• 한국균학회지
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• 제45권2호
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• pp.160-166
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• 2017

The genus Pseudoperonospora (Peronosporales, Oomycota) comprises six accepted species, including Ps. cubensis, which causes downy mildew on many economically important cucurbitaceous crops, and Ps. humuli, which occurs on hops. During a survey of downy mildew flora in Korea, a previously unreported species of Pseudoperonospora was found on Urtica angustifolia. Based on molecular phylogenetic and morphological analyses, the causal agent was identified as Pseudoperonospora urticae. This is the first report of Pseudoperonospora urticae occurring on Urtica angustifolia in Korea.

• Mycobiology
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• 제47권3호
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• pp.261-272
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• 2019

Oomycetes are widely distributed in various environments, including desert and polar regions. Depending upon different habits and hosts, they have evolved with both saprophytic and pathogenic nutritional modes. Freshwater ecosystem is one of the most important habitats for members of oomycetes. Most studies on oomycete diversity, however, have been biased mostly towards terrestrial phytopathogenic species, rather than aquatic species, although their roles as saprophytes and parasites are essential for freshwater ecosystems. In this study, we isolated oomycete strains from soil sediment, algae, and decaying plant debris in freshwater streams of Korea. The strains were identified based on cultural and morphological characteristics, as well as molecular phylogenetic analyses of ITS rDNA, cox1, and cox2 mtDNA sequences. As a result, we discovered eight oomycete species previously unknown in Korea, namely Phytopythium chamaehyphon, Phytopythium litorale, Phytopythium vexans, Pythium diclinum, Pythium heterothallicum, Pythium inflatum, Pythium intermedium, and Pythium oopapillum. Diversity and ecology of freshwater oomycetes in Korea are poorly understood. This study could contribute to understand their distribution and ecological function in freshwater ecosystem.

• 식물병연구
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• 제25권2호
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• pp.98-101
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• 2019

Pak choi (or a Bok choy; Brassica rapa subsp. chinensis) is a popular brassicaceous vegetable worldwide. In January 2019, a downy mildew symptom on pak choi was found at a farm located in Yongin, Korea. Based on morphological characteristics and molecular phylogenetic inference, the pathogenic oomycete was identified as Hyaloperonospora brassicae. To our knowledge, this is the first report of downy mildew disease occurring on pak choi in Korea. Considering the increasing demand for this crop, this pathogen would be a potentially new threat to the cultivation of pak choi in Korea.

• Mycobiology
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• 제46권4호
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• pp.416-420
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• 2018

Crepidiastrum sonchifolium, a flowering plant in the daisy family (Asteraceae), is native to East Asia. In Korea, this plant is a locally cultivated vegetable, and its market size is gradually growing. Since the plants with downy mildew infection were initially found at a private farm of Chuncheon city, the occurrences have continued in commercial farms of other regions, highlighting that this disease is spreading throughout Korea. The pathogen was attributed to a member of the genus Bremia that contains many specialized species, each of which displays a narrow host spectrum on Asteraceae. Based on morphological and molecular phylogenetic analyses, along with the high host specificity recently proven for Bremia species, the identity of the causal agent was confirmed as a so far undescribed species of Bremia. Here, we introduce Bremia itoana sp. nov., specific to C. sonchifolium.

• Mycobiology
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• 제49권2호
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• pp.188-195
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• 2021

The genus Pseudoperonospora, an obligate biotrophic group of Oomycota, causes the most destructive foliar downy mildew disease on many economically important crops and wild plants. A previously unreported disease by Pseudoperonospora was found on oriental pickling melon (Cucumis melo var. conomon) in Korea, which is a minor crop cultivated in the temperate climate zone of East Asia, including China, Korea, and Japan. Based on molecular phylogenetic and morphological analyses, the causal agent was identified as Pseudoperonospora cubensis, and its pathogenicity has been proven. Importantly, two phylogenetic clades of P. cubensis, harboring probably two distinct species, were detected within the same plots, suggesting simultaneous coexistence of the two clades. This is the first report of P. cubensis causing downy mildew on oriental pickling melon in Korea, and the confirmation of presence of two phylogenetic clades of this pathogen in Korea. Given the high incidence of P. cubensis and high susceptibility of oriental pickling melon to this disease, phytosanitary measures, including rapid diagnosis and effective control management, are urgently required.

• Mycobiology
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• 제51권5호
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• pp.333-342
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• 2023

Phytophthora species, classified under Oomycota, cause significant damage to various crops and trees. The present study introduced Phytophthora species, P. nagaii and P. tentaculata, new to Korea, which pose notable risks to their respective host plants. Our research provided a comprehensive description of these species taking into account their cultural features, morphological characteristics, and molecular phylogenetic analysis using the internal transcribed spacer rDNA region and cytochrome c oxidase subunit mtDNA genes (cox1 and cox2) sequences. In addition, this study first evaluated the sensitivity of P. nagaii and P. tentaculata to five anti-oomycete fungicides, finding both species most responsive to picarbutrazox and P. tentaculata resistant to fluazinam. The data can guide targeted treatment strategies and offer insights into effective control methods. The findings expand our understanding of the diversity, distribution, and management of Phytophthora species in Korea.

