Plant growth promoting components

Abstract

To provide a plant growth promoting composition that can promote plant growth more safely and inexpensively compared to conventional materials. [Solution] A plant growth promoting composition comprising one or more selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient.

Description

Technical Field

[0001] The present invention relates to a plant growth promoting composition and a plant growth promoting method.

Background Art

[0002] Currently, due to the explosive increase in population, producing sufficient amounts of food plants has become a global issue. In addition, desertification of land due to the reduction of green spaces and other factors is also a problem. Moreover, the rise in surface temperature based on the global warming phenomenon is also a problem, and the environmental problems in growing plants are increasing. That is, excessive stress based on global environmental factors in plants often causes problems in plant growth.

[0003] Therefore, there is a need for technology that promises more efficient harvesting. Biostimulants are attracting attention as new technologies that reduce damage to plants caused by climate and soil conditions by controlling environmental stress on plants and provide healthy plants.

[0004] Patent Document 1 discloses a plant stomatal opening promoter containing stevia, and it has been reported that artificial promotion of stomatal opening by stevia improves heat stress tolerance and the like. Patent Document 2 discloses a composition for activating genes that activate the ethylene and / or jasmonic acid signal transduction system, containing yeast cell wall degradation products. It has been reported that by applying yeast cell wall degradation products to plants, the expression of plant defensin genes involved in antibacterial properties and disease prevention of plants is activated. Patent Document 3 discloses a method for increasing the yield of cereals by inoculating cell wall-containing substances of methanol-assimilating bacteria into plants for cultivating cereals.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6741262 [Patent Document 2] Patent No. 4931388 [Patent Document 3] Japanese Patent Publication No. 2019-180361 [Overview of the project] [Problems that the invention aims to solve]

[0006] As mentioned above, various studies have been conducted to date using different materials to improve plant tolerance to environmental stress and increase yield, but there have been no reports of studies using sweet potato extract or sweet potato powder. [Means for solving the problem]

[0007] As a result of diligent research, the inventors of this invention discovered, using a uniquely developed high-precision screening method, that one or more materials selected from the group consisting of sweet potato extract and sweet potato powder can be effective ingredients for promoting plant growth, thus completing the present invention.

[0008] In other words, the present invention is as follows. [1] A plant growth promoting composition comprising one or more substances selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient. [2] The plant growth promoting composition according to [1], which has an effect of improving stress tolerance to one or more stresses selected from the group consisting of high temperature stress and drought stress. [3] The plant growth promoting composition according to [2], which activates response genes to one or more selected from the group consisting of high temperature stress and drought stress. [4] A method for promoting plant growth, comprising using a plant growth promoting composition containing one or more selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient, on a plant, in the soil in which the plant grows, or in a culture solution. [5] The plant growth promoting method according to [4], wherein the amount of the plant growth promoting composition used in the culture medium or diluent is 0.001 to 50% by mass or 0.001 to 50% by volume. [Effects of the Invention]

[0009] By applying a composition containing one or more selected from the group consisting of sweet potato extract and sweet potato powder of the present invention to plants, plant growth can be promoted more safely and inexpensively compared to conventional materials. [Brief explanation of the drawing]

[0010] [Figure 1] These images show the improvement in root development of rice plants when no sweet potato powder was added (left) and when 0.36 mg of a plant growth promoting composition containing sweet potato powder was added (right) (Example 1). [Figure 2] This graph shows the dry weight of rice roots when no sweet potato powder is added (left) and when 0.36 mg of a plant growth promoting composition containing sweet potato powder is added (right) (Example 1). [Figure 3] This graph shows the expression level of the high-temperature stress tolerance gene Os06g0716700 in the above-ground parts of plants when no sweet potato powder was added (left) and when 0.36 mg of a plant growth promoting composition containing sweet potato powder was added (right) (Example 2). [Figure 4] This graph shows the expression level of the high-temperature stress tolerance gene Os08g0500700 in the above-ground parts of plants when no sweet potato powder was added (left) and when 0.36 mg of a plant growth promoting composition containing sweet potato powder was added (right) (Example 2). [Figure 5] This graph shows the expression level of the high-temperature stress tolerance gene Os01g0165000 in the above-ground parts of plants when no sweet potato powder was added (left) and when 0.36 mg of a plant growth promoting composition containing sweet potato powder was added (right) (Example 2). [Figure 6]Graph showing the calculated water loss rate in the largest expanded leaf when no sweet potato powder was added (CT) and when 0.45 g or 0.90 g of the plant growth promoting composition containing sweet potato powder was added (right) (Example 3).

