• The Korean Journal of Mycology
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• v.51 no.2
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• pp.141-146
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• 2023

Stem rot symptoms were observed in Gondre (Cirsium setidens) plants growing in a vinyl greenhouse in Taebaek, Korea during a disease survey in June 2022. The plants presented with dark brown to black rot on the stems at or above the soil line. Severely diseased plants displayed wilt and blight. Disease incidence among these plants ranged from 1 to 5%. Three isolates of Rhizoctonia sp. were obtained from the stem lesions of diseased plants. All isolates were identified as Rhizoctonia solani AG-2-2(IV) based on the morphological and cultural characteristics, results of the anastomosis test, and phylogenetic analysis. The pathogenicity of the isolates to Gondre plants was confirmed using an artificial inoculation test. The lesions induced by the inoculation test were similar to those observed in the investigated vinyl greenhouse. Here, we report a case of R. solani AG-2-2(IV) causing stem rot in Gondre.

• Mycobiology
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• v.32 no.2
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• pp.95-97
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• 2004

In July 2002, a destructive stem rot of tawny daylily(Hemerocallis fulva) was occurred sporadically in exhibition farm of Gyeongsangnam-do Agricultural Research and Extension Services located in Hamyang-gun, Korea. The fungus also caused collar and crown rot, and systemic wilt or blight of whole plant. White mycelium spread over stems and petioles of infected plants and sclerotia were formed on the old lesions and near the soil surface. The optimum temperature for mycelial growth and scierotial formations was $30^{\circ}C$ on PDA. The mycelial width ranged $4.2{\sim}10.4{\mu}m$ and the color was white, usually many narrow mycelial strand grew in the aerial mycelium and formed clamp connection. The shape of sclerotia was spherical and $1.0{\sim}3.2$ mm in diameter. The fungus was isolated repeatedly from the infected tissues and confirmed its pathogenicity to Hemerocallis fulva and identified as Sclerotium rolfsii. This is the first report on the stem rot of H. fulva caused by S. rolfsii in Korea.

• Mycobiology
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• v.38 no.2
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• pp.156-158
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• 2010

Stem rot disease was found in garlic (Allium sativum L.) cultivated from 2008 to 2010 in the vegetable gardens of some farmers in Geumsan-myon, Jinju City, Gyeongnam province in Korea. The initial symptoms of the disease were typical water-soaked spots, which progressed to rotting, wilting, blighting, and eventually death. White mycelial mats had spread over the lesions near the soil line, and sclerotia had formed over the mycelial mats on the stem. The sclerotia were globoid in shape, 1~3 mm in size, and tan to brown in color. The optimum temperature for growth and sclerotia formation on potato dextrose agar (PDA) medium was $30^{\circ}C$. The diameter of the hyphae ranged from approximately 4 to $8\;{\mu}m$. Typical clamp connection structures were observed in the hyphae of the fungus, which was grown on PDA medium for 4 days. On the basis of the mycological characteristics and pathogenicity of the fungus on the host plants, the causal agent was identified as Sclerotium rolfsii Saccardo. This is the first report of stem rot disease in garlic caused by S. rolfsii in Korea.

• The Plant Pathology Journal
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• v.26 no.3
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• pp.231-237
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• 2010

The heat-inactivated (at $121^{\circ}C$ for 20 min) conidial suspension of Bipolaris cactivora (HICS) was evaluated for the control of Bipolaris stem rot of cactus caused by B. cactivora. Severe rot symptoms were developed on the cactus stem discs inoculated with B. cactivora from 5 days after inoculation. However, only small brownish spots developed on the stem discs treated with HICS 2 days prior to the pathogen inoculation. HICS also reduced symptom development on cactus stem discs inoculated with other fungal pathogens such as Alternaria alternata, Colletotrichum gloeosporioides, and Fusarium oxysporum, suggesting its disease-inhibitory efficacy may not be pathogen-specific. HICS significantly reduced severities of the stem rot disease on several cactus species including Hylocereus trigonus, Cereus peruvianus, Chamaecereus silvestrii and Gymnocalycium mianovichii, but not on Cereus tetragonus. Extensive wound periderms were formed in the stem tissues of inoculation and/or wounding sites on C. peruvianus treated with HICS alone or prior to the pathogen inoculation, but not on C. tetragonus, indicating the structural modifications may be related to the mechanism of disease suppression by HICS. HICS also reduced the disease development on the grafted cactus (H. trigonus stock and G. mianovichii scion) with the control efficacy nearly equivalent to the application of a commercial fungicide. All of these results suggest HICS can be used as an environmental-friendly agent for the control of the cactus stem disease.

