JP7705531B2 - Plant activators - Google Patents

Description

The present invention relates to a plant activator.

Since ancient times, measures such as optimizing temperature and sunlight conditions and applying fertilizer have been taken to promote plant growth. However, these measures have limitations. For example, not only is it difficult to expect a certain level of growth promotion effect by increasing the amount of fertilizer used, but applying too much fertilizer can actually hinder plant growth and even result in soil contamination.

In addition to the above-mentioned measures, a method of activating plants using a plant activator that has plant growth regulating effects such as growth promotion, dormancy suppression, and stress suppression has been reported. For example, Patent Document 1 describes a plant activator that contains a ketol fatty acid with 4 to 24 carbon atoms as an active ingredient. Patent Document 2 reports a plant activator that contains fatty acid metabolites obtained by metabolizing fatty acids with 4 to 30 carbon atoms using Proteobacteria in an environment with a dissolved oxygen concentration of 0.1 to 8 mg/L.

JP 2001-131006 A International Publication No. WO 2018/47918

There is a demand for a plant activator that has a growth-promoting effect superior to that of the plant activator containing ketol fatty acid as an active ingredient described in Patent Document 1 and the plant activator described in Patent Document 2, and that has excellent uniformity and dispersibility when irrigated or sprayed.

The present invention aims to provide a plant activator that has low soil contamination and toxicity and has excellent plant growth promoting effects.

The present invention relates to a compound represented by the following formula (I) and/or (II):
HOOC-(R ¹ )-CH(OH)-CH(OH)-CH=CH-CH(OH)-R ² (I)
HOOC-(R ¹ )-CH(OH)-CH=CH-CH(OH)-CH(OH)-R ² (II)
During the ceremony,
R ¹ is a linear or branched hydrocarbon group having 4 to 12 carbon atoms, which may contain one or more double bonds and/or OH groups, and when it contains a double bond, the position of the double bond is not limited;
^R2 is a linear or branched hydrocarbon group having 2 to 8 carbon atoms, which may contain one or more double bonds and/or OH groups, and when it contains a double bond, the position of the double bond is not limited;
The present invention relates to a plant activator comprising as an active ingredient a hydroxylated fatty acid derivative or a salt or ester thereof having the following structural formula: wherein R ¹ is particularly preferably --(CH ₂ ) _n -- (wherein n is an integer of 4 to 12).

The plant activator is preferably a hydroxylated fatty acid derivative in which the hydrocarbon group of R ¹ has 6 to 8 carbon atoms and the hydrocarbon group of R ² has 4 to 6 carbon atoms.

The plant activator is preferably a hydroxylated fatty acid derivative in which R ¹ has a structure of -(CH ₂ ) _n - (n is an integer from 4 to 12) and R ² has a structure of C _n H _2n+1 - (n is an integer from 2 to 8).

The plant activator is preferably a hydroxylated fatty acid derivative in which R ¹ is an alkylene group having 7 carbon atoms (-(CH ₂ ) ₇ --) and R ² is an alkyl group having 5 carbon atoms (CH ₃ CH ₂ CH ₂ CH ₂ CH ₂ --).

Preferably, the plant activator is one in which the hydroxylated fatty acid derivative is hydroxyoctadecenoic acid.

Preferably, the plant activator is one in which the hydroxylated fatty acid derivative is 9,10,13-trihydroxy-11-octadecenoic acid.

Preferably, the plant activator is one in which the hydroxylated fatty acid derivative is 9,12,13-trihydroxy-10-octadecenoic acid.

Note that "octadecaenoic acid" is a conventional notation (for example, JP Patent Publication 3-14539, etc.), and the above-mentioned "9,10,13-trihydroxy-11-octadecenoic acid" is also written as "9,10,13-trihydroxyoctadec-11-enoic acid" or "9,10,13-trihydroxy-11-octadecenoic acid". Similarly, the above-mentioned "9,12,13-trihydroxy-10-octadecenoic acid" is also written as "9,12,13-trihydroxyoctadec-10-enoic acid" or "9,12,13-trihydroxy-10-octadecenoic acid". Note that in the examples, the manufacturer's name is also written in parentheses. The above explanation also applies to all "octadecaenoic acid" used in this specification, claims, drawings, and abstract.

