JP2005168315A - Sterilized seed and seedling article and method for sterilizing seed and seedling article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a method for iodine gas sterilization by which sufficient sterilization can be carried out without deteriorating the growth of a seed and seedling article. <P>SOLUTION: The seed and seedling article is sterilized with the iodine gas. The growth rate after the sterilization with the iodine gas is ≥0.8 based on the growth rate before the sterilization with the iodine gas. Furthermore, the seed and seedling article is any of the following. The pathogenic concentration of the seed and seedling article after the sterilization with the iodine gas is ≤1.0 the critical concentration of the pathogens required for the onset of the seed and seedling article; the sterilization rate is ≥60% or the bacteria carrying rate is ≤80%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a seedling article sterilized with iodine gas and a sterilization method.

  Seed and seedling products such as seeds are sterilized by dressing treatment with agrochemicals (disinfectant), heat treatment, chemical immersion treatment, etc. The sterilization treatment by this method has been studied. For example, as described in Non-Patent Documents 1 and 2, heat treatment is generally performed, but depending on the treatment conditions, germination may be adversely affected, and seed storage may be reduced. is there. Further, in the chemical immersion treatment, there is no problem when seeding immediately after the treatment, but when stored after the treatment, germination may be lowered. Furthermore, it is not suitable for crops where seed coats are easily removed by immersion.

On the other hand, iodine has a bactericidal effect, and usually a liquid bactericidal agent in which iodine is dissolved is used and is subjected to a bactericidal treatment by a method such as dipping or coating. Although iodine has sublimation properties, gaseous iodine also has a bactericidal effect, for example, as described in Non-Patent Document 3, but there is no report of a technology that can be put to practical use.
Keiko Higashi, “Kaiare Daikon Seed Dry Heat Disinfection Method”, [online], Ministry of Agriculture, Forestry and Fisheries Vegetable and Tea Experiment Station, [Search July 18, 2002], Internet <URL: http: // www. afftis. or. jp / shinji / 01. htm> Hiroshi Nakamura, “Dry-heat disinfection technology for vegetable seeds”, [online], Ministry of Agriculture, Forestry and Fisheries Vegetable and Tea Experiment Station, [searched July 18, 2002], Internet <URL: http: // www. afftis. or. jp / shinji / 01. htm> Isao Shibazaki, “Recent Topics on Iodine Environmental Disinfectants”, Food Industry, Vol. 29, No. 2, pages 60-71, especially page 68 (1986)

  In view of the situation as described above, an object of the present invention is to realize an iodine gas sterilization method capable of performing sufficient sterilization without impairing the growth rate of seedling articles.

  According to the present invention for achieving the above object, a seedling article sterilized with iodine gas is provided.

  Moreover, according to this invention, the sterilization method of the seedling articles by iodine gas is provided.

  According to the iodine gas sterilization method of the present invention, sufficient sterilization can be realized without impairing the growth rate of the seedling product.

  The present invention is described in detail below.

(Seedling products)
Seed and seedling articles are seeds, roots, leaves, stems, flowers, seeds and seedlings of various plants; plants obtained by growing these seeds, roots, leaves, stems, flowers, seeds and seedlings; these seeds, roots , Cultivation supplies used to grow leaves, stems, flowers, seeds and seedlings, etc. These seedling articles can be sterilized well with iodine gas.

  Specifically, cabbage, Chinese cabbage, komatsuna, broccoli, cauliflower, spinach, lettuce, celery, leek, onion, leek, garlic, ginger, ginger, ginger, horseradish, ginger rhinoceros, Kyoto mizuna, parsley, etc. Roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies; root vegetables seeds such as radish, turnip, carrot, burdock, beet, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies; Tomato (including rootstock), mini tomato, eggplant (including rootstock), pepper, paprika, cucumber, watermelon, melon (including rootstock), pumpkin (including rootstock), zucchini, okra, sweet corn, etc. Fruit and vegetable seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies; green beans, green beans, taiz, azuki beans, black beans, peas, broad beans, la Seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies such as caustic; potato seeds, roots, leaves, stems, seedlings , Plants, flowers, berries and cultivation supplies; seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies such as silkworms, bean sprouts, green onions, bees, perilla; Dahlia, daffodil, leaf peony, morning glory, yugao, eustoma, limonium, delphinium, canna, cyclamen, stock, coconut, nylenbergia, pansy, viola, sunflower, petunia, melanpodium, linaria, rudbeckia, osteospermum, goldfish, lobelia, roberia , Flower bulbs, seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies; Plum, cherry, cedar, camellia, spider, chestnut, tea, coffee, ginkgo, and other tree seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies; Dent corn sorgo, rye, Italian, En Forage crops such as wheat, legumes, and turf seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies; bananas, pineapples, kiwis, apples, peaches, grapes, pears, oysters, akebi, Seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies of figs, loquats, strawberries, mandarin oranges, kumquats, decapons, lemons, olives, cherries, etc .; rice, wheat, sesame, buckwheat, millet Seeds, roots, leaves, stems, seedlings, plants, flowers, berries and cultivation supplies such as millet, maize, etc .; seeds, roots, leaves, ornamental plants such as kapok, pacula, croton, rubber, cactus, etc. Stem, seedling, plant, Flowers, fruits and cultivated goods can be sterilized with iodine gas.