Mode for Carrying Out the Invention

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. The present invention is not limited to the present embodiment and can be variously modified and implemented within the scope of the gist thereof.

[0012] <Plant Growth Promoting Composition> The plant growth promoting composition in the present embodiment contains sweet potato extract or sweet potato powder as an active ingredient. Sweet potato (sweet potato variety) is a plant of the genus Ipomoea in the family Convolvulaceae. Specifically, Ipomoea batatas (L.) Lam. can be mentioned. The variety, production area, etc. of sweet potato are not particularly limited. For example, Yukikomachi, Amanadzuki, Akane Minori, Hoshi Akane, Churakana Sa, Konai Shin, Fukumurasaki, Murasaki Homare, Suzuhokkuri, Karayutaka, Aiko Machi, Kogane Masari, Hoshi Kogane, Satsuma Masari, Konamizuki, Tama Akane, Kyushu No. 2, Hoshi Kirari, Hime Ayaka, Kyushu No. 138, Beni Haruka, Toki Masari, Ake Murasaki, Kyushu No. 137, Okiko Gane, Aya Komachi, Daichi no Yume, Hama Komachi, Quick Sweet, Kyushu No. 121, Suiou, Tama Otome, Beni Masari, Purple Sweet Road, Murasaki Masari, Konahomare, Aya Murasaki, Nonglin Jireddo, Spring Kogane, Sunny Red, Silk Sweet, Annan Taro, Naruto Gold, Beni Azuma, Beni Satsuma, Annan Kogane, Takai 14, Sakide Gold, Goro Island Gold, Beni Akka, Kogan Senkan, etc. can be mentioned.

[0013] In this embodiment, the sweet potato extract is obtained by extracting specific components from sweet potatoes. The part used for extraction is not particularly limited. For example, it includes leaf blades, leaf stalks, vines, tuberous roots, rhizomes, fine roots, etc. These can be used alone or in combination. The sweet potato extract can be obtained, for example, by the method described in <Method for Preparing Plant Growth Promoting Composition> described later. The sweet potato powder is obtained by drying and pulverizing sweet potatoes or sweet potato extracts, and is not particularly limited.

[0014] The plant growth promoting composition in this embodiment is a composition having a plant growth promoting effect. Here, the plant growth promoting effect includes, for example, the promotion of growth such as the elongation or weight increase of the stem and leaf parts or the root part, the increase in the number of leaves, the promotion of flowering or fruiting, the increase in the number of flowers or fruits, the increase in the plant weight or crop yield, greening, or the promotion of tillering.

[0015] More specifically, the case where a plant growth promoting effect is observed means that the fresh weight increase amount (%) or dry weight increase amount (%) increases when comparing the case of using the plant growth promoting composition of this embodiment with the case of not using it. The fresh weight or dry weight may be the fresh weight or dry weight of the whole plant, or may be the fresh weight or dry weight of each part of the plant (preferably the root part). The fresh weight increase amount (%) or dry weight increase amount (%) when using the plant growth promoting composition preferably increases by 10% or more, more preferably 20%, and even more preferably 30% or more compared to the case of not using the plant growth promoting composition of this embodiment. The case where there is a plant growth promoting effect includes the case where growth is not observed at all without using the plant growth promoting composition and growth is observed after using the plant growth promoting composition. The above numerical values are the average values for the whole plant to which the plant growth promoting composition is applied.

[0016] In addition, the plant growth promoting effect also includes the effect of improving the following activities of plants. 1) Improvement of root growth, elongation of roots, and improvement of root survival rate 2) Increase in nutrient absorption efficiency 3) Induction of flower buds, promotion of flowering, and increase of fruit set. 4) Accumulation of components such as sugars 5) Increased water-saving effect 6) Inducing effect of callus formation 7) Improvement of plant size, particularly elongation or thickening of above-ground and underground parts. 8) Wound repair In other words, the plant growth-promoting composition of this embodiment may have growth-promoting effects such as elongation of stems and leaves or roots, increase in the number of leaves, promotion of flowering or fruiting, increase in the number of flowers or fruits, increase in plant weight or crop yield, greening, or promotion of tillering, in addition to the effects described in 1) to 8) above. The effect described in 1) above may promote nutrient absorption by the roots, thereby promoting the growth of the entire plant.