The structural formula of "9,10,13-trihydroxy-11-octadecaenoic acid" is shown in the following structural formula (1).

The structural formula of "9,12,13-trihydroxy-10-octadecenoic acid" is shown in the following structural formula (2).

It is preferable that the plant activator further contains a surfactant and/or a diluent or carrier.

Preferably, the concentration of the hydroxylated fatty acid derivative or its salt or ester is 0.05 to 5 mg/L.

It is preferable that the plant activator is a plant activator used as a spray or immersion agent that is brought into contact with the stems, leaves, or roots of a plant, or as a soil drenching agent.

The plant activator is preferably a plant activator used for plants selected from the Brassicaceae, Poaceae, Leguminosae, Solanaceae, Rosaceae, Amaranthaceae, Cucurbitaceae, and Malvaceae families.

The plant activator of the present invention is easily decomposed in the environment, has low soil pollution and toxicity, and has excellent plant growth promoting effects.

1 is a graph showing the growth-promoting effect on plant weight of mizuna, a Brassicaceae plant. 1 is a graph showing the growth-promoting effect on the leaf length of mizuna, a Brassicaceae plant. 1 is a graph showing the growth-promoting effect on plant weight of spinach, an Amaranthaceae plant. 1 is a graph showing the growth-promoting effect on the leaf length of spinach, a plant of the Amaranthaceae family. 1 is a graph showing the expression level of resistance-inducing genes in tomato, a plant of the Solanaceae family. 1 is a graph showing the expression level of resistance-inducing genes in cucumber, a Cucurbitaceae plant. 1 is a graph showing the expression level of resistance-inducing genes in Arabidopsis thaliana, a plant of the Brassicaceae family.

The plant activator of the present invention is a hydroxylated fatty acid derivative,
The following formula (I) and/or (II):
HOOC-(R ¹ )-CH(OH)-CH(OH)-CH=CH-CH(OH)-R ² (I)

HOOC-(R ¹ )-CH(OH)-CH=CH-CH(OH)-CH(OH)-R ² (II)
During the ceremony,
R ¹ is a linear or branched hydrocarbon group having 4 to 12 carbon atoms, which may contain one or more double bonds and/or OH groups, and when it contains a double bond, the position of the double bond is not limited;
^R2 is a linear or branched hydrocarbon group having 2 to 8 carbon atoms, which may contain one or more double bonds and/or OH groups, and when it contains a double bond, the position of the double bond is not limited;
The present invention is characterized in that it contains, as an active ingredient, a hydroxylated fatty acid derivative having the structural formula represented by the following formula: or a salt or ester thereof. In particular, R ¹ is preferably --(CH ₂ ) _n -- (wherein n is an integer of 4 to 12). The present invention also relates to a plant activator containing, as an active ingredient, the compound of formula (I) and/or (II) or a salt or ester thereof, including all geometric isomers and stereoisomers.

In the present invention, "plant activation" means regulating the growth activity of a plant in some way to activate or maintain it, and includes growth promotion (a concept that includes the expansion of stems and leaves, promotion of tuber and root growth, etc.), dormancy suppression, induction and imparting of resistance to plant stress (e.g., disease, etc.), and plant growth regulating effects such as anti-aging. For example, by contacting a part of a stem, leaf, or root of a plant with the plant activator of the present invention, a growth promotion effect can be imparted to the plant. By inoculating the plant activator of the present invention, an increase in leaf length and leaf weight, which are growth indicators of the plant, and promotion of tuber or root growth can be confirmed in the plant body compared to an untreated plant, and therefore the plant activator of the present invention is considered to impart a growth promotion effect to the plant. By using the plant activator of the present invention, the growth of the plant body can be promoted, and the yield of the plant body such as vegetables, grains, and fruits can be increased. The plant growth promotion effect of the plant activator of the present invention is very high, and as a result, an excellent yield increase effect and improved harvest efficiency of commercial crops can be achieved.

