• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.242-242
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• 2017

A potato cultivar, Haryeong, was released for table stock in 2005 and has been supplied to farmers since 2010. Black dot has been known as a disease causing tuber blemishes in the cultivar, which is primarily an issue in storage. To investigate the effect of curing periods on disease occurrence, four periods (1, 3, 6 and 9 weeks) of curing were applied on Haryeong tubers harvested from the highlands (800 m a.s.l) in September. Tubers were stored at $2-3^{\circ}C$ and 80-90% RH for 6-7 months and were visually checked for disease occurrence. Tuber infection was characterized by barely visible small black spots on tubers and dark sooty lesions in stolon end of tubers. Another symptoms were observed on the upper surface of tubers which showed irregular, small to large, and depressed areas of brown to blackish skin with necrotic lesions inside. Results showed decrease in black dot depending on the curing period that ranges 18-48, 3-35, 0-14 and 0-3% at 1, 3, 6 and 9 weeks curing, respectively. During the storage, however, percentage weight loss of tubers and percentage of tubers with sprouts increased slightly with increasing the curing period from 1-3 to 6-9 weeks.

• Research in Plant Disease
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• v.26 no.1
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• pp.48-52
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• 2020

In July 2019, typical rot symptom was observed on peach fruits harvested from the fields at Andong, Korea. As the disease progressed, white and purple colored mycelial mat developed on the surface of the infected fruits. A causal pathogen was isolated from the infected fruit and cultured on potato dextrose agar media for identification. Fungal colonies on potato dextrose agar produced 3 pigments, including purple, yellow, and white colors. The isolate incited fruit rot symptoms on artificially inoculated peach fruits, from which the same fungus was isolated, fulfilling Koch's postulates. Based on the morphological characteristics and sequence analysis of rDNA internal transcribed spacer, translation elongation factor 1-alpha, and β-tubulin, the causal agent of the disease was identified as Fusarium avenaceum. This study is the first report of fruit rot of peach fruits caused by Fusarium avenaceum in Korea.

• Mycobiology
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• v.39 no.3
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• pp.200-205
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• 2011

Marssonina coronaria associated with apple blotch disease causes severe premature defoliation, and is widely distributed in Korea. Thirteen isolates were collected from orchards located in Gyeongbuk Province from 2005~2007. All isolates displayed over 99.6% and 99.2% sequence similarity to each other in internal transcribed spacer regions and partial sequences of 28S rDNA, respectively. The isolates were phylogenetically closely related to Chinese isolates. Selected isolates did not differ in their pathogenicity. The optimum conditions for fungal growth were $20^{\circ}C$ and pH 6 on peptone potato dextrose agar (PPDA). Peptone and mannose were the best nitrogen and carbon source, respectively. Fungal growth was better on PPDA than on common potato dextrose agar. This study provides valuable information for integrated disease management program and facilitates the routine culturing of M. coronaria.

• 한국균학회소식:학술대회논문집
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• 2015.11a
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• pp.26-26
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• 2015

Phytophthora infestans is the causal agent of potato and tomato late blight, one of the most devastating plant diseases. P. infestans secretes effector proteins that are both modulators and targets of host plant immunity. Among these are the so-called RXLR effectors that function inside plant cells and are characterized by a conserved motif following the N-terminal signal peptide. In contrast, the effector activity is encoded by the C terminal region that follows the RXLR domain. Recently, I performed in planta functional profiling of different RXLR effector alleles. These genes were amplified from a variety of P. infestans isolates and cloned into a Potato virus X (PVX) vector for transient in planta expression. I assayed for R-gene specific induction of hypersensitive cell death. The findings included the discovery of new effector with avirulence activity towards the Solanum bulbocastanum Rpi-blb2 resistance gene. The Rpi-blb2 encodes a protein with a putative CC-NBS-LRR (a coiled-coil-nucleotide binding site and leucine-rich repeat) motif that confers Phytophthora late blight disease resistance. We examined the components required for Rpi-blb2-mediated resistance to P. infestans in Nicotiana benthamiana. Virus-induced gene silencing was used to repress candidate genes in N. benthamiana and to assay against P. infestans infections. NbSGT1 was required for disease resistance to P. infestans and hypersensitive responses (HRs) triggered by co-expression of AVRblb2 and Rpi-blb2 in N. benthamiana. RAR1 and HSP90 did not affect disease resistance or HRs in Rpi-blb2-transgenic plants. To elucidate the role of salicylic acid (SA) in Rpi-blb2-mediated resistance, we analyzed the response of NahG-transgenic plants following P. infestans infection. The increased susceptibility of Rpi-blb2-transgenic plants in the NahG background correlated with reduced SA and SA glucoside levels. Furthermore, Rpi-blb2-mediated HR cell death was associated with $H_2O_2$, but not SA, accumulation. SA affects basal defense and Rpi-blb2-mediated resistance against P. infestans. These findings provide evidence about the roles of SGT1 and SA signaling in Rpi-blb2-mediated resistance against P. infestans.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.257-257
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• 2022

Late blight, caused by the hemibiotrophic oomycete pathogen Phytophthora infestans, has been the most important disease limiting potato production worldwide. P. infestans undergo major population shifts in agricultural systems via the successive emergence and migration of asexual lineages. The phenotypic and genotypic bases of these selective sweeps are largely unknown but management strategies need to adapt to reflect the changing pathogen population. Here, we used molecular markers to divide the 86 South Korea isolates into six clonal lineages: KR_1_A1, KR_2_A2, SIB-1, US-11, SIB-1 like, and KR-2 like. We documented the emergence of a new lineage, termed SIB-1 like, and KR-2 like, and their rapid replacement of other lineages to exceed 35% of the pathogen population across South Korea. Genome analyses of the Korean P. infestans populations revealed extensive genetic polymorphism, particularly in effector genes. Importantly, SIB-1 like isolates carry an intact Avr8 effector gene that triggers resistance in potato carrying the corresponding R immune receptor gene R8 cloned from Solarium demissum. These findings point toward a strategy for deploying genetic resistance to mitigate the impact of the SIB-1 like lineage and illustrate how pathogen population monitoring, combined with genome analysis, informs the management of devastating disease epidemics. Further study is being done on pathogenicity of the SIB-1 like isolates on cultivated potatoes and changes in expression patterns of disease effector genes within the SIB-1 like isolates

• Journal of Bio-Environment Control
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• v.32 no.2
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• pp.165-171
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• 2023

Potato dry rot is one of the potato storage diseases caused by Fusarium species and is a representative pathological disorder that induced post-harvest loss during storage. Chlorpropham treatment for sprouting inhibition is mainly used for room temperature storage of potatoes for processing. In this study, the inhibitory effect of chlorpropham on Fusarium-induced dry rot of potato 'Dano'. To investigate the mycelial growth rate of the dry rot fungus (Fusarium solani Appel & Wollenw), mycelial growth was investigated in a chlorpropham (5.0, 50.4, 503.8, and 5,038 ppm) and prochloraz (0.1, 1.0, 10.0, and 100.0 ppm) medium containing F. oxysporum mycelia. Mycelia were more inhibited as the concentration of chlorpropham and prochloraz increased during incubation at 20℃, and the inhibition rate was 98.2% and 100% when treated with 503.8 ppm of chlorpropham and 10ppm of prochloraz in 14 days, respectively. Potato Dano tubers inoculated with F. oxysporum were dipped in chlorpropham (5.0, 50.4, and 503.8 ppm) and prochloraz (100 ppm) to investigate the effect of preventