JPH0638745B2 - Suppressed strain of rice bacterial blight and method for controlling rice bacterial blight - Google Patents

Description

TECHNICAL FIELD The present invention relates to a bacterial strain that suppresses the occurrence of rice bacterial blight and a method for controlling rice bacterial blight.

[Conventional technology]

Rice bacterial blight is a rice disease first confirmed in Fukuoka prefecture in 1955. This disease is characterized by showing no symptoms on the leaf blades and sheaths of the Honda period and showing symptoms only on the seedlings during the raising period and on the rice buds after the heading of the Honda. Seedling decay occurs mainly in the Hokuriku and Tohoku regions, and rice blight occurs in the southwestern warm regions.
The occurrence of rice blight after heading in the Kyushu area was small until 1974, but the occurrence gradually increased from 1975, and in 1983, the area ratio was 44% in the Kyushu area.
Has caused a great deal of damage and has caused great damage to various parts of Japan.
The number of outbreaks was large after that, and the occurrence rate was over 30% except in 1987 and 1988, which is an important disease of rice in the southwestern warm district.

[Problems to be Solved by the Invention]

So far, many studies have been conducted on the bacterial rot of rice rot, but since no resistant varieties of this disease have been found and there is no drug with a high control effect, there are 2-3 types of control measures for this disease. The current situation is that measures are being taken to reduce the outbreak as much as possible by systematic control using these chemicals. For this reason, in this disease where the introduction of resistant varieties has no prospect, introduction of a chemical pesticide or a biological pesticide having a high control effect is desired.

The present invention has been made for the purpose of solving the above problems.

[Means for Solving the Problems]

In order to solve the above problems, the present invention is (1) discovery of Kyu-A891 strain belonging to the genus Pseudomonas characterized by suppressing the growth of rice blast fungus, (2) culture of Kyu-A891 strain The method is applied by spraying before and after the heading stage of paddy rice in Honda to suppress the occurrence of bacterial bacterial blight of rice.

[Work]

By the above strains and control methods, a bactericidal antibacterial agent that suppresses the growth of bacterial wilt disease on the medium was discovered, and by spraying the bactericidal antibacterial agent before and after the heading period in Honda, the occurrence of rice bacterial bacterial disease was greatly suppressed. can do.

〔Example〕

Hereinafter, the present invention will be described with reference to the examples (test examples) of the present invention.

About 900 strains of bacteria and filamentous fungi isolated from rice and weeds were tested, and the presence or absence of inhibition circle formation was assayed on YPDA plate medium. As a result, 12 strains of bacteria showed formation of inhibition circles against bacterial wilt disease bacteria. It was In the filamentous fungus, no strain forming an inhibition circle was found. These 12 strains were spray-inoculated with the isolates once on the day before or after the day of inoculation of the pathogenic bacteria using pot-grown rice, and the disease-causing rate was investigated and the control effect was tested. . As a result, one strain (Kyu
-A891) showed a relatively high control effect. Antagonistic bacterium K
It was observed that the higher the treatment concentration of the yu-A891 strain, the higher the control effect (see Fig. 1). In addition, although the difference due to treatment time was not clear in this pot test, a relatively high control effect was observed even with the treatment the day after inoculation of pathogenic bacteria, which had a high incidence of rice germ, suggesting the possibility of controlling this disease by using antagonistic microorganisms. Was done.

[Test Example 1] Pot test: Relationship between inoculum concentration of antagonistic bacteria and pathogenicity of bacterial wilt disease (1) Test method Discovered antagonistic bacterial strain Kyu-A891 and rice bacterial wilt disease 982-
34-2 strain was tested. Antagonist suspension (10 ⁴ to 10 ⁸ cfu / m
The relationship between the onset of the bacterial rot and the inoculation concentration of antagonistic bacteria was investigated by the method of pre-inoculating l) with the pathogenic bacteria the day before and the method of the day after the pathogenic bacteria inoculation.

(2) Test results (pre-inoculation with antagonistic bacteria) Looking at the inoculation concentration of pathogenic bacteria of 10 ⁶ cfu / ml, in the inoculation group of pathogenic bacteria alone, the incidence of rice was 35.7%, whereas the inoculation concentration of antagonistic bacteria was 10%. ⁸ cfu / ml), no illness was seen at all, and 1
0 ⁶ to 10 ⁷ cfu / ml) even in the plot, the incidence of rice fever is 0.3 to 4.0%.
And the disease was significantly suppressed. Inoculation concentration of antagonistic bacteria 10 ⁵ to 10 ⁴ cfu /
(ml) group, the disease incidence was as low as 9.9 to 14.9%, and the disease suppressive effect of 58.3 to 72.3% was recognized as compared with the group inoculated with only pathogenic bacteria. 11.0% of the pathogenic bacteria were inoculated in the inoculation concentration of the pathogenic bacteria (10 ⁵ cfu / ml), whereas no disease was observed in the inoculation concentration of the antagonistic bacteria (10 ⁶ to 10 ⁹ cfu / ml). Is not observed, and the disease rate is 4.0 to ^{5 even} in the 10 ⁴ to 10 ⁵ cfu / ml group.
7% and 48-63.6% disease suppressive effects were observed (1a
See table).

