Methods for cultivating cassava and plant stimulants for cassava cultivation

Abstract

To provide a method for improving the yield of cassava harvests.SOLUTION: A method for cultivating cassava includes giving a plant vitalizer containing exogenous elicitor and endogenous elicitor to a young seedling at least once.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for cultivating cassava using exogenous elicitors and endogenous elicitors, and a plant vitality agent for cultivating cassava.

Background Art

[0002] Plant yields are reduced by 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 cassava, it prefers abundant sunlight and well-drained land, and the cultivation temperature is 20 to 40 °C, and the temperature must be at least 15 °C or higher. If it is below this range, growth will be poor. Also, under overly wet conditions, there are drawbacks such as an increased likelihood of disease occurrence. In particular, in order to increase the yields of agricultural crops, various fertilizers and pesticides have been used so far. Fertilizers are nutrient sources required for plant growth but do not have the function of alleviating stress. Pesticides directly control pests parasitic on plants and eliminate biotic stress. However, when using pesticides, although safety has been sufficiently confirmed, there are concerns about the effects on the human body and the environment due to excessive ingestion. In particular, drugs such as pesticides manufactured by chemical synthesis methods may remain in the soil, etc. for a long time once sprayed, and it has been desired to confer resistance to biotic stress by other methods if possible. Therefore, in recent years, in addition to these, the use of biostimulants as substances safe for both the human body and the environment has attracted attention.

[0003] "Biostimulants," also known as "biostimulants" or "plant stimulants," are substances containing various groups of materials and microorganisms that, when applied to plants or their root systems, stimulate a series of processes that occur naturally within the plant, thereby improving nutrient absorption, increasing fertilization efficiency, conferring stress tolerance, and improving quality. They do not have a direct effect on pests or diseases, and therefore are not classified as any insecticide or fungicide. In other words, they are naturally occurring components (including microorganisms) that are not plant hormones or nutrients, but even in very small amounts, stimulate plant vitality and promote growth. It is believed that applying biostimulants to plants increases nutrient absorption and utilization, promotes growth, and improves crop yield and quality. Agricultural biostimulants include a variety of formulations such as compounds, materials, and other products applied to plants or soil to control and enhance the physiological processes of crops. Biostimulants act on plant physiology through pathways different from those of nutrients to improve crop vitality, yield, quality, and post-harvest shelf life. In this way, biostimulants can stimulate the inherent 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: a plant vitality agent combining chitin oligosaccharides and chitosan having antibacterial activity (Patent Document 1), a plant vitality agent containing oligosaccharides and plant extracts in vinegar (Patent Document 2), a plant growth promoter containing cellulose (Patent Document 3), a plant growth regulator containing hexofuranose derivatives (Patent Document 4), a method for improving plant disease resistance using low-molecular-weight chitin or chitosan (Patent Document 5), and a fertilizer containing chitin and / or chitosan (Patent Document 6). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-143013 [Patent Document 2] Japanese Patent Publication No. 2001-64112 [Patent Document 3] Japanese Patent Publication No. 2002-114610 [Patent Document 4] Japanese Patent Publication No. 2013-151438 [Patent Document 5] Japanese Patent Publication No. 2015-48436 [Patent Document 6] Japanese Patent Publication No. 2017-95352 [Patent Document 7] International Publication No. 2017 / 104687 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, in plant cultivation, there has been no prior research into adjusting the method of applying plant stimulants according to the plant species to enhance their effectiveness. In particular, the appropriate method of applying plant stimulants to cassava was unknown. [Means for solving the problem]

[0007] This invention was made in view of the above circumstances, and in diligent research was conducted on how to apply plant vitality enhancers in cassava cultivation. As a result, it was found that applying a plant vitality enhancer containing exogenous and endothelial enhancers to cassava seedlings significantly improves the yield of harvested produce, leading to the completion of this invention.