  The cultivation supplies indicate cultivation materials and facilities, and examples of the cultivation materials include culture media, support materials, coating materials, containers (pots, trays, containers, etc.) and the like. In addition, the culture medium includes culture soil, straw, wood, rock wool, sand, gravel, pumice sand, perlite, ceramic, charcoal, resin-based medium, peat moss, coconut fiber, bark medium, rice husk, neat, and sotan. Examples of the culture medium include solid, clay, paste, gel, sol, and liquid.

  Among the seed and seedling articles as described above, those that can take full advantage of the iodine gas sterilization method are articles in which the growth rate is not desirably lowered by sterilization. Examples of such articles include seeds.

  In addition, even if the seed and seedling articles as described above are sterilized with iodine gas, the growth rate of the seed and seedling articles may not be lowered or improved. For example, in the case of seeds, germination rate and germination rate may not be reduced or improved by iodine gas sterilization. In addition, since the attached and mixed bacteria are sterilized in the cultivation supplies, the growth rate is improved by reducing the occurrence of diseases.

  The growth rate used here is an index indicating the degree of growth when each living body is grown in a constant growth environment, and is a seed, root, leaf, stem, flower, fruit and seedling; Plants obtained by growing seeds, roots, leaves, stems, flowers, seeds and seedlings have different indices for each living body, for example, germination rate in the case of seeds, and roots in the case of roots. In the case of root amount, rooting, and leaf, the leaf length and leaf width, and in the case of seedlings, the plant height and the weight of the plant are the growth rate. In the case of cultivation supplies, seeds, roots, leaves, stems, flowers, seeds and seedlings using these supplies; plants obtained by growing these seeds, roots, leaves, stems, flowers, seeds and seedlings It is an index indicating the degree of growth and conforms to the growth rate index standard for each living body.

  Specifically, in the case of seeds, the germination rate refers to the proportion of seeds that have produced normal sprouting among the seeds that have been sown. For example, germination rate (%) = (after seeding, the number of days necessary for the seeds to germinate Further, the number of normal germination / the number of sowing after a sufficient number of days is calculated by 100, and is a value for evaluating the final germination property. The higher this value, the better. Since the germination rate of the seed after iodine gas sterilization is high, it is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. Further, since the germination rate of seeds is not lowered or improved by iodine gas sterilization, the germination rate after iodine gas sterilization is higher than the germination rate before iodine gas sterilization, preferably 0.8 times or more, more preferably 0.9. Double or more, more preferably 1.0 or more, and most preferably 1.1 or more can be realized.

  In addition to the germination rate described above, germination vigor is also important. Germination vigor refers to the ratio of the number of germinations until a certain time before the germination cut-off date. For example, germination vigor (%) = (when the seeds have passed the number of days necessary for germination after sowing. (Number of germination / number of seeding) × 100, which is a value for evaluating the uniformity of germination. The higher this value, the better. Since the seed germination rate after iodine gas sterilization is high, it is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. In addition, since germination of seeds is not reduced or improved by iodine gas sterilization, germination after iodine gas sterilization is higher than germination before iodine gas sterilization, preferably 0.8 times or more, more preferably 0.9 times. Double or more, more preferably 1.0 or more, and most preferably 1.1 or more can be realized.

  In addition, like the relationship between the germination rate and the growth rate, the growth rate can be defined according to the definition of the germination rate. In other words, the growth rate is an index indicating the alignment of growth when each living body is grown for a certain period in a certain growth environment. Seeds, roots, leaves, stems, flowers, fruits These seeds, roots, leaves, stems, flowers, fruits, and plants obtained by growing seedlings have different indices for each living body. For example, in the case of seeds, germination vigor, roots The growth rate is evaluated based on the amount of roots and the length of the roots, in the case of leaves, the leaf length and width, and in the case of seedlings, the plant height and the weight of the plant. In the case of cultivation supplies, seeds, roots, leaves, stems, flowers, seeds and seedlings using these supplies; plants obtained by growing these seeds, roots, leaves, stems, flowers, seeds and seedlings It is an index indicating the growth uniformity and conforms to the growth trend index standard for each living body.