[0017] The plant growth promoting composition in this embodiment may have an effect of improving stress tolerance to various environmental stresses that plants experience, and in particular, it may have an effect of improving stress tolerance to high temperature stress and drought stress. In one embodiment, this embodiment also provides a plant growth promoting composition that has an effect of improving stress tolerance to one or more stresses selected from the group consisting of high temperature stress and drought stress. Furthermore, in one embodiment, this embodiment also provides a composition for improving high temperature stress tolerance and a composition for improving drought stress tolerance.

[0018] In this embodiment, stress tolerance to high temperature stress and drought stress refers to the ability to grow normally or in a near-normal state without substantially suffering undesirable effects such as inability to grow (death), poor growth (e.g., whitening or yellowing of the plant body, reduction in root length or number of leaves), reduced growth rate, or reduction in plant weight or crop yield, even under growth conditions that involve high temperature stress and drought stress, respectively. By improving high temperature stress tolerance and drought stress tolerance with the plant growth promoting composition of this embodiment, plants can grow normally even in external environments that would normally have undesirable effects on plant growth. The plant growth promoting composition of this embodiment may exhibit a stress tolerance-improving effect against one or more stresses selected from the group consisting of high temperature stress and drought stress by having a plant growth promoting effect, or it may exhibit a plant growth promoting effect by having a stress tolerance-improving effect against one or more stresses selected from the group consisting of high temperature stress and drought stress. For example, the plant growth promoting composition of this embodiment may exhibit a stress tolerance-improving effect against one or more stresses selected from the group consisting of high temperature stress and drought stress by improving the root development of plants.

[0019] In this embodiment, the effect of conferring stress tolerance to plants against high temperature stress or drought stress is, for example, the effect of promoting normal growth under high temperature or drought conditions. High temperature conditions may be appropriately determined by those skilled in the art based on common technical knowledge in this field, but conditions of 35°C or higher are preferred, for example, conditions of 35°C to 50°C. Drought conditions may be appropriately determined by those skilled in the art based on common technical knowledge in this field, but conditions of 70% humidity or lower are preferred, for example, conditions of 10% to 70% humidity, or conditions of 10% to 60%, 10% to 50%, 10% to 40%, or 10% to 30%.

[0020] In this embodiment, the heat stress tolerance or drought stress tolerance of a plant can be evaluated, for example, by growing the target plant under heat stress or drought stress conditions and evaluating its phenotype. Specifically, it can be evaluated by the following means: The presence or absence of heat stress tolerance can be confirmed by acclimatizing the target plant under high-temperature conditions, then growing it under conditions of optimal growth temperature and growth period, and evaluating its phenotype. The presence or absence of drought stress tolerance can be confirmed by acclimatizing the target plant under dry conditions, then growing it under conditions of optimal growth temperature and growth period, and evaluating its phenotype. The phenotype evaluated after acclimatization under dry conditions may be, for example, the water retention rate of any part of the plant.

[0021] If the plant growth promoting composition in this embodiment has an effect of improving stress tolerance to high temperature stress or drought stress, the plant growth promoting composition may also activate response genes to high temperature stress or drought stress. The plant growth promoting composition in this embodiment may exhibit an effect of improving stress tolerance to one or more stresses selected from the group consisting of high temperature stress and drought stress by activating response genes to one or more stresses selected from the group consisting of high temperature stress and drought stress.

