• Research in Plant Disease
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• v.8 no.4
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• pp.245-249
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• 2002

Monosporascus cannonballus, a soilborne ascomycetes is recently described in Korea that causes root rot/vine decline of cucurbits. The effect of Monosporascus root rot disease on photosynthetic activity and growth was studied on oriental melon plants. At harvest stage, photosynthetic activity of diseased oriental melon plants was lower and stomatal resistance was higher than healthy plants, while xylem exudates were not observed in diseased plants. There was no difference in mineral contents of the leaves and stems between diseased and healthy plants. Leaf area, fresh and dry weights, and fruit weights of the plants were markedly decreased in diseased plants compared to those of healthy plants.

• The Plant Pathology Journal
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• v.19 no.3
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• pp.152-158
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• 2003

Stromata of the white root rot fungus, Rosellinia necatrix, were produced on diseased roots although they were reported to develop rarely in nature. Forty-two (42) out of 47 samples produced synnemata while 23 developed stromata. Forty-seven (47) isolates obtained from diseased root samples were divided into 24 mycelium compatibility groups (MCGs). Sixteen (16) out of 24 MCGs produced stromata. Single ascospore isolates from 10 stroma samples produced dsRNA-containing isolates from diseased tissue beneath stromata. The frequency of synnema production on axenic culture varied among isolates with different origin. The dsRNA was not transmitted vertically to the ascospore offspring despite the infection of various dsRNA in the parental isolates. The dsRNA was absent in 35 ascospore isolates in two stroma samples that originated from the isolates, in which dsRNA was not eliminated by hyphal tip isolation. Consequently, sexual reproduction in the white root rot fungus was suggested to produce propagules as a new infection source and to have the function to eliminate infectious factors such as mycoviruses.

• The Korean Journal of Mycology
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• v.36 no.2
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• pp.203-205
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• 2008

From 2006 to 2008, the stem rot of Petunia hybrida Vilm. caused by Sclerotium rolfsii occurred sporadically at Jinju city in Gyeongsangnam-do. The typical symptom is water-soaking, brown on the stem and rotting, wilting and blighting. The infected plants 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, $1{\sim}3\;mm$ in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation was at $30^{\circ}C$ on PDA and the hyphal width ranged from 4 to $8{\mu}m$. The typical clamp connections were observed in the hyphae of the fungus. On the basis of mycological characteristics and pathogenicity to P. hybrida, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the stem rot of P. hybrida caused by S. rolfsii in Korea.

• Research in Plant Disease
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• v.24 no.2
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• pp.138-144
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• 2018

In December 2016, stem rot symptoms were observed on Persian buttercup (Ranunculus asiaticus) plants in Chilgok, Gyeongbuk, Korea. In the early stage of the disease, several black spots appeared on the stem of infected plants. As the disease progressed, the infected stem cleaved and wilted. The causal agent was isolated from a lesion and incubated on Reasoner's 2A (R2A) agar at $25^{\circ}C$. Total genomic DNA was extracted for phylogenetic analysis. Based on the 16S rRNA gene analysis, the isolated strain was found to belong to the genus Pseudomonas. To identify the isolated bacterial strain at the species level, the nucleotide sequences of the gyrase B (gyrB) and RNA polymerase D (rpoD) genes were obtained and compared with the sequences in the GenBank database. As the result, the causal agent of the stem rot disease was identified as Pseudomonas marginalis. To determine the pathogenicity of the isolated bacterial strain, it was inoculated into the stem of healthy R. asiaticus plant, the inoculated plant showed a lesion with the same characteristics as the naturally infected plant. Based on these results, this is the first report of bacterial stem rot on R. asiaticus caused by P. marginalis in Korea.

• The Plant Pathology Journal
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• v.18 no.3
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• pp.156-160
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• 2002

Cymbidium orchids with blight and rot symptoms were collected, and a total of 63 isolates of Fusarium app. was obtained from pseudobulbs, roots, and leaves of the diseased plants. The isolates were identified based on their morphological characteristics. Out of the 63 isolates of Fusatium sup., 51 isolates were identified as F. oxysporum, 10 isolates as F. solani, and the rest as F. proliferatum. F. oxysporum was isolated from all the Cymbidium spp., while F. solani and F. proliferatum were isolated only from Cymbidium ensifolium and C. ginatum, respectively. Isolates of the three Fusarium spp. were tested for pathogenicity to their hosts by artificial inoculation. The strongly pathogenic isolates of Fusarium spp. induced severe dry rot of pseudobulbs and roots of the host plants. The symptoms progressed up to the basal part of the leaves, which later caused blight of the entire plant. The dry root symptoms induced on the plants by artificial inoculation with the isolates of Fusarium app. were similar to those observed in the growers'greenhouses. This is the first report of dry rot of Cymbidium spp. caused by F. oxysporum, F. solani, and F. proliferatum in Korea.