  In addition, like the germination rate, the growth rate is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. The growth rate after iodine gas sterilization is higher than that before iodine gas sterilization, preferably 0.8 times or more, more preferably 0.9 times or more, still more preferably 1.0 times or more, and most preferably 1. More than 1 time can be realized.

  Further, like the germination, the growth rate is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. Further, the growth rate after iodine gas sterilization is higher than the growth rate before iodine gas sterilization, preferably 0.8 times or more, more preferably 0.9 times or more, still more preferably 1.0 times or more, most preferably 1. More than 1 time can be realized.

  In the iodine gas sterilization method, the pathogen tissue is fatally damaged by chemical action such as oxidation by iodine, so the spectrum of pathogens that can be sterilized by iodine gas is wider than other sterilization methods. Specifically, pathogenic animals such as bacteria, molds, fungi, viruses, nematodes and eggs thereof can be sterilized with iodine gas. After sterilizing these pathogens with iodine gas, the concentration of the pathogens present in the seedling articles is below the critical concentration necessary for pathogenesis.

  As a method for quantifying the concentration of pathogens, for example, (a) the number of pathogens existing per unit mass (eg, 1 g) of seedling articles (eg, 1 g), and (b) possessing pathogens in all seedling articles Adopt the ratio (%) of the seed and seedlings used. The number of pathogens is measured by (a) extracting the pathogens held by the seedling article, growing it on a plate, etc., and measuring the number of colonies, plaques, etc. (C) Pathogenic animals and pathogens that can be observed with an optical microscope and an electron microscope, such as eggs, can be directly detected using an optical microscope and an electron microscope. Use a method such as measuring.

  Since the iodine gas sterilization method has high sterilization efficiency, the pathogen concentration of the seedling article after iodine gas sterilization is preferably 1.0 times or less, more preferably 0.9 times or less of the critical concentration of the pathogen necessary for the pathogenesis of the seedling article. More preferably, 0.8 times or less can be realized.

  In addition, since the iodine gas sterilization method has high sterilization efficiency, the ratio (sterilization rate,%) killed by sterilization of the pathogen present per unit mass (for example, 1 g) of the seedling product is high, preferably 60% or more, More preferably 80% or more, still more preferably 90% or more, and in some cases 98% or more can be realized.

  Furthermore, since the iodine gas sterilization method has a high sterilization efficiency, the proportion of seedling articles that possess pathogens in all the seedling articles after sterilization (bacterial retention rate,%) is low, preferably 80% or less, more preferably 70%. Hereinafter, more preferably 60% or less can be realized.

(Iodine gas sterilization method)
As a specific form of the sterilization method using iodine gas, (a) as a first form, iodine is generated by sublimating solid iodine in a gaseous medium, and this iodine gas is mixed with the gaseous medium. (A) As a second form, a liquid containing iodine is sprayed on the seedling article, and iodine is distributed from the liquid to the gas phase part to generate iodine gas. (C) As a third form, solid iodine is mixed with a seedling article, the solid iodine is sublimated, iodine gas is generated, and the seedling article is brought into contact. Hereinafter, each form is demonstrated.

(A) 1st form In FIG. 1, as an example of an apparatus for the 1st form, iodine gas generation part 110, iodine gas generated in iodine gas generation part, and seedling articles are made to sterilize seedling articles. The sterilization apparatus provided with the seedling article sterilization part 111 was shown. The entire apparatus is sucked by the pump 116, and the gas medium 113 is introduced into the iodine gas generation unit. The flow rate of the gaseous medium is controlled by the valve 114 and measured by the flow meter 115. The iodine gas generation unit is filled with solid iodine, and the solid iodine is sublimated to generate iodine gas, and the iodine gas is transported to the seedling article sterilization unit 111 by a gas medium airflow. The seed and article sterilization section is filled with the seed and seed article, and the seed and seed article is sterilized when iodine gas contacts the seed and seed article.

  In addition, as a gaseous medium, air, humidified air, dry air, nitrogen, helium, argon, carbon dioxide, C1-C5 unsaturated and saturated hydrocarbon, etc. are used, and these are used together as needed. You can also.

  As solid iodine, flake products (flaky products), prill products (spherical products), granule products (square granular products), etc. are used. A prill product is preferable because of the occurrence of the above.

  Furthermore, the iodine gas generating part is preferably a replaceable cassette filled with solid iodine. This is because new solid iodine can be safely and easily installed after all solid iodine is used.

