• Korean Journal of Microbiology
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• v.22 no.3
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• pp.157-165
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• 1984

Seasonal and spatial variations in propagule numbers of Trichoderma species were investigated every other month for one year in deciduous and coniferous forest soils and evaluated the relationships of Trichoderma spp. populations to soil environmental factors. The total population of Trichoderma spp. increased until summer and then declined until winter. The yearly mean frequency of Trichoderma spp. exceeded 1.4% of total fungal propagules in two sites. Decreases of absolute an relative propagule numbers of Trichoderma spp. with increasing soil depth were found and variation in Trichoderma spp. propagules caused by differences in soil depth ($0{\sim}50cm$) was greater than that caused by differences in sampling time. The most common species occurring in two sites was T. viride, followed by T. polysporum, T. koningii, and T. hamatum. Individual species of Trichoderma showed diferent abundance trend in accordance with sampling time. T. viride was dorminant from spring to autumn, while T. polysporum dominated over the other speicies in winter. Variations in propagule number of Trichoderma sppp. were principally mediated by the actions of biotic environmental factors rather than by the direct effects of abiotic factors. In multiple-regression analyses, 48% of the total vaiation in Trichoderma spp. propagules in deciduous site could be accounted for by total fungal propagules and soil CMCase actvity. In coniferous site, 65% of total variation could be accounted for by total fungal and bacterial propagules, moisture content and organic carbon content.

• Korean Journal of Microbiology
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• v.19 no.4
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• pp.154-162
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• 1981

An investigation of the soil microfungal population in the paddy fields of two locations around Seoul was made at four seasons. By the dilution plate method, a total number of propagules of the microfungi pergram of soil was recorded as $10^4$ at the upper layer (0.10cm depth) followed by the middle (10-20cm depth) and the lower layer(20-30 cm depth). The highest number of fungal propagules was $11.0\;{\times}\;10^4$ at the upper layer of the soil collected in autumn. The decreasing tendency of the number of fungal propagules was depend on the increasing depth in paddy fields. Seasonal fluctuation of the fungal population was shown from the highest density of fungal colonies on the plate in autumn season and the lowest one in winter, indicating that the autumn is best season for fungal growth. Generally, the number of the species of Talaromyces in the paddy soils was found to be very high, particularly in autumn, while comparatively low in winter. The highest number of the species of Talaromyces was $6.5\;{\times}\;10^4$ propagules per gram of soil in Yukkog-dong in autumn and the lowest was $0.5\;{\times}\;10^4$ in Shinwon-dong in winter. It is assumed that these fungi grow well also in the warm to the hot seasons.

• The Korean Journal of Mycology
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• v.13 no.4
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• pp.195-201
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• 1985

Numbers of total bacteria and fungal propagules were highly populated in the soil of diseased plot in Gumsan, whereas numbers of actinomycetes were high in the soil of healthy plot in Goesan. In microbial fluctuation of different soil conditions four weeks after amended with various plant materials, bacteria were decreased in the soil amended with various plant materials as compared with non-amended soil except for Goesan. On the contrary, numbers of fungal propagules were increased amended with onion and potato stalk in two soils at different conditions, and also the propagules were enhanced in the soil amended with various plant materials in general. Higher numbers of bacteria and fungal propagules were observed in the diseased replanted plot in general, but germination rate of fungal spores relatively reversed against the microbial population. Alternaria panax was not affected much in their germination by natural soil condition, while Fusarium spp. were affected in their germination by natural soil. Natural soil showed a fungistatic effect against four fungal spores.

• The Korean Journal of Mycology
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• v.20 no.2
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• pp.109-117
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• 1992

Chemotactic responses of five motile saprophytic and one phytopathogenic bacteria e.g. Agrobacterium radiobacter, Bacillus subtilis, B. polymyxa, Pseudomonas aeruginosa, P. fluorescens and Xanthomonas malvacearum towards exudate of Cochliobolus sativus conidia, Fusarium of oxysporum f. sp. ciceri chlamydospores, Macrophomina phaseolina sclerotia and Phytophthora drechsleri f. sp. cajani oospores were determined in vitro at different abiotic conditions. In general, a positive correlation (r=0.76 to 0.89; P=0.05) was observed between concentration of fungal exudates and attraction of bacterial cells. Similarly, a significant (P=0.05; r=+0.82 to 0.95) positive correlation was noticed between chemotactic response and incubation period. The chemotactic response of bacteria was greatly influenced by temperature and pH of the test fungal exudate. The optimum temperature for maximum chemotaxis was $25^{\circ}C$ for A. radiobacter, $30^{\circ}C$ for B. polymyxa, P. aerugionosa, P. fluorescens and X. malvacearum and $35^{\circ}C$ for B. subtilis. Fungal exudates maintained at pH 7 attracted maximum number of bacteria. The response of bacterial cells to exudates at pH 3 and 11 was not significantly (P=0.05) different than that to the buffer (control). Chemotaxis of bacteria was observed towards attractants (fungal propagules and their exudates) when they were kept apart and bridged with the capillaries filled with non-attractant (buffer) or attractant (exudate).

