• Horticultural Science & Technology
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• v.33 no.3
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• pp.429-434
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• 2015

Apple blotch-like symptoms (ABLS) were observed on 'Fuji' apple leaves in Cheongsong, Gunwi and Yeongcheon apple orchards located in Gyeongbuk Province during 2010-2014. Characteristics of ABLS were yellowing, brown spots on leaves, and defoliation, similar to apple blotch diseased (ABD) leaves, which are infected with Marssonina coronaria. It is difficult to differentiate by eye between ABLS and ABD, which has led to misdiagnosis and overuse of fungicides. The present study was conducted to investigate the cause of ABLS using stereomicroscopy, culture isolation, cross-sectional analysis of leaves, and PCR. No acervuli were found on the surface of ABLS leaves and no growth was observed on potato dextrose agar (PDA) plates in culture. Furthermore, cross-sectional analysis revealed similar results, and mycelia were absent in ABLS leaves. By contrast, all these characteristics were present in ABD leaves. Furthermore, no fungi or viruses were detected in ABLS leaves by PCR, suggesting that the disease is not caused by these agents. These findings suggest that ABLS might be a physiological disorder in plants that is distinct from ABD.

• Journal of Mushroom
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• v.1 no.1
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• pp.15-20
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• 2003

Antibacterial activities of 33 antibiotics against Pseudomonas tolaasii causing the brown blotch disease on the edible mushroom Pleurotus ostreatus, were tested in vitro for the control of the disease. Tetracyclin, kanamycin, kasugamycin, and streptomycin showed strong antibacterial activity against P. tolaasii, having the minimal inhibitory concentration of 10, 10, 100 and 200ppm, respectively. These antibiotics showed similar control value of 72.9, 71.2, 68.1 and 62.7%, respectively when applied on the artificially infected mushroom beds. Mushroom yields in the tetracycline treated boxes were increased about 31.8% comparing to the control ones. Mycelial growth of P. ostreatus on the PDA supplemented with streptomycin and kanamycin were not affected, but were inhibited 10~20% and 40% with tetracyclin and kasugamycin treatment, respectively.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2000.04a
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• pp.1-1
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• 2000

• Journal of Food Hygiene and Safety
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• v.16 no.3
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• pp.232-240
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• 2001

One hundred twenty five bacterial isolates were obtained from the brown blotch-diseased oyster mushrooms collected from markets. Among them, 45 were determined as pathogenic bacteria and white line forming organisms(WLFO) were 6 strains and white line reaction organisms (WLRO) were 6 strains. All of the white line forming isolates were identified as Pseudomonas tolaasii which is a known pathogen of brown blotch disease of oyster mushroom by GC-MIS(Gas chromatography-microbial identification system). Six of the white line reacting organisms were identified as P. chlomraphis, P. fluorescens biotype A and type C. The rest of them were P gingeri, P. agarici, P. fluorescens biotype B, P. chloroyaphis, non-pathogenic P. tolaasii, P. putida biotype A and B etc. For spectrum of activity of tolaasin, culture filtrates from pathogenic isolates were examined by browning of mushroom tissue and pitting of mushroom caps. The weak pathogenic bacteria didn't induce browning or pitting of mushroom tissue. On the other hand, strong pathogenic isolates showed browning and pitting reaction on mushroom. An extracellular toxin produced by P. tolaasii, was investigated. The hemolysis activity test of 6 strains identified as P. tolaasii were 0.8∼0.9 at 600 nm and 3 strains of WLRO were 0.9∼1.0 and Pseudomonas app. were 1.0∼1.2. Observation of fresh mushroom tissue using confocal laser scanning microscopy was carried out for images of optical sectioning and vertical sectioning. Also images of brown blotch diseased oyster mushroom tissue after contamination P. tolaasii was obtained by CLSM.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2064-2070
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• 2018

Pseudomonas tolaasii 6264 is a representative strain that causes bacterial blotch disease on the cultivated oyster mushroom, Pleurotus ostreatus. Bacteriophages are able to sterilize the pathogenic P. tolaasii strains, and therefore, they can be applied in creating disease-free mushroom cultivation farms, through a method known as "phage therapy". For successful phage therapy, the characterization of phage-resistant strains is necessary, since they are frequently induced from the original pathogenic bacteria in the presence of phages. When 10 different phages were incubated with P. tolaasii 6264, their corresponding phage-resistant strains were obtained. In this study, changes in pathogenic, genetic, and biochemical characteristics as well as the acquired phage resistance of these strains were investigated. In the phylogenetic analyses, all phage-resistant strains were identical to the original parent strain based on the sequence comparison of 16S rRNA genes. When various phage-resistant strains were examined by three different methods, pitting test, white line test, and hemolytic activity, they were divided into three groups: strains showing all positive results in three tests, two positive in the first two tests, and all negative. Nevertheless, all phage-resistant strains showed that their pathogenic activities were reduced or completely lost.

