• The Korean Journal of Mycology
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• v.50 no.4
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• pp.357-360
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• 2022

In July 2021, we surveyed diseases affecting wild vegetables grown in Hongcheon, Gangwon Province, Korea. During this survey, we observed severe seedling rot symptoms in Kamchatka goatsbeard (Aruncus dioicus) grown in a vinyl greenhouse. The incidence of the disease in the plant seedlings was 1-10%. Diseased seedlings from this population were collected, and fungi were isolated from leaf and petiole lesions. Rhizoctonia sp. was consistently isolated from the lesions. We examined the morphological and cultural characteristics and anastomosis groups of nine Rhizoctonia sp. isolates obtained from the lesions. The results revealed that all isolates corresponded to Rhizoctonia solani AG-1(IB). Three isolates of R. solani AG-1( IB) were evaluated to determine their pathogenicity towards Kamchatka goatsbeard seedlings through artificial inoculation. The tested isolates caused rot symptoms on the inoculated plant seedlings. The symptoms were similar to those observed in plant seedlings from the vinyl greenhouse. We found that R. solani AG-1(IB) caused seedling rot of Kamchatka goatsbeard.

• Journal of Ginseng Research
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• v.14 no.3
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• pp.432-436
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• 1990

Incidence of damping-off callsed by Rhizoctonia solani was 0.6-10.9% at "Yangjik" seedbed in Pocheon, Korea. The seedbeds where the lengths of etiolated stems (underground portion) of ginseng seedlings were 0.78-1.25 cm showed 0.8-3.2% of the disease, while 6.9-10.9% disease incidence was observed at the seedbeds with the longer etiolated stem (1.89-2.26 cm). The pathogen produced a typical girdle symptom on the etiolated portion of ginseng stems close to the soil surface. The deeper the seeds were sown, the more the disease occurred in pot soil inoculated with the pathogen, AG 2-1, showing 18.4, 27.4 and 32.9% of damping-off at the seeding depth of 1, 2 and 4 cm, respectively. Cuticle layers of colored stems (over ground portion) were well - developed to be 42.8, 58.0, and 55.0 um in thickness compared to the etiolated stems with 8.5, 15.0 and 8.0um for seedling, 2 year-old, and 3 year-old ginsengs, respectively, when the disease occurred. In the seedling and 2 year-old ginseng, the colored stems were more rigid than the etiolated. There was however, no difference in rigidness of the stem of the 3 year-old ginseng where the disease is not severe as in seedlings and 2 year-old ginseng plants.ng plants.

• Plant Disease and Agriculture
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• v.5 no.1
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• pp.1-7
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• 1999

The grain rot of caused by Bukholderia glumae was fist reported in japan in 1955 and then reported in other countries as well as in Korea in 1986. The pathogen causes both seedling and grain rot of rice but it cannot attack any other parts of adult rice plant. Bacterial colonies grow slowly, and are circular and greyish white. The causal bacterium is Gram-negative and rod shape with 1-3 polar flagella, and produce a diffusible yellow-greenish nonfluorescent pigment on King's medium B. Biochemical characteristics such as negative in arginine dehydrolase, oxidase reaction and nitrate reduction and positive in lecithinase, and the utilization of L-arginine and inositol are useful in differentiation of this from other nonfluorescent bacteria pathogenic to rice. This pathogenic bacterium had belonged to the genus of Pseudomonas but recently was transferred to the new genus Burkholderia on the basis of physiological characteristics and DNA-DNA hybridization data. However, other characteristics such as colony heterogenicity or colonial variation after subcultures, phytotoxin, secreting antibiotics, and relationship between yellow greenish pigment production and pathogenicity need to be clarified more. To develop an effective control strategy for this disease, understanding of detailed life cycle of the disease and critical environmental factors affecting disease development is prerequisite. Although 5,435 ha of rice paddy in Korea was infested during 1998, there is no exact estimation of yield losses and distribution of the pathogen. The review will focus on recent progress on the understanding of the bacteriological and ecological characteristics of the causal bacterium and control means of the disease.

• Mycobiology
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• v.51 no.3
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• pp.186-194
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• 2023

In July 2021, wilting symptoms were observed in adult and seedling hemp (Cannabis sativa L. cv. Cherry Blossom) plants grown in a greenhouse. As the disease progressed, yellowing and wilting symptoms on the leaves developed, resulting in whole plant death. In seedling plants, typical damping-off symptoms were observed. To identify the pathogen, the roots of diseased plants were sampled, surface sterilized, and cultured on potato dextrose agar (PDA) media. From the culture, 4 different fungal isolates were recovered and purely cultured. Each fungal isolate showed distinct growth shapes and color development on malt extract agar, oatmeal agar, sabouraud dextrose agar, and PDA media. Microscopic observation and molecular identification using ribosomal DNA internal transcribed spacer sequencing identified them as 3 Fusarium spp. and 1 Thielaviopsis paradoxa. Additional sequencing of elongation factor 1-alpha and b-tubulin regions of 3 Fusarium spp. revealed that 2 of them are Fusarium solani, and the other one is Fusarium proliferatum. To examine which isolate can act as a causal agent of wilt disease of hemp, each isolate was tested for their pathogenicity. In the pathogenicity test, F. solani AMCF1 and AMCF2, and F. proliferatum AMCF3, but not T. paradoxa AMCF4, were able to cause wilting disease in hemp seedlings. Therefore, we report that F. solani AMCF1 and AMCF2, and F. proliferatum AMCF3 as causal agents of Fusarium wilt of hemp plants. To our knowledge, this is the first report of the wilt disease of C. sativa L. caused by Fusarium spp. in Korea.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.70.2-70
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• 2002

• Journal of Ginseng Research
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• v.4 no.2
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• pp.186-193
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• 1980

The causal organism of Phytophthora disease on Panax ginseng Meyer in Korea was isolated and identified as Phytophthora cactorum. It's pathogenicity, etiology, and possible control measures were investigated. Disease symptoms on various parts of ginseng plants were also described The fungus caused seedling and mature plant blight and root rot. Oospores were easily formed on potato dextrose agar and corn meal agar. Oospores, however, were not formed in the diseased root tissues but did in the in footed shoots such as leaves, petioles, and stems and in the inoculated berries.