[0008] In other words, the present invention encompasses the following [1] to

[20] . [1] A method for cultivating cassava, comprising applying a plant stimulant containing exogenous and endogenous elicitors to seedlings at least once. [2] The method for cultivating cassava according to [1], comprising giving the plant vitality agent at least once to seedlings 2 to 15 days after germination. [3] The method for cultivating cassava according to [1] or [2], further comprising applying the plant vitality agent to the plant at least once after the seedling stage. [4] A method for cultivating cassava 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 cassava according to any one of [1] to [4], wherein the mass ratio of the exogenous elicitor to the endogenous elicitor in the plant vitality agent is 0.1 to 5. [6] A method for cultivating cassava according to any one of [1] to [5], comprising xylooligosaccharide as the endogenous elicitor. [7] The method for cultivating cassava according to [6], comprising both cellooligosaccharides and xylooligosaccharides as the endogenous elicitors. [8] The method for cultivating cassava according to [7], wherein the mass ratio of cellooligosaccharide to xylooligosaccharide in the plant vitality agent is 0.2 to 5. [9] The method for cultivating cassava according to any one of [1] to [8], wherein the plant vitality agent 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.

[10] The method for cultivating cassava according to any one of [1] to [9], wherein the plant vitality agent is applied to the plant by foliar spraying.

[11] A plant stimulant for use in the cultivation of cassava, comprising an exogenous elicitor and an endogenous elicitor, which is applied to seedlings at least once.

[12] The plant stimulant described in

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

[13] The plant vitality agent according to

[11] or

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

[14] The plant vitality agent 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 vigor agent according to any one of

[11] to

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

[16] The plant vigor agent according to any one of

[11] to

[15] , which contains xylo-oligosaccharide as the endogenous elicitor.

[17] The plant vigor agent according to

[16] , which contains both cello-oligosaccharide and xylo-oligosaccharide as the endogenous elicitor.

[18] The plant vigor agent according to

[17] , wherein the mass ratio of the cello-oligosaccharide to the xylo-oligosaccharide in the plant vigor agent is 0.2 to 5.

[19] The plant vigor agent 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 mass ppm.

[20] The plant vigor agent according to any one of

[11] to

[19] , which is applied to a plant by foliar spraying.

Advantages of the Invention

[0009] The cassava cultivation method of the present invention can improve the yield of the harvested product by applying a plant vigor agent containing an exogenous elicitor and an endogenous elicitor to the cassava seedlings.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described. The embodiments described below show typical examples of the present invention and are not limited thereto.

[0011] The cassava cultivation method of the present embodiment includes applying a plant vigor agent containing an exogenous elicitor and an endogenous elicitor to the cassava seedlings. The "plant vigor agent" includes not only those having a relaxing effect on abiotic stresses such as temperature, light, water, and salts related to plant growth, but also those having a relaxing effect on biotic stresses such as pests and diseases.

[0012] An elicitor is a general term for substances that induce a biological defense response in tissues or cultured cells of higher plants, and induces disease resistance in the plant immune system. Plants sense elicitors with receptors present on the leaf surface, etc., and activate a pathogen resistance response. As a result, a biological defense action (immunity) in which various compounds are secreted occurs against various pathogens. When an elicitor acts on a plant, defense responses such as the synthesis and accumulation of phytoalexins and infection-specific proteins, the generation of reactive oxygen species, the generation of reactive nitrogen species, hypersensitive cell death, and changes in gene expression are induced, and it is thought that the plant protects itself from pathogens and enhances disease tolerance through these reactions. Phytoalexins are antibacterial compounds synthesized and accumulated in plants by the action of elicitors, and the antibacterial compounds produced vary for each plant species. Representative phytoalexins include flavonoids, terpenoids, fatty acid derivatives, etc. Reactive oxygen species have the effect of killing pathogenic microorganisms, and further, reactive oxygen species and reactive nitrogen species function as signals that activate various defense responses alone or in cooperation. Such disease resistance due to the elicitor effect is expected to be used in agriculture because it enhances resistance to a wide range of diseases.

[0013] [Exogenous elicitor] In this specification, "exogenous elicitor" means an elicitor of a substance derived from an organism other than a plant, for example, a component derived from a fungus, an insect, or a crustacean, and is not particularly limited as long as it has an elicitor effect, but typically, it is chitin, chitosan, and their oligosaccharides, various biomolecules derived from insects, etc. The plant vigor agent used in the cultivation method of cassava of this embodiment preferably contains chitosan oligosaccharide as an exogenous elicitor.

