JPH104954A - Microorganism of genus pseudomonas capable of colonizing in rhizosphere of tobacco and soil disease injury controlling agent and control using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control damping-off without adversely affecting a plant body by the presence of a specific bacterium excellent in colonizing properties in a tobacco root in the root part, a cultivated land for the tobacco or soil thereof. SOLUTION: This new microorganism belongs to the genus Pseudomonas and has the ability to decompose nicotine and high colonizing properties in a root part of tobacco. Furthermore, the soil disease injury controlling agent is obtained by the presence of the new microorganism, especially a Pseudomonas fluorescens F3OR2 strain (FERM BP-5555), etc., in the root part of the tobacco, a cultivated land or soil thereof. The microorganism is capable of well proliferating and colonizing in a site where the microorganism is hardly liberated to assimilate nicotine and sufficiently colonize in the rhisospherical part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a nicotine-degrading Pseudomonas bacterium having excellent fixation to tobacco roots. The present invention further relates to a method for controlling tobacco damping-off by introducing the present bacteria into tobacco roots or selectively growing the roots to tobacco.

[0002]

2. Description of the Related Art Tobacco wilt or solanaceous plant wilt (hereinafter simply abbreviated as "wilt") caused by infestation of Pseudomonas solanacearum , a kind of phytopathogenic bacteria, are tobacco and tomato. Many crops, such as eggplant, eggplant and pepper, are heavily damaged.

[0003] Damping-off fungi are easy to survive in soil for a long period of time, and once infected with a plant, proliferate rapidly. Therefore, it is extremely difficult to control them. .

[0004] To control the damping-off disease, soil fumigants such as chloropicrin and methyl bromide have been mainly used. However, in recent years, the use of these agents has caused more pollution due to irritating odors, environmental pollution and destruction of the ozone layer, and also kills not only pathogenic bacteria but also useful microorganisms in the soil. There is a need for safe and effective control methods.

[0005] On the other hand, it has been found that a large number of microorganisms exhibiting antagonism to pathogenic bacteria exist in natural soil, and in order to provide a safe and effective control method, these microorganisms are required. Attempts to control damping-off by using microorganisms have been widely made.

For example, a method using Pseudomonas putida (Japanese Journal of Plant Pathology (1990), vol. 56: 404), a method using Pseudomonas fluorescens (R)
evista de Microbiologia (1989) vol 20: 18-26) and a method using a weakly pathogenic Pseudomonas solanacearum bacteriocin-producing strain ( Pseudomonas solanacearum ) (JP-A-1-16579).

However, in general, there is a problem when using antagonistic bacteria for controlling soil diseases. In other words, the antagonistic bacteria are well established in the roots of the plant and need to be active there.However, under a natural environment such as a field, since the rhizosphere environment is different from the greenhouse condition, the antagonistic bacteria are poorly colonized, so that It has been pointed out that the survival and activity of pathogenic bacteria and the occurrence of the accompanying diseases cannot be suppressed, and that the control effect is low or unstable in many cases.

[0008] For example, in the above-mentioned example using Pseudomonas putida or Pseudomonas fluorescens, these antagonistic bacteria show antibacterial activity against the wilt fungus on the medium, and have a disease-suppressing effect in a short-term experiment in a greenhouse. However, in many cases, the control effect was not observed in the contaminated fields, or the control effect was remarkably reduced in the latter stage of cultivation. No antagonistic bacterium that works has been known so far.

Further, in the above-mentioned Japanese Patent Application Laid-Open No. 1-16579, in which a weakly pathogenic Pseudomonas solanacearum bacteriocin-producing bacterium (OM2 strain) was used,
It became clear that temperature conditions of 18 ° C. or higher were necessary for colonization of the root of the OM2 strain. 3 when transplanting tobacco fields
Since this temperature condition cannot be satisfied on a monthly basis, it is recognized that the number of treated bacteria is liable to decrease, and therefore the effect is low or unstable.

In order to solve these problems, it is necessary to inoculate the inoculated bacteria efficiently on the root. Until now, in order to improve the fixation properties, various measures have been taken, such as applying antagonistic bacteria to seeds and seed potatoes, and adding culture bacteria to talc, zeolite, charcoal, etc. Often unstable.

