JP2022106003A - Sterilization/infection prevention method of seed rice - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent infection of seed rice sterilized by using warm water or a weak pesticide free from residual effect.

SOLUTION: In a sterilization/infection prevention method of seed rice in an embodiment, seed rice is sterilized by using warm water or a weak pesticide free from residual effect, and after sterilization, seed soaking and forced sprouting are performed by using hypochlorous acid water, to thereby prevent microbial or bacterial infection to the seed rice.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

Application for application of Article 30, Paragraph 2 of the Patent Act has been made. Presented at the 2017 Phytopathological Society of Japan Conference hosted by the Phytopathological Society of Japan

An embodiment of the present invention relates to a method for sterilizing seed paddy and preventing infection.

Disinfection methods for seed paddy include pesticides and hot water sterilization with hot water at around 60 ° C. From the viewpoint of food safety, it is desirable to sterilize with hot water rather than pesticides with high residual effect.

However, in recent years, the outbreak of idiot seedling disease has been reported when raising seedlings of seeds sterilized with hot water.

In hot water sterilization, since the treatment is performed at a temperature near the boundary that damages the seed paddy, it may not be possible to completely sterilize due to variations in the number of bacteria possessed and variations in the sterilization treatment. If the paddy that has been sterilized with hot water remains inadequately sterilized, there is a problem that the seed paddy is secondarily infected with the healthy paddy when the seed paddy is soaked in the soaking and sprouting process.

In sterilization using pesticides, secondary infections are less likely to occur when pesticides with strong residual effects are used, but when low pesticides with no residual effects are used, they are used during soaking and germination. There is a problem of secondary infection with healthy paddy.

Japanese Unexamined Patent Publication No. 2008-328723 Japanese Unexamined Patent Publication No. 2003-23815

An object of the present invention is to prevent infection in the seed soaking and germination steps of seeds sterilized with hot water or low pesticides having no residual effect.

According to the embodiment, in the seeding and sprouting process for raising seedlings sterilized with hot water or low pesticides having no residual effect, hypochlorite water is used as an immersion liquid to obtain healthy seeds. A method for sterilizing and preventing infection of seed paddy for the purpose of preventing infection with bacteria.

It is a flow chart which shows the sterilization and infection prevention method of the seed paddy which concerns on embodiment. It is a schematic diagram which shows an example of the exchange method of hypochlorite water in an embodiment. It is a schematic diagram which shows another example of the exchange method of hypochlorite water in an embodiment. It is a schematic diagram which shows another example of the exchange method of hypochlorite water in an embodiment. It is a schematic diagram which shows another example of the exchange method of hypochlorite water in an embodiment.

Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 shows a flow chart showing a method for sterilizing and preventing infection of seeds according to an embodiment. In the seedling raising process, seed disinfection, soaking, germination, and emergence treatment are performed to raise seedlings. As shown in the figure, the method for sterilizing and preventing infection of seed rice according to the embodiment is to sterilize the seed rice using hot water or a low pesticide having no residual effect (S1), and after sterilization, use hypochlorite water. By soaking with seeds (S2) and sprouting with hypochlorite water (S3), infection of seeds can be prevented.

Here, the hot water means water at around 60 ° C. or hypochlorite water at around 40 ° C.

In FIG. 1, hypochlorite water is used in both the soaking and sprouting steps, but the present invention is not limited to this, and either soaking or sprouting may be used.

Here, the hot water refers to water at around 60 ° C., for example, 58 ° C. to 62 ° C., or hypochlorite water at around 40 ° C., for example, 38 ° C. to 42 ° C.

According to the embodiment, by using hypochlorite water as the soaking solution for soaking and / or sprouting, infection to healthy paddy can be suppressed. In addition, the use of hypochlorite water suppresses the growth of microorganisms and other germs and has the effect of deodorizing, so that discomfort during work can be reduced.