[0014] Chitosan oligosaccharide contains partially deacetylated chitosan oligosaccharide, and is an oligosaccharide in which several N-acetylglucosamines are linked together. Generally, it is obtained by hydrolyzing chitin derived from crustaceans, etc., and is also called oligo-N-acetylglucosamine. In other words, chitin oligosaccharides are obtained by chemically or enzymatically partially hydrolyzing chitin, which is prepared by conventional methods from the shells of crustaceans such as crabs and shrimp. Preferably, one or more of the following chitin oligosaccharides are used: N-acetylchitobiose, N-acetylchitotriose, N-acetylchitotetraose, N-acetylchitopentaose, N-acetylchitohexaose, N-acetylchitoheptaose, N-acetylchitooctaose, etc. Among these, N-acetylchitopentaose, N-acetylchitohexaose, and N-acetylchitoheptaose have particularly high elicitor effects.

[0015] In this embodiment, the chitin oligosaccharide used is particularly preferably one having the following chemical structure. [ka] Note that this also includes cases where some of the acetyl groups (-COCH3) in the formula have been removed, with -NHCOCH3 becoming -NH2.

[0016] [Endogenous Elicitor] In this specification, "endogenous elicitor" means an elicitor of plant origin, and is not particularly limited as long as it has an elicitor effect, but typically includes cellulose, xylan and their oligosaccharides produced from plants. The plant vitality agent used in the cassava cultivation method of this embodiment preferably contains at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides as an endogenous elicitor.

[0017] Cello-oligosaccharides are short sugars in which multiple glucose molecules are polymerized by β-glycosidic bonds. In recent years, functionalities such as moisturizing properties, anti-stickiness, flavor enhancement, starch retrogradation reduction, and protein denaturation inhibition have been discovered, and their use in the pharmaceutical, cosmetic, food, and animal feed fields is expected. In particular, cello-oligosaccharides with a degree of polymerization of glucose of 3 or higher are attracting even greater attention in terms of increased functionality and the conferral of new functionalities. Cello-oligosaccharides currently used industrially are produced by enzymatic reactions, but their main components are glucose and the dimer cellobiose, and they contain almost no oligomers of the trimer cellotriose or higher. However, in recent years, the applicants have reported a method for producing cello-oligosaccharides containing oligomers with a degree of polymerization of glucose of 3 to 6 by controlling the heating rate, cooling rate, reaction temperature, and reaction time to induce a hydrothermal reaction in a hydrolysis reaction of plant biomass using a carbon catalyst (Patent Document 7).

[0018] In this embodiment, the cellooligosaccharide used is particularly preferably one having the following chemical structure. [ka]

[0019] Xylooligosaccharides are short sugars in which several xylose molecules are polymerized by β-glycosidic bonds. They are generally obtained by hydrolysis of xylan, the main component of hemicellulose, and are mainly sold for food applications.

[0020] In this embodiment, xylooligosaccharides having the following chemical structure are particularly preferred. [ka]

[0021] [Plant vitality enhancer] The plant stimulant used in the cassava 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 stimulant (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 stimulant more preferably contains xylooligosaccharides as endogenous elicitors, and optimally contains both cellooligosaccharides and xylooligosaccharides. The mass ratio of cellooligosaccharides to xylooligosaccharides in the plant stimulant (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 a plant vitality enhancer contains chitin oligosaccharide as an exogenous elicitor and both cellooligosaccharide and xylooligosaccharide as an endogenous elicitor, it is preferable that the proportion of each oligosaccharide to the total content of chitin oligosaccharide, cellooligosaccharide, and xylooligosaccharide is 10-50% by mass for chitin oligosaccharide, 10-50% by mass for cellooligosaccharide, and 10-60% by mass for xylooligosaccharide. More preferably, the proportion of each oligosaccharide is 20-40% by mass for chitin oligosaccharide, 20-40% by mass for cellooligosaccharide, and 20-55% by mass for xylooligosaccharide.