9(S),10(S),13(S)-11(E)-trihydroxyoctadecenoic acid and/or 9(S),12(S),13(S)-10(E)-trihydroxyoctadecenoic acid and their derivatives, which are used as an example of a hydroxylated fatty acid derivative in one embodiment of the present invention, are suitable as plant activators of the present invention. In this specification, hydroxylated fatty acids or derivatives thereof including hydroxyoctadecenoic acid or its derivatives are collectively referred to as hydroxylated fatty acid derivatives.

The salt of the hydroxylated fatty acid derivative of the present invention is not particularly limited as long as it is one or more agriculturally acceptable salts such as ammonium salts, alkyl ammonium salts such as ammonium salts and tetramethylammonium salts, alkaline earth metal salts such as calcium salts and magnesium salts, alkali metal salts such as sodium salts, lithium salts and potassium salts, metal salts such as cobalt salts and manganese salts, and salts contained in fertilizers. For example, by making the hydroxylated fatty acid derivative into a salt form, high water solubility and/or low deliquescence can be obtained, and the hydroxylated fatty acid derivative may be easily handled. In addition, in the present invention, the salt of the hydroxylated fatty acid derivative includes various forms of salts of the hydroxylated fatty acid derivative, such as salts formed between the hydroxylated fatty acid derivative and an acid or base, hydrates thereof, and mixtures thereof.

Esters of the hydroxylated fatty acid derivatives of the present invention include, but are not limited to, methyl esters, ethyl esters, propyl esters, butyl esters, pentyl esters, isopentyl esters, octyl esters, etc.

As described below, the plant activator containing the hydroxylated fatty acid derivative of the present invention is characterized in that, when applied to a plant, it exhibits a significantly superior plant growth-promoting effect on the plant compared to known plant growth-promoting materials. This shows that the plant activator of the present invention has a high plant growth-promoting effect. It also shows that, when applied to a plant, it suppresses plant diseases by expressing resistance-inducing genes in the salicylic acid pathway and jasmonic acid pathway, which provide the plant with an immune mechanism against diseases.

The plant activator of the present invention may contain a compatible surfactant and/or diluent or carrier suitable for use in the plant activator, if necessary. For example, the diluent may improve the dispersibility of the hydroxylated fatty acid derivative, such as hydroxyoctadecenoic acid or its salt or ester, in the solvent. In addition, in order to improve the solubility and dispersibility of the hydroxylated fatty acid derivative used in the present invention in the diluent, surfactants such as dispersing agents and wetting agents may be contained. These added components are not particularly limited as long as they are agriculturally acceptable agents. In addition to the hydroxylated fatty acid derivative or its salt or ester, the plant activator of the present invention may further contain other components that are beneficial to plants, such as components normally used in pesticide formulations and one or more fertilizer components, other than the surfactant, diluent, and carrier.

The plant activator of the present invention may contain a hydroxylated fatty acid derivative or a salt or ester thereof, and the origin thereof is not particularly limited. The hydroxylated fatty acid derivative such as hydroxyoctadecenoic acid of the present invention or a salt or ester thereof may be obtained by chemical synthesis, or may be produced by using a microorganism or may be obtained by acting an enzyme derived from a microorganism on a substrate such as a fatty acid. The plant activator of the present invention may contain a desired concentration of a hydroxylated fatty acid derivative. For example, when hydroxyoctadecenoic acid produced by a microorganism is used as the hydroxylated fatty acid derivative, a mixture containing hydroxyoctadecenoic acid may be used for the plant activator. When a biosurfactant secreted by a microorganism is contained in the mixture, the dispersibility of the plant activator of the present invention may be improved even without the inclusion of the above-mentioned additive component. When the hydroxylated fatty acid derivative itself is insoluble, it may be emulsified by a biosurfactant and dispersed in water.

