• Mycobiology
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• 제45권3호
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• pp.129-138
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• 2017

In this study, we aimed to characterize fungal samples from necrotic lesions on collar regions observed in different sweetpotato growing regions during 2015 and 2016 in Korea. Sclerotia appeared on the root zone soil surface, and white dense mycelia were observed. At the later stages of infection, mother roots quickly rotted, and large areas of the plants were destroyed. The disease occurrence was monitored at 45 and 84 farms, and 11.8% and 6.8% of the land areas were found to be infected in 2015 and 2016, respectively. Fungi were isolated from disease samples, and 36 strains were preserved. Based on the cultural and morphological characteristics of colonies, the isolates resembled the reference strain of Sclerotium rolfsii. Representative strains were identified as S. rolfsii (teleomorph: Athelia rolfsii) based on phylogenetic analysis of the internal transcribed spacer and large subunit genes along with morphological observations. To test the pathogenicity, sweetpotato storage roots were inoculated with different S. rolfsii strains. 'Yulmi' variety displayed the highest disease incidence, whereas 'Pungwonmi' resulted in the least. These findings suggested that morphological characteristics and molecular phylogenetic analysis were useful for identification of S. rolfsii.

• Mycobiology
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• 제38권4호
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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.

• 농업생명과학연구
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• 제50권2호
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• pp.25-32
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• 2016

A severe outbreak of gray mold on kenaf (Hibiscus cannabinus L.) was observed on kenaf grown in the research field of Gyeongsangnam-do Agricultural Research and Extension Services, Jinju, Korea in 2014. Gray mold appeared on young plants as gray-brown velvety mold covering stems and leaves. Infections that girdled the stem caused wilting above the infected area and developed a canker. The casual fungus formed grayish brown colonies on potato dextrose agar. The conidia were one celled, mostly ellipsoid or ovoid in shape, colorless or pale brown in color, and 6-18 × 4-10 ㎛ in size. The conidiophores were 15-32 ㎛ in length. These measurements and taxonomic characteristics were most similar to those of Botrytis. DNA sequencing and phylogenetic analysis of the complete internal transcribed spacer rRNA gene region confirmed that the fungal isolates were indeed Borytis cinerea. Koch's postulates were supported by pathogenicity tests conducted on healthy plants. On the basis of mycological characteristics and pathogenicity test on host plants, the fungus was identified as Botrytis cinerea. To the best of our knowledge, this is the first report of a gray mold caused by B. cinerea on kenaf in Korea.

• The Plant Pathology Journal
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• 제20권1호
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• pp.58-62
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• 2004

White root rot of wild white clover (Trifoliorum repens) caused by isolate BWC98-105 has been first reported in Korea. Typical symptoms on root include water-soaked and dark-brown rot, resulting in complete blight of the whole plant. The fungus grew well at $20-28^{\circ}C$ and produced abundant sclerotia at 10-15 days after full mycelial growth on potato dextrose agar. Sclerotia were brown to dark-brown in color and 1-3 mm in length. When white clover plants were inoculated with mycelial suspension ($10^5$ cfu/ml) of isolate BWC98-105, the plant shoots were killed within 4-6 days and the roots were completely blighted. Sclerotia were also formed on the surface of the root covered with whitish mycelia within 10-15 days in the field. All nine isolates developed high incidences of white root rot disease on white clover seedlings, of which the symptoms were similar to those observed in the fields. Hence, their pathogenicity was confirmed on white clover. The infection rate of the fungal isolates varied from 78.5% to 95.2%, among which BWC98-105 was the most virulent isolate. The weeding efficacy of the fungus was maintained until the following year, leading to a significant reduction of reshooting. The fungus was specifically parasitic to white clover, but not to four lawn species including zoysiagrass (Zoysia japonica) under greenhouse test. The fungus also had no response to some Gramineae species including rice, but caused little damage to five species of Leguminosae.

• 식물병연구
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• 제28권4호
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• pp.209-220
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• 2022

Charcoal canker of oak, which has recently increased in southern Iran, could pose a serious threat to the entire forest ecosystem in the near future. In addition, it seems that climate change and its consequences, such as drought in the southern regions of Iran, have exacerbated this phenomenon. Consequently, the objective of this study was to identify the fungal pathogens that could cause charcoal canker disease in the oak forests of South Zagros. It was also sought to find associations between changes in the occurrence/exacerbation of charcoal canker disease under non and intense drought stress in non-inoculated or inoculated Quercus brantii seedlings. In total, 120 isolates were obtained from eight oak forests located in the Zagros Mountains of Southern Iran, Kohgiluyeh & Boyer-Ahmad and Fars provinces, which were classified as Biscogniauxia mediterranea based on morphological assessment. Subsequently, molecular assay confirmed the result by phylogenetic inference of internal transcribed spacer-rDNA regions, α-actin, and β-tubulin genes. The results of the pathogenicity test showed that the response of isolates of B. mediterranea (Iran-G1 and Iran-M70) was varied in different environments for the measured necrotic lesion length. In comparison with the control moisture treatments (non-stress), the necrotic lesion length in inoculated treatments increased under intense drought stress. In general, inoculated oak seedlings' exposure to water-deficient stress by the pathogen of B. mediterranea could affect the spread/severity of the charcoal canker disease.

