JP2024084243A - Coated seed, seed coating agent and seed coating method - Google Patents

Abstract

To provide a plant growth promotion technique using photosynthetic bacteria, capable of reducing a workload of an agricultural worker, being applicable to various plants, and acquiring stable effects.SOLUTION: A seed 16 of a plant is coated with a coating agent 15 containing photosynthetic bacteria cells, lipopolysaccharide derived from the photosynthetic bacteria, or lipid A derived from the lipopolysaccharide or the like, and a coating base. The coated seed can promote growth of roots of the plant after sowing, and consequently, improve absorption efficiency of nutrients and water so as to promote the growth of the entire plant body.SELECTED DRAWING: Figure 1

Description

The present invention relates to coated seeds, seed coating agents, and seed coating methods.

It has long been known that administering photosynthetic bacteria to plants can promote the growth of the plants (see, for example, Non-Patent Documents 1 to 3). Photosynthetic bacteria are non-pathogenic and easy to cultivate, so plant growth promoters whose main component is photosynthetic bacterial cells are widely used in fields such as agriculture, horticulture, and landscaping.

However, traditional plant growth promoters generally contain photosynthetic bacteria in a viable (living) state, which makes them difficult to manage during storage and transportation. Furthermore, traditional methods of administering plant growth promoters to plants generally involve foliar spraying, irrigation at the base of the plants, or pouring into rice paddies, but these administration methods require a lot of labor to be carried out in the field, and also require a large amount of photosynthetic bacteria to be used. For example, pouring into rice paddies requires about 10 liters of photosynthetic bacteria culture solution per 1 tan (10a).

To solve the above problems, some of the present inventors have proposed a new method for promoting plant growth using photosynthetic bacteria in Patent Document 1. This method promotes growth after germination by soaking plant seeds in a suspension of dead photosynthetic bacteria before sowing, and has the advantage of being extremely low cost and hassle-free compared to traditional methods of spraying photosynthetic bacteria on plants in farm fields or pouring photosynthetic bacteria into rice paddies.

JP 2022-038863 A

M. Elbadry, H. Gamal-Eldin, Kh. Elbanna, "Effects of Rhodobacter capsulatus inoculation in combination with graded levels of nitrogen fertilizer on growth and yield of rice in pots and lysimeter experiments", World J. Microbiol. Biotechnol., 15: pp.393-395 (1999) Hosny Gamal-Eldin, Khaled Elbanna "Field Evidence for the Potential of Rhodobacter capsulatus as Biofertilizer for Flooded Rice", Curr Microbiol. 62: pp.391-395 (2011) Wai-Tak Wong, Ching-Han Tseng, Shu-Hua Hsu, Huu-Sheng Lur, Chia-Wei Mo, Chu-Ning Huang, Shu-Chiung Hsu, Kung-Ta Lee, Chi-Te Liu "Promoting Effects of a Single Rhodopseudomonas palustris Inoculant on Plant Growth by Brassica rapa chinensis under Low Fertilizer Input", Microbes Environ. 29: pp.303-313 (2014) A. Koga, M. Goto, T. Morise, H.T.D. Tran, T. Kakimoto, K. Kashiyama, N. Yamauchi, K. Nakayama, S. Hayashi, S. Yamamoto, H. Miyasaka, "Value-added recycling of distillation remnants of Kuma Shochu: a local traditional Japanese spirit, with photosynthetic bacteria", Waste Biomass Valor., 11: pp.6717-6724 (2020)

However, the method described in Patent Document 1 requires the preparation of the photosynthetic bacteria suspension and the soaking of the seeds to be performed by the agricultural worker who performs the sowing work, and therefore the concentration of the bacteria in the suspension, the timing of the soaking process, and the soaking time are not necessarily constant, resulting in a problem of large variation in effectiveness. In addition, although the method described in Patent Document 1 is less time-consuming than the application of conventional plant growth promoters, it requires an extra step for agricultural workers before sowing, which has hindered its widespread use. Furthermore, the method described in Patent Document 1 is suitable for rice and other crops in which the seeds are soaked in water before sowing, but is not suitable for plants such as wheat that are sown without being soaked in water beforehand.

The present invention was made in consideration of the above points, and its purpose is to reduce the workload of agricultural workers in a plant growth promotion technology that uses photosynthetic bacteria, make it applicable to a variety of plants, and provide stable effects.