• The Korean Journal of Mycology
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• v.14 no.2
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• pp.109-119
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• 1986

The correlations between environmental influences on microorganisms in soil and its effects on disease development in ginseng field were studied to obtain some useful data for increasing ginseng production and effective preventive measures against the root rot caused by soil-borne pathogens. The diseased replanted ginseng fields were selected as the diseased field and the healthy plot in first planted field selected as control in three major Korean ginseng producing areas such as Kumsan, Goesan and Poonggi. The physicochemical characteristics of the soil were analyzed and microorganisms susceptible for root rot of ginseng, such as Fusarium spp. and general fungi were investigated for their population density in various soil conditions. Correlations between soil microbial populations and environmental factors were investigated. The numbers of Fusarium spp. propagules were abundant in fall in both soil conditions. The numbers of Fusarium spp. were 1.9 to 2.6 times higher in replanted field than first planted field except Goesan area. Relative ratio of Fusarium spp. to total fungi propagules in replanted field was 1.6 times higher in replanted field than first planted field indicating higher numbers of Fusarium spp. distributed in replanted field of soil. The numbers of propagules of total fungi were increased in June and July and there was no sensitive variation according to the temperature. There was no significant difference in vertical distributions of total fungi according to soil depth, while the total fungi were abundant in the surface layer and $10{\sim}15\;cm$ layer. The contents of organic matter and phosphate in healthy field were somewhat high, and phosphate/organic matter ratio and Mg contents were high in diseased field. All of the soils showed a weak acidic pH of 4.5 to 5.7. Soil moisture contents were increased during winter season, but did not show any significant changes during the growing periods, showing 24.6% in healthy field and 19.5% in diseased field respectively. Soil temperature was the highest in July and August and the lowest in January and February.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1994.06a
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• pp.27-49
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• 1994

Root colonization of biocontrol agents via seed treatment was investigated and a compatible combination, Gliocladium virens G872B and Pseudomonas putida Pf3, in colonizing cucumber rhizosphere was confirmed through the study. Much higher number of fungal and bacterial propagules were detected when two isolates were inoculated together. The presence of Pf3 in root system was greatly helpful to G872B to colonize at root tip. The mechanism of this phenomenon is partially elucidated through the results of in vitro experiments and the observations of scanning electron and fluorescence microscope. Addition of Pf3 cells resulted earlier germination of G872B conidia and increased mycelial growth. And the more number of germinated conidia on seed coat, the more vigorous hypal streching and sporulation on the root surface were observed in coinoculated treatment. The propagules of G872B on the cucumber root when they were challenged against the pathogenic Fusarium oxysporum, were even higher than that of G872B treated alone, and the magnitude of such a difference was getting grater toward the root ip and the population of F. oxysporum on the root was reduced by seed inoculation of G872B. The rhizosphere competence was obviously reflected to disease suppression and plant growth promotion that induced by the given isolate. Green house experiments revealed that the combined treatment provided long-term disease suppression with greater rate and the larger amount of fruit yield than single treatments. Through this study the low temperature growing Pseudomonas fluorescens M45 and MC07 were evaluated to apply them to the winter crops in field or plastic film house. In vitro tests reveal that M45 and MC07 inhibited the mycelial growth of Pythium ultimum, Rhizoctona solani and Phytophthora capsici and enhanced growth of cucumber cotyledon in MS agar. This effect was more pronounced when the bacteria were incubated at 14$^{\circ}C$ than at 27$^{\circ}C$. And disease suppression and plant growth promotion in green house were also superior at low temperature condition. Seed treatment of M45 or soil treatment of MC07 brought successful control of damping-off and enhanced seedling growth of cucumber. The combined treatment of two isolates was more effective than any single treatment.