[0022] The response genes to high temperature stress or drought stress are not particularly limited and include genes that are generally known as indicators of response to high temperature stress or drought stress, such as those disclosed in public databases such as the National Center for Biotechnology Information (NCBI), Ensembl Plants, The Arabidopsis Information Resource (TAIR), The Rice Annotation Project (RAP), and the Rice Annotation Project. Examples of response genes to high temperature stress include Os06g0682900, Os11g0216100, Os03g0426900, Os08g0127600, Os03g0161900, Os05g0460000, and Os05g0530400. Examples of response genes to drought stress include Os01g0165000, Os11g0454300, Os05g0542500, Os01g0702500, and Os01g0583100. For example, by applying the plant growth promoting composition of this embodiment to a plant, the expression levels of genes such as Os06g0682900, Os11g0216100, Os03g0426900, Os08g0127600, Os03g0161900, Os05g0460000, and Os05g0530400 in the plant acclimatized to high temperatures increase compared to the control. Similarly, by applying the plant growth promoting composition of this embodiment to a plant, the expression levels of genes such as Os01g0165000, Os11g0454300, Os05g0542500, Os01g0702500, and Os01g0583100 in the plant acclimatized to dry conditions increase compared to the control. The response genes to high temperature stress and drought stress may be high temperature stress tolerance genes and drought stress tolerance genes, respectively.

[0023] The plant growth promoting composition in this embodiment may contain one or more selected from the group consisting of sweet potato extract and sweet potato powder, either alone or in combination with one or more agriculturally acceptable components. Agriculturally acceptable components are not particularly limited, but examples include solvents, carriers, excipients, binders, solubilizers, stabilizers, thickeners, leavening agents, lubricants, surfactants, oily liquids, buffers, bactericides, antifreezes, defoamers, colorants, antioxidants, preservatives, and further active ingredients. Agriculturally acceptable carriers include agriculturally acceptable liquid carriers such as water, mineral oil fractions like kerosene or diesel oil, plant or animal-derived oils, cyclic or aromatic hydrocarbons (e.g., paraffin, tetrahydronaphthalene, alkylated naphthalenes or their derivatives, or alkylated benzenes or their derivatives), alcohols (e.g., methanol, ethanol, propanol, butanol, or cyclohexanol), ketones (e.g., cyclohexanone), or amines (e.g., N-methylpyrrolidone), or mixtures thereof.

[0024] If the plant growth promoting composition in this embodiment contains one or more additional active ingredients, various compounds known in the art that have an effect of improving stress tolerance to high temperature stress and drought stress can be applied as the additional active ingredients. The plant growth promoting composition tends to have an even greater effect of improving stress tolerance to high temperature stress and drought stress by containing one or more such additional active ingredients.

[0025] The plant growth promoting composition in this embodiment can be used in combination with conventionally known agricultural materials such as pesticides and fertilizers. Examples of agricultural materials include pesticides, fertilizers, soil conditioners, and growing media (potting soil). Specifically, pesticides may include fungicides, insecticides, insecticide-fungicides, acaricides, nematicides, rodenticides, insecticides / repellents, attractants, spreading agents, hormones (growth regulators), herbicides, etc. Fertilizers may include organic fertilizers, chemical fertilizers, liquid fertilizers, solid fertilizers, compound fertilizers, compost, growth promoters, vitality boosters, calcium supplements, etc. Soil conditioners may be intended for physical, chemical, or biological soil improvement, and may also include oxygen supply agents, etc. Furthermore, pesticides, fertilizers, soil conditioners, and growing media may contain components derived from plants, animals, lime, minerals, or microorganisms.

[0026] In a plant growth promoting composition, the content of one or more substances selected from the group consisting of sweet potato extract and sweet potato powder relative to the entire plant growth promoting composition may be any value as long as one or more substances selected from the group consisting of sweet potato extract and sweet potato powder function as an active ingredient for promoting plant growth. For example, it may be 5, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by mass (volume) or more, and 99, 95, 90, 80, 70, 60, 50, 40, 30, 20, or 10% by mass (volume) or less.

[0027] The plant growth promoting composition in this embodiment can be used as an agricultural chemical agent or pesticide to promote plant growth. The plant growth promoting composition may be in any form, such as a solid (e.g., powder or granules) or a liquid (e.g., solution or suspension), and is preferably used in the form of a liquid such as a solution or suspension. When used as a solution, it may be in liquid form, or it may be used as a liquid prepared at the time of application.

[0028] The dosage form of the plant growth promoting composition of this embodiment is not particularly limited and can be formulated in dosage forms commonly used in the art, such as emulsions, wettable powders, liquids, aqueous solutions, powders, pastes, or granules.

