JP6736342B2 - Method for sterilizing grain seeds - Google Patents

Description

The present invention relates to a method for sterilizing grain seeds. More specifically, it relates to a method for sterilizing grain seeds for the purpose of controlling grain seed infectious disease fungi.

Rice, wheat, barley, etc. are listed as the major grains in Japan. Among them, rice (paddy rice) has become a standard for box-raised seedlings due to the spread of mechanical transplantation at the seedling raising stage, and with this, obstacles such as dead seedlings and poor growth of the seedlings are increasing. The basic measure against diseases that occur during the seedling raising period is to grow healthy seedlings through proper management such as temperature, water, and acidity correction of bed soil, and the first measure is to prevent disease.

Examples of diseases of box-raised seedlings include seed-borne blast, bacillus seedling disease, rice bacterial blight, seedling bacterial blight, and soil-borne seedling blight, mullet seedlings, etc. .. In particular, in order to prevent the occurrence of seed-borne diseases, it is important to perform appropriate control (sterilization/disinfection) at the seed stage before germination. Chemical pesticides used for sterilizing and disinfecting seeds include Momiguard C/DF, Sumithion emulsion, Sportac emulsion, Trifmine wettable powder, Herseed wettable powder, Sturna wettable powder, Spartac Stana SE, Techreed C Flowable, etc. ..

In addition, as a sterilization treatment other than chemical pesticides, hot water treatment in which rice seeds are soaked in hot water at 60°C for 10 minutes before soaking, and Eco-Hope, Eco-Hope DJ, Tough block, Momigenki wettable powder, Momi-Hope hydration Examples of the control method include biological pesticides such as agents.

However, all of these control methods have problems. Although chemical pesticides have a remarkable bactericidal effect, it is necessary to pay attention to how they are handled and discarded. Some agricultural areas are instructing and regulating to reduce the usage (quantity/type) from the health and environmental aspects. At present, there are few chemical pesticides effective against bacteria. Furthermore, it cannot be overlooked that a resistant bacterium emerges after a certain period of use.

Hot water treatment and biological pesticides are safe and easy to handle in this respect. However, the bactericidal effect including the application range is not as remarkable as that of chemical pesticides, and it is difficult to expect a sufficient controlling effect in the state where a disease is/is likely to occur.

In addition, seed-infectious diseases have also become a problem in wheat and barley. In particular, there is no effective control means for black rot disease, and this also requires early establishment of a control method.

On the other hand, in recent years, peracetic acid preparations have been widely used as bactericides, and their amounts have been increased. The peracetic acid preparation is prepared by appropriately mixing hydrogen peroxide and acetic acid and producing peracetic acid by their chemical equilibrium reaction, and contains peracetic acid, hydrogen peroxide, acetic acid and water as components. For strongly resistant spores, peracetic acid preparations are more effective than hydrogen peroxide, which has been used for sterilization due to its oxidizing action, that bactericidal power does not decrease like chlorine even in the presence of organic matter, and Has a sterilization mechanism that irreversibly oxidatively denatures essential biomolecules such as enzymes and DNA, so that resistant bacteria are unlikely to appear, sterilizing agents for PET bottles for beverages, medical endoscopes Its use is expanding as a disinfectant and a disinfectant cleaner in food factories that handle Bacillus natto.

Another feature of this peracetic acid preparation is the ease of treatment after use. Peracetic acid preparations become acetic acid (salt), which is easily biodegradable with water and oxygen over time or by adjusting pH, etc. Conceivable.

Several attempts have already been made to apply peracetic acid preparations having such characteristics to the agricultural field. A method for controlling rice diseases by treating rice seeds before soaking and before/after germination with a peracetic acid concentration of 200 to 1000 ppm for 60 minutes to 24 hours has been reported (Patent Document 1). In addition, a method of sterilizing microorganisms by causing nascent atomic oxygen generated by exposing peroxides such as peracetic acid to energy sources to seeds such as rice and agricultural products such as roots, shells, fruits and flowers (Patent Document 2) has been reported.

JP, 1995-258005, A Special table 2005-514169 gazette

Maintaining stable production of rice both in terms of quality and quantity is the most important issue in Japanese agriculture, and the control of pests related to rice cultivation is a key factor. In controlling the pests and diseases of such rice cultivation, rice seed sterilization has a great role to play, and there is a demand for bactericides and methods that are more effective, safe, and easier to handle. In addition, wheat and barley are also indispensable grains in Japanese dietary habits nowadays, and in the current situation of being reevaluated from the viewpoint of safety and domestic self-sufficiency, stable production by controlling pests is important. Is increasing.
The present invention provides a method for sterilizing these grain seeds, which is free from phytotoxicity in the germination rate of seeds, is efficient, and has an excellent bactericidal effect.

