JPH09154570A - Microorganism having property of preventing replant failure and microbial material using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new actinomyces K-31 strain, belonging to the genus Streptomyces, having functions to suppress the raising of pathogenic fungi for crops in soil and capable of providing a microbial material capable of preventing replant failure by culturing vermiculite and wheat bran therewith and applying the cultured product to soil. SOLUTION: This microorganism is a new actinomyces K-31 strain (FERM P-15204), having functions to suppress the raising of pathogenic fungi for crops in soil and belonging to the genus Streptomyces. The microorganism is capable of producing a microbial material capable of preventing replant failure by culturing together with a carrier such as vermiculite and a culture medium such as wheat bran and application thereof to soil. The microorganism is obtained by embedding chitin as a separation source in a plowland soil, etc., then directly culturing the resultant plowland soil, etc., after the passage of 2 months or mixing chitin therewith, culturing the resultant mixture under conditions for preferentially increasing the microorganism capable of decomposing the chitin, adding the cultured product to sterile water, shaking the mixture for 30min, diluting the shaken mixture, smearing a chitin agar plate culture medium with a part thereof, carrying out the culturing at 28 deg.C in the dark for 1 week and collecting the microorganism of a colony capable of decomposing the chitin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD [0001] The present invention relates to a microorganism capable of reducing the density of crop pathogens in soil and mitigating continuous crop damage, and a microbial material using the same.

[0002]

2. Description of the Related Art Since the introduction of the designated production area system for crops in 1970, continuous crop production has progressed in agricultural lands, which has led to a problem of continuous crop failure, which is a disease caused by soil pathogens. When this method of control is used to kill pathogenic bacteria using pesticides, not only the pathogenic bacteria but also useful microorganisms are sterilized, which disturbs the biological environment in the soil, deteriorates crop growth, or introduces new There is a problem that diseases will occur. On the other hand, it is possible to avoid continuous cropping of the same crop and prevent crop failure, but profitability becomes a problem.

In response to such a problem, there is a method of using a microorganism to reduce soil diseases and continuous crop damage by the action of the microorganism. For example, Japanese Patent Laid-Open No. 03-72825 discloses a method.
A molding medium to which useful agricultural microbes have been added is disclosed, and Japanese Patent Application Laid-Open No. 62-234005 discloses a microbial preparation for agriculture, forestry and fisheries, in which microbes are immobilized on a polymeric substance.

[0004]

However, Japanese Patent Laid-Open No. 03-
The formation medium described in Japanese Patent No. 72825 is to prevent continuous cropping by adding useful microorganisms to the medium and propagating in the medium in plant cultivation using an inorganic molding medium such as rockwool fiber. However, it cannot be directly applied to soil in which various microorganisms live. Further, in the microbial preparation described in JP-A-62-234005, the microorganism used is a known species, and these microorganisms are not sufficient in suppressing soil pathogens and are effective in reducing continuous cropping disorders. Not really.

Therefore, an object of the present invention is to solve the above-mentioned problems and provide a microorganism having a high effect of suppressing soil pathogens that can be applied to general soil, and further use this to provide an agricultural microbial material for reducing continuous crop damage. Is to provide.

[0006]

[Means for Solving the Problems] The present inventors have focused on the phenomenon that the occurrence of disease is suppressed by adding chitin, which is a component of the cell wall of pathogenic bacteria, to disease-producing soil, and have the ability to decompose chitin. It was found that by separating a microorganism that is high and capable of suppressing the growth of pathogenic bacteria and applying it to soil in which the disease has occurred, the bacterial density of the crop pathogenic bacteria in the soil can be reduced and the disease can be suppressed. The present invention has been completed.

That is, the microorganism of the present invention is a novel actinomycete K-31 strain FERM P-15204 belonging to the genus Streptomyces having a function of suppressing the growth of crop pathogens in soil. And actinomycetes belonging to the same species as the above, separated from soil mixed with chitin or plant or animal material, and having a function of suppressing the growth of crop pathogens in soil.