• Research in Plant Disease
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• v.8 no.2
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• pp.113-116
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• 2002

A sclerotinia rot of Leonurus sibiricus caused by Sclerotinia sclerotio겨m occurred severely in farmer's fields at Seosang-myon, Hamyang-gun, Gyeongnam Province, Korea in 2001. The typical symptoms of the disease were that leaves, stems or collar of the infected plants at first became darker green and then watery soft rotted, and white fluffy mycelia formed on the lesion developed into black sclerotia later, Sclerotia on the plant and PDA medium were globose to cylindrical or irregular in shape, and 0.8~10.3$\times$0.8~6.4 m in size. Aphothecia with numerous asci were cup-shape, and 0.6~1.2 cm in diameter, Asci with 8 spores were cylindrical, and 87~246$\times$4.6~21.6 $\mu\textrm{m}$ in size. Ascospores of one cell were hyaline, ellipsoid to ovoid in shape, and 10.2~14.6$\times$4.7~7.2 $\mu\textrm{m}$ in size. The range of temperature for mycelial growth was from 5 to 3$0^{\circ}C$, and the optimum was $25^{\circ}C$. This is the first report on the sclerotinia rot of L. sibiricus caused by Sclerotinia sclerotioum in Korea.

• Research in Plant Disease
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• v.8 no.1
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• pp.50-54
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• 2002

A total of 55 Colletotrichum isolates from strawberry plants with anthracnose symptoms(crown rot) were inhibited in mycelial growth on potato-dextrose agar(PDA) amended with fungicides in variable degrees depending on the chemicals used, especially showing no growth on PDA with 1 mg/m/tricyclazole. However, in the detached leaf test by treating chemicals before or after inoculation of Colletotrichum sp., tricyclazole was little effective in controlling symptom development; instead azoxystrobin, which had low in vitro inhibition of mycelial growth, inhibited strongly the symptom development. Some chemicals were tested for the control of strawberry crown rot in greenhouse using three methods, sprays soil drenching and plant dipping. No or little control effect were made by chemical spray and soil drenching, but plant dipping in chemical solution, especially azoxystrobin: reduced crown rot development by about 50% in the greenhouse suggesting that the azoxystrobin treatment may be an effective control method of the crown rot of strawberry. No differences in the control efficacy were noted according to the dipping time and chemical concentration of azoxystrobin not less than 10 min and 250 mg/m/, respectively.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.642-645
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• 1998

A severe pink mold rot on matured melon fruits occurred under a glass tunnel cultivation in Chinju at Kyeongasngnam-do Agricultural Research and Extention Services on May of 1998. Basal portion of the fruits toward blossom end was preferably infected and colonized by the fungus. The causal fungus consistently isolated from the lesions was identified as Trichothecium roseum based on following mycological characteristics. Conidia were hyaline or brightly colored, 2-celled, ovoid or elipsoid, characteristically held together zi-zag chains. Conidiophore was long, slender, simple, septate, bearing conidia-meristem arthrospores-apically, singly when young and successively by slight growth of conidiphore apex. Optimum temperature for mycelial growth and conidial germination was recorded at 20~$25^{\circ}C$. However, over 48% of the fungal conidia were germinated at 15$^{\circ}C$ and mycelial growth was only slightly slower than $25^{\circ}C$. The temperature profiles and high humidity available during the cultivation were considered favorable for the pathogen as showing 22% infection rate on matured melon fruits cv. Saros. This is the first report of pink mold rot of melon caused by T. roseum in Korea.

• Research in Plant Disease
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• v.7 no.3
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• pp.140-144
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• 2001

Occurrence of ripe rot in Vitis vinifera cv, Campbell Early was examined at Daegu, Yaungchon, and Kimchon in Kyungbuk province, Korea from 1997 through 1999. Its occurrence was related to rainfall days in July and Auguest. In cv, Campbell Early, the disease started in late July, and increased rapidly from mid August. Considering the incubation time, the pathogen infection might have increased from late July, which was confirmed by wrapping grape clusters in field and in vitro tests. By scanning electron microscopy, it took 24 h or longer for infection to occur in moisturized conditions. Chlrorothalonyl WP (500$\times$) sufficiently reduced ripe rot disease when the chemical was sprayed 3 or 4 times during the growing season.

• The Plant Pathology Journal
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• v.19 no.6
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• pp.280-283
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• 2003

A soybean-sprout rot epidemic occurred in a mass production soybean sprout factory in 2000 and 2001 in Korea, which caused up to 20% production loss. Among the causal pathogenic bacteria and fungi, Pythium deliense was found to be the dominant pathogen of severe root and hypocotyls rot, particularly in recirculating water system. An average of 90% of the isolated fungi from the rotted sprout on potato dextrose agar were Pythium sp. The fungal density of Pythium in the sampled water was monitored in the recycled water system for 1 year using a selective medium (com meal agar with Pimaricin, 10 mg； Rifampicin, 10 mg； and Ampicillin, 100 mg per 1 liter). The drained water from the soybean-sprout cultivation always had a certain amount of fungus in it. The removal of Pythium from the recycling water system must be thorough, safe, and environment friendly. However, the pathogen in the water was easily found even after ozone and chlorine treatments, which were devised on the recycling system for the removal of microorganisms. 5-$\mu\textrm{m}$ pore size filter was applied and was able to successfully control the disease. As the sprout industry increasingly shifts into mass production, the demand for water will increase continuously. Recycling water for sprout production is eco-friendly. However, a process must be devised to be able to first decompose organic matters before Pythium zoospores are filtered.