Strawberry cultivation method and plant vitalizer for strawberry cultivation

Abstract

To provide methods for improving the yield and quality of harvested strawberries.SOLUTION: According to a method for cultivating strawberries, a plant vitalizer contains an exogenous elicitor and an endogenous elicitor and is given to a young seedling at least once.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for cultivating strawberries using an exogenous elicitor and an endogenous elicitor, and a plant activator for cultivating strawberries. [Background technology]

[0002] Plant yields are affected by abiotic stresses such as sunshine duration, temperature, and rainfall, as well as biotic stresses such as pests and diseases. For example, strawberries prefer abundant sunlight and a relatively cool climate with an optimum temperature of 17–25°C. High temperatures can lead to growth disorders and inhibition of flower bud differentiation. Poor drainage and excessive humidity can also lead to root rot, poor fruit set, and increased susceptibility to disease. To increase crop yields, various fertilizers and pesticides have been used. Fertilizers provide nutrients necessary for plant growth but do not alleviate stress. Pesticides directly control plant pests and diseases and eliminate biotic stress. While pesticide use has been fully documented, concerns remain about the impact of excessive use on humans and the environment. Chemically synthesized pesticides, in particular, can persist in soil for long periods after application. Therefore, alternative methods for enhancing resistance to biotic stress have been desired. For this reason, in addition to these, the use of biostimulants has recently been attracting attention as substances that are safe for both the human body and the environment.

[0003] "Biostimulants," also known as "biostimulants" or "plant activators," are any group of substances or microorganisms that, when applied to plants or their root systems, stimulate a series of processes that occur naturally in crops, thereby improving nutrient absorption, increasing fertilizer efficiency, conferring stress tolerance, and improving crop quality. They do not have a direct effect on pests and diseases and are therefore not classified as insecticides or fungicides. Biostimulants are naturally occurring substances (including microorganisms) that are not plant hormones or nutrients, but that stimulate plant vitality and promote growth even in very small amounts. Applying biostimulants to plants is believed to increase plant nutrient absorption and utilization, promoting growth and improving crop yield and quality. Agricultural biostimulants include a variety of compounds, substances, and other products applied to plants or soil to control or enhance physiological processes in crops. Biostimulants act on plant physiology through pathways different from nutrients to improve crop vigor, yield, quality and post-harvest storability. In this way, biostimulants can stimulate the innate abilities of plants and promote their growth without causing the problems associated with conventional pesticides and fertilizers.

[0004] Related to such biostimulants, the following have been reported so far: a plant stimulant that combines chitin oligosaccharides with chitosan or the like having antibacterial activity (Patent Document 1); a plant stimulant that combines vinegar with oligosaccharides and plant extracts (Patent Document 2); a plant growth promoter that contains cellulose (Patent Document 3); a plant growth regulator that contains a hexofuranose derivative (Patent Document 4); a method for increasing plant disease resistance using depolymerized chitin or chitosan (Patent Document 5); and a fertilizer that contains chitin and / or chitosan or the like (Patent Document 6). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-143013 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-64112 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-114610 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-151438 [Patent Document 5] Japanese Patent Application Laid-Open No. 2015-48436 [Patent Document 6] Japanese Patent Application Laid-Open No. 2017-95352 [Patent Document 7] International Publication No. 2017 / 104687 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in plant cultivation, there have been no studies to date on how to enhance the effects of plant activators by adjusting the application method depending on the plant species. In particular, no method for applying plant activators that is suitable for strawberries has been known. [Means for solving the problem]

[0007] The present invention was made in consideration of the above circumstances, and the inventors have conducted extensive research into how to apply a plant activator to strawberry cultivation. As a result, they have found that applying a plant activator containing an exogenous elicitor and an endogenous elicitor to strawberry seedlings significantly improves yield and quality, which led to the completion of the present invention.

[0008] That is, the present invention includes the following [1] to

[26] . [1] A method for cultivating strawberries, comprising applying a plant stimulant containing an exogenous elicitor and an endogenous elicitor to seedlings at least once. [2] The method for cultivating strawberries according to [1], which comprises applying the plant vitalizer at least once to seedlings that are 2 to 15 days old after germination. [3] The method for cultivating strawberries according to [1] or [2], further comprising applying the plant vitality agent to the plant body at least once after the seedling stage. [4] The method for cultivating strawberries according to any one of [1] to [3], wherein the seedlings are offspring sprouted from runners of a parent plant. [5] The method for cultivating strawberries described in [4], further comprising applying the plant vitality agent to the parent plant at least once during the period before the first offspring germinates from the grown runner. [6] A method for cultivating strawberries described in any of [1] to [5], wherein the exogenous elicitor is chitin oligosaccharide and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides. [7] The method for cultivating strawberries according to any one of [1] to [6], wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5. [8] The method for cultivating strawberries according to any one of [1] to [7], wherein the endogenous elicitor comprises xylooligosaccharide. [9] The method for cultivating strawberries according to [8], wherein the endogenous elicitor contains both cellooligosaccharides and xylooligosaccharides.

