JPH0482124B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] Tobacco damping-off of tobacco plants is caused by the scientific name Pseudomonas solanacearum (Pseudomonas solanacearum).
solanacearum) is a soil-borne disease caused by infection with bacteria (also known as tobacco damping-off fungus), and is recognized as a disease that is difficult to control. The present invention is based on the scientific name Pseudomonas solanacearum (Pseudomonas solanacearum).
Tobacco damping-off and solanaceous plant bacterial wilt can be treated by immobilizing a living strain of bacteria belonging to the solanacearum) using a polymeric substance and applying the immobilized bacteria thus obtained to the soil. This relates to a method for controlling. [Prior Art] In general, the occurrence of soil diseases is thought to be largely caused by the survival of pathogenic bacteria at high density in the soil due to continuous cultivation of a single crop, and by cultivating the same crop in such a soil environment. Soil disinfection using soil disinfectants such as chloropicrin and methyl bromide is currently widely used as a control method for tobacco damping-off and solanaceous plant bacterial wilt. The drawback is that it indiscriminately sterilizes the beneficial microorganisms that live there, turning the cultivation soil into "dead soil." Furthermore, their use may cause chemical damage and pollution, and may also result in the accumulation of harmful bromine and excessive chlorine in the soil. The present inventors have discovered that the bacteria Sydomonas solanacearum M23R, which has been previously heat sterilized, is an effective control method that replaces the use of soil disease control agents as described above.
The inventors have invented a method for controlling soil diseases of solanaceous plants, which is characterized by applying Pseudomonas solanacearum M23R to the soil (Japanese Patent Publication No. 59-24126). Furthermore, Pseudomonas solanacearum M4S, a bacterial strain belonging to Pseudomonas solanacearum,
We have just filed a patent application for the above-mentioned method for controlling soil diseases of Solanaceae plants, which is characterized by inoculating live M4S (hereinafter abbreviated as M4S) into the roots of Solanaceae plants. No. 186230). In addition, a method for producing an immobilized complex of microorganisms having plant pathogen control activity has recently been disclosed (Japanese Patent Application Laid-open Nos. 180588-1988 and 180589-1989).
There are descriptions of the control effects of cucumber vine crack disease, eggplant bacterial wilt disease, and tomato wilt disease using immobilized plant pathogenic microorganisms. [Problems to be Solved by the Invention] The present invention relates to an improvement in a method for controlling soil diseases such as tobacco damping-off using the above-mentioned live M4S. An object of the present invention is to provide a method for controlling tobacco damping-off and bacterial wilt of solanaceous plants, which exhibits a more excellent control effect than the method described in JP-A-60-186230. The invention method described in JP-A-60-186230 (hereinafter referred to as M4S live bacteria seedling root inoculation treatment method) is as follows:
Before transplanting, the roots of the transplanted seedlings (usually one seedling is planted in the soil divided by pots at the nursery) are immersed in a suspension of M4S bacteria for about 1 hour. This is a method of transplanting to the main field,
Performing such a soaking operation during transplanting has the problem that agricultural work is complicated and requires labor. Furthermore, as time passes after transplantation, the roots elongate and the rhizosphere expands, and the control effect decreases. This is thought to be due to the fact that as time passes, the environment in which the bacteria can survive is less likely to reach the outside of the original pot soil, and the bacteria die or decrease, which poses a problem in the sustainability of the control effect. . [Means for solving the problem] In order to focus on and overcome the above-mentioned shortcomings, we placed a control bacterium in the expanded rhizosphere that accompanies the growth of seedlings after transplanting, and improved the survival environment for the control bacterium. By doing so, we came up with the present invention as a pest control method that maintains the sustainability of the pest control effect. That is, the present invention uses live bacteria Sydomonas solanacearum M4S.
This is a method for controlling tobacco damping-off disease, which is characterized by immobilizing the tobacco using a polymeric substance and applying the thus obtained immobilized product to soil. The method of the present invention will be explained in detail below. The M4S used in the present invention has been deposited with the Institute of Microbial Technology, Agency of Industrial Science and Technology on December 14, 1983 as Microbiological Research Institute Deposit No. 700. This was obtained by mutation of the Pseudomonas solanacearum U-7 strain, which is known as the bacterium that causes tobacco damping-off. It is a well-known strain that has the characteristics of inhibiting the phytotoxicity of solanaceous plants, and is not pathogenic to plants of the Solanaceae family at all. The method for culturing M4S is, for example, a known CPG medium (1 g of casamino acids, 10 g of glucose, 10 g of peptone).
g, 1000 ml of water), and cultured with shaking at 28-30°C for about 48 hours. The culture fluid thus obtained is collected using a centrifuge to obtain wet bacterial cells. The wet bacterial cells are immobilized using a polymeric substance or its monomer. The method for immobilizing bacterial cells is a method known as the comprehensive method ("Enzyme Engineering", edited by Saburo Fukui et al.
p157-202) is sufficient. That is, natural substances such as starch and its derivatives, konjac flour and its purified products, gelatin, alginic acid and its salts, or algae-derived polysaccharide substances such as carrageenan are made into a sol, and the wet bacterial cells are In addition, it may be gelled. Alternatively, monomers such as polyacrylamide or acrylamide-acrylic acid copolymer may be gelled by adding the wet bacterial cells. Furthermore, it is also possible to use a method in which a prepolymer such as polyvinyl alcohol or a photocurable resin is added to the wet microbial cells, gelled, and immobilized. The number of living M4S bacteria contained in the obtained immobilized product must be 1 x 10 ⁵ cells/ml or more, preferably 1 x 10 ⁷ cells/ml or more. By applying the M4S immobilized product thus obtained to soil, it exhibits excellent control effects against tobacco damping-off and solanaceous plant bacterial wilt.
The application method is not particularly limited, but from the day when basal fertilizer is applied to the main field or from the day when ridges are formed to the day of transplanting,
Mix well with the soil and apply about 2 times per ^10m2 . There is no problem in mixing it with compost and other fertilizers. The plants targeted for disease control by the method of this invention are plants of the Solanaceae family, such as tobacco, tomatoes, eggplants, green peppers, and potatoes, and the targeted disease is tobacco damping-off caused by the bacteria Sydomonas solanacearum. and bacterial wilt of solanaceous plants. [Action] The control mechanism of tobacco damping-off and bacterial wilt of solanaceous plants by M4S is that after M4S invades the plant,
It is characterized by its pest control effect. From this point of view, it was thought that no control effect could be exerted except by the conventional M4S live fungus root inoculation treatment method. The method of the present invention involves immobilizing M4S before transplanting seedlings.
M4S is unique in that it mixes into the soil, and live M4S in the soil invades the roots of the transplanted plant and causes the plant's own control response due to the specific action of M4S. The control effect is exerted by secreting anti-pathogen substances. In particular, M4S in the immobilized material mixed in the soil gradually invades the newly elongated roots after transplanting.
The advantage of the method of the present invention is that it exhibits a pesticidal effect. In the conventional M4S live bacteria root inoculation treatment method,
It has been experimentally confirmed that once M4S invades the roots, it migrates to the stems and multiplies, but it does not migrate to newly elongated roots, so the effect of this method lacks sustainability. be. The effects of the method of the present invention are clear in the following examples. Example 1 Casamino acids 0.1%, glucose 1%, peptone 1
M4S was inoculated into a liquid medium containing % of M4S and cultured at 30°C for 42 hours. The culture solution was collected using a centrifuge to obtain wet bacterial cells. A sodium alginate suspension is prepared using 3000 ml of a 3% sodium alginate aqueous solution for 10 g of wet bacterial cells, and this is dropped into a 1.5% calcium chloride aqueous solution.
An immobilized product of M4S was obtained. The obtained immobilized product had approximately 1×10 ⁷ cells/ml.
Contained M4S. Tobacco was grown in a field contaminated with tobacco damping-off disease within the Utsunomiya Experimental Station of Japan Tobacco Co., Ltd. The field is divided into three districts.
(1) M4S viable bacteria immobilized soil treatment area of the present invention, (2)
(3) untreated area; (3) untreated area; (1) The M4S viable bacteria immobilized soil treatment area of the present invention was treated as follows. That is, the immobilized material prepared by the above method was mixed into compost when adding basal fertilizer two weeks before tobacco transplantation, and 10 m ²
It was applied to tobacco fields so that it would be 2 times per day.
Transplantation of tobacco seedlings followed conventional practices. (2) M4S viable fungus seedling root inoculation treatment was carried out according to the treatment method of the previous invention. That is, Example 1
A treatment solution was prepared by suspending the wet bacterial cells obtained in the same manner as in the above method in distilled water. The bacterial concentration in the suspension was ¹⁰⁹ bacteria per ^ml of suspension. Pour the treatment solution prepared in this way into a treatment tank to a depth of 2 cm, and place a vinyl pot (28.5 cm on each side) inside the tank.
Tobacco seedlings planted in the water were soaked for 1 hour. This treatment was performed on the day the tobacco seedlings were transplanted to the main field. (3) The untreated plot served as a control plot, and tobacco seedlings were transplanted according to conventional practices without any treatment. After transplanting the seedlings to the main field, the disease state of tobacco damping-off was investigated. The degree of onset of the disease is determined using the index shown below.
The average morbidity index was determined, and the control rate was calculated from this. Index 0: Healthy 1: One or two lower leaves are withered 3: Half of the leaves are withered 5: All leaves are yellowed and withered 10: Blight control rate (%) = (1 - (average disease index of treated area) / (Average morbidity index of control plot) x 100 The results of the investigation 84 days after transplanting the seedlings are shown in Table 1.