The plant activator of the present invention can be applied to plants by any method. There is no particular limitation as long as it is a method that contacts the plant body, such as the roots, stems, and leaves of the plant. It may be applied so as to directly contact the plant body, or it may be applied to a cultivation carrier such as soil in which the plant body is fixed. For example, the plant activator of the present invention can be used as a spray or immersion agent that contacts the stems, leaves, or roots of the plant, or as a soil irrigation agent. The plant activator of the present invention may also be used as a sustained-release agent by being contained in a porous structure or capsule, or impregnated in a sheet, etc. For storage stability, it may also be powdered together with an appropriate excipient by means of freeze-drying or spray-drying. The plant activator of the present invention imparts a plant growth promoting effect to the plant, and in the plant to which it is applied, it increases the yield by increasing the plant body, such as increasing the leaf length, plant weight, leaf number, and crop weight, and improves the harvest efficiency by increasing the number of stems per plant. It also suppresses plant diseases by expressing resistance genes.

The plant activator of the present invention can promote plant growth and suppress disease by simple treatment such as spraying, so there is no need to prepare special equipment, and in this respect, the present invention is also very advantageous. Furthermore, since hydroxyoctadecenoic acid, for example, is an oxide of a naturally occurring fatty acid, the plant activator of the present invention has a low environmental impact and is excellent in that it causes almost no chemical damage to the plants to which it is applied.

The application of the hydroxylated fatty acid derivative or its salt or ester, which is the active ingredient of the plant activator of the present invention, to the plant body and/or cultivation carrier can be carried out, for example, by a method in which the hydroxylated fatty acid derivative or its salt or ester is applied to the plant body and/or cultivation carrier in the form of a liquid dissolved or dispersed in water and/or a water-soluble solvent. For example, the liquid in which the hydroxylated fatty acid derivative or its salt or ester is dissolved or dispersed can be sprayed or applied to the above-ground parts (stems, leaves, etc.) of the target plant body. The plant activator of the present invention may be applied to the target plant at least once, for example, after germination and before harvest, or may be applied in multiple portions.

In one embodiment of the present invention, the hydroxylated fatty acid derivative or its salt or ester may be used at a concentration of 500 mg/L or less. The preferred concentration of the hydroxylated fatty acid derivative or its salt or ester depends on the plant species and its condition to which it is applied, but if the concentration exceeds 500 mg/L, there is a risk of causing phytotoxicity to the plant. There is no particular lower limit for the concentration of the hydroxylated fatty acid derivative or its salt or ester, but 0.05 mg/L or more is preferred. In a preferred embodiment of the present invention, the concentration of the hydroxylated fatty acid derivative or its salt or ester is 0.01 to 100 mg/L.

The plant to which the plant activator of the present invention can be applied is not particularly limited, and can be used effectively for plants in general, such as plants of the Poaceae, Fabaceae, Solanaceae, Rosaceae, Amaranthaceae, Malvaceae, Cucurbitaceae, and Brassicaceae. For example, the growth of plants such as grass, rice, wheat, and corn as Poaceae plants, tomato, eggplant, red pepper, green pepper, and potato as Solanaceae plants, strawberry as Amaranthaceae plants, spinach as Amaranthaceae plants, cotton and okra as Malvaceae plants, cucurbitaceae plants, cucumber, pumpkin, and watermelon as Brassicaceae plants, komatsuna and mizuna as Brassicaceae plants, is effectively promoted. In addition, the plants to which the plant activator is applied are not limited to wild-type plants, and may be, for example, mutants or transformants. Additionally, the varieties of each plant are not particularly limited.

The present invention will be described based on examples, but the present invention is not limited to only the examples.

