Composition for improving environmental stress tolerance in plants and method therefor

Abstract

An object of the present invention is to provide a means for improving environmental stress in plants. The present invention provides a method and an agent for improving environmental stress tolerance in a plant, which contains at least one of lactone-type sophorolipid, acid-type sophorolipid, and sophorolipid glyceride as an active ingredient.

Description

[Technical field]

[0001] The present invention relates to a composition for improving environmental stress tolerance in plants and a method for using the same. [Background technology]

[0002] In recent years, various abnormal weather events have been reported around the world due to global warming. Among these, high temperatures and little rainfall cause great damage to commercial crops such as grains and vegetables that are used as food for humans, leading to price hikes and famine due to supply shortages. However, due to a global decline in water resources and on large-scale farms, it is often impossible to provide sufficient irrigation for commercial crops during high temperatures and little rainfall, which can lead to significant damage such as reduced yields and plant death.

[0003] Various reports have been published so far regarding methods for increasing the environmental stress tolerance of plants themselves and regarding agents for improving environmental stress tolerance. For example, a method for producing a stress-tolerant plant, in which a plant is cultivated under an artificially controlled light-dark cycle to obtain a stress-tolerant plant (Patent Document 1), and an agent for improving environmental stress resistance in plants, which contains ethanol or a solvate thereof as an active ingredient (Patent Document 2), have been reported.Furthermore, a method for enhancing environmental stress resistance has been reported in which desiccation resistance in a plant is induced by treating the plant with abscisic acid, the plant is subjected to desiccation stress, and then the plant is treated with an autophagy inhibitor, or an autophagy-related gene is deleted, the plant is treated with abscisic acid, and then the plant is subjected to environmental stress (Patent Document 3).

[0004] In addition, a plant growth enhancer that contains zerumbone or its analogs or their salts as the main component and that relieves environmental stress in plants, promotes plant growth, or improves the quality (Patent Document 4), a method for improving the drought resistance of plants that specifically inhibits ABA 8'-hydroxylase to increase the endogenous abscisic acid concentration (Patent Document 5), and a composition for improving the environmental stress resistance of plants that contains at least one of sanguinarine or its salts as an active ingredient (Patent Document 6) have been reported. In addition, a method using at least one of α,β-alkenal, α,β-alkanone, γ,δ-alkenal, γ,δ-alkanone, δ,ε-alkenal, δ,ε-alkanone, ε,ζ-alkenal, and ε,ζ-alkanone (Patent Document 7) has been reported, which is an unsaturated carbonyl compound that is a compound having 4 to 9 carbon atoms and does not have an unsaturated bond at the terminal.

[0005] Sophorolipids are amphiphilic lipids produced by microorganisms, mainly yeasts, and have a strong surface-active effect and excellent biodegradability, so in recent years, their use as a major biosurfactant has been developed. The genera Candida, Rhodotorula, Cryptococcus, Wickerhamiella, Cyberlindnera, Starmerella, Metschnikowia, etc. are known to produce sophorolipids. Among these, the non-pathogenic basidiomycete yeast Starmerella bombicola (formerly Candida bombicola) is the most promising, and its biosurfactant productivity reaches over 400g per liter of culture medium, making it suitable for commercial production, and many studies have been conducted using this yeast. The structures of sophorolipids produced by this yeast are shown in general formulas 1 and 2 below. General formula 1 is said to be the lactone type, and general formula 2 is said to be the acid type.

[0006] [ka] [ka]

[0007] In addition, Non-Patent Document 1 reports that the combined use of sophorolipids and low molecular weight peptides can impart high temperature stress resistance to tea; however, the sophorolipids are used for the purpose of improving the permeability of low molecular weight peptides, and this is not an effect of the sophorolipids alone. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2018-166480 A [Patent Document 2] Re-tabled publication 2018 / 123651 [Patent Document 3] JP 2016-199519 A [Patent Document 4] JP 2016-145159 A [Patent Document 5] JP 2013-231014 A [Patent Document 6] International Publication No. 2013 / 151041 [Patent Document 7] International Publication No. 2016 / 031775 [Patent Document 8] Patent No. 6954548 [Non-patent literature]