The coated seed according to the present invention, which has been developed to solve the above problems,
Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing photosynthetic bacteria and a coating base;
It has the following.

The coated seed according to the present invention, which has been developed to solve the above problems,
Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing a lipopolysaccharide derived from photosynthetic bacteria and a coating base;
The present invention may also have the following structure.

The coated seed according to the present invention, which has been developed to solve the above problems,
Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing lipid A and a coating base;
The present invention may also have the following structure.

In addition, the seed coating agent according to the present invention, which has been developed to solve the above problems, is
It contains photosynthetic bacteria cells and a coating base.

The seed coating agent according to the present invention, which has been developed to solve the above problems, is
It may contain lipopolysaccharide derived from photosynthetic bacteria and a coating base.

The seed coating agent according to the present invention, which has been developed to solve the above problems, is
It may contain lipid A and a coating base.

In addition, the seed coating method according to the present invention, which has been made to solve the above problems, comprises the steps of:
Any of the above seed coating agents is applied in a liquid state to the surface of a plant seed, and then the coating agent is dried.

The coated seeds, seed coating agent, and seed coating method according to the present invention can reduce the workload of agricultural workers in plant growth promotion technology using photosynthetic bacteria, can be applied to a variety of plants, and can provide stable effects.

FIG. 1 is a schematic diagram showing an outline of a seed coating method according to one embodiment of the present invention. Graphs showing the total root length, root surface area, number of root tips, and number of root branches of rice seeds coated with a coating agent containing cells of the photosynthetic bacterium Rhodobacter sp. Turu3 and using starch as a coating base, 14 days after sowing. 13 is a graph showing the total root length, root surface area, number of root tips, and number of root branches of rice seeds coated with a coating agent containing the fungus bodies and using sodium carboxymethylcellulose as a coating base, 14 days after sowing. Graphs showing the total root length, root surface area, number of root tips, and number of root branches of rice seeds coated with a coating agent containing the fungus bodies and using polyvinyl alcohol as a coating base, 14 days after sowing. Graph showing the total root length, root surface area, number of root tips, and number of root branches of rice seeds coated with a coating agent containing cells of the photosynthetic bacteria standard strain Rhodobacter sphaeroides NBRC 12203 ^T and using starch as a coating base, 14 days after sowing. Graph showing the total root length, root surface area, number of root tips, and number of root branches 14 days after sowing of rice seeds coated with a coating agent containing LPS derived from the standard strain and using starch as a coating base. A graph showing the total root length, root surface area, number of root tips, and number of root branches 14 days after sowing of rice seeds coated with a coating agent containing lipid A obtained from the LPS and using starch as a coating base.

As a result of extensive research into solving the above problems, the present inventors have found that by coating plant seeds with a coating agent containing photosynthetic bacteria cells, lipopolysaccharide (LPS) derived from photosynthetic bacteria, or lipid A derived from the LPS before sowing, root elongation after sowing is promoted in the same manner as in the method described in Patent Document 1. The present invention was conceived based on the above findings.

In other words, the coated seeds of the present invention are plant seeds coated with a coating agent containing at least one of photosynthetic bacteria cells, LPS derived from photosynthetic bacteria, or lipid A derived from the LPS or the like as an active ingredient.

In addition to the above-mentioned active ingredients, the coating agent contains a coating base for forming a coating layer on the surface of the seeds to retain the photosynthetic bacteria. It is desirable to use a coating base that is soluble or dispersible in water and has the property of hardening to form a coating when the solution or suspension is dried. Examples of such coating bases include polysaccharides such as starch or agarose, gelatin, or water-soluble polymers, which are generally used as gelling agents or thickeners. Examples of the water-soluble polymers that can be used preferably include carboxymethylcellulose or a salt thereof, or polyvinyl alcohol. The concentration of the coating base in the coating agent before hardening (i.e., in a liquid state) is not particularly limited, but is, for example, about 0.5% to 5% (preferably about 1% to 2%). Examples of methods for coating seeds with the coating agent include a method of immersing seeds in the coating agent, or applying or spraying the coating agent on the surface of the seeds and then drying the coating agent (surface coating method; encrusting). However, the coating method is not limited to this, and other methods can be used, such as a method of forming a very thin film on the surface of the seeds using a water-soluble polymer (film coating method), or a method of thickly coating the surface of the seeds with a mixture of inorganic particles such as talc, calcium peroxide, bentonite, or diatomaceous earth and the coating base, and then forming them into pellets (pelletization method).