  As the container into which the seedling article of the seedling article sterilization section is charged, it is desirable that the iodine gas transported and introduced by the gas medium air flow in the seedling article sterilization section uniformly contacts the seedling article while the seedling article is being stirred. A structure that is sterilized by contact with iodine gas is preferred. In this case, since the seedling product is agitated during sterilization, sterilization proceeds efficiently and uniformly. In addition, when introducing a gas containing iodine gas, if the sterilization treatment is performed under the condition that the flow rate is increased and the seedlings are stirred by an air flow, no further stirring means is required, so that the sterilization apparatus is not complicated. .

  Further, in order to suppress solid iodine from solidifying and crystallizing on the seed and seedling article in the seed and seed article sterilizing section, it is preferable to control the temperature of the seed and seed article article sterilizing section to be equal to or higher than the temperature of the iodine gas generating section. In the case of the sterilization apparatus of FIG. 1, the temperature of the iodine gas generation unit is controlled by the temperature controller 117, and the temperature of the seedling article sterilization unit is controlled by the temperature controller 118.

  If necessary, a means 112 for removing iodine in the discarded gas is provided. As the iodine gas removing means, for example, an alkali absorption method such as a 1% by mass sodium hydroxide aqueous solution, a reducing agent absorption method such as a sodium thiosulfate aqueous solution, an adsorption method using an adsorbent such as activated carbon, or the like is used.

  In addition, if at least one of the iodine gas generation unit and the seedling product sterilization unit includes a means for diluting iodine gas, a wider range of iodine gas concentration can be realized, and in particular, treatment with low concentration iodine gas is performed. The case is suitable, and the operability of adjusting the iodine gas concentration is improved. For example, as shown in FIG. 1, the second gaseous medium 122 is introduced and mixed through a three-way cock 119 to dilute iodine gas. The flow rate of the second gas medium is controlled by the valve 121 and measured by the flow meter 120.

  Furthermore, by adopting such a structure, by operating the three-way cock after sterilization, a gas that does not contain iodine gas such as the second gas medium can be introduced into the seedling article sterilization unit. As a result, the solid iodine remaining in the seedling article can be sublimated and removed.

  In addition, it is preferable that the site | part which contacts iodine gas is comprised by at least any one of glass and non-corrosive resin, in order to suppress the corrosion by iodine gas. As the non-corrosive resin, vinyl chloride resin, fluorine resin, or the like is used.

  In the case of the sterilization apparatus shown in FIG. 1 as described above, iodine gas generated from the iodine gas generation unit passes through the seedling article sterilization unit, and then iodine is removed and discarded by the iodine gas removal unit. is there. For this reason, there exists a possibility that the use efficiency of iodine gas may become inadequate. On the other hand, after the iodine gas in the apparatus reaches a predetermined concentration, the gaseous medium containing iodine gas is circulated through a path passing through the seedling article sterilization unit, and in some cases, iodine lost due to adsorption to the seed or the like during the treatment is removed. In order to replenish, if the so-called circulation system is adopted, the use efficiency of iodine gas can be improved.

  FIG. 2 shows an example of a circulation type sterilizer. The iodine gas generation unit 210, the seedling article sterilization unit 211, and the iodine gas removal unit 212 are the same as those in FIG. In the case of the sterilizer of FIG. 2, first, the corrosion-resistant pump 221 is operated, the three-way cock 213 is operated, and the gaseous medium 216 is introduced into the sterilizer. At this time, the three-way cock 218 is operated to introduce the gas medium into the iodine gas generation unit, the three-way cock 219 is operated to be introduced into the seedling article sterilization unit, and the three-way cock 220 is operated to remove the gas medium from the corrosion-resistant pump side. To transport. Thereafter, the three-way cock 213 is operated to stop the introduction of the gas medium 216, and the gas medium is circulated in a sealed path passing through the iodine gas generation unit and the seedling article sterilization unit. The flow rate of the gaseous medium is controlled by flow meters 214 and 217.

  When the circulation of the gaseous medium is continued, the concentration of iodine gas increases while sterilization proceeds. When the iodine gas concentration reaches a predetermined value, the three-way cock 218 is operated so that the gaseous medium does not pass through the iodine gas generating part, and in the sealed path passing through the seedling article sterilizing part without passing through the iodine gas generating part. Circulate the gaseous medium further and continue sterilization. In the case of loss due to adsorption to seeds during the treatment, iodine is supplied into the switching gas medium so that the circulation path of the gas medium is introduced into the iodine gas sterilization unit. Thus, if it processes by an airflow circulation type, since the iodine of an iodine gas generation part is not sublimated wastefully, the consumption of iodine can be reduced.