[0029] In this embodiment, the plants to which the plant growth promoting composition can be applied are not particularly limited, and examples include angiosperms and gymnosperms. Examples of target plants include Asteraceae plants such as chrysanthemums and gerberas, Solanaceae plants such as potatoes, tomatoes and eggplants, Brassicaceae plants such as rapeseed and rapeseed, Poaceae plants such as rice, maize, wheat, sugarcane and barley, Fabaceae plants such as soybeans, Apiaceae plants such as carrots, Lamiaceae plants such as basil, mint and rosemary, Convolvulaceae plants such as morning glories, Salicaceae plants such as poplars, and Euphorbiaceae plants such as castor bean, cassava and jatropha. Examples include plants of the Convolvulaceae family such as sweet potatoes, plants of the Rutaceae family such as oranges and lemons, plants of the Rosaceae family such as cherry blossoms and roses, plants of the Orchidaceae family such as phalaenopsis orchids, plants of the Gentianaceae family such as lisianthus, plants of the Primulaceae family such as cyclamen, plants of the Violaceae family such as pansies, plants of the Liliaceae family such as lilies, plants of the Amaranthaceae family such as sugar beets, plants of the Vitaceae family such as grapes, plants of the Cupressaceae family such as cedar and cypress, plants of the Oleaceae family such as olives and osmanthus, and plants of the Pinaceae family such as Japanese red pine.

[0030] The plants targeted may include not only the whole plant (i.e., a complete plant), but also plant tissues or organs (for example, cut flowers, or vegetative reproductive organs such as rhizomes, tubers, corms, or runners), cultured cells, and / or parts of the plant such as callus.

[0031] The plant growth promoting composition in this embodiment can be applied to the whole or a part of a plant at any growth stage, including before or after germination (for example, a seed, seedling, or the whole or a part of a mature plant).

[0032] <Method for preparing a plant growth promoting composition> As a method for preparing a plant growth promoting composition, for example, one or more components selected from the group consisting of sweet potato extract and sweet potato powder can be obtained, and then mixed with the above-mentioned agriculturally acceptable components as needed. The method for obtaining sweet potato extract is not particularly limited, and general methods for extracting plant extracts can be used. Specifically, for example, it can be obtained by a method that includes the steps of: obtaining a raw sweet potato extract material by heating or crushing one or more selected from the group consisting of leaf blades, petioles, vines, tubers, rhizomes, and fine roots, and then removing impurities; concentrating the raw sweet potato extract material obtained in the first step to obtain a sweet potato concentrate; and fractionating the sweet potato concentrate obtained in the first step to obtain a sweet potato extract containing specific components. Alternatively, the raw sweet potato extract material or the sweet potato concentrate may be used as is as sweet potato extract. The raw sweet potato extract material, sweet potato concentrate, or sweet potato extract may be heated or pressurized in or after each step. When performing the heat treatment or pressurization treatment, a solvent may be added as appropriate. Furthermore, the conditions for obtaining sweet potato extract can be appropriately determined depending on the variety, part, and condition of the sweet potato used. The method for obtaining sweet potato powder is not particularly limited. It can be obtained by drying sweet potato residue such as sweet potato extract raw materials, sweet potato concentrate, or impurities generated when obtaining sweet potato extract, or by drying fresh or frozen sweet potato (one or more selected from the group consisting of sweet potato leaf blades, petioles, vines, tubers, peduncles, and fine roots) using methods such as hot air drying, air drying, dry heat drying, or reduced pressure drying, and then crushing it into a powder.

[0033] (Crushing process) Sweet potatoes can be crushed using fresh or dried sweet potatoes, for example, by using a mixer. When crushing sweet potatoes, an appropriate amount of water may be added to facilitate processing with a mixer or other device. The crushed sweet potatoes are filtered using a filter cloth, filter paper, or the like to obtain a sweet potato extract raw material from which impurities have been removed. When filtration, an extraction solvent such as an organic solvent may be added beforehand. Alternatively, impurities may be removed by obtaining the supernatant using a centrifuge instead of filtration.

