• The Korean Journal of Mycology
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• v.21 no.4
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• pp.293-300
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• 1993

For the enzymes AAT, GmDH, ME, GPI, LDH and IDH, nine, seven, four, nine, seven, and four different phenotypes, respectively, were observed. All six isolates of an unidentified sterile Pythium sp. isolated from field soil showed the same band positions for all six enzymes compared. These phenotypes were not similar to any of the known Pythium species. Two isolates of unknown Pythium species (145 and 299) showed the same band positions for all six enzymes. The phenotypes for all three unknown Pythium spp. were different from the other species in the experiment. Five isolates of P. heterothallicum showed the same band positions for all enzymes compared except one enzyme, lDH. Two isolates of P. torulosum showed the same band petitions for enzymes AAT, GmDH and ME, and three isolates of P. totulosum showed the same positions for enzymes GPI, LDH, and IDH. Single isolates of P. spinosum and P. irregulare showed the same band positions for enzymes AAT, GmDH and GPI. In conclusion, sterile types of Pythium species showed 100% similarities among themselves but did not show any similarity with all isolates of P. heterothallicum and P. spinosum isolate, and showed very low similarities with other isolates in general except with unknown Pythium isolate 306. Similarity levels between different species were low in general with few exceptions.

• ALGAE
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• v.30 no.3
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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.

• Korean Journal Plant Pathology
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• v.14 no.2
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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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• v.47 no.3
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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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• v.35 no.1
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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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• v.32 no.2
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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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• v.35 no.2
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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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• v.32 no.1
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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.

• The Korean Journal of Mycology
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• v.25 no.4 s.83
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• pp.276-290
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• 1997

Eleven species of Pythium were identified from 125 isolates collected from leaf blight lesions on creeping bentgrass (Agrostis palustris Huds.), Kentucky bluegrass (Poa pratensis L.), and zoysiagrasses (Zoysia japonica Steud., and Z. matrella (L.) Merr.) at 35 golf courses in Korea in $1990{\sim}1996$. The identified species included P. aphanidermatum, P. arrhenomanes, P. catenulatum, P. graminicola, P. myriotylum, P. oligandrum, P. periplocum, P. rostratum, P. torulosum, P. ultimum var. ultimum, and P. vanterpoolii. Mycological characteristics of sporangia, oogonia, antheridia, and oospores observed on the sucrose-asparagine bentgrass leaf culture medium were described for each species. Of the species, P. arrhenomanes, P. catenulatum, P. gmminicola, P. oligandrum, P. periplocum, P. rostratum, P. torulosum and P. vanterpoolii were reported for the first time in Korea. P. myriotylum, P. rostratum, P. torulosum and P. vanterpoolii showed characteristic colony patterns on the potato-carrot agar medium, which can be used as criteria for species identification of Pythium.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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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.