The control value was calculated by the following formula. Control value == (average disease incidence in control plot-average disease incidence in test plot) / (average disease incidence in control plot) X 100 The results are shown in Table 8. As is evident from Table 8, it was found that the immersion treatment of bile acids at a very low concentration of 10 to 5 Omg / L was effective in controlling the infection of tomato wilt fungi.

Industrial potential

The present invention relates to a plant disease controlling agent comprising a bile acid or a derivative thereof, which has a low environmental load, and exhibits a high controlling effect against a disease of a cultivated plant by applying the controlling agent. Can be.

Claims

The scope of the claims

1. A plant disease controlling agent comprising one or more selected from bile acids or derivatives thereof.

2. The bile acids are cholic acid, valocholic acid, chenodeoxycholic acid, lithocholic acid, deoxycholic acid, hyocholic acid, muricholic acid, hydoxycholic acid, ursodeoxycholic acid, taurocholic acid, Glycocholate, Tauroglycocholic acid, Taurochenedoxycholic acid, Taurodeoxycholic acid, Taurolithocholic acid, Glycochenedoxycholic acid, Glycodoxycholic acid, Glycolycholic acid, Oxolitocholic acid, or a mixture thereof The plant disease controlling agent according to claim 1, comprising one or more selected from salts.

3. The concentration applied to the plant is 0, as the content of bile acids or their derivatives.

The plant disease control agent according to any one of claims 1 and 2, wherein the agent is 1 to 100 mg OgZL.

4. Use of one or more selected from bile acids and their derivatives in the manufacture of plant disease control agents.

5. A method for controlling plant diseases, comprising a step of treating a cultivated plant with the plant disease controlling agent according to any one of claims 1 to 3.

6. The method for controlling a plant disease according to claim 5, wherein a disease resistance is induced in the plant by treating a cultivated plant with the plant disease controlling agent.