JP2007332110A - Agent for controlling clubroot and method for controlling clubroot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for effectively activating the latent resisting mechanism of plants against diseases and provide an agent and a method for controlling diseases, effective for controlling clubroot disease of plants of the family Brassicaceae such as cabbage and highly safe to the environment and human body. <P>SOLUTION: At least one kind of microorganism selected from Sphingomonas TF1401 (FERM P-20899) and Sphingomonas TF1402 (FERM P-20900) is applied to a plant of the family Brassicaceae in combination with an oligomerized chitin obtained by the hydrolysis of chitin and having a number-average molecular weight of 3,000-50,000. The invention is preferably usable to plants of the family Brassicaceae such as cabbage, Chinese cabbage, turnip, Japanese radish, cauliflower, broccoli, Japanese horseradish, Santo-sai (Brassica campestris), Tai-sai (Brassica rapa var. chinensis), Komatsu-na (Suaeda ghuca), Nozawa-na (Brassica rapa var. hakabura), Karashina (Brassica juncea), Takana (Brassica juncea var. Integlifolia), kailang, watercress and kale. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an agent for controlling a clubroot disease for suppressing a disease of a plant disease, in particular, an occurrence of a clubroot occurring in a cruciferous plant such as cabbage, or for improving the symptom thereof, and further relates to a method for controlling the tuberculous disease. .

  Conventionally, the method of controlling clubroot occurring in cruciferous plants has mainly been the method of soil disinfection with chemicals and the use of resistant varieties.

  As for drugs, flusulfamide powder (drug name: nevidin powder), dazomet powder (drug name: bathamide fine powder), fluazinam powder (drug name: fronside powder), etc. are applied to the soil and pathogens (dormant spores) are applied. By preventing sterilization or germination of spores, infection of plants is prevented.

  As resistant varieties, cruciferous plants having resistance genes such as kale and feed turnip are used as genetic resources to develop resistant varieties such as cabbage and Chinese cabbage.

  On the other hand, as a technique different from the above-described method, a method of increasing the resistance to disease-causing bacteria by activating a disease-resistance mechanism that a plant potentially has has been attempted. Specifically, for example, from the following findings, it is considered that low molecular weight chitin is an elicitor-like active substance that activates a resistance mechanism.

  That is, the following Non-Patent Document 1 describes that chitin oligosaccharide has an elicitor effect in rice plant cells. Moreover, the following nonpatent literature 2 describes that a chitin degradation product has an elicitor effect on tomato. Furthermore, the following Non-Patent Document 3 describes that chitin oligosaccharide (7-mer or octamer) strongly activates the resistance-related gene of Arabidopsis (Arabidopsis).

  And as a technique which applied the above knowledge to the cruciferous plant, for example, in the following Patent Document 1, low molecular weight chitin having a number average molecular weight of 3,000 to 50,000 obtained by hydrolyzing chitin is effective. The plant disease control agent characterized by containing as a component is indicated, and it is described that it is effective in controlling cabbage root-knot disease.

  In addition, attempts have been made to induce resistance by inoculating microorganisms that inhabit the rhizosphere of the plant body (see Non-Patent Document 4 below). However, it has been pointed out that the degree of establishment and control effect on the root tissue of plants depends on environmental conditions, and as a result, the effect becomes unstable.

In response to such problems, it has been reported that microorganisms having an activity of inducing disease resistance in a host plant are found among microorganisms having high colonization ability and adaptability to the environment. Specifically, in the following non-patent document 5 by the present inventors, microorganisms belonging to the genus Sphingomonas having an effect of suppressing root-knot disease symptoms are isolated from microorganisms that inhabit healthy cabbage leaves. Has been revealed.
JP 2004-323460 A Naoto Shibuya, Journal of the Japanese Pesticide Science Society, 19, p67-71, 1994 G. Felix, M. Regenass, T. Boller. The Plant Journal, 4 (2), 307-316, 1993 Bing Zhang, et al., Molecular Plant-Microbe Interactions 15, 963-970, 2002 Narisawa, K. et al 1998 Plant Pathology, 47, 206-210, 1998 Atsushi Nagasaka, Ikuo Kadota, Nikkatsu Disease Report 71 (3): p285, August 2005

  When using drugs, there is a problem of adversely affecting the agricultural environment, and when using resistant varieties, there is a problem that susceptibility of resistant varieties occurs due to continuous cropping.