The microbial material containing the microorganism of the present invention is a microbial material obtained by culturing the above-mentioned novel actinomycetes together with a carrier and a culture medium, and is cultivated using vermiculite as a carrier and bran as a culture medium. It is a microbial material obtained by

Furthermore, the present invention is a method for preventing continuous cropping disorders, characterized by applying the above-mentioned novel actinomycetes to soil. By applying the above-mentioned microbial material, it is possible to prevent continuous cropping disorders. It is a feature.

The microorganism used in the present invention is a genus Streptomyces isolated from soil.
actinomycete K-31 strain (accession number: FERM)
P-15204) and actinomycetes having the same properties as those, which produce chitinase, suppress the growth of soil pathogens, and prevent continuous crop failure.

The actinomycete K-31 strain was isolated by the dilution plate method using a chitin medium, and was treated with Streptomyces in the following manner.
It was identified as a new actinomycete belonging to s).

That is, "Experimental method for identifying actinomycetes, No. 1
Edition, Japan Actinomycete Study Group, Japan Actinomycete Study Group Secretariat (1
985) ”,“ Scientific Methods for Scientific Classification of Microorganisms, First Edition, Kazuo Komagata, Academic Publishing Center (1982) ”and“ Bacterial Identification Method Accompanied by New Taxonomy, 1st Edition, Nane Publishing (19)
87) ”, and regarding the search for bacterial species, refer to“ H.
Nonomura, J. Ferment. Technol., 52, 78 (1974) '',
`` Bergey's Manual of Systematic Bacterology, Vol.
4, ST Williams, ME Sharpe, JG Holt, Wiliam
s & Wilkins (1989) "," ISP description reports "
`` EB Shirling, D. Gottlieb, Int. J. Syste
m. Bacteriol., 18, 69 (1968), EB Shirling, D. G
ottlieb, Int. J. System. Bacteriol., 18, 279 (196
8), EB Shirling, D. Gottlieb, Int. J. System. B
acteriol., 19, 391 (1969), EB Shirling, D. Got
tlieb, Int. J. System. Bacteriol., 22, 265 (1972)
The morphological observation, physiological property test and analysis of bacterial cell components were carried out for identification with reference to.

As a result, from the cell wall type, morphology, and quinone system, cell wall type I actinomycetes form basal hyphae and form long spore chains in the spore stalk on aerial hyphae. (Streptomy
It was identified as an actinomycete belonging to s). Next, a species search was carried out with reference to Nonomura's literature, but no description of a completely matching bacterial species was found in the literature. Therefore, when I re-searched focusing only on the color tone and assimilation of the village surface,
Treptomyces viridifacienc
s, Streptomyces recifensi
s, Streptomyces xanthocidi
Since it was considered to be relatively close to the three strains of C. cus, the culture properties were compared with the reference strains of these three strains. as a result,
It was found that the K-31 strain differs from the reference strain in the color tone of the settlement and the like, and is a strain different from these strains. K-
The properties of the 31 strains are shown in Table 1, and the comparison results of the color tone of the K-31 strain and the reference strains of the three strains in each ISP medium are shown in Table 2. A micrograph showing the shape of the spore chain is shown in FIG. 1, and a micrograph showing the surface structure of the spores is shown in FIG.

[0014]

[Table 1]

[0015]

[Table 2]

The reason why the actinomycete of the present invention suppresses the growth of pathogenic bacteria is not fully understood theoretically, but in general, the cell wall composition of the pathogenic bacteria of the crop is found in the soil in which the disease of the crop is developed. It is known that the disease can be suppressed by applying the component chitin or laminarin, which is
By adding these substances, microorganisms that can assimilate and decompose chitin or laminarin selectively grow, and as a result, substances that decompose chitin such as chitinase are released into the soil and lysis of pathogenic bacteria is performed. It is believed that the pathogenic fungus prevents the crop from infecting the crop. That is, the field soil separated from the soil of the present invention, specifically, the field soil is placed in a pot, and 5 g of chitin wrapped in gauze is buried therein to keep the soil in a wet state.
After being left for a month, the actinomycete separated from the chitin in the gauze using a chitin medium has a large production amount of chitinases, assimilates chitin, and has a high ability to decompose,
This is believed to effectively suppress the growth of pathogenic bacteria.

