Inhibitor of pollen dispersal of Cryptomeria japonica, Chamaecyparis obtusa, and Betula platyphylla var. japonica and method for suppressing pollen dispersal

Abstract

To provide a technique for inhibiting pollen dispersion with high efficiency based on a new action mechanism.SOLUTION: According to a discovery by the present inventors, pre-flowering male flowers of cedar, cypress, and Japanese white birch are treated with a compound that inhibits the elongation (flowering) of the male flowers or causes necrosis of them, thereby significantly inhibiting pollen dispersion from these flowers.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pollen scattering inhibitor for Cryptomeria japonica, Chamaecyparis obtusa, and Betula platyphylla containing, as an active ingredient, a compound that inhibits the elongation (flowering) of male flowers of Cryptomeria japonica, Chamaecyparis obtusa, and Betula platyphylla carrying pollen or causes necrosis of male flowers, and a method for inhibiting pollen scattering of Cryptomeria japonica, Chamaecyparis obtusa, and Betula platyphylla using the compound.

Background Art

[0002] Pollen, which is minute male reproductive cells formed in the anthers of stamens in angiosperms and in the pollen sacs of male flowers in gymnosperms, scatters into the external environment (air or water) or is transported by other vector organisms, and comes into contact with ovules having the same kind of female reproductive cells to effect pollination. When a person inhales pollen scattered in the air and it comes into contact with mucous membranes such as the nose and eyes, an allergic reaction to the pollen may occur, and a disease in which symptoms such as sneezing, runny nose, nasal congestion, and itching of the eyes occur due to this allergic reaction is called hay fever.

[0003] Known causative plants for hay fever include Cryptomeria japonica, Chamaecyparis obtusa, Betula platyphylla, Ambrosia artemisiifolia, Pinus spp., Gramineae plants, Artemisia princeps, etc. In particular, in Japan, hay fever caused by Cryptomeria japonica pollen in early spring is prominent. Approximately 80% of hay fever cases in Japan are caused by Cryptomeria japonica pollen, and Cryptomeria japonica hay fever is a national disease affecting 30% of the Japanese population.

[0004] Conventionally, various measures have been attempted to address hay fever, which significantly impairs the quality of life of many hay fever patients during the pollen scattering period. In addition to etiological therapies such as desensitization therapy to enhance resistance to allergens and improve constitution to relieve hay fever symptoms, administration of antihistamines and corticosteroids, and preventive measures such as eye drops and masks are taken. However, the most fundamental measure is to reduce the amount of pollen scattered into the air.

[0005] In the "Cabinet Ministers' Meeting on Hay Fever" established to discuss measures to address the hay fever problem across the boundaries of relevant government ministries and agencies, three main pillars of hay fever countermeasures have been set forth. That is, in order to achieve visible results in solving the social problem of hay fever, specific measures incorporated into 1. measures against the source of occurrence, 2. measures against dispersion, and 3. measures against onset and exposure will be implemented promptly with the government acting as one entity, eliminating vertical division of labor.

[0006] Among these, in the 2. measures against dispersion, the practical application of technologies to suppress the generation of cedar pollen and the development and popularization of cedar pollen dispersal inhibitors, etc., technologies to suppress the generation and prevent the dispersion of cedar pollen are being pursued, and various technological developments are being promoted accordingly.

[0007] For example, flower bud formation inhibitors for conifers such as the Cupressaceae and Taxodiaceae family containing maleic hydrazide or its salts as an active ingredient are known (Patent Document 1). This agent is applied to the leaf stalks during the flower bud formation period of conifers, and the application time for cedar is around June - September in summer.

[0008] In Patent Document 2 reporting a pollen dispersal inhibitor containing a surfactant emulsion of oleic acid or / and linoleic acid (plant oil) as an active ingredient, it is considered that ethylene production, which acts as a plant hormone, is induced in cedar to which the agent is applied, and the generated ethylene rapidly promotes the respiration of pollen, in other words, accelerates the consumption of pollen, rapidly aging and killing the pollen. Regarding the application time, it is indicated that the agent should be sprayed on male flowers around October when pollen maturation can be observed. Also, in Patent Documents 3 - 8, various derivatives of oleic acid or linoleic acid are disclosed as active ingredients of pollen dispersal inhibitors, and it is recommended that these be applied from August to November before the pollen grains mature in the early stage of male flower formation in cedar.

[0009] In Patent Document 9, which suppresses pollen scattering by infecting and withering male flowers with the mycelium of *Sydowia japonica*, the mycelium suspension is applied from October to November in autumn. In addition to the above, techniques for suppressing pollen scattering by inhibiting flower bud formation using polyhydric alcohol esters of fatty acids having 2 to 12 carbon atoms (such as acetic acid, capric acid, caprylic acid, or lauric acid), acetolactate synthase inhibitors, and gibberellin biosynthesis inhibitors have been reported (Patent Documents 10 to 13).