• Research in Plant Disease
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• v.9 no.2
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• pp.64-67
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• 2003

Clubroot disease of Chinese cabbage has extremely occurred in recent years. Conventional soils such as sandy loam soil (saprolite) and clay soil (yellow soil) as bed media combined with field soil application of fungicidal chemicals were tested for the control of clubroot disease. Using sandy loam soil and clay soil as plug seedling bed media efficiently reduced clubroot disease occurrence down to 21.7% and 14.1%, respectively compared to peatmoss (75.7%) and Baroco soil (36.6%) when seedling plants were transplanted into previously-infected Yoncheon field. Application of flusulfamide and azoxystrobin to previsouly-infected soil prior to transplanting also effectively reduced disease incidence, especially when combined with growing seedlings in sandy loam or clay soil media. In conclusion, flusulfamide application prior to trnasplanting as well as utiliz-ing sandy loam and clay soil as a plug bedding media may effectively reduce the occurrence of clubroot dis-ease of Chinese cabbage.

• Mycobiology
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• v.38 no.4
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• pp.286-294
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• 2010

Epicoccum purpurascens stain 5615 AUMC was investigated for its biocontrol activity against root rot disease caused by Pythium irregulare. E. purpurascens greenhouse pathogenicity tests using three leguminous plants indicated that the fungus was nonpathogenic under the test conditions. The germination rate of the three species of legume seeds treated with a E. purpurascens homogenate increased significantly compared with the seeds infested with P. irregulare. No root rot symptoms were observed on seeds treated with E. purpurascens, and seedlings appeared more vigorous when compared with the non-treated control. A significant increase in seedling growth parameters (seedling length and fresh and dry weights) was observed in seedlings treated with E. purpurascens compared to pathogen-treated seedlings. Pre-treating the seeds with the bioagent fungus was more efficient for protecting seeds against the root rot disease caused by P. irregulare than waiting for disease dispersal before intervention. To determine whether E. purpurascens produced known anti-fungal compounds, an acetone extract of the fungus was analyzed by gas chromatography mass spectrometry. The extract revealed a high percentage of the cinnamic acid derivative (trimethylsiloxy) cinnamic acid methyl ester. The E. purpurascens isolate grew more rapidly than the P. irregulare pathogen in a dual culture on potato dextrose agar nutrient medium, although the two fungi grew similarly when cultured separately. This result may indicate antagonism via antibiosis or competition.

• Journal of Ginseng Culture
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• v.6
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• pp.51-79
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• 2024

In the 1970s and 1980s, during the nascent phase of ginseng disease research, efforts concentrated on isolating and identifying pathogens. Subsequently, their physiological ecology and pathogenesis characteristics were scrutinized. This led to the establishment of a comprehensive control approach for safeguarding major aerial part diseases like Alternaria blight, anthracnose, and Phytophthora blight, along with underground part diseases such as Rhizoctonia seedling damping-off, Pythium seedling damping-off, and Sclerotinia white rot. In the 1980s, the sunshade was changed from traditional rice straw to polyethylene (PE) net. From 1987 to 1989, focused research aimed at enhancing disease control methods. Notably, the introduction of a four-layer woven P.E. light-shading net minimized rainwater leakage, curbing Alternaria blight occurrence. Since 1990, identification of the bacterial soft stem rot pathogen facilitated the establishment of a flower stem removal method to mitigate outbreaks. Concurrently, efforts were directed towards identifying root rot pathogens causing continuous crop failure, employing soil fumigation and filling methods for sustainable crop land use. In 2000, adapting to rapid climate changes became imperative, prompting modifications and supplements to control methods. New approaches were devised, including a crop protection agent method for Alternaria stem blight triggered by excessive rainfall during sprouting and a control method for gray mold disease. A comprehensive plan to enhance control methods for Rhizoctonia seedling damping-off and Rhizoctonia damping-off was also devised. Over the past 50 years, the initial emphasis was on understanding the causes and control of ginseng diseases, followed by refining established control methods. Drawing on these findings, future ginseng cultivation and disease control methods should be innovatively developed to proactively address evolving factors such as climate fluctuations, diminishing cultivation areas, escalating labor costs, and heightened consumer safety awareness.

• Journal of Ginseng Research
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• v.14 no.1
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• pp.50-56
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• 1990

Root-rot of ginseng caused by Fusarium solani is one of the most obstacles to ginseng cultivation. We evaluated some inoculating techniques of ginseng with Fusarium solani, for selection of disease resistant breeding lines. The most effective inoculating techniques evaluated were inserting toothpicks colonized by F. solani into the seedling roots in laboratory test and dusting seedlings with vermiculite after dipping in conidial sllspension and then replanting method in field test. The resistance to diseased by F. solani was lines of 82022 and 82066 in laboratory test. 82920-1 and 78093 in field test.