[0034] (concentration process) The obtained sweet potato extract raw material can be concentrated to obtain a sweet potato concentrate using methods such as vacuum concentration, freeze concentration, or membrane concentration. The concentration ratio is preferably 3 to 30 times, and more preferably 4 to 20 times. When the concentration ratio is 5 times or more, the amount of plant growth promoting composition added to the plant is reduced, which improves handling and tends to reduce transportation costs. When the concentration ratio is 30 times or less, the amount of precipitate in the plant growth promoting composition is reduced, which tends to make it easier to handle. Furthermore, in the preparation of the plant growth promoting composition, concentration of the sweet potato extract raw material is not essential, and the obtained sweet potato extract raw material may be subjected directly to the following fractionation steps.

[0035] (Fractional process) The obtained sweet potato concentrate can be fractionated by solvent extraction or other methods to obtain sweet potato extract containing specific components. In the fractionation process, for example, hydrophilic and hydrophobic fractions can be obtained by liquid-liquid partitioning. Further purification can be obtained by passing the fraction through a column.

[0036] The sweet potato extract obtained in the fractionation process may be further purified or separated into highly active fractions as needed. Purification methods include, for example, filtration and adsorption (ion exchange resin column, activated carbon column, etc.). Separation methods for highly active fractions include gel filtration, adsorption, silica gel column chromatography, and HPLC.

[0037] <Plant growth promotion method> The plant growth promotion method in this embodiment is a method of promoting plant growth by using a composition containing one or more selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient on a plant, or on the soil or culture solution in which the plant grows. In this method, the plant growth promotion composition can be applied to a plant or a part thereof (e.g., a seed, seedling, or mature plant) at any growth stage, including before or after germination. Furthermore, it can be applied not only to the plant itself, but also to the soil, culture medium, or culture solution in which the plant grows. By applying the plant growth promotion composition to a plant in a growth stage or to the soil, culture medium, or culture solution in which the plant grows, plant growth can be promoted.

[0038] By using a composition containing one or more selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient in plants, the soil in which the plants grow, or the culture solution, it is also possible to improve the stress tolerance of plants to one or more selected from the group consisting of high temperature stress and drought stress. This embodiment also provides a method for improving stress tolerance to one or more selected from the group consisting of high temperature stress and drought stress.

[0039] The plant growth promoting composition may be applied to plants once or multiple times. Similarly, if there are multiple application periods, the number of applications at each period may also be once or multiple times.

[0040] Methods for applying the plant growth-promoting composition to plants include, for example, addition, spraying, coating, and immersion. These methods may be used individually or in combination of two or more. The application of the plant growth-promoting composition to plants may be done manually or using machinery. When using machinery, there are no particular limitations, but for example, application (spraying) may be done using a drone.

[0041] The amount of plant growth promoting composition to be applied to plants is preferably 0.001 to 50% by mass or 0.001 to 50% by volume, more preferably 0.01 to 30% by mass or 0.01 to 30% by volume, and even more preferably 0.01 to 10% by mass or 0.01 to 10% by volume, when applied to the culture solution in which the plants are growing, or when diluted with a diluent and applied to the field or other area where the plants are growing. While sufficient plant growth promoting effects tend to be obtained when the amount of plant growth promoting composition is within the above range, the amount used may be appropriately adjusted depending on the content of one or more selected from the group consisting of sweet potato extract and sweet potato powder in the plant growth promoting composition, the type and growth stage of the plant to which the plant growth promoting composition is applied, and the plant's growing environment such as temperature, humidity, and light. The amount used may also be determined by investigating the concentration range in which the effect is obtained using known cultivation test methods. When applying a plant growth-promoting composition diluted with a diluting solvent to plants using a drone, the amount of solution that can be carried on the drone is limited by the drone's payload capacity, etc. Therefore, the amount of plant growth-promoting composition used relative to the diluting solvent is preferably 1 to 50% by mass or 1 to 50% by volume.

[0042] The components of the culture solution and diluent described above are not particularly limited as long as they do not adversely affect plant growth, and may include water, pesticides, etc.

[0043] The above usage amounts will vary depending on the concentration ratio of the sweet potato extract raw material mentioned above, but the above usage amounts represent the preferred range when the concentration ratio is between 3 and 30 times. [Examples]

[0044] The present invention will be described in more detail using examples and comparative examples, but the present invention is not limited in any way by these examples.

[0045] (Method for measuring root weight) The roots were identified based on the color and shape of the rice plants, and their weight was measured in a bottle using a microbalance.