The present inventors have achieved the present invention as a result of earnest efforts. That is, the present invention, a peracetic acid formulation containing peracetic acid in an appropriate concentration range, for a practical time in agricultural work, rice, wheat, used for sterilization treatment of grain seeds such as barley, adheres to the grain seeds By killing the pathogenic bacteria and then removing peracetic acid by washing with water, the chemical damage such as a lower germination rate to grain seeds due to peracetic acid can be reduced, and the healthy growth of grain seeds such as rice, wheat, and barley can be achieved. I will get it.

That is, the present invention has the following configuration.

[1] A method for sterilizing a grain seed, which comprises treating the grain seed with a peracetic acid preparation and then washing with water.
[2] A method for sterilizing grain seeds, which comprises washing with water within 15 minutes after the treatment with the peracetic acid preparation.
[3] A method for sterilizing grain seeds, wherein the pH value of grain seeds is 5.0 or more and 9.0 or less after washing with water.
[4] The treatment with the peracetic acid preparation is characterized in that the concentration (ppm) of the peracetic acid contained and the treatment time (min) are integrated to be 5000 (ppm·min) to 300,000 (ppm·min). Method for sterilizing grain seeds.
[5] In the treatment with the peracetic acid preparation, the concentration of peracetic acid contained in the peracetic acid preparation is 1000 ppm to 100000 ppm, and the treatment time is 1 minute to 30 minutes. ..

In the present invention, by immersing grain seeds in a peracetic acid preparation solution, a sufficient bactericidal effect against disease fungi that contaminate grain seeds, for example, filamentous fungi and bacteria, and resistant bacteria are less likely to appear. Sterilization treatment with a peracetic acid formulation under the treatment conditions of the present invention, and the sterilization treatment method of the grain seeds for carrying out the subsequent water washing treatment have a practical time in the agricultural work scene, an advantage of convenient operation, and further, the grain seeds. The infectious disease fungus can be efficiently killed, and the sufficient germination ability of grain seeds can be maintained, so that healthy grains such as rice, wheat, and barley can be cultivated.

Hereinafter, the present invention will be described in detail.
The peracetic acid preparation of the present invention can be prepared by mixing hydrogen peroxide and acetic acid. The concentration and amount of hydrogen peroxide and acetic acid to be used may be appropriately selected based on the known equilibrium constant of peracetic acid according to the concentration of peracetic acid to be obtained. When hydrogen peroxide and acetic acid are mixed, stirred, and allowed to stand at room temperature for several days, peracetic acid is produced by a chemical equilibrium reaction between the two, and a peracetic acid preparation is prepared.

The peracetic acid preparation thus obtained is used as it is or after being diluted so that the peracetic acid concentration becomes appropriate. The bactericidal effect of peracetic acid preparations depends on the concentration of peracetic acid, treatment time, temperature, and the type of disease-causing bacteria or molds to be targeted, so the appropriate concentration, treatment time, and treatment temperature are set in consideration of them. There is a need.

This is due to the sterilization mechanism of peracetic acid contained in the peracetic acid preparation. Peracetic acid, which is highly permeable to living organisms and has strong oxidizing power, irreversibly alters or inactivates the essential elements of life-sustaining activities such as membranes, enzymes, and DNA of pathogenic bacteria by oxidization, resulting in high bactericidal efficiency. Difficult to produce drug-resistant bacteria. However, if the residual liquid is left adhering to the grain seeds after soaking in the peracetic acid preparation, the germination is suppressed due to the penetration into the grain seeds or the action on the germinated sprouts, etc. There is a risk of damage to germination rate.

The concentration of peracetic acid generally used is 1000 ppm to 100000 ppm, preferably 5000 ppm to 50000 ppm, and more preferably 5000 ppm to 20000 ppm. If the concentration is less than 1000 ppm, long-time treatment is required to obtain a sufficient bactericidal effect. There is a possibility that a sufficient bactericidal effect may not be obtained within a practical time for farmers. If the concentration exceeds 100,000 ppm, grain seed germination may be inhibited even if the treatment is performed for a short time.

The treatment time with the peracetic acid preparation varies depending on the temperature conditions and the peracetic acid concentration, but generally, the lower the peracetic acid concentration, the longer the sterilization treatment time needs to be. Considering practicality, the sterilization treatment time is preferably 1 minute to 30 minutes, more preferably 5 minutes to 30 minutes, and particularly preferably 5 minutes to 20 minutes.