[0010] Thus, attempts to suppress pollen scattering by applying agents that inhibit pollen formation in Japanese cedar male flowers are being researched and developed in various places, but at present, no agent that exhibits sufficient effects has been found. Therefore, the development of a new technology that suppresses pollen scattering with high efficiency based on an action mechanism different from those of conventionally known ones can greatly meet the social demand for suppressing extensive health damage caused by pollinosis and is expected to have high demand.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Summary of the Invention

Problems to be Solved by the Invention

[0012] The present invention relates to a pollen scattering inhibitor containing, as an active ingredient, a compound that inhibits the elongation (flowering) of Cryptomeria japonica, Chamaecyparis obtusa, or Populus sieboldii male flowers carrying pollen or causes male flowers to necrotize, and a method for suppressing pollen scattering using the compound.

Means for Solving the Problems

[0013] The inventors have found that by applying (2-chloroethyl)phosphonic acid (also known as ethephon or Ethrel (registered trademark)) or jasmonic acid to male flowers in early February immediately before the elongation (flowering) of Cryptomeria japonica male flowers, a pollen scattering inhibitory effect can be obtained. The conventional Cryptomeria japonica pollen scattering inhibitors exemplified above solely reduce the pollen production amount by inhibiting the flower bud formation and pollen formation processes of Cryptomeria japonica male flowers. Among the above prior art documents, the only substance that suppresses pollen scattering by inhibiting the flowering of male flowers that have already been formed is the 3-oxobutanoic acid ester of Patent Document 13, which is a different type of substance not related to (2-chloroethyl)phosphonic acid and jasmonic acid according to the present invention.

[0014] In addition, the inventors have also found that, similarly in the male flowers of Japanese cypress, by applying (2-chloroethyl)phosphonic acid or jasmonic acid to the male flowers in early March immediately before the flowering of the male flowers of Japanese cypress, a pollen scattering inhibitory effect can be obtained. Although both Japanese cedar and Japanese cypress belong to the family Cupressaceae, they are separate tree species that should not be grouped together. The fact that the pollen scattering inhibitor of the present invention, which has shown a pollen scattering inhibitory effect in Japanese cedar, also shows a similarly good pollen scattering inhibitory effect in Japanese cypress is an advantageous feature of the present invention.

[0015] Furthermore, the inventors have found that by applying salicylic acid to the male flowers of Japanese cedar from late December, about two months before the flowering of the male flowers, to mid-February, two weeks before the flowering, a pollen scattering inhibitory effect due to stronger male flower necrosis than that of the above-mentioned (2-chloroethyl)phosphonic acid or jasmonic acid can be obtained. In the male flowers of Japanese cypress as well, a strong pollen scattering inhibitory effect due to similar male flower necrosis was recognized by applying it to the male flowers in mid-February, about one month before the flowering. Furthermore, in the male flowers of sawara cypress as well, a strong pollen scattering inhibitory effect due to similar male flower necrosis was obtained by applying it to the male flowers in mid-March, about one month before the flowering.

[0016] Since the pollen scattering inhibition of the present invention is based on the action of inhibiting the flowering of male flowers immediately before flowering as described above, it is applied at a time later than summer to autumn when flower bud formation and pollen formation of male flowers of Japanese cedar, which are the action targets of conventional agents, occur, and immediately before winter to early spring before flowering. In addition, since the mechanism of action and the application time are different from those of conventional inhibitors, when the agent of the present invention is applied in combination with those conventional agents, the effects do not overlap, and there is also a possibility of exhibiting an additive or synergistic scattering inhibitory effect.

[0017] Therefore, the present application provides the following inventions.

[0018] 1. A composition for inhibiting the scattering of pollen of Japanese cedar or Japanese cypress, containing, as an active ingredient, a compound that inhibits the elongation (flowering) of male flowers carrying pollen or causes male flowers to necrose, and the compound is selected from the group consisting of (2-chloroethyl)phosphonic acid, jasmonic acid, and their physiologically acceptable salts or esters. 2. A composition for suppressing the scattering of pollen of Cryptomeria japonica, Chamaecyparis obtusa or Betula platyphylla, which contains, as an active ingredient, a compound that inhibits the elongation (flowering) of male flowers carrying pollen or causes male flowers to necrotize, and the compound is selected from the group consisting of salicylic acid and its physiologically acceptable salts or esters. 3. The composition according to any one of items 1 or 2, formulated in a form suitable for spraying, applying or dipping application onto the surface of male flowers carrying the pollen. 4. A method for suppressing the scattering of pollen of Cryptomeria japonica or Chamaecyparis obtusa, which includes the step of applying, in an effective amount, an agent containing a compound that inhibits the elongation (flowering) of male flowers carrying pollen to the male flowers of Cryptomeria japonica and Chamaecyparis obtusa, and the compound is selected from the group consisting of (2-chloroethyl)phosphonic acid, jasmonic acid, and their physiologically acceptable salts or esters. 5. A method for suppressing the scattering of pollen of Cryptomeria japonica, Chamaecyparis obtusa or Betula platyphylla, which includes the step of applying, in an effective amount, an agent containing a compound that inhibits the elongation (flowering) of male flowers carrying pollen or causes male flowers to necrotize to the male flowers of Cryptomeria japonica, Chamaecyparis obtusa or Betula platyphylla, and the compound is selected from the group consisting of salicylic acid and its physiologically acceptable salts or esters. 6. The method according to any one of items 4 or 5, wherein the application of the agent to the male flowers carrying the pollen is performed by spraying, applying or dipping the agent onto the surface of the male flowers. 7. The method according to any one of items 4 or 5, wherein the application of the agent to the male flowers carrying the pollen is performed between 8 weeks before and 1 week before the time when the flowering of the male flowers starts. 8. The method according to item 4, wherein the agent is applied to the surface of male flowers as an aqueous solution of 0.5 to 10% by weight of (2-chloroethyl)phosphonic acid. 9. The method according to item 4, wherein the agent is applied to the surface of male flowers as an aqueous solution of 0.1 to 2% by weight of jasmonic acid. 10. The method according to item 5, wherein the agent is applied to the surface of male flowers as an aqueous solution of 0.1 to 1% by weight of salicylic acid.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0030] The plants to which the pollen dispersal inhibitor of the present invention is applied are trees whose pollen causes hay fever, preferably Japanese cedar, Japanese cypress, and white birch.

