• Journal of Forest and Environmental Science
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• v.34 no.5
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• pp.395-404
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• 2018

Since the mass mortality of Quercus mongolica has been first reported in Gyeonggi province at 2004, the disease spread rapidly over Korean peninsula annually. Ambrosia beetle (Platypus koryoensis) was known as the insect vector of oak wilt fungus, Raffaelea quercus-mongolicae, and control methods of the disease had mainly been focused on eradication of insect vector. However, for the efficient management of the disease, combined control methods for both of the pathogenic fungus and insect vector are strongly required. As one of the efforts to suppress the pathogenic fungus, antifungal activities of Streptomyces isolated from oak forest soil were assayed in this study. Optimum culture condition for the selected isolates was also studied, As a result, Streptomyces blastmyceticus cultured in PDB (Potato Dextrose Broth) at $25^{\circ}C$ for 1 week showed the strongest antifungal activity against oak wilt fungus. Mycelial growth inhibition rates (MGIRs) of Streptomyces isolates were compared on culture media supplemented with heated and unheated culture filtrates of S. blastmyceticus. MGIRs on culture media with unheated culture filtrates were generally higher than those on culture media with heated culture filtrates. Antagonistic mechanism to get involved in the inhibition of hyphal growth and spore formation of the pathogen is due to the antifungal metabolites produced by Streptomyces. This study will provide the fundamental information in developing biocontrol agents for the environment-friendly management of oak wilt disease.

• The Korean Journal of Mycology
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• v.26 no.1 s.84
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• pp.78-85
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• 1998

During the screening of biological control agents for insect pests in the greenhouse, 70 dead insect-related fungi were isolated and tested insecticidal effect of their culture filtrates was tested. From this studies, CNAB-63 isolate showed strong control effects against the cotton aphids and the two-spotted spider mite as 65.19% and 77.55%, respectively. The insecticidal active compound of CNAB-63 isolate was purified from culture filtrate by silica gel chromotography, thin layer chromatography and HPLC. Purified active compound (CNAB) showed control effects against the two-spotted spider mite with 63.45% at $100\;{\mu}g/ml$ concentration. However, it did not exhibit antimicrobial activity against fungi and bacteria.

• Mycobiology
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• v.37 no.1
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• pp.48-52
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• 2009

Essential oils are mixtures of volatile, lipophilic compounds originating from plants. Some essential oils have useful biological activities including antimicrobial, spasmolytic, antiplasmodial, and insect-repelling activities. In this study, we tested the antimicrobial activity of essential oil prepared from the aromatic plant, Cymbopogon citrates, against three important plant pathogenic and medical microorganisms, Pectobacterium carotovorum, Colletotrichum gloeosporioides, and Aspergillus niger. It effectively inhibited the growth of the bacterium, Pectobacterium carotovorum, in a dose-dependent fashion, and 0.5% of the oil inhibited the growth of bacteria completely. Similarly, the essential oil inhibited the growth of plant pathogenic fungus, Colletotrichum gloeosporioides, and the addition of 1% of essential oil completely inhibited the growth of fungus even after 5 days of culture. Finally, it effectively inhibited the growth of the medically and industrially important fungal species, Aspergillus spp. These results suggest that the essential oil from Cymbopogon citrates may be an environmentally safe alternative to inhibit antimicrobial agents for various uses.

• Journal of Korean Society of Forest Science
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• v.96 no.1
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• pp.58-64
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• 2007

Overwintering adults of sycamore lace bug (Corythucha ciliata) infected by an unidentified pathogenic fungus were found on the stems of street trees of sycamore in Cheongju city. The objective of this study was to describe this entomopathogenic fungus infecting overwintering sycamore lace bug adults. This unidentified fungus colonized the insect adult body and formed white colony with subglobose clusters of conidiocarps. The size of conidiocarps was 300 to $400{\mu}m$ and each conidium was 15 to $20{\mu}m$. The conidiospore was globus and 2.5 to $3.0{\mu}m$ in diameter, and the hyphae were 1 to $5{\mu}m$ thick. This fungus was successfully isolated and cultivated on potato dextrose agar medium (PDA). The fungal colony was white and then became light yellow. When conidia from this pure culture were inoculated into the overwintering adults, the fungus formed conidiocarps with the same morphology on the insect body and the lethal rate by the fungus was $88{\pm}16%$. This fungus has over 99% homology with Cordyceps bassiana (imperfect fungal name is Beauveria bassiana) in ITS-5.8s rDNA base sequence. The fungal ecology and the infection process of the fungus into its host need to be clarified before using this fungus as a biological control agent.

• Journal of Korean Society of Forest Science
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• v.112 no.1
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• pp.117-125
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• 2023

Outbreaks of Ramulus mikado (Insecta: Phasmatodea: Phasmatidae) in the hilly areas of Mt. Bongsan, Mt. Cheonggye, and elsewhere in Seoul and Gyeonggi occurred from 2020 to 2021, causing serious defoliation. We evaluated the insecticidal effects of six eco-friendly organic materials and the insect-pathogenic fungus Metarhizium anisopliae against R. mikado. The fungus was isolated from naturally dead bodies of R. mikado in forest ecosystems. The results revealed that three eco-friendly organic materials containing azadirachtin or geraniol as active ingredients showed high mortality in the range of 85.2%-100%, which were rates similar to that of the chemical insecticide fenitrothion emulsifiable concentrate. All R. mikado adults that were sprayed with a conidial suspension of M. anisopliae at different concentrations were killed within a few days. In conclusion, three eco-friendly organic materials and M. anisopliae could be good alternatives to chemical insecticides.