  In addition, the above-mentioned control methods using low molecular weight chitin and microorganisms belonging to the genus Sphingomonas were not sufficient in terms of effectiveness compared to conventional control methods using drugs and resistant varieties. .

  Therefore, an object of the present invention is to provide a technology for effectively activating a disease resistance mechanism that a plant potentially has, and is effective in controlling root-knot disease of cruciferous plants such as cabbage, Another object of the present invention is to provide a disease control agent and a disease control method that are highly safe for humans and the human body.

  As a result of diligent research to achieve the above-mentioned object, the present inventors have demonstrated that resistance to root-knot disease of cruciferous plants can be reduced by combining with low molecular weight chitin from microorganisms that inhabit healthy cabbage leaves. The present inventors have found a strain that can be promoted and have completed the present invention.

  That is, one of the present invention is to hydrolyze chitin with at least one microorganism selected from Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900). It is a clubroot disease control agent for cruciferous plants containing the obtained low molecular weight chitin having a number average molecular weight of 3,000 to 50,000 as an active ingredient.

  According to the cruciferous plant root-knot disease controlling agent of the present invention, by applying the microorganism and the low molecular weight chitin in combination to the cruciferous plant, the occurrence of the clubroot disease of the cruciferous plant is suppressed. And can promote healthy root development.

  In another aspect of the present invention, at least one microorganism selected from Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900) is applied to Brassicaceae plants. The cruciferous plant is applied with a low molecular weight chitin having a number average molecular weight of 3,000 to 50,000 obtained by hydrolyzing chitin before, simultaneously with, or after the microbial application step. A method for controlling root-knot disease of cruciferous plants, comprising a chitin application step.

  According to the method of controlling a clubroot disease of a cruciferous plant of the present invention, the microorganism is applied to a cruciferous plant, and the molecular weight reduction is performed before, simultaneously with and / or after the application. By applying chitin to the cruciferous plant, the occurrence of clubroot of the cruciferous plant can be easily suppressed and the development of healthy roots can be promoted.

  In the present invention, although the detailed mechanism of the effect of the combined use of the microorganism and the low molecular weight chitin is not known, the disease resistance-inducing activity of the two kinds of materials is synergistically enhanced and has a remarkable effect. It is considered to be effective.

  The low molecular weight chitin is prepared from chitin derived from shells of crustaceans such as crabs and shrimps, so it can be manufactured at low cost, is highly safe for the human body, and is plant or soil. Even if sprayed on the surface, it is easily decomposed by microorganisms, does not remain for a long time, and does not contaminate the agricultural environment. In addition, since the microorganism is a microorganism that inhabited healthy cabbage leaves, it does not place a burden on the agricultural environment and is used as it is as an active ingredient, so it is inexpensive.

  In a preferred embodiment of the method for controlling root-knot disease according to the present invention, in the microorganism application step and / or the chitin application step, the microorganism and / or the molecular weight reduction is carried out on the soil or culture medium on which the cruciferous plant grows. Chitin is mixed, sprayed or irrigated, and the microorganism and / or the low molecular weight chitin are applied to the cruciferous plant. According to this, application of the active ingredient to the cruciferous plant is easy.

  In another preferred embodiment of the method for controlling root-knot disease according to the present invention, the microorganism and / or the low molecular weight chitin is sprayed on the cruciferous plant in the microorganism application step and / or the chitin application step. The microorganism and / or the low molecular weight chitin are applied to the cruciferous plant by pouring or coating. According to this, since the active ingredient is directly applied to the cruciferous plant, disease resistance can be effectively induced.

