• 한국균학회지
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• 제21권4호
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• pp.293-300
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• 1993

Enzyme AAT, GmDH, ME, GPI, LDH 그리고 IDH에 대해 각각 아홉, 일곱. 넷, 아홉, 일곱 그리고 네개의 서로 다른 phenotype이 관찰되었다. Sugarcane field에서 분기한 종명이 밝혀지지 않은 여섯개의 sterile isolate 모두 여섯개의 enzyme에 대해 동일한 위치에 band를 형성하였다. 이 phenotype들은 이미 밝혀진 Pythium species와는 다른 위치에서 band를 형성하였다. 종명이 밝혀지지 않은 Pythium isolate중 isolate 145와 299는 여섯개의 enzyme에 대해서 동일한 위치에서 band가 형성되었고, 다른 isolate들은 다른 위치에서 band를 형성하였다. 다섯개의 Pythium heterothallicum isolate들은 IDH를 제외한 모든 enzyme에 대해서 동일한 위치에서 band를 형성하였다. 두개 그리고 세개의 P. torulosum isolate가 AAT, GmDH 그리고 ME와 GPI,LDH 그리고 IDH 에 대해 각각 동일한 위치에 band를 형성하였다. 한개의 P. spinosum 과 P. irregulare isolate 각각이 enzyme AAT, GmDH 그리고 GPI에 대해 동일한 위치에 band를 형성하였다. 결론적으로, sterile Pythium isolate 들은 intraspecies level에서는 similarity 가 100%였지만, P. heterothallicum 그리고 Pythium spinosum과는 무관함이 밝혀졌고 isolate 306 을 제외한 다른 Pythium species들과는 전반적으로 낮은 상관성을 나타내었다 . 서로 다른 species간의 상관성은 몇몇 경우를 제외하고는 전반적으로 매우 낮았다.

• ALGAE
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• 제30권3호
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• pp.217-222
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• 2015

Pythium species (Pythiales, Oomycetes) are well known as the algal pathogen that causes red rot disease in Pyropia / Porphyra species (Bangiales, Rhodophyta). Accurate species identification of the pathogen is important to finding a scientific solution for the disease and to clarify the host-parasite relationship. In Korea, only Pythium porphyrae has been reported from Pyropia species, with identifications based on culture and genetic analysis of the nuclear internal transcribed spacer (ITS) region. Recent fungal DNA barcoding studies have shown the low taxonomic resolution of the ITS region and suggested the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene as an alternative molecular marker to identify Pythium species. In this study, we applied an analysis of both the ITS and cox1 regions to clarify the taxonomic relationships of Korean Pythium species. From the results, the two closely related Pythium species (P. chondricola and P. porphyrae) showed the same ITS sequence, while the cox1 marker successfully discriminated P. chondricola from P. porphyrae. This is the first report of the presence of P. chondricola from the infected blade of Pyropia yezoensis in Asia. This finding of the algal pathogen provides important information for identifying and determining the distribution of Pythium species. Further studies are also needed to confirm whether P. chondricola and P. porphyrae are coexisting as algal pathogens of Pyropia species in Korea.

• 한국식물병리학회지
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• 제14권2호
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• pp.103-108
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• 1998

A Pythium species was isolated from roots of lisianthus (Eustoma grandiflorum) showing wilt symptoms and reduced growth in a greenhouse at Ichon, Kyonggi-do in 1997. The Pythium species was identified as Pythium spinosum Sawada based on various mycological characteristics. The isolate was strongly pathogenic when inoculated to root of lisianthus plants in pots. The diseased plants showed typical symptoms of root and crown rot, resulting in reduced growth of roots and shoots, and consequently wilting of the above ground part of plants.

• 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.

• ALGAE
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• 제35권1호
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• pp.79-89
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• 2020

Pythium species are ubiquitous organisms known to be pathogens to terrestrial plants and marine algae. While several Pythium species (hereafter, Pythium) are described as pathogens to marine red algae, little is known about the pathogenicity of Pythium on marine green algae. A strain of a Pythium was isolated from a taxonomically unresolved filamentous Ulva collected in an intertidal area of Oslo fjord. Its pathogenicity to a euryhaline Ulva intestinalis collected in the same area was subsequently tested under salinities of 0, 15, and 30 parts per thousand (ppt). The Pythium isolate readily infected U. intestinalis and decimated the filaments at 0 ppt. Mycelium survived on U. intestinalis filaments for at least 2 weeks at 15 and 30 ppt, but the infection did not progress. Sporulation was not observed in the infected algal filaments at any salinity. Conversely, Pythium sporulated on infected grass pieces at 0, 15, and 30 ppt. High salinity retarded sporulation, but did not prevent it. Our Pythium isolate produced filamentous non-inflated sporangia. The sexual stage was never observed and phylogenetic analysis using internal transcribed spacer suggest this isolate belongs to the clade B2. We conclude that the Pythium found in the Oslo fjord was a pathogen of U. intestinalis under low salinity.