  A gas medium containing a predetermined concentration of iodine gas is circulated for a predetermined time, and sterilization is terminated. Thereafter, the three-way cock 213 is operated to introduce the gaseous medium 216 again into the sterilizer. At this time, the three-way cock 218 is operated so that the gaseous medium is not introduced into the iodine gas generating unit, the gaseous medium not containing iodine gas is introduced into the seedling article sterilizing unit, and the three-way cock 220 is operated to remove the gaseous medium. Introduce into iodine gas removal means. By introducing a gaseous medium not containing iodine gas into the seedling article sterilization unit, iodine remaining on the seedling article by adsorption or the like is sublimated and removed.

  Also in the case of the sterilizer of FIG. 2, the temperature of the iodine gas generating unit is controlled by the temperature controller 222, the temperature of the seed material sterilizing unit is controlled by the temperature controller 223, and the temperature of the seed material sterilizing unit is generated by iodine gas. The temperature is set to be equal to or higher than the temperature of the part, and iodine is condensed and solidified in the seedling article sterilization part to suppress crystallization on the seedling article.

  Moreover, it is preferable that the site | part which contacts iodine gas is comprised with at least any one of glass and non-corrosive resin, in order to suppress the corrosion by iodine gas. As the non-corrosive resin, vinyl chloride resin, fluorine resin, or the like is used.

(B) Second form As an example of the apparatus for the second form, seed material that has been sprayed with an iodine-containing liquid is put into a container, and iodine gas is distributed to the gas phase in the container to sterilize the seed material. There is a device to do. Such an apparatus is considered suitable for a batch type.

  The iodine-containing liquid is preferably a liquid that has high volatility such as water and alcohols and does not decrease the growth rate of the seedling product.

  Moreover, it is preferable to temperature-control the site | part which sterilizes a seedling article with iodine gas from a viewpoint of suppressing that an iodine condenses on the site | part which sterilizes a seedling article.

  Furthermore, it is preferable that the part which contacts iodine gas is comprised with at least any one of glass and non-corrosive resin, in order to suppress the corrosion by iodine gas. As the non-corrosive resin, vinyl chloride resin, fluorine resin, or the like is used.

(C) Third embodiment As an example of the device for the third embodiment, solid iodine and seedling articles are mixed in a container, and iodine gas is distributed to the gas phase portion in the container to sterilize the seedling articles. There is. Such an apparatus is considered suitable for a batch type.

  In the case of the third embodiment, as in the case of the second embodiment, the temperature of the site for sterilizing the seedling product with iodine gas is controlled from the viewpoint of suppressing iodine from condensing on the site for sterilizing the seedling product. Is preferred.

  Further, as in the case of the second embodiment, the portion in contact with iodine gas is preferably composed of at least one of glass and non-corrosive resin in order to suppress corrosion by iodine gas. As the non-corrosive resin, vinyl chloride resin, fluorine resin, or the like is used.

(Disinfection conditions for iodine gas sterilization)
Sterilization conditions such as iodine gas concentration, sterilization temperature, sterilization time, and agitation conditions are carefully optimized to achieve sufficient sterilization without compromising the growth of the seedling article. Among these sterilization conditions, optimization of iodine gas concentration, sterilization temperature, and sterilization time is important.

  The concentration of iodine gas is preferably 10 ppm by volume or more, more preferably 100 ppm by volume or more, from the viewpoint of realizing a sufficient sterilizing effect. On the other hand, from the viewpoint of suppressing a large amount of iodine from remaining on the surface of the seedling article and ensuring safety even in the event of an iodine gas leak, it is preferably 10,000 ppm by volume or less, and 5,000 ppm by volume. The following is more preferable, and 2,000 ppm by volume or less is still more preferable.

  Depending on the type of seedling article, a sufficient sterilizing effect can be realized with a low concentration of iodine gas, or iodine may easily remain on the surface. In the case of such seed and seedling articles, the concentration of iodine gas is lowered, and the lower limit thereof is preferably 0.1 ppm by volume or more, more preferably 1 ppm by volume or more, and still more preferably 10 ppm by volume or more.

  Although it depends on the concentration of iodine gas, the sterilization time is preferably 10 minutes or more, more preferably 60 minutes or more, and still more preferably 120 minutes or more from the viewpoint of realizing a sufficient sterilization effect. On the other hand, from the viewpoint of suppressing a large amount of iodine from remaining on the surface of the seedling article and improving work efficiency, it is preferably 24 hours or shorter, more preferably 12 hours or shorter, and even more preferably 6 hours or shorter.