  In still another preferred embodiment of the method for controlling root-knot disease according to the present invention, the microorganism and / or the low molecular weight chitin is applied at the time of seedling, planting or planting of the cruciferous plant. According to this, when applying the said active ingredient to the seedling before planting, the disease resistance of a plant can be induced | guided | derived with a small application amount. Moreover, when applying the said active ingredient at the time of fixed planting or after fixed planting, even if it plants in the field contaminated with the pathogenic microbe, approach to a plant body and proliferation can be suppressed.

  In the present invention, the cruciferous plant is preferably a seedling of the cruciferous plant. According to this, the disease resistance of a plant can be induced with a small application amount by applying the active ingredient to the seedlings before planting. Moreover, even if a seedling to which the active ingredient is applied is planted in a field contaminated with pathogenic bacteria, the pathogenic bacteria can be prevented from entering and growing, and the pathogenesis of the plants can be effectively suppressed. Can do.

  In the present invention, the cruciferous plant is preferably a cruciferous plant suffering from clubroot. According to this, since the growth of a new healthy root can be promoted in a plant suffering from clubroot, the growth of the plant can be recovered.

In the root-knot disease control method of the present invention, it is preferable to apply a suspension containing 1 × 10 ⁸ to 1 × 10 ¹² cfu / ml of the microorganism belonging to the genus Sphingomonas.

  Moreover, in the root-knot disease control method of the present invention, it is preferable to apply a suspension containing 0.1 to 100 mg / ml of the low molecular weight chitin.

  The root-knot disease control agent and root-knot disease control method of the present invention include cabbage, Chinese cabbage, turnip, Japanese radish, cauliflower, broccoli, wasabi, Japanese sugar beet, Taisai, Komatsuna, Nozawana, mustard, Takana, Kairan, watercress, kale, etc. It is preferably used for cruciferous plants.

  According to the present invention, Sphingomonas TF1401 strain (Accession No. FERM P-20899) or Sphingomonas TF1402 strain (Accession No. FERM P-20900), which is a microorganism belonging to the genus Sphingomonas, and a small molecule having a specific molecular weight. By applying to a cruciferous plant in combination with a modified chitin, it is possible to strongly induce the potential disease resistance of the plant and suppress the onset of the plant due to the root-knot pathogen. In the present invention, by applying the active ingredient to the seedlings before planting, the disease resistance of the plant can be induced with a small application amount, and the active ingredient is applied at the time of planting or after planting. By giving, even if it plants in the field contaminated with the pathogenic microbe, the approach and proliferation to the plant body of a pathogenic microbe can be suppressed. Furthermore, even in a plant suffering from clubroot, it is possible to promote the development of a new healthy root by applying the above-mentioned active ingredient, so that the growth can be recovered.

  Since the microorganism is a microorganism that inhabited healthy cabbage leaves, it does not place a burden on the agricultural environment and is used as it is as an active ingredient, so it is inexpensive.

  In the present invention, “root-knot disease” means a disease that occurs in cruciferous plants using Plasmodiophora brassicae, which is a type of mold, as a pathogen. Clubroot disease is likely to occur when cruciferous plants are continuously cropped, and is one of the biggest production inhibiting factors of cruciferous plants. A plant suffering from clubroot is enlarged in a bumpy shape, cannot absorb water and nutrients, and its growth is stagnant and it dies. In addition, since the pathogenic bacteria survive in the soil for a long period of time, it is difficult to control them once they occur, and they often spread from the generated fields to the surroundings through movement of the soil or rain accompanying farming, and cultivation of cruciferous plants such as cabbage It is one of the most harmful soil-borne diseases.

  The microorganisms belonging to the genus Sphingomonas used in the present invention were isolated as follows.

  That is, when bacteria are randomly separated from cabbage leaves that are healthy in appearance and separated by using Biomelieu's bacteria identification kit “API20 NE”, they are identified as microorganisms belonging to the genus Sphingomonas. Many bacteria were obtained. The bacterial identification kit “API 20 NE” includes nitrate reduction using potassium nitrate as a substrate, indole production using L-tryptophan as a substrate, acid production from glucose under anaerobic conditions, arginine dihydrase activity, Urease activity, esculin hydrolysis, gelatin liquefaction, β-galactosidase activity, oxidase activity, glucose assimilation, L-arabinose assimilation, D-mannose assimilation, D-mannitol assimilation, N-acetyl-D-glucosamine assimilation, Negative / positive for each test item: maltose assimilation, potassium gluconate assimilation, n-capric acid assimilation, adipic acid assimilation, dl-malic acid assimilation, sodium citrate assimilation, phenyl acetate assimilation Bacterial identification kit for identifying bacterial species level by judging It is.

