• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.493-502
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• 2019

Maize (Zea mays L.) is a C4-plant and one of the three major crops grown worldwide. Because of its high productivity, maize is considered as one of the most important food and feed stocks in the world. Recently, bioethanol from maize was predominantly generated in the USA and Brazil. Infection of maize by several diseases resulted in a huge disaster and prevented maize production. Downy mildew, caused by Peronosclerospora sorghi, is one of the most serious diseases of maize. Despite efforts to develop downy mildew-resistant cultivars or seed treatment with metalaxyl, downy mildew persists as a serious pathogen and is still prevalent in specific geographical locations. Analysis of soils infected with downy mildew and investigation of candidates associated with downy mildew resistance is an attractive method to overcome downy mildew damage in maize. In a previous study, we reported that maize chromosome 6 carries a possible candidate gene for downy mildew resistance. Using bioinformatics tools and RT-PCR analysis, five novel genes including bZIP, OFP transcription factor, and Ppr were identified as candidate genes associated with downy mildew resistance.

• Research in Plant Disease
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• v.27 no.4
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• pp.149-154
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• 2021

Pseudoperonospora cubensis (downy mildew) is highly virulent to various Cucurbitaceae crops, including cucumber (Cucumis sativus). We tested chlorine dioxide application in a plastic greenhouse for environment-friendly control of downy mildew disease. Spraying diluted chlorine dioxide suppressed downy mildew disease with 41.2% control efficacy. Thermal fogging with chlorine dioxide had a high control efficacy of 80.9%, confirming that this approach is useful for environment-friendly downy mildew control. Using thermal fogging to control diseases that are greatly affected by humidity, such as downy mildew, may be more effective compared with conventional dilution spray control methods.

• Korean Journal of Organic Agriculture
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• v.24 no.4
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• pp.919-929
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• 2016

This study investigated the effect of organic materials (Bordeaux, Loess-sulfur) and the removal of apical shoot against downy mildew disease on cucumber cultivated in greenhouse. Five kinds of Bordeaux were made by adjusting mixing ratio of lime and copper sulfate in order to elucidate the optimal combination. The 4-6type Bordeaux was selected as the most effective combination for controlling cucumber downy mildew. Loess-sulfur showed inhibitory activity against cucumber downey mildew, but it was less effective than Bordeaux. It was confirmed that apical shoot cutting could reduce the incidence of cucumber downy mildew disease by 56.3%. When apical shoots of susceptible cucumber variety were cut at different leaf stages, disease incidence by early apical shoot cutting treatment was lower than that of late apical shoot cutting treatment. However in a resistant variety, 'Heukryungsamcheok', disease incidences of all cucumber apical shoot cutting treatments were lower than that of non-cutting treatment, but there was no differences between apical shoot cutting treatments due to low disease incidences. In addition, when organic materials and apical shoot cutting treatment were carried out in parallel, the combined treatments of organic materials and apical shoot cutting showed low disease incidence of cucumber downy mildew compared to untreated control. The lowest disease incidence of cucumber downy mildew was recorded in the combined treatment of 4-6type Bordeaux and apical shoot cutting. This study confirmed that apical shoot cutting can reduce the disease incidence of cucumber downy mildew and the combined treatment of apical shoot cutting and organic materials showed higher suppressive effect against cucumber downy mildew.

• The Plant Pathology Journal
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• v.18 no.3
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• pp.147-151
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• 2002

Seven fungicides were compared for the control of downy mildew on midge gourd. All treatments had significantly lower rates of disease progress curves and disease severity levels than that of the control. The highest yields were obtained from crops treated with metalaxyl + mancozeb, fosetyl-Al, and chlorothalonil. These treatments also proved to be the most economical considering the treatment costs.

• The Korean Journal of Mycology
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• v.46 no.4
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• pp.505-510
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• 2018

Peronospora is the largest genus of the order Peronosporales (Oomycota) and contains more than 550 accepted species, which causes downy mildew on many economically important crops. During a survey of downy mildew flora in Korea, a previously unreported species of Peronospora has been found on Corydalis ambigua. Based on molecular phylogenetic and morphological analyses, the causal agent was identified as Peronospora bulbocapni. This is the first report of Peronospora bulbocapni occurring on Corydalis ambigua in Korea.

• The Korean Journal of Mycology
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• v.46 no.3
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• pp.235-239
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• 2018

Basil (Ocimum spp.) is a popular herb grown worldwide. During the past fifteen years, a downy mildew pathogen has caused considerable damage to basil cultivations. In August 2017, downy mildew disease symptoms were found on Basil Tree (or long foot Basil Tree), which was developed by the grafting of two basil varieties and is a continuous harvest plant with a woody trunk. The present study reports the occurrence of downy mildew disease in basil Tree and identifies the causal pathogen, as Peronospora belbahrii.

• Research in Plant Disease
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• v.25 no.2
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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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• v.49 no.2
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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.

• Research in Plant Disease
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• v.9 no.1
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• pp.52-56
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• 2003

It was conducted to investigate the effect of rice downy mildew (RDM) infection to plant growth and yield components in water seeding stage, and to screen of varietal resistance to downy mildew. Being infected by rice downy mildew, chlorotic spot appeared in the leaf and leaf length was shortened. As the infected rice was growing, internode was not elongated properly and was deformed, and then panicle was not arised or mal-formed. Plant height of infected rice was shortened at all growth stage, and while the number of tillers of infected rice was more decreased than that of healthy plant before maximum tillering stage, and that of infected rice was more increased after heading stage. While the number of internode of infected tiller was much increased than that of healthy tiller internode length of infected tiller was shorter. As the rice infected by RDM severely, the number of panicles per square meter and ripening of rice was more decreased and yield of rice was extremely much decreased. As result of the varietal resistance screening with rice seedling, Geyh-wabyeo and Donjinbyeo were resistant varieties to downy mildew.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.1
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• pp.41-49
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• 2016

This study was conducted to evaluate maize downy mildew resistance using spreader row technique in Cambodia. A total of forty maize lines were used in this experiment. Seven Korean varieties and seven breeding lines showed high infection rates (80~100%) and highly susceptible (HS) to downy mildew disease in both spring and fall. Also most of nested association mapping (NAM) parent lines were highly susceptible (HS). Meanwhile three inbred lines, Ki3, Ki11, and CML228, showed highly resistant (HR) or resistant (R) in spring and moderately resistant (MR) in fall. These three lines were already known as resistant inbred lines against downy mildew disease. It appears that spreader row technique was suitable for selection of maize downy mildew resistance in Cambodia. The incidence of downy mildew was influenced by weather conditions, especially relative humidity and temperature. Among several inoculation methods to screen for downy mildew resistance, this spreader row technique is effectively and easily used in the field of Southeast Asia.