Hypochlorite water is obtained by electrolyzing an aqueous solution of potassium chloride in a diaphragmatic electrolytic cell, electrolyzing the aqueous solution obtained from the anode side or hydrochloric acid in a non-diabolic electrolytic cell, and diluting it with water suitable for drinking. The obtained aqueous solution. In the embodiment, hypochlorite water having a pH of 6.5 or less and an effective chlorine concentration of 10 to 60 mg / kg can be used. Such hypochlorite water can be used as a specific control material (specific pesticide).

The bath ratio of hypochlorite water to the seed paddy can be 2 to 10 in terms of volume ratio (volume ratio). If the bath ratio is less than 2, the effective chlorine concentration cannot be maintained and the secondary infection rate tends to increase. Further, when the bath ratio exceeds 10, hypochlorous acid is excessively supplied to the seed paddy, and the risk of growth failure tends to increase.

In order to introduce it to the site, it is desirable to replace the soaking liquid at the time of soaking and sprouting with hypochlorite water from the conventionally used tap water, and the bath ratio should be within 2 to 5 by volume ratio (volume ratio). It is considered easy to use.

On the other hand, in order to prevent infection, it is more effective to maintain the effective chlorine concentration of hypochlorite water above a certain value. When the bath ratio is low, the effective chlorine concentration decreases quickly, and it tends to be difficult to maintain the required concentration.

The dipping solution preferably maintains an effective chlorine concentration of 7 mg / kg or more from the start of immersion to 70 hours for soaking, and an effective chlorine concentration of 7 mg / kg or more until the end of germination. If the effective chlorine concentration is less than 7 mg / kg, it tends to be difficult to prevent the infection of seed paddy.

In addition, the soaking solution is more effective in preventing infection when the hypochlorite water is replaced at least once in the soaking or sprouting step.

For example, infection during the process can be prevented by exchanging the entire amount of hypochlorite water once in 7 days of soaking and once before sprouting at the same frequency as the conventional tap water exchange.

Furthermore, it is desirable that the soaking and sprouting steps be carried out in a closed space covered with a lid in order to prevent consumption of hypochlorous acid due to atmospheric release.

Since the amount of decrease in the effective chlorine concentration is smaller in the closed immersion tank than in the open case, the hypochlorite water can efficiently act on the sterilization of the seed paddy. Therefore, the closed immersion tank can obtain a sufficient seed paddy sterilizing effect even with a smaller bath ratio than the open immersion tank.

Furthermore, as a procedure for exchanging the hypochlorite water of the immersion liquid, it is conceivable to replace the entire amount of the hypochlorite water, add or recover the hypochlorite water, or regenerate the immersion liquid. Be done.

To replace the entire amount of hypochlorite water, it is possible to restore the effective chlorine concentration by discharging most of the hypochlorite water and then supplying new hypochlorite water.

When adding hypochlorite water, replace a part of the hypochlorite water with a hypochlorite water having an effective chlorine concentration higher than the effective chlorine concentration of the recorded hypochlorite water. The effective chlorine concentration can be restored.

FIG. 2 shows a schematic diagram showing an example of a method for exchanging hypochlorite water.

In this method, first, as shown in FIG. 2A, for example, the drain valve 5 provided in the drain line 3 of the immersion tank 1 containing the hypochlorite water is opened in advance to hypochlorite. Drain enough water. After that, the drain valve 5 of the drained immersion tank 1 can be closed, the water supply valve 4 of the water supply line 2 can be opened, and new hypochlorite water can be introduced for replacement.

The purpose of exchanging hypochlorite water is to maintain and restore the effective chlorine concentration, except for the method of discharging all the liquid used from the discharge port and discarding it and supplying a new liquid as shown in Fig. 2. There is a method.

3 to 5 show a schematic diagram showing another example of the method for exchanging hypochlorite water.

For example, in the method shown in FIG. 3, the water supply valve 4 and the drain valve 5 are opened, new hypochlorite water is introduced from the water supply line 2, and only the amount of the introduced hypochlorite water is introduced without draining the hypochlorite water in advance. This is a so-called free-flowing method in which the hypochlorite water in use is discharged from the drainage line 3.

Further, in the method shown in FIG. 4, for example, a part of the hypochlorite water in use is recovered, sent from the drainage line 3'to the electrolytic unit 7, and the recovered working liquid is electrolyzed to obtain the effective chlorine concentration. This is a circulation method in which the water is regenerated and returned from the water supply line 2'to the immersion tank 1.