[0046] (Preparation of sweet potato powder) Sweet potato powder was obtained by crushing dried sweet potato tubers with the skin on.

[0047] [Example 1] We evaluated whether sweet potato powder increases root weight using rice plants.

[0048] (seedling raising period) Rice seedlings germinated by soaking in distilled water were transferred to hydroponic solutions at the concentrations shown in Table 1 for the seedling stage. The seedlings were then transferred to an artificial climate chamber, where they were grown while the hydroponic solution was changed. (Exam period) Two experimental plots were designed: one plot containing 900 mL of hydroponic solution at the concentrations shown in Table 1, into which rice plants grown as described above were transferred. 0.36 g of sweet potato powder was added to achieve a final concentration of 0.04% by mass, and the other plot contained no sweet potato powder (control plot). Both plots were grown in artificial climate chambers. After cultivation, the rice plants were removed, dried, and their roots were collected and weighed. The results showed a 34.9% weight increase in the plot with 0.04% by mass of sweet potato powder compared to the control plot (Figures 1 and 2). Therefore, it was demonstrated that sweet potato powder has the effect of increasing root weight.

[0049] [Table 1]

[0050] [Example 2] The changes in gene expression in rice caused by sweet potato powder were evaluated using rice cultivated in Example 1.

[0051] (Sample preparation) Total RNA was extracted from the roots of rice plants in the control group of Example 1 and the group treated with 0.04% by mass of sweet potato powder.

[0052] (RNA extraction) RNA samples were obtained using the Maxwell RSC Plant RNA Kit (Promega) and Maxwell RSC Instrument (Promega) according to the instructions. (RNA quality check) Measuring equipment: Agilent 2100 Bioanalyzer <g2939a>Using (Agilent Technologies), reagent kit: Agilent RNA6000 Nano kit <5067-1511> (Agilent Technologies) and analysis software: 2100 expert software <version B.02.07> (Agilent Technologies), after confirming that there are no problems with the quality of the RNA sample, it was used for library preparation. (Library preparation) Using the QuantSeq 3'mRNA-Seq Library Prep Kit, a library for the NextSeq next-generation sequencer was prepared according to the following steps. 1 Use 100 ng of total RNA 2 cDNA synthesis using oligo(dT) primers 3 Removal of template mRNA 4 Double-stranded cDNA synthesis using random primers 5 14-cycle PCR using indexed adapters 6 Purification with beads

[0053] (Analysis by next-generation sequencer) · Sequence analysis Equipment: NextSeq500 (Illumina) Reagent: NextSeq 500 / 550 High Output Kit v2.5 (75 Cycles) <2002490>6> (Illumina) · Sequence (outline) Sequencing was performed using NextSeq500 according to the following steps. 1 Addition of sequencing reagent 2 One-base extension reaction 3 Removal of unreacted bases 4 Incorporation of fluorescence signal 5 Removal of protecting group and fluorescence < extraordinari000264>6 Repeat the cycles of 2Cycle…3Cycle… and perform up to 75 cycles

[0054] (Data analysis) • Primary data analysis Analysis program: bcl2fastq ver2.20 (Illumina Corporation) A fastq file was created from the obtained reads using the program bcl2fastq (Illumina). • Secondary data analysis Operating System of the analysis computer: Ubuntu Desktop 22.04.4 LTS Analysis software: FastQC, hisat2, samtools, HTSeq, DESeq2 The analysis was performed using the software described above. 1. Checking the quality of the reeds We used FastQC to verify the quality of the bases contained in the obtained fastq file. 2. Mapping and Sorting The data was mapped to the Oryza sativa reference genome, Oryza sativa Japonica Group (assembly IRGSP-1.0), using hisat2. Subsequently, the files were sorted and converted to binary data using samtools. 3 Lead Count The number of mapped reads was counted using the htseq-count within the HTSeq. 4 Statistical analysis Using the DESeq2 package on the statistical package R, we compared gene expression levels in the control group and the group treated with sweet potato extract. • Third-level data analysis We searched the Rice Annotation Project (https: / / rapdb.dna.affrc.go.jp / ) for genes reported in previous studies to be involved in high-temperature stress tolerance or drought stress tolerance. We then searched for these genes using the gene expression list created in this experiment.