[10] The method for cultivating strawberries according to [9], wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant vitality agent is 0.2 to 5.

[11] The method for cultivating strawberries according to any one of [1] to

[10] , wherein the plant activator is administered to the plant at a concentration such that the total content of the exogenous elicitor and the endogenous elicitor is 0.1 to 500 ppm by mass.

[12] The method for cultivating strawberries according to any one of [1] to

[11] , wherein the plant vitalizer is applied to the plants by foliar spray.

[13] The method for cultivating strawberries according to any one of [1] to

[12] , wherein the strawberries are of a one-season variety.

[14] A plant activator used in strawberry cultivation, the plant activator comprising an exogenous elicitor and an endogenous elicitor, the plant activator being applied to seedlings at least once.

[15] The plant vitalizer according to

[14] , which is applied at least once to seedlings 2 to 15 days after germination.

[16] The plant vitalizer according to

[14] or

[15] , which is further applied at least once to a plant body after the seedling stage.

[17] The plant vitalizer according to any one of

[14] to

[16] , wherein the seedling is a plant that has germinated from a runner of a parent plant.

[18] The plant vitalizer according to

[17] , which is further applied to the parent plant at least once during the period before the first offspring germinates from the grown runner.

[19] The plant activator according to any one of

[14] to

[18] , wherein the exogenous elicitor is a chitin oligosaccharide and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides.

[20] The plant activator according to any one of

[14] to

[19] , wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5.

[21] The plant activator according to any one of

[14] to

[20] , wherein the endogenous elicitor is a xylooligosaccharide.

[22] The plant activator according to

[21] , wherein the endogenous elicitor contains both cellooligosaccharides and xylooligosaccharides.

[23] The plant activator according to

[22] , wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant activator is 0.2 to 5.

[24] The plant activator according to any one of

[14] to

[23] , which is applied to a plant at a concentration such that the total content of the exogenous elicitor and the endogenous elicitor is 0.1 to 500 ppm by mass.

[25] The plant vitalizer according to any one of

[14] to

[24] , which is applied to plants by foliar spray.

[26] The plant activator according to any one of

[14] to

[25] , wherein the strawberry is a one-season variety. [Effects of the Invention]

[0009] The strawberry cultivation method of the present invention can improve the yield and quality of the harvested product by applying a plant activator containing an exogenous elicitor and an endogenous elicitor to strawberry seedlings. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described. Note that the embodiments described below are representative examples of the present invention, and the present invention is not limited thereto.

[0011] The strawberry cultivation method of this embodiment includes applying a plant activator containing an exogenous elicitor and an endogenous elicitor to strawberry seedlings. The "plant activator" includes not only those that have the effect of alleviating abiotic stresses related to plant growth, such as temperature, light, water, and salt, but also those that have the effect of alleviating biotic stresses, such as those caused by pests and diseases.

[0012] Elicitors are a general term for substances that induce biological defense responses in tissues or cultured cells of higher plants, inducing disease resistance in the plant's immune system. Plants sense elicitors using receptors present on the leaf surface and initiate a pathogen resistance response. This triggers a biological defense mechanism (immunity) in which various compounds are secreted against various pathogens. When elicitors act on plants, defense responses such as the synthesis and accumulation of phytoalexins and infection-specific proteins, reactive oxygen species production, reactive nitrogen production, hypersensitive cell death, and changes in gene expression are induced. These responses are thought to protect plants from pathogens and enhance their disease resistance. Phytoalexins are antibacterial compounds synthesized and accumulated in plants through the action of elicitors, and the antibacterial compounds produced vary from plant to plant. Representative phytoalexins include flavonoids, terpenoids, and fatty acid derivatives. Reactive oxygen species have the ability to kill pathogenic microorganisms, and reactive oxygen species and reactive nitrogen species function, either alone or in concert, as signals to trigger various defense responses. Disease resistance through such elicitor effects is expected to be used in agriculture because it can enhance resistance to a wide range of diseases.

