• Korean journal of applied entomology
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• v.24 no.3 s.64
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• pp.117-121
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• 1985

Through the laboratory and vinyl house experiments, the effects of inoculum density, plant age and temperature on the incidence of Phytophthora crown rot of pepper (Capsicum annum L.) were investigated. The propagule survival was greater in the natural soil than in autoclaved soil within first 2 weeks when the sporangial suspension of the pathogenic fungus was incorporated into soil, thereafter the survivability reduced rapidly. The propagule was not detectable in 35 days by means of Papavizas selective medium neither in natural nor in autoclaved soil. At least 5 sporangia per gram soil were required to induce crown rot for 30 days old pepper seedlings. Further increase in inoculum concentration above this threshold level resulted in higher disease incidence and shorter incubation period. When the same amount of inoculum was infested, higher disease incidence was observed for younger plants until 3 weeks after inoculation. On the other hand after 4 weeks this tendency was not extended any more. Younger plants were recognized as having shorter incubation period upon infection, however, the days from first symptom appearance to complete death were not significantly different among differently aged seedlings. Exposure of inoculated pepper seedlings to $25^{\circ}C$ resulted in highest infection rates and followed by those to $30^{\circ}C\;and\;20^{\circ}C$ but no disease was found at $15^{\circ}C\;and\;35^{\circ}C$ for 10 days. When the plants previously incubated at different temperature for 10 days were moved to $25^{\circ}C$ room temperature, prior exposure to $20^{\circ}C\;and\;30^{\circ}C$ brought continuous disease development. Even those plants preincubated at $15^{\circ}C$ were diseased up to 50%. But the prior exposure to $35^{\circ}C$ induced no symptom developed, indicating no seedlings infected at all.

• The Plant Pathology Journal
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• v.22 no.3
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• pp.248-254
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• 2006

Pear black necrotic leaf spot (PBNLS) on pear trees (Pyrus pyrifolia) is caused by a Korean isolate of Apple stem grooving virus (ASGV-K). Yellow spots were detected in Phaseolus vulgaris (kidney bean) and Chenopodium quinoa which were grown near the diseased pears in year 2000 through 2003. The ASGV-K, the causative agent of PBNLS, was detected from the symptoms of the diseased kidney bean plant and C. quinoa. ASGV-harboring fungi were also isolated from symptomatic plants and from soils surrounding the infected plants. The ASGV-harboring fungus was identified and characterized as Talaromyces flavus. Ecopathological studies showed that the number of ASGV-harboring fungi on the pear leaves was not correlated with differences in temperature or severity of symptoms. Additionally, there was no difference in fungus frequency among the orchard locations or different host plants. Although the frequency of fungi isolated from the soil was not affected by changes in temperature or location, the fungi occurred at higher densities in the rhizosphere than in the plants themselves.

• The Plant Pathology Journal
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• v.25 no.3
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• pp.231-235
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• 2009

Viral infections and root growth were examined to elucidate the relationship between viral resistance and root growth in 26 Korean hulless barley cultivars. Viral resistance was estimated in experimental filed of Honam agricultural research institute for 3 years. Length and number of seminal and adventitious roots were examined for evaluation of root growth in both field and green-house conditions 30 days after seeding. Dominant viral infection occurred in Korean hulless barley by Barley yellow mosaic virus (BaYMV) in fields; however, susceptible cultivars were infected by either BaYMV, Barley mild mosaic virus (BaMMV) or both. Only four cultivars, including Donghanchalssalbori, Kwangwhalssalbori, Namhossalbori and Naehanssalbori, presented stable resistance to viral infections. Susceptible cultivars to viral infection in fields showed shorter seminal root length and fewer adventitious root number than resistant cultivars. Resistant cultivars showed better root growth and significant difference in adventitious root length in green house conditions. Increase in the number of seminal roots in resistant cultivars was derived from decreased damage of roots by the viral infection compared to the susceptible cultivars.

• Research in Plant Disease
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• v.17 no.3
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• pp.399-401
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• 2011

Stem rot of Stachys sieboldii occurred sporadically in the farmer's fields at Shindeung-myeon, Sancheonggun, Gyeongnam province in Korea. The infected leaves and stems are water-soaked, rotted, wilted and finally leads to the death of the whole plants. The sclerotia, 1-3 mm, white to brown, globoid, were formed on lesions and the surface of soil line. The optimum temperature for mycelial growth and sclerotia formation was $30^{\circ}C$ on potato dextrose agar. The typical clamp connections were observed in the hyphae of the fungus. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of stem rot on S. sieboldii caused by S. rolfsii in Korea.