• 한국균학회지
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• 제13권3호
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• pp.179-183
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• 1985

Cylindrocarpon속균(屬菌)이 딸기가 재배(栽培)되는 포장(圃場)의 토양(土壤)에서 토양희석법(土壤稀釋法)으로 분리(分離)되었다. 감자한천배지에서 일주일에 10 mm정도 자라는 균(菌)이며 회백색의 conidial slime을 형성(形成)한다. 균사(菌絲)에서 침상의 phialide의 분생자경(分生子梗)으로 분지(分枝)되고 그위에 소형분생포자(小型分生胞子)와 대형분생포자(大型分生胞子)를 형성(形成)한다. 대형분생포자(大型分生胞子)는 $1{\sim}3$개(個)의 격막(隔膜)을 가지며 크기는 $22{\sim}45{\times}5{\sim}6.5\;{\mu}m$이고 무색원통형(無色圓筒形)으로 양끝은 반원형(半圓形)이다. 후막포자(厚膜胞子)는 water agar상에서 균사(菌絲)의 중간(中間)이나 정단부(頂端部)에서 하나 혹 연쇄상으로 형성(形成)된다. 포자(胞子)나 균사(菌絲)는 서로 쉽게 격합(隔合)된다. 병징(病徵)은 지상부(地上部)에서는 위축(萎縮)되든지 황화(黃化)되며 지하부(地下部)의 뿌리는 썩어 병원성(病原性)이 인정(認定)되었다. 본균(本菌)은 포자(胞子)의 형태(形態), 균사(菌絲)의 생장(生長)과 병원성검정(病原性檢定)을 통(通)하여 Cylindrocarpon destructans Scholten으로 동정(同定)되었다.

• Mycobiology
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• 제48권4호
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• pp.245-251
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• 2020

During a survey of putative fungal pathogens infecting oak trees in the Gangwon Province of the Republic of Korea, a fungus resembling a Ceratocystis sp. was repeatedly isolated from natural wounds on Quercus variabilis. Morphological comparisons and DNA sequence comparisons based on partial β-tubulin and TEF-1α gene regions showed that the fungus resided in a distinct lineage. This novel Ceratocystis species is described here as C. quercicola sp. nov. This is the first novel species of Ceratocystis to be reported from Korea. A pathogenicity test showed that it can cause lesions on inoculated trees but that it had a very low level of aggressiveness. The discovery of this fungus suggests that additional taxa residing in Ceratocystis are likely to be discovered in Korea in the future.

• Mycobiology
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• 제47권1호
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• pp.120-125
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• 2019

In 2017, small, elliptical, brownish purple spots on spears and ferns of asparagus were found in fields of Gangwon-do. The isolated fungal species was identified as an ascomycete Stemphylium vesicarium based on morphological characteristics and molecular phylogenic analyses including nucleotide sequences of the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and cytochrome b (cytb). A pathogenicity test revealed that S. vesicarium was the causal agent of purple spot disease on asparagus. The occurrence of purple spots caused by S. vesicarium on asparagus is the first report in Korea.

• 한국균학회지
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• 제49권3호
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• pp.417-423
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• 2021

Apple decline symptoms were frequently observed on cv. Fuji apple orchards located in Gyeonggi, Gyeongbuk, and Gangwon provinces during surveys conducted from May until the end of September 2020. Three fungal strains were isolated from the margins of internal lesions of diseased apple trees, and their morphological characteristics were considered similar to Botryosphaeria sinensis. Phylogenetic analysis using internal transcribed spacer (ITS) regions, translation elongation factor 1-alpha (tef1), beta-tubulin (tub2), and the second largest subunit of RNA polymerase II (rpb2) gene sequences confirmed the closest relationship of isolates with B. sinensis at the species level. According to a pathogenicity test, the appearance of dark-brown discolorations and vascular necrosis on apple branches inoculated with the isolated strain KNUF-20-014 was observed. To the best of our knowledge, this is the first report of B. sinensis as the causal agent of apple disease in Korea.

• Weed & Turfgrass Science
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• 제7권3호
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• pp.269-274
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• 2018

2017년 4월 중순 경남 양산에 소재한 골프장에서 Laetisariafuciformis에 의한 redthread 병징이 켄터키블루그래스에 발생하였다. 골프코스의 페어웨이에 불규칙한 모양의 병반 형태로 발생하였다. 감염된 잎은 마름증상을 보이면서 점차 볏짚색으로 변했으며, 잎의 끝부분은 실모양으로 헝클어져있었다. 이른 아침에는 분홍빛을 띤 젤라틴 형태로된 사슴뿔 모양의 균핵을 형성하였다. 배양적 특징으로 균총은 옅은 분홍색이었으며 균사다발이 형성되었고 3-5mm 크기의 연한 분홍색 균핵을 형성하였다. 병원균은 형태, 배양적특징 및 분자생물학적 특징을 토대로 L. fuciformis로 동정되었다. 코흐의 원칙에 따라 병원성 검정을 실시하여 켄터키블루그래스에 병원성이 있음을 확인하였다. 이는 한국에서 L. fuciformis에 의해 켄터키블루그래스에 발생하는 redthread에 대한 최초의 보고이다.