Fruit tree cultivation method and plant vitalizer for fruit tree cultivation

Abstract

To provide methods for improving the yield and quality of harvested fruit trees.SOLUTION: According to a method for cultivating fruit trees, a plant vitalizer contains an exogenous elicitor and an endogenous elicitor and is given to a leaf of a plant in a young-leaf stage at least once. Preferably, the plant vitalizer is given to a leaf of a plant in a young-leaf stage within two weeks after the completion of foliation at least once. Preferably, the exogenous elicitor is a chitinoligosaccharide and the endogenous elicitor is at least one oligosaccharide selected from a cellooligosaccharide and a xylooligosaccharide.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Plant yields decrease due to abiotic stresses such as sunlight duration, temperature, and rainfall, as well as biotic stresses such as pests and diseases. For example, in the case of fruit trees, the optimal average annual temperature varies depending on the type of fruit tree, but they generally prefer abundant sunlight and well-drained soil. Heavy rainfall and prolonged overly humid conditions can lead to adverse effects such as poor root growth and increased susceptibility to pests and diseases. Furthermore, small temperature differences during the day can have a significant impact on quality, such as preventing fruit sugar content from increasing. To date, various fertilizers and pesticides have been used to increase crop yields, particularly in agricultural crops. Fertilizers are a source of nutrients necessary for plant growth, but they do not have the function of alleviating stress. Pesticides directly eliminate pests that parasitize plants and eliminate biological stress, but even though their safety has been fully confirmed, there are concerns about the effects of excessive consumption on the human body and the environment, and there is also concern that pesticides and other chemicals manufactured by chemical synthesis may remain in the soil for long periods of time once sprayed, so it has been desirable to develop resistance to biological stress using other methods, if possible.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 regulate 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 suitable for fruit trees 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 methods for applying plant activators to fruit tree cultivation. As a result, they have found that applying a plant activator containing an exogenous elicitor and an endogenous elicitor to young leaves of fruit trees significantly improves the yield and quality of the harvested product, which led to the completion of the present invention.

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

[20] . [1] A method for cultivating fruit trees, comprising applying a plant stimulant containing an exogenous elicitor and an endogenous elicitor to leaves at least once in the young leaf stage. [2] The method for cultivating fruit trees described in [1], which comprises applying the plant vitality agent at least once to leaves in the young leaf stage up to two weeks after the completion of leaf expansion. [3] The method for cultivating a fruit tree according to [1] or [2], further comprising applying the plant vitality agent at least once to leaves after the young leaf stage. [4] A method for cultivating a fruit tree according to any one of [1] to [3], wherein the exogenous elicitor is a chitin oligosaccharide and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides. [5] The method for cultivating a fruit tree according to any one of [1] to [4], wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5. [6] The method for cultivating a fruit tree according to any one of [1] to [5], wherein the endogenous elicitor comprises xylooligosaccharide. [7] The method for cultivating fruit trees according to [6], wherein the endogenous elicitor contains both cellooligosaccharides and xylooligosaccharides. [8] The method for cultivating fruit trees according to [7], wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant vitalizer is 0.2 to 5. [9] The method for cultivating fruit trees described in any one of [1] to [8], wherein the plant vitalizer 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.

[10] The method for cultivating a fruit tree according to any one of [1] to [9], wherein the fruit tree is at least one species selected from the group consisting of Rutaceae, Vitaceae, and Rosaceae.

[11] A plant activator containing an exogenous elicitor and an endogenous elicitor, which is used in the cultivation of fruit trees and is applied at least once to leaves in the young leaf stage.

[12] The plant vitalizer according to

[11] , which is applied at least once to leaves in the young leaf stage up to two weeks after leaf emergence is complete.

[13] The plant vitalizer according to

[11] or

[12] , which is further applied at least once to leaves after the young leaf stage.

[14] The plant activator according to any one of

[11] to

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

[15] The plant activator according to any one of

[11] to

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

[16] The plant activator according to any one of

[11] to

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

[17] The plant activator according to

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

[18] The plant activator according to

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

[19] The plant activator according to any one of

[11] to

[18] , 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.

