• Proceedings of the Plant Resources Society of Korea Conference
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• 2002.11b
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• pp.55-55
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• 2002

Occurrences of diseased sweet flag (Acorus calamus L. var. asiaticus) were found in Chonju and Buan Province, on August 2002. The typical symptoms of the disease affected the leaves, pods, and collar of the infected plants. The leaves or pods became darker brown, then dry rotted, and white fluffy mycelia formed on the lesion. The collar, of the infected plants, formed black spot. The spores grew rapidly on PDA medium. Pathogenic fungi have not been identified clearly, as of yet. These fungi were formed from developed spores, as well as, undeveloped spores. These fungi suggest that Fusarium sp. and Rhizoctonia sp.. The range of temperatures were tested from 5$^{\circ}C$ to 35$^{\circ}C$ for mycelial growth. The optimum temperature for growth was 3$0^{\circ}C$. This is the first report on the fungus disease of sweet flag by some pathogens, in Korea. We would like to do further research for single spore isolation, pathogenity, and characterization of fungi.

• The Plant Pathology Journal
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• v.28 no.1
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• pp.10-19
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• 2012

This study investigated the distribution of endophytic fungi obtained from the surface sterilized tissues of leaves, stems and roots of chili pepper ($Capsicum$ $annuum$ L.) plants in seedling, flowering and fruiting stages in Korea and their antifungal activity. A total of 481 isolates were recovered and were identified using molecular techniques. Based on rDNA ITS gene sequence and phylogenetic analysis, 21 fungal genera were characterized, belonging to 16 Ascomycota and 5 Basidiomycota. $Penicillium$ in seedling stage, $Fusarium$ in flowering stage, $Colletotrichum$ followed by $Fusarium$, $Alternaria$ and $Xylaria$ in fruiting stage was predominant and $Alternaria$, $Cladosporium$ and $Fusarium$ were common in all growth stages. Among 481 endophytes 90 phenotypes were evaluated for the antimicrobial activity against three major pathogens ($Phytophthora$ $capsici$, $Colletotrichum$ $acutatum$ and $Fusarium$ $oxysporum$) of chili pepper. Among them 16 isolates inhibited the growth of at least one test microorganisms. Three strains showed a broad spectrum antifungal activity and displayed strong inhibition against chili pepper pathogenic fungi.

• Research in Plant Disease
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• v.24 no.2
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• pp.162-169
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• 2018

The GacS/GacA system in the root colonizer Pseudomonas chlororaphis O6 is a key regulatory system of many traits relevant to the plant probiotic nature of this bacterium. The work in this paper elucidates proteins using proteomics approach in P. chlororaphis O6 under the control of the cytoplasmic regulatory protein, GacA. A gacA mutant of P. chlororaphis O6 showed loss in production of phenazines, acyl homoserine lactones, hydrogen cyanide, and protease, changes that were associated with reduced in vitro antifungal activity against plant fungal pathogens. Production of iron-chelating siderophore was significantly enhanced in the gacA mutant, also paralleling changes in a gacS mutant. However, proteomic analysis revealed proteins (13 downregulated and 7 upregulated proteins in the mutant compared to parental strain) under GacA control that were not apparent by a proteomic study of a gacS mutant. The putative identity of the downregulated proteins suggested that a gacA mutant would have altered transport potentials. Notable would be a predicted loss of type-VI secretion and PEP-dependent transport. Study of mutants of these GacA-regulated proteins will indicate further the features required for probiotic potential in this rhizobacterium.

• The Plant Pathology Journal
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• v.32 no.6
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• pp.570-574
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• 2016

Botrytis cinerea is a necrotrophic pathogen causing a major problem in the export and post-harvest of strawberries. Inappropriate use of fungicides leads to resistance among fungal pathogens. Therefore, it is necessary to evaluate the sensitivity of B. cinerea to various classes of fungicide and to determine the effectiveness of different concentrations of commonly used fungicides. We thus evaluated the effectiveness of six classes of fungicide in inhibiting the growth and development of this pathogen, namely, fludioxonil, iprodione, pyrimethanil, tebuconazole, fenpyrazamine, and boscalid. Fludioxonil was the most effective ($EC_{50}$ < $0.1{\mu}g/ml$), and pyrimethanil was the least effective ($EC_{50}=50{\mu}g/ml$), at inhibiting the mycelial growth of B. cinerea. Fenpyrazamine and pyrimethanil showed relatively low effectiveness in inhibiting the germination and conidial production of B. cinerea. Our results are useful for the management of B. cinerea and as a basis for monitoring the sensitivity of B. cinerea strains to fungicides.

• Korean Journal of Microbiology
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• v.38 no.1
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• pp.19-25
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• 2002

Colletotrichum species are important fungal pathogen that cause great damages on various host plant species worldwide. In Korea, Colletotrichum species cause massive economic losses on apple, peach, grape, and essecially, sweet persimon productions. In the past, Identification of the pathogen and the studies on the genetic relationships among the pathogenic isolates were mainly based on morphology, cultural characteristics, and the difference in pathogenicity. However, in recent years, these traditional methods have been replaced with molecular methods to solve the difficulty of classification on pathogens. Therefore, in this study, RAPD and PCR-RFLP methods were employed for the studies of genetic relationship among the different isolates of Colletotrichum species that cause damages on sweet persimon. As a results of genetic relationship analysis, Colletotrichum species tested were divided into two big groups or five small groups.