As shown in FIGS. 3 to 6, the inhibitory effect of the K-31 strain on pathogenic bacteria is Streptomyces viridifac which is a conventionally known actinomycete.
iencs and Streptomyces receive
It has a large inhibitory ability as compared with the ability of the known actinomycetes such as Nsis to inhibit pathogenic bacteria.

In order to prevent continuous cropping disorders, the microorganism of the present invention, Streptomyces.
es) actinomycete K-31 strain (accession number: FERM
P-15204) or actinomycetes exhibiting properties similar thereto can be applied to cultivated soil. As the application form, there is a method of irrigating suspension containing actinomycete hyphae and spores, actinomycete culture solution, spore germination solution, etc., or applying a row, and easy handling and stability of effect. It can be carried out by preparing a microbial material containing actinomycetes in consideration of the above and mixing and applying it to cultivated soil.

The microbial material containing actinomycetes is prepared by solidifying actinomycetes as a carrier such as vermiculite and a culture medium such as bran. The carrier that can be used here is used as a growth substrate for actinomycetes, and for example, inorganic ones such as vermiculite and zeolite, and organic ones such as bone meal, egg shell, peat moss and charcoal can be used. The culture medium is used as a source of growth nutrients for actinomycetes, and various types such as bran, rice bran, and fish meal can be used. Among these, the combination of vermiculite and bran is preferable because of the growth of the K-31 strain.

The amount of the carrier and the culture medium to be blended is preferably about 1 to 10 volumes of the carrier with respect to 1 volume of the culture medium. In the case of fusuma and vermiculite, the volume ratio is 1: 1 to 1: 3, particularly preferably 1 volume. Good results are obtained with a mixing ratio of 1: 1.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The actinomycetes used in the present invention can be isolated as follows. That is, directly from upland soil, plant or animal organic material, or
After applying chitin to these and breeding microorganisms,
A sample is collected using these as a separation source and suspended in sterile water to prepare a diluent. Then, a part of the diluted solution was cultivated on a chitin agar plate medium at 28 ° C. in the dark for 1 week, and the colonies generated on the medium were observed, and those having a transparent ring showing dissolution of chitin in the medium were observed. Purely isolated as a chitin-degrading bacterium. Thereafter, the purely isolated strain was (1) having a high ability to decompose chitin in the medium under solid stationary culture and liquid shaking culture conditions using a chitin medium,
(2) Suppress the growth of Fusarium hyphae by facing culture with Fusarium, which is a causal agent of yellow radish radish in malt / yeast extract medium, (3) Proliferation ability under liquid shaking culture conditions of albumin medium The stock was selected based on the high value. The K-31 strain of the present invention, which was separately selected by such a method, was a new actinomycete belonging to the genus Streptomyces, and therefore has the accession number FERM P-15204.
As a deposit.

The actinomycetes that can be used in the present invention can be separated by the same separation method as long as they produce chitinase, laminarinase and the like and suppress the growth of pathogenic bacteria.
Not only the same strain as the K-31 strain but also a strain in which the K-31 strain is slightly mutated or a similar strain isolated by a similar method can be used.

The prevention of continuous cropping can be achieved by applying the above-mentioned K-31 strain in soil in any form, but it is easy to handle, has reproducibility, and shows a stable effect. It is convenient to use a microbial material, and the case of using this will be described.

The microbial material of the present invention utilizes the inhibitory action against pathogenic bacteria possessed by microorganisms of the genus Streptomyces. To prepare such microbial material,
For example, bran and vermiculite are mixed at a predetermined volume ratio, water is added, and the mixture is sterilized by an autoclave, and then the K-31 strain that has been subjected to liquid shaking culture in a chitin medium is transplanted. For example, at 28 ° C. in the dark. Incubate for 40 days with thorough mixing. During this culture, chitin can be added to the medium to promote the secretion of chitinase, or other culture medium such as laminarin can be added to the medium to promote the secretion of laminarinase, and stable culture can be performed.
For example, various additives such as activated carbon and perlite can be added, and a microbial material can also be prepared by using a granulating agent or the like after culturing, if necessary. The bacterial density of the cultivated material can be measured by the dilution plate method using a chitin agar plate medium, and it is generally preferable that the cultivated material has a bacterial density of 10 ⁶ cfu or more per 1 g of the material.