• Journal of Biosystems Engineering
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• v.41 no.3
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• pp.255-262
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• 2016

Purpose: Fuji apples are one of the top selling exports for South Korea bringing in over $233.4 million in 2013. However, during the last few decades, about half of the Fuji apple orchards have been infected by Apple Marssonina Blotch disease (AMB), a fungal disease caused by Diplocarpon mali., which takes about 40 days to exhibit obvious visible symptoms. Infected leaves turn yellow and begin growing brown lesions. AMB promotes early defoliation and reduces the quality and quantity of apples an infected tree can produce. Currently, there is no prediction model for AMB on the market. Methods: The Precision Agriculture Laboratory (PAL) at the University of Florida (UF) has been working with the National Academy of Agricultural Science, Rural Development Administration, South Korea to investigate the use of hyperspectral data in creating an early detection method for AMB. The RDA has been researching hyperspectral techniques for disease detection at their Apple Research Station in Gunwi since 2012 and disseminates its findings to the local farmers. These farmers were surveyed to assess the state of knowledge of AMB in the area. Out of a population of about 750 growers, 111 surveys were completed (confidence interval of +/- 8.59%, confidence level of 95%, p-value of 0.05). Results: The survey revealed 32% of the farmers did not know what AMB was, but 45% of farmers have had their orchards infected by AMB. Twenty-five percent could not distinguish AMB from other symptoms. Overwhelmingly, 80% of farmers strongly believed an early detection method for AMB was necessary. Conclusions: The results of the survey will help to evaluate the outreach programs of the RDA so they can more effectively educate farmers on the identifying, treating, and mediating AMB.

• Journal of Applied Biological Chemistry
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• v.63 no.4
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• pp.387-392
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• 2020

Pseudomonas tolaasii is a pathogen causing brown blotch disease in cultivated mushrooms. In previous study, various strains of P. tolaasii were isolated from the mushrooms with disease symptoms and they were further divided into Ptα, Ptβ, and Ptγ subtypes according to the 16S rRNA gene analysis. To investigate the secretion of peptide toxins, tolaasin and its analog peptides, culture extracts of Pt group strains were analyzed by gel permeation chromatography. Those of Ptα subtype strains contained two chromatographic peaks, band A and B. Meanwhile, those of Ptβ and Ptγ subtype strains contained mainly band A component and a little of band B. Molecular weights of toxic peptides of culture extracts were measured by MALDI-TOF mass spectrometry. In Ptα subtype strains, the peptide compositions of band A and B were same including tolaasin I (1,987 Da), tolaasin II (1,943 Da), and its two analog peptides, 1,973 Da and 2,005 Da. The strains of Ptβ and Ptγ subtype secreted many components of MW 1,100-1,200 Da, but they did not synthesize any tolaasin-like peptides. These results suggest that the only Ptα subtype strains secrete tolaasin and its analog peptide toxins and the strains of Ptβ and Ptγ subtypes have different pathogenic characters causing brown blotch disease.

• Korean Journal Plant Pathology
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• v.11 no.4
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• pp.348-352
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• 1995

Severe gray mold neck rot of onion occurred in most farmers' fields in the southern part of Korea, and 20∼50% of onions were infected by the disease at Goheung, Chonnam, in 1994. Symptoms of the disease appeared on the lower leaves near the soil surface in late February. The symptoms initially appeared as yellowish blotch with compact gray mold on the surface of the infected leaves and developed to blast of the aboveground parts of onions. As brown to dark brown symptoms progressed around the necks of onion later, the bulbs were rotting gradually. Botrytis sp. repeatedly isolated from the lesions produced the typical symptom on the neck of healthy onion 7 days after wound inoculation of conidial suspension of the fungus. The fungus reisolated from the bulbs was identified as Botrytis allii Munn based on the morphological and cultural characteristics and pathogenicity. This is first report of a gray mold neck rot of onion in Korea.

• The Korean Journal of Mycology
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• v.27 no.2 s.89
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• pp.132-137
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• 1999

This study was carried out to develop the molecular marker for the detection of Pseudomonas tolaasii, a causative agent of bacterial brown blotch disease of oyster mushroom (Pleurotus ostreatus). When several primers designed from repetitive sequences and pectin lyase genes of bacteria were used to produce DNA polymorphism from different Pseudomonas spp. isolated from edible mushrooms, PEU1 primer derived from pectin lyase gene produced polymorphic bands differentiating P. tolaasii strains from other Pseudomonas species. Two bands, 1.0kb and 0.4kb, found commonly in 6 isolates of P. tolaasii were cloned into pGEM-T vector which were designated as pPTOP1 and pPTOP2, respectively, to use as probe. The 0.4 kb insert of pPTOP2 hybridized to only 6 isolates of P. tolaasii, but did not to the other Pseudomonas species. As few as $1.5{\times}10^3$ colony forming unit (cfu) of P. tolaasii could be detected by dot blot hybridization with the cloned 0.4kb DNA in pPTOP2.

• Proceedings of the Korean Biophysical Society Conference
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• 1998.06a
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• pp.34-34
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• 1998

Tolaasin is a channel forming bacterial toxin produced by Pseudomonas tolaasii and causes a brown blotch disease on cultivated oyster mushrooms. When tolaasin molecules form channels in the membranes of mushroom cells, they destroy cellular membrane structure, known as 'colloid osmotic lysis'. In order to understand the molecular mechanisms forming membrane channels by tolaasin molecules, we have investigated the electrophysiological characteristics of tolaasin-induced channels in lipid bilayer.(omitted)