[0031] Both Japanese cedar and Japanese cypress belong to the Cupressaceae family, but among the Cupressaceae family, it is only Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) that cause hay fever. Both have been used in Japan for a long time as timber, garden trees, and street trees. Especially in response to the increase in timber demand during the high economic growth period after the war, the afforestation of Japanese cedar and Japanese cypress was actively carried out. Subsequently, due to the decrease in demand, logging has stagnated, and currently, artificial forests of Japanese cedar or Japanese cypress occupy nearly 30% of Japan's forest area.

[0032] However, it should be noted that Japanese cedar and Japanese cypress are separate tree species that should not be grouped together. Therefore, in the prior art exemplified above, those that only report the suppression of pollen dispersal in Japanese cedar and make no mention of Japanese cypress should be considered to have no pollen suppression effect on Japanese cypress. In this regard, the fact that the pollen dispersal inhibitor of the present invention exhibits a good pollen dispersal inhibition effect as described below in both of the two separate tree species of Japanese cedar and Japanese cypress is an advantageous feature of the present invention.

[0033] In addition, since there is a difference of several months between the time when flower bud formation of male flowers occurs and the time when flowering occurs in Cryptomeria japonica and Chamaecyparis obtusa, the application time of the pollen dispersal inhibitor of the present invention to be applied immediately before flowering differs between the case of Cryptomeria japonica and the case of Chamaecyparis obtusa. For example, in an area where Cryptomeria japonica flowers in March and Chamaecyparis obtusa flowers in April, the application time of the pollen dispersal inhibitor of the present invention is considered around February and March, respectively. Preferably, the pollen dispersal inhibitor of the present invention is applied 8 weeks, 7 weeks, 6 weeks, 5 weeks, 4 weeks, 3 weeks, 2 weeks, or 1 week before the time when flowering of the target Cryptomeria japonica or Chamaecyparis obtusa male flowers starts.

[0034] Alnus hirsuta is a deciduous broad-leaved tree belonging to the family Betulaceae. Pollen scatters in spring and causes hay fever. However, since it is rarely artificially forested and its distribution is limited to highlands and cold regions, the damage is limited compared to Cryptomeria japonica and Chamaecyparis obtusa. However, in regions such as Hokkaido where many Alnus hirsuta grow, the incidence of hay fever also increases because the opportunity to come into contact with Alnus hirsuta pollen increases. In addition, since Alnus hirsuta forests are mainly natural forests, it is difficult to adjust the amount of pollen dispersal by logging like in artificial forests of Cryptomeria japonica and Chamaecyparis obtusa. Also, as described above, the pollen dispersal inhibitor may have different effects depending on the species, so a pollen dispersal inhibitor developed specifically for Cryptomeria japonica pollen may have no effect on Alnus hirsuta. Therefore, Alnus hirsuta hay fever should usually be treated separately from Cryptomeria japonica or Chamaecyparis obtusa hay fever. In this regard, among the pollen dispersal inhibitors of the present invention, those using salicylic acid as an active ingredient show a strong pollen dispersal inhibitory effect on Alnus hirsuta as well as on Cryptomeria japonica and Chamaecyparis obtusa, as described below, which is a particularly remarkable feature of the present invention.

[0035] The Cryptomeria japonica and Chamaecyparis obtusa to which the pollen dispersal inhibitor of the present invention is applied to suppress the dispersal of pollen can be any Cryptomeria japonica and Chamaecyparis obtusa trees that form and release pollen, such as natural or artificial forests, street trees, garden trees, and hedges. Also, as shown in the examples, the pollen dispersal from cut branches collected from trees can be suppressed.

[0036] The pollen dispersal inhibitor of the present invention contains, as an active ingredient, a compound that inhibits the elongation (flowering) of male flowers carrying the pollen of the target tree or causes necrosis of male flowers. Plant hormones such as ethylene, jasmonic acid, and salicylic acid have an effect of inhibiting growth and promoting aging in plants.

[0037] In one aspect, the pollen dispersal inhibitor of the present invention contains, as an active ingredient, (2-chloroethyl)phosphonic acid (also referred to as ethephon or Ethrel (registered trademark)). (2-chloroethyl)phosphonic acid itself is a known compound (CAS RN 16672-87-0), and the pollen dispersal inhibitor of the present invention can be constituted with a commercially available single compound (for example, Tokyo Chemical Industry product code: C1456) or a commercially available ethephon preparation (for example, Ishihara Ethrel (registered trademark) 10 (Ishihara Bioscience Co., Ltd.) or Nissan Ethrel (registered trademark) 10 (Nissan Chemical Industries, Ltd.)) as the active ingredient. (2-chloroethyl)phosphonic acid is a derivative of ethylene that acts as a plant hormone and causes various physiological responses induced by ethylene in the target plants sprayed in liquid form. The suppression of male flower flowering in the present invention is considered to be a physiological response to ethylene. The pollen dispersal inhibitor of the present invention is applied in an amount sufficient for cedar and cypress to exhibit such a physiological response to ethylene.

