• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 1999.10a
• /
• pp.31.2-31
• /
• 1999

• Korean Journal Plant Pathology
• /
• v.3 no.1
• /
• pp.17-19
• /
• 1987

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2022.04a
• /
• pp.97-97
• /
• 2022

• 한국균학회소식:학술대회논문집
• /
• 2015.11a
• /
• pp.41-41
• /
• 2015

Oomycetes belong to the kingdom Straminipila, a remarkably diverse group which includes brown algae and planktonic diatoms, although they have previously been classified under the kingdom Fungi. These organisms have evolved both saprophytic and pathogenic lifestyles, and more than 60% of the known species are pathogens on plants, the majority of which are classified into the order Peronosporales (includes downy mildews, Phytophthora, and Pythium). Recent phylogenetic investigations based on DNA sequences have revealed that the diversity of oomycetes has been largely underestimated. Although morphology is the most valuable criterion for their identification and diversity, morphological species identification is time-consuming and in some groups very difficult, especially for non-taxonomists. DNA barcoding is a fast and reliable tool for identification of species, enabling us to unravel the diversity and distribution of oomycetes. Accurate species determination of plant pathogens is a prerequisite for their control and quarantine, and further for assessing their potential threat to crops. The mitochondrial cox2 gene has been widely used for identification, taxonomy and phylogeny of various oomycete groups. However, recently the cox1 gene was proposed as a DNA barcode marker instead, together with ITS rDNA. To determine which out of cox1 or cox2 is best suited as universal oomycete barcode, we compared these two genes in terms of (1) PCR efficiency for 31 representative genera, as well as for historic herbarium specimens, and (2) in terms of sequence polymorphism, intra- and interspecific divergence. The primer sets for cox2 successfully amplified all oomycete genera tested, while cox1 failed to amplify three genera. In addition, cox2 exhibited higher PCR efficiency for historic herbarium specimens, providing easier access to barcoding type material. In addition, cox2 yielded higher species identification success, with higher interspecific and lower intraspecific divergences than cox1. Therefore, cox2 is suggested as a partner DNA barcode along with ITS rDNA instead of cox1. Including the two barcoding markers, ITS rDNA and cox2 mtDNA, the multi-locus phylogenetic analyses were performed to resolve two complex clades, Bremia lactucae (lettuce downy mildew) and Peronospora effuse (spinach downy mildew) at the species level and to infer evolutionary relationships within them. The approaches discriminated all currently accepted species and revealed several previously unrecognized lineages, which are specific to a host genus or species. The sequence polymorphisms were useful to develop a real-time quantitative PCR (qPCR) assay for detection of airborne inoculum of B. lactucae and P. effusa. Specificity tests revealed that the qPCR assay is specific for detection of each species. This assay is sensitive, enabling detection of very low levels of inoculum that may be present in the field. Early detection of the pathogen, coupled with knowledge of other factors that favor downy mildew outbreaks, may enable disease forecasting for judicious timing of fungicide applications.

• The Plant Pathology Journal
• /
• v.18 no.2
• /
• pp.77-80
• /
• 2002

A simple method for sporangial formation of the rice downy mildew pathogen, Sclerophthora macrospora, on infected leaf tissues was developed to facilitate diagnosis of the disease. Freshly infected young leaves showing whitish to yellowish small spots were selected and cut into small pieces about 2-3 cm in length. About 10-20 pieces were surface sterilized in a 100 ml Duran bottle with 40 ml of 70% ethanol by vigorous shaking for 30 seconds. After washing three times with distilled water, the leaf cuts were submerged in 10 ml of Millipore-filtered paddy water and incubated at $20^{\circ}C$ in the dark. After 8-10 h of incubation, the bottle was vigorously agitated on a vortex mixer, Aliquot amount of the suspension, 0.1-1.0 m1, was spread on a slide glass and examined under a light microscope at 50 or 100x magnification. It was found that light and 1% NaClO strongly inhibit sporangial formation of S. macrospora. Meanwhile, the use of freshly infected young loaves and washing with 70% ethanol stimulated sporangial formation of the fungus on rice leaves.

• Mycobiology
• /
• v.45 no.3
• /
• pp.139-149
• /
• 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.

• The Korean Journal of Pesticide Science
• /
• v.4 no.1
• /
• pp.64-70
• /
• 2000

Control effects of phosphorous acid were investigated on three diseases. For Phytophthora blight of red pepper, protective and curative effects of phosphorous acid at the concentration of $1,408{\mu}g$ a. i./mL were 91.0% and 80.0%, respectively. In case of late blight of tomato, caused by Phytophthora infestans, protective and curative effects were 63.4% and 13.0% at the same concentration, respectively. However, the protective and curative effects of phosphorous acid increased by decreasing inoculum density of Phytophthora infestans. The protective effects of phosphorous acid on control of Phytophthora blight of red pepper was persisted for 4 days with high control efficacy (94.0%). The protective and curative effects of phosphorous acid ($1,408{\mu}g$ a. i./mL) on cucumber downy mildew were 82.0% and 62.0% respectively. The foliar application of phosphorous acid also promoted shoot growth and fresh weight of red pepper.

• The Korean Journal of Mycology
• /
• v.45 no.4
• /
• pp.386-393
• /
• 2017

Onion downy mildew, caused by Peronospora destructor, is a major disease in onion cultivation areas in Korea. The causal fungi were collected and analyzed based on sequence similarity and molecular phylogenetic relationships of multi-gene sequences, including the internal transcribed spacer (ITS) region. All isolates from Changnyeong-gun, Hamyang-gun, and Hapcheon-gun in Gyeongnam province, and Muan-gun, Haenam-gun, and Sinan-gun in Jeonnam province were identical in the four types of gene sequences, indicating they were genetically the same strains. In this study, a PCR method was developed based on the ITS gene sequences to amplify the specific DNA fragment for P. destructor only. The detection limit of was total genomic DNA of the P. destructor and the plant $0.7ng/{\mu}L$. Therefore, the developed PCR method could be used to detect P. destructor effectively from symptomless onion leaves.

• Korean journal of applied entomology
• /
• v.3
• /
• pp.11-14
• /
• 1964

This experiment was compared Bordeaux mixture, which used to as good fungicide up to date, with new 6 fungicides for control of powdery mildew on onion from 1963 to 1864 in Pusan. In resulting treated blocks was better effect than untreated block, and specially Difolatan and Dithane M 45 was best. Dithane M 22, Dithane Z 78 and Orthocide was moderate but Sankinon and Bordeaux mixture was lower effect than formers.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 1999.10a
• /
• pp.28.1-28
• /
• 1999