Further, in the method shown in FIG. 5, the electrolysis unit 8 is directly installed in the immersion tank 1, and the electrolysis unit 8 is driven by the controller 9 connected to the electrolysis unit 8 to perform electrolysis, and a new method is performed in the immersion tank. This is a method of keeping the effective chlorine concentration above a certain value by generating hypochlorite water. At this time, the newly supplied hypochlorite water may have the same concentration as the initial one, or a higher concentration of hypochlorite water may be supplied to keep the effective chlorine concentration at a constant value. You may keep the above.

Hereinafter, examples will be shown and embodiments will be described in more detail.

Example 1
Prepare healthy paddy that has been sterilized by hot water for 10 minutes in hot water at 60 ° C. and contaminated paddy that has not been sterilized, and divide the appropriate amount according to the bath ratio into separate nets.

Next, in a dipping tank filled with hypochlorite water, healthy paddy and contaminated paddy placed in a net are immersed in the same dipping tank, and the bath ratio is set to 5 to 40, and the seeding treatment is performed at 10 to 12 ° C. for 7 days. gone. In this embodiment, the immersion tank is an open system without a lid, and the immersion liquid is not replaced for 7 days.

Contaminated paddy is added by 5% by weight of the total amount of healthy seeds and contaminated paddy, and contaminated paddy is seed paddy collected from the ears of seedlings artificially inoculated with idiot seedling disease bacteria at the time of flowering in the previous year.

The effective chlorine concentration of hypochlorite water is 60 mg / kg (pH 6.0), the capacity is 600 ml, and the amount of healthy seeds and contaminated paddy is bath ratio 40, 20, 10, 5 (volume ratio (volume ratio)). It was adjusted to be.

Bath ratio 40 = total amount of paddy (contaminated paddy) = 15 g (0.75 g) (sample 1-2)
Bath ratio 20 = total amount of paddy (contaminated paddy) = 30 g (1.50 g) (Sample 1-3)
Bath ratio 10 = Total amount of paddy (contaminated paddy) = 60 g (3.0 g) (Sample 1-4)
Bath ratio 5 = Total amount of paddy (contaminated paddy) = 120 g (6.0 g) (Sample 1-5)
The infection rate shown below was measured using the seed paddy after soaking.

After 7 days of soaking, the net was taken out and only healthy paddy was evaluated to evaluate the secondary contamination rate. For each bath ratio, 150 seeds of paddy were placed every 50 seeds on a □ 90 mm square Petri dish containing F0-G2 medium at equal intervals, and cultured at a temperature of 25 ° C for 7 to 10 days. The number of colonies in the medium was measured, and the percentage of the number of colonies to 150 grains was taken as the carrier rate.

As a target group for comparison, a group soaked with tap water having a bath ratio of 40 was prepared (Sample 1-1). Except for the dipping solution, the seeds were soaked in the same manner as in the hypochlorite water group, and the infection rate was measured.

The obtained results are shown in Table 1 below.

Compared with the infection rate of 99.6% in the tap water area, which is the target area, infection suppression is seen in the hypochlorite water area. However, even with hypochlorite water, the infection rate is 0% at a bath ratio of 40, whereas the infection rate increases as the bath ratio decreases. It can be seen that the infection rate is 1% or less when the bath ratio is 10 to 40, while the infection rate is increased to 5.3% when the bath ratio is 5. In order to investigate the reaction rate between the infection rate and hypochlorite water, the changes in the effective oxygen concentration with respect to the soaking days are shown in Table 2 below. Further, Table 3 shows the consumption of hypochlorous acid per 1 kg of seed paddy calculated from the effective chlorine concentration.