Further, in consideration of the influence on the germination rate of seeds, it is necessary to shorten the sterilization treatment time as the concentration increases. For example, a sterilization treatment for 30 minutes or longer at a peracetic acid concentration of 10000 ppm causes phytotoxicity in germination of seeds, and thus a sterilization treatment for 30 minutes or longer is not preferable.

Therefore, it is necessary to consider the overall effect of peracetic acid concentration and sterilization treatment time, taking into consideration both the bactericidal activity and the effect on germination rate. The lower the peracetic acid concentration, the longer the sterilization treatment time is desirable in order to maintain the sterilizing power. Conversely, the higher the concentration of peracetic acid, the shorter the sterilization time is required to reduce the effect on germination rate.

Here, the integrated effect of the peracetic acid concentration and the sterilization treatment time can be evaluated by setting the total of the peracetic acid concentration and the sterilization treatment time as one amount. Accumulation of peracetic acid concentration (ppm) and sterilization time (min) of peracetic acid preparation is 5000 (ppm·min) or more and less than 300,000 (ppm·min), preferably 5000 (ppm·min) to 200,000 (ppm·min) , And more preferably 10,000 (ppm·min) to 150,000 (ppm·min).

When treating with a peracetic acid preparation, if the peracetic acid concentration and the sterilization treatment time exceed 300,000 (ppm/min), the germination of grain seeds will be significantly impaired, and the germination rate may be less than 50%. Cannot secure a good germination rate.

On the other hand, in practical situations, it is preferable that the germination rate is as high as possible.However, in rice cultivation using grain seeds, especially rice seeds, if a significant number of pathogens survive, the subsequent work step (for example, soaking).・Emergence of seeds and seedlings may spread due to germination treatment, nursery box raising, etc.), resulting in a significant decrease in yield. Therefore, it is necessary to carry out under conditions that can surely kill the pathogenic bacteria while ensuring a sufficient germination rate. Therefore, in order to ensure the minimum bactericidal activity, the lower limit of the integration of the peracetic acid concentration (ppm) of the peracetic acid preparation and the sterilization treatment time (minute) is 5000 (ppm·minute), more preferably 10,000 (ppm·minute). It is necessary to set the peracetic acid concentration and the sterilization treatment time so that

The temperature during sterilization is also an important factor, and generally, the higher the temperature of a peracetic acid preparation, the stronger the bactericidal activity. However, too high a temperature will cause more damage to the grain seeds. Ultimately, it must be determined by the balance between the concentration of peracetic acid and the sterilization treatment time, but the treatment temperature is preferably 10°C to 70°C, and particularly preferably 20°C to 35°C.

Examples of the method for sterilizing grain seeds with the peracetic acid preparation of the present invention include dipping treatment, dressing treatment (slurry treatment), spraying treatment (spraying treatment), and the like. The dipping treatment is more preferable because it is the point that the bactericidal effect is exhibited by sufficiently permeating the active ingredient into the pathogenic bacteria lurking in the seed coat having unevenness or water repellency.

In the method for sterilizing treatment with a peracetic acid preparation of the present invention, seeds may be dipped in the peracetic acid preparation as they are, or may be put in a cloth bag, a net or the like for treatment. In particular, in the case of high-concentration treatment for a short time, it is necessary to take it in and out quickly from the peracetic acid preparation liquid. In that case, considering the drainage property, put it in a coarse mesh like a net and treat it. It is preferable to carry out.

After sterilization with a peracetic acid preparation, clean water such as tap water is quickly washed. The higher the concentration of peracetic acid, the earlier the water washing treatment after the sterilization treatment is, and the less the influence on the germination rate of seeds is. Therefore, it is desirable to perform the water washing treatment as early as possible. From the time when the sterilization treatment of the peracetic acid preparation is completed, the water washing treatment is preferably started within 15 minutes at the latest, more preferably the water washing treatment is started within 10 minutes, and the water washing treatment is performed within 5 minutes. It is even more preferable to start.

In water washing after sterilization treatment with a peracetic acid preparation, it is preferable to remove the peracetic acid preparation adhering to the seeds or entering the seed coat so that the concentration of peracetic acid remaining in the seeds becomes zero as much as possible. However, for the confirmation, it is very difficult to measure the concentration of peracetic acid remaining in the seeds in the actual agricultural work scene. As a simple method, there is a method of measuring the pH value of the seed after the water washing treatment with a pH test paper and evaluating the concentration of peracetic acid remaining in the seed.