The type of the photosynthetic bacteria is not particularly limited, but is preferably a purple non-sulfur bacterium, and particularly preferably a photosynthetic bacterium of the genus Rhodobacter. As the photosynthetic bacterium of the genus Rhodobacter, for example, Rhodobacter sphaeroides can be preferably used. As Rhodobacter sphaeroides, for example, bacterial bodies commercially available as agricultural materials such as soil improvement agents or soil activators, specifically, bacterial bodies commercially available under the names "PSB frozen bacterial bodies", "Aures PSB", "Hikari Aures", "NEW Pana Aures", or "Aures Midori" (sold by Matsumoto Microbiology Laboratory Co., Ltd.), etc. can be preferably used.

When the photosynthetic bacteria cells are used as the active ingredient, the concentration of the photosynthetic bacteria in the coating agent is preferably about 1 cell/mL to 10 ⁶ cells/mL (more preferably about 10 ¹ cell/mL to 10 ⁵ cells/mL), but is not limited thereto. The cells may be contained in the coating agent in a live state, but in consideration of ease of storage and handling, it is preferable to contain the live bacteria in a dead state obtained by heating or drying the live bacteria in advance. The temperature for heat-treating the live bacteria is 60°C or higher, preferably 70°C or higher, more preferably 100°C or higher, but is not limited thereto. The photosynthetic bacteria cells may be cells that have not been subjected to a cell-disrupting treatment, such as ultrasonic treatment, homogenizer treatment, treatment with a mortar and pestle, freeze-thawing treatment, or cell lysis treatment with an enzyme (i.e., intact), or may be cells that have been subjected to the above-mentioned cell-disrupting treatment.

When LPS derived from photosynthetic bacteria is used as the active ingredient, the concentration of LPS in the coating agent can be, for example, about 1 pg/mL to 1 μg/mL (preferably about 5 pg/mL to 50 pg/mL), but is not limited to this. LPS derived from photosynthetic bacteria can be obtained, for example, by disrupting photosynthetic bacteria cells by ultrasonic treatment or the like, centrifuging the resulting disrupted cell liquid, and extracting it from the insoluble fraction. Alternatively, commercially available LPS derived from photosynthetic bacteria may be used.

When lipid A is used as the active ingredient, the concentration of lipid A in the coating agent can be, for example, about 0.01 pg/mL to 1 μg/mL (preferably about 1 pg/mL to 1 ng/mL), but is not limited thereto. For example, lipid A obtained by acid hydrolysis (for example, heating at 100°C for about 1 hour in 0.1N hydrochloric acid) of LPS extracted from photosynthetic bacteria can be used. Chemically synthesized lipid A such as eritoran (E5564, CAS number: 185954-98-7) can also be used.

The present invention can be suitably used for plants of the Gramineae family, such as rice or wheat, but the types of plants to which the present invention can be applied are not limited to these.

Figure 1 shows an outline of a seed coating method according to one embodiment of the present invention. In this method, a predetermined amount of coating base (e.g., starch) 12 is first added to water 11 and dissolved or dispersed to prepare an aqueous solution or suspension of the coating base (hereinafter referred to as coating base liquid 13). Note that, if necessary, the water 11 may be heated before or after the addition of the coating base 12 in order to promote dissolution or dispersion of the coating base.

Then, a suspension of dead photosynthetic bacteria (hereinafter referred to as bacterial cell suspension 14) is added to the coating base liquid 13 and mixed to prepare the coating agent 15. The bacterial cell suspension 14 is prepared by centrifuging a culture solution containing live photosynthetic bacteria in advance to remove the supernatant, drying the remaining precipitate (bacterial cells), and then adding water to the precipitate to suspend it. After adding water to the dried bacterial cells, the bacterial cells may be crushed by ultrasonic treatment or the like. In addition, as the "culture solution containing live photosynthetic bacteria", a culture solution of purely cultured photosynthetic bacteria may be used, or a culture solution containing non-purely cultured photosynthetic bacteria as the main constituent microorganisms, which is cultured using shochu lees or the like, may be used.

In addition, instead of the bacterial cell suspension 14, the coating agent 15 may be prepared by adding LPS extracted from photosynthetic bacteria, lipid A extracted from the LPS, or chemically synthesized lipid A to the coating base liquid 13.

