• Research in Plant Disease
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• v.11 no.2
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• pp.128-134
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• 2005

This study was conducted to elucidate effect of environmental factors on the development of white rot. In order to identify the causal agents causing white rot of Allium crops, we compared DNA profiles of a representative isolate, Sclerotium cepivorum, introduced from foreign country with Korean isolates using UP-PCR. As a result, Sclerotium isolates forming round-shaped sclerotia were identified as Sclerotium cepivorum pertaining in UP-PCR b group and Sclerotium isolates farming anamorphic-shaped sclerotia presumed to be a novel species of Sclerotium based on DNA profiles of UP-PCR. There was a big difference in DNA band pattern between two species of Sclerotium isolated in Korea. Electron micrographs of scanning electron microscope and transmission electron microscope showed morphological differences in sclerotial surface structure and rind layers between two species of Sclerotium. There were more wrinkles and pore spaces on sclerotial surface of Sclerotium sp. forming anamorphic-shaped sclerotia than that of Sclerotium cepivorum forming round-shaped sclerotia. Both of two white rot pathogens grew well at the temperature range of $10-25^{\circ}C$ with optimal temperature of $20^{\circ}C$. Sclerotia of the two pathogens were well formed at $20^{\circ}C$ and well germinated at the temperature range of $20-24^{\circ}C$, Effect of pre-incubation of sclerotia on destruction of sclerotial dormancy of two pathogens was evaluated through storing sclerotia under different temperature condition. The sclerotia of the two pathogens showed an increased capacity to germinate on potato dextroise agar when the sclerotia were incubated for 7 days at $10^{\circ}C$ after pre-treatment at $35^{\circ}C$ for 7 days. At that time, germination rate of Sclerotium sp. and 5. cepivorum was $100\%\;and\;70\%$, respectively. Flooding period and treatment temperature had an effect on sclerotial survival rate of the two pathogens. As flooding period and treatment temperature increased, sclerotial germination rate of the two pathogens decreased. It was confirmed that soil humidity played an important role on development of white rot. It was the highest disease incidence of garlic white rot when garlic were sown at potted soils infested with the two pathogens and adjusted soil humidity to $15\%$ (field moisture capacity, about -300 mb). As soil humidity increase or decrease based on $15\%$ of soil humidity, disease incidence decreased move and more.

• The Korean Journal of Mycology
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• v.45 no.3
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• pp.246-250
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• 2017

Sclerotium rot was observed on mungbean (Phaseolus radiatus L.) plants cultivated in the exhibition field of Gyeongsangnam-do Agricultural Research and Extension Services in September 2015. The progression of rot was initially observed as water-soaked lesions on several parts of the affected plant. Severely infected plants were blighted and eventually died. White mycelial mats spread over the lesions and numerous sclerotia formed on stems near the 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 potato dextrose agar (PDA) was $30^{\circ}C$ and the hyphal width was $4{\sim}8{\mu}m$. Typical clamp connections were observed on the hyphae of fungus grown on PDA. For molecular identification, the complete internal transcribed spacer (ITS) ribosomal DNA (rDNA) of the causal fungus was sequenced and analyzed. Based on the mycological characteristics, ITS rDNA sequence analysis, and pathogenicity to host plants, the fungus was identified as Sclerotium rolfsii. This is the first report of Sclerotium rot on mungbean caused by S. rolfsii in Korea.

• Research in Plant Disease
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• v.19 no.3
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• pp.229-232
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• 2013

Sclerotium rot of cucumber (Cucumis sativus L.) occurred at the experimental field of Gyeongsangnam-do Agricultural Research and Extension Services in July 2012. The typical symptoms included wilt, rot, and water-soaking on stems and fruits and severely infected plants eventually died. White mycelial mats spread over lesions, and then sclerotia were formed on fruit and near soil line. The sclerotia were globoid in shape, white to brown in color and 1-3 mm in size and the hyphal width was 4-8 ${\mu}m$. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. For further identification, the complete internal transcribed spacer (ITS) rDNA region was amplified and sequenced. On the basis of mycological characteristics, ITS rDNA region comparison, and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of sclerotium rot on cucumber caused by S. rolfsii in Korea.