• Mycobiology
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• 제42권3호
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• pp.241-248
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• 2014

NADPH oxidases (Noxes), transmembrane proteins found in most eukaryotic species, generate reactive oxygen species and are thereby involved in essential biological processes. However, the fact that genes encoding ferric reductases and ferric-chelate reductases share high sequence similarities and domains with Nox genes represents a challenge for bioinformatic approaches used to identify Nox-encoding genes. Further, most studies on fungal Nox genes have focused mainly on functionality, rather than sequence properties, and consequently clear differentiation among the various Nox isoforms has not been achieved. We conducted an extensive sequence analysis to identify putative Nox genes among 34 eukaryotes, including 28 fungal genomes and one Oomycota genome. Analyses were performed with respect to phylogeny, transmembrane helices, di-histidine distance and glycosylation. Our analyses indicate that the sequence properties of fungal Nox genes are different from those of human and plant Nox genes, thus providing novel insight that will enable more accurate identification and characterization of fungal Nox genes.

• ALGAE
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• 제35권2호
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• pp.133-144
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• 2020

Pythium porphyrae is responsible for devastating outbreaks in seaweed farms of Pyropia, the most valuable cultivated seaweed worldwide. While the genus Pythium contains many well studied pathogens, the genome of P. porphyrae has yet to be sequenced. Here we report the first available gene repertoire of P. porphyrae and a preliminary analysis of pathogenicity-related genes. Using ab initio detection strategies, similarity based and manual annotation, we found that the P. porphyrae gene repertoire is similar to classical phytopathogenic Pythium species. This includes the absence of expanded RxLR effector family and the detection of classical pathogenicity-related genes like crinklers, glycoside hydrolases, cellulose-binding elicitor lectin-like proteins and elicitins. We additionally compared this dataset to the proteomes of 8 selected Pythium species. While 34% of the predicted proteome appeared specific to P. porphyrae, we could not attribute specific enzymes to the degradation of red algal biomass. Conversely, we detected several cellulases and a cutinase conserved with plant-pathogenic Pythium species. Together with the recent report of P. porphyrae triggering disease symptoms on several plant species in lab-controlled conditions, our findings add weight to the hypothesis that P. porphyrae is a reformed plant pathogen.

• The Plant Pathology Journal
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• 제23권4호
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• pp.287-294
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• 2007

Endophytic fungi were isolated from surface sterilized root tissues of Aralia elata and Aralia continentalis, collected from farmer's field in Chungnam province, Republic of Korea, in 2005. Based on ITS sequence analysis, 24 fungal genera were characterized from 359 isolates, belonging to 22 Ascomycota, 1 Glomeromycota and 1 Oomycota. Strumella, Rhizopycnis and Entrophospora in A. elata and Rhizopycnis and Leptosphaeria in A. continentalis were the most abundant taxa. Out of 24 genera, Entrophospora, Leptodontidium, Neoplaconema, Paraconiothyrium, Rhizopycnis, Strumella and Tumularia were new to Korea. A total of 110 isolates were tested for antifungal activities against six plant pathogenic fungi. Out of these, 39 isolates showed antifungal activity against at least one plant pathogenic fungi. Four isolates of Pyrenochaeta, 1 isolate of Entrophospora and 1 unidentified fungus strongly inhibited the growth of six plant pathogenic fungi.

• Mycobiology
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• 제45권3호
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• pp.139-149
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• 2017

The genus Hyaloperonospora (Peronosporaceae; Oomycota) is an obligate biotrophic group that causes downy mildew disease on the Brassicaceae and allied families of Brassicales, including many economically relevant crops, such as broccoli, cabbage, radish, rape, and wasabi. To investigate the diversity of Hyaloperonospora species in northeast Asia, we performed a morphological analysis for the dried herbarium specimens collected in Korea, along with molecular phylogenetic inferences based on internal transcribed spacer rDNA and cox2 mtDNA sequences. It was confirmed that 14 species of Hyaloperonospora exist in Korea. Of these, three species, previously classified under the genus Peronospora, were combined to Hyaloperonospora: H. arabidis-glabrae comb. nov. (ex Arabis glabra), H. nasturtii-montani comb. nov. (ex Rorippa indica), and H. nasturtii-palustris comb. nov. (ex Rorippa palustris). In addition, finding two potentially new species specific to northeast Asian plants is noteworthy in support of the view that the species abundance of Hyaloperonospora has been underestimated hitherto.