In general, the standard pH value of tap water is 5.8 or more and 8.6 or less, and a pH value of around 7 is suitable, so that the pH value of seeds after washing is 5. When it is 0 or more and 9.0 or less, more preferably 5.8 or more and 8.6 or less, and further preferably around 7, it may be judged that the peracetic acid preparation was sufficiently washed and removed from the seed. When washing with water after sterilization with a peracetic acid preparation, washing with a sufficient amount of water and washing time so that the pH value is 5.0 or more and 9.0 or less, more preferably 5.8 or more and 8.6 or less. This is desirable, and more preferably, washing with running water. Water must be relatively clean, such as tap water, well water, and river water without pollution. When seeds are placed in a net bag or the like and washed with water, it is necessary to take care so that the seeds inside are also thoroughly washed with water. A more preferable washing method is a method in which seeds are roughly washed while still in the net, and then the seeds are transferred from the net to another container and washed with running water.

When the sterilization treatment with the peracetic acid preparation of the present invention is carried out, the seeds of rice, in particular, can be subsequently subjected to the seeding treatment and the germination treatment so as to germinate and raise the seedlings soundly. The control value is used to evaluate the bactericidal effect of peracetic acid. The control value is an index showing the degree of control effect of the treated area against the damage of pests in the untreated area, and is generally calculated by (100−(damage of treated area/damage of untreated area)×100). The higher the control value is, the more effective the control is. It is shown that if the control value is 50 or more, a reliable bactericidal effect can be obtained.

Since the peracetic acid preparation becomes acetic acid (salt) that is easily biodegradable with water and oxygen over time or by adjusting the pH, it is easy to handle in terms of environment and health. Therefore, peracetic acid preparations that have been used for sterilization should be neutralized with an alkaline agent such as caustic soda, reduced peracetic acid and hydrogen peroxide with sodium sulfite, sodium thiosulfate, etc., and then discarded in general sewage. You can

Examples of the present invention will be shown below.
As the peracetic acid preparation, Oxyper 100 (product name, Hodogaya Chemical Co., Ltd.) was used. The peracetic acid concentration of this drug was 100,000 ppm (10%), and this was diluted to each concentration and immediately tested as a working solution.

(Inhibition of germination of grain seeds by residual peracetic acid)
Oxyper 100 was diluted 10-fold (10000 ppm peracetic acid) and 100-fold (1000 ppm peracetic acid), and 96 seeds of wheat and barley were soaked for 60 minutes at 20° C., then these seeds were taken out and washed with water as they were. No, the pH value of the seeds was measured using pH test paper. The pH value was 2-3 acidic. The seeds were air dried and placed on an agar plate. The temperature was kept at 25°C for 7 days, and the germination rate was confirmed. The results are shown in Table 1.

The results in Table 1 show that when the water washing treatment after the sterilization treatment with the peracetic acid preparation is not carried out, neither the wheat seed nor the barley seed germinates by the sterilization treatment of the peracetic acid concentration of 10,000 ppm for 60 minutes. Further, even when the peracetic acid concentration is 1000 ppm, it is shown that the germination rate of the grain seeds is reduced by 30% to 40% by the sterilization treatment for 60 minutes as compared with the non-sterilized treatment. These results indicate that if the peracetic acid preparation remains as it is in the seed without washing with water after the sterilization treatment, the germination rate of the seed is obviously reduced due to the chemical damage.

(Effect of treatment time with peracetic acid on germination rate of rice seeds)
Oxipale 100 was diluted 10 times to prepare a peracetic acid preparation having a peracetic acid concentration of 10000 ppm. 300 seeds of rice seed (Koshihikari) were immersed in this peracetic acid preparation at room temperature for 1 to 30 minutes, and then washed twice with sterile water. When the pH value of the washed rice seeds was measured with a pH test paper, the pH value was 6 to 7. These rice seeds were immersed in water at 25° C. for 4 days, placed on an agar medium and kept at 30° C. for 4 days, and the germination rate was confirmed. The results are shown in Table 2.