[0013] [Exogenous elicitor] As used herein, the term "exogenous elicitor" refers to an elicitor derived from a substance derived from a living organism other than a plant, such as a component derived from a fungus, insect, or crustacean. There are no particular limitations on the elicitor as long as it has an elicitor effect, but typical examples include chitin, chitosan, and their oligosaccharides, as well as various biomolecules derived from insects. The plant activator used in the strawberry cultivation method of this embodiment preferably contains chitin oligosaccharide as an exogenous elicitor.

[0014] Chitin oligosaccharides are oligosaccharides that contain partially deacetylated chitosan oligosaccharides and consist of several N-acetylglucosamine units. They are generally obtained by hydrolyzing chitin derived from crustaceans, etc., and are also called oligo-N-acetylglucosamines. Specifically, chitin oligosaccharides can be obtained by chemically or enzymatically partially hydrolyzing chitin, which is prepared by conventional methods from the shells of crustaceans such as crabs and shrimp. Chitin oligosaccharides are preferably prepared by one or a mixture of two or more selected from N-acetylchitobiose, N-acetylchitotriose, N-acetylchitotetraose, N-acetylchitopentaose, N-acetylchitohexaose, N-acetylchitoheptaose, and N-acetylchitooctaose. Among these, N-acetylchitopentaose, N-acetylchitohexaose, and N-acetylchitoheptaose have particularly strong elicitor effects.

[0015] The chitin oligosaccharide used in this embodiment is particularly preferably one having the following chemical structure: [ka] In addition, this also includes compounds in which some of the acetyl groups (-COCH3) in the formula have been lost, with -NHCOCH3 becoming -NH2.

[0016] [Endogenous elicitor] As used herein, the term "endogenous elicitor" refers to an elicitor derived from a plant, and is not particularly limited as long as it has an elicitor effect, but typically includes cellulose, xylan, and their oligosaccharides, etc., which are produced by plants. The plant activator used in the strawberry cultivation method of this embodiment preferably contains at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides as an endogenous elicitor.

[0017] Cellooligosaccharides are oligosaccharides formed by the polymerization of multiple glucose units via β-glycosidic bonds. Recently, they have been found to have functions such as moisture retention, suppression of stickiness, imparting a clean taste, reducing starch retrogradation, and inhibiting protein denaturation, and are expected to be used in the fields of medicine, cosmetics, food, and feed. Cellooligosaccharides with a glucose polymerization degree of 3 or more are particularly expected to enhance the above-mentioned functions and to impart new functions. Cellooligosaccharides currently used industrially are produced by enzymatic reactions, but they mainly contain glucose and the dimer cellobiose, and almost no oligomers higher than the trimer cellotriose. However, the applicants recently reported a method for producing cellooligosaccharides containing oligomers with a glucose polymerization degree of 3 to 6 by controlling the heating rate, cooling rate, reaction temperature, and reaction time in the hydrothermal reaction of plant biomass using a carbon catalyst (Patent Document 7).

[0018] The cellooligosaccharide used in this embodiment is particularly preferably one having the following chemical structure: [ka]

[0019] Xylooligosaccharides are oligosaccharides formed by the polymerization of several xylose units via β-glycosidic bonds. They are generally obtained by hydrolysis of xylan, the main component of hemicellulose, and are sold primarily for food applications.

[0020] The xylooligosaccharide used in this embodiment is particularly preferably one having the following chemical structure: [ka]

[0021] [Plant vitalizer] The plant activator used in the strawberry cultivation method of this embodiment contains at least the exogenous elicitor and the endogenous elicitor as active ingredients. The mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator (i.e., exogenous elicitor content / endogenous elicitor content) is preferably 0.1 to 5, more preferably 0.2 to 2, and even more preferably 0.3 to 0.6.

[0022] The plant vitalizer more preferably contains xylooligosaccharides as endogenous elicitors, and most preferably contains both cellooligosaccharides and xylooligosaccharides. The mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant vitalizer (i.e., cellooligosaccharide content / xylooligosaccharide content) is preferably 0.2 to 5, more preferably 0.3 to 3, and even more preferably 0.4 to 1.2.

[0023] When the plant vitalizer contains chitin oligosaccharides as an exogenous elicitor and both cellooligosaccharides and xylooligosaccharides as endogenous elicitors, the proportions of each oligosaccharide relative to the total content of chitin oligosaccharides, cellooligosaccharides, and xylooligosaccharides are preferably 10 to 50% by mass chitin oligosaccharides, 10 to 50% by mass cellooligosaccharides, and 10 to 60% by mass xylooligosaccharides, and more preferably 20 to 40% by mass chitin oligosaccharides, 20 to 40% by mass cellooligosaccharides, and 20 to 55% by mass xylooligosaccharides.