[0024] The plant stimulant may further contain other components besides the active ingredients, which are the exogenous and endogenous elicitors, such as preservatives, spreading agents, anti-precipitation agents, thickeners, excipients, and solvents. Examples of preservatives include potassium sorbate, para-hydroxybenzoic acid esters, benzoic acid, sodium dehydroacetate, hinokitiol, phenoxyethanol, polyaminopropyl biguanide, and polylysine. The spreading agent is a viscous liquid mainly composed of a surfactant and is not particularly limited as long as it can be used as a spreading agent for the plant stimulant, but examples include polyoxyethylene nonylphenyl ether, sorbitan fatty acid ester, and polyoxyethylene hexitane fatty acid ester. Examples of anti-precipitation agents include polyphosphate or salts of polyphosphate, or polycarboxylic acid-type polymer surfactants. Examples of thickeners include water-soluble polymers such as carboxymethylcellulose (CMC), polyacrylamide, and starch, or molasses, alcohol fermentation concentrate wastewater, and amino acid fermentation concentrate wastewater. Excipients include lactose and starch. Solvents are used to dilute the active ingredient to an appropriate concentration and to facilitate application to plants. Water is preferred as the solvent.

[0025] The plant stimulant used in the cassava cultivation method of this embodiment may be in powder, granular, or liquid form, but is generally preferred to be in liquid form for easier application. When using a liquid plant stimulant, the concentration of the active ingredient in the stimulant at the time of application to the plant 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 concentration of the active ingredient in the plant stimulant refers to the total content of exogenous and endogenous elicitors in the plant stimulant. When the application concentration is 0.1 ppm by mass or higher, the effect of the plant stimulant is efficiently expressed. When the application concentration is 500 ppm by mass or lower, disease resistance can be expressed without inhibiting plant growth.

[0026] While commercially available plant stimulants with pre-adjusted active ingredient concentrations may be used, typically, a concentrated plant stimulant solution containing high concentrations of exogenous and endogenous elicitors is diluted with water before use. When the concentrated plant stimulant solution is diluted (for example, 1000 times), the total content of exogenous and endogenous elicitors in the concentrated 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] [Cassava] The types of cassava cultivated by the cultivation method of this embodiment include bitter varieties, sweet varieties, and other varieties, and are not particularly limited.

[0028] [Cultivation method] There are no particular restrictions on the cultivation method of cassava, and methods such as sowing seeds and propagation by cuttings are possible, but propagation by cuttings is preferred.

[0029] For example, in the case of propagation by cuttings, the following methods can be used. It is preferable to select a field in the subtropical or tropical region with an average temperature of 20-35°C and that is not excessively wet, and to plant around March to May. One week before planting, apply a moderate amount of base fertilizer (30-50% of the prescribed amount) to the field, deep plow it, and create ridges. Since drainage is important for cassava cultivation, it is preferable to make the ridges higher, at 20-30 cm. The ridge width should be 80-100 cm, and the spacing between ridges should be about 90-120 cm. Cut the stems for cuttings to about 8-15 cm, plant them in holes dug about 80-120 cm apart and 8-15 cm deep, cover with soil, and lightly press down. Germination will occur in about a week after planting, but it is preferable to manage the plants until harvest by following conventional farming methods, including additional fertilization, hilling, and irrigation. Nine to eleven months after planting, the plants are pulled up and the tubers at the base are harvested.

[0030] The method for cultivating cassava according to this embodiment includes applying the plant vitality agent to seedlings. In this specification, "seedlings" of cassava refers to seedlings from germination to three weeks old.

[0031] In one embodiment, it is preferable to use the plant vitality agent at least once on seedlings 2 to 15 days after germination. It is more preferable to use the plant vitality agent at least once on seedlings 2 to 10 days after germination, and even more preferable to use the plant vitality agent at least once on seedlings 2 to 5 days after germination. To obtain more robust seedlings, it is particularly preferable to use the plant vitality agent at least once on seedlings 2 to 15 days after germination, and then at least once every 5 to 10 days thereafter.