[Table] Example 2 M4S was inoculated into a liquid medium containing 1% yeast extract and 1.5% glucose, and cultured at 30°C for 48 hours. The culture solution was collected using a centrifuge to obtain wet bacterial cells.
A 200 ml cell suspension was prepared using sterile water per 1 g of wet cells. On the other hand, 750 ml of 18.7% acrylamide (containing 96% acrylamide and 4% N,N'-methylenebisacrylamide) aqueous solution, 0.23
%N,N,N',N'-tetramethylethylenediamine aqueous solution (250 ml) and 0.28% ammonium persulfate aqueous solution (500 ml) were each prepared. After mixing these three types of aqueous solutions and the bacterial cell suspension, the mixture solidified when left to stand still. This solidified product was shaped into cubes of 2 to 3 mm using a mesh to obtain an M4S immobilized product. The immobilized product obtained was 1×10 ⁵ cells/ml.
Contained M4S. The occurrence of tomato bacterial wilt was investigated using the immobilized product prepared by the method described above. In other words, soil with immobilized material added at a ratio of 1/50 to Kuroboku soil to which pathogenic tomato bacterial wilt bacteria was added so that the number of bacteria was 1 x ^{103 per} gram of dry soil. They were placed in pots, and on the same day, tomato seedlings 20 days after sowing were transplanted there. As a control, we put the black soil with the tomato bacterial wilt fungus added into the pot.
Tomato seedlings were transplanted in the same manner. On the 45th day after transplanting the seedlings, the onset of tomato bacterial wilt disease was investigated. The degree of disease onset and control rate were determined in the same manner as in Example 1. The results are shown in Table-2.