[0024] Plant activators may further contain other ingredients besides the active ingredients, exogenous elicitors and endogenous elicitors, such as preservatives, spreading agents, suspending agents, thickeners, excipients, and solvents. Examples of preservatives include potassium sorbate, parahydroxybenzoic acid esters, benzoin, sodium dehydroacetate, hinokitiol, phenoxyethanol, polyaminopropyl biguanide, and polylysine. Spreaders are viscous liquids primarily composed of surfactants. There are no particular limitations on the types of spreading agents that can be used as plant activators. Examples include polyoxyethylene nonylphenyl ether, sorbitan fatty acid esters, and polyoxyethylene hexitane fatty acid esters. Examples of suspending agents include polyphosphates or salts of polyphosphates, and polycarboxylic acid-type polymer surfactants. Examples of thickeners include water-soluble polymers such as carboxymethylcellulose (CMC), polyacrylamide, and starch, as well as blackstrap molasses, concentrated alcohol fermentation wastewater, and concentrated amino acid fermentation wastewater. Examples of excipients include lactose and starch. Solvents are used to dilute the active ingredient to an appropriate concentration to make it liquid and to facilitate spraying on plants. Water is preferred as the solvent.

[0025] The plant activator used in the strawberry cultivation method of this embodiment may be in any form, such as powder, granules, or liquid, but is generally preferably in liquid form for ease of application. When using a liquid plant activator, the active ingredient concentration in the plant activator at the time of application to plants is preferably 0.1 to 500 ppm by mass, more preferably 0.5 to 200 ppm by mass, and even more preferably 1 to 100 ppm by mass. The active ingredient concentration in the plant activator refers to the total content of exogenous elicitors and endogenous elicitors in the plant activator. When the application concentration is 0.1 ppm by mass or higher, the plant activator's effects are efficiently manifested. When the application concentration is 500 ppm by mass or lower, disease resistance can be manifested without inhibiting plant growth.

[0026] Although commercially available plant activators whose active ingredient concentrations have been adjusted to the above-mentioned concentrations may be used, a plant activator stock solution containing high concentrations of exogenous and endogenous elicitors is usually diluted with water before use. When the plant activator stock solution is diluted (for example, 1000 times), the total content of the exogenous and endogenous elicitors in the plant activator stock solution is preferably 0.05 to 10% by mass, more preferably 0.1 to 8% by mass, and even more preferably 0.5 to 6% by mass.

[0027] [strawberry] The strawberries cultivated by the cultivation method of this embodiment are preferably those classified as belonging to the genus Rubus. The type is not particularly limited, and either one-season or four-season varieties can be used, but one-season varieties are particularly preferred.

[0028] [Cultivation method] There are no particular limitations on the cultivation method for strawberries, but examples include outdoor cultivation, greenhouse cultivation, and hydroponic cultivation. In strawberry cultivation, the production of robust seedlings is important to ensure high-quality fruit and yield. Seeds can be sown directly in the field, but to produce robust seedlings, it is preferable to separate the sowing and raising of seedlings, and it is more preferable to harvest seedlings from runners that grow from the parent plant. It is preferable to plant the harvested seedlings in a seedbed, nursery box, or nursery pot, and then transplant the grown seedlings into the actual field for cultivation.

[0029] For example, when cultivating seedlings from runners growing from a parent plant, the following method can be used. In the Kanto region of Japan, parent seedlings are planted in April in a fertilized field for parent plants and thoroughly watered for about a week to promote rooting. Alternatively, plants harvested in the previous season can be used as parent plants without planting new parent seedlings. Runners extend from the parent plant in June or July, and these runners germinate one after another to form new plants (seedlings). The new plants that germinate from the runners are trained and fixed in seedbeds, pots, or seedling boxes, where they root and take root. The newly established seedlings are separated from the parent plant in August and harvested. The harvested seedlings are then raised for about a month. Until the seedlings take root, they should be protected from direct sunlight and the soil should be kept slightly moist. After rooting, it is recommended to gradually reduce irrigation to prevent root rot. Avoid extreme heat and excessive humidity during the seedling raising period, and transplant them to the main field around October. When caring for planted seedlings, it is best to maintain a slightly higher soil moisture level until they take root, and then gradually reduce watering to prevent root rot. To ensure the planted plants grow well, it is best to remove any runners or side shoots that appear during the vegetative growth period up until around November. They enter a winter dormancy period from December to February, and once this period is over, as temperatures rise, appropriate watering and fertilization will stimulate reproductive growth and lead to flowering. They can be harvested about one month after flowering.

