• Korean Journal of Agricultural Science
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• v.12 no.2
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• pp.242-252
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• 1985

In order to get information on the ecology of rice false smut, germination ability and pathogenicity of sclerotia and chlamydospores of the pathogen, environmental conditions affecting the disease outbreak and varietal resistance have been investigated. 1. The degree of outbreak of rice false smut was higher in the upland rice in comparison with the paddy field rice in respect to the number of affected grains per ear, the size and weight of smut balls formed on affected grains as well as the ratio of sclerotial formation produced on smut balls. 2. Germination percentage and days required for germination of overwintered sclerotia placed on the soil surface in July were 81% and 19 days, respectively, while those of overwintered sclerotia treated in May were 60-70% and 41 days. Sclerotia placed on the soil surface or under 1 cm depth of the soil surface and incubated at $25-30^{\circ}C$ were germinated well, whereas those placed under 3 cm or 5 cm depth of the soil surface were not germinated at all. Germinability and stroma productivity of sclerotia were reduced when the sclerotia were cutted into small pieces. 3. The average number of stroma formed on a sclerotium was six and that of perithecia formed in a stroma was about 50 to 140. 4. Percentage of germination of chlamydospores on the yellow balls was very high and was decreased as the color of the balls being darken with maturation. 5. Panicle of rice plants were successfully infected by injection inoculation with suspention of ascospores and chlamydospores of the pathogen to the sheaths at the booting stages, while seeding infection by spraying with suspensions of chlamydospores was unsuccessful. 6. More number of infected grains was distributed on basal parts of an affected ear than that of infected ones distributed upper parts of the ear, when the affected ear was divided into five parts from its basal portion to the apical of the ear. 7. The occurrence of the disease was more severe in the late maturing varieties of rice in comparison with the early maturing varieties. 8. When the level of nitrogen applied was increased, the incidence of disease increased, and the infection percentage of the disease was increased as the transplanting date was delayed. 9. The weight of panicles and 1000 kernels and the ratio of ripenness were reduced, and the contamination degree of grains with chlamydospores were increased as the number of smut balls per panicle were increased.

• The Korean Journal of Pesticide Science
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• v.4 no.3
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• pp.68-74
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• 2000

Penicillium oxalicum (PENOX) has shown the potential as a biocontrol agent(5CA) for control of a weed, clover(Trifolium repens L.) in grass plots. The bioherbicidal activity may be due to germinative and growth capacities and substrate availability of the agent over a range of environmental factors. The influences of different water activities($0.94{\sim}0.995\;a_w$) and temperatures($18{\sim}30^{\circ}C$) on mycelial growth, conidial germination, sporulation oil 2% MEA(malt extract agar) adjusted to different water activities with glycerol, and carbon source utilization using BIOLOG GN MicroPlate were determined in vitro. Decreases in $a_w$ on MEA caused a reduction in mycelial growth and conidial germination depending on temperature. The mycelial growth of PENOX was greatest at $30^{\circ}C/0.995\;a_w$. At some lowered water activity($0.97\;a_w$), the growth was similar between 25 and $30^{\circ}C$, and considerably decreased at lowered temperature($20^{\circ}C$). The germination rate was also greatest at $30^{\circ}C/0.995\;a_w$. Lag phase times for PENOX at $18^{\circ}C$ on MEA were >6hrs at tile whole $a_w$ level tested, and at 18 and $25^{\circ}C$ they were >18hrs and >12hrs at $0.94\;a_w$, respectively. However, its sporulation was some better at $0.97\;a_w$ than $0.995\;a_w$ or $0.94\;a_w$, and better at $20^{\circ}C$ than $30^{\circ}C$. In contrast, the number of carbon sources(niche size) utilized by PENOX varied with $a_w$ and temperature. Under some water stress condition($0.95\;a_w$), the agent utilized smaller number of carbon sources than $0.995\;a_w$ depending on temperature. The niche size at 0.995 and $0.95\;a_w$ were highest at $25^{\circ}C$, and showed 86 and 65, respectively. At $30^{\circ}C$, the niche size at 0.995 and $0.95\;a_w$ showed 84 and 50, respectively. There was no carbon source utilized by PENOX at $0.90\;a_w$ regardless of temperature. These information of tile fungal ecophysiology will be useful for the effective development of BCA.

• Korean journal of applied entomology
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• v.26 no.4 s.73
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• pp.229-237
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• 1987