[0038] In one aspect, the pollen dispersal inhibitor of the present invention contains jasmonic acid as an active ingredient. Jasmonic acid itself is a known compound (CAS 221682-41-3) and is commercially available as a single compound (for example, Tokyo Chemical Industry product code: J0004). Jasmonic acid is a plant hormone that induces various physiological responses in plants, similar to the above-mentioned ethylene. It suppresses the male flower flowering of cedar and cypress in the same way as (2-chloroethyl)phosphonic acid, but such suppression is caused by a different system from ethylene.

[0039] In one aspect, the pollen dispersal inhibitor of the present invention contains salicylic acid as an active ingredient. Salicylic acid is a known aromatic compound naturally contained in plants and exists in the form of methyl salicylate and salicin in plants. Salicylic acid is involved in the resistance of plants to pathogenic microorganisms and is regarded as a plant hormone that acts antagonistically to jasmonic acid. Similar to (2-chloroethyl)phosphonic acid and jasmonic acid, it inhibits the male flower blooming of Cryptomeria japonica and Chamaecyparis obtusa, but such inhibition is more drastic than leading to male flower necrosis, and the same inhibitory effect is also observed in Quercus serrata, and the phytotoxicity to other plant species is remarkable in that it is milder compared to (2-chloroethyl)phosphonic acid and jasmonic acid.

[0040] The appropriate application amount of the pollen dispersal inhibitor of the present invention sufficient to achieve pollen dispersal inhibition can be determined by those skilled in the art through normal condition consideration. As described later, since the application of the pollen dispersal inhibitor of the present invention may cause phytotoxicity to other plants, the application amount can be determined in consideration of the influence on the surrounding environment of the pollen dispersal inhibitor of the present invention.

[0041] The pollen dispersal inhibitor of the present invention can be prepared as a composition in any suitable form such as an aqueous solution or suspension, an oily solution or suspension, an emulsion, an aerosol, a powder, a granule, etc. Such a pollen dispersal inhibitor of the present invention can be used as it is in the stock solution, or can be diluted, dissolved or suspended with a predetermined liquid and used. How to prepare the pollen dispersal inhibitor of the present invention is a matter that can be appropriately determined by those skilled in the art in consideration of the actual application conditions.

[0042] In a preferred aspect, the pollen dispersal inhibitor of the present invention is applied to the surface of male flowers as an aqueous solution of 0.5 to 10% by weight of (2-chloroethyl)phosphonic acid. In another preferred aspect, the pollen dispersal inhibitor of the present invention is applied to the surface of male flowers as an aqueous solution of 0.1 to 2% by weight of jasmonic acid. In still another preferred aspect, the pollen dispersal inhibitor of the present invention is applied to the surface of male flowers as an aqueous solution of 0.1 to 1% by weight of salicylic acid.

[0043] In one aspect, (2-chloroethyl)phosphonic acid, jasmonic acid, or salicylic acid, which is contained as an active ingredient in the pollen dispersal inhibitor of the present invention, may be in the form of their phytophysiologically acceptable salts or esters. Examples of the salts include alkali metal salts such as sodium and potassium, and alkaline earth metal salts such as calcium and magnesium. Examples of the esters of aromatic compounds include alkyl esters such as methyl ester and ethyl ester.

[0044] The pollen dispersal inhibitor of the present invention suppresses the dispersal of pollen from male flowers by suppressing the elongation (flowering) of the applied male flowers. Therefore, the application time of the agent is set before the male flowers bloom. For example, the agent can be applied 8 weeks, 7 weeks, 6 weeks, 5 weeks, 4 weeks, 3 weeks, 2 weeks, or 1 week before the predicted date when pollen dispersal begins. Since the pollen dispersal time of Japanese cypress is later than that of Japanese cedar, the application time of the agent to Japanese cypress in the same area can be later than that to Japanese cedar. For example, in an area where the pollen dispersal time of Japanese cedar is recognized as March and that of Japanese cypress is recognized as April, the agent of the present invention can be applied to Japanese cedar from January to February and to Japanese cypress from February to March.

[0045] Since the pollen dispersal inhibitor of the present invention is applied immediately before the male flowers bloom, it is applied later than the pollen dispersal inhibitors that suppress flower bud formation and pollen maturation as in the prior art. For example, in Patent Document 4 (Japanese Patent Application Laid-Open No. 2009-191053), it is described that the application time can be "sprayed over a relatively long period from August when male flowers are borne to October to November when pollen grains are produced", and it does not overlap with the normal application time of the present invention from January to March (8 to 1 week before the start of Japanese cedar male flower blooming in March).