[0030] The strawberry cultivation method of this embodiment includes applying the plant vitalizer to young seedlings. In this specification, "young seedlings" refers to seedlings up to three weeks old from germination when seeds are directly sown in a field, and refers to seedlings from germination to planting when sowing and raising are carried out separately. Furthermore, when seedlings are harvested from runners of parent plants, the term refers to seedlings from germination to harvesting to planting.

[0031] In one embodiment, to obtain healthy seedlings, the plant vitalizer is preferably used at least once on seedlings 2 to 15 days after germination, more preferably at least once on seedlings 2 to 10 days old, and even more preferably at least once on seedlings 3 to 7 days old. The plant vitalizer is preferably used 1 to 2 times, more preferably once, during the period 2 to 15 days after germination.

[0032] In another embodiment, when sowing and raising seedlings are carried out separately or when seedlings are collected from runners of parent plants, it is preferable to use the plant vitalizer at least once on the seedlings from 16 days after germination until transplanting. The number of times the plant vitalizer is used during the period from 16 days after germination until transplanting depends on the seedling raising period, but it is preferable to use it once every 5 to 30 days, and more preferably once every 10 to 20 days.

[0033] In another embodiment, when seeds are directly sown in a field, it is preferable to apply the agent at least once to seedlings 16 days to 3 weeks after germination.

[0034] To obtain fuller seedlings, it is more preferable to apply the plant vitalizer at least once to seedlings 2 to 15 days after germination, and then to seedlings at least once every 5 to 30 days.

[0035] In the strawberry cultivation method of this embodiment, when harvesting seedlings from runners of parent plants, the plant activator is preferably applied to the parent plants in addition to the young seedlings. When planting the parent plants, the plant activator is preferably applied from one week after planting to before the first offspring germinate from the runners, and more preferably thereafter until the runners are cut for harvesting. When using plants harvested in the previous season as parent plants, the plant activator is preferably applied from harvest to before the first offspring germinate from the runners, and more preferably thereafter until the runners are cut for harvesting. The frequency of application is preferably once every 5 to 30 days, more preferably once every 10 to 20 days. Furthermore, it is even more preferable to apply the plant activator to both the parent plants and offspring at the aforementioned frequency after the first offspring germinate from the runner, after the second offspring germinate from the runner, and after the third offspring germinate from the runner.

[0036] In another embodiment of the strawberry cultivation method of this embodiment, the plant vitalizer is preferably applied to a plant after the seedling stage. In this specification, "a plant after the seedling stage" refers to a plant after the "seedling" period. Specifically, in the case of direct seeding in a field, the term refers to a plant after three weeks have passed since germination. In the case of separate seeding and seedling raising, the term refers to a plant after planting. Furthermore, in the case of harvesting seedlings from runners of a parent plant, the term refers to a plant after the seedlings harvested from the runners have been planted.

[0037] In one embodiment, when sowing and raising seedlings separately or when harvesting seedlings from runners of parent plants, it is preferable to transplant seedlings around October when they have developed about 5 to 8 true leaves. To ensure sufficient sunlight, plant them shallowly to avoid overcrowding, and water them after transplanting to encourage them to take root. The plant activator is preferably applied at least once to the plant 1 to 2 weeks after planting. After that, until the plant enters the dormant period, it is preferably applied once every 5 to 30 days, more preferably once every 10 to 20 days. During the dormant period, the plant activator is preferably applied once every 10 to 40 days, more preferably once every 20 to 30 days. Furthermore, from the end of the dormant period until the harvest season, the plant activator is preferably applied once every 5 to 40 days, more preferably once every 10 to 30 days.

[0038] In another embodiment, when seeds are directly sown in a field, the plant vitalizer is preferably applied to the plant at least once three weeks after germination. From three weeks after germination until the plant enters the dormant period, the plant vitalizer is preferably applied once every five to thirty days, more preferably once every ten to twenty days. During the dormant period, the plant vitalizer is preferably applied once every ten to forty days, more preferably once every twenty to thirty days. Furthermore, from the end of the dormant period until the harvest season, the plant vitalizer is preferably applied once every five to forty days, more preferably once every ten to thirty days.