[0055] Gene expression analysis revealed that in the sweet potato powder-added group, the expression levels of the high-temperature stress tolerance genes Os06g0716700 and Os08g0500700 were significantly increased by 1.54 and 1.66 times, respectively, in the above-ground parts (Figures 3 and 4; p-values ​​were 7.7 × 10⁻⁶). -4 and 3.6 × 10 -4 ). The following has been reported about these molecules related to high-temperature stress tolerance, and therefore they are thought to contribute to high-temperature stress tolerance. The group of molecules including homologous molecules of Os06g0716700 is generally known to be central to the function of high-temperature stress tolerance (Reference 1). This gene and similar genes have been reported to be widely present not only in Arabidopsis thaliana and rice, but also in rapeseed, soybeans, wheat, chili peppers, tomatoes, cocoa, grapes, etc. (Reference 2). The molecule homologous to Os08g0500700 is induced to be expressed by high-temperature stress tolerance, and biochemical analysis suggests that it plays an important role in the survival of plants even under high-temperature conditions (Reference 3). This gene and similar genes have been reported to be widely present not only in Arabidopsis thaliana and rice, but also in grapes, rose gum, Amborella trichopoda, oranges, liverworts, etc. (Reference 4). Furthermore, the expression level of the drought stress tolerance gene Os01g0165000 was increased 1.88 times in the above-ground parts (Figure 5; p-value = 0.045). Since the following has been reported regarding this gene related to drought stress tolerance, this molecule is also considered to contribute to drought stress tolerance. This gene and similar genes have been reported to be widely present not only in Arabidopsis thaliana and rice, but also in rapeseed, soybeans, wheat, chili peppers, tomatoes, cocoa, grapes, etc. (Reference 5), and are known to be molecules that respond to drought stress in common across species (Reference 6). Based on the above, it is thought that sweet potato extract has the effect of improving the tolerance of one or more stresses selected from the group consisting of high temperature stress and drought stress in many plants other than rice, by stimulating high temperature stress tolerance genes and drought stress tolerance genes, or molecules similar to these.

[0056] Reference 1: https: / / onlinelibrary.wiley.com / doi / 10.1002. / mco2.470 Reference 2: https: / / www.arabidopsis.org / locus?key=129590 Reference 3: https: / / pmc.ncbi.nlm.nih.gov / articles / PMC362454 Reference 4: https: / / phylogenes.arabidopsis.org / tree / PTHR11528 Reference 5: https: / / www.arabidopsis.org / locus?key=37566 Reference 6: https: / / academic.oup.com / jxb / article / 62 / 14 / 4731 / 482713

[0057] [Example 3] This study investigated whether sweet potato powder helps retain moisture in rice plants. The cultivation method was the same as in Example 1, except that the amount of sweet potato powder added was changed to 0.45g (0.05% by mass) or 0.90g (0.10% by mass). After cultivation for a certain period, the fully developed leaves of the rice plants from the control group (CT), the group with 0.45g (0.05% by mass) of sweet potato powder, or the group with 0.90g (0.10% by mass) of sweet potato powder were cut and placed in petri dishes. After creating air passages in the petri dishes, the conditions were changed to match those of the rice plants, and the weight was measured as needed to calculate the moisture loss rate.

[0058] The results of this experiment showed that both the group with 0.45g (0.05% by mass) of sweet potato powder and the group with 0.90g (0.10% by mass) of sweet potato powder showed a tendency for reduced moisture loss compared to the control group (CT) (Figure 6). Therefore, it was found that sweet potato powder improves drought stress tolerance.

Claims

1. A plant growth promoting composition comprising one or more substances selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient.

2. The plant growth promoting composition according to claim 1, which has an effect of improving stress tolerance to one or more stresses selected from the group consisting of high temperature stress and drought stress.

3. The plant growth promoting composition according to claim 2, which activates response genes to one or more selected from the group consisting of high temperature stress and drought stress.

4. A method for promoting plant growth, comprising using a plant growth promoting composition containing one or more selected from the group consisting of sweet potato extract and sweet potato powder as an active ingredient, on a plant, in the soil in which the plant grows, or in a culture medium.

5. The plant growth promoting method according to claim 4, wherein the amount of the plant growth promoting composition used in the culture medium or diluent is 0.001 to 50% by mass or 0.001 to 50% by volume.

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