• ALGAE
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• 제32권2호
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• pp.155-160
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• 2017

Red rot disease has caused a major decline in Pyropia (Nori) crop production in Korea, Japan, and China. To date, only Pythium porphyrae (Pythiales, Oomycetes) has been reported as the pathogen causing red rot disease in Pyropia yezoensis (Rhodophyta, Bangiales). Recently, Pythium chondricola was isolated from the infected blades of Py. yezoensis during molecular analyses using the mitochondrial cox1 region. In this study, we evaluated the pathogenicity of P. chondricola as an algal pathogen of Py. yezoensis. Moreover, a new cox2 marker was developed with high specificity for Pythium species. Subsequent to re-inoculation, P. chondricola successfully infected Py. yezoensis blades, with the infected regions containing symptoms of red rot disease. A novel cox2 marker successfully isolated the cox2 region of Pythium species from the infected blades of Py. yezoensis collected from Pyropia aquaculture farms. cox2 sequences showed 100% identity with that of P. chondricola (KJ595354) and 98% similarity with that of P. porphyrae (KJ595377). The results of the pathogenicity test and molecular analysis confirm that P. chondricola is a new algal pathogen causing red rot disease in Pyropia species. Moreover, it could also suggest the presence of cryptic biodiversity among Korean Pythium species.

• 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.

• ALGAE
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• 제32권1호
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• pp.29-39
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• 2017

Geographic distributions of pathogens are affected by dynamic processes involving host susceptibility, availability and abundance. An oomycete, Pythium porphyrae, is the causative agent of red rot disease, which plagues Pyropia farms in Korea and Japan almost every year and causes serious economic damage. We isolated an oomycete pathogen infecting Pyropia plicata from a natural population in Wellington, New Zealand. The pathogen was identified as Pythium porphyrae using cytochrome oxidase subunit 1 and internal transcribed spacer of the rDNA cistron molecular markers. Susceptibility test showed that this Pythium from New Zealand was able to infect several different species and genera of Bangiales including Pyropia but is not able to infect their sporophytic (conchocelis) phases. The sequences of the isolated New Zealand strain were also identical to Pythium chondricola from Korea and the type strain from the Netherlands. Genetic species delimitation analyses found no support for separating P. porphyrae from P. chondricola, nor do we find morphological characters to distinguish them. We propose that Pythium chondricola be placed in synonymy with P. porphyrae. It appears that the pathogen of Pyropia, both in aquaculture in the northern hemisphere and in natural populations in the southern hemisphere is one species.

• 한국균학회지
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• 제25권4호통권83호
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• pp.276-290
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• 1997

1990년부터 1996년에 걸쳐 전국 35개 골프장에서 한지형잔디인 creeping bentgrass, Kentucky bluegrass 그리고 난지형잔디인 zoysiagyass의 잎마름 증상으로부터 Pythium spp. 125균주를 분리 하였고, 이를 동정한 결과 P. aphanidermatum, p. arrhenomanes, P. catenulatum, p. gramlnicola, p. myriotylum, P. oligandrum, P. periplocum, P. rostratum, P. torulosum, P. ultimum Trow var. ultimum 그리고 P. vanterpoolii로 모두 11개 종으로 동정되었다. 본 실험에서 사용한 semi-solid 상태의 'sucrose-asparagine bentgrass leaf culture' 방법을 이용할 경우 Pythium spp.의 동정에 필요한 포자낭, 장란기, 장정기 그리고 난포자의 형태적 특징의 관찰이 용이하였다. 동정된 Pythium spp.는 국내에서는 잔디류에 대하여 처음 보고되는 것이고, 이 중에서 P. arrhenomunes, P. cutenulatum, P. graminioota, P. oligandrum, P. periplocum, P. rostratum, P. torulosum 그리고 P. vanterpoolii는 국내에서 처음 보고되는 미기록종이다. P. myriotylum, P. rostratum, P. torulosum, P. vanterpoolii의 경우는 PCA 배지상에서 특이한 균사생장형을 나타내므로 이를 균 동정에 이용할 수 있었다.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.83.1-83
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• 2003

Rice seedling disease is one of major problems in water-seeded rice. This disease is known to be caused by several pathogen such as Pythium, Achlya, and Fusarium species. However, seedling disease of rice in water-seeded rice in Korea is not extensively studied. Pythium species have been isolated from Seosan, Yeoju, Icheon areas using Pythium selective media and their pathogenicity was investigated. All of the Pythium isolates showed strong pathogencity causing seedling emergence reduction in water-seeded rice. Seedling emergence was reduced to 0∼9％ at 10 days after inoculation of 23 Pythium isolates compared to 60％ of noninoculated control in a growth chamber. However, Fusarium species did not cause seedling emergence reduction in water-seeded rice. In contrast, when no water added into water agar or soil, the pathogen caused seedling rot two weeks after planting. These results indicate that Pythium species is a cause of seedling disease in water-seeded cultivation areas in Korea.