[20] The plant activator according to any one of

[11] to

[19] , wherein the fruit tree is at least one species selected from the group consisting of Rutaceae, Vitaceae, and Rosaceae. [Effects of the Invention]

[0009] The method for cultivating fruit trees of the present invention can improve the yield and quality of harvested products by applying a plant activator containing an exogenous elicitor and an endogenous elicitor to the leaves of fruit trees in the young leaf stage. 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 method for cultivating fruit trees of this embodiment includes applying a plant activator containing an exogenous elicitor and an endogenous elicitor to young leaves of fruit trees. 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 vitalizer used in the fruit tree 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 fruit tree 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 fruit tree 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 fruit tree cultivation method of this embodiment is preferably in a liquid form for easy application. When a liquid plant activator is used, the active ingredient concentration in the plant activator when sprayed onto 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 spray concentration is 0.1 ppm by mass or more, the effect of the plant activator is efficiently exerted. When the spray concentration is 500 ppm by mass or less, disease resistance can be exerted 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] [Fruit tree] The type of fruit tree cultivated by the cultivation method of this embodiment is not particularly limited, but examples include plants of the Rutaceae, Rosaceae, Vitaceae, Ebenaceae, Moraceae, Ericaceae, and Actinidiaceae families. Specific examples include plants from the Rutaceae family, such as mandarins, oranges, lemons, and grapefruits; the Rosaceae family, such as peaches, apricots, plums, cherries, pears, loquats, and apples; the Vitaceae family, such as grapes; the Ebenaceae family, such as persimmons; the Moraceae family, such as figs; the Ericaceae family, such as blueberries; and the Actinidiaceae family, such as kiwifruit. Among these, Rutaceae plants such as mandarin oranges, oranges, and grapefruits, Rosaceae plants such as peaches and apples, and Vitaceae plants such as grapes are preferred, with Rutaceae plants being more preferred.

[0028] [Cultivation method] There are no particular limitations on the cultivation method for fruit trees, but examples include outdoor cultivation, greenhouse cultivation, etc. In fruit tree cultivation, soil management and fruit tree management are important to ensure high quality fruit and yield.

[0029] The soil management includes watering, fertilizing, weeding, etc., and the fruit tree management includes pruning, bud removal, top pinching, fruit thinning, etc., as well as spraying chemicals for disease and pest control, etc. The methods for soil management and fruit tree management vary depending on the fruit tree in question, and may be carried out in accordance with conventional farming methods.

[0030] The method for cultivating fruit trees of this embodiment includes applying the plant vitalizer to leaves in the young leaf stage. In this specification, for both deciduous and evergreen fruit trees, the period from the time when the first leaf has fully expanded from a leaf bud to three weeks after the first leaf has expanded is referred to as the "young leaf stage" of the leaf bud. In this specification, leaves in the young leaf stage may also be referred to as "young leaves."

[0031] In one embodiment, the plant vitalizer is applied at least once to leaves in the young leaf stage (young leaves). In order to harvest sufficient high-quality fruits, it is preferable to apply it to young leaves two to three times at intervals of one week or more. The timing of application is preferably at least once to young leaves within two weeks after completion of leaf expansion, more preferably at least once to young leaves within one week after completion of leaf expansion, and even more preferably at least once to young leaves within one week after completion of leaf expansion and once around two weeks after completion of leaf expansion. Note that the timing of leaf expansion of each leaf bud varies among all fruit trees. For example, the time when 70% of the leaf buds on a single fruit tree have completed leaf expansion may be considered to be the time when leaf expansion of that fruit tree is complete, and foliar spraying may be performed on the entire fruit tree at the above frequency.

[0032] In another embodiment of the fruit tree cultivation method of the present embodiment, it is preferable to further apply the plant vitalizer to leaves after the young leaf stage. In this specification, "leaves after the young leaf stage" refers to leaves after the "young leaf stage."

[0033] In order to obtain fuller fruits, it is preferable to apply the plant vitalizer at least once to leaves in the young leaf stage and at least once to leaves after the young leaf stage.

[0034] In one embodiment, it is more preferable to apply the plant vitalizer to leaves after the young leaf stage periodically at intervals of at least one week. The timing of application to leaves after the young leaf stage is preferably at least once on leaves during the period from after fruiting to fruit coloring, more preferably at least once on leaves during the period from after fruiting to fruit thickening, and even more preferably at least once on leaves during the period from after fruiting to just before fruit thickening. It is more preferable to apply the plant vitalizer at least once during any two of the period from after fruiting to just before fruit thickening, the fruit thickening, and the fruit coloring, and even more preferably at least once during all three periods. In any case, it is preferable to apply the plant vitalizer at intervals of at least one week.

[0035] (Application of plant vitalizers) The plant vitalizer is applied to fruit trees by foliar spraying. Foliar spraying is preferred for effectively expressing elicitor activity. Foliar spraying can be carried out by methods conventional in the art, such as a power sprayer, a shoulder sprayer, a broadcaster, a sprayer, a manned or unmanned helicopter, a fogger, or a hand sprayer. In addition to foliar spraying, the plant vitalizer may be applied to fruit trees by other methods. For example, it may be sprayed directly on the soil, or it may be incorporated into fertilizer and then sprayed on the soil. When incorporated into fertilizer, the type of fertilizer is not limited, and may include chemical fertilizers containing nitrogen, phosphorus, and potassium, as well as organic fertilizers such as oil cakes, fish cakes, bone meal, seaweed powder, amino acids, sugars, and vitamins.