  In addition, depending on the kind of seedling articles, a sufficient sterilizing effect can be realized by a short time treatment, or iodine may easily remain on the surface. In the case of such seed and seedling articles, the sterilization time is shortened, and the lower limit thereof is preferably 1 second or longer, more preferably 10 seconds or longer, and even more preferably 1 minute or longer.

  On the other hand, depending on the type of seedling article, a long time treatment may be required for a sufficient sterilizing effect, or iodine may be difficult to remain on the surface. In the case of such seed and seedling articles, the sterilization time is lengthened, and the upper limit thereof is preferably 1 month or less, more preferably 7 days or less, and further preferably 3 days or less.

  The sterilization temperature is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, from the viewpoint of realizing a sufficient sterilizing effect. On the other hand, from the viewpoint of suppressing a decrease in the growth rate of the seedling product, 80 ° C. or lower is preferable, 60 ° C. or lower is more preferable, and 40 ° C. or lower is still more preferable.

  Further, as an indicator of sterilization conditions, the product of iodine gas concentration and sterilization time is preferably 100 ppm by volume or more from the viewpoint of realizing a sufficient sterilization effect, while a large amount of iodine is present on the surface of the seedling article. From the viewpoint of suppressing remaining and improving work efficiency, 50,000 ppm by volume or less is preferable.

  In addition, the sterilization method is roughly divided into a method of sterilizing for a long time with a low concentration of iodine gas and a method of sterilizing for a short time with a high concentration of iodine gas. Depending on the ease of handling, there are cases where a high concentration short time is appropriate and a low concentration long time is appropriate. If the article to be sterilized is a seed, the adsorptivity of iodine varies considerably depending on the surface properties and constituents of the seed coat, and high-concentration, short-term treatment tends to be good for seeds that are difficult to adsorb iodine. For seeds that are easy to do, iodine may be adsorbed to the seed at a high concentration in a short time at a high concentration, and the germination rate of the seed may be reduced. In such a case, it is considered that it is better to process at a low concentration for a long time.

(Characteristics of iodine gas sterilization method)
The iodine gas sterilization method has the following advantages as compared with the existing sterilization methods, in addition to sufficient sterilization without impairing the growth of the seedling product.

  (A) Compared with chemical immersion, cleaning and drying after sterilization and disposal of chemicals are not necessary.

  (I) It is suitable for seeds whose seed coats are easy to fall off when dipped like Brassicaceae or Legumes.

  (C) Compared with dry heating, the germination rate is less decreased and seedling articles can be sterilized efficiently.

  (D) Compared with the low temperature plasma sterilization method, an expensive apparatus is not required.

  (E) Compared with pesticide dressing, it can also be applied to seedlings and articles that are prohibited to use pesticides such as pesticide-free cultivation.

  (F) Compared with fumigation treatment, gas treatment after treatment is easy, no harmful substances are generated, and safety is high.

  Furthermore, the iodine gas sterilization method has the following advantages.

  (G) It is thought that a small amount of iodine is adsorbed to the seedling article after sterilization, but the sterilization effect is retained by the adsorbed iodine.

  (Iii) Since the residual iodine adsorbed on the seedling product volatilizes little by little to the extent that it is not irritating or corrosive, it is safe.

  (G) Although it reacts with the organic components of the seedling product, the deterioration of the seedling product is small.

  (I) Iodine used for sterilization is an element, and since it is an essential element for humans, it is less harmful to the human body.

  (Sa) Since the spectrum of pathogenic bacteria that can be sterilized by iodine gas is wide, molds, bacteria, viruses, nematodes and the like can be sterilized by a single treatment.

  Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, commercially available high-purity products were used as reagents.

(Examples 1-19) Sterilized seeds 1-19
Black rot naturally contaminated cabbage seeds and black soot disease naturally contaminated cabbage seeds were sterilized with iodine gas. The pathogen of black rot is Xanthomonas campestris (bacteria), and the pathogen of black soot is Alternaria brassicicola (mold).

  A glass column is filled with 20 g of solid iodine (prill), another glass column is filled with 10 g of microorganism-contaminated seeds, both columns are connected with glass tubes, and a flow control valve is provided at the air inlet of the iodine-filled column. In addition, the air outlet of the seed packed column is connected to a gas absorption bottle containing 1% NaOH aqueous solution with a glass tube, and the outlet of the gas absorption bottle is connected to an air pump to suck air. The sterilization treatment was performed by the one-way method. The downstream side of the absorption bottle was installed in a thermostatic chamber, and iodine gas sterilization was performed under the conditions shown in Tables 1 and 2. The aeration gas flow rate was adjusted to 0.5 L / min with a flow rate adjusting valve at the end. After passing the time shown in Table 1 and Table 2, air containing no iodine gas was introduced into the seedling article sterilization section. The concentration of iodine gas was calculated by measuring the iodine concentration in the absorbing solution and the gas flow rate.

