• The Plant Pathology Journal
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• v.18 no.2
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• pp.57-62
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• 2002

In vivo expression technology (IVET) has been developed to study bacterial gene expression in Salmonella typhimurium during host infection. The expression of selected genes by IVET has been elevated in vivo but not in vitro. The selected genes turned out to be important for bacterial virulence and/or pathogenicity. IVET depends on a synthetic operon with a promoterless transcriptional fusion between a selection marker gene and a reporter gene. The IVET approach has been successfully adapted in other bacterial pathogens and plant-associated bacteria using different selection markers. Pseudomonas putida suppresses citrus root rot caused by Phytophthora parasitica and enhances citrus seedling growth. The WET strategy was adapted based on a transcriptional fusion, pyrBC'-lacZ, in P. putida to study the bacterial traits important far biocontrol activities. Several genes appeared to be induced on P. parasitica hyphae and were found to be related with metabolism and regulation of gene expression. It is likely that the biocontrol strain took a metabolic advantage from the plant pathogenic fungus and then suppressed citrus root rot effectively. The result was parallel with those from the adaptation of IVET in P. fluorescens, a plant growth promoting rhizobacteria (PGPR). Interestingly, genes encoding components for type III secretion system have been identified as rhizosphere-induced genes in the PGPR strain. The type III secretion system may play a certain role during interaction with its counterpart plants. Application of IVET has been demonstrated in a wide range of bacteria. It is an important strategy to genetically understand complicated bacterial traits in the environment.

• The Plant Pathology Journal
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• v.15 no.1
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• pp.44-47
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• 1999

Fungal isolates belong to Fusarium solani (perfect stage : Nectria haematococca) were isolated form pea, ginseng roots and soybean during 1995 and 1996 in Korea. Thirty-five isolates were identified as F. solani f. sp. pisi based on the morphological characteristics and their pathogenicity. Microconidia formed on the long conidiophore were ovoid or oblong sizing 5~14 x 2.5~5.0 $\mu\textrm{m}$. Macroconidia were formed on carnation leaf agar media with 4.8~5.3 x 32.0~40.7 $\mu\textrm{m}$ in size. They belonged to $\beta$-type since their 3-septate macroconidia were smaller than $5\mu\textrm{m}$ in width. Chlamydospores were smooth- or rough- walled and formed in terminal or lateral branches of hyphae, intercalary, or in chains. Most isolates were highly virulent to pea seedlings, producing dark brown or rot lesions. This is the first report of f. solani f. sp. pisi being pathogenic to pea in Korea.

• The Plant Pathology Journal
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• v.17 no.6
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• pp.350-353
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• 2001

In 2001, a black scab disease was observed in tea plant (Thea sinensis) cultivated in the hillsides of Hwngaemyon and Hadong-gun, Gyeongnam province, Korea. The disease symptoms initially appeared on leaves, green twigs and stems, showing small dark brown spots on the infected areas, which gradually expanded. A fungus was isolated from diseased leaves and green twigs. It grew readily on potato dextrose agar, forming dark green to dark gray colonies. The optimum temperature for mycelial growth was about 20$^{\circ}C$. The diameter of growing hyphae was 3.5-5.8 $\mu\textrm{m}$. Conidia were ellipsoidal, ovoid or subspherical, and mostly one-celled but occasionally septate. The size of one-celled and septate conidia were 3.7-12.4${\times}$3.4-5.2 $\mu\textrm{m}$ and 9.3-18.7${\times}$3.8-7.2 $\mu\textrm{m}$, respectively. Conidia were formed in long branched chains on the erected conidiophores, which were dark brown in color and 28.9-218.3${\times}$3.0-6.1 $\mu\textrm{m}$ in length. The fungus was identified as Cladosporium herbarum on the basis of its morphological characteristics. The black scab disease occurring in tea caused by Cladosporium herbarum has not been previously reported in Korea.

• Korean Journal Plant Pathology
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• v.2 no.3
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• pp.158-164
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• 1986

Histopathological changes of strawberry plants infected with Fusarium oxysporum f. sp. fragariae Winks & Williams were examined. In all sections of the plant parts including roots, crowns, petioles and runners naturally and artificially infected with the fungus, fungal hyphae and conidia, and their plugging were found in xylem vessels, and formation of cavities was noted in the vascular cylinders. The xylem vessels were not localized with pectic materials, tyloses were not formed, and xylem parenchyma cells were not hypertrophied. The results suggest that plugging or disconnection of xylem elements by the fungus may be an important factor in inducing characteristic symptoms associated with Fusarium wilt of strawberry.