(Post-antagonist inoculation) Looking at the inoculation concentration of pathogenic bacteria of 10 ⁶ cfu / ml, the control rice inoculation concentration was 94.1%, whereas the inoculation concentration of antagonistic bacteria was 104.1%. ^{In the 9} to 10 ⁶ cfu / ml) plot, the incidence rate was 56.0 to 59.3%, which was 37.0% lower than in the control plot.
It was confirmed that the disease was suppressed by -40.5%. Looking at the pathogenic bacterium inoculation concentration of 10 ⁵ cfu / ml), in the control group, the pathogenic bacterium-only inoculation group had a morbidity rate of 62.4%, whereas in the antagonistic inoculation concentration of 10 ⁹ cfu / ml). It was confirmed that the disease onset was significantly suppressed to 9.9%. In addition, even if the inoculation concentration of antagonistic bacteria is 10 ⁷ to 10 ⁸ cfu / ml), the incidence of disease is 34.5 to 39.9%.
The rate was as low as 36.1 to 44.7% compared to the control group, but in the 10 ⁵ to 10 ⁶ cfu / ml) group, the incidence rate was 51.8 to 58.6%.
There were many cases of illness, and a decrease in illness control was seen.

From the above, in particular, a remarkable disease suppressive effect was observed in the pre-inoculation section of the antagonistic bacteria, and the inhibitory effect was high even at a low antagonistic bacterial concentration of 10 ⁴ to 10 ⁵ cfu / ml, and practical application could be expected. 1b
See table).

[Test Example 2] Field test: Controlling effect of bacterial bacterial wilt disease by inoculation of antagonistic bacteria before and after heading period (1) Test method Test 1: Trial of variety Golden Hare, machine transplantation in late June, then conventional cultivation did. 10 days before heading or August 24
It was a day. PS before heading lo or after sunset the day after heading
Pathogenic bacteria cultured at 28 ° C for 48 hours in culture medium 982-34-2
100 / 10a of a bacterial suspension of the strain (approximately 10 ⁷ cfu / ml) was spray inoculated with a shoulder sprayer. Bacterial suspension of antagonist Kyu-A891 strain cultured in PS medium at 28 ° C for 48 hours (approximately 10 ⁷ cfu / m
l) was spray-inoculated with 100 / 10a the day before the heading period and 2 days after the heading period.

Test 2: The variety Reihou was supplied, and the plant was mechanically transplanted in late June, and then cultivated conventionally. The heading period was September 7. 10 days before heading or at heading, a pathogenic bacterial suspension prepared in the same manner as in (Test 1) was spray-inoculated. In addition, a suspension (about 10 ⁷ cfu / ml) of an antagonistic bacterium (Kyu-A891 strain) was spray-inoculated on the day before the heading date and the day after the heading date.

(2) Test results Test 1: Sections inoculated with pathogenic bacteria 10 days before heading (No. 4,
Looking at the effect of inoculation with antagonistic bacteria in 5), the disease incidence in the single inoculation area of the pathogenic bacteria was 16.1% 3 weeks after the heading period, whereas
On the day before the heading date, the disease incidence in the antagonist inoculation section was as low as 5.6% even 3 weeks after the heading date, and the onset was largely suppressed by the antagonistic bacteria. Next, looking at the groups inoculated with pathogenic bacteria the day after heading (No. 1, 2, 3), the disease incidence in the single group inoculated with pathogenic bacteria was 38.3% 3 hours after heading, but In the inoculation zone (No. 1) the day before the heading date of the fungus, 27.5 weeks after the heading date, 27.5
%, 2 weeks after the heading period in the inoculation zone (No. 2) the day after the heading period
It was considerably reduced to 4.4% (see Table 2a).

Test 2: Area inoculated with pathogenic bacteria 10 days before heading (No. 4,
Looking at the effect of inoculation with antagonistic bacteria in 5), while the disease incidence in the inoculation area of the pathogenic bacteria alone was 20.5% after 3 weeks of heading,
11.2% after 3 weeks of heading time in the inoculation area on the day before heading time of antagonistic bacteria
, And the illness was considerably suppressed. Looking at the group inoculated with pathogenic bacteria at the heading stage (No.1,2,3), the disease incidence in the group only inoculated with pathogenic bacteria was 26.0% 3 weeks after the heading period, whereas the heading of the antagonistic bacteria Heading period 3 in the inoculation zone (No. 1) on the previous day
14.0% after a week, inoculation section of the antagonistic bacteria on the next day after heading (No. 2)
It became 13.7% 3 weeks after the heading period, and it was revealed that the onset of the antagonistic bacteria was suppressed by the antagonistic bacteria both on the day before and on the next day of the heading (see Table 2b).

〔The invention's effect〕

As described above, the Kyu-A891 strain according to the present invention and the method for controlling rice bacterial blight disease using this strain have the following effects.

By using the antagonistic strain Kyu-A891 strain that shows an antagonistic effect against the bacterial blight of rice blast, it is expected that the control effect is higher than the registered pesticides used so far.

By spraying before and after the heading stage, we discovered an antagonist that has a high control effect against bacterial wilt disease.Therefore, there is no resistant variety and it is possible that biological control is effective against bacterial wilt disease without specific registered pesticides. Found.

[Brief description of drawings]

FIG. 1 is a graph showing the control effect of a bacterial bacterium for controlling the bacterial blight of rice.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Saburo Fukamachi 1-13-5 Satsumoto, Kanoya, Kagoshima Prefecture (72) Inventor Shoichi Izumi 3-24-10 Nishiryo, Kagoshima City, Kagoshima Prefecture (72) Inventor Hiroaki Torigoe 27-13 Shinseimachi, Kanoya, Kagoshima 135 Mutual Aid Housing

Claims (2)

[Claims] 1. A Kyu-A891 strain belonging to the genus Pseudomonas, which suppresses the growth of rice bacterial blight. 2. A rice bactericidal disease, characterized in that the culturing method of Kyu-A891 strain is applied by spraying before and after the heading stage of paddy rice in Honda to suppress the occurrence of rice bacterial blast disease. Control method.