Then, plant seeds (e.g., rice seeds) 16 are placed in the coating agent 15 prepared above and soaked for a predetermined time, after which the seeds 16 are removed from the coating agent 15 and dried. The time for soaking the seeds 16 in the coating agent is approximately 1 to 30 minutes, preferably 10 to 20 minutes, but is not limited to this. As a result, coated seeds 17 are obtained, which are seeds covered with a coating layer containing dead photosynthetic bacteria.

The coated seeds 17 obtained in the above manner are transported to agricultural land and sown in the usual manner, either immediately or after being stored for a predetermined period of time. If necessary, the coated seeds 17 may be soaked in water before sowing. Even if the coated seeds 17 get wet, the active ingredients (i.e., photosynthetic bacteria cells, LPS, or lipid A) are retained on the surface of the seeds 16 by the action of the coating base 12 contained in the coating layer. Therefore, even if the coated seeds 17 are soaked in water before sowing or the soil in which the coated seeds 17 are sown is irrigated, these active ingredients are not immediately lost from the surface of the seeds 16.

The seed coating method according to the present embodiment promotes the growth of plant roots after sowing, which improves the efficiency of nutrient and water absorption and promotes the growth of the entire plant. In addition, in the method according to the present embodiment, photosynthetic bacteria (or LPS or lipid A) are administered at the seed stage, which is less time-consuming than traditional field administration such as foliar spraying, irrigation to the roots, or pouring into paddy fields, and the amount of photosynthetic bacteria used is extremely small. In addition, while the method described in the above-mentioned Patent Document 1 required the administration of photosynthetic bacteria to seeds at the agricultural site, the method according to the present embodiment allows the administration of photosynthetic bacteria to seeds (i.e., coating with the coating agent) to be performed industrially in advance at a place other than the agricultural site, for example, at a seed manufacturer. Therefore, the seed coating method according to the present embodiment can be realized without bothering the agricultural workers who sow the seeds. In addition, the seed coating method according to this embodiment does not administer photosynthetic bacteria during the soaking treatment before sowing, as in the method described in Patent Document 1, so it can be suitably applied to plants such as wheat that are generally sown without being soaked in water beforehand.

Below, we explain examples that were carried out to confirm the effects of the present invention. In these examples, coating agents were created by adding cells of the photosynthetic bacterium Rhodobacter sp. Turu3 to aqueous solutions (or suspensions) of various coating bases, and rice seeds coated with each coating agent were sown to evaluate the degree of root growth.

First, Rhodobacter sp. Turu3, a photosynthetic bacterium isolated from paddy field soil in Tsurukui, Sakamoto-cho, Yatsushiro-shi, Kumamoto Prefecture, was cultured in a medium prepared using Kuma shochu lees as a raw material, as described in Non-Patent Document 4. The medium containing the photosynthetic bacterium cells was then centrifuged to collect the precipitate (cells), which was then dried at 60°C for 6 hours to obtain dried cells (dead cells). Water was then added to the dried cells, and the cells were disrupted by ultrasonic treatment to obtain a disrupted cell solution.

Next, three types of gelling agents were prepared as coating bases: starch (derived from wheat), sodium carboxymethylcellulose (Nacalai Tesque, Inc.), and polyvinyl alcohol (Fujifilm Wako Pure Chemical Industries, Ltd.). Each gelling agent was added to water, and then heated to 80°C to dissolve (or disperse) the gelling agent in water, thereby preparing an aqueous solution (or suspension) containing each gelling agent at a concentration of 2%. Then, after cooling the aqueous solution (or suspension) of each gelling agent, a predetermined amount of the cell disruption liquid was added to prepare a coating agent containing the photosynthetic bacteria at a concentration of 10 ³ bacteria/mL and a coating agent containing the photosynthetic bacteria at a concentration of 10 ⁵ bacteria/mL. In preparing the coating agents, the absorption of carotenes was measured at a wavelength of 450 nm, and the bacterial concentration was calculated assuming that OD ₄₅₀ = 2 was 10 ⁹ bacteria/mL.

Next, dried rice seeds (variety: Akitakomachi, production year: 2021) were immersed in each of the above coating agents for 15 minutes, then removed and naturally dried for 1 hour to create coated seeds. As a control, rice seeds were coated with a coating agent that did not contain photosynthetic bacterial cells (i.e., an aqueous solution or suspension containing each of the above gelling agents at a concentration of 2%).