• 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.

• Mycobiology
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• v.29 no.1
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• pp.58-60
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• 2001

A destructive stem rot of wild aster(Aster koraiensis) occurred sporadically some farmers' fields in Guman-myon, Kosonggun, Kyongsangnam-do in 2000. One of the most severely infected field in Kosong showed 28.6 percent of infection rate. The fungus also caused stem or crown rot and systemic wilt or blight of the plants. White mycelium spread over stems and petioles of infected plants and sclerotia formed on the old lesions and near the soil surface. The fungus showed maximum mycelial growth around $30^{\circ}C$ and did not grow under $5^{\circ}C$ and over $45^{\circ}C$ and mycelial width were $4.3{\sim}10.2{\mu}m$. Colony was white, usually many narrow mycelial stand in the aerial mycelium and formed clamp connection. Numerous sclerotia were formed on PDA at $30^{\circ}C$. The shape sclerotia were globoid and $0.8{\sim}3.0{\times}0.9{\sim}3.4$ mm in size. The fungus was isolated repeatedly from the infected tissues and confirmed its pathogenecity to wild aster and identified as Sclerotium rolfsii. This is the first report on the stem rot of wild aster caused by S. rolfsii in Korea.

• Mycobiology
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• v.39 no.1
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• pp.57-58
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• 2011

Stem rot was found for the first time on the Asiatic dayflower plant (Commelina communis L.) in Korea. A detailed description of this Korean specimen is given, along with its rDNA internal transcribed spacer sequence. The fungus was identified as Sclerotium rolfsii Saccardo based on mycological characteristics and molecular data.

• Mycobiology
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• v.28 no.4
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• pp.180-184
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• 2000

In order to find an environment-friendly method to suppress astragal stem rot caused by the isolates of Rhizoctonia solani AG 1 and AG 4, we tested an antagonistic fungus Gliocladium virens G1 was evaluated as a biocontrol agent and estimated inorganic compounds and organic materials were tested for their effect of the disease suppression. G. virens G1 effectively inhibited mycelial growth in a dual culture and caused mycelial lysis in the culture filtrate. No adverse effect was observed when examined for seed germination and seedling growth. Promoted seedling growth was observed with the seed treatment. Seeds of astragal plant were germinated higher in the sterile soil than the natural soil. Of 14 inorganics tested, alum, aluminum sulfate and calcium oxide significantly suppressed the mycelial growth and sclerotial germination. Milled pine bark and oak sawdust also suppressed the mycelial growth. Soil amended with 1% of G. virens G1 composted with pine bark (w/v) significantly controlled astragal stem rot in the glasshouse experiments.

• Mycobiology
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• v.40 no.4
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• pp.268-271
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• 2012

In June 2012, leaf spot and stem rot were observed on Wilford Swallowwort plants grown in Cheonan, Korea. Three fungal isolates obtained from the diseased leaves and stems were identified as Stemphylium lycopersici, based on morphological, cultural, and molecular characteristics and pathogenicity. This is the first report of leaf spot and stem rot on Wilford Swallowwort caused by S. lycopersici.

• Research in Plant Disease
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• v.7 no.1
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• pp.56-59
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• 2001

Stem rot of cacti was found at major cultivating areas including Koyang, Ansung and Eumsung of Korea in 2000. Bipolaris cactivora was consistently isolated from the lesions. The disease occurred on different species of cactus including Cereus peruvianus, C. neopithahaja f. monstruo년, C. tetragonus, Chamaeceresu silestrii, Ch. silvestrii, f. variegata, Gymnocalcium mihanovichii var. friedrichii. G. denudatum var. pentacantha, Hylocereus trigonus and Isolatocereus dumortier. Major symptoms on the cactus species except H. trigohus were almost identical. A rapid rot of the upper portion of the catus stem appeared, and became blackened and somewhat dry. On H. trigonus, the symptom was initially light yellow, water-soaked lesion, turned into light brown and dried to death. According to pathogenicity test, 10 out of 16 cactus species and varieties tested produced identical symptoms as found in the field. However, the fungi did not show pathogenicity to Notocactus scopa, Echinocactus grusonii, Eriocactus leninghausii, Lobivia nealeana, Mammillaria elongata var. intertexta.