Environmental stress tolerance-enhancing composition for enhancing plant environmental stress tolerance and method therefor

Abstract

To provide means for enhancing environmental stress tolerance in plants.SOLUTION: The present invention provides a method and an agent for enhancing environmental stress tolerance in plants. The environmental stress tolerance-enhancing agent comprises at least one selected from a lactonic sophorolipid, an acidic sophorolipid, and a sophorolipid glyceride as an active ingredient.SELECTED DRAWING: Figure 1

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 Art

[0002] Due to recent global warming, various abnormal weather conditions have been reported around the world. Among these, high temperature and low rainfall cause great damage to commercial crops that are human food such as grains and vegetables, leading to price increases and hunger due to supply shortages. However, on a global scale, the reduction of water resources and in large-scale farms, it is often impossible to sufficiently irrigate commercial crops during high temperature and low rainfall, which is likely to lead to great damage such as a decrease in yield and withering.

[0003] So far, various reports have been made regarding methods for increasing the environmental stress tolerance of plants themselves and environmental stress tolerance improvers. For example, a method for producing stress-tolerant plants (Patent Document 1) in which plants are cultivated under an artificially controlled light-dark cycle to obtain stress-tolerant plants, and an environmental stress tolerance improver for plants (Patent Document 2) containing ethanol or its solvate as an active ingredient have been reported. Furthermore, a method for enhancing tolerance to environmental stress (Patent Document 3) has been reported in which the drought tolerance of plants is induced by treatment with abscisic acid, a drought stress is imposed, and then treatment is carried out using an autophagy inhibitor or an autophagy-related gene is deleted, and an environmental stress is imposed after treatment with abscisic acid.

[0004] In addition, a plant growth promoter (Patent Document 4) that alleviates environmental stress in plants, promotes plant growth, or improves quality, with zearnimbone or its analogs or their salts as the main component, and a method for improving the drought tolerance of plants (Patent Document 5) that specifically suppresses ABA8'-hydroxylase to increase the concentration of endogenous abscisic acid, have been reported to contain at least one of sanguinarine or its salts as an active ingredient in a composition for improving the environmental stress tolerance of plants (Patent Document 6). Also, for unsaturated carbonyl compounds, for example, a method (Patent Document 7) using at least one selected from compounds having 4 to 9 carbon atoms without an unsaturated bond at the terminal, such as 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, has been reported.

[0005] On the other hand, sophorolipid is an amphiphilic lipid produced by microorganisms, mainly yeasts. It has a strong surfactant action and is excellent in biodegradability. Therefore, in recent years, its use development has been promoted as the main player in biosurfactants. As the producing bacteria of sophorolipid, Candida genus, Rhodotorula genus, Cryptococcus genus, Wickerhamiella genus, Cyberlindnera genus, Starmerella genus, Metschnikowia genus, etc. are known. Among these, Starmerella bombicola (old name Candida bombicola), a non-pathogenic basidiomycetous yeast, is promising. Since the productivity of its biosurfactant reaches more than 400 g per liter of the culture solution, it is suitable for commercial production, and many studies have been conducted using this yeast. The structures of the sophorolipids produced by this yeast are shown in the following General Formulas 1 and 2. General Formula 1 is said to be the lactone type, and General Formula 2 is the acid type.

[0006]

Chemical formula

Chem.

[0007] In addition, Non-Patent Document 1 reports that the combination of sophorolipid and low-molecular-weight peptide imparts high-temperature stress tolerance to tea. However, sophorolipid is used for the purpose of improving the permeability of low-molecular-weight peptide, and it is not the effect of sophorolipid alone.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Documents

[0009]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a novel composition for improving environmental stress tolerance in plants without inhibiting photosynthesis, and also to provide a method for improving environmental stress tolerance in plants by applying the composition for improving environmental stress tolerance to plants. **Means for Solving the Problems**

[0011] As a result of intensive studies, the present inventors have found that sophorolipid, which is excellent in biodegradability and safety, improves the environmental stress tolerance of plants without inhibiting photosynthesis, and have completed the present invention. The present invention relates to a composition for improving environmental stress tolerance in plants described in the following (1) to (5), or a method for improving environmental stress tolerance in plants described in (6) to (8). (1) A composition for improving environmental stress tolerance in plants, containing sophorolipid as an active ingredient. (2) The composition for improving environmental stress tolerance according to (1) above, wherein the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipid, acid-type sophorolipid, and glyceride-type sophorolipid. (3) The composition for improving environmental stress tolerance according to (1) above, wherein the environmental stress is at least one selected from the group consisting of salt stress, drought stress, and high temperature stress. (4) The composition for improving environmental stress tolerance according to (1) above, containing a culture solution of yeast that produces sophorolipid. (5) The composition for improving environmental stress tolerance according to (4) above, wherein the yeast that produces the sophorolipid is Starmerella bombicola. (6) A method for improving environmental stress tolerance in plants, characterized by applying a composition for improving environmental stress tolerance in plants, containing sophorolipid as an active ingredient, to plants. (7) The method according to (6) above, wherein a composition for improving environmental stress tolerance, in which the content of sophorolipid is 0.005 to 5% by mass based on the total mass at the time of application, is applied to plants. (8) The method according to (6) or (7) above, wherein the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipid, acid-type sophorolipid, or glyceride-type sophorolipid.

Advantages of the Invention

[0012] The environmental stress tolerance improver containing the sophorolipid of the present invention can improve or enhance tolerance such as drought tolerance without inhibiting photosynthesis. Further, since the sophorolipid is biodegradable, it is an environmentally friendly tolerance improver. By applying it to the soil where plants grow, the labor and cost of frequent watering can be reduced, and by applying it at the time of transplanting seedlings, the damage of seedling death can also be reduced.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] Sophorolipid is an amphiphilic lipid produced by microorganisms, mainly yeasts. It has strong surfactant activity and is excellent in biodegradability. Therefore, in recent years, its application development has been promoted as the main player in biosurfactants. As a yeast that produces sophorolipid, non-pathogenic basidiomycetous yeast Starmerella bombicola (formerly known as Candida bombicola) is well known. Since the productivity of its biosurfactant can reach more than 400 g per liter of culture broth, it is suitable for commercial production, and many studies have been conducted using this yeast. In addition, as other yeasts that produce sophorolipid, Candida apicola, Candida bogoriensis, Wickerhamiella domericqiae, etc. are known.

[0015] Sophorolipid is a glycolipid in which a long-chain hydroxy fatty acid and sophorose are bonded. When produced by Starmerella bombicola, it has been considered that the lactone type and acid type shown by General Formula 1 and General Formula 2 are approximately a mixture of 6 - 8:2 - 4. However, in recent years, it has been found that there are unknown components with different molecular structures from the conventionally known sophorolipids in the culture products of sophorolipid-producing bacteria that have been widely studied, and their structures have been specified (Patent Document 8). The structure is shown in General Formula 3. Hereinafter, it is referred to as the glyceride type in this specification.

[0016] [Chemical formula] (In the formula, R 1 ~R 3 are each independently hydrogen, a fatty acid ester having 2 to 22 carbon atoms, or the above SL group, provided that at least one of R 1 ~R 3 is the SL group. R in the SL group represents hydrogen or an acetyl group, which may be the same or different, and R nrepresents a linear or branched alkyl or alkenyl group having 13 to 21 carbon atoms.)

[0017] When produced by Starmerella bombicola, it is considered to be a mixture of lactone type, acid type and glyceride type in approximately the ratio of 5 - 7:1 - 4:1 - 2. The surface activity of this mixture shows a strong surface activity at a concentration which is 1 / 10 to 1 / 100 of that of sodium lauryl sulfate which is commonly used as a surfactant, with a critical micelle concentration (CMC) of approximately 35 - 70 mg / L and a surface tension of 35 - 75 mN / m. Also, compared with alkylbenzene sulfonic acid which is difficult to biodegrade, it is a material that is easy to biodegrade and environmentally significant.)

[0018] The sophorolipid of the present invention is at least one selected from the group consisting of lactone type, acid type and glyceride type sophorolipids represented by General Formulas 1 - 3.) In addition, the sophorolipid of the present invention includes not only itself but also its salts. Metals that can form salts with sophorolipids include, but are not limited to, for example, inorganic metals such as sodium, potassium, calcium, magnesium, copper, aluminum, etc., as well as ammonia and amines, etc., but are not limited thereto.) Furthermore, for the composition for improving environmental stress tolerance of the present invention, the culture solution of yeast that produces sophorolipid can be used as it is or after addition.)

[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 drought stress is particularly preferred. By applying the composition for improving environmental stress tolerance of plants in this embodiment to plants, the environmental stress tolerance of the plants can be improved.) In the present invention, "improving the environmental stress tolerance of plants" means that when the present invention is applied to a plant population under growth conditions subjected to environmental stress, 50% or more of the treated plant population shows tolerance to environmental stress. The environmental stress tolerance can be evaluated by the means described below.)

[0020] In the present invention, the environmental stress tolerance of plants can be evaluated by the following means, although not limited thereto. For example, the drought stress tolerance can be evaluated by subjecting the target plant to drought stress treatment for a period of 1 day to 14 days under the growth temperature and growth humidity in a dry state for the plant (for example, in the case of cabbage, air temperature 30°C, humidity 50% or less (for example, under non-watering conditions)), and then, if desired, acclimating the plant for a period of 1 day to 14 days under the growth conditions suitable for the plant, and determining by evaluating its phenotype. The effect of improving the environmental stress tolerance of plants according to the present invention refers to the effect of promoting plant growth and improving the survival rate.

[0021] The drought stress tolerance in the present invention means a trait that can grow normally without substantially being affected by undesirable effects such as withering, poor growth, or a decrease in plant weight or crop yield even under growth conditions subjected to drought stress. By improving the drought stress tolerance of plants according to the present invention, plants can be grown normally even in an external environment that has an undesirable effect on growth in normal plants.

[0022] One aspect of the present invention relates to a method for improving the environmental stress tolerance of plants by applying to the plants a composition for improving the environmental stress tolerance of plants, which contains sophorolipid as an active ingredient. By applying to the plants an agent for improving the drought stress tolerance of plants containing sophorolipid as an active ingredient, the drought stress tolerance can be improved. Sophorolipid, which is an active ingredient of the composition for improving the environmental stress tolerance of plants of the present invention, can be used in combination with various additives commonly used in plants. Specifically, they are various fertilizers, agricultural chemicals, surfactants, biostimulants, and the like. Also, when applying to plants, for example, it can be applied with a composition for improving environmental stress tolerance in which the content of sophorolipid is 0.005 to 5% by mass based on the total mass at the time of application.

[0023] The applicable plants of the present invention are not particularly limited. For example, vegetables (such as cabbage, spinach, lettuce, komatsuna, Chinese cabbage, salad turnip, mizuna, tomato, eggplant, broccoli, onion, leek, pepper, etc.), root vegetables (such as carrot, daikon radish, potato, taro, sweet potato, burdock, turnip, etc.), legumes (such as soybean, adzuki bean, kidney bean, broad bean, pea, peanut, etc.), fruit trees and fruits (such as apple, peach, pear, citrus fruits, grape, walnut, almond, banana, strawberry, etc.), cereals (such as rice, barley, wheat, rye, oats, corn, etc.), gourds (such as cucumber, pumpkin, zucchini, watermelon, melon, etc.), and in addition, it can also be applied to forage grasses, lawn grasses, crops for spices, etc., and flowers.

Example

[0024] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. In the examples, "%" means "mass%".

[0025] <Example 1> Drought stress tolerance test of cabbage by sophorolipid (Part 1) Twenty cabbage seeds were sown on a urethane mat that had been soaked in water, and grown in a parameter full control type cultivation device (Growth Chamber TGL-1-5S, Espec) at 22 °C, with a 16-hour light period / 8-hour dark period, and a photosynthetic photon flux density of 90 μmol / s / m 2 for 14 days. Then, six seedlings of the same growth stage were transplanted together with the urethane mat into the potting soil (seedling soil for vegetables and flowers, Takii Seedlings) in the pot, and grown at 22 °C, with a 16-hour light period / 8-hour dark period for 30 days. At this point, the plants were randomly divided into two groups. The treatment group was supplied with 0.7% sophorolipid (ACS-Sophor (registered trademark), manufactured by Allied Carbon Solutions) in the soil, and the non-treatment group was supplied with water. Excess water was removed from the tray, watering was stopped, and the conditions in the cultivation device were changed to 30 °C, with a 20-hour light period / 4-hour dark period for drought stress treatment. The pot positions in the cultivation device were shuffled daily to ensure that the exposure to light and wind was even.

[0026] Eleven days after the start of stress treatment, water was supplied to the plants, and they were grown for 4 days under the same conditions as before the stress treatment. The phenotype of the grown cabbages was observed with the naked eye. Photographs before stress treatment, after stress treatment (11 days), and after recovery treatment (4 days) are shown in Fig. 1. Also, for the same subjects, the image analysis data of a hyperspectral camera (Eva Japan) using ND705, which is one of the indicators of chlorophyll content (appears yellow when photosynthesis is active and redder when it is more active), are shown in Fig. 2, and the quantified data are shown in Fig. 3. As shown in Fig. 1, in the non-treated group, the whole leaves wilted after stress, and they did not return to the normal state even after the recovery treatment. In contrast, in the sophrolipid treatment group, the wilting of the leaves was partially suppressed even after the stress treatment, and they almost recovered to the normal state after the recovery treatment. This tendency is also clear from the results of Fig. 2 taken with the hyperspectral camera (appears yellow when photosynthesis is active and redder when it is more active). Also, the value of ND705 shown in Fig. 3 decreased due to drought stress in the non-treated group, but it was clarified that there was no significant change in the value in the sophrolipid treatment group even after the stress treatment, and the normal photosynthetic ability was maintained.

[0027] <Example 2> Drought stress tolerance test of cabbages using sophrolipid (Part 2) Thirty cabbage seeds were sown on a urethane mat that had absorbed water, and they were grown in a parameter full control type cultivation device (Growth Chamber TGL-1-5S, Espec) at 22 °C, with a 16-hour light period / 8-hour dark period, and a photosynthetic photon flux density of 90 μmol / s / m 2They were grown for 13 days under the specified conditions. Subsequently, 12 seedlings of similar growth were transplanted into the potting soil (seedling and sowing soil, prototroph) together with the urethane mat, and grown for 21 days at 22°C under a 16-hour light period / 8-hour dark period. Next, the plants were randomly divided into four groups. The soil in the treatment group was supplied with sophorolipid at 0.35%, 0.7%, and 1.05% (ACS-Sophor (registered trademark), manufactured by Allied Carbon Solutions), while the non-treatment group was supplied with water. Excess water was removed from the tray, watering was stopped, and the conditions inside the cultivation device were changed to 30°C under a 20-hour light period / 4-hour dark period for drought stress treatment. The pot positions inside the cultivation device were shuffled daily to ensure even exposure to light and wind.

[0028] Four days after the start of the stress treatment, water was supplied to the plants, and they were grown for 4 days under the same conditions as before the stress treatment. The phenotypes of the grown cabbages were observed with the naked eye. Photographs before the stress treatment, after the stress treatment (4 days), and after the recovery treatment (4 days) are shown in Figure 4. Also, for the same subjects, the image analysis data of a hyperspectral camera (Eva Japan) using ND705, which is one of the indicators of chlorophyll content (appears yellow when photosynthesis is active and redder when it is more active), are shown in Figure 5, and the quantified data are shown in Figure 6. As shown in Figure 4, in the non-treatment group, the entire leaves wilted after the stress, and did not return to the normal state even after the recovery treatment. In contrast, in the sophorolipid treatment group, the wilting of the leaves was partially suppressed even after the stress treatment, and almost returned to the normal state after the recovery treatment. This tendency is also clear from the results in Figure 5 taken with the hyperspectral camera. Also, the values of ND705 shown in Figure 6 decreased due to drought stress in the non-treatment group, but there was no significant change in the values in the sophorolipid treatment group even after the stress treatment, indicating that they maintained normal photosynthetic ability.

[0029] <Example 3> Drought Stress Tolerance Test of Cabbage with Sophorolipid (Part 3) 80 cabbage seeds were sown on a urethane mat that had absorbed water, and they were grown for 14 days in a parameter full-control cultivation device (Growth Chamber TGL-1-5S, Espec) at 22°C, with a 16-hour light period / 8-hour dark period, and a photosynthetic photon flux density of 90 μmol / s / m 2 under these conditions. Subsequently, 50 seedlings of similar growth were transplanted together with the urethane mat into the culture soil (seed sowing soil for vegetables and flowers, Takii Seedlings) in pots, and they were grown for 30 days at 22°C with a 16-hour light period / 8-hour dark period. At this point, the plants were randomly divided into two groups. The soil in the treatment group was supplied with 0.7% sophorolipid (ACS-Sophor (registered trademark), manufactured by Allied Carbon Solutions), and the non-treatment group was supplied with water. Excess water was removed from the trays, watering was stopped, and the plants were subjected to a drought stress treatment by changing the conditions in the cultivation device to 30°C with a 20-hour light period / 4-hour dark period. The pot positions in the cultivation device were shuffled daily to ensure that the exposure to light and wind was even.

[0030] Eleven days after the start of the stress treatment, water was supplied to the plants, and they were grown for 4 days under the same conditions as before the stress treatment to observe the recovery status of the plants. The results of the number of cabbage seedlings that recovered after the drought stress treatment are shown in Table 1. In the sophorolipid treatment group, all individuals recovered.

Table 1

[0031] <Example 4> Drought Stress Tolerance Test of Cabbage with Sophorolipid (Part 4) 100 cabbage seeds were sown on a urethane mat that had absorbed water, and they were grown in a parameter full-control cultivation device (Growth Chamber TGL-1-5S, Espec) at 22°C, with a 16-hour light period / 8-hour dark period, and a photosynthetic photon flux density of 90 μmol / s / m 2They were grown for 13 days under the specified conditions. Subsequently, 80 seedlings of similar growth were transplanted into the potting soil (seedling and sowing soil, protocorm) along with the urethane mat, and grown for 21 days at 22°C with a 16-hour light period / 8-hour dark period. Next, the plants were randomly divided into four groups. The treatment groups were supplied with 0.35%, 0.7%, and 1.4% ACS-Sophor (registered trademark, manufactured by Allied Carbon Solutions) in the soil, while the non-treatment group was supplied with water. Excess water was removed from the trays, watering was stopped, and the plants were subjected to a drought stress treatment by changing the conditions in the cultivation apparatus to 30°C with a 20-hour light period / 4-hour dark period. The pot positions in the cultivation apparatus were shuffled daily to ensure even exposure to light and wind.

[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 growth status of the grown cabbages was observed with the naked eye. The results of the number of recovered cabbage seedlings after the drought stress treatment are shown in Table 2. All individuals in the Sopholipid treatment groups (treatment concentrations 0.35%, 0.7%, and 1.4%) recovered.

Table 2

Claims

1. A composition for improving environmental stress tolerance of plants, containing sophorolipid as an active ingredient.

2. The composition for improving environmental stress tolerance according to claim 1, wherein the sophorolipid is at least one selected from the group consisting of lactone-type sophorolipid, acid-type sophorolipid, and glyceride-type sophorolipid.

3. The composition for improving environmental stress tolerance according to claim 1, wherein the environmental stress is at least one selected from the group consisting of salt stress, drought stress, and high temperature stress.

4. The composition for improving environmental stress tolerance according to claim 1, containing a culture solution of yeast that produces sophorolipid.

5. The composition for improving environmental stress tolerance according to claim 4, wherein the yeast that produces sophorolipid is Starmerella bombicola.

6. A method for improving environmental stress tolerance of plants, characterized by applying a composition for improving environmental stress tolerance of plants, containing sophorolipid as an active ingredient, to the plants.

7. The method according to claim 6, wherein a composition for improving environmental stress tolerance with a sophorolipid content of 0.005 to 5% by mass based on the total mass at the time of application is applied to the plants.

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

Images