• Journal of Korean Society of Forest Science
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• v.104 no.2
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• pp.332-335
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• 2015

Taphrina wiesneri, a pathogen of cherry witches' broom, is highly pathogenic to Prunus yedoensis Matsumura which are widely planted in parks and streets in South Korea. In order to control the disease, it is crucial to know the life cycle of the fungus. We attempted to detect the fungus tentatively overwintering in shoots and branches of cherry trees both having witches' broom and healthy before flowering and leafing in spring using PCR with species-specific primer set (TwITSF and TwITSR). Genomic DNAs were extracted from the symptomatic and the asymptomatic shoots or branches. Results indicated that T. wiesneri is present in leaf buds and inner bark not only in symptomatic branches but also in the asymptomatic branches in diseased trees. However, the fungus was not detected in flower buds of the symptomatic trees and any samples of healthy trees.

• Journal of Microbiology and Biotechnology
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• v.12 no.6
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• pp.950-956
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• 2002

The antitumor activity of the insect pathogenic fungus Paecilomyces japonica has been attributed to apoptotic cell death. However, the mechanism underlying the induced apoptosis has not yet been elucidated. In this study, we for the first time show that mitochondria-dependent caspase-3 activation were associated with the apoptotic activity of P. japonica in human acute leukemia Jurkat T cells. When Jurkat T cells were treated with the ethyl acetate extract of P japonica at concentrations ranging from $2-6{\mu}g/ml$, apoptotic cell death. accompanied by several biochemical events such as caspase-9 activation, caspase-3 activation, degradation of poly (ADP-ribose) polymerase (PARP), and apoptotic DNA fragmentation, was induced in a dose-dependent manner. In addition, the release of cytochrome c from mitochondria was detected. Under these conditions, the expression of Fas and Fas-ligand (FasL) remained unchanged. Ethyl acetate extract-induced mitochondrial cytochrome c release, caspase-3 activation, PARP cleavage, and apoptotic DNA fragmentation were suppressed by the ectopic expression of Bcl-2, which is known to block mitochondrial cytochrorme c release. Accordingly, these results demonstrate that P. japonica-induced apoptotic cell death is mediated by a cytochrome c-dependent caspase-3 activation pathway that can be interrupted by Bcl-2.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.465-469
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• 2016

An entomopathogenic fungus was isolated from the two-spotted spider mite (Tetranychus urticae) in a rearing house, and identified as Neozygites floridana (Entomophthorales: Neozygitaceae). A high infection rate induced by N. floridana could increase the price of the natural enemy. The body color of mites infected by this fungus changed to red or orange and swelling occurred. Fungal conidia were discharged into the webbing produced by the spider mites, making it relatively easy to infect the mites. Primary conidia were pear shaped and capilliconidia almond shaped. The fungus could not be cultured on solid media (PDA, SDAY, or EYSDA), but could possibly be cultured in liquid media (Grace's insect tissue culture medium + 5% fetal bovine serum). Kidney beans were supplied as food for T. urticae; the mite infection rate in a kidney bean canopy was about 36.1%. The density of infected mites was higher on the underside than on the upper side of leaves. Based on the results of this survey, we need to identify methods of fungal control for natural enemy production and biological control agents for T. urticae for effective crop management.

• Research in Plant Disease
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• v.17 no.1
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• pp.99-101
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• 2011

The ascomycetous fungus Taphrina wiesneri, the pathogen of cherry witches' broom, is highly pathogenic to Prunus yedoensis, the most widely planted cherry trees in Korea as park and roadside trees. A collection of 13 strains of the pathogen in Korea and Japan was characterized by 18S rDNA gene sequence and restriction fragment length polymorphism (RFLP) analysis. In cluster analysis based on 18S rDNA gene sequence the strains were divided into 2 clusters. In RFLP analysis of the rDNA-IGS region using HhaI, the strains were separated into four patterns, B, C, D and G, of which pattern G was new.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.889-893
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• 2012

Appressorium is a specialized infection structure of filamentous pathogenic fungi and plays an important role in establishing a pathogenic relationship with the host. The Egh16/Egh16H family members are involved in appressorium formation and pathogenesis in pathogenic filamentous fungi. In this study, a homolog of Egh16H, Magas1, was identified from an entomopathogenic fungus, Metarhizium acridum. The Magas1 protein shared a number of conserved motifs with other Egh16/Egh16H family members and specifically expressed during the appressorium development period. Magas1-EGFP fusion expression showed that Magas1 protein was not localized inside the cell. Deletion of the Magas1 gene had no impact on vegetative growth, conidiation and appressorium formation, but resulted in a decreased mortality of host insect when topically inoculated. However, the mortality was not significant between the Magas1 deletion mutant and wild-type treatment when the cuticle was bypassed by injecting conidia directly into the hemocoel. Our results suggested that Magas1 may influence virulence by affecting the penetration of the insects' cuticle.