[0046] The pollen dispersal inhibitor of the present invention inhibits the dispersal of pollen from the opened male flowers by inhibiting the flowering of male flowers or causing male flowers to necrose. By applying the inhibitor to the target tree, the amount of subsequent pollen dispersal decreases significantly compared to the case where it is not applied. For example, the amount of pollen dispersal of Cryptomeria japonica and Chamaecyparis obtusa to which the pollen dispersal inhibitor of the present invention is applied decreases in a dose-dependent manner, and when an excessive dose is applied, male flowers necrose and 100% pollen dispersal can be suppressed. However, since the active ingredient of the present invention may cause phytotoxicity to various plant species as described below, application conditions can be set in consideration of the desired pollen dispersal inhibition and the impact on the surrounding environment.

Example

[0047] Example 1: Application of an ethephon hydrochloric acid aqueous solution to Cryptomeria japonica 10%, 1%, and 0.1% ethephon solutions prepared by dissolving ethephon (manufactured by Tokyo Chemical Industry) in a hydrochloric acid aqueous solution (0.01 mol / l), and a hydrochloric acid aqueous solution (0.01 mol / l) as a control were used to soak cut branches collected on February 9, 2021, about two weeks before the flowering of Cryptomeria japonica male flowers, immerse them in male flowers, and place them at room temperature. For water soaking, a flower form (DCM Holdings) for fresh flowers was used to hold the male flower spikes so that pollen would fall into a 5 ml plastic container. After 18 days, the weight of the pollen dispersed for each branch was measured and the number of male flowers was counted to determine the weight of the pollen dispersed per male flower.

[0048] The amount of pollen dispersal in the 1% ethephon treatment was 35.5% of the dispersal amount in the control, and an effect of suppressing the pollen dispersal of Cryptomeria japonica was obtained (Figure 2). On the other hand, in the 0.1% ethephon treatment, no effect of suppressing the pollen dispersal of Cryptomeria japonica was obtained. In the 10% ethephon treatment, the branches and male flowers necrosed and did not flower. Also, in the 1% ethephon treatment in the field, there were no external changes in the branches and leaves of Cryptomeria japonica, and no phytotoxicity was observed.

[0049] Example 2: Treatment of an ethephon hydrochloric acid aqueous solution on Chamaecyparis obtusa Etophon (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in an aqueous hydrochloric acid solution (0.01 mol / l) to prepare 10%, 1%, and 0.1% etophon solutions. As a control, an aqueous hydrochloric acid solution (0.01 mol / l) was used. Cuttings collected on March 4, 2021, approximately two weeks before the flowering of Chamaecyparis obtusa male flowers were water - inserted, immersed in male flowers, and placed at room temperature. For water - insertion, a flower form for fresh flowers (DCM Holdings) was used, and the branches were covered with paraffin paper bags to collect the fallen pollen. After 22 days, the weight of the scattered pollen per branch was measured and the number of male flowers was counted to determine the weight of the scattered pollen per male flower.

[0050] The amount of pollen scattered in the 1% etophon treatment was 29.5% of the amount scattered in the control, and an effect of suppressing the pollen scattering of Chamaecyparis obtusa was obtained (Figure 3). On the other hand, in the 0.1% etophon treatment, no effect of suppressing the pollen scattering of Chamaecyparis obtusa was obtained. In the 10% etophon treatment, the branches and male flowers necrosed and did not flower. Also, in the 1% etophon treatment in the field, there were no apparent changes in the branches and leaves of Chamaecyparis obtusa, and no phytotoxicity was observed.

[0051] Example 3: Application of Esrel (registered trademark) treatment solution to Cryptomeria japonica Commercially available plant growth regulator Ishihara Esrel (registered trademark) 10 (manufactured by Ishihara Bioscience Co., Ltd., ethephon concentration 10%) was diluted 10 - fold, 100 - fold, 1000 - fold, and 10000 - fold with deionized water to prepare 1%, 0.1%, 0.01%, and 0.001% treatment solutions, an undiluted 10% treatment solution, and deionized water. These were immersed in the male flowers of Cryptomeria japonica planted in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute on January 11, 2018, approximately one month before the flowering of Cryptomeria japonica male flowers. On February 27, 2018, the branches with the treated male flowers were collected, water - inserted indoors to make them flower, and the pollen was collected. Water - insertion was carried out by putting water in a plastic container, and plastic containers were used for the pollen trap for each branch. The pollen weight was measured and the number of male flowers was counted for each branch to determine the weight of the scattered pollen per male flower.

[0052] The amount of pollen dispersal in the 1% treatment was 15.2% of that in the water treatment, and the effect of suppressing sugi pollen dispersal was obtained (Figure 4). On the other hand, no effect of suppressing sugi pollen dispersal was obtained with the 0.1%, 0.01%, and 0.001% treatment solutions. Also, no external changes were observed in the branches and leaves of sugi with the 1% treatment and the 0.1%, 0.01%, and 0.001% treatment solutions. Note that with the 10% treatment solution, the branches and male flowers necrotized and did not bloom.

[0053] Example 4: Application of Ethrel (registered trademark) treatment solution to Chamaecyparis obtusa A 1% treatment solution obtained by diluting 10-fold with water the commercially available plant growth regulator, Ishihara Ethrel (registered trademark) 10 (manufactured by Ishihara Bioscience Co., Ltd., ethephon concentration 10%), and water were immersed in the male flowers of Chamaecyparis obtusa planted in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute on February 12, 2020, about one month before the flowering of the male flowers of Chamaecyparis obtusa. On March 22, 2020, the branches with the treated male flowers were collected, water cuttaged to make them bloom, and the pollen was collected. For water cuttage, a flower form (DCM Holdings) for fresh flowers was used, the branches were covered with paraffin paper bags, and the fallen pollen was collected. The pollen weight was measured for each branch, the number of male flowers was counted, and the weight of the dispersed pollen per male flower was determined.