About 56 strains of bacteria identified as microorganisms belonging to the genus Sphingomonas, about 6 ml of an aqueous suspension prepared to about 10 ⁸ cfu / ml for each microbial cell was irrigated to the original soil of cabbage seedlings. 24 hours later, it was transplanted to a pot filled with contaminated soil of Plasmodiophora brassicae. Thereafter, when clubroot symptoms were observed on the 39th day, enlargement directly under the main stem was reduced in 37 of the 56 strains. Moreover, about nine of the 37 strains, the degree of daytime wilt of the cabbage individual leaves decreased, and the fresh weight of the above-ground part increased compared with the untreated section.

  The above 9 strains having the effect of improving the clubroot symptoms were respectively Sphingomonas TF1401, Sphingomonas TF1402, Sphingomonas TF1403, Sphingomonas TF1404, Sphingomonas TF1405, Sphingomonas TF1406, and Sphingomonas TF1407. They were named Sphingomonas TF1408 strain and Sphingomonas TF1409 strain. Of these 9 strains, Sphingomonas TF1401 strain and Sphingomonas TF1402 strain, which were confirmed to be effective in combination with low molecular weight chitin in the examples described later, were submitted to the National Institute of Advanced Industrial Science and Technology Patent Organism Depositary. Deposited. The accession number of Sphingomonas TF1401 strain is FERM P-20899, and the accession number of Sphingomonas TF1402 strain is FERM P-20900.

  In the present invention, the above-mentioned Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900) can be used as microorganisms belonging to the genus Sphingomonas. Table 1 below shows the characteristics of the bacterial form and the physiological characteristics of the bacteria by the bacterial identification kit “API20 NE”.

  Moreover, as a result of molecular phylogenetic analysis based on the 16S rDNA base sequence, the positions of the molecular phylogenetic trees of Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900) are both Sphingomonas parapaucimobilis. Matched. That is, when the 16S rDNA base sequence of the strain was determined and homology search was performed in the DNA database (DDBJ), the Sphingomonas TF1401 strain (accession number FERM P-20899) was found between the 16S rDNA base sequence of Sphingomonas parapaucimobilis. A homology of 98% and Sphingomonas TF1402 strain (Accession No. FERM P-20900) 99% was observed. In addition, after multiple alignment of various species of microorganisms belonging to the genus Sphingomonas and 16S rDNA base sequences of representative bacterial species, the position of the molecular phylogenetic tree by molecular phylogenetic analysis NJ method was consistent with Sphingomonas parapaucimobilis in both strains .

  Cultivation, storage, bacterial count measurement, cfu value measurement and the like of microorganism strains belonging to the genus Sphingomonas can be performed according to known methods.

In the present invention, a rapeseed prepared by suspending a microorganism belonging to the genus Sphingomonas in an appropriate solvent such as sterilized water so as to contain 1 × 10 ⁸ to 1 × 10 ¹² cfu / ml is used. It is preferable to apply to a family plant.

  The low molecular weight chitin used in the present invention has a number average molecular weight of 3,000 to 50 by partially hydrolyzing chitin prepared from crustacean shells such as crabs and shrimps by conventional methods with an acid or an enzyme. It is a chitin degradation product prepared to have a number average molecular weight of 5,000 to 20,000. The number average molecular weight can be measured according to a known method such as an HPLC method.

  Such a low molecular weight chitin can be prepared by a known method, for example, by a method described in JP-A-2004-323460.

  In the present invention, the dosage form at the time of applying the low molecular weight chitin may be any form such as powder, granule, liquid, etc., but there is no particular limitation, but 0.1-100 mg / ml The suspension prepared by suspending in a suitable solvent such as water is preferably applied to the cruciferous plant. Moreover, other components, such as an excipient | filler and a bulking agent, may be mix | blended with this low molecular weight chitin containing composition.