Example 1 Growth Evaluation of Mizuna In Example 1, 9,10,13-trihydroxy-11-octadecenoic acid (Larodan Fine Chemicals, English: 9(S),10(S),13(S)-trihydroxy-11(E)-octadecenoic acid; Japanese: 9(S),10(S),13(S)-trihydroxy-11(E)-octadecenoic acid), 200 mg/L ethanol solution) and 9,12,13-trihydroxy-10-octadecenoic acid (Larodan Fine Chemicals, English: 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid; Japanese: 9(S),12(S),13(S)-trihydroxy-10(E)-octadecenoic acid), 200 mg/L ethanol solution) were used. A mixture of these (ethanol solution) and (meth)-2-hydroxyoctadecanoic acid in a ratio of 2:1 was used as a trihydroxyoctadecanoic acid solution.

As a comparative example, a plant activator containing ketol fatty acids and fatty acid metabolites prepared by the following method was used.

Preparation of ketol fatty acid 10 mg of soybean-derived lipoxidase (Sigma-Aldrich) was added to a linoleic acid suspension consisting of 1 g of linoleic acid, 0.15 g of potassium dihydrogen phosphate, and 100 mL of distilled water, and the mixture was stirred for 24 hours to produce lipid peroxide 1. The production of lipid peroxide was confirmed by comparison with a standard substance by TLC (developing solvent chloroform:ethanol=20:1, sulfuric acid coloring) and by an increase in OD234 nm. In addition, it was confirmed by NMR that the main component of lipid peroxide 1 was 13-HPODE ((9Z,11E)-13-(hydroperoxy)-9,11-octadecadienoic acid). 0.1 mg of allene oxide synthase (Sigma-Aldrich) was added to the obtained peroxide 1, and the mixture was stirred for 24 hours to produce ketol fatty acid, and then the enzyme reaction was stopped by adding dilute hydrochloric acid under ice cooling to adjust the pH of the reaction solution to 3.0. The pH was then adjusted to 6.5 to give an aqueous solution of ketol fatty acid (9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid, 13-KODA).

Preparation of plant activator containing fatty acid metabolites <Preculture step>
20 g of peptone (protein hydrolysate manufactured by Difco), 1.5 g of magnesium sulfate heptahydrate, and 1.5 g of dipotassium hydrogen phosphate were dissolved in 1 L of water in a glass Erlenmeyer flask, sterilized by autoclaving at 121°C for 20 minutes, cooled to room temperature, and then the flask was filled with proteobacteria derived from activated sludge used in wastewater treatment (Azoarcus buckelii, Propionivibrio pelophilus, Thauera selenatis, Pandoraea pulmonicola, Pusillimonas noertemannii, Rhodovulum kholense, Haematobacter massiliensis, Hyphomicrobium hollandicum, Chelatovorus multitrophus, Nitrosococcus halophilus, Thioalkalivibrio thiocyanodenitrificans, Marinobacter hydrocarbonoclasticus, Halomonas xinjiangensis, Pseudomonas A bacterial solution of a complex flora including C. pertucinogena was inoculated into the culture vessel. The opening of the culture vessel was sealed with a silicone plug. After the inoculation, the vessel was cultured for 24 hours at 20°C and 120 rpm using a bioshaker (BR-23UM, Taitec Corporation). The number of bacteria in the culture solution was 5 x 10 ⁸ cells/mL. After the culture, the culture solution was centrifuged at 15,000 x G and 20°C to separate the bacteria from the culture solution, and the bacteria were collected.
<Fatty acid metabolism process>
12 g of linoleic acid (primary linoleic acid manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 1.5 g of magnesium sulfate heptahydrate, 1.5 g of dipotassium hydrogen phosphate, and the total amount of the bacterial cells obtained in the pre-culture step were added to 1 L of sterilized water in a glass Erlenmeyer flask. This was cultured for 4 days under conditions of 20°C, 120 rpm, and a dissolved oxygen concentration of 4 mg/L using a Bioshaker (registered trademark) (BR-23UM manufactured by Taitec Co., Ltd.). The decomposition of linoleic acid was confirmed by analyzing the culture solution by measuring the absorbance at a wavelength of 230 nm using a spectrophotometer BioSpec-mini manufactured by Shimadzu Corporation, and by the production level of oxidized lipids, which are one of the intermediate products of linoleic acid. The culture solution containing the bacterial cells after the culture was used as the fatty acid metabolite contained in the fatty acid metabolite-containing plant activator.