[0011]

From the above, in the control of soil diseases by antagonistic bacteria, it is strongly desired to develop a method for stably colonizing plant roots using antagonistic bacteria having a high root-fixing property. It is rare.

On the other hand, in recent years, genetic analysis of antibacterial substances produced by antagonistic bacteria has been remarkably advanced based on genetic engineering techniques, and attempts have been made to apply this result to disease control. One method is to incorporate an antimicrobial substance-producing gene into a plant, and studies in this area are proceeding. However, in such a method, it is necessary to create a recombinant plant according to the type of plant. Yes, it takes time and effort.

[0013] Therefore, as another use of the genetic engineering technique, a method of incorporating an antimicrobial substance-producing gene into a rhizosphere microorganism and controlling it with an antimicrobial substance produced by a colonized microorganism can be considered. However, the effectiveness of this method depends on the ability of the microorganisms used to colonize the plant roots. Therefore, it is urgently necessary to provide a bacterium with extremely high root colonization to further increase the possibility of controlling a disease by this method.

Accordingly, the present invention provides a novel bacterium having a high ability to colonize tobacco roots. The present invention further provides a control agent and a control method for damping-off using bacteria having a high ability to colonize tobacco roots.

[0015]

Means for Solving the Problems The present inventors proceeded with research from a viewpoint different from the combination with an antagonistic bacterium or a carrier used in conventional research, and found that a bacterium having excellent colonization at the tobacco root was obtained. Was found. In addition, the present inventors have found that by introducing these bacteria into the roots and selectively growing and colonizing them, it is possible to effectively control the damping-off disease, and completed the present invention.

That is, the present inventor has examined the types and densities of microorganisms inhabiting the rhizosphere of tobacco, and found that nicotine-degrading bacteria are present in the rhizosphere of tobacco. Found significantly more than other solanaceous plants, tomatoes. Furthermore, among these nicotine-degrading bacteria, it was clarified that fluorescent Pseudomonas spp. Especially proliferated and colonized well in sites that were hardly released from roots. In this way, specific bacteria that inhabit the soil or plant rhizosphere and are easily isolated from these samples can assimilate nicotine produced in the tobacco root and settle well in the rhizosphere, adversely affecting plants. It was found that it showed an effect of controlling damping-off without giving birth. The nicotine-degrading Pseudomonas bacteria have not been known in the field of disease control or establishment of microorganisms in the rhizosphere, and are provided for the first time by the present invention.

Novel Bacteria with High Fixation to Tobacco Root The bacterium of the present invention belongs to the genus Pseudomonas, has a nicotine-degrading property, and has a high fixation to tobacco root.

The nicotine decomposability of the bacterium of the present invention can be identified by vigorous growth on a medium containing nicotine in an amount of about 0.2%. In addition, 6% in nicotine medium
When sprayed with 0.1N hydrochloric acid containing silicotungstic acid, nicotine in the medium becomes nicotine silicotungstate and a white precipitate is generated. However, the area around the colonies of nicotine-decomposing bacteria becomes a clear zone, which can be easily confirmed (freeze and dried). Research Society Journal (1986) 32: 78-82).

For the establishment of rifampicin in tobacco roots, a rifampicin-resistant mutant strain was prepared and treated in tobacco roots. The roots were collected periodically, and rifampicin was added to King B medium by a serial dilution method. It can be evaluated by counting the colonies that grew on the medium to which about 50 ppm was added.

[0020] The Pseudomonas bacterium of the present invention can be prepared from natural sources such as soil by ordinary techniques in the field of microorganisms, based on the presence or absence of growth on a medium containing nicotine, colonization of tobacco roots, and characteristics of Pseudomonas. All microorganisms that can be isolated and thus isolated are included in the scope of the present invention. Examples of media containing nicotine are described in Example 1 below. Furthermore, those modified by genetic manipulation or other methods so as to impart desirable properties to the isolated microorganisms, for example, antagonism to take-all fungi, are also within the scope of the present invention.