In Comparative Example 3, when the peracetic acid preparation having a peracetic acid concentration of 10000 ppm was subjected to immersion treatment of rice seeds for 30 minutes or longer, the germination rate of rice seeds fell to 50% or less even after water washing treatment. It was shown that such germicidal treatment (10000 ppm×30 minutes) causes phytotoxicity on the germination rate of rice seeds. On the other hand, from Example 2, if the rice seeds were sterilized (10000 ppm×10 minutes) for 10 minutes with the same concentration of peracetic acid preparation and washed with water, the germination rate of rice seeds could be maintained at 90% or more. it can. In the method of sterilizing treatment with a peracetic acid preparation of the present invention, since no phytotoxicity is caused in germination of seeds, it is necessary to comprehensively consider the influences of the two factors of peracetic acid concentration and sterilization treatment time.

(Sterilizing effect by treatment with peracetic acid preparation)
Rice seeds (Koshihikari) were artificially infected with pathogenic bacteria by the vacuum infection method to prepare disease-infected seeds. As the disease-causing bacteria, Pseudomonas glumae, Pseudomonas avenae Manns 1909, and Pseudomonas plantarii were used. In addition, for Gibberella fujikuuroi, naturally infected Becoa ova was used. Wheat seeds and barley seeds were infected with wheat black rot (Pseudomonas syringae pv. Japanica) to prepare seeds infected with the disease fungus.

Oxipale 100 was diluted 10 times, and the infected seeds were immersed in a peracetic acid solution having a peracetic acid concentration of 10000 ppm for 10 minutes, and after 5 minutes, water washing was performed and washing with running water was performed for 10 minutes. The pH value of the washed rice seeds was about 7.0 to 8.0 measured using pH test paper.

These rice seeds were soaked and germinated, sown in a soil, and after raising seedlings, the disease degree (control value) of each 200 seedlings was confirmed. As for the seeds of barley and wheat, 96 seeds each were sown as they were in a medium and germinated to confirm the disease degree (control value). The results are shown in Table 3. The sterilization method before seed soaking according to the present invention showed that bacillus seedling disease has a bactericidal effect of about 100% (control value is 99). It was also confirmed that there is a sure bactericidal effect (control value is 50 or more) against rice bacterial blight, rice brown stripe, rice seedling bacterial blight and wheat black rot.

In the sterilization treatment of cereal seeds using a peracetic acid preparation, it is very important that the seeds are immersed in a peracetic acid agent and then rapidly washed with water in order not to cause phytotoxicity on the germination rate of the seeds. In addition, selection of appropriate sterilization treatment conditions in treatment concentration and time of peracetic acid is also a very important factor in preventing phytotoxicity on the germination rate of seeds. It is considered appropriate to consider the overall effect of peracetic acid concentration and sterilization treatment time by using the integration of peracetic acid concentration and sterilization treatment time. As a sterilization method of grain seeds according to the present invention, the pH value of the seeds is quickly obtained after the sterilization treatment in which the integration of the peracetic acid concentration and the sterilization treatment time is within the range of 5000 (ppm·min) or more and 300,000 (ppm·min) or less. If the water washing treatment is performed so that the ratio is 5.0 or more and 9.0 or less, the disease fungus adhering to the grain seeds can be effectively sterilized, and phytotoxicity to the germination rate of the seeds can be prevented.

The method for sterilizing grain seeds with the peracetic acid preparation of the present invention is a simple and convenient method for sterilizing grain seeds in an actual agricultural work scene, and is effective for controlling seed infectious diseases while maintaining the germination rate of grain seeds. It is a very effective method of controlling. It is particularly suitable for pre-soaking sterilization treatment of rice seeds. Furthermore, handling is a safe sterilization method in terms of environment and health.

Claims (4)

A method for sterilizing a grain seed, which comprises treating the grain seed by immersing it in a peracetic acid preparation and then washing with water ,
In the treatment with the peracetic acid preparation, the concentration of peracetic acid contained in the peracetic acid preparation is 5000 ppm to 100000 ppm, and the treatment time is 1 minute to 30 minutes,
The treatment with the peracetic acid preparation is performed so that the concentration of peracetic acid (ppm) and the treatment time (min) are integrated to be 5000 (ppm·min) to 150,000 (ppm·min).
A method for sterilizing grain seeds, wherein the water washing is carried out within 5 minutes after the treatment with the peracetic acid preparation and the pH value of the grain seeds after water washing is 5.8 or more and 8.6 or less. The method for sterilizing a grain seed according to claim 1, wherein the treatment is performed at a temperature of the peracetic acid preparation of 20°C to 35°C. The method for sterilizing grain seeds according to claim 1 or 2, wherein the water washing is performed with running water. The method for sterilizing grain seeds according to any one of claims 1 to 3, wherein the grain seeds are put in a cloth bag or a net to perform the treatment.