Dilutions were prepared by adding distilled water to the above-obtained trihydroxyoctadecaenoic acid solution, ketol fatty acid aqueous solution, and culture solution containing fatty acid metabolites to give final concentrations of trihydroxyoctadecaenoic acid, ketol fatty acid, and fatty acid metabolite of 0.05 mg/L, and these were used as treatment solutions. A 72-hole cell tray was filled with culture soil (Takii Seed Co., Ltd., product name "Seed Maki Culture Soil"), and seeds of mizuna that had been subjected to germination treatment were sown. After germination, the mizuna seedlings were thinned to two plants per cell. The light conditions were set to 12 hours light/12 hours dark. Water was replenished by irrigating with an appropriate amount of tap water about once every four days. Nine and 12 days after sowing, each treatment solution was sprayed (300 L/10 a) onto the above-ground parts of the plants using a sprayer, and applied to the leaves. No treatment solution was sprayed on the negative control ("untreated area").

The plants were harvested 21 days after sowing, and the wet weight of the aboveground part and the length of the leaves per plant were measured. The results are shown in Figures 1 and 2, respectively.

As shown in Figures 1 and 2, the average above-ground wet weight and leaf length of the mizuna plants (n=20) treated with a hydroxyoctadecenoic acid treatment solution were both increased compared to the untreated area. The above-ground wet weight was 0.19 g/plant in the untreated area, while the hydroxyoctadecenoic acid treatment area was 0.35 g/plant. The leaf length was 8.1 cm in the untreated area, while the hydroxyoctadecenoic acid treatment area was 9.6 cm. As a result of the t-test, significant differences were observed in both above-ground wet weight and leaf length in the area treated with a hydroxyoctadecenoic acid treatment solution compared to the untreated area. In contrast, there was almost no increase in above-ground wet weight in the areas treated with a fatty acid metabolite or ketol acid treatment solution. Furthermore, the leaf length was reduced in the area treated with a ketol fatty acid treatment solution.

Example 2 Evaluation of spinach growth A 72-well cell tray was filled with culture soil (Takii Seed Co., Ltd., product name "Seed Maki Culture Soil"), and spinach seeds that had been subjected to a germinated treatment were sown. After germination, the spinach seedlings were thinned out to two plants per cell. Light conditions were set at 12 hours light and 12 hours dark. Water was replenished by irrigating with an appropriate amount of tap water about once every three days. The treatment solution used was the hydroxyoctadecenoic acid treatment solution prepared in Example 1, and 16 days after sowing, the treatment solution was sprayed onto the above-ground parts of the plants (300 L/10 a) using a sprayer to apply it to the leaves. The negative control was not sprayed with the treatment solution ("untreated area").

The plants were harvested 23 days after sowing, and the wet weight of the aboveground part and the length of the leaves per plant were measured. The results are shown in Figures 3 and 4, respectively.

As shown in Figures 3 and 4, the average above-ground wet weight and leaf length of spinach (n=46) in the treatment area with hydroxyoctadecenoic acid treatment increased compared to the untreated area. The above-ground wet weight was 0.20 g/plant in the untreated area, and 0.26 g/plant in the hydroxyoctadecenoic acid treatment area. The leaf length was 5.2 cm in the untreated area, and 5.7 cm in the hydroxyoctadecenoic acid treatment area. The results of the t-test showed significant differences in both above-ground wet weight and leaf length in the treatment area with hydroxyoctadecenoic acid treatment compared to the untreated area.

As shown in Figures 1 to 4, an increase in the wet weight of the aboveground parts and an increase in leaf length were confirmed for water mustard, a plant of the Brassicaceae family, and spinach, a plant of the Amaranthaceae family. It can be seen that the plant activator of the present invention has an excellent growth promoting effect on plants.