From the obtained results, it can be seen that the effective chlorine concentration decreases rapidly within 70 hours (3 days) from the start of immersion, that is, the consumption of hypochlorous acid is high. Further, in a bath ratio of 5 having a high infection rate, the effective chlorine concentration becomes 0 70 hours after the start of immersion. Furthermore, looking at the consumption of hypochlorous acid, the contamination rate of healthy seeds is 5% or less because the effective chlorine concentration 70 hours (3 days) after the start of immersion is 7 mg / kg or more, and hypochlorous acid. It can be seen that the acid consumption is in the range of 265 to 530 (mg / kg of seed paddy). The amount of hypochlorous acid consumed (cumulative) can be calculated by obtaining the amount of HClO (mg) from the integration of the amount of decrease in the effective chlorine concentration and the amount of the soaked liquid, and dividing by the amount of soaked paddy (kg).

Example 2
We will examine in more detail the soaking with a bath ratio of 10 or less.

The same soaking treatment as in Example 1 was carried out at bath ratios (volume ratios (volume ratios)) of 10, 5, 3 and 2, respectively. Further, after soaking, the germination treatment was carried out at 30 to 32 ° C. for 20 hours.

In this embodiment, the immersion tank is an open system without a lid, and the immersion liquid is not replaced for 7 days (samples 2-2, 2-3, 2-4, 2-5) and after 24 hours (samples 2-2, 2-3, 2-4, 2-5). After 1 day), the hypochlorite water of the dipping solution was completely replaced (samples 2-6, 2-7, 2-8, 2-9). In the germination step carried out after the soaking, the soaking solution was used as it was.

The effective chlorine concentration of hypochlorite water is 60 mg / kg (pH 6.0), the capacity is 600 ml, and the total amount of healthy seeds and contaminated paddy is bath ratio 10, 5, 3, 2 (volume ratio (volume ratio)). ).

In addition, tap water with a bath ratio of 10 was prepared as the target group (Sample 2-1). Do not change tap water.

Bath ratio 10 = total amount of paddy (contaminated paddy) = 60 g (3.0 g) (samples 2-2, 2-6)
Bath ratio 5 = total amount of paddy (contaminated paddy) = 120 g (6.0 g) (samples 2-3, 2-7)
Bath ratio 3 = total amount of paddy (contaminated paddy) = 200 g (10 g) (samples 2-4, 2-8)
Bath ratio 2 = total amount of paddy (contaminated paddy) = 300 g (15 g) (samples 2-5, 2-9)
The infection rate of the seed paddy after soaking and sprouting was measured in the same manner as in Example 1. Furthermore, for the seed paddy after germination, the seedlings were actually raised by the following method, and the incidence rate of the seedlings was measured.

In the measurement of the incidence rate in raising seedlings, seedlings were raised in seeds after soaking and germination, and the onset of stupid seedling disease 10 to 14 days later was visually observed and evaluated. The number of samples was 20, and the percentage of the number of diseased seedlings to the total number of seedlings was taken as the disease rate.

The obtained results are shown in Table 4 below.

The results of measuring the change in effective oxygen concentration with respect to the number of soaking days once a day are shown in Table 5 below.

In the table, the values one day after the exchange of hypochlorite water are the values before the exchange.

Further, the consumption of hypochlorous acid per 1 kg of seed paddy calculated from the effective chlorine concentration is shown in Table 6 below.

Looking at the infection rate after soaking, without water exchange, the infection rate tends to be high at bath ratios 2 to 5 (samples 2-3, 2-4, 2-5) excluding bath ratio 10 (sample 2-2). Will be. On the other hand, with water exchange, it was confirmed that infection control was possible at a high level with an infection rate of 5% or less in all bath ratios 2 to 5 (samples 2-6, 2-7, 2-8, 2-9). can.

Even when soaking in tap water, the tap water is exchanged during the soaking. Therefore, according to the second embodiment, by exchanging the hypochlorite water during the soaking, the conventional method is performed. It is possible to reduce the infection rate after soaking without particularly increasing the number of steps as compared with the soaking step.

However, looking at the infection rate after sprouting, since the infection rate has increased significantly under all conditions, it is considered more effective to prevent infection not only during inoculation but also during sprouting.

When the transition of the effective chlorine concentration was confirmed, it was confirmed that when the infection rate after soaking was 5% or less, the effective chlorine concentration was 7 mg / kg or more as in Example 1 70 hours after the start of soaking (3 days later). can.