[0032] In another embodiment of the cassava cultivation method of this embodiment, it is preferable to further apply the plant vitality agent to the plant after the seedling stage. In this specification, "plant after the seedling stage" of cassava refers to the plant after the seedling stage, that is, the plant three weeks after germination.

[0033] In one embodiment, it is preferable to use the plant stimulant at least once on the plant after the seedling stage. It is more preferable to use it 5 to 12 times at a rate of once every 2 to 4 weeks until about 8 months after planting.

[0034] (Application of plant stimulants) The application of the plant stimulant to cassava can be carried out by methods customary in this industry, and the application method is not particularly limited. For example, it may be applied directly to the leaves and stems of the plant, applied to the culture medium or soil in which the plant is grown, or mixed with fertilizer and applied to the culture medium or soil. When mixed with fertilizer, the type of fertilizer is not limited and can be any chemical fertilizer containing nitrogen, phosphorus, and potassium, or organic fertilizer such as oil cake, fish meal, bone meal, seaweed powder, amino acids, sugars, and vitamins. As for the application method, foliar application is particularly preferable for effectively expressing the elicitor activity. Foliar application can be carried out by methods customary in this industry, such as power sprayers, shoulder sprayers, broadcasters, sprayers, manned or unmanned helicopters, fogging devices, and hand sprayers.

[0035] The amount of plant stimulant to spray is 1 cm on the leaf surface. 2 Preferably, the amount of active ingredient sprayed per unit area is 0.1 ng to 100 ng, and the amount per 1 cm of leaf surface. 2 It is more preferable that the amount of active ingredient applied per unit area is 1 ng to 20 ng. In actual fields, it is difficult to selectively apply only to the leaf surface and to ensure that all of the applied substance adheres to the leaf surface, so for a cultivated area of ​​100 m² 2 It is preferable to dilute 0.01g to 20g of the active ingredient per plant so that the concentration in the plant stimulant is 1 ppm to 100 ppm by mass, and then evenly spray it over the plant. More preferably, for a cultivated area of ​​100m² 2 It is preferable to dilute 0.1g to 10g of the active ingredient per serving so that the concentration in the plant stimulant is between 10 ppm by mass and 500 ppm by mass.

[0036] In the cassava cultivation method of this embodiment, soil management is preferably carried out using conventional farming methods.

[0037] (Effects of plant stimulants) The cassava cultivation method of this embodiment includes providing a plant stimulant containing exogenous and endogenous elicitors to cassava seedlings. It is also preferable to continue providing the plant stimulant containing exogenous and endogenous elicitors to the plant after the seedling stage. The reason why providing a plant stimulant with this configuration at this stage is effective is not yet fully understood. By providing exogenous elicitors (e.g., derived from chitin oligosaccharides), the plant is given resistance to herbivore-derived diseases, etc., but it is thought that excessive action may cause growth inhibition. On the other hand, by providing endogenous elicitors (e.g., derived from cellooligosaccharides, xylooligosaccharides), the plant is expected to recognize its own cell damage and disruption components (DAMPs: damage-associated molecular patterns), thereby promoting its own growth in order to acquire immunity and repair cells. In the cassava cultivation method of this embodiment, it is believed that by applying a plant vitality agent containing exogenous and endogenous elicitors, particularly during the early seedling stage, robust seedlings with disease resistance can be cultivated while suppressing growth inhibition. By subsequently applying the plant vitality agent to these strong plants, the growth-promoting effect of the endogenous elicitors can be utilized without being strongly affected by the growth-inhibiting effect of the exogenous elicitors, ultimately resulting in a high growth effect achieved through the complementary action of both. Therefore, it is estimated that applying the plant vitality agent at least once to seedlings and at least once to plants after the seedling stage will lead to strong plant growth and improved yields.