Example 3 Evaluation of Resistance Induction in Tomato Distilled water was added to the trihydroxyoctadecenoic acid (trihydroxyoctadecenoic acid) solution (ethanol solution of a mixture of 9,10,13-trihydroxy-11-octadecenoic acid and 9,12,13-trihydroxy-10-octadecenoic acid) prepared in the first part of Example 1 so that the final concentrations of trihydroxyoctadecenoic acid were 5 mg/L (5 ppm) and 50 mg/L (50 ppm), respectively, to prepare two types of treatment solutions.

Tomato seedlings at the two-leaf stage (variety: CF House Momotaro; purchased from Ibigawa Kogyo Co., Ltd.) were replanted in 9 cm pots filled with soil (Takii Seed Co., Ltd., product name "Seed-Maki Soil"). The temperature was kept constant at 30°C, and the light conditions were set to 12 hours light and 12 hours dark with fluorescent lights. Water was supplied by irrigating with an appropriate amount of tap water about once a day. 24 hours after replanting, the treatment solution of the two types of hydroxyoctadecenoic acid prepared above was sprayed onto the above-ground parts of the plants (10 mL/plant) as a foliar spray. Distilled water was sprayed on the negative control ("untreated area").

48 hours after foliar spraying, RNA was extracted from the leaves of each tomato treated with each treatment solution and from untreated tomato plants as a control using a commercially available RNA extraction kit (GPR1002, Viogene), cDNA was prepared from the RNA, and the expression levels of the resistance genes PR-1b, PR-2a, PR-2b, PR-3a, PR-3b, and PR-5 were examined by real-time PCR. The gene expression levels were standardized by the expression levels of housekeeping genes. Three tomato seedlings were tested for each treatment group, and the average expression levels obtained are shown in Figure 5. The types of resistance genes measured were based on the Japanese Journal of Plant Pathology, 2017, Vol. 83, pp. 3-9. PR-1b, PR-2a, PR-3a, and PR-5 are resistance genes of the salicylic acid pathway, and PR-2b and PR-3b are resistance genes of the jasmonic acid pathway.

Example 4 Evaluation of Resistance Induction in Cucumber Distilled water was added to the trihydroxyoctadecenoic acid (trihydroxyoctadecenoic acid) solution (ethanol solution of a mixture of 9,10,13-trihydroxy-11-octadecenoic acid and 9,12,13-trihydroxy-10-octadecenoic acid) prepared in the first half of Example 1 so that the final concentration of trihydroxyoctadecenoic acid was 50 mg/L (50 ppm) to prepare a diluted solution, which was used as a treatment solution.

Cucumber seedlings at the two-leaf stage (variety: Hokushin; purchased from Ibigawa Kogyo Co., Ltd.) were replanted in 9 cm pots filled with soil (Takii Seed Co., Ltd., product name "Seed Maki Soil"). The temperature was kept constant at 25°C, and the light conditions were set to 12 hours light and 12 hours dark with fluorescent lights. Water was supplied by irrigating with an appropriate amount of tap water about once a day. Five days after replanting, the treatment solution of hydroxyoctadecenoic acid prepared above was sprayed onto the above-ground parts of the plants (10 mL/plant) as a foliar spray. Distilled water was sprayed as a negative control ("untreated area").

The expression levels of the resistance genes PR-8 and POX were examined in cucumbers treated with the treatment solution 72 hours after foliar spray and in untreated cucumbers as a control, using the same procedures as in Example 3. Three cucumber seedlings were tested for each treatment group, and the average expression levels obtained are shown in Figure 6. The types of resistance genes measured were based on those in "Journal of Plant Molecular Breeding, 2016, Vol. 4, No. 2, pp. 33-40" and "Sono Gakuken, 2011, Vol. 10, No. 3, pp. 429-433". PR-8 and POX are resistance genes in the salicylic acid pathway.