Furthermore, looking at the consumption of hypochlorous acid per 1 kg of seed paddy calculated from the decrease in effective chlorine concentration, the infection rate after soaking is 5% or less after 70 hours (3 days) after the start of soaking. When the consumption of chloric acid is 273 (mg / seed paddy 1 kg) (with water exchange, bath ratio 3), the consumption amount of 260 (mg / seed paddy 1 kg) (without water exchange, bath ratio 5) is not sufficient. You can see that. Therefore, in an open system without a lid, the contamination rate of healthy paddy is 5% or less because the effective chlorine concentration 70 hours (3 days) after the start of soaking is 7 mg / kg or more, and that of hypochlorous acid. The consumption is 270 (mg / 1 kg of seed paddy) or more.

Example 3
For soaked seeds with a bath ratio of 5, we will verify the infection control effect in the presence or absence of a lid for the immersion tank (closed system / open system) and the presence or absence of water exchange during germination.

The same soaking treatment as in Example 1 was carried out at a bath ratio (volume ratio (volume ratio)) of 5, respectively. Further, after soaking, the germination treatment was carried out at 30 to 32 ° C. for 20 hours.

In this embodiment, the immersion tank has an open system without a lid (Sample 3-2) and a closed system with a lid (Sample, 3-3, 3-4, 3-5). The seeding solution was not replaced for 7 days (Sample 3-3), and after 70 hours (3 days), the hypochlorite water of the immersion solution was completely replaced (Sample 3-2, 3-4, 3-5). Divided into. Further, it was divided into the case where sprouting was carried out continuously after soaking (Sample 3-4) and the case where the hypochlorite water was completely replaced before sprouting (Samples 3-2, 3-3, 3-5).

In addition, tap water with a bath ratio of 5 was prepared as the target area (Sample 3-1). The exchange of tap water was carried out at the same time as the exchange of hypochlorite water at the time of soaking and before germination.

The effective chlorine concentration of the hypochlorite water was 60 mg / kg (pH 6.0), the volume was 600 ml, and the amounts of healthy seeds and contaminated paddy were adjusted to a bath ratio of 5.

The infection rate of the seeds after soaking and sprouting was measured in the same manner as in Example 1. Further, in the same manner as in Example 2, the seedlings were raised with seedlings after germination, and the incidence rate of the seedlings was measured.

The obtained results are shown in Table 7 below.

The effective oxygen concentration with respect to the soaking days is shown in Table 8 below.

Further, Table 9 shows the consumption of hypochlorous acid per 1 kg of seed paddy calculated from the amount of decrease in the effective chlorine concentration.

From the above table, comparing samples 3-2, 3-4, 3-5 to see the effect of attaching a lid to the immersion tank to make it a closed system, the effective chlorine concentration after 70 hours (3 days) was without a lid. With a lid, it was 25,34 mg / kg for 5 mg / kg, and in terms of hypochlorite consumption, it was 275 (mg / kg of seed rice) without a lid, and 130,175 (mg / kg of seed rice) with a lid. Despite the low consumption, the infection rate after soaking is lower with the lid than without the lid, indicating that the infection prevention effect is better.

It is thought that this is because the lid prevents the release of hypochlorous acid to the atmosphere, which effectively acts on the sterilization of seed paddy and the bacteria dissolved in the hypochlorous acid water.

Therefore, it can be seen that it is effective to set the consumption of hypochlorous acid to 130 (mg / kg of seed paddy) in order to prevent secondary infection in a closed system with a lid on the immersion tank.

On the other hand, without the lid, 270 (mg / kg of paddy) hypochlorous acid, which is a guideline for infection prevention, was consumed 70 hours later (3 days later), but the infection rate exceeded 5%. It is presumed that this is because the effective chlorine concentration after 70 hours (3 days) is 5 mg / kg, and the target value of 7 mg / kg or more cannot be maintained.