Surprisingly, the bacterium of the present invention, with or without antagonism against take-all in vitro,
By introducing these into tobacco roots and soil at an appropriate time before transplantation or the like, it is possible to effectively control take-all. That is, in Examples 2 to 5 described below, Pseudomonas fluorescens and Pseudomonas putida, which are priority species, are selected from the isolates of Example 1 among the Pseudomonas spp. Were tested on the tobacco root colonization and the disease-suppressing effect on take-all disease among different strains, and it was found that nicotine-degrading bacteria had high colonization and high inhibitory effect in all species. . Examples of preferred nicotine-degrading bacterial strains thus found are Pseudomonas fluorescens (F27R2, F30R2, F89R1) and Pseudomonas putida (PP2, PP3, PP4).

The reason that the relationship between nicotine degradability and colonization exists may be that the bacterium of the present invention remarkably grows at the site where nicotine produced in tobacco root leaks out of the root. . This leak site is composed of a wound or a crack, and on the other hand, is a place where a pathogenic bacterium invades. Therefore, it is considered that the mechanism for controlling the damping-off by the bacterium of the present invention is to prevent the invasion of the pathogen by physical or antibacterial substances. It is also conceivable to induce resistance in plants. However, the present invention is not limited by these theories.

[0023] The control method and control agent present invention the tobacco blight also provides control methods and the control agent of tobacco blight.

[0024] The controlling method of the present invention comprises, as an active ingredient, a microorganism having nicotine decomposability and having a high fixation to tobacco roots, and / or a culture thereof, which is present in the tobacco root, cultivation area or soil thereof, Inhibiting the growth and / or activity of the pathogen of tobacco take-all during almost the entire period from the start of tobacco cultivation to the harvest or at least one stage.

The microorganism used in the method of the present invention is typically the novel bacterium described above. However, besides that, it has a nicotine-degrading property and therefore has a high fixation to tobacco roots, and has a property of preventing the occurrence of soil diseases of tobacco by being present in tobacco roots, cultivation areas or its soil. It seems that various microorganisms exist. Such microorganisms include bacteria, fungi, actinomycetes and yeast. Therefore, it is within the scope of the present invention to select a microorganism having high fixation to tobacco roots from microorganisms having nicotine decomposability and use it in the method of the present invention.

The microorganisms for use in the method of the present invention may be appropriately grown. For example, in the case of the novel bacteria of the present invention,
There is no need to prepare a special culture medium, and it grows well in a medium for general bacteria such as a meat extract medium and King B medium. Culture conditions are performed under aerobic conditions such as shaking culture and aeration culture.The temperature is 20 to 30 ° C., preferably 25 to 30 ° C., the pH is 5 to 8, preferably 6 to 7, and the culture period is 1 to 1. Four days, preferably two to three days, is appropriate. It is also possible to use cells grown on a slant or a plate medium containing agar and grown on the medium.

The "root" of tobacco is a part which is present in soil or hydroponic solution when a plant is cultivated and absorbs water and nutrients. In addition, the introduction of bacteria to be present in the root, cultivation area or its soil is performed by spraying or irrigating the cell culture on or around the tobacco plant, or by immersing the root in the cell culture. It can be done easily. For example, these are introduced into the root at a concentration of 10 ⁵ to 10 ¹⁰ / ml, preferably 10 ⁷ to 10 ⁹ / ml as live bacteria, from 7 days before transplantation to one month after transplantation. When performing immersion treatment as one method of introduction, the immersion time is 30 minutes.
It is about one minute to three hours, preferably about one hour. In the case of introduction into roots by irrigation or irrigation, the appropriate amount is 5 to 20 ml per seedling, and 50 to 200 ml after transplantation. Alternatively, the same effect can be expected by sprinkling the bacterial cells in the soil.

Also, by simultaneously irrigating the solution containing nicotine with the soil around tobacco at the same time as or after a short time after the introduction of the bacteria, useful bacteria can be selectively grown, and a higher colonization and control effect can be expected. it can. Examples of the solution containing nicotine include nicotine sulfate, nicotine and the like.

Further, by introducing an antibacterial substance gene into these bacteria, it is possible to more effectively prevent the invasion of pathogenic bacteria at the site of entry of the pathogenic bacteria. Therefore, the bacterium of the present invention can be used not only for disease control but also as a material for creating antagonistic bacteria for colonizing tobacco roots.