Each of the coated seeds obtained above was sown one seed per cell in 25 central holes (5 x 5) of a 49-hole (7 x 7) seedling cell box (external dimensions 285 mm x 285 mm x 35 mm, internal dimensions of cell hole 36.7 mm x 36.7 mm x 7 mm) containing Promix BX (Premier Tech Horticulture Ltd, QC, Canada) as culture medium. The seeds were cultivated at 25°C for 14 days under 12 hours of light and 12 hours of darkness, after which root growth was evaluated.

The image analysis system WinRHIZO (Regent Instruments Inc.) was used to evaluate root growth. Specifically, water was first poured into a WinRHIZO tray, the soil was removed from the roots growing from the seed rice, the roots were spread out, and an A4 flatbed scanner (EPSON GT-X980) was used to capture an image of the roots. The captured root images were then analyzed with WinRHIZO to evaluate the total root length, root surface area, number of root tips (total number of roots), and number of root branches. Three seeds were used for the evaluation in each section.

The results of the above test are shown in Figures 2 to 4. Figure 2 shows the results when starch was used as the coating base, Figure 3 shows the results when sodium carboxymethylcellulose was used as the coating base, and Figure 4 shows the results when polyvinyl alcohol was used as the coating base. As is clear from these figures, when any of the above coating bases was used, the total root length, root surface area, number of root tips, and number of root branches generally increased compared to the control at both the photosynthetic bacteria concentrations of ¹⁰³ bacteria/mL and ¹⁰⁵ bacteria/mL, confirming that root growth was promoted.

In this example, a coating agent containing cells of the photosynthetic bacterium Rhodobacter sphaeroides NBRC 12203 ^T and a coating agent containing LPS derived from the photosynthetic bacterium were prepared, and the degree of root growth of rice seeds coated with each coating agent was evaluated.

The photosynthetic bacteria Rhodobacter sphaeroides NBRC 12203 ^T was obtained from the National Institute of Technology and Evaluation, and pure cultured using SA Medium (NBRC Medium No. 360) designated by the same organization. The medium containing the photosynthetic bacteria was then centrifuged to collect the precipitate (bacteria), which was then dried at 60 ° C for 6 hours to obtain dried bacteria (dead bacteria). Water was then added to the dried bacteria, and the bacteria were disrupted by ultrasonic treatment to obtain a cell disruption solution. In addition, when preparing the coating agent described below, the turbidity OD ₆₆₀ at a wavelength of 660 nm was measured, and the bacterial concentration was calculated assuming that OD ₆₆₀ = 1 is 10 ⁹ bacteria/mL. In addition, the commercially available LPS derived from Rhodobacter sphaeroides NBRC 12203 ^T (LPS-RS, sold by Invivogen) was used as the LPS.

The coating agent according to this example was prepared by adding the dried cells of Rhodobacter sphaeroides NBRC 12203 ^T or the LPS to a 2% suspension of starch prepared in the same manner as in Example 1. The concentration of the cells in the coating agent was 1 cell/mL or ¹⁰² cells/mL, and the concentration of LPS in the coating agent was 5 pg/mL or 50 pg/mL.

Rice seeds were coated with the coating agent obtained above in the same manner as in Example 1. As a control, seeds were coated in the same manner using a coating agent that did not contain photosynthetic bacteria (i.e., the above-mentioned 2% suspension of starch). Each of the resulting coated seeds was then sown and cultivated in the same manner as in Example 1, and the degree of root growth 14 days after sowing was evaluated. The number of seeds used for evaluation was 4 for each group.

The results of the above test are shown in Figures 5 and 6. Figure 5 shows the results when seed rice was coated with a coating agent containing Rhodobacter sphaeroides NBRC 12203 ^T cells, and Figure 6 shows the results when seed rice was coated with a coating agent containing LPS derived from the same strain. As is clear from these figures, when the coating agent containing Rhodobacter sphaeroides NBRC 12203 ^T cells at a concentration of 1 cell/mL or ¹⁰² cells/mL was used, and when the coating agent containing LPS derived from the same strain at a concentration of 5 pg/mL or 50 pg/mL was used, the total root length, root surface area, number of root tips, and number of root branches were increased compared to the control, confirming that root growth was promoted.

