• The Plant Pathology Journal
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• v.26 no.3
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• pp.209-215
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• 2010

Plant pathogenic oomycetes, such as Phytophthora spp., are the causal agent of the most devastating plant diseases. During infection, these pathogens accomplish parasitic colonization of plants by modulating host defenses through an array of disease effector proteins. These effectors are classified in two classes based on their target sites in the host plant. Apoplastic effectors are secreted into the plant extracellular space, and cytoplasmic effectors are translocated inside the plant cell, through the haustoria that enter inside living host cell. Recent characterization of some oomycete Avr genes showed that they encode effector protein with general modular structure including N-terminal conserved RXLR-DEER motif. More detailed evidences suggest that these AVR effectors are secreted by the pathogenic oomycetes and then translocated into the host plant cell during infection. Recent findings indicated that one of the P. infestans effector, Avrblb2, specifically induces hypersensitive response (HR) in the presence of Solanum bulbocastanum late blight resistance genes Rpi-blb2. On the other hand, another secreted RXLR protein PexRD8 originated from P. infestans suppressed the HCD triggered by the elicitin INF1. In this review, we described recent progress in characterized RXLR effectors in Phytophthora spp. and their dual functions as modulators of host plant immunity.

• Research in Plant Disease
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• v.16 no.3
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• pp.274-278
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• 2010

Potato late blight caused by Phytophthora infestans was the most constrain disease at potato cultivation areas. The mating type distribution and fungicides response of P. infestans were investigated to elucidate the changes of pathogen from Gangwon province. On the fungal isolates in 2006, 58.7% were A1 mating type and 41.3% were A2 mating type. In 2007, A1 mating type isolates increased to 93.3% and A2 mating type isolates were collected from Jinbu areas as much as 6.7%. About 234 isolates analysed for metalaxyl response, the results was resistance 73.7%, intermediate 18.8% and sensitive 7.5% in 2006. And it was resistance 59.4%, intermediate 4.0% and sensitive 36.6% in 2007. It meant that mating type distribution and fungicide response were very different over the collection sites. Minimal inhibition concentration (MIC) of dimethomorph examined with 126 isolates in 2006 and 106 isolates in 2007. MIC over $1.0\;{\mu}g/ml$ was 56.3% in 2006 and it was 3.8% in 2007. The average $EC_{50}$ value of P. infestans was $0.37\;{\mu}g/ml$ in 2006, but it decreased to $0.12\;{\mu}g/ml$ in 2007. Fungicides response and pathogenesis of P. infestans should be monitored continuously to enhance the chemical efficacy at potato fields.

• The Korean Journal of Mycology
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• v.52 no.2
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• pp.73-96
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• 2024

Root and stem rot caused by Phytophthora palmivora is one of the most serious diseases affecting durian production in Thailand where metalaxyl, an effective fungicide against oomycetes, has been used extensively for a long period to control this disease. Although field isolates of P. palmivora resistant to metalaxyl exist in Thailand, a molecular basis for P. palmivora has not yet been elucidated regarding metalaxyl resistance. The current study tested whether P. palmivora RPA1 (the DNA-directed RNA polymerase I subunit gene), a homolog gene of RPA190 associated with metalaxyl resistance in some isolates of Phytophthora infestans, had a role in the resistance mechanism toward metalaxyl. In total, 40 durian-derived isolates of P. palmivora were assessed for metalaxyl sensitivity using a mycelial growth inhibition assay. The effective concentrations for 50% mycelial growth inhibition values for all isolates tested were in the range 0.01-872.88 mg/L. The isolates were clustered into three groups: sensitive (n=23), moderately resistant (n=11), and resistant (n=6) groups. No polymorphism was revealed based on multiple alignment analysis of the amino acid sequences translated from the corresponding DNA sequences in the region of RPA1 of the metalaxyl-sensitive (n=5), moderately resistant (n=2), and resistant isolates (n=6). Furthermore, investigation of the RPA1 expression among these representative isolates (n=3, each group) indicated that RPA1 expression may not be involved in the regulation of P. palmivora resistance to metalaxyl. Based on this line of evidence, there was no detected relationship regarding metalaxyl resistance and P. palmivora RPA1.

