• The Korean Journal of Mycology
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• v.41 no.4
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• pp.261-267
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• 2013

In order to select antagonists for biological control of downy mildew of cucumber, 126 bacteria were isolated from cucumber plants collected from several locations in Korea. Among them, Five isolates were selected as potential biocontrol agents of cucumber downy mildew using a leaf disc bioassay method. In preventive and curative effect tests, the isolate CC110 was found to be effective to control downy mildew on cucumber showing diseased area by 0% whereas that of control was 15.0~18.0%. A bacterium isolate CC110 was identified as Bacillus amyloliquefaciens subsp. plantarum based on phylogenetic analysis using gyrB gene sequence. The culture liquid of isolate CC110 in TSB media were more effective for the control of the disease than those cultured in LB, NB, and KB media in leaf disk bioassay. when undiluted liquid, two-fold, five-fold diluted culture broth, and undiluted liquid, two-fold, five-fold diluted filtrate of isolate CC110 in TSB media were treated, diseased area of cucumber powdery mildew were 0%, 3.0%, 8.0%, 0%, 4.0% and 7.0%, respectively, whereas diseased area in the control was 21.0%. In the cucumber seedling tests, when the culture broth of isolate CC110 in TSB media was treated, diseased area were 35.0%, whereas that of control was 82.0%. When B. amyloliquefaciens CC110 was treated four times at five-day interval in the vinylhouse test, the control effect of cucumber downy mildew was higher than that treated three at seven-day interval.

• Mycobiology
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• v.48 no.4
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• pp.304-312
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• 2020

Over the past 15 years, downy mildew became the most destructive foliar disease in cultivated Impatiens species (Balsaminaceae) worldwide. A previous study had revealed that the causal agent was not Plasmopara obducens (Oomycota, Peronosporales) but Plasmopara destructor on Impatiens walleriana, and Plasmopara velutina on Impatiens balsamina. This hints to a relatively high degree of specialization of Plasmopara on Balsaminaceae. Therefore, it was the aim of the present study to perform multigene phylogenetic analysis and detailed morphological investigation for several Korean downy mildew samples parasitic to cultivated I. walleriana, and I. balsamina, but also to a northeast Asian wild plant, Impatiens textori. It was revealed that I. textori harbors a new species, which is introduced and described here as Plasmopara elegantissima.

• Mycobiology
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• v.46 no.4
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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.

• Applied Biological Chemistry
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• v.44 no.2
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• pp.109-115
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• 2001

The foliar uptake of dimethomoiph induced by several nonionic surfactants was measured in order to study the correlations between the uptake rate of dimethomorph and the fungicidal activity to cucumber downy mildew. Dimethomorph was not absorbed in cucumber leaf in the absence of activator surfactant. And the curative effect of dimethomoiph WP to cucumber downy mildew was very low under the concentration of 250 ${\mu}g/ml$. But dimethomorph uptake was remarkably enhanced by addition of nonionic surfactants, such as polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. And the curative effect to cucumber downy mildew was enhanced with proportion to uptake rate of dimethomorph. The protective effect to cucumber downy mildew, however, tends to decrease with the increase of foliar uptake of dimethomorph. The uptake rate of dimethomorph to cucumber leaf was proportional to the content of polyoxyethylene cetyl ether in formulation, but was decreased with dilution.

• Research in Plant Disease
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• v.22 no.3
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• pp.208-212
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• 2016

During the nursery seedlings stage at Muan in 2013, moisture and temperature conditions were favorable for the occurrence of onion downy mildew. Several fungicides were evaluated for controlling onion downy mildew at the stage of seedling. The disease incidence of the untreated control was 51.1%, which was sufficient to evaluate the fungicide efficacy for the control of onion downy mildew. Incidence at the mancozeb treatment (MAN treatment) was 4.4% and it was the highest control value of 91.4%. Incidence at the various fungicides treatment (MIX treatment) consisted of amectotradin plus dimethomorph, floupicolide plus propamocarb HCl, or dimethomorph plus pyraclostrobin was 10.0%, and the control value of the MIX treatment was 80.4%. Among the tested fungicides, amectotradin plus dimethomorph (AME plus DIM treatment) was selected and treated. Incidence of AME plus DIM treatment was 12.2%. There was statistically significant difference among the three different treatments and the untreated control. These results suggest that the application of fungicides on onion nursery seedlings was effective to control the onion downy mildew.