In order to study the biological control of soil-borne disease of sesame, antagonistic isolates of Trichoderma , Bacillus sand streptomyces to Fusarium oxysporum and Rhizoctonia solani were isolated from the rhizosphere soils of sesame plants and some other habitats. Out of the isolates of microorganisms collected a strain of Trichoderma viride was selected as a biological control agent for the study and its effect on the control of damping-off and the seedling growth of sesame was investigated. The results obtained are as follows: 26 percents of Bacillus spp. isolated from the rhizosphere soil of sesame plants showed antagonism to two pathogenic fungi. Important species were B. Subtilis and B. polymyxa. Streptomyces species isolated from the rhizosphere soils of sesame lysed the cell wall of hyphae and conidia of F. oxysporum and reduced conspicuously the formation of macroconidia and chlamydospores of the fungus. 84 percents of Trichoderma spp. isolated from the rhizosphere soil of sesame plants were antagonistic to F. oxysporum and 60 percents of the isolates were antagonistic to both F. oxysporum and R. solani. Trichoderma viride TV-192 selected from antagonistic isolates of Trichoderma spp. was highly antagonistic to F. oxysporum and soil treatment with the isolate reduced notably damping-off of sesame. T. viride TV-192 showed better growth in crushed rice straw, barley straw and sawdust media than F. oxysporum. Sawdust was selective for the growth of T. viride. Supplementation of wheat bran and mixtures of wheat bran and sawdust inoculated with T. viride TV-192 in the soil reduced remarkably damping-off of sesame by F. oxysporum but high density of the fungus TV-192 caused the inhibition of seed germination and seedling growth of sesame. Inhibitory effects of Trichoderma species on seed germination and seedling growth of sesame were different according to the isolates of the fungus. Normal sesame seedlings on the bed treated with the fungus showed better growth than not treated seedlings.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.1
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• pp.1-8
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• 2017

We investigated the effect of silicate coating of rice seeds on bakanae disease incidence and the quality of seedlings raised in seedling boxes and transplanted into pots. The silicate-coated rice seed (SCS) was prepared as follows. Naturally infested rice seeds not previously subjected to any fungicidal treatment were dressed with a mixture of 25% silicic acid at pH 11 and 300-mesh zeolite powder at a ratio of 50 g dry seed - 9 mL silicic acid - 25 g zeolite powder. The following nursery conditions were provided : Early sowing, dense seeding in a glass house with mulching overnight and no artificial heating, which were the ideal conditions for determining the effect on the seed. The nursery plants were evaluated for Gibberella. fujikuroi infection or to determine the recovery to normal growth of infected nursery plants in the Wagner pot. Seedlings emerged 2-3 days earlier for the SCS than they did for the non-SCS control, while damping-off and bakanae disease incidence were remarkably reduced. Specifically, bakanae disease incidence in the SCS was limited to only 7.8% for 80 days after sowing, as compared to 91.6% of the non-SCS control. For the 45-days-old SCS nursery seedlings, the fresh weight was increased by 11% and was two times heavier, with only mild damage compared to that observed for non-SCS. Even after transplanting, SCS treatment contributed to a lower incidence of further infections and possibly to recovery of the seedlings to normal growth as compared to that observed in symptomatic plants in the pot. The active pathogenic macro-conidia and micro-conidia were considerably lower in the soil, root, and seedling sheath base of the SCS. In particular, the underdeveloped macro-conidia with straight oblong shape without intact septum were isolated in the SCS ; this phenotype is likely to be at a comparative etiological disadvantage when compared to that of typical active macro-conidia, which are slightly sickle-shaped with 3-7 intact septa. A active intact conidia with high inoculum potential were rarely observed in the tissue of the seedlings treated only in the SCS. We propose that promising result was likely achieved via inhibition of the development of intact pathogenic conidia, in concert with the aerobic, acidic conditions induced by the physiochemical characteristics associated with the air porosity of zeolite, alkalinity of silicate and the seed husk as a carbon source. In addition, the resistance of the healthy plants to pathogenic conidia was also important factor.

• Research in Plant Disease
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• v.15 no.2
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• pp.94-100
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• 2009

These experiments were conducted to improve the effect of seed disinfection on rice seed severely infected Bakanae disease by seed soaking into mixed solution of prochloraz EC and fludioxonil FS. We investigated the effects of various concentrations of two fungicides mixed solution on spore germination and mycelial growth of Fusarium fujikuroi. Mycelial growth was inhibited 100% at $10{\mu}g$/ml of prochloraz and 33.3% at $80{\mu}g$/ml of fludioxonil. Spore germination was inhibited 81.4% at $40{\mu}g$/ml of prochloraz. Interestingly, mixed solution of $5{\mu}g$/ml or $10{\mu}g$/ml of each fungicide inhibitied 100% of mycelial growoth and 99.2% of spore germination, respectively. Severely infected rice seeds soaked into mixed solution composed of $125{\mu}l$/ml of prochloraz and $50{\mu}l$/ml of fludioxonil showed 2.1% of disease symptoms compared to 20.4% of prochloraz $125{\mu}l$/ml, but higher concentrations of prochloraz decreased the seedling stand rate. When the seed soaking time was longer and temperature was higher, control effect on Bakanae disease was improved, but seedling stand was lower about 80% over $35^{\circ}C$.