• Mycobiology
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• v.45 no.3
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• pp.204-208
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• 2017

Nosema ceranae is an obligate intracellular fungal parasite that causes mortality in honey bees and enhances the susceptibility of honey bees to other pathogens. Efficient purification of Nosema spores from the midgut of infected honey bees is very important because Nosema is non-culturable and only seasonably available. To achieve a higher yield of spores from honey bees, in this study, we considered that the initial release of spores from the midgut tissues was the most critical step. The use of 2 mm beads along with enzymatic treatment with collagenase and trypsin enhanced the homogenization of tissues and the yield of released spores by approximately 2.95 times compared with the use of common 3 mm beads alone. The optimal time for the enzyme treatment was determined to be 1 hr as measured by the yield and viability of the spores. A one-step filtration using a filter paper with an $8-11{\mu}m$ pore size was sufficient for removing cell debris. This method may be useful to purify not only N. ceranae spores but also other Nosema spp. spores.

• Mycobiology
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• v.31 no.3
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• pp.151-156
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• 2003

Two fungal isolates obtained from roots of Cymbidium goeriingii in Jeju island were confirmed to be symbiotic with orchid plantlets, and were compared with other orchid mycorrhizal(OM) fungi previously isolated. The two isolates differed in their peloton structures formed in the roots of Cymbidium kanran hybrid 'Chungsu' and in responses of orchid plant. These two isolates differed from the additionally tested OM fungi in some features, and from root damaging species of Rhizoctonia and Fusarium as based on cluster analysis after PCR-RAPD with the primers, Bioneer-28 and OPO-2. With this simple and fast technique, it was possible to distinguish OM fungi from the plant root pathogenic fungi based on calculation of their polymorphic bands. This technique can therefore be helpful to distinguish the OM fungi from the root pathogens. Particularly, the new isolates are considered as new resource of symbiotic fungi for horticultural industries.

• Mycobiology
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• v.45 no.4
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• pp.370-378
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• 2017

Cylindrocarpon destructans is an ascomycete soil-borne pathogen that causes ginseng root rot. To identify effective biocontrol agents, we isolated several bacteria from ginseng cultivation soil and evaluated their antifungal activity. Among the isolated bacteria, one isolate (named JH7) was selected for its high antibiotic activity and was further examined for antagonism against fungal pathogens. Strain JH7 was identified as a Chromobacterium sp. using phylogenetic analysis based on 16S rRNA gene sequences. This strain was shown to produce antimicrobial molecules, including chitinases and proteases, but not cellulases. Additionally, the ability of JH7 to produce siderophore and solubilize insoluble phosphate supports its antagonistic and beneficial traits for plant growth. The JH7 strain suppressed the conidiation, conidial germination, and chlamydospore formation of C. destructans. Furthermore, the JH7 strain inhibited other plant pathogenic fungi. Thus, it provides a basis for developing a biocontrol agent for ginseng cultivation.

• Plant Biotechnology Reports
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• v.5 no.4
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• pp.301-308
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• 2011

This study tested the relative and combined efficacy of ShPx2 and ShPAL transgenes by comparing Nicotiana tabacum hybrids with enhanced levels of $_L$-phenylalanine ammonia lyase (PAL) activity and cationic peroxidase (Prx) activity with transgenic parental lines that overexpress either transgene. The PAL/Prx hybrids expressed both transgenes driven by the 35S CaMV promoter, and leaf PAL and Prx enzyme activities were similar to those of the relevant transgenic parent and seven- to tenfold higher than nontransgenic controls. Lignin levels in the PAL/Prx hybrids were higher than the PAL parent and nontransgenic controls, but not significantly higher than the Prx parent. All transgenic plants showed increased resistance to the necrotrophs Phytophthora parasitica pv. nicotianae and Cercospora nicotianae compared to nontransgenic controls, with a preponderance of smaller lesion categories produced in Prx-expressing lines. However, the PAL/Prx hybrids showed no significant increase in resistance to either pathogen relative to the Prx parental line. These data indicate that, in tobacco, the PAL and Prx transgenes do not act additively in disease resistance. Stacking with Prx did not prevent a visible growth inhibition from PAL overexpression. Practical use of ShPAL will likely require more sophisticated developmental control, and we conclude that ShPx2 is a preferred candidate for development as a resistance transgene.

• Research in Plant Disease
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• v.27 no.3
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• pp.91-98
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• 2021

The current social demand for organic, sustainable, and eco-friendly approaches for farming, while ensuring the health and productivity of crops is increasing rapidly. Biocontrol agents are applied to crops to ensure biological control of plant pathogens. Research on the biological control of white root rot disease caused by a soil-borne pathogen, Rosellinia necatrix, is limited in pears compared to that in apple and avocado. This pathogenic fungus has an extensive host range, and symptoms of this disease include rotting of roots, yellowing and falling of leaves, wilting, and finally tree death. The severity of the disease caused by R. necatrix, makes it the most harmful fungal pathogen infecting the economical fruit tree species, such as pears, and is one of the main limiting factors in pear farming, with devastating effects on plant health and yield. In addition to agronomic and cultural practices, growers use chemical treatments to control the disease. However, rising public concern about environmental pollution and harmful effects of chemicals in humans and animals has facilitated the search for novel and environmentally friendly disease control methods. This review will briefly summarize the current status of biocontrol agents, ecofriendly methods, and possible approaches to control disease in pear orchards.