• The Plant Pathology Journal
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• v.27 no.3
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• pp.232-341
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• 2011

Pink snow mold, caused by Microdochium nivale, is a major disease on cool season turfgrasses in golf courses in northern Unites States. The relative susceptibility of 17 commercial cultivars of three bentgrass species (creeping, colonial and velvet bentgrass) to Microdochium nivale and the aggressiveness of M. nivale eight isolates obtained from infected turfgrasses on golf courses in Wisconsin were evaluated under controlled conditions. For the field trial, susceptibility of 2 year-old 12 commercial bentgrass cultivars was evaluated after inoculating three M. nivale isolates in the fields. There were significant differences in disease severities among the three bentgrass species, particularly between tetraploids (creeping and colonial) and diploid (velvet) species, and among cultivars within each species, indicating that there are varying levels of susceptibility in species and cultivars to M. nivale. Host resistance by days of cold hardening was confirmed, by detecting the resistance by 30 days of cold hardening treatments. In field trial, susceptibility of 12 bentgrass cultivars was highly correlated to the results obtained from growth chamber experiments. The positive correlation of the susceptibility between growth chamber experiments and field trials demonstrates that the growth chamber method is a useful technique for saving time, space and labor to evaluate efficiently pink snow mold susceptibility of bentgrass cultivars. This study could be applied to evaluating susceptibility of bentgrass to pink snow mold and also predicting a prospective evaluation of bentgrass cultivars to pink snow mold in fields in a breeding program.

• Research in Plant Disease
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• v.21 no.4
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• pp.334-336
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• 2015

Sclerotium rot on Pulsatilla koreana was observed in the exhibition field of Jinju Agriculture Technology Center in July 2013. The infected plants showed water-soaked, blighted and rotted symptoms. White mycelial mats spread over lesions, and then numerous sclerotia were formed on flower stalk and flower 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 mycelial growth and sclerotia formation on PDA was $30^{\circ}C$ and the hyphal width was $4-8{\mu}m$. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. For molecular identification, the complete ITS rDNA sequence of the causal fungus was sequenced and analyzed. On the basis of mycological characteristics, ITS rDNA sequence analysis, and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of sclerotium rot on Pulsatilla koreana caused by S. rolfsii in Korea.

• Applied Biological Chemistry
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• v.14 no.2
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• pp.171-175
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• 1971

Gibberella fujikuroi(imperfect stage Fusarium moniforme) a soil fungi is well known as the producer of plant growth regulator Gibberellins. The present work was planned for the isolation of the active strains of Gibberella fujikuroi from the native paddy soils. Twenty two strains were isolated from the infected rice seedlings collected from four local areas. Pyongtaek, Yesan, Tangjin and Sunchon and screened through the activity test for the production of Gibberellins. The strains P-105, Y-14 and T-58 yielded higher activity than the others isolated and the referred strain IAM-8048. The strains Y-5, Y-7, T-54 and S-152, however, were less promotive or rather inhibitory in the growth of rice seedlings. Six different kinds of culture media developed by Cross, Raulin-Thom, Borrow, West, Stodola and Kurosawa respectively were compared with each other for the production of Gibberellins and the best result was obtained with Raulin-Thom's media(glucose 16% and $NH_4NO_3$ 0.24%).

• Journal of Bio-Environment Control
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• v.16 no.3
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• pp.252-257
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• 2007

This study was carried out to clarify the effects of antifungal Streptomyces sp. isolated from the soil grown kiwifruit on the growth inhibition of fruit rot (Botryosphaeria dothidea) infected in kiwi fruit plants in the southwestern districts of Jeonnam. Two hundred and fifty microorganisms were isolated and examined into the antifungal activity against Botryosphaeria dothidea. We screened and isolated six bacterial strains which have a strong inhibition against Botryosphaeria dothidea. And the best antifungal strain designated as the strain #120 showing 96.0% antifungal activity against Botryosphaeria dothidea was finally selected. The strain #120 was identified as Streptomyces sp. #120 based on its morphological, physiological, biochemical and chemotaxonomic characteristics.

• The Korean Journal of Mycology
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• v.33 no.2
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• pp.98-102
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• 2005

In 2003 to 2005, the root rot of Japanese angelica (Aralia elata) was surveyed in nursery beds of Korea, where incidence of the disease often reached up to 100%. Three isolates were obtained from the infected roots, and identified as Phytophthora cactorum on the basis of cultural, morphological characteristics and molecular analysis. The isolates were characterized by having markedly papillate and broadly ovoid deciduous sporangia. The optimum temperature for mycelium growth was at $25^{\circ}C$ on V8 juice agar. Pathogenicity of the isolates was confirmed by soil mixture inoculation. Approximately 900 bp of ITS rDNA was amplified from all 3 isolates and band pattern of restriction fragments observed by Alu I, Msp I, and Taq I digestion also supported the result of the morphological identification when compared with PhytID database.

• Korean journal of applied entomology
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• v.26 no.1 s.70
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• pp.25-30
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• 1987

An unusual disease syndrome, partial stem rot and final blight of the whole plants was observed in sesame, Sesamum indicum L., cultivar Pungnyeonkkae and Kwangsankkae grown in the field. Symptoms progressed from water-soaking continuous banding lesions on one side of stem to producing abundant Fusarium growth on the lesion at late stage of pathogenesis. Although wilting of plants was most frequently observed in sesame seedlings when infected with Fusarium oxysporum, reproduction of the partial stem discoloration and rot was possible by soil inoculation, and wound inoculation in old plants. The disease occurred from late July. Mycological characteristics of the isolate Fusarium oxysporum compared with those reported in sesame suggested that the isolate might be F. oxysporum f. sp. sesame.