  In the method for controlling the clubroot disease of the cruciferous plant of the present invention, the method for applying the microorganism and / or the low molecular weight chitin to the cruciferous plant is not particularly limited. For example, the microorganism and / or the low molecule The aforementioned suspension of chitin may be mixed or sprayed on soil or culture medium, but it is preferable to irrigate the roots of plants. It may also be sprayed, injected or applied directly to the plant.

Preferably, the application amount of the microorganism is usually 1 × 10 ⁹ to 1 × 10 ¹³ cfu per 1 m ² (about 6 pieces of 72-well cell tray (30 cm × 60 cm)) in terms of viable count. × and more preferably ^{10 10 ~1} × ¹⁰ 12 cfu. Moreover, plant 1 per individual, is preferably ^{2 × 10 6 ~5 × 10 10} cfu, more preferably ^{2 × 10 7 ~5 × 10 9} cfu. If the application amount of the microorganism is too small, a sufficient control effect cannot be expected, and if it is too large, it is possible to disturb the biological system in the field, which is not preferable. Moreover, the application amount of the low molecular weight chitin is preferably 0.05 to 500 g in terms of low molecular weight chitin, usually per 1 m ² (about 6 pieces of 72-well cell tray (30 cm × 60 cm)), More preferably, it is 0.5-50g. Moreover, it is preferable that it is 0.1-1000 mg per plant, and it is more preferable that it is 1-100 mg. If the application amount of the low molecular weight chitin is too small, a sufficient control effect cannot be expected, and if it is too large, pathogenesis may be promoted.

  The application time and period of the microorganism and / or the low molecular weight chitin are not particularly limited, but in the present invention, it is preferably applied to plant seedlings. Specifically, it is preferably applied to seedlings grown in cell trays or pots before being transplanted to the field. In this case, it is preferable to apply the microorganism and / or the low molecular weight chitin from at least 1 to 2 days before being transplanted to the field. Thereby, the disease resistance of the plant can be strongly induced, and even when the seedling is planted in a field contaminated with the pathogenic fungus, the invasion and proliferation of the pathogenic fungus can be remarkably suppressed, Plant disease can be effectively suppressed.

  Further, the microorganism and / or the low molecular weight chitin can be applied to a plant suffering from clubroot. For example, by irrigating the suspension of the microorganism and / or the low molecular weight chitin several times to the root of a plant suffering from clubroot, a healthy root is newly expressed from above the diseased root. The plant growth can be restored.

  According to the present invention, for example, the microorganism and / or the low molecular weight chitin is applied to seedlings that have been raised such as cabbage, cabbage, turnip, radish, cauliflower, broccoli, etc. Not only can the development be effectively suppressed, but also the plant suffering from clubroot disease is given the microorganism and / or the low molecular weight chitin, so that healthy roots can be expressed from above the diseased root. It can be promoted and the growth of the plant individual can be restored.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, these Examples do not limit the scope of the present invention.

  As the low molecular weight chitin, a low molecular weight chitin-containing composition “low molecular chitin” (manufactured by Yaizu Suisan Chemical Co., Ltd.) was suspended in water and used as a 20 mg / ml aqueous suspension. This low molecular weight chitin-containing composition is a composition containing 20 to 25% by mass of a chitin partial hydrolyzate (average molecular weight 10,000). The composition is shown in Table 2 below. In addition, when applying the said low molecular weight chitin suspension to a plant body, it stirred thoroughly, and applied, after disperse | distributing the suspension content as uniformly as possible.

  In the following test examples, microorganisms belonging to the genus Sphingomonas include Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P) having the above-mentioned effect of improving the clubroot symptoms. -20900), Sphingomonas TF1403, Sphingomonas TF1404, Sphingomonas TF1405, Sphingomonas TF1406, Sphingomonas TF1407, Sphingomonas TF1408, and Sphingomonas TF1409.