[0038] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto. [Examples]

[0039] [1. Prepare the oligosaccharides] (1) Chitin oligosaccharide 10 g of chitin powder (Wako Pure Chemical Industries, purified chitin) was dispersed in 30 mL of water containing 1.2 g of 85% phosphoric acid (Wako Pure Chemical Industries, special grade reagent). The powder was then dried under reduced pressure and placed in a 250 mL alumina pot along with 100 g of 5 mm diameter alumina balls. This pot was then set in a planetary ball mill (Fritsch, PULVERISETTE 6) and processed continuously at 500 rpm for 6 hours to obtain the reaction product. The reaction was started at room temperature, and the temperature rise due to shear heating was left to occur naturally. Next, the reaction mixture was suspended in water and neutralized with calcium hydroxide to obtain a slurry. This slurry was then filtered using 5B filter paper in a Nutsche filter, and the recovered filtrate was freeze-dried to obtain chitin oligosaccharide powder.

[0040] (2) Cellooligosaccharides 271g (1.8% moisture content, 266g dry weight) of cotton linter pulp (Tohoku Kosen Co., Ltd., 97% cellulose content) was mixed with 38g of 85% by mass phosphoric acid (special grade reagent, Fujifilm Wako Pure Chemical Industries, Ltd.) using a food blender (model: HBF500S, Hamilton Beach Corporation) to obtain 309g of reaction raw material (3.4% moisture content, 10.4% phosphoric acid content). Next, 309g of the reaction material was placed in a vibrating mill (device name: MB-1 type, manufactured by Chuo Kakoki Co., Ltd., pot size 5L) together with 13kg of φ3 / 4 inch carbon steel balls. A hydrolysis reaction was carried out by dry grinding for 24 hours under conditions of a total amplitude of 8mm, a vibration frequency of 16.2Hz, and a jacket flow water temperature of 75℃, after which the reaction powder was recovered. 10 g of this reaction powder and 90 g of deionized 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 cellulose hydrolysate. Next, 1.3 g of a 40% by mass aqueous calcium hydroxide solution was added to the extract, and the mixture was stirred using a magnetic stirrer at 25°C for 1 hour to prepare a neutralized solution. The supernatant was collected using a centrifuge, and then freeze-dried to obtain cellooligosaccharide powder.

[0041] (3) Xylooligosaccharides Acremonium Cellulolyticus The cus)TN strain (FERM P-18508) was cultured in a 500mL flask containing 100mL of liquid medium (Avicel 50g / L, KH2O4 24g / L, ammonium sulfate 5g / L, potassium tartrate 1 / 2H2O 4.7g / L, urea 4g / L, Tween80 1g / L, MgSO4·7H2O 1.2g / L, ZnSO4·7H2O 10mg / L, MnSO4·5H2O 10mg / L, CuSO4·5H2O 10mg / L) at 30°C for 6 days with shaking. 5g of corn cob powder was suspended in 50mL of the supernatant from the resulting culture solution and stirred at 50°C for 72 hours. The supernatant from the resulting reaction solution was freeze-dried to obtain xylooligosaccharide powder.

[0042] [2. Cultivating Cassava] (1) Preparation of plant vitality enhancers The oligosaccharides prepared in [1. Preparation of Oligosaccharides] were dissolved in water by stirring with a stirrer at their respective composition ratios so that the concentration of the active ingredient (mass ppm) in the plant stimulants shown in Examples 1-11 and Comparative Examples 1-5 in Table 1 was 1000 times greater. After dissolving, the mixture was sterilized using a 0.45 μm filter to obtain the plant stimulant stock solution. This stock solution was diluted 1000 times with water and used in the following cultivation tests. Hereafter, the plant stimulant after being diluted 1000 times may be referred to as "diluted plant stimulant solution". Note that the composition ratios of each oligosaccharide in the table are expressed in mass percent.