[0036] 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. 2It 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.

[0037] (Effects of plant vitalizers) The fruit tree cultivation method of this embodiment involves applying a plant activator containing an exogenous elicitor and an endogenous elicitor to the leaves of the fruit tree in the young leaf stage. It is also preferable to subsequently apply the plant activator containing an exogenous elicitor and an endogenous elicitor to the leaves of the fruit tree after the young leaf 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 the plant, but excessive application is thought to cause growth inhibition. On the other hand, applying an endogenous elicitor (e.g., derived from cellooligosaccharides or xylooligosaccharides) is expected to enable the plant to recognize its own cellular damage and disruptive components (DAMPs: damage-associated molecular patterns) and promote its own growth in order to acquire immunity and repair cells. In the fruit tree cultivation method of this embodiment, it is believed that by applying a plant activator containing an exogenous elicitor and an endogenous elicitor, particularly to leaves in the young leaf stage, it is possible to cultivate strong fruit trees that are endowed with disease resistance while suppressing growth inhibition. By subsequently using a plant activator on strong plants cultivated in this manner, it is believed that the growth-promoting effect of the endogenous elicitor can be utilized without being strongly affected by the growth-inhibiting effect of the exogenous elicitor, ultimately achieving a high growth effect through the complementary action of the two. Therefore, in cultivating fruit trees, it is believed that applying the plant activator at least once to leaves in the young leaf stage and at least once to leaves after the young leaf stage will result in strong plant growth and improved yield and quality of the harvest.

[0038] The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited thereto. [Example]

[0039] 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.

[0040] (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.

[0041] (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.

[0042] [2. Fruit Tree 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 25 and Comparative Examples 1 to 13 in Tables 1 to 3. 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 tables is expressed as % by mass.

[0043] (2) Cultivation Test 1 (Satsuma mandarin oranges) (Examples 1 to 13, Comparative Examples 1 to 5) The experiment was conducted using outdoor-grown Satsuma mandarins. Four trees per plot were planted, and conventional farming methods were used, including irrigation, fertilization, pruning, and fruit thinning, as well as soil and tree management. Buds sprouted sequentially in early April, and the time when approximately 70% of the leaf buds had fully expanded was considered to be the time of complete leaf expansion. A diluted solution of the plant vitalizer was sprayed on the young leaves under the conditions listed in Table 1, until the leaf surface was moist. Aqueous solutions (diluted plant vitalizer solutions) adjusted to the active ingredient concentration of the plant vitalizer for each condition were prepared at 2.0 kg per plot, and foliar spraying using a sprayer was carried out from the completion of leaf expansion until the fruit coloring period as shown in Table 1. Fruit yield and sugar content of four fruit trees (per plot) were then measured and compared under each condition. In Table 1, "After the young leaf stage (3 times)" indicates that the product was sprayed three times in total: once after fruiting and before the thickening period, once during the thickening period, and once during the coloring period. The yield was expressed as a percentage of the yield obtained under cultivation conditions where the plant vitalizer was not sprayed (Comparative Example 1), which was set at 100. Brix was calculated by randomly selecting five fruits from each tree and averaging the measurements for a total of 20 fruits. The test results are shown in Table 1.

[0044] [Table 1]

[0045] (3) Cultivation Test 2 (Grape) (Examples 14 to 19, Comparative Examples 6 to 9) The experiment was conducted using greenhouse-grown grapes (Delaware). Two trees per plot were used, and conventional farming methods were used, including irrigation, fertilization, pruning, fruit thinning, and hormone (gibberellin) treatment, as well as soil and tree management. Germination occurred sequentially in early April, and the time when approximately 70% of the leaf buds had fully expanded was considered to be the time of complete leaf expansion. A diluted solution of the plant vitalizer was sprayed on the young leaves under the conditions listed in Table 2, until the leaf surface was moist. Aqueous solutions (diluted plant vitalizer solutions) adjusted to the active ingredient concentration for each condition were prepared at 1.5 kg per plot, and foliar spraying using a sprayer was performed from the time leaf expansion was complete until the fruit coloring period, as shown in Table 2. Fruit yield and sugar content of two fruit trees (one plot) were then measured and compared under each condition. In Table 2, "After the young leaf stage (three times)" indicates that the product was sprayed three times: once after fruiting and before the thickening period, once during the thickening period, and once during the coloring period. The yield is expressed as a percentage of the yield under cultivation conditions where the plant vitalizer was not sprayed (Comparative Example 6), which is set at 100. Brix was calculated by randomly selecting five bunches of fruit from each tree and averaging the measurements of the kernels at the bottom of the bunch for a total of 10 bunches. The test results are shown in Table 2.