The control agent of the present invention comprises a microorganism (typically the novel bacterium of the present invention) having a nicotine-decomposing ability and a high colonization property on tobacco roots and / or a culture thereof as an active ingredient. It is manufactured as a dry preparation, solid preparation, concentrated suspension preparation, or diluted preparation, which can have a concentration of 10 ⁵ to 10 ¹⁰ / ml, preferably 10 ⁷ to 10 ⁹ / ml as live bacteria. If necessary, bulking agents, stabilizers, some nicotine, nutrients for bacteria, etc. may be added as appropriate. further,
The control agent of the present invention can also be provided as a mixture with a fertilizer.

[0031]

The present invention will be described below with reference to examples.

Example 1 Isolation of Nicotine-Degrading Pseudomonas Bacteria A healthy tobacco root was dug from a tobacco field in Oyama City, Tochigi Prefecture, the root was cut off with scissors, and the attached soil was shaken off. The roots cut to a length of about 1 cm are placed in 10 ml of sterilized water and stirred with a mixer. Then, 0.1 ml of the obtained serial dilution is added to King B medium (proteose peptone N).
o3 20g, KH ₂ PO ₄ 1.5g, MgSO ₄・ 7H ₂ 01.5g, glycerin
10 ml, distilled water 1,000 ml: J. Lab. Clin. Med (1954) v
ol44: 301-307). After culturing at 28 ° C. for 2 to 3 days, colonies emitting fluorescence under ultraviolet irradiation were separated, and stored in a freezer at −80 ° C. Each bacterial strain is a nicotine synthesis medium (KH ₂ PO ₄ 1.0 g, MgSO ₄ 0.5 g)
, Fe ₂ (SO ₄ ) ₃ traces, CaCl ₂ traces, MnSO ₄ traces, Na ₂ MoO ₄
Traces, nicotine 2.2 g, distilled water 1,000 ml, agar 20.0 g were classified into nicotine-degrading and non-degrading based on the presence or absence of growth on the Japanese Society of Soil Fertilizers (1967) 38: 161-166). Furthermore, the isolated strain was inoculated into a nicotine liquid medium obtained by removing agar from the nicotine medium, and after shaking culture at 28 ° C. for 7 days,
The content of nicotine remaining in the medium was examined to confirm the presence or absence of nicotine degradability. Thus, about 100 fluorescent Pseudomonas bacteria having different nicotine degrading properties were obtained.

Example 2: Identification of isolates Among the putative Pseudomonas fluorescens strains isolated in Example 1, three nicotine-degrading strains and three non-degrading strains were randomly selected. I chose. And
The bacteriological properties of each were examined.

[0034]

[Table 1] Table 1 Bacteriological properties Test item F27R2 F30R2 F89R1 F4R1 F64R1 F97R1  Form Bacillus Bacillus Bacillus Bacillus Bacillus Bacillus Gram staining-------Spores------Motility ++ ++ ++ ++ Attitude to oxygen aerobic aerobic aerobic aerobic aerobic aerobic oxidase + + + + + + Catalase + + + + + + + OFOOOOOOOOOO Fluorescent dye + + + + + + + nitrate reduction------Indole formation------Glycosic fermentability---- --Arginine dihydrolase + + + + + + + Urea decomposition------Esculin hydrolysis------Gelatin liquefaction + + +--+ + PNPG------Utilizing glucose + + ++++++ L-arabinose ++++++++ D-mannose ++++ --- + D-mannitol ++++++++ N-acetyl-D-glucosamine ++++++ + Maltose-------Potassium gluconate + + + + + + + n-capric acid + + + + + + + Adipic acid------dl- Malic acid + + + + + + + Sodium citrate + + + + + + + Phenyl acetate---+ +-Production of acid from xylose + + + + + + Utilization of sorbitol------Formation of yellow pigment------Nicotine degrading ++ ++ − − −

The above six strains are based on bacteriological properties.
rgey's Manual of Systematic Bacteriology volume 1
(1984).
It was identified as a bacterial strain belonging to fluorescens. F27R
2. F30R2 and F89R1 strains are new bacterial strains having nicotine degradation, of which F30R2 and F89R1 strains are referred to as FERM BP-5555 and FERM BP-5556, respectively, on May 30, 1996, by Deposited at the Industrial Technology Research Institute.