• The Plant Pathology Journal
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• v.30 no.3
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• pp.254-260
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• 2014

Potato Rpi-blb2 encodes a protein with a coiled-coil-nucleotide binding site and leucine-rich repeat (CC-NBSLRR) motif that recognizes the Phytophthora infestans AVRblb2 effector and triggers hypersensitive cell death (HCD). To better understand the components required for Rpi-blb2-mediated HCD in plants, we used virus-induced gene silencing to repress candidate genes in Rpi-blb2-transgenic Nicotiana benthamiana plants and assayed the plants for AVRblb2 effector. Rpi-blb2 triggers HCD through NbSGT1-mediated pathways, but not NbEDS1- or NbNDR1-mediated pathways. In addition, the role of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) in Rpi-blb2-mediated HCD were analyzed by monitoring of the responses of NbICS1-, NbCOI1-, or NbEIN2-silenced or Rpi-blb2::NahG-transgenic plants. Rpi-blb2-mediated HCD in response to AVRblb2 was not associated with SA accumulation. Thus, SA affects Rpi-blb2-mediated resistance against P. infestans, but not Rpi-blb2-mediated HCD in response to AVRblb2. Additionally, JA and ET signaling were not required for Rpi-blb2-mediated HCD in N. benthamiana. Taken together, these findings suggest that NbSGT1 is a unique positive regulator of Rpi-blb2-mediated HCD in response to AVRblb2, but EDS1, NDR1, SA, JA, and ET are not required.

• The Plant Pathology Journal
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• v.37 no.6
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• pp.580-595
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• 2021

Although late blight is an important disease in ecofriendly potato cultivation in Korea, it is highly dependent on the use of eco-friendly agricultural materials and the development of biological control technology is low. It is a necessary to develop an effective biocontrol agent to inactivate late blight in the field. AFB2-2 strain is a gram-positive with peritrichous flagella. It can utilize 20 types of carbon sources, like L-arabinose, and D-trehalose at 35℃. The optimal growth temperature of the strain is 37℃. It can survive at 20-50℃ in tryptic soy broth. The maximum salt concentration tolerated by AFB2-2 strain is 7.5% NaCl. AFB2-2 strain inhibited the mycelial growth of seven plant pathogens by an average inhibitory zone of 10.2 mm or more. Among the concentrations of AFB2-2, 10⁷ cfu/ml showed the highest control value of 85.7% in the greenhouse. Among the three concentrations of AFB2-2, the disease incidence and severity of potato late blight at 10⁷ cfu/ml was lowest at 0.07 and 6.7, respectively. The nucleotide sequences of AFB2-2 strain were searched in the NCBI GenBank; Bacillus siamensis strain KCTC 13613, Bacillus velezensis strain CR-502, and Bacillus amyloliquefaciens strain DSM7 were found to have a genetic similarity of 99.7%, 99.7%, and 99.5%, respectively. The AFB2-2 strain was found to harbor the biosynthetic genes for bacillomycin D, iturin, and surfactin. Obtained data recommended that the B. velezensis AFB2-2 strain could be considered as a promising biocontrol agent for P. infestans in the field.

• Korean Journal Plant Pathology
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• v.14 no.3
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• pp.278-285
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• 1998

Effects of chitosan on growth of tomato plant, and suppression of Fusaruim wilt caused by Fusarium oxysporum f. sp. lycopersici and late blight casued by Phytophthora infestans, were examined. Both late blight and fusarium wilt were suppressed by spray and irrigation of chitosan, respectively. Inhibition of mycelial growth was not greatly affected by molecular size of chitosan but, concentration dependent effects was observed. Ninty percent of P. infestans and 80% of F. oxysporum f. sp. lycopersici of mycelial growth was inhibited by 1,000 ppm of chitosan (MW 30,000~50,000) when amended in plate media. Induction of defense-related gene expression in plant by chitosan treatments were observed when chitosan treated tobacco and tomato RNA samples were hybridized with several defense-related genes as probes. The results revealed that $\beta$-1,3-glucanase and chitinase genes were strongly induced, while pathogenesis-related protein-1, 3-hydroxy-3-methylglutaryl coenzyme A reductase, anionic peroxidase, phenylalanine ammonia lyase genes were weakly induced by chitosan treatment. These results suggest that chitosan have dual effects on these host-pathogen interactions. Possible roles of chitosan in suppression of tomato diseases by inhibition of mycelial growth and activation of plant defense responses are discussed.