[0046] [Table 2]

[0047] (4) Cultivation Test 3 (Peach) (Examples 20 to 25, Comparative Examples 10 to 13) A test was conducted using peach (Hakuho) grown outdoors. Four trees per plot were used, and conventional farming methods were used, including irrigation, fertilization, pruning, and fruit thinning, as well as soil and tree management. Flowering occurred in late March, followed by sequential germination in early April. After this, the time when approximately 70% of the leaf buds had fully expanded was considered complete, and a diluted solution of the plant vitalizer was sprayed on the young leaves, using the conditions listed in Table 3, until the leaf surface was moist. Aqueous solutions (diluted plant vitalizer solutions) adjusted to the active ingredient concentration of the plant vitalizer for each condition were prepared at 2.0 kg per plot, and foliar spraying using a sprayer was carried out from the time leaf expansion was complete until the fruit coloring period, as shown in Table 3. Fruit yield and sugar content were then measured for four fruit trees (per plot), and the results were compared under each condition. In Table 3, "After the young leaf stage (twice)" indicates that the product was sprayed twice, once during the thickening period and once during the coloring period. The yield was expressed as a percentage of the yield obtained under cultivation conditions where the plant vitalizer was not sprayed (Comparative Example 10), which was set at 100. Brix was calculated by randomly selecting five fruits from each tree and averaging the measurements for a total of 20 fruits. The test results are shown in Table 3.

[0048] [Table 3]

[0049] From the results of Tables 1 to 3, it was confirmed that in fruit tree cultivation, the use of a plant activator containing both exogenous and endogenous elicitors on young leaves significantly improved the yield. Furthermore, in the examples, it was confirmed that the sugar content of the harvested fruit was high, and that good quality fruit was obtained.

Claims

1. A method for cultivating fruit trees, comprising applying a plant vitalizer containing an exogenous elicitor and an endogenous elicitor to leaves in the young leaf stage 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 fruit trees according to claim 1, comprising applying the plant vitalizer at least once to leaves in the young leaf stage up to two weeks after completion of leaf emergence.

3. 3. The method for cultivating fruit trees according to claim 1 or 2, further comprising applying the plant vitalizer at least once to leaves after the young leaf stage.

4. The method for cultivating fruit trees according to any one of claims 1 to 3, wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5.

5. The method for cultivating fruit trees according to any one of claims 1 to 4, wherein the endogenous elicitor comprises a xylooligosaccharide.

6. The method for cultivating fruit trees according to claim 5 , wherein the endogenous elicitor comprises both cellooligosaccharides and xylooligosaccharides.

7. 7. The method for cultivating fruit trees according to claim 6, wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant vitalizer is 0.2 to 5.

8. The method for cultivating a fruit tree according to any one of claims 1 to 7, 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.

9. The method for cultivating fruit trees according to any one of claims 1 to 8, wherein the fruit trees are at least one species selected from the group consisting of Rutaceae, Vitaceae, and Rosaceae.

10. A plant activator containing an exogenous elicitor and an endogenous elicitor for use in the cultivation of fruit trees, wherein the plant activator is applied at least once to leaves in the young leaf stage, and the exogenous elicitor is a chitin oligosaccharide and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides.

11. The plant vitalizer according to claim 10, which is applied at least once to leaves in the young leaf stage up to two weeks after completion of leaf emergence.

12. The plant vitalizer according to claim 10 or 11, which is further applied at least once to leaves after the young leaf stage.

13. The plant activator according to any one of claims 10 to 12, wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant activator is 0.1 to 5.

14. The plant activator according to any one of claims 10 to 13, comprising a xylooligosaccharide as the endogenous elicitor.

15. The plant activator according to claim 14, comprising both cellooligosaccharides and xylooligosaccharides as the endogenous elicitor.

16. The plant activator according to claim 15, wherein the mass ratio of the cellooligosaccharides to the xylooligosaccharides in the plant activator is 0.2 to 5.

17. The plant activator according to any one of claims 10 to 16, wherein the plant activator 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.

18. The plant activator according to any one of claims 10 to 17, wherein the fruit tree is at least one species selected from the group consisting of Rutaceae, Vitaceae, and Rosaceae.

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