[0009] [Non-Patent Document 1] Plants (2023) Vol.12, NO.15, p.2817 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a new composition for improving environmental stress tolerance that improves environmental stress in plants without inhibiting photosynthesis, and to provide a method for improving environmental stress tolerance in plants by applying the composition for improving environmental stress tolerance to the plants. [Means for solving the problem]

[0011] As a result of intensive research, the present inventors have discovered that sophorolipids, which are highly biodegradable and safe, improve the environmental stress resistance of plants without inhibiting photosynthesis, and have thus completed the present invention. The present invention relates to the following (1) to ( 4 ) of the plants described in Drying Improves stress resistance Agent ,or( 5 )~( 7 ) of the plants described in Drying The present invention relates to a method for improving stress resistance. (1) Sophorolipid is the active ingredient do , Plant Drying Improves stress resistance Agent . (2) The method according to (1) above, wherein the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipids, acid-type sophorolipids, and glyceride-type sophorolipids. Agent . ( 3 ) The method according to (1) above, which contains a culture medium of a yeast that produces sophorolipids. Agent . ( 4 ) The above-mentioned sophorolipid-producing yeast is Starmerella bombicola. 3 ) Agent . ( 5 ) Sophorolipid of Active ingredients and do Botanical Drying Improves stress resistance Agent The method for producing a plant, comprising applying to the plant Drying How to improve your stress tolerance. (6 ) The content of sophorolipids relative to the total mass at the time of application The method according to (5) above, wherein the composition for improving environmental stress tolerance is applied to a plant at 0.005 to 5% by mass. ( 7 ) the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipids, acid-type sophorolipids, and glyceride-type sophorolipids, 5 )or( 6 ) The method according to claim 1. Effect of the Invention

[0012] The environmental stress tolerance improver containing the sophorolipid of the present invention can improve or enhance tolerance such as drought resistance without inhibiting photosynthesis. In addition, since the sophorolipid is biodegradable, it is an environmentally friendly tolerance improver, and its application to the soil in which plants grow can reduce the labor and cost required for frequent watering, and its application at the time of planting seedlings can also reduce damage caused by the withering of seedlings. [Brief description of the drawings]

[0013] [Figure 1] Photographs of the state of cabbage seedlings before and after the resistance test of Example 1 and after recovery. [Diagram 2] Figure 1. Hyperspectral camera image analysis data of cabbage seedlings at each stage. [Diagram 3] A graph showing the ND705 values ​​of cabbage seedlings at each stage in Figure 1. [Figure 4] Photographs of the state of cabbage seedlings before and after the resistance test of Example 2 and after recovery. [Diagram 5] Figure 4. Hyperspectral camera image analysis data of cabbage seedlings at each stage. [Figure 6] A graph showing the ND705 values ​​of cabbage seedlings at each stage in Figure 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Sophorolipids are amphiphilic lipids produced by microorganisms, mainly yeasts. They have strong surface-active properties and excellent biodegradability, and in recent years, their use as biosurfactants has been developed. Starmerella bombicola (formerly Candida bombicola), a non-pathogenic basidiomycete yeast, is well known as a sophorolipid-producing yeast. Its biosurfactant productivity reaches more than 400 g per liter of culture medium, making it suitable for commercial production, and many studies have been conducted using this yeast. Other sophorolipid-producing yeasts include Candida apicola, Candida bogoriensis, and Wickerhamiella domericqiae.

[0015] Sophorolipids are glycolipids in which long-chain hydroxy fatty acids and sophorose are bound, and when produced by Starmerella bombicola, they have been thought to be a mixture of lactone and acid forms shown in general formulas 1 and 2 in a ratio of approximately 6-8:2-4. However, in recent years, it has been discovered that unknown components with molecular structures different from those of conventionally known sophorolipids are present in the culture products of sophorolipid-producing fungi, which have been widely studied, and their structures have been identified (Patent Document 8). The structure is shown in general formula 3. Hereinafter, this will be referred to as the glyceride type in this specification.

[0016] [ka] (In the formula, R 1 ~R 3 are each independently hydrogen, a fatty acid ester having 2 to 22 carbon atoms, or the above-mentioned SL group, while R 1 ~R 3 At least one of the groups is an SL group. R in the SL group may be the same or different and represents a hydrogen atom or an acetyl group; R nrepresents a linear or branched alkyl or alkenyl group having 13 to 21 carbon atoms.

[0017] When produced by Starmerella bombicola, it is thought to be a mixture of lactone, acid and glyceride types in a ratio of approximately 5-7:1-4:1-2. The surfactant activity of this mixture is approximately 35-70mg / L in critical micelle concentration (CMC) and 35-75mN / m in surface tension, which is a strong surfactant at a concentration 10-100 times lower than that of sodium lauryl sulfate, which is widely used as a common surfactant. In addition, compared to alkylbenzene sulfonate, which is difficult to biodegrade, it is an environmentally significant material because it is easily biodegradable.

[0018] The sophorolipid of the present invention is at least one type selected from the group consisting of lactone-type, acid-type, and glyceride-type sophorolipids represented by general formulas 1 to 3. The sophorolipid of the present invention includes not only the sophorolipid itself but also its salts. Metals capable of forming salts with the sophorolipid include, but are not limited to, inorganic metals such as sodium, potassium, calcium, magnesium, copper, and aluminum, as well as ammonia and amines. Furthermore, in the composition for improving environmental stress resistance of the present invention, a culture solution of a yeast that produces sophorolipids can be used as is or added thereto.

[0019] In the present invention, the environmental stress is preferably at least one selected from the group consisting of salt stress, drought stress, and high temperature stress, and is particularly preferably drought stress. By applying the composition for improving environmental stress tolerance of a plant of this embodiment to a plant, the environmental stress tolerance of the plant can be improved. In the present invention, "improving environmental stress resistance of a plant" means that by applying the present invention to a plant population under growth conditions that cause environmental stress, 50% or more of the treated plant population exhibits resistance to the environmental stress. Environmental stress resistance can be evaluated by the means described below.

[0020] In the present invention, the environmental stress tolerance of a plant can be evaluated by, but is not limited to, the following means. For example, drought stress tolerance can be determined by subjecting a target plant to drought stress treatment for 1 to 14 days at a growth temperature and growth humidity that are dry for the plant (for example, in the case of cabbage, a temperature of 30°C and a humidity of 50% or less (for example, no water supply conditions)), and then, if desired, acclimatizing the plant for 1 to 14 days under growth conditions suitable for the plant, and evaluating the phenotype. The effect of improving the environmental stress resistance of a plant according to the present invention refers to the effect of promoting plant growth and improving the survival rate of the plant.

[0021] In the present invention, drought stress tolerance means a trait that allows a plant to grow normally even under growth conditions that cause drought stress, without suffering from undesirable effects such as death, poor growth, or a decrease in plant weight or crop yield. By improving the drought stress tolerance of a plant according to the present invention, the plant can grow normally even under external environments that cause undesirable effects on the growth of a normal plant.

[0022] One aspect of the present invention relates to a method for improving environmental stress tolerance of a plant by applying to the plant a composition for improving environmental stress tolerance of a plant, the composition containing a sophorolipid as an active ingredient. By applying a plant drought stress tolerance enhancer containing sophorolipid as an active ingredient to a plant, drought stress tolerance can be improved. Sophorolipid, which is an active ingredient of the composition for improving environmental stress tolerance of a plant of the present invention, can be used in combination with various additives that are commonly used in plants. Specifically, various fertilizers, pesticides, surfactants, biostimulants, etc. Furthermore, when applied to plants, the composition for improving environmental stress tolerance can be applied, for example, with a sophorolipid content of 0.005 to 5% by mass relative to the total mass at the time of application.

[0023] Plants to which the present invention can be applied are not particularly limited, and examples thereof include vegetables (cabbage, spinach, lettuce, komatsuna, Chinese cabbage, lettuce, mizuna, tomato, eggplant, broccoli, onion, leek, bell pepper, etc.), root vegetables (carrot, radish, potato, taro, sweet potato, burdock, turnip, etc.), beans (soybean, adzuki bean, kidney bean, broad bean, pea, peanut, etc.), fruit trees and fruits (apple, peach, pear, citrus fruit, grape, walnut, almond, banana, strawberry, etc.), grains (rice, barley, wheat, rye, oats, corn, etc.), melons (cucumber, pumpkin, cucumber, watermelon, melon, etc.), and other pasture grasses, turfgrass, crops for spices, flowers, etc. EXAMPLES

[0024] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples, "%" means "% by mass".

[0025] <Example 1> Drought stress tolerance test of cabbage using sophorolipids (part 1) Twenty cabbage seeds were sown on a water-absorbed urethane mat and cultivated in a parameter-fully controlled cultivation device (Growth Chamber TGL-1-5S, ESPEC) at 22°C, 16 hours light / 8 hours dark, and with a photon flux density of 90 μmol / s / m 2 The plants were grown for 14 days under the above conditions. After that, six seedlings with similar growth were planted in pots with urethane mats in soil (vegetable and flower seeding soil, Takii Seeds) and grown for 30 days at 22°C and 16 hours light / 8 hours dark. At this point, the plants were randomly divided into two groups. The soil in the treatment group was provided with 0.7% sophorolipid (ACS-Sophor (registered trademark), Allied Carbon Solutions), and the non-treatment group was provided with water. Excess water was removed from the trays, water supply was stopped, and the conditions in the cultivation apparatus were changed to 30°C and 20 hours light / 4 hours dark, to treat with drought stress. The pot positions in the cultivation apparatus were shuffled every day to ensure that the exposure to light and wind was not biased.

[0026] Eleven days after the start of the stress treatment, the plants were watered and grown for four days under the same conditions as before the stress treatment. The phenotype of the grown cabbage was observed with the naked eye. Photographs of the plants before stress treatment, after stress treatment (11 days), and after recovery treatment (4 days) are shown in Figure 1. In addition, for the same subjects, image analysis data from a hyperspectral camera (Eva Japan) using ND705, an index of chlorophyll content (active photosynthesis appears yellow, and more active photosynthesis appears red) is shown in Figure 2, and the quantified data is shown in Figure 3. As shown in Figure 1, in the untreated area, the entire leaf wilted after stress and did not return to a normal state even after recovery treatment, whereas in the sophorolipid-treated area, leaf wilting was partially suppressed even after stress treatment, and the leaves almost returned to a normal state after recovery treatment. This tendency is also clear from the results of Figure 2, which was taken with a hyperspectral camera (leaves are colored yellow when photosynthesis is active, and red when photosynthesis is more active). In addition, the ND705 value shown in Figure 3 also decreased due to drought stress in the untreated area, but in the sophorolipid-treated area, the value did not change significantly even after stress treatment, making it clear that normal photosynthetic ability was maintained.

[0027] <Example 2> Drought stress tolerance test of cabbage using sophorolipids (part 2) Thirty cabbage seeds were sown on a water-absorbed urethane mat and cultivated in a parameter-fully controlled cultivation device (Growth Chamber TGL-1-5S, ESPEC) at 22°C, 16 hours light / 8 hours dark, and with a photon flux density of 90 μmol / s / m 2The plants were grown for 13 days under the above conditions. Then, 12 seedlings with similar growth were planted in pots with urethane mats in soil (soil for cuttings and sowing seeds, ProtLeaf) and grown for 21 days at 22°C under a 16-hour light / 8-hour dark period. The plants were then randomly divided into 4 groups. The soil in the treatment groups was supplemented with 0.35, 0.7, or 1.05% sophorolipid (ACS-Sophor (registered trademark), Allied Carbon Solutions), and the non-treatment groups were provided with water. Excess water was removed from the trays, water supply was stopped, and the conditions in the cultivation apparatus were changed to 30°C and 20-hour light / 4-hour dark, to treat the plants with drought stress. The pots in the cultivation apparatus were shuffled every day to ensure that the light and wind were not biased.

[0028] Four days after the start of the stress treatment, the plants were watered and grown for four days under the same conditions as before the stress treatment. The phenotype of the grown cabbage was observed with the naked eye. Photographs of the plants before stress treatment, after stress treatment (4 days), and after recovery treatment (4 days) are shown in Figure 4. In addition, for the same subjects, image analysis data from a hyperspectral camera (Eva Japan) using ND705, which is one of the indicators of chlorophyll content (active photosynthesis appears yellow, and more active photosynthesis appears red) is shown in Figure 5, and the quantified data is shown in Figure 6. As shown in Figure 4, in the untreated area, the entire leaf wilted after stress and did not return to a normal state even after recovery treatment, whereas in the sophorolipid-treated area, leaf wilting was partially suppressed even after stress treatment, and the leaves almost returned to a normal state after recovery treatment. This tendency is also clear from the results of Figure 5, which was taken with a hyperspectral camera. In addition, the ND705 value shown in Figure 6 also decreased due to drought stress in the untreated area, but in the sophorolipid-treated area, the value did not change significantly even after stress treatment, making it clear that normal photosynthetic ability was maintained.