• Korean Journal Plant Pathology
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• v.2 no.3
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• pp.165-173
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• 1986

Accumulation of Pseudomonas sp., P. fluorescens and Erwinia carotovora in 60 min treatment was greater in extracts from soil, exudate from ginseng root and solutions than distilled water. In bacterial movement toward rubber tube soil from chamber, accumulation of P. fluorescens in response to soil supplemented with soil extracts, exudate and solutions was generally greater in soil extracts compared to control and other solutions, but Pseudomonas sp. and E. carotovora were not much response to supplemented extracts, exudate and solutions. Accumulation of the bacteria in capillaries containing various exudates from fungal propagules with not attracted to the exudates. For an accumulation of bacteria in rubber tubes containing soil inoculated with fungal propagules, the Pseudomonas sp. was not attracted in soil inoculated by the organisms as attractant but P. fluorescens and E. carotovora to fungi were attracted to F. solani, F. oxysporum and mixed organism Alternaria panax did not affect on bacterial movement except E. carotovora. The organic matter conten in Kangwha and Kimpo soil were low in diseased and healthy soil. The K content was especially high in Kimpo healthy soil. Bacterial population in Goesan and Kangwha were more abundant than other soil. The number actinomycetes was populated abundant in healthy soil of Goesan and diseased soil of Poonggi.

• Korean journal of applied entomology
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• v.61 no.1
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• pp.197-210
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• 2022

Entomopathogenic fungi can be used to control a variety of sucking and chewing insects, with little effect on beneficial insects and natural enemies. Approximately 170 entomopathogenic fungal insecticides have been registered and used worldwide, with the recent focus being on the mode of action and mechanism of insect-fungal interactions. During the initial period of research and development, the industrialization of entomopathogenic fungi focused on the selection of strains with high virulence. However, improvement in productivity, including securing resistance to environmental stressors, is a major issue that needs to be solved. Although conidia are the primary application propagules, efforts are being made to overcome the limitations of blastospores to improve the economic feasibility of the production procedure. Fungal transformation is also being conducted to enhance insecticidal activity, and molecular biology is being used to investigate functions of various genes. In the fungi-based pest management market, global companies are setting up cooperative platforms with specialized biological companies in the form of M&As or partnerships with the aim of implementing a tank-mix strategy by combining chemical pesticides and entomopathogenic fungi. In this regard, understanding insect ecology in the field helps in providing more effective fungal applications in pest management, which can be used complementary to chemicals. In the future, when fungal applications are combined with digital farming technology, above-ground applications to control leaf-dwelling pests will be more effective. Therefore, for practical industrialization, it is necessary to secure clear research data on intellectual property rights.

• Research in Plant Disease
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• v.8 no.1
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• pp.45-49
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• 2002

Seasonal occurrence of strawberry anthracnose in greenhouses caused by Colletotrichum sp. was examined from 1997 through 1999 at three locations, Kyeongju, Goryeong, and Cheongdo in Kyungbuk province, Korea. Also some factors related to the anthracnose infection such as initial infection sites, inoculation methods, and soil nature were studied through in vitro and field experiments. The anthracnose disease begun to occur from 15 days after transplanting in early October, and continued but gradually decreased thereafter for 2 months until December, After transplanting, initial infection mainly occurred through the runner of which the tissue was more susceptible to the anthracnose than those of the leaf and petiole when the fungal mycelial disk was inoculated. Postplanting inoculation by irrigation with spore suspension was much more effective in inducing the anthracnose disease than preplanting soil mix. However without inoculation, no or little anthracnose occurred regardless of commercial, non-cultivated or diseased field soils when healthy seedlings were planted. This suggests that occurrence of strawberry anthracnose in fields may be related to contamination of plant propagules with the anthracnose pathogen.

• The Korean Journal of Mycology
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• v.19 no.2
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• pp.109-119
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• 1991

The vertical distribution of the fungal population for the soil samples from two sites of producing and nonproducing of Tricholoma matsutake, song-yi mushroom, were examined at Yang­yang and Myung-joo, Gangweon province. By the dilution plate method, a total number of propagu­les of fungi per gram of soil was observed to be low at the song-yi producing sites but high at the song-yi nonproducing sites under the communities of Pinus densiflora. The tendency of the number of fungal propagules were decreased with the increasing vertical depth. In the incuhation method at $42^{\circ}C$, six genera and nineteen species of the fungi were isolated from two sites; Aspergillus fumigatus, Acremonium sp., Talaromyces stipitatus, Penicillium lilacinum, P. oxalicum and Westerdykella multispora. The most dominant species by this method was A. fumigatus. From heat treatment method at $70^{\circ}C$, seven genera and nineteen species were isolated; Aspergillus fumigatus, Alternaria alternata, Neurospora sitophila and Mucor sp.. In the ethanol treatment method, one genera and one species was isolated Mortierella sp.. From the three isolation methods, it was found that the total number of the soil fungi and the frequency of species appeared were the highest at the soil of upper layer whereas the lowest at the soils of lower layer in its vertical distribution.