• Korean Journal of Breeding Science
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• v.42 no.2
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• pp.139-143
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• 2010

Late blight caused by Phytophthora infestans is historically a serious epidemic disease in potato and tomato cultivations. Accession L3708 (Solanum pimpinellifolium), a new source for late blight resistance was identified in AVRDC, and carries the resistance gene, Ph-3, incompatible to P. infestans race 3. The AFLP markers linked to Ph-3 were previously developed from the L3708 accession (Chunwongse et al. 2002). To facilitate tomato breeding with the Ph-3 gene, an attempt was made to convert AFLP markers to sequence-characterized amplified region (SCAR) markers. Among 6 AFLP markers, only one AFLP marker, L87, was successfully converted to SCAR marker. The resistance-specific 230 bp AFLP fragment was cloned and sequenced, and the PCR primer amplifying a 123 bp fragment was designed. This SCAR marker could discriminate resistant and susceptible individuals with high stringency. The developed SCAR marker could be used for the marker assisted-selection in tomato breeding programs.

• The Plant Pathology Journal
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• v.38 no.5
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• pp.541-549
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• 2022

Potato late blight caused by Phytophthora infestans is a destructive disease in Korea. To elucidate the genomic variation of the mitochondrial (mt) genome, we assembled its complete mt genome and compared its sequence among different haplotypes. The mt genome sequences of four Korean P. infestans isolates were revealed by Illumina HiSeq. The size of the circular mt genome of the four major genotypes, KR_1_A1, KR_2_A2, SIB-1, and US-11, was 39,872, 39,836, 39,872, and 39,840 bp, respectively. All genotypes contained the same 61 genes in the same order, comprising two RNA-encoding genes, 16 ribosomal genes, 25 transfer RNA, 17 genes encoding electron transport and ATP synthesis, 11 open reading frames of unknown function, and one protein import-related gene, tatC. The coding region comprised 91% of the genome, and GC content was 22.3%. The haplotypes were further analyzed based on sequence polymorphism at two hypervariable regions (HVRi), carrying a 2 kb insertion/deletion sequence, and HVRii, carrying 36 bp variable number tandem repeats (VNTRs). All four genotypes carried the 2 kb insertion/deletion sequence in HVRi, whereas HVRii had two VNTRs in KR_1_A1 and SIB-1 but three VNTRs in US-11 and KR_2_A2. Minimal spanning network and phylogenetic analysis based on 5,814 bp of mtDNA sequences from five loci, KR_1_A1 and SIB-1 were classified as IIa-6 haplotype, and isolates KR_1_A2 and US-11 as haplotypes IIa-5 and IIb-2, respectively. mtDNA sequences of KR_1_A1 and SIB-1 shared 100% sequence identity, and both were 99.9% similar to those of KR_2_A2 and US-11.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.10a
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• pp.34.2-34
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• 1999

• The Korean Journal of Pesticide Science
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• v.8 no.2
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• pp.137-144
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• 2004

[ $\beta$ ]-Ketoacetoanilide chloride derivatives containing a substituent at 4 in phenyl group (para) reduced specifically the development of tomato late blight caused by Phytophthora infestans. Among $\beta$ketoacetoanilide chloride derivatives, five (KIST163, KIST170, KIST260, KIST263, and KIST267) were selected and tested for their protective, curative, systemic, persistent activities, and disease control efficacy against tomato late blight on adult plants. They exhibited a strong l-day protective activity and $EC_{50}$ of KIST163 and KIST170 were 21.9 and $14.5{\mu}g/mL$, respectively. However, they had little curative and systemic activities. Good persistence of KIST163 and KIST170 on tomato plants were observed against P. infestans; both KIST163 and KIST170 at $100{\mu}g/mL$ showed control values more than 75% in a 7-day protective applications. In addition, the two chemicals effectively controlled the occurrence of P. infestans on adult tomato plants. These results indicate that five $\beta$-ketoacetoanilide chloride derivatives are foliar fungicides with a preventive action and KIST163 and KIST170 have a potential for the control of tomato late blight in the fields.