[0054] The amount of pollen dispersal in the 1% treatment was 11.2% of that in the water treatment, and the effect of suppressing Chamaecyparis obtusa pollen dispersal was obtained (Figure 5). Also, no external changes were observed in the branches and leaves of Chamaecyparis obtusa with the 1% treatment.

[0055] Example 5: Application of jasmonic acid treatment solution to Cryptomeria japonica After dissolving jasmonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) in a small amount of ethanol, 1%, 0.1%, and 0.01% jasmonic acid solutions with water added, and water as a control were immersed in male sugi flowers in the field on January 17 and February 7, 2022. On March 2, 2022, just before the flowering of male sugi flowers, 10 branches each containing the treated male flowers were collected and placed in water cuttings at room temperature. For the water cuttings, a flower form for fresh flowers (DCM Holdings) was used to hold the male flower spikes so that pollen would fall into a 5 ml plastic container. After 11 days, the weight of the scattered pollen per branch was measured and the number of male flowers was counted to determine the weight of the scattered pollen per male flower.

[0056] The amount of pollen scattering in the 1% jasmonic acid treatment was 19.8% in the January treatment and 9.9% in the February treatment compared to the scattering amount in the control, and an effect of suppressing sugi pollen scattering was obtained. Also, the amount of pollen scattering in the 0.1% jasmonic acid treatment was 45.8% in the February treatment compared to the scattering amount in the control, and an effect of suppressing sugi pollen scattering was obtained, but no effect was observed in the January treatment. In the 0.01% jasmonic acid treatment, no effect of suppressing sugi pollen scattering was obtained in either the January treatment or the February treatment (Figure 6).

[0057] Example 6: Application of Jasmonic Acid Treatment Solution to Chamaecyparis obtusa After dissolving jasmonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) in a small amount of ethanol, a 1% jasmonic acid solution with water added, and water as a control were applied with a brush to male Chamaecyparis obtusa flowers in the field on February 9, 2022. On March 28, 2022, just before the flowering of male Chamaecyparis obtusa flowers, 8 branches each containing the treated male flowers were collected and placed in water cuttings at room temperature. For the water cuttings, a flower form for fresh flowers (DCM Holdings) was used to hold the male flowers so that pollen would fall into a 5 ml plastic container. After 4 days, the weight of the scattered pollen per branch was measured and the number of male flowers was counted to determine the weight of the scattered pollen per male flower.

[0058] The amount of pollen scattering in the 1% jasmonic acid treatment was 10.7% compared to the scattering amount in the control, and an effect of suppressing Chamaecyparis obtusa pollen scattering was obtained (Figure 7).

[0059] Example 7: Application of Salicylic Acid Treatment Solution to Cryptomeria japonica A 1% sodium salicylate solution prepared by dissolving sodium salicylate (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) in deionized water, a 0.1% sodium salicylate solution obtained by diluting this 10-fold with deionized water, and control deionized water were immersed in the male flowers of Cryptomeria japonica planted in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute on December 28, 2022 (about 2 months before the predicted male flower blooming date of Cryptomeria japonica on February 28, 2023), January 20, 2023 (about 1 month before), and February 11, 2023 (about 2 weeks before). On March 28, 2023, when the control male flowers had finished blooming, 10 branches each with the treated male flowers were collected. The male flowers were removed from each male flower spike, photographed, and it was determined whether they had bloomed or not. The flowering rate of the total number of male flowers in 10 male flower spikes was calculated. The flowering rate of the December treatment was 0% for the 1% salicylic acid treatment, 100% for the control, 0% for the 1% salicylic acid treatment, 34.7% for the 0.1% salicylic acid treatment, and 99.0% for the control in the January treatment, and 0% for the 1% salicylic acid treatment, 79.1% for the 0.1% salicylic acid treatment, and 93.8% for the control in the February treatment. In all treatments at any time, the 1% salicylic acid treatment could suppress flowering by causing rapid necrosis of the male flowers, and an effect of suppressing the dispersal of Cryptomeria japonica pollen was obtained (Figure 8). Also, there were no apparent changes in the branches and leaves other than the male flower spikes of Cryptomeria japonica, and no phytotoxicity was observed.

[0060] Example 8: Application of Salicylic Acid Treatment Solution to Chamaecyparis obtusa A 1% sodium salicylate solution prepared by dissolving sodium salicylate (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) in deionized water and deionized water as a control were spray-treated on the branches of Japanese cypress planted in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute on February 25, 2023 (about one month before the predicted flowering date of Japanese cypress male flowers on March 25). On March 29, 2023, when the control male flowers bloomed, 15 branches were collected for each treatment. The male flowers were removed from each branch and photographed, and the flowering rate of each branch was determined by judging the flowering or non-flowering of the male flowers in the photograph. The average flowering rate of the 15 branches for each treatment was calculated. The average flowering rate of the Japanese cypress treated by spray was 36.6% for the 1% salicylic acid treatment and 78.1% for the control. The 1% salicylic acid treatment could suppress flowering by causing necrosis of male flowers, and an effect of suppressing the scattering of Japanese cypress pollen was obtained (Fig. 9). In addition, there were no external changes in the branches and leaves of Japanese cypress, and no phytotoxicity was observed.