  The sterilized state of the sterilized seeds obtained as described above was examined. The cabbage black rot fungus (Xanthomonas campestris) soaked the seed with 2.5 times the amount of sterile physiological saline per weight at a speed of 150 rpm for 2.5 hours. Dilute the suspension after immersion to 1/10, 1/100, 1/1000, or 1/10000 (volume) with sterile physiological saline, and apply each diluted solution to the selective medium of black rot fungus. did. Thereafter, the cells were cultured for 3 to 5 days, and the colonies of black rot fungi formed on the medium were measured for the culture sample having a measurable dilution ratio, and converted to the number of pathogenic bacteria per 1 g of seed (cfu / g).

  In addition, detection of black smut fungus (Alternaria brassicicola) was performed by the following method. Two filter papers moistened with sterilized water were spread on a petri dish, and seeds were placed on the filter paper. The petri dish was allowed to stand at 20 ° C. for 1 day, at −20 ° C. for 1 day, and at 20 ° C. under BLB (12 hours) for 6 days. Thereafter, the seed surface was observed with a stereomicroscope to test for the presence or absence of growth of black soot pathogen, and the ratio of seeds on which the pathogenic fungus grew was evaluated as the retention rate (%).

Furthermore, as a germination evaluation, a germination test was conducted by the following method. Two pieces of filter paper were spread on the petri dish, 4 ml of distilled water was added, and then 50 seeds were placed thereon. The seeding number was 100 to 200 grains in each section. Germination vigor was calculated from the number of germinations on the 4th day. Moreover, the germination rate was calculated from the number of germinations on the 7th day;
Germination vigor (%) = (number of germination on day 4/100 grains) × 100,
Germination rate (%) = (number of germination on day 7/100 grains) × 100.

  The obtained results are shown in Tables 1 and 2.

The sterilizing effect was increased by increasing iodine gas concentration and sterilization time for black rot fungus-contaminated seeds. In this example, the initial number of bacteria was sterilized using 2.0 × 10 ⁵ seeds / g seed, but 95% or more at which seeds were sterilized by sterilization with iodine gas concentrations of 100 ppm · 24 hours and 1000 ppm · 12 hours. Was able to sterilize. Furthermore, the sterilization treatment of 1000 ppm · 24 hours was able to sterilize 100%. In addition, there was no significant effect on germination, and germination improved when iodine gas concentration was relatively low. In addition, when the initial number of seeds to be retained is smaller than that of the test seeds of this time, the same effect can be obtained even with a shorter concentration of iodine gas.

  For seeds contaminated with black soot disease, treatment with iodine gas concentrations of 100 ppm for 24 hours, 1000 ppm for 24 hours, 2000 ppm for 6 hours should reduce the initial bacterial retention rate to 9% or less to 7% or less. I was able to. As for germination, germination tends to be improved with an increase in the bactericidal rate, and at 2000 ppm · 6 hours, the germination rate before treatment was improved to 91% with respect to 71%. In addition, the seeds treated under these sufficiently bactericidal effects not only improved the germination rate but also reduced the abnormal germination rate. This is thought to be due to the disappearance of germs on the seeds and the contamination of living tissues during germination.

(Example 20) Sterilized seed 20
In the same manner as in Examples 1-19, seeds of black spot fungus (Alternaria radicina) and black leaf blight fungus (Alternaria dauci) were naturally sterilized under conditions shown in Table 3.
Detection of black spot fungus (Alternaria radicina) and black leaf blight fungus (Alternaria dauci) possessed by the carrot seeds subjected to sterilization treatment was carried out by the following method. Three filter papers moistened with sterilized water were laid on a petri dish, and seeds were placed thereon. The petri dish was allowed to stand for 3 days in the dark at 20 ° C., for 1 day at −20 ° C., and for 6 days under BLB at 20 ° C. (12 hours). Thereafter, the seed surface was observed with a stereomicroscope to test the presence or absence of growth of black spot fungus and black leaf blight fungus, and the ratio of seeds on which the disease fungus was growing was evaluated as the retention rate (%).

  Furthermore, as a germination evaluation, a germination test was conducted by the following method. A 200-hole cell tray was filled with seedling culture soil, and 200 seeds per seed were seeded. The soil temperature was controlled at about 25 ° C., and the germination rate was examined on the 7th day and the germination rate was examined on the 14th day.