Cultivation was carried out on a KingB flat medium, and after culturing, a cell suspension was prepared by suspending in sterilized distilled water to 1 × 10 ⁸ cfu / ml. In addition, when applying the said microbial cell suspension to a plant body, it stirred sufficiently, and applied, after disperse | distributing the suspension content as uniformly as possible.

<Test example>
Contaminated soil was prepared by mixing root-knot dormant spore (Plasmodiophora brassicae) with commercial horticultural soil.

On the other hand, cabbage seeds were sown in a 128-well cell tray packed with seedling culture soil and grown in a greenhouse for about 3 weeks. Ten days before transplanting these seedlings into contaminated soil, about 5 ml of the above-mentioned cell suspension (1 × 10 ⁸ cfu / ml) per cabbage seedling was irrigated to the soil at the root of the seedling. On the day before transplantation, about 4 ml of the low molecular weight chitin suspension (20 mg / ml) per cabbage seedling was irrigated to the soil at the base of the seedling. On the next day, seedlings were planted in the contaminated soil, and the course of disease was observed. In addition, for comparison, the cabbage treated with the low molecular weight chitin suspension alone was irrigated with the root of the seedling. Disease severity was calculated according to I). A non-treated seedling planted in uncontaminated soil was used as a control (sound). The results are shown in FIG.

  From FIG. 1, three strains of Sphingomonas TF1401 (Accession No. FERM P-20899), Sphingomonas TF1402 (Accession No. FERM P-20900), and Sphingomonas TF1405 Strain are pretreated with low molecular weight. It can be seen that post-treatment with modified chitin shows a higher disease-inhibiting effect than when other strains are used or when low molecular weight chitin is treated alone. Among these strains, Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900) had more stable disease-inhibiting effects than Sphingomonas TF1405 strain.

<Example 1>
The cabbage seeds were sown in a 128-well cell tray packed with seedling culture soil and grown in a greenhouse for about two weeks. 6 days prior to implantation of these seedlings contaminated soil, Sphingomonas TF1402 strain by about 5ml per cabbage seedling 1 individuals (accession number FERM P-20900) cell suspension ^{(1 × 10 8 cfu / ml} ), plant It sprayed on the above-ground part of the body and the stock base soil. On the day before transplantation, about 4 ml of the low molecular chitin suspension (20 mg / ml) per cabbage seedling was sprayed on the above-ground part of the plant body and the stock soil. On the next day, seedlings were planted in the contaminated soil, and the course of the disease was observed. On the 7th and 14th day after planting, the low molecular weight chitin suspension is diluted to 1 mg / ml with sterilized distilled water, and is added to the above-ground part of the plant body and the root soil of each cabbage seedling. About 4 ml was sprayed.

<Comparative Example 1>
A test group of Comparative Example 1 was prepared in the same manner as in Example 1 except that the treatment was performed only with the cell suspension of Sphingomonas TF1402.

<Comparative Example 2>
A test group of Comparative Example 2 was prepared in the same manner as in Example 1 except that the treatment was performed only with the low molecular weight chitin suspension. In addition, the low molecular weight chitin suspension after planting was not sprayed.

<Comparative Example 3>
A test group of Comparative Example 3 was prepared in the same manner as in Example 1 except that the treatment with the cell suspension or low molecular weight chitin suspension of Sphingomonas TF1402 strain was not performed.

About each test section of the said Example 1 and Comparative Examples 1-3, the root enlargement rate, the fine root yield grade, and the above-ground part production amount of the 47th day after planting were calculated | required. The root hypertrophy rate was calculated according to the following formula (II), and the fine root yield was calculated according to the following formula (III). A non-treated seedling planted in uncontaminated soil was used as a control (sound). Each result is shown in FIGS.

  As is apparent from FIGS. 2 to 4, in the test section where the cell suspension and the low molecular weight chitin suspension of Sphingomonas TF1402 strain (Accession No. FERM P-20900) were treated, they were treated alone. Compared with the case, it turns out that the enlargement of the root tissue by a clubroot, and the reduction | decrease of the amount of fine roots, and the above-ground raw weight are improved more.

