• 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.

• Research in Plant Disease
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• v.17 no.3
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• pp.358-363
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• 2011

Dapple fruits of plum cv. Oiishiwase (Prunus salicina L.) were occurred at Gyeonggi-do and Gyeongsangbukdo. The symptoms resembled the dapple fruit disease caused by Hop stunt viroid (HSVd). To identify the causal disease agents, RT-PCR was performed with the specific primers of HSVd. RT-PCR analysis showed that HSVd variants (DP1, DP2) were detected from dapple fruits. HSVd detection was also confirmed by the dot blot hybridization using a DIG-probe specific to HSVd. Nucleotide sequences of DP1 and DP2 had the identities of 94-100% with those of other 7 variants of HSVd in Genbank database. DP1 and DP2 were different in two nucleotides of CG and AA at position of 59 and 60, orderly. Based on nucleotide sequences at position of 59 and 60, HSVd variants associated with plum dapple fruits could be divided mainly into three groups as CG, AA and TG.

• Korean Journal of Medicinal Crop Science
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• v.10 no.3
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• pp.155-161
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• 2002

Using semi-selective (SS-) and selective (Jee-) medium, we identified the pathogens isolated from the symptomatic plants and soils collected from different locations, such as Suwon, Andong, and Youngju, as P. drechsleri, which is Phytophthora root rot causal agent of A. macrocephala. At $25^{\circ}C$, these isolates were grown faster on 10% V8A (V8 juice agar) medium than on PDA (potato dextrose agar) with hyphal swelling, but no growing was observed at below $5^{\circ}C$ and over $40^{\circ}C$. In order to identify the pathogenicity of each isolate, seedlings of A. macrocephala were inoculated with mycelium -zoospore suspended inoculum, which was prepared by culturing on 10% V8A medium and homogenizing in distilled water. By this method, wide ranges of pathogenicity were observed as follows; $5.0%{\sim}26.4%$ of disease severities concerning the lesion areas of the top plants and $23.5%{\sim}72.2%$ of disease incidences. Therefore, this was considered as a efficient method to identify the pathogenicity of P. drechsleri in large scale screening. P-A200073, isolated from soils in Andong, and P-9755, from the root of symptomatic plant of A. macrocephala in Suwon, showed the highest degree of pathogenicity to the seedlings. By these isolates, lesion areas and disease incidences of the inoculated seedlings were occurred $26.4%{\sim}63.2%$ and $25.1%{\sim}72.2%$, respectively. However, no symptoms were observed in uninoculated control. Same pathogens were reisolated from roots and lower stems of the inoculated plants, but not from leaves.

• Journal of Plant Biotechnology
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• v.43 no.3
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• pp.317-331
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• 2016

Development of disease resistant plant is one of the important objectives in rice breeding programs because biotic stresses can adversely affect rice growth and yield losses. This study was conducted to identify lines with multiple-resistance genes to biotic stress among 173 hybrid rice breeding lines and germplasms using DNA-based markers. Our results showed that one hybrid rice line [IR98161-2-1-1-k1-3 (IR86409-3-1-1-1-1-1/IRBB66)] possessed 5 bacterial blight resistance genes (Xa4, xa5, Xa7, Xa13 and Xa21) while two hybrid rice lines [IR98161-2-1-1-k1-2 (IR86409-3-1-1-1-1-1/IRBB66) and 7292s (IR75589-31-27-8-33S(S1)/IR102758B)] possessed 3 bacterial blight resistance genes (Xa4, Xa7 and Xa21, and Xa3, Xa4 and xa5). Molecular survey on rice blast disease revealed that most of these lines had two different resistant genes. Only 11 lines possessed Pib, Pi-5, and Pi-ta. In addition, we further surveyed the distribution of insect resistant genes, such as Bph1, Bph18(t), and Wbph. Three hybrid breeding lines [IR98161-2-1-1-k1-3 (IR86409-3-1-1-1-1-1/IRBB66), IR98161-2-1-1-k1-2 (IR86409-3-1-1-1-1-1/IRBB66), and 7292s (IR75589-31-27-8-33S(S1) /IR102758B)] contained all three resistance genes. Finally, we obtained four hybrid rice breeding lines and germplasms [IR98161-2-1-1-k1-2 (IR86409-3-1-1-1-1-1/IRBB66), Damm-Noeub Khmau, 7290s, and 7292s (IR75589-31-27-8-33S(S1)/IR102758B)] possessing six-gene combination. They are expected to provide higher level of multiple resistance to biotic stress. This study is important for genotyping hybrid rice with resistance to diverse diseases and pests. Results obtained in this study suggest that identification of pyramided resistance genes is very important for screening hybrid rice breeding lines and germplasms accurately for disease and pest resistance. We will expand their cultivation safely through bioassays against diseases, pests, and disaster in its main export countries.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.538-543
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• 2018

Powdery mildew caused by Podosphaera xanthii is a disease in cucurbit crops especially in green house. The objective of this study was to determine the effect of alternative fungicide spraying system for control of powdery mildew disease. We selected four fungicides with different mode of action and made three treatment combinations of each fungicide in 2017. Pyraclostrobin-flutianyl-penthiopyrad treatment showed the highest control value (87%) while, pyraclostrobin-pyraclostrobin-pyraclostrobin treatment showed the lowest control value (32.5%). So it seemed like the treatment was not suitable for control of powdery mildew. In 2018, pyraclostrobin of pyraclostrobin-flutianyl-penthiopyrad was replaced to contact fungicide called iminoctadine-tris-albesilate and compared control effect of two treatments. Two of the treatments showed similar control value (87.0% for pyraclostrobin, 89.0% for iminoctadine-tris-albesilate). These two tests in 2017 and 2018 indicated that alternative treatment of different fungicides is essential for controlling of powdery mildew and inhibiting development of fungicide resistance.