• Research in Plant Disease
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• v.12 no.2
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• pp.69-74
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• 2006

Basal rot of freesia caused by a Sclerotium sp. occurred at Incheon areas. Incidence of the disease reached up to 45% and averaged 17.0% in the fields. Typical symptoms consisted of sheath dry and leaf blight due to rots on basal leaves. The causal fungus was identified as Sclerotium sp. based on following mycological characteristics. The fungus formed sclerotia on cultural media and plant tissues, but did not produce asexual spores. On cultural medium, aerial mycelia of the fungus changed color from white to clay with cultural age and smelled musty odor. Numerous irregular and elliptical black microsclerotia of the fungus were formed on potato dextrose agar (PDA) after 5 days of incubation at $25^{\circ}C$ and sized $115{\sim}200{\times}95{\sim}150 (av. 145{\sim}126.5){\mu}m$. The fungus grew at $10{\sim}32^{\circ}C$ and $pH 4.0{\sim}8.5$. However, the optimal temperature and pH for mycelial growth of the fungus were $24^{\circ}C$ and 5.5 respectively. The isolate showed present pathogenicity to not only freesia but gladiolus in the pathogenicity test, and the symptoms were similar to those observed in the fields. Basal rot of freesia caused by Sclerotium sp. is firstly reported in Korea.

• 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.

• The Korean Journal of Mycology
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• v.37 no.2
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• pp.198-200
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• 2009

From 2008 to 2009, the stem rot of Astragalus sinicus L. caused by Sclerotium rolfsii occurred sporadically in Gyeongnam area, Korea. The typical symptom is water-soaking, rotting and wilting on the stem. The infected plants were eventually died. White mycelial mats were spread over lesions, and then sclerotia were formed on stems and near soil line. The sclerotia were globoid in shape, white to brown in color, 1-3 mm in size and the hyphal width was 3-9 μm. The optimum temperature for mycelial growth and sclerotial formation on PDA was 30oC. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the stem rot of A. sinicus 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.

• The Plant Pathology Journal
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• v.23 no.3
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• pp.212-214
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• 2007

In 2005 and 2007, a basal stem rot of Disporum smilacinum caused by Sclerotium rolfsii occurred sporadically in a herb farm at Hamyang, Korea. The symptom initiated with water-soaking lesion and progressed into stem rot and wilt of a whole plant. Severely infected plants were blighted and died eventually. White mycelial mats appeared on the lesion at early stage and a number of sclerotia were formed on the stem near the soil line. The sclerotia were globoid in shape, 1-3 mm in size and white to brown in color. The optimum temperature for the growth and sclerotia formation was 30 on PDA and the hyphal width was measured $3-8{\mu}m$. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. On the basis of symptom, mycological characteristics and pathogenicity to the host plant, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report on the stem rot of D. smilacinum caused by S. rolfsii in Korea.

• Mycobiology
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• v.37 no.2
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• pp.158-159
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• 2009

In 2007 to 2008, a fruit rot of Melon (Cucumis melo L.) caused by Sclerotium rolfsii occurred sporadically in a farmer's vinyl house in Jinju City. The symptoms started with watersoaking lesion and progressed into the rotting of the surface of fruit. White mycelial mats appeared on the lesion at the surface of the fruit and a number of sclerotia formed on the fruit near the soil line. The sclerotia were globoid in shape, 1${\sim}$3 mm in size, and white to brown in color. The hyphal width was measured 3 to 8 ${\mn}$. The optimum temperature for mycelial growth and sclerotia formation was 30 on PDA. Typical clamp connections were observed in hyphae of grown for 4 days on PDA. On the basis of symptoms, mycological characteristics and pathogenicity to the host plant, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of the fruit rot of Melon caused by S. rolfsii in Korea.

• Research in Plant Disease
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• v.9 no.4
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• pp.221-223
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• 2003

In May 2002, a destructive stem rot of Obedient plant (Physostegia virginiana) occurred sporadically in an exhibition farm of Hamyang-gun, Gyeongsangnam-do Agricultural Research and Extension Services, Korea. The typical symptoms of the disease were stem rot, crown rot, wilt or blight. Upper parts of the infected stems were mostly blighted. White mycelial mats were spread over lesions and the sclerotia were formed on the stems near soil line. The sclerotia was globoid or irregular in shape, 1${\sim}$3 mm in size, and brown in color. The optimum temperature for fungal growth was about $30^{\circ}C$. The typical clamp connections were observed in the hyphae of the fungus grown on PDA, and hyphal diameter was 3.6${\sim}$9.4 ${\mu}m$. On the basis of mycological characteristics and test of pathogenecity to host plants, the fungus was identified as Sclerotium rolfsii. This is the first report on the stem rot of Physostegia virginiana caused by Sclerotium rolfsii in Korea.