Example 5 Evaluation of Resistance Induction in Arabidopsis thaliana Distilled water was added to the trihydroxyoctadecenoic acid (trihydroxyoctadecenoic acid) solution (ethanol solution of a mixture of 9,10,13-trihydroxy-11-octadecenoic acid and 9,12,13-trihydroxy-10-octadecenoic acid) prepared in the first half of Example 1 to prepare dilutions with final trihydroxyoctadecenoic acid concentrations of 4 mg/L (4 ppm) and 40 mg/L (40 ppm), and two types of treatment solutions were prepared.

Arabidopsis seeds (Col-0; purchased from Inplanta Innovations, Inc.) were sown at a density of 1 seed/1 cm2 on a 3 cm x 3 cm x 3 ^cm rock wool (Daiwa Plastics, Rock Wool Block 60P) as a solid medium. The temperature was kept constant at 22°C, and the light conditions were set to 12 hours light/12 hours dark with fluorescent lights. For 15 days after sowing, the rock wool was immersed in a culture solution prepared by diluting a commercially available liquid fertilizer (Sumitomo Chemical Gardening, Vegeful liquid fertilizer) 1000 times, and the plants were grown hydroponically. After 15 days, 13 mL of the treatment solution of the two types of hydroxyoctadecenoic acid prepared above was added to the rock wool, and the mixture was left to stand for 5 hours, after which the original culture solution was replaced and the plants were continued to grow. The negative control was not treated with the treatment solution ("untreated area").

24 hours after treatment, the expression levels of the resistance genes PR-1, PR-2, and PDF1.2 were examined in Arabidopsis plants treated with each treatment solution and untreated Arabidopsis plants as a control using the same procedures as in Example 3. Three Arabidopsis seedlings were tested for each treatment group, and the average expression levels obtained are shown in Figure 7. The types of resistance genes measured were based on "PLoS ONE, Vol. 9, No. 1, e86882." PR-1 and PR-2 are resistance genes in the salicylic acid pathway, and PDF1.2 is a resistance gene in the jasmonic acid pathway.

As can be seen from Figure 5 (Example 3), Figure 6 (Example 4), and Figure 7 (Example 5), increased expression of the resistance genes was confirmed in tomato (Solanaceae), cucumber (Cucurbitaceae), and Arabidopsis (Brassicaceae). It can be seen that the plant activator of the present invention has an excellent disease suppression effect on plants.

The above results show that the plant activator of the present invention is an excellent plant activator that has low soil contamination and toxicity, can promote plant growth, and can also suppress plant diseases by expressing resistance genes.

Claims (5)

The following formula (I) and/or (II):
HOOC-(R ¹ )-CH(OH)-CH(OH)-CH=CH-CH(OH)-R ² (I)
HOOC-(R ¹ )-CH(OH)-CH=CH-CH(OH)-CH(OH)-R ² (II)
During the ceremony,
R ¹ is a linear or branched hydrocarbon group having 4 to 12 carbon atoms, which may contain one or more double bonds and/or OH groups, and when it contains a double bond, the position of the double bond is not limited;
^R2 is a linear or branched hydrocarbon group having 2 to 8 carbon atoms, which may contain one or more double bonds and/or OH groups, and when it contains a double bond, the position of the double bond is not limited;
A plant activator comprising, as an active ingredient, a hydroxylated fatty acid derivative having the structural formula:
A plant activator for promoting the expansion of stems and leaves or the growth of tubers and roots, wherein the hydroxylated fatty acid derivative is 9,10,13-trihydroxy-11-octadecenoic acid and/or 9,12,13-trihydroxy-10-octadecenoic acid . The plant activator according to claim 1 , further comprising a surfactant and/or a diluent or carrier. 3. The plant activator according to claim 1 , wherein the concentration of the hydroxylated fatty acid derivative or its salt or ester is 0.05 to 5 mg/L. 4. The plant activator according to claim 1, which is used as a spray or immersion agent to be brought into contact with the stems, leaves or roots of a plant, or as a soil drench agent. The plant activator according to any one of claims 1 to 4 , which is used for a plant selected from the group consisting of Brassicaceae, Poaceae, Leguminosae, Solanaceae, Rosaceae, Amaranthaceae, Cucurbitaceae, and Malvaceae.

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