In this example, a coating agent containing lipid A derived from the LPS of photosynthetic bacteria was prepared, and the degree of root growth of rice seeds coated with the coating agent was evaluated.

First, lipid A was obtained by acid hydrolysis of LPS derived from the same Rhodobacter sphaeroides NBRC 12203 ^T as in Example 2. The acid hydrolysis was carried out by heating the LPS in 0.1 N hydrochloric acid at 100° C. for about 1 hour.

Next, a starch suspension was prepared in the same manner as in Example 1 (except that the concentration of starch in the suspension was 1%), and the lipid A was added to the suspension to prepare the coating agent of this example. The concentration of lipid A in the coating agent was 1 pg/mL or 1 ng/mL.

Rice seeds were coated with the coating agent obtained above in the same manner as in Example 1. As a control, rice seeds were coated in the same manner using a coating agent that did not contain lipid A (i.e., the above-mentioned 1% suspension of starch). Each of the resulting coated seeds was then sown and cultivated in the same manner as in Example 1, and the degree of root growth 14 days after sowing was evaluated. The number of rice seeds used for evaluation was 5 for each group.

The results of the above test are shown in Figure 7. As is clear from the figure, when either the coating agent containing lipid A at a concentration of 1 pg/mL or 1 ng/mL was used, the total root length, root surface area, number of root tips, and number of root branches increased compared to the control, confirming that root growth was promoted.

[Aspects]
It will be apparent to those skilled in the art that the above-described exemplary embodiments are illustrative of the following aspects.

(1) The coated seed according to paragraph 1 is
Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing photosynthetic bacteria and a coating base;
It has the following.

(2) The coated seeds according to the 2nd paragraph are
Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing a lipopolysaccharide derived from photosynthetic bacteria and a coating base;
It has the following.

(Clause 3) The coated seeds according to clause 3 are
Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing lipid A and a coating base;
It has the following.

(4) The coated seed according to paragraph 4 is a coated seed according to any one of paragraphs 1 to 3,
The photosynthetic bacteria are characterized in that they are purple non-sulfur bacteria.

(5) The coated seed according to the 5th paragraph is the coated seed according to the 4th paragraph,
The purple non-sulfur bacterium is characterized in that it is a bacterium of the genus Rhodobacter.

(6) The coated seed according to paragraph 6 is the coated seed according to paragraph 5,
The bacterium of the genus Rhodobacter is characterized in that it is Rhodobacter sphaeroides.

(Clause 7) The coated seed according to clause 7 is the coated seed according to any one of clauses 1 to 6, characterized in that the coating base is a gelling agent.

(Item 8) The seed coating agent according to item 8 is
The coating composition is characterized by containing photosynthetic bacteria cells and a coating base.

(Item 9) The seed coating agent according to item 9 is
It is characterized by containing lipopolysaccharide derived from photosynthetic bacteria and a coating base.

(Item 10) The seed coating agent according to item 10,
It is characterized by containing lipid A and a coating base.

(Item 11) The seed coating method according to item 11 comprises:
The seed coating agent according to any one of claims 8 to 10 is applied in a liquid state to the surface of a plant seed, and then the coating agent is dried.

11... Water 12... Coating base 13... Coating base liquid 14... Bacterial cell suspension 15... Coating agent 16... Seeds 17... Coated seeds

Claims (11)

Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing photosynthetic bacteria and a coating base;
The coated seeds have Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing a lipopolysaccharide derived from photosynthetic bacteria and a coating base;
The coated seeds have Plant seeds and
a coating layer formed on the surface of the seed, the coating layer containing lipid A and a coating base;
The coated seeds have The coated seed according to any one of claims 1 to 3, wherein the photosynthetic bacteria are purple non-sulfur bacteria. The coated seed according to claim 4, wherein the purple non-sulfur bacterium is a bacterium of the genus Rhodobacter. The coated seed according to claim 5, wherein the bacterium of the genus Rhodobacter is Rhodobacter sphaeroides. The coated seed according to any one of claims 1 to 3, wherein the coating base is a gelling agent. A seed coating agent containing photosynthetic bacteria cells and a coating base. A seed coating agent containing lipopolysaccharide derived from photosynthetic bacteria and a coating base. A seed coating agent containing lipid A and a coating base. A seed coating method comprising applying the seed coating agent according to any one of claims 8 to 10 in a liquid state to the surface of a plant seed, and then drying the coating agent.

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