• The Plant Pathology Journal
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• v.26 no.2
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• pp.185-188
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• 2010

This study was undertaken to isolate and to identify a fungal pathogen Monilinia sp. KV-27 associated with apple anthracnose. Rotted Fuji apples were used for the isolation of the fungus. The infected tissues were sterilized with 70% ethanol, washed with sterilized distilled water and were transferred to 50 ml containing potato dextrose broth (PDB) flasks. The peripheral hyphae of the fungal colony which developed from the infected tissues were isolated on to potato dextrose agar (PDA). On PDA plates the fungus grew well at $25^{\circ}C$ and occupied more than half of a 9 cm petri dish within 5 days. The fungal cultures on PDA were used for morphological observation and identification of the fungus. Conidiophores were produced on the gray to whitish sporodochial structures scattered on PDA plates. These conidiophores gave rise to chains of conidia, which were branched and easily detached in water. These structures were dark brown to black and consisted of hyphal masses. Conidia produced on PDA plates were hyline or light colored, lemon shaped or ellipsoidal ($10-13{\times}8.5-11{\mu}m$) in size.

• Research in Plant Disease
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• v.16 no.3
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• pp.323-325
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• 2010

The stem rot of sunflower (Helianthus annuus) occurred sporadically in the experimental field of Gyeongsangnam-do Agricultural Research and Extension Services, on September, 2009. The infected plants were wilted and water-soaked brown spots were formed on the stem, than infected stems were mostly died. White mycelial mats were spread over lesions, and then sclerotia were formed on stem and near soil line. The sclerotia were globoid in shape, 1~3 mm in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$ and the hyphal width was $4{\sim}8\;{\mu}m$. The typical clamp connections were observed in the hyphae of the pathogenic fungus. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii. This is the first report on the stem rot of sunflower by S. rolfsii in Korea.

• Mycobiology
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• v.31 no.1
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• pp.1-8
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• 2003

Detailed structures of ectomycorrhizae formed in Pinus roots were observed with various microscopes: light, fluorescence, and scanning electron microscopes. The mantles and Hartig nets commonly found in the structure of ectomycorrhiza were newly observed according to developmental stage by various staining. The mycelia were observed to be composed of coiled types on the surface of epidermal root during early stage and fused to form mantles of smooth fungal layers, loosing mycelia with some viscous liquid secreted. The ectomycorrhizal hyphae in anatomical roots penetrated the cortical layer and formed obviously mantle and Hartig net. The round spots of ectomycorrhizal mycelia were observed morphological distribution from the cortical layer to vascular bundle of stele in the ectomycorrhizal roots of Pinus species and especially scattered at the area of meristem at the root tip as longitudinal sections. Those mycelia penetrated seemed to move into other roots by means of vascular bundle of ectomycorrhizal roots and newly form ectomycorrhizal roots of dichotomous branches.

• Mycobiology
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• v.43 no.2
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• pp.170-173
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• 2015

Herein, we report the first occurrence of web blight of rosemary caused by Rhizoctonia solani AG-1-IB in Gangneung, Gangwon Province, Korea, in August 2014. The leaf tissues of infected rosemary plants were blighted and white mycelial growth was seen on the stems. The fungus was isolated from diseased leaf tissue and cultured on potato dextrose agar for identification. The young hyphae had acute angular branching near the distal septum of the multinucleate cells and mature hyphal branches formed at an approximately $90^{\circ}$ angle. This is morphologically identical to R. solani AG-1-IB, as per previous reports. rDNA-ITS sequences of the fungus were homologous to those of R. solani AG-1-IB isolates in the GenBank database with a similarity percentage of 99%, thereby confirming the identity of the causative agent of the disease. Pathogenicity of the fungus in rosemary plants was also confirmed by Koch's postulates.

• Mycobiology
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• v.39 no.1
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• pp.26-32
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• 2011

Powdery mildew is one of the most devastating diseases in cucurbits. Crop yield can decline as the disease severity increases. In this study, we evaluated the effect of silver nanoparticles against powdery mildew under different cultivation conditions in vitro and in vivo. Silver nanoparticles (WA-CV-WA13B) at various concentrations were applied before and after disease outbreak in plants to determine antifungal activities. In the field tests, the application of 100 ppm silver nanoparticles showed the highest inhibition rate for both before and after the outbreak of disease on cucumbers and pumpkins. Also, the application of 100 ppm silver nanoparticles showed maximum inhibition for the growth of fungal hyphae and conidial germination in in vivo tests. Scanning electron microscope results indicated that the silver nanoparticles caused detrimental effects on both mycelial growth and conidial germination.

• The Korean Journal of Mycology
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• v.16 no.4
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• pp.247-252
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• 1988

The uptake of isolated Lyophyllum ulmarium chromosomes by Ganoderma applanatum protoplasts was induced with polyethylen $glycol+CaCl_2+glycine$. Uptake products of chromosomes by protoplasts showed micro-and macrotransgenome type. The former was slowly growing and unstable, the latter was outgrowing and stable mycelial colonies which made thick hyphae of width and segregation of mycelial colony on GCM containing benomyl. A comparison of macrotransgenome type was using isozyme analysis of esterase. The enzyme pattern of two transformants was distinct in position and quantity compared with parents.