• Microbiology and Biotechnology Letters
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• v.27 no.6
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• pp.427-432
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• 1999

For the development of a multifunctional biocontrol agent, the siderophore-producing strain GL7 was isolated from a rhizosphere on chrome azurol S agar. The GL7 was identified as a strain of Pseudomonas fluorescents on the basis of their reactions to standard physicochemcial tests from Bergey's manual, API diagnostic test, and fatty acid analysis. P. fluorescents GL7 considerably inhibited spore germination and hyphal growth of phytopathogenic fungus Funsarium solani in a dual culture. In pot trials of bean with P. fluorescens GL7, the disease incidence was significantly reduced down to 5% from 70% of incidence in the untreated control. P. fluorescens GL7 also enhanced plant growth to nearly 1.5 times than that of the untreated control, promoting elongation and development of the roots. These results suggest that the plant growth-promoting P. fluorescens GL7 can play an important role in the biological control of soil-borne plant disease in a rhizosphere.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.283-289
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• 2009

Isolation frequency of resistant isolates of Phytophthora capsici to metalaxyl was reported to be 38.9% through the resistance monitoring for metalaxyl in P. capsici causing pepper Phytophthora blight. Metalaxyl was very effective to mycelium growth, while not to zoosporangium germination and zoospore release. $EC_{50}$ values of metalaxyl in the inhibition of mycelium growth were 0.204, 0.151, 0.379, and $0.215\;{\mu}g\;mL^{-1}$ against each isolate sensitive to the fungicide as P. capsici 06-119, 06-143, P08-7, and P08-31, respectively, whilst those were 5.242, 5.724, 6.621, and $5.377\;{\mu}g\;mL^{-1}$ in P. capsici 06-125, 06-155, P08-50, and P08-60. For the field fitness, several factors, which were mycelium growth, zoosporangium germination, zoospore release, virulence to pepper plants, and the zoosporangium and the oospore production, were investigated with 4 sensitive isolates and 4 resistant isolates. Between 2 groups differentiated by the sensitivity of metalaxyl, there was no significance in mycelium growth, zoosporangium germination, zoospore release, and virulence to pepper plants. However, the zoosporangium and the oospore production in each resistant isolate, which were related to survival of P. capsici in fields, were superior to those of sensitive isolates. Based on results of this study, it was suggested that the increase of the percentage of resistant isolates to metalaxyl resulted from the high capacities of the zoosporangium and the oospore production.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.5
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• pp.666-670
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• 2008

Lovastatin (Mevinolin, Monacolin K) is a well-known drug for the therapy of hypercholesterolemia. It is an important fungal secondary metabolite as it inhibits 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase, EC 1.1.1.34) which catalyzes a major rate-limiting step in the biosynthesis of cholesterol. Both soybeans and black soybeans with Aspergillus terreus ATCC 20542 mutant were used as the seed culture for the mass production of lovastatin. The production of lovastatin in soybean seed culture of Asp. terreus was twofold compared to that of black soybean seed culture. The effect of two different vessels (petri dish and Erlenmeyer flask) on lovastatin production was also studied. The production of lovastatin on petri dish was tenfold to that of Erlenmeyer flask. Furthermore, the most lovastatin production on rice bran was achieved when the soybean seed culture was treated by heat shock at $30^{\circ}C$ for 1 hour, representing 82% of HMG-CoA reductase inhibition in the koji extract. We estimated that the heat treated soybean seed culture could be a new method for the mass production of lovastatin.

• Research in Plant Disease
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• v.13 no.2
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• pp.110-114
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• 2007

Anthracnose fungus was most pathogenic on soybean sprout, of the fungi and bacteria isolated from rotten sprout on market. Bacterial strains associated were not virulent. Dry heat (DHT) applied even as high as $65^{\circ}C$ for 30min. was not effective enough to eliminate the artificially inoculated Colletotrichum gloeosporioides propagules from seedllots. Hot water immersion treatment (HWT), at elevated temperature of $55^{\circ}C$ for 20 min, did eliminate the pathogen but reduced seed germinating and retarded sprout growth: Seed germination was practically acceptable when the seedlots were exposed to at $55^{\circ}C$ for 5 min, but about 20% anthracnose propagules survived. Accordingly, we have optimized the HWT scheme for 5 min at $60^{\circ}C$. This scheme was validated, at small to large scale production system, that surely rule out the possible carry over of the bacterial contaminant from seedlots. This result should improve the shelf-life of soybean sprout on the market.

• Journal of Aquaculture
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• v.20 no.1
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• pp.7-13
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• 2007

The seed production of Ecklonia stolonifera Okamura was studied under laboratory conditions through the embryonic sporophyte stage and the field cultivation was conducted in eastern coast of Korea. The germination of zoospores occurred within 3 days and the growth of gametophytes was most rapid at $25^{\circ}C$ and $20\;{\mu}mol{\cdot}m^{-2}s^{-1}$. Sporophyte growth was highest at $20^{\circ}C$ and $20\;{\mu}mol{\cdot}m^{-2}s^{-1}$ and lowest at $25^{\circ}C$ and $80\;{\mu}mol{\cdot}m^{-2}s^{-1}$. In the nursery culture of E. stolonifera lasting for 2 weeks in January, the initial blade length of E. stolonifera (about $500\;{\mu}m$) grew to $526.3{\pm}176.0\;{\mu}m$ at water temperature of $12.05^{\circ}C$. The blade length and width reached their maxima in July, after which the ends of blade and stem began to degrade with the increase in water temperature. The degraded end of the blade started to regenerate in October, when water temperature began to decline. This species can be considered a potential candidate for aquaculture, increasing in the availability of raw material and aiding in recovery of seaweed bed.