[0039] (Application of plant vitalizers) The plant activator can be applied to strawberries by methods conventional in the art, and the application method is not particularly limited. For example, it may be applied directly to the leaves, stems, etc. of the plant, applied to the culture medium or soil for growing the plant, or incorporated into fertilizer and then applied to the culture medium or soil. When incorporated into fertilizer, the type of fertilizer is not limited, and may include chemical fertilizers containing nitrogen, phosphate, and potassium, as well as organic fertilizers such as oil cakes, fish cakes, bone meal, seaweed powder, amino acids, sugars, and vitamins. Foliar application is particularly preferred for effectively expressing elicitor activity. Foliar application can be carried out using methods conventional in the art, such as power sprayers, shoulder sprayers, broadcasters, sprayers, manned or unmanned helicopters, foggers, and hand sprayers.

[0040] The amount of plant vitalizer to be sprayed is 1cm on the leaves. 2 The amount of active ingredient to be sprayed per 1cm of leaf surface is preferably 0.1ng to 100ng. 2 It is more preferable that the amount of active ingredient to be sprayed is 1 ng to 20 ng per 100 m2 of cultivated area. In actual fields, it is difficult to selectively spray only on the leaves and to have all of the sprayed material adhere to the leaves. 2 It is preferable to dilute 0.01 g to 20 g of the active ingredient per 100 m of cultivated area so that the concentration in the plant vitalizer is 1 ppm by mass to 100 ppm by mass, and spray the diluted solution evenly over the plants. 2 It is preferable to dilute 0.1 g to 10 g of the active ingredient per unit amount so that the concentration in the plant vitalizer is 10 ppm by mass to 500 ppm by mass.

[0041] In the strawberry cultivation method of this embodiment, soil management is preferably carried out according to conventional farming methods.

[0042] (Effects of plant vitalizers) The strawberry cultivation method of this embodiment involves applying a plant activator containing an exogenous elicitor and an endogenous elicitor to strawberry seedlings. It is also preferable to continue applying the plant activator containing an exogenous elicitor and an endogenous elicitor to strawberry plants after the seedling stage. The reason why applying a plant activator with such a configuration at this stage is effective is not fully understood. Applying an exogenous elicitor (e.g., derived from chitin oligosaccharides) confers disease resistance and other properties derived from herbivores to plants, but excessive application is thought to inhibit growth. On the other hand, applying an endogenous elicitor (e.g., derived from cellooligosaccharides or xylooligosaccharides) is expected to enable plants to recognize their own cellular damage and disruptive components (DAMPs: damage-associated molecular patterns) and promote their own growth in order to acquire immunity and repair cells. In the strawberry cultivation method of this embodiment, applying a plant activator containing an exogenous elicitor and an endogenous elicitor, particularly at the early seedling stage, is believed to enable the cultivation of robust seedlings that are conferred disease resistance while suppressing growth inhibition. By subsequently applying a plant activator to the strong plants thus cultivated, the growth-promoting effects of the endogenous elicitor can be utilized without the strong growth-inhibiting effects of the exogenous elicitor, ultimately achieving a high growth effect through the complementary action of the two. Therefore, in cultivating strawberries, applying the plant activator at least once to seedlings and at least once to plants after the seedling stage is expected to result in robust plant growth and improved yield and quality.

[0043] The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited thereto. [Example]

[0044] 1. Preparation of oligosaccharides (1) Chitin oligosaccharides 10 g of chitin powder (purified chitin, manufactured by Wako Pure Chemical Industries) was dispersed in 30 mL of water containing 1.2 g of 85% phosphoric acid (special grade reagent, manufactured by Wako Pure Chemical Industries). The powder was dried under reduced pressure and placed in a 250 mL alumina pot together with 100 g of 5 mm diameter alumina balls. The pot was then placed in a planetary ball mill (PULVERISETTE 6, manufactured by Fritsch) and processed at 500 rpm for 6 hours to obtain the reaction product. The temperature was started at room temperature, and the temperature increase due to shear heat generation was allowed to proceed. Next, the reaction product was suspended in water and neutralized with calcium hydroxide to form a slurry, which was then filtered through a Nutsche filter using 5B filter paper. The collected filtrate was freeze-dried to obtain chitin oligosaccharide powder.