[0029] <Example 3> Drought stress tolerance test of cabbage using sophorolipids (part 3) Eighty cabbage seeds were sown on a water-absorbed urethane mat and cultivated in a parameter-fully controlled cultivation device (Growth Chamber TGL-1-5S, ESPEC) at 22°C, 16 hours light / 8 hours dark, and with a photon flux density of 90 μmol / s / m 2 The plants were grown for 14 days under the above conditions. After that, 50 seedlings with similar growth were planted in pots with urethane mats in soil (vegetable and flower seeding soil, Takii Seeds) and grown for 30 days at 22°C and 16 hours light / 8 hours dark. At this point, the plants were randomly divided into two groups. The soil in the treatment group was provided with 0.7% sophorolipid (ACS-Sophor (registered trademark), Allied Carbon Solutions), and the non-treatment group was provided with water. Excess water was removed from the trays, water supply was stopped, and the conditions in the cultivation apparatus were changed to 30°C and 20 hours light / 4 hours dark, to treat with drought stress. The pot positions in the cultivation apparatus were shuffled every day to ensure that the light and wind exposure were not biased.

[0030] Eleven days after the start of the stress treatment, the plants were watered and grown for four days under the same conditions as before the stress treatment, and the recovery of the plants was observed. The number of cabbage seedlings that recovered after the drought stress treatment is shown in Table 1. All individuals in the sophorolipid treatment area recovered. [Table 1]

[0031] <Example 4> Drought stress tolerance test of cabbage using sophorolipids (part 4) 100 cabbage seeds were sown on a water-absorbed urethane mat and cultivated in a parameter-fully controlled cultivation device (Growth Chamber TGL-1-5S, ESPEC) at 22°C, 16 hours light / 8 hours dark, and with a photon flux density of 90 μmol / s / m 2The plants were grown for 13 days under the above conditions. After that, 80 seedlings with similar growth were planted in pots with urethane mats in soil (soil for cuttings and sowing seeds, Protreaf) and grown for 21 days at 22°C with a 16-hour light / 8-hour dark period. The plants were then randomly divided into 4 groups. The soil in the treatment group was provided with 0.35, 0.7, and 1.4% (ACS-Sophor (registered trademark), Allied Carbon Solutions), and the non-treatment group was provided with water. Excess water was removed from the trays, water supply was stopped, and the conditions in the cultivation device were changed to 30°C with a 20-hour light / 4-hour dark period, to treat the plants with drought stress. The positions of the pots in the cultivation device were shuffled every day to ensure that the light and wind were not biased.

[0032] Four days after the start of the stress treatment, the plants were watered and grown for four days under the same conditions as before the stress treatment, and the condition of the grown cabbages was observed with the naked eye. The number of cabbage seedlings that recovered after drought stress treatment is shown in Table 2. All individuals recovered in the sophorolipid treatment groups (treatment concentrations of 0.35, 0.7, and 1.4%). [Table 2]

Claims

1. An agent that improves plants' resistance to drought stress, with sophorolipid as the active ingredient.

2. The agent according to claim 1 , wherein the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipids, acid-type sophorolipids, and glyceride-type sophorolipids.

3. The agent according to claim 1 , comprising a culture medium of a yeast that produces sophorolipid.

4. The agent according to claim 3 , wherein the sophorolipid-producing yeast is Starmerella bombicola.

5. A method for improving drought stress tolerance in a plant, comprising applying to the plant a plant drought stress tolerance enhancer containing sophorolipid as an active ingredient.

6. The method according to claim 5, wherein the sophorolipid content is 0.005 to 5 mass% relative to the total mass at the time of application.

7. The method according to claim 5 or 6, wherein the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipids, acid-type sophorolipids, and glyceride-type sophorolipids.

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