Example 3 On May 11, 1994, tobacco (variety: Va115) was transplanted into a field contaminated with tobacco blight. Then, three strains of each of the above-mentioned strains in Table 1 were placed in a King B liquid medium at 25 ° C. for 3 times.
After shaking culture for each day, the cells were collected by centrifugation, suspended in sterile water at a concentration of about 10 ⁸ / ml, and irrigated at 100 ml per strain on June 11 with the strain. The test was conducted with 9 strains per plot and repeated twice. After the treatment, the change in the density of the treated bacteria in the rhizosphere was examined, and the disease status was regularly observed. On August 5, the end of the harvest of tobacco cultivation, a final investigation was performed and each strain was treated. The incidence of tobacco was compared. Table 2 shows the results of the test.

[0037]

Table 2 Changes in fluorescent Pseudomonas spp. Treated to the rhizosphere of tobacco and occurrence of damping-off  Test nicotineDensity in rhizosphere / 1 g of dry root Damping-off rate Classification Resolution 0 days later 15 days later 30 days later August 1 August 5 % (%)% (%) F 4R1-7.9 × 10⁷ 4.0 × 10⁶ 2.7 × 10⁶ 55.6 77.8 F64R1-1.5 × 10⁸ 3.8 × 10⁶ 5.1 × 10^Five 22.2 (48.2) 22.2 (63.0) F97R1-3.1 × 10⁷ 3.2 × 10⁶ 1.6 × 10⁶ 66.7 88.9 F27R2 + 2.1 × 10⁸ 6.9 × 10⁶ 3.4 × 10⁶ 44.4 55.6 F30R2 + 2.4 × 10⁷ 6.1 × 10⁶ 2.5 × 10⁶ 0.0 (18.5) 11.1 (29.6)F89R1 + 1.0 × 10 ⁸ 1.7 × 10 ⁷ 4.5 × 10 ⁷ 11.1 22.2  Note: Figures in parentheses indicate the average disease incidence of the three strains.

As shown in Table 2, fluorescent Pseudomonas bacteria having no ability to degrade nicotine were tested.
Both strains tended to have a lower density in the rhizosphere after treatment, and had a density of about 5% or less immediately after treatment on the 30th day after treatment. In addition, the incidence of dead blight was high, and the final survey showed an average incidence of 63.0%. On the other hand, in the case of nicotine-degrading bacteria, the decrease in bacterial density in the rhizosphere was slow, the colonization was high, and the disease incidence was much lower than that of non-degrading bacteria. Among them, the disease incidence of F30R2 was the lowest at 11.1%, and the control effect was excellent. Moreover, F89R1 was excellent in the ability to survive and proliferate in the rhizosphere among the strains tested.

Example 4 Among the strains or stocks isolated in Example 1, strains that are considered to belong to Pseudomonas putida were selected, and nicotine-degrading strains and non-degrading strains were randomly selected from the strains. I chose each stock. And each bacteriological property was examined. The IFO1416 strain is a standard strain of Pseudomonas putida stored by the Fermentation Research Institute.

[0040]

Table 3 Bacteriological properties Test item PP2 PP3 PP4 IFO1416 PP13 PP14  Form Bacillus Bacillus Bacillus Bacillus Bacillus Bacillus Gram staining-------Spores------Motility + + + + + + + Attitude to oxygen aerobic aerobic aerobic aerobic aerobic aerobic oxidase + + + + + + OF OO OO OO OO Fluorescent dye formation +++ ++++ Nitrate reduction------Indole formation------Glucose fermentability------Arginine dihydrolase + + + + + + Urea decomposition------Esculin hydrolysis------Gelatin liquefaction------PNPG-------Utilizing glucose +++ ++++ L-arabinose ++ +----D-mannose + + +----D-mannitol------N-acetyl-D-glucosamine------Maltose---- -Potassium gluconate +++++++++ n-capric acid ++++++++++ Adipic acid------dl-malic acid ++++++Nicotine degrading ++ ++ − − −

The above six strains are based on bacteriological properties.
rgey's Manual of Systematic Bacteriology volume 1
(1984).
It was identified as a bacterial strain belonging to Puccida. PP2, P
P3 and PP4 strains are new bacterial strains with nicotine degradability, of which PP4 strain is FERM BP-
5554 was deposited with the Institute of Biotechnology and Industrial Science and Technology on May 30, 1996.