[0045] (2) Cellooligosaccharides 271 g (moisture content 1.8%, dry mass 266 g) of cotton linter pulp (Tokyo Kosen Co., Ltd., cellulose content 97%) was mixed with 38 g of 85% by mass phosphoric acid (special grade reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) using a food blender (model number: HBF500S, Hamilton Beach) to obtain 309 g of reaction raw material (moisture content 3.4%, phosphoric acid content 10.4%). Next, 309 g of the reaction raw materials were placed in a vibration mill (device name: MB-1 type, manufactured by Chuo Kakoki Co., Ltd., pot size: 5 L) together with 13 kg of φ3 / 4 inch carbon steel balls, and subjected to a hydrolysis reaction by dry grinding for 24 hours under conditions of a total amplitude of 8 mm, a vibration frequency of 16.2 Hz, and a jacket circulating water temperature of 75°C, after which the reaction powder was recovered. 10 g of this reaction powder and 90 g of ion-exchanged water were placed in a 200 L beaker and stirred at 25° C. for 1 hour using a magnetic stirrer to obtain an extract of the cellulose hydrolysate. Next, 1.3 g of 40% by weight calcium hydroxide aqueous solution was added to the extract, and the mixture was stirred for 1 hour at 25°C using a magnetic stirrer to prepare a neutralized solution. The supernatant was then recovered using a centrifuge and freeze-dried to obtain cellooligosaccharide powder.

[0046] (3) Xylooligosaccharides Acremonium Cellulolyticus The TN strain (FERM P-18508) was cultured in a 500 mL flask containing 100 mL of liquid medium (Avicel 50 g / L, KH2O 424 g / L, ammonium sulfate 5 g / L, potassium tartrate 1 / 2H2O 4.7 g / L, urea 4 g / L, Tween 80 1 g / L, MgSO4·7H2O 1.2 g / L, ZnSO4·7H2O 10 mg / L, MnSO4·5H2O 10 mg / L, and CuSO4·5H2O 10 mg / L) at 30°C for 6 days with shaking. 5 g of corncob powder was suspended in 50 mL of the centrifuged culture supernatant and incubated at 50°C for 72 hours with stirring. The resulting supernatant was freeze-dried to obtain the xylooligosaccharide bulk powder.

[0047] [2. Strawberry cultivation] (1) Preparation of plant vitalizer Each oligosaccharide prepared in [1. Preparation of Oligosaccharides] was dissolved in water with stirring at the respective composition ratios to achieve 1000 times the active ingredient concentration (ppm by mass) of the plant vitalizers shown in Examples 1 to 12 and Comparative Examples 1 to 5 in Table 1. The resulting solution was then sterilized with a 0.45 μm filter to prepare a plant vitalizer stock solution. This stock solution was diluted 1000 times with water and used in the following cultivation tests. Hereinafter, the plant vitalizer obtained after diluting the stock solution 1000 times may be referred to as the "diluted plant vitalizer solution." Note that the composition ratio of each oligosaccharide in the table is expressed as % by mass.

[0048] (2) Cultivation Test 1 (Examples 1 to 12, Comparative Examples 1 to 5) (Parent plant cultivation ~ Seedling cultivation) Two weeks before planting, parent plants (one-season variety: Akihime) were planted in rows 200cm wide and 80cm apart in a field that had been fertilized and thoroughly watered. The parent plants were divided into 20 plots of four plants per plot, and seedlings that germinated from the runners that grew were trained into seedling pots and pinned down to root. When the first to third offspring of each runner that grew from the parent plant had taken root and had developed two to four true leaves, the runners were cut off and independent seedlings were harvested, 28 plants per plot (7 plants per parent plant). The seedlings harvested in the pots were thoroughly watered to encourage rooting, and then cultivated for 1.5 months while removing leaves until they had three to five true leaves. (Planting to harvesting) Field cultivation is a total of 80m 2 A field in a greenhouse was used. Ridges 60cm wide and 10cm high were created in the deeply plowed field, and planted in two rows with 30cm spacing between plants. The best-growing seedlings were selected from the raised strawberry seedlings and planted in 20 plots, 20 plants per plot. The plants were watered thoroughly for two weeks after planting, and then, once new leaves had emerged, watering was continued only when the soil surface dried. Conventional farming methods were followed for soil management and plant care (leaf removal, top pinching, fruit thinning, etc.) during the cultivation period from planting to harvest. (Use of plant vitalizers) The diluted solution of the plant vitalizer was sprayed on the leaves and soil of parent plants, seedlings, and plants after the seedling stage under the conditions shown in Table 1 until the leaves and soil were moist. Aqueous solutions (diluted plant stimulants) prepared to the active ingredient concentration of each plant stimulant were prepared at 1.0 kg per plot each time, and sprayed onto the leaves using a watering can and onto the soil near the roots. The ripe red fruits were harvested one by one, and the average yield and average sugar content per plant were measured for 20 plants (one plot) and compared under each condition. The average sugar content was measured using a saccharometer for 20 fruits from each plot. The test results are shown in Table 1.