Next, comparing samples 3-4 and 3-5 to see the effect of water exchange before sprouting, the infection rate after sprouting was 50.0% without exchange and 2.0% with exchange. It can be seen that there is a great improvement effect. Furthermore, looking at the incidence rate in raising seedlings, there is a large difference in the effect as with the infection rate, with 24.5% without replacement and 0% with replacement. It can be seen that it is important to start sprouting in a high concentration state and keep the effective chlorine concentration at 7 mg / kg or more until the end of sprouting to prevent infection.

Example 4
For soaked seeds with a bath ratio of 5, verification is performed assuming actual use in which contaminated paddy is also sterilized with hot water.

In Examples 1 to 3, the contaminated paddy was not sterilized with hot water in order to clarify the effect of preventing secondary infection. In Example 4, the contaminated paddy was also sterilized with hot water according to practical use, and the immersion tank was verified with a closed system with a lid.

The same hot water sterilization as in Example 1 was carried out separately for healthy paddy and contaminated paddy. Then, hypochlorite water having an effective chlorine concentration of 60 mg / kg (pH 6.0) at a bath ratio of 5 (volume ratio (volume ratio)) was applied, and seeding was carried out at 12 ° C. for 7 days. Here, the hypochlorite water was replaced on the third day. The effective oxygen concentration on the 3rd and 7th days was measured. The measurement on the third day was performed before replacing the hypochlorite water.

The sprouting step was carried out after soaking, and the seeding solution was used as it was (Sample 4-2), and the hypochlorite water was completely replaced before sprouting (Sample 4-3). In addition, tap water with a bath ratio of 5 was prepared as the target area (Sample 4-1). The exchange of tap water was carried out at the same time as the exchange of hypochlorite water at the time of soaking and before germination.

The infection rate of the seeds after soaking and sprouting was measured in the same manner as in Example 1. Further, in the same manner as in Example 2, the seedlings were raised with seedlings after germination, and the incidence rate of the seedlings was measured. The obtained results are shown in Table 10 below.

The effective oxygen concentration with respect to the soaking days is shown in Table 11 below.

Further, the consumption of hypochlorous acid per 1 kg of seed paddy calculated from the effective chlorine concentration is shown in Table 12 below.

It can be seen that the combination of hot water sterilization and hypochlorite water, which is supposed to be used in actual use, has a high infection control effect. In particular, when the hypochlorite water was exchanged during soaking and before sprouting to maintain a high effective chlorine concentration (Sample 4-3), the infection rate to healthy paddy was 0% both after soaking and after sprouting. No illness was observed in the subsequent raising of seedlings, which is a good result.

Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (9)

After sterilizing the seeds with warm water or low pesticides with no residual effect, the seeds are sterilized by using hypochlorite water as the soaking solution in the soaking or germination process to prevent the seeds from being infected through the soaking solution. -Infection control method. According to claim 1, the dipping solution has a bath ratio of the hypochlorite water to the seed paddy of 2 to 10 by volume and an effective chlorine concentration of the hypochlorite water of 10 to 60 mg / kg. The method described. Claim 1 or 2 that the dipping solution maintains an effective chlorine concentration of 7 mg / kg or more from the start of immersion to 70 hours in the soaking step, and maintains an effective chlorine concentration of 7 mg / kg or more until the end in the germination step. The method described in. The method according to claim 1 or 2, wherein the soaking solution consumes 130 mg or more of hypochlorous acid per 1 kg of paddy in the soaking step from the start of soaking to 70 hours. The method according to claim 3 or 4, wherein the immersion liquid is replaced with the hypochlorite water at least once. The method according to claim 3 or 4, wherein the immersion liquid is regenerated by adding or recovering the hypochlorite water, or regenerating the immersion liquid. The method according to any one of claims 1 to 6, wherein the soaking and sprouting steps are closed by covering the inundation tank with low consumption of hypochlorous acid. The fourth aspect of claim 4, wherein the replacement of the hypochlorite water includes recovering the effective chlorine concentration by supplying a new hypochlorite water after discharging most of the hypochlorite water. Method. In the exchange of the hypochlorite water, a part of the hypochlorite water is exchanged with a hypochlorite water having an effective chlorine concentration higher than the effective chlorine concentration of the hypochlorite water to obtain effective chlorine. The method of claim 4, comprising restoring the concentration.

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