[0061] Example 9: Application of salicylic acid treatment solution to Japanese white birch A 1% sodium salicylate solution prepared by dissolving sodium salicylate (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) in deionized water, a 0.1% sodium salicylate solution obtained by diluting this 10-fold with deionized water, and deionized water as a control were applied to the male inflorescences attached to 1 to 4 branches at the tips of the branches of Japanese white birch planted in the Tohoku Branch of the Forestry and Forest Products Research Institute on March 17, 2023 (about one month before the predicted flowering date of Japanese white birch male inflorescences on April 17). The number of male inflorescences treated was 39 for the 1% salicylic acid treatment, 21 for the 0.1% salicylic acid treatment, and 18 for the control. On April 24, 2023, when the control male inflorescences bloomed, the flowering or non-flowering of each male inflorescence was judged, and the flowering rate was determined. The flowering rates were 23.1% for the 1% salicylic acid treatment, 72.7% for the 0.1% salicylic acid treatment, and 77.8% for the control. The 1% salicylic acid treatment could suppress the flowering of Japanese white birch male inflorescences, and an effect of suppressing the scattering of Japanese white birch pollen was obtained (Fig. 10). In addition, there were no external changes in the branches and leaves other than the male inflorescences of Japanese white birch, and no phytotoxicity was observed.

[0062] Example 10: Examination of the application time of Esrel (registered trademark) treatment solution to Japanese cedar A 1% Ethephon (registered trademark) treatment solution obtained by diluting the commercially available plant growth regulator Ethephon (registered trademark) (Nissan Ethephon 10, ethephon concentration 10%) 10-fold with deionized water, and deionized water were used to immerse the male flowers of Cryptomeria japonica planted in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute on December 28, 2021, about 2 months before the flowering of the male flowers of Cryptomeria japonica, on January 17, 2022, about 1 month before, and on February 7, 2022, about 2 weeks before. On March 2, 2022, when the flowering was much later than usual, 10 branches each with male flowers treated were collected for each treatment, placed in water cuttings indoors to make them flower, and the pollen was collected. For the water cuttings, a flower form for fresh flowers (DCM Holdings) was used to hold the male flower spikes so that the pollen would fall into a 5 ml plastic container. The pollen weight of each branch was measured and the number of male flowers was counted, and the weight of the scattered pollen per male flower was determined.

[0063] The amount of pollen scattering in the 1% Ethephon (registered trademark) treatment was 66.1% in the December treatment, 46.5% in the January treatment, and 13.8% in the February treatment compared to the amount of scattering in the control, and the effect of suppressing the pollen scattering of Cryptomeria japonica was obtained at 50% or less in the January treatment and the February treatment (Figure 11). Also, there were no external changes in the branches and leaves of Cryptomeria japonica, and no phytotoxicity was observed.

[0064] Example 11: Phytotoxicity test of (2-chloroethyl)phosphonic acid Since ethylene produced by (2-chloroethyl)phosphonic acid has a wide range of physiological effects on plants in general, there is a possibility of phytotoxicity occurring in surrounding plants when implementing the pollen scattering suppression of the present invention. Examination was conducted on the possibility of such phytotoxicity occurring.

[0065] A 1% treatment solution (containing 1% ethephon) obtained by diluting Nissan Ethephon (registered trademark) 10 (manufactured by Nissan Chemical Industries, Ltd., ethephon concentration 10%) 10-fold with deionized water was prepared. On January 21, 2021, in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute in Kyoto City, the 1% treatment solution was applied by spraying to 38 types of plants. Thereafter, visual inspections were conducted on February 8, March 8, and April 2, and those with any phytotoxicity were regarded as having phytotoxicity. The results of this test are summarized in the following table.

Table 1

[0066] Among the 38 plant species investigated, phytotoxicity was observed in 14 species (37%). Specifically, among 4 evergreen coniferous tree species, 25 evergreen broad-leaved tree species, and 9 deciduous broad-leaved tree species, the percentages of species with some phytotoxicity such as twig blight and leaf drop were 0%, 52%, and 11% respectively. As representative examples of the observed phytotoxicity, in evergreen broad-leaved trees such as Nanten, Senryo, and Manryo, twig blight with the greatest degree of damage occurred. Also, in Pittosporum tobira, Croton tiglium, and Camellia sasanqua, leaf drop occurred. Among deciduous broad-leaved trees, phytotoxicity was observed only in Prunus mume, and early flower drop occurred after the buds bloomed.

[0067] Example 12: Phytotoxicity Test of Jasmonic Acid Jasmonic acid (manufactured by Tokyo Chemical Industry) was dissolved in a small amount of ethanol, and then a 1% jasmonic acid solution was prepared by adding water. On February 9, 2022, in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute in Kyoto City, the jasmonic acid solution was applied to 68 plant species with a pen. Subsequently, visual inspections were conducted on February 28, March 25, and April 14, and those with any phytotoxicity by April 14 were regarded as having phytotoxicity. The results of this test are summarized in the following table.