[0049] [Table 1]

[0050] [3. Cultivation of Brassicaceae Plants (Reference Examples 1-3)] A test was conducted using Komatsuna, a member of the Brassicaceae family. Compost was incorporated into the cultivated field, and ridges were made with 15-20cm spacing between rows. Komatsuna (Inamura variety) seeds were sown in rows 1-1.5cm apart, lightly covered with soil, and then tamped down, followed by thorough watering. The germinated komatsuna seeds were thinned out as needed, and a diluted solution of the plant vitalizer was sprayed on the leaves and soil to moisten them, under the conditions listed in Table 2. The seeds were harvested when they reached a height of 20-25cm, and the harvest weight per plant was compared for 20 seedlings. The test results are shown in Table 2.

[0051] [Table 2]

[0052] The results in Table 1 show that in strawberry cultivation, using a plant stimulant containing both exogenous and endogenous elicitors on seedlings significantly improves yield and produces strawberries with high sugar content. On the other hand, the results in Table 2 show that in the cultivation of komatsuna, a Brassicaceae plant, no significant improvement in weight per plant was observed even when a plant stimulant containing both exogenous and endogenous elicitors was used on seedlings during the growth period before harvest.

Claims

1. A method for cultivating strawberries, comprising applying a plant vitalizer containing an exogenous elicitor and an endogenous elicitor to seedlings at least once, wherein the exogenous elicitor is chitin oligosaccharide, and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides.

2. 2. The method for cultivating strawberries according to claim 1, comprising applying the plant vitalizer at least once to seedlings 2 to 15 days after germination.

3. The method for cultivating strawberries according to claim 1 or 2, further comprising applying the plant vitalizer to a plant body after the seedling stage at least once.

4. The method for cultivating strawberries according to any one of claims 1 to 3, wherein the seedlings are offspring germinated from runners of a parent plant.

5. 5. The method for cultivating strawberries according to claim 4, further comprising applying the plant vitalizer to the parent plant at least once during a period before the first offspring sprouts from the grown runner.

6. The method for cultivating strawberries according to any one of claims 1 to 5, wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5.

7. The method for cultivating strawberries according to any one of claims 1 to 6, wherein the endogenous elicitor is a xylooligosaccharide.

8. The method for cultivating strawberries according to claim 7, wherein the endogenous elicitor comprises both cellooligosaccharides and xylooligosaccharides.

9. 9. The method for cultivating strawberries according to claim 8, wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant vitalizer is 0.2 to 5.

10. The strawberry cultivation method according to any one of claims 1 to 9, wherein the plant activator is applied to the plant at a concentration such that the total content of the exogenous elicitor and the endogenous elicitor is 0.1 to 500 ppm by mass.

11. The method for cultivating strawberries according to any one of claims 1 to 10, wherein the plant vitalizer is applied to the plant by foliar spraying.

12. The method for cultivating strawberries according to any one of claims 1 to 11, wherein the strawberries are one-season varieties.

13. A plant activator containing an exogenous elicitor and an endogenous elicitor for use in strawberry cultivation, wherein the plant activator is applied to a seedling at least once, and the exogenous elicitor is a chitin oligosaccharide, and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides.

14. The plant vitalizer according to claim 13, which is applied at least once to seedlings 2 to 15 days after germination.

15. The plant vitalizer according to claim 13 or 14, which is further applied at least once to a plant body after the seedling stage.

16. The plant activator according to any one of claims 13 to 15, wherein the seedling is a young plant germinated from a runner of a parent plant.

17. The plant vitalizer according to claim 16, which is further applied to the parent plant at least once during the period before the first offspring germinate from the grown runner.

18. The plant activator according to any one of claims 13 to 17, wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5.

19. The plant activator according to any one of claims 13 to 18, comprising a xylooligosaccharide as the endogenous elicitor.

20. The plant activator according to claim 19, comprising both cellooligosaccharides and xylooligosaccharides as the endogenous elicitor.

21. The plant activator according to claim 20, wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant activator is 0.2 to 5.

22. The plant activator according to any one of claims 13 to 21, which is applied to a plant at a concentration such that the total content of the exogenous elicitor and the endogenous elicitor is 0.1 to 500 ppm by mass.

23. The plant vitalizer according to any one of claims 13 to 22, which is applied to plants by foliar spray.

24. The plant activator according to any one of claims 13 to 23, wherein the strawberry is a one-season variety.

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