• Journal of Plant Biotechnology
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• v.42 no.4
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• pp.350-355
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• 2015

Clubroot disease is one of the most wide-spread and devastating diseases in the cultivation of Chinese cabbage. To develop a protein marker for resistance to clubroot disease in Chinese cabbage, a comparative proteome analysis was performed between a sensitive line, 94SK, and a resistant line, CR Shinki DH. Three proteins of two fold or higher accumulation that are specific to each line were found 3 days after innoculation of the Plasmodiphora brassicae. They are glutamine synthetase, malate dehydrogenase/oxidoreductase and fructose-bisphosphate aldolase in the 94SK and actin, phosphoglycerate kinase, and Cu/Zn superoxide dismutase in the CR Shinki line. From the comparison of the synthesized proteins in the 94SK and the CR Shinki, CR Shinki was found to produce more ATP-binding protein for the ABC transporter while 94SK showed a higher level of pathogenesis-related protein 1 production. All of these proteomic variations may lead to the development of molecular markers to accelerate the breeding process.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.3
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• pp.156-159
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• 2003

Barley yellow mosaic virus (BaYMV) cause severe damage in barley cropping field especially yield reduction about 40% to 100% depend on climatic conditions and varieties. The correlations between disease incidence (DI) and changes of climatic conditions were analyzed. The average temperature affected on the DI in early barley growing stage before wintering. However any factors was not correlated with DI during wintering season that means barley growth was closely related to virus reproduction. Significant correlation between the highest temperature and DI during barley regeneration time that temperature, especially the highest, has to be considered to set appropriate time for DI investigation.

• Journal of Crop Science and Biotechnology
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• v.11 no.1
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• pp.13-16
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• 2008

Pepper fruit anthracnose caused by Colletotrichum species is an economically important disease that causes serious yield loss and quality deterioration in many Asian countries including South Korea and Taiwan. Recently, Capsicum baccatum PI594137 was found to exhibit broad-spectrum resistance to Colletotrichum acutatum. The inheritance of anthracnose resistance to C. acutatum was analyzed in an intraspecific population derived from a cross between C. baccatum Golden-aji and PI594137. Detached mature green fruits were inoculated using the microinjection method. The disease response was evaluated as the disease incidence and the overall lesion diameter at 7 days after inoculation(DAI). The segregation ratios of resistance and susceptibility to C. acutatum in the $F_2$ and $BC_s$ populations significantly fit a 3:1 Mendelian model. This result indicates that the resistance of PI594137 to C. acutatum is controlled by a single dominant gene.

• Research in Plant Disease
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• v.18 no.2
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• pp.129-132
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• 2012

Citrus bacterial canker is an economically important disease affecting citrus production in many citrusgrowing areas and several pathotypes have been recognized within the Xanthomonas pathogens causing canker. In view of the containment of the disease, accurate identification of the causal bacterium is important. In this study, triplex PCR method was developed by using the previously reported primers. Two groups of primer combination, such as, one group including primers 2/3, J-pth1/J-pth2 and XACF/XACR, and another group 2/3, J-pth1/J-pth2 and Xac01/Xac02, were suitable for the detection and differentiation of X. a. pv. citri $A^w$, X. a. pv. aurantifolii B and C, and X. a. pv. citrumelo E strains. Moreover, the primer combination of Xac01 and J-pth2 promised us to use as a specific primer set to detect X. a. pv. citrumelo E strain. The PCR methods developed in this study could be used for the rapid differentiation of Xanthomonas pathotypes of citrus.

• Research in Plant Disease
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• v.29 no.4
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• pp.399-404
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• 2023

Agricultural activities and the number of farms in the subarctic regions have been increasing annually after the coronavirus disease 2019 pandemic to achieve food self-sufficiency. Potatoes are vulnerable to soft rot bacteria at all stages of production, storage, and transportation. A novel bacterium, Pseudomonas sp. N3-W, isolated from Alaska tundra soil, grows at 5-25℃ and produces extracellular protease(s). N3-W caused necrotic spots (hypersensitivity) in hot pepper leaves and soft rot disease (pathogenicity) in potato tubers. The psychrotolerant N3-W caused significant soft rot symptoms on potatoes at a broad temperature range (5℃, 15℃, and 25℃). In contrast, mesophilic Pectobacterium carotovorum KACC 16999 induced severe rotting symptoms in potatoes at their optimal growth temperature of 15℃ and 25℃. However, it barely produced symptoms at 5℃, which is the appropriate storage and transportation temperature for potatoes. The results of pathogenicity testing imply that psychrotolerant soft rot pathogens from polar regions may cause severe soft rot not only during the crop growing season but also during storage and transportation. Our study indicates the possibility of new plant pathogen emergence and transmission due to the expansion of crop cultivation areas caused by permafrost thawing in response to recent polar warming.