  FIG. 5 shows (a) a photograph of the root of a cabbage individual in the untreated section of Comparative Example 3 and (b) a cell suspension of Sphingomonas TF1402 strain and a low molecular weight chitin in Example 1 above. The photograph of the root part of the cabbage individual in the test section which processed suspension was shown. Also from FIG. 5, healthy root growth is promoted in cabbage individuals suffering from clubroot by treating with a suspension of Sphingomonas TF1402 and a low molecular weight chitin suspension. You can see that

It is a chart which shows the disease severity when planting cabbage seedlings in contaminated soil prepared by mixing root-knot dormant spore (Plasmodiophora brassicae) with commercially available horticultural soil. It is a chart which shows the average value of the root hypertrophy rate of the cabbage individual in each test section. It is a graph which shows the average value of the fine root yield grade of the cabbage individual in each test section. It is a chart which shows the average value of the above-ground production amount of the cabbage individual in each test section. (A) Photograph of root part of cabbage individual in untreated section and (b) Photograph of root part of cabbage individual in test section treated with cell suspension and low molecular weight chitin suspension of Sphingomonas TF1402 strain. .

Claims (11)

  Number average molecular weight obtained by hydrolyzing chitin and at least one microorganism selected from Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900) A root-knot disease control agent for cruciferous plants containing 50,000 low molecular weight chitin as an active ingredient.   2. The cruciferous plant is at least one plant selected from cabbage, Chinese cabbage, turnip, radish, cauliflower, broccoli, wasabi, santosai, Taisai, Komatsuna, Nozawana, mustard, Takana, Kailan, watercress, or kale. A clubroot control agent for cruciferous plants as described in 1.   A microorganism application step of applying at least one microorganism selected from Sphingomonas TF1401 strain (Accession No. FERM P-20899) and Sphingomonas TF1402 strain (Accession No. FERM P-20900) to a cruciferous plant; And a chitin application step of applying to the cruciferous plant a low molecular weight chitin having a number average molecular weight of 3,000 to 50,000 obtained by hydrolyzing chitin at the same time or after the step. A method for controlling clubroot disease of cruciferous plants, characterized by   In the microorganism application step and / or the chitin application step, the microorganism and / or the low molecular weight chitin are mixed in the soil or culture medium on which the cruciferous plant grows, and sprayed or irrigated. 4. The method for controlling a clubroot disease of a cruciferous plant according to claim 3, wherein the low molecular weight chitin is applied to the cruciferous plant.   In the microorganism application step and / or the chitin application step, the microorganism and / or the low molecular weight chitin is sprayed, injected or applied to the cruciferous plant, and the microorganism and / or the low molecular weight is reduced. The method for controlling clubroot disease of cruciferous plants according to claim 3, wherein chitin is applied to the cruciferous plants.   The method for controlling a clubroot disease of a cruciferous plant according to any one of claims 3 to 5, wherein the microorganism and / or the low molecular weight chitin is applied at the time of seedling raising, planting or after planting of the cruciferous plant. .   The method of controlling a clubroot disease of a cruciferous plant according to any one of claims 3 to 5, wherein the cruciferous plant is a seedling of the cruciferous plant.   The method of controlling a clubroot disease of a cruciferous plant according to any one of claims 3 to 5, wherein the cruciferous plant is a cruciferous plant suffering from a clubroot disease. The clubroot control of cruciferous plants according to any one of claims 3 to 8, wherein a suspension containing 1 x 10 ⁸ to 1 x 10 ¹² cfu / ml of the microorganism belonging to the genus Sphingomonas is applied. Method.   The method for controlling clubroot disease of cruciferous plants according to any one of claims 3 to 9, wherein a suspension containing 0.1 to 100 mg / ml of the low molecular weight chitin is applied.   4. The cruciferous plant is at least one plant selected from cabbage, Chinese cabbage, turnip, radish, cauliflower, broccoli, wasabi, santosai, taisai, komatsuna, nozawana, mustard, takana, caylan, watercress, or kale. The method of controlling root-knot disease of cruciferous plants according to any one of 10 to 10.