• The Korean Journal of Mycology
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• v.49 no.3
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• pp.379-383
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• 2021

Lactuca serriola L. (syn. L. scariola L.), commonly known as prickly lettuce, invaded Korea in the late 1970s. The plant has since become widely naturalized and disruptive to native plant communities. In May 2020, downy mildew infections were observed on L. serriola in Gimje-si, Korea. Molecular phylogenetic and morphological analyses identified the causal agent as Bremia lactucae. This is the first report of B. lactucae infection on L. serriola in Korea.

• The Korean Journal of Pesticide Science
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• v.15 no.3
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• pp.323-328
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• 2011

Control efficacies of mixing of powdery mildew biofungicides with other control agents against major or fungal diseases of cucumber were investigated. Control efficacies against cucumber powdery mildew were quite different according to the kinds of biofungicides applied but those of powdery mildew biofungicides were increased by mixing application of two biofungicides. More than 80% of control efficacies on powdery and downy mildews of cucumber were obtained by mixing application of a powdery mildew biofungicide Bacillus subtilis KB-401 and a downy mildew chemical fungicide dimethomorph. Similarly, control efficacies on powdery and downy mildews of cucumber were 95% and 70% by mixing application of a powdery mildew biofungicide Bacillus subtilis KB-401 and cooking oils and yolk mixture, respectively.

• Agrochemical news magazine
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• v.25 no.2 s.195
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• pp.41-43
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• 2004

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.113-113
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• 2017

Downy mildew (DM), caused by several species in the Peronosclerospora and Scleropthora genera, is a major maize (Zea mays L.) disease in tropical or subtropical regions. DM is an obligate parasite species in the higher plants and spreads by oospores, wind, and mycelium in seed surface, soil, and living hosts. Owing to its geographical distribution and destructive yield reduction, DM is one of the most severe maize diseases among the maize pathogens. Positional cloning in combination with phenotyping is a general approach to identify disease resistant gene candidates in plants; however, it requires several time-consuming steps including population or fine mapping. Therefore, in the present study, we suggest a new combination strategy to improve the identification of disease resistant gene candidates. Downy mildew (DM) resistant maize was selected from five cultivars using the spreader row technique. Positional cloning and bioinformatics tools identified the DM resistant QTL marker (bnlg1702) and 47 protein coding genes annotations. Eventually, 5 DM resistant gene candidates, including bZIP34, Bak1, and Ppr, were identified by quantitative RT-PCR without fine mapping of the bnlg1702 locus. Specifically, we provided DM resistant gene candidates with our new strategy, including field selection by the spreader row technique without population preparation, the DM resistance region identification by positional cloning using bioinformatics tools, and expression level profiling by quantitative RT-PCR without fine mapping. As whole genome information is available for other crops, we propose applying our novel protocol to other crops or for other diseases with suitable adjustment.

• Weed & Turfgrass Science
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• v.5 no.1
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• pp.23-28
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• 2016

Zoysiagrass possessing the leaf yellowing with excessive tillers was first found in a golf course in Gyunggi province at last three to four years ago and since then have rapidly spread many golf courses in Korea. The symptom is very similar to that of yellow tuft or downy mildew, which is caused by Sclerophthora macrospora, on cool-season turfgrasses including Kentucky bluegrass and ryegrass. Microscopic study was firstly carried out to look over the presence of the pathogen in the infected leaf and stem tissues. Oospores and sporangia, reported as typical indicators of downy mildew, were obviously observed from the infected leaves. Using a set of primers based on the 18S ribosomal DNA from S. macrospora, the specific DNA fragment corresponding the gene was amplified. This study reveals that S. macrospora might be involved in spread of leaf yellowing of zoysiagrass with excessive tillers.