By mixing and applying the thus-prepared microbial material into the soil, it is possible to suppress the growth of pathogenic bacteria in the soil and prevent the continuous cropping disorder. The amount of actinomycetes necessary for suppressing the growth of Fusarium bacterium, etc. is required, but generally 10 to 10 per field are.
When applied at a rate of about 0 kg, continuous crop failure can be effectively prevented.

As described above, Streptomyces
The actinomycete K-31 strain of the genus has an excellent inhibitory action against pathogenic bacteria by lysing the cell wall of coexisting pathogenic bacteria with an enzyme such as chitinase produced and inhibiting the formation of the cell wall. By applying the fungus in the soil, actinomycetes grow in the soil, in the field soil where the disease of the crop is occurring, the fungus density of the crop pathogen in the soil is reduced to suppress the disease, while, In the soil where the disease has not yet occurred, the continuous cropping failure can be prevented by preventing the disease from occurring by preventing an increase in the bacterial density of the crop pathogen.

A more detailed description will be given below with reference to examples.

[0028]

【Example】

Example 1 Separation of Microorganisms: As a separation source, a chitin-degrading microorganism was directly decomposed from field soil, vegetative or animal organic material, etc., which had been stored for 2 months after being embedded, or by mixing chitin therewith. 10 g of soil or the like cultivated under the condition of increasing preferentially is collected, added to 90 ml of sterilized water, and shaken for 30 minutes. To 1 ml of this suspension (10-fold diluted solution), add 9 ml of sterilized water and mix well.
Prepare a 0 ² -fold diluted solution, collect 1 ml of 10 ² -fold diluted solution, dilute and mix with 9 ml of sterilized water to prepare a 10 ³ -fold diluted solution, repeat this operation ⁶ times, and dilute 10 ⁶ -fold diluted solution. Was prepared. Next, add 10 ⁵ , 10 ⁶ times diluted solution to 0.1 m
l was collected, dispensed on a chitin agar plate medium, evenly smeared with a conradi stick, and cultured at 28 ° C. in the dark for 1 week. After completion of the culture, among the colonies generated in the medium, a colony having a transparent ring showing dissolution of chitin in the medium was judged to be a chitin-decomposing bacterium, and pure separation was performed. Then, from the purely isolated strain, (1) solid static culture using chitin medium,
High ability to decompose chitin in the medium under liquid shaking culture conditions. (2) Suppression of growth of Fusarium hyphae by confronting culture with malt / yeast extract medium with Fusarium, which is a pathogen of radish chlorosis.
(3) K-31 strain of the present invention was selected by selecting a strain under the liquid shaking culture condition of an albumin medium, which is a general medium for actinomycetes, based on its high growth ability.

Morphological observation of the obtained K-31 strain,
Physiological property tests and analysis of bacterial cell components were carried out to identify the bacteria. The results are shown in Tables 1 and 2 and FIGS. As a result, the isolated and selected K-31 strain was found to be a novel strain belonging to the genus Streptomyces, although the species could not be determined.

Example 2 Inhibitory test of K-31 strain against pathogenic bacteria: In the same petri dish,
Fusarium oxysporum which is pathogenic fungus (Fusarium oxysporum s)
p. Raphani) and the K-31 strain were cultured at the same time, and a test for examining the inhibitory effect against pathogenic bacteria was conducted.

As the pathogenic bacteria, Czapek-Dox medium was used, and for K-31 strain, liquid shaking culture was continued for 1 week in sucrose and nitrate medium, respectively, to prepare each bacterial cell. Both culture solutions were soaked in a paper with a diameter of 7 mm, placed on a malt / yeast extract agar plate medium, cultured at 28 ° C for 1 month, and the growth state of the mycelium of the pathogenic bacteria was observed to determine the degree of inhibition by the K-31 strain. Examined. As a control, a known Streptomyces of the genus Streptomyces considered to be relatively related strains
s viridiens and Streptomy
The same test was performed for ces recifenis. The results are shown in FIGS. Figures 3-5 show malt
Place a paper impregnated with the culture solution of Fusarium oxysporum in the center of the yeast extract agar plate medium, and to the left and right of the paper, K-31 strain, Streptomyces vi, respectively.
ridiciens and Streptomyces
It shows a growing state when a paper roll impregnated with a culture fluid of Recifenis is placed and simultaneously cultured. Also,
FIG. 6 shows the growth state when only Fusarium bacterium was cultivated by placing a paper impregnated with a culture solution of Fusarium oxysporum in the center of a malt / yeast extract agar plate medium.

Example 3 Preparation of Microbial Material: Buma: vermiculite in a volume ratio of 1: 1 (100 ml + 100 ml) and 1: 3 (5
0 ml + 150 ml) and mixed in a 300 ml Erlenmeyer flask. Each flask has a maximum water content of 60
Distilled water was added so that the concentration became 100%, and the mixture was sterilized by an autoclave. 5 ml of a culture solution of the K-31 strain that had been subjected to liquid shaking culture was transplanted therein and cultured at 28 ° C. in the dark for 40 days.

The bacterial density of the cultivated material was measured by the dilution plate method using a chitin agar plate medium. Table 3 shows the results.

[0034]

[Table 3]

Example 4 Suppression Test of Pathogenic Bacteria in Soil: Japanese radish chlorophyll disease pathogenic spores Spore density was 10 ⁶ cfu / g of soil. (Bacterial density: 2.32 × 10 ⁷ cfu / g of material)
The mixture was thoroughly mixed at a ratio of 5% by weight and filled in a styrene bottle having a volume of 200 ml. Using 10 styrol bottles for each ward, one radish (varieties: T-340 species) was cultivated per bottle, and the radish chlorophyll pathogen density in the soil after 10 days and 20 days was measured using a Komada medium. It was measured by the dilution plate method used. As a control, the same experiment was conducted under the condition that no microbial material was added. Table 4 shows the results.

[0036]

[Table 4]

Example 5 Disease Suppression Test: The microbial material prepared in Example 3 was mixed at a ratio of 1% by weight with the radish chlorosis-contaminated soil (soil name: Hiruzen soil) to which the original fertilizer had been applied in advance, and 400
350ml pots made of polycarbonate are filled with 350g each, and 2 Japanese radish (variety: T-340 strain) are placed in the glass chamber.
After cultivating for 6 days, the disease state was investigated. Cultivation was done with no material applied as a control, 10 pots in each plot, 3 per pot
I went on a regular basis.

In the investigation of the morbidity, a strain in which the hypocotyl was cut and browning was observed in the central part of the shaft was judged as a sick strain, and as a measure of the degree of morbidity, the “morbidity rate” and “morbidity index” were calculated according to the following formulas.
The disease suppressive properties were investigated. Table 5 shows the results.
The "morbidity rate" indicates the ratio of the number of diseased plants to the number of cultivated plants, and the "morbidity index" conforms to the commonly used disease severity, and the strains killed by the disease survive twice. The degree of morbidity is represented by the following equation, assuming that the diseased strain is 1.

[0039]

(Equation 1)

[0040]

[Table 5]

Example 6 Disease control test: 1 of each of the microbial materials prepared in Example 3
The radish was cultivated for 42 days in the same manner as in Example 5 using the soil added with wt% and the soil added with chitin, and the diseased state was observed. Note that chitin was added to soil using a microbial material having a bran: vermiculite mixing ratio of 1: 3, and the amount of chitin added was 0.6 g per pot. Cultivation was carried out in three stands per pot, with the group to which no material was applied as a control. In addition, the K-31 strain and the bacterial density of the pathogenic fungus on the soil after the cultivation were K-
31 strains were measured by a dilution plate method using chitin medium and pathogenic bacteria were measured by Komada medium. The cultivation results are shown in Table 6 and the bacterial density results are shown in Table 7.

[0042]

[Table 6]

[0043]

[Table 7]

Example 7 Suppression test for susceptibility to continuous cropping disorder: Succeeding cropping disorder occurs in various places, but even in soil where the same disease occurs, properties such as physicochemical properties and biological properties differ depending on the location. From this, it is considered that even if the Japanese radish is cultivated under the same environmental conditions, the degree of disease that occurs and the effect of applying the material are different. Therefore, soils in three districts where radish chlorosis was found were tested, and the disease-controlling effect of the K-31 strain cultivated microbial material in soils having different properties was examined.

Three types of soils were examined: Hiruyama area, Okayama prefecture, Kawai village, Iwate prefecture, and Numamiyauchi area, Iwate town, Iwate prefecture. Table 8 shows the properties of the soil used.

[0046]

[Table 8]

These soils were air-dried and passed through a 2 mm sieve to prepare air-dried fine soil. The obtained air-dried fine soil was mixed with 1% by weight of a fertilizer and a microbial material that had been prepared by culturing at a mixing ratio of fusuma: vermiculite of 1: 1 and filled in a polycarbonate pot having a capacity of 400 ml. After breeding (cultivar number: T-340 species) so that 3 pots per pot (cultivation number: 30), it was cultivated in a greenhouse for 32 days (however, Hiruzen is cultivated for 33 days). After the cultivation was completed, the upper part of the root was cut and the diseased state in the first crop was investigated. Then, radish was sown in the same pot again in the same manner, for 33 days for Hiruyama soil, 34 days for Kawai soil, and 5 days for Iwate soil.
It was cultivated in a greenhouse for 4 days, and the diseased state of the second crop was observed. In the observation of the diseased state after the completion of cultivation, the root upper part was cut, and those showing browning in the central axis were classified as diseased strains, and the “morbidity rate” and “morbidity index” shown in Example 5 Using the "mortality rate" defined by the formula, the effect of suppressing susceptibility to continuous cropping disorders was determined.

[0048]

(Equation 2)

In each of the soils, fertilizer only was applied without using a microbial material as a control. In addition, the density of Fusarium bacterium in the soil before and after cultivation was measured by the dilution plate method using Komada medium. The results of disease control and bacterial density before and after cultivation are shown in Tables 9 to 11.

[0050]

[Table 9]

[0051]

[Table 10]

[0052]

[Table 11]

As can be seen from the comparison between FIG. 3 and FIGS. 4 to 6, Fusarium bacteria were placed in the center of the malt / yeast extract agar plate medium, and the K-31 strain was placed on the left and right sides of the medium, and the results showed that It can be seen that the hyphae of Fusarium bacterium slightly extend in the direction of the K-31 strains arranged on the left and right, but strongly suppress the growth of the hyphae themselves (FIG. 3). On the other hand, in the other two species of Streptomyces,
Growth of mycelium of Fusarium is hardly suppressed (Figs. 4 and 5). As is clear from the results of mycelial growth of Fusarium, the inhibitory effect of the K-31 strain of the present invention on the pathogenic bacteria is significantly greater than the inhibitory effect of known Streptomyces bacteria.
Thus, the strain selected from the chitin buried in the soil by the chitin medium has the ability to actively produce enzymes such as chitinase, which is secreted outside the cells and the cell wall of Fusarium, which is a pathogen. By dissolving
It seems to suppress proliferation.

As can be seen from Tables 3 to 7, the bacterial density of the K-31 strain in the microbial material was higher when the ratio of vermiculite was increased. However, when using this microbial material to investigate the morbidity-suppressing effect, rather, the cultivated material containing a mixture of fusuma: vermiculite at a ratio of 1: 1 significantly reduced both the morbidity rate and morbidity index compared to the control group. However, it has an excellent disease control effect. further,
In some cases, the bacterial density of Fusarium is not reduced, although the disease-controlling effect is actually exhibited.

As described above, the disease control effect is not directly influenced by the bacterial density of the K-31 strain in the material before application, and
No strong correlation was found with the density of Fusarium in the soil after the cultivation.

This is because a carrier such as vermiculite is necessary for uniform and active growth of microorganisms, and can increase the bacterial density of strain K-31 in the material. However, since disease control is due to actinomycetes growing in soil and chitinase produced by actinomycetes, a carrier such as vermiculite affects the uniform growth of actinomycetes in soil and creates an effective site. Even if provided, the growth of actinomycetes is strongly influenced by the environment and growth conditions of the soil such as the nature and condition of the soil, and the growth of microorganisms in the soil after applying the microbial material is important. It indicates that there is. Further, from the experimental results, the disease control is affected not only by the density of the pathogenic bacteria themselves but also by the state of existence of both microorganisms in the soil such as the relative abundance ratio with the Fusarium antagonistic bacteria such as the K-31 strain. I understand.