[Table] Example 3 Casamino acid 0.1%, glucose 1%, peptone 1
M4S was inoculated into a liquid medium containing % of M4S and cultured at 30°C for 40 hours. The culture solution was collected using a centrifuge to obtain wet bacterial cells. A carrageenan suspension is prepared using 3000 ml of a 2.5% carrageenan aqueous solution for 10 g of wet bacterial cells, and this is dropped into a 2% potassium chloride aqueous solution to immobilize M4S using spherical carrageenan with a diameter of 2 to 3 mm. I got a monster. The obtained immobilized product had approximately 1×10 ⁸ cells/ml.
Contained M4S. Tobacco was grown in a field contaminated with tobacco damping-off disease within the Utsunomiya Experimental Station of Japan Tobacco Co., Ltd. The field is divided into three districts.
(1) M4S viable bacteria immobilized soil treatment area of the present invention, (2)
(3) untreated area and (3) untreated area. (1) The M4S viable bacteria immobilized soil treatment area of the present invention was treated as follows. That is, the immobilized material prepared by the above method was mixed with compost when adding basal fertilizer one week before tobacco transplantation, and 10
It was applied to tobacco fields at a rate of 2 per m ² . (2) M4S viable seedling treatment plots were treated in the same manner as described in Example 1. (3) The untreated plot served as a control plot, and tobacco seedlings were transplanted according to conventional practices without any treatment. After transplanting the seedlings to the main field, the disease state of tobacco damping-off was investigated. The degree of disease onset and control rate were determined in the same manner as in Example 1. Table 3 shows the results of the survey 76 days after transplanting the seedlings.

[Table] [Effects of the Invention] As is clear from the examples, the method of the present invention demonstrated the soil disease control effect of treatment with live bacteria of Cydomonas solanacearum and M4S targeting tobacco damping-off and bacterial wilt of solanaceous plants. It has become possible to increase dramatically.

Claims (1)

[Claims] 1 Live bacteria Sydomonas solanacearum
A method for controlling tobacco damping-off and bacterial wilt of solanaceous plants, which comprises immobilizing M4S using a polymeric substance and applying the immobilized product thus obtained to the soil while keeping the bacteria alive. .