  The obtained results are shown in Table 3.

(Examples 21 to 23) Sterilized seeds 21 to 23
In the same manner as in Examples 1 to 19, the scab artificially contaminated tomato seeds were sterilized with iodine gas under the conditions shown in Table 4.

  The detection of the causal fungus was carried out by the following method. Seeds were placed in a phosphate buffer solution (added with 0.02% tween 20) in an amount of 4 times the weight, and allowed to stand for 16 hours to extract scab. This extract was diluted to 1/10, 1/100, 1/1000, and 1/10000 (volume) with sterile physiological saline as a stock solution, and each diluted solution was applied to two types of selective cultures for causal fungus. Thereafter, the cells were cultured for 5 to 10 days, and colonies of scabs produced on the culture medium were measured on the culture samples having a measurable dilution ratio, and converted to the number of pathogenic bacteria per 1 g of seed (cfu / g).

  Further, germination was evaluated in the same manner as in Example 19, and the germination rate was examined on the 6th day and the germination rate was examined on the 14th day.

  Table 4 shows the obtained results.

(Example 24) Sterilized seed 24
A liquid containing iodine is sprayed on the cabbage seeds, and iodine is distributed from the liquid to the gas phase part to generate iodine gas, which is brought into contact with the cabbage seeds and sterilized.

(Example 25) Sterilized seed 25
Solid iodine is mixed with cabbage seeds, and the solid iodine is sublimated to produce iodine gas, which is brought into contact with cabbage seeds and sterilized.

(Example 26) Sterilization tuber 1
Sterilize potatoes.

(Example 27) Sterilized seedling 1
Sterilize sweet potato seedlings.

(Example 28) Sterilized cultivation article 1
Sterilize the seedling cell tray and the seedling box.

(Example 29) Sterilized cultivation article 2
Sterilize the supporting column.

(Example 30) Sterilized cultivation article 3
Sterilize the house.

  By using iodine gas sterilization method, seeds can be sterilized at a very high sterilization rate without impairing seed germination, especially seed germination and germination rate, and without adversely affecting seeding and seedling stages. Can contribute to high quality and stable agricultural production.

It is a typical sectional view for explaining an iodine gas sterilizer. It is a typical sectional view for explaining an iodine gas sterilizer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 Iodine gas generating part 111 Seedling article sterilization part 112 Iodine gas removal means 113 Gas medium 114 Valve 115 Flow meter 116 Pump 117 Temperature controller 118 Temperature controller 119 Three-way cock 120 Flow meter 121 Valve 122 Second gas medium 210 Iodine gas generation Part 211 Seedling article sterilization part 212 Iodine gas removing means 213 Three-way cock 214 Flow meter 215 Valve 216 Gas medium 217 Flow meter 218 Three-way cock 219 Three-way cock 220 Three-way cock 221 Pump 222 Temperature controller 223 Temperature controller

Claims (10)

  Seedlings sterilized with iodine gas. The growth rate after the iodine gas sterilization with respect to the growth rate before the iodine gas sterilization is 0.8 or more;
The pathogen concentration of the seedling article after iodine gas sterilization is 1.0 times or less the critical concentration of the pathogen necessary for the pathogenesis of the seedling article, the sterilization rate is 60% or more, or the germ-bearing rate is 80% or less The seedling article according to claim 1, which is any one of the above.   A method for sterilizing seedling articles with iodine gas.   4. The method for sterilizing seedling articles according to claim 3, wherein the iodine gas is produced by sublimating solid iodine in a gaseous medium, and is performed by bringing a mixed gas of the iodine gas and the gaseous medium into contact with the seedling article.   The method for sterilizing seedling articles according to claim 3, wherein the iodine gas is generated by distributing the iodine gas to a gas phase part from an iodine-containing liquid sprayed on the seedling articles.   4. The method for sterilizing seedling articles according to claim 3, wherein the iodine gas is generated by sublimating solid iodine mixed with the seedling articles.   The method for sterilizing seedling articles according to any one of claims 3 to 6, wherein the iodine gas has a concentration of 0.1 to 10,000 ppm by volume.   The method for sterilizing seedling articles according to any one of claims 3 to 7, wherein the sterilization time with iodine gas is 1 second to 1 month.   9. The method for sterilizing seedling articles according to claim 3, wherein the product of the iodine gas concentration and the sterilization time is 100 ppm by volume to 50,000 ppm by volume. The method for sterilizing seedling articles according to any one of claims 3 to 9, wherein the sterilization temperature with iodine gas is 0 to 80 ° C.

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