[0043] (2) Cultivation Test 1 (Examples 1-11, Comparative Examples 1-5) Cassava is cultivated in fields inside greenhouses, totaling 240m². 2 The experiment was conducted using the field. Two weeks before the planned planting date, the field was tilled and leaf mold was mixed in. In mid-March, ridges were made in the prepared field with a width of 80 cm, a spacing of 100 cm between ridges, and a height of 25 cm. Cassava (sweet variety) cuttings (approximately 10 cm long) were planted at 100 cm intervals to a depth of 10-12 cm. After covering with soil, the soil was lightly compacted and watered thoroughly, and germination occurred sequentially after 8-10 days. These were then divided into 20 plots of 5 plants each, and conventional farming methods were used. Diluted plant stimulant solution was sprayed onto the leaves and soil of germinated cassava seedlings and plants after the seedling stage, under the conditions described in Table 1, until the soil was moist. Aqueous solutions (diluted plant stimulant solutions) prepared to the appropriate concentration of the active ingredient for each plant stimulant were prepared at a rate of 1 kg / plot during the seedling stage and up to two months after planting, and at a rate of 2 kg / plot from three months after planting onward. Foliar application using a watering can and irrigation of the soil around the base of the plants were carried out as described in Table 1. Harvesting was performed 10 months after planting, and the average yield for each plot (5 plants) was measured and compared under each condition. The yield was measured by harvesting the edible tubers (potatoes) from the base of the plant and measuring the average weight per plant. The test results are shown in Table 1.

[0044] [Table 1]

[0045] [3. Cultivation of Brassicaceae plants (Examples 1-3)] We conducted experiments using komatsuna, a member of the Brassicaceae family. In a field tilled with compost, ridges were made with a row spacing of approximately 15-20 cm. Komatsuna (Inamura variety) seeds were sown in rows at intervals of 1-1.5 cm, lightly covered with soil, compacted, and then thoroughly watered. The germinated komatsuna were thinned as needed, and a diluted plant stimulant solution was sprayed on the leaves and soil until moist, under the conditions described in Table 2. Harvesting was carried out when the plants reached a height of 20-25 cm, and the harvest weight per plant was compared for 20 seedlings. The test results are shown in Table 2.

[0046] [Table 2]

[0047] Table 1 shows that in cassava cultivation, using a plant stimulant containing both exogenous and endogenous elicitors on young seedlings significantly improved yield. On the other hand, Table 2 shows that in the cultivation of komatsuna (Japanese mustard spinach), a Brassicaceae plant, using a plant stimulant containing both exogenous and endogenous elicitors on young seedlings in addition to the pre-harvest growth period did not result in a significant improvement in weight per plant.

Claims

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

2. The method for cultivating cassava according to claim 1, comprising giving the plant vitality agent at least once to seedlings 2 to 15 days after germination.

3. The method for cultivating cassava according to claim 1 or 2, further comprising applying the plant vitality agent to the plant at least once after the seedling stage.

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

5. A method for cultivating cassava according to any one of claims 1 to 4, wherein the endogenous elicitor is xylooligosaccharide.

6. The method for cultivating cassava according to claim 5, wherein the endogenous elicitor includes both cellooligosaccharides and xylooligosaccharides.

7. The method for cultivating cassava according to claim 6, wherein the mass ratio of cellooligosaccharide to xylooligosaccharide in the plant vitality agent is 0.2 to 5.

8. A method for cultivating cassava according to any one of claims 1 to 7, wherein the plant vitality agent is given 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. A method for cultivating cassava according to any one of claims 1 to 8, wherein the plant vitality agent is applied to the plant by foliar spraying.

10. A plant stimulant used in the cultivation of cassava, comprising an exogenous elicitor and an endogenous elicitor, wherein the plant stimulant is applied to seedlings at least once, the exogenous elicitor is a chitin oligosaccharide, and the endogenous elicitor is at least one oligosaccharide selected from cellooligosaccharides and xylooligosaccharides.

11. The plant vitality agent according to claim 10, which is applied at least once to seedlings 2 to 15 days after germination.

12. Furthermore, the plant vitality agent according to claim 10 or 11 is applied to the plant at least once after the seedling stage.

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

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

15. The plant vitality agent according to claim 14, comprising both cellooligosaccharide and xylooligosaccharide as the endogenous elicitor.

16. The plant stimulant according to claim 15, wherein the mass ratio of cellooligosaccharide to xylooligosaccharide in the plant stimulant is 0.2 to 5.

17. A plant vitality enhancer according to any one of claims 10 to 16, applied to plants 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. A plant stimulant according to any one of claims 10 to 17, which is applied to plants by foliar spraying.

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