Table 2

[0068] Among the 68 plant species investigated, phytotoxicity was observed in 7 species (10%). Specifically, among 9 evergreen coniferous tree species, 34 evergreen broad-leaved tree species, and 25 deciduous broad-leaved tree species, the percentages of species with some phytotoxicity such as twig blight and leaf drop were 11%, 15%, and 4% respectively. As representative examples of the plants with observed phytotoxicity, in evergreen coniferous tree Cryptomeria japonica var. sinensis, and in evergreen broad-leaved trees Manryo and Croton tiglium, leaf drop occurred. Among deciduous broad-leaved trees, phytotoxicity was observed only in Prunus mume, and the flowering was slightly delayed.

[0069] Therefore, since the application of the pollen dispersal inhibitor of the present invention at a dose sufficient to achieve pollen dispersal inhibition may cause phytotoxicity to other plants, attention to the surrounding environment may be required in practice.

[0070] Example 13: Phytotoxicity test of salicylic acid A 1% sodium salicylate solution was prepared by dissolving sodium salicylate (FUJIFILM Wako Pure Chemical Industries, special grade reagent) in deionized water. On February 3, 2023, in the experimental forest of the Kansai Branch of the Forestry and Forest Products Research Institute in Kyoto City, a 1% sodium salicylate solution was sprayed onto 69 types of plants by spraying. Then, visual inspections were conducted on February 17, March 24, and April 27, and those with any phytotoxicity by April 27 were regarded as having phytotoxicity. The results of this test are summarized in the following table.

Table 3

[0071] Among the 69 types of plants investigated, phytotoxicity was observed in 15 types (22%). Specifically, among 8 types of evergreen conifers, 36 types of evergreen broad-leaved trees, and 25 types of deciduous broad-leaved trees, the percentages of species with any phytotoxicity such as browning or leaf drop were 25%, 36%, and 0%, respectively. As the observed phytotoxicity, in evergreen conifers, needle browning occurred in Cryptomeria japonica and Chamaecyparis obtusa, in evergreen broad-leaved trees, leaf drop occurred in Ilex crenata and Nandina domestica, and slight leaf browning occurred in Camellia japonica and Camellia sinensis, etc., but all of them were minor. No phytotoxicity was observed in deciduous broad-leaved trees.

[0072] Therefore, the application of salicylic acid at a dose sufficient to achieve pollen dispersal inhibition is less phytotoxic to other plants than in the case of (2-chloroethyl)phosphonic acid or jasmonic acid. However, the possibility that some phytotoxicity may occur to other plants due to the application of salicylic acid acting as a plant hormone should not be ignored, and attention to the surrounding environment may still be required in practice.

Claims

1. A composition for suppressing the scattering of Cryptomeria japonica or Chamaecyparis obtusa pollen, comprising, as an active ingredient, a compound that inhibits the elongation (flowering) of male flowers carrying pollen or causes male flowers to necrotize, wherein the compound is selected from the group consisting of (2-chloroethyl)phosphonic acid, jasmonic acid, and their physiologically acceptable salts or esters.

2. A composition for suppressing the scattering of Cryptomeria japonica, Chamaecyparis obtusa or Betula platyphylla pollen, comprising, as an active ingredient, a compound that inhibits the elongation (flowering) of male flowers carrying pollen or causes male flowers to necrotize, wherein the compound is selected from the group consisting of salicylic acid and its physiologically acceptable salts or esters.

3. The composition according to any one of Claims 1 or 2, formulated in a form suitable for spraying, coating or dipping application onto the surface of male flowers carrying the pollen.

4. A method for suppressing the scattering of Cryptomeria japonica or Chamaecyparis obtusa pollen, comprising the step of applying an agent containing a compound that inhibits the elongation (flowering) of male flowers carrying pollen to the male flowers of Cryptomeria japonica and Chamaecyparis obtusa, wherein the compound is selected from the group consisting of (2-chloroethyl)phosphonic acid, jasmonic acid, and their physiologically acceptable salts or esters.

5. A method for suppressing the scattering of Cryptomeria japonica, Chamaecyparis obtusa or Betula platyphylla pollen, comprising the step of applying an agent containing a compound that inhibits the elongation (flowering) of male flowers carrying pollen or causes male flowers to necrotize to the male flowers of Cryptomeria japonica, Chamaecyparis obtusa or Betula platyphylla, wherein the compound is selected from the group consisting of salicylic acid and its physiologically acceptable salts or esters.

6. The method according to any one of Claims 4 or 5, wherein the application of the agent to the male flowers carrying the pollen is performed by spraying, coating or dipping the agent onto the surface of the male flowers.

7. The method according to any one of Claims 4 or 5, wherein the application of the agent to the male flowers carrying the pollen is performed between 8 weeks and 1 week before the start of flowering of the male flowers.

8. The method according to Claim 4, wherein the agent is applied to the surface of male flowers as an aqueous solution of 0.5 to 10% by weight of (2-chloroethyl)phosphonic acid.

9. The method according to Claim 4, wherein the agent is applied to the surface of male flowers as an aqueous solution of 0.1 to 2% by weight of jasmonic acid.

10. The method according to Claim 5, wherein the agent is applied to the surface of male flowers as an aqueous solution of 0.1 to 1% by weight of salicylic acid.

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