In addition, in a system in which chitin was added to the soil together with the culture material, the growth of Fusarium bacterium caused by chitin also increased the bacterial density, but since the K-31 strain grew more than that, the proportion of Fusarium bacterium was It decreased relatively.

Next, the effects of suppressing susceptibility to continuous cropping disorders will be described with reference to Tables 9 to 11 and 12. Table 12 shows the morbidity-suppressing effect when the continuous radish cropping is performed.
The value obtained by subtracting the morbidity rate of the material group from the morbidity rate of the control group shown in 0 is shown for each soil. According to this, it can be seen that the morbidity rate of the material section is low in each of the soils of Kawai, Iwate, and Hiruzen, and that the continuous crop failure is suppressed.

[0059]

[Table 12]

Table 13 shows the relationship between the growth rate of the Fusarium bacterium at the end of cultivation and the morbidity and morbidity index with respect to the fungal density before cultivation for each soil. According to this, as described above, the disease-controlling effect does not depend only on the growth rate of Fusarium bacterium itself in soil, that is, only on the absolute abundance of Fusarium bacterium in soil, but the Fusarium antagonistic bacteria in soil. It is considered that it is strongly influenced by the relative abundance with the K-31 strain. That is, in order to prevent the continuous cropping disorder, it is important to form a flora in the soil in which useful bacteria such as the Fusarium antagonistic strain K-31 preferentially propagate.

Therefore, useful bacteria which are antagonistic microorganisms settle in the soil and grow to form a flora preferentially propagated,
It seems that it takes some time for the antagonistic action against the pathogenic bacteria to appear. Therefore, adopted in this example, immediately after applying the material to the soil, not the method of applying the material to sow and carry out a cultivation test, after the application of the material, cultivate the soil for a certain period of time, and then sowing such as radish Therefore, the effect of suppressing the continuous cropping disorder will be more remarkable.

[0062]

[Table 13]

[0063]

INDUSTRIAL APPLICABILITY According to the present invention, the novel strain K-31 belonging to the genus Streptomyces is applied to the soil in which the continuous dysfunction of Japanese radish chlorosis is occurring, whereby the density of pathogenic bacteria in the soil is reduced to 1/20. Can be lowered to a degree,
In addition, the incidence of radish chlorosis can be reduced from 93% to 60%, and continuous crop failure can be prevented.

[Brief description of the drawings]

FIG. 1 is a drawing-substituting micrograph showing the shape of spore linkage (×
800).

FIG. 2 is a drawing-substitute photomicrograph showing the surface structure of spores (×
15000).

FIG. 3 is a drawing-substituting photograph showing a state in which Fusarium bacterium is placed in the center of a malt / yeast extract agar plate medium and K-31 strain is placed on the left and right sides of the medium to culture.

FIG. 4: Fusarium bacterium is placed in the center of malt / yeast extract agar plate medium, and Streptomyce is placed on the left and right sides of the bacterium.
A photograph as a substitute for a drawing, showing a state in which s viridiens are arranged and cultured.

FIG. 5: Fusarium bacterium is placed in the center of malt / yeast extract agar plate medium, and Streptomyce is placed on the left and right of it.
A photograph as a substitute for a drawing showing a state in which S. recifenis is arranged and cultured.

FIG. 6 is a drawing-substituting photograph showing a state in which Fusarium is placed in the center of a malt / yeast extract agar plate medium and only Fusarium is cultured.

Claims (6)

[Claims] 1. A bacterium of the genus Streptomyces, which has a function of suppressing the growth of crop pathogens in soil.
s) actinomycete K-31 strain FERM P-1520
4. 2. An actinomycete K-31 strain FERM P-152.
Actinomycetes belonging to the same species as 04, isolated from soil mixed with chitin or from plant or animal materials and having a function of suppressing the growth of crop pathogens in soil. 3. A microbial material obtained by culturing the actinomycete according to claim 1 or 2 together with a carrier and a culture medium. 4. The microbial material according to claim 3, wherein the carrier is vermiculite and the culture medium is bran. 5. A method for preventing continuous crop damage, which comprises applying the actinomycete according to claim 1 or 2 to soil. 6. A method for preventing continuous cropping disorders, which comprises applying the microbial material according to claim 3 or 4 to soil.