Example 5 On May 24, 1995, tobacco (variety: BY4) was transplanted into a field contaminated with tobacco blight. Then, each of the three strains shown in Table 3 above was shake-cultured in a King B liquid medium at 25 ° C. for 3 days each, and then collected by centrifugation, and placed in sterilized water.
The suspension was suspended at a concentration of 10 ⁸ / ml, and the suspension was irrigated on June 26 at a rate of 100 ml per strain. The test was performed by repeating 9 times with 9 strains per plot. After the treatment, the onset of the disease was periodically observed. The results are shown in Table 4.

[0043]

[Table 4] Outbreak of take-all disease  Test distinction nicotineDamping-off rate Resolution July 21 July 28 August 4  % (%)% (%)% (%) IFO14164-16.7 22.2 33.3 PP13-0.0 (7.4) 22.2 (22.2) 22.2 (25.9) PP14-5.6 22.2 22.2 PP2 + 0.0 11.1 27.8 PP3 + 0.0 (0.0) 11.1 (7.4) 11.1 (14.8) PP 4 + 0.0 0.0 5.6 Untreated 5.6 16.7 27.8 Note: The figures in parentheses indicate the average incidence of three strains.

As shown in Table 4, in the untreated section,
Affected strains were seen from mid-July, and on August 4, the last survey, the disease rate was 27.8%. In the treated section of non-nicotine-degrading bacteria, the time of initial development differs depending on the strain, but in the final survey, the disease incidence was almost the same as in the untreated section.

On the other hand, in the treatment section of nicotine-degrading bacteria,
In each case, the first onset time tended to be late, and the final incidence was low in many cases. Among them, the PP4 strain had a remarkably low final disease incidence of 5.6% and was excellent in controlling effect.

[0046]

INDUSTRIAL APPLICABILITY In the present invention, in order to control tobacco damping-off by a biological method, attention was paid not only to the antagonism of the damping-off bacterium but also to the root-fixing property of tobacco. As a result, it was found that nicotine-degrading bacteria were well established on the roots of tobacco. Such a bacterium can prevent the growth of the damping-off fungus for a long time until harvesting, and thus can be used directly for controlling the damping-off disease. Furthermore, by imparting such a bacterium with favorable properties such as antagonism against take-all, it is expected that the biological control method can be further improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C12R 1:40)

Claims (10)

[Claims] 1. A novel microorganism belonging to the genus Pseudomonas, having nicotine-decomposability, and having high colonization to tobacco roots. 2. Pseudomonas fluorescens ( Pseu)
domonas fluorescen s ) F30R2 strain (FERM BP-555)
The microorganism according to claim 1, which is 5). 3. Pseudomonas fluorescens ( Pseu)
domonas fluorescen s) F89R1 strain (FERM BP-555
The microorganism according to claim 1, which is 6). 4. Pseudomona
s putida ) is a PP4 strain (FERM BP-5554).
The microorganism according to the above. 5. The microorganism according to claim 1, which has a property of preventing tobacco soil disease from occurring by being present in tobacco root, cultivation area, or its soil. 6. The microorganism according to claim 5, wherein the soil disease is tobacco wilt caused by Pseudomonas solanacearum . 7. A microorganism belonging to the genus Fluorescent Pseudomonas and / or a culture thereof having a property of preventing the occurrence of soil diseases of tobacco by being present in tobacco roots, cultivation areas, or soil thereof as an active ingredient. An agent for controlling plant soil diseases. 8. A microorganism belonging to the genus Fluorescent Pseudomonas and / or a culture thereof having the property of preventing the occurrence of soil diseases of tobacco by being present in tobacco roots, cultivation areas, or its soil. A method for controlling a plant soil disease, which comprises causing the plant to be present in a root, a cultivation place, or its soil. 9. Microorganisms having high nicotine-degrading ability to adhere to tobacco roots and having the property of preventing the occurrence of soil diseases of tobacco by being present in tobacco roots, cultivation areas or their soils. And causing the selected microorganism or its variant and / or a culture thereof to be present in the roots of the tobacco, the cultivation area or the soil thereof, and tobacco standing for almost the entire period from the start of tobacco cultivation to harvest or at least one time. A method for controlling blight of tobacco, comprising suppressing the growth and / or activity of pathogenic fungi of blight. 10. The method according to claim 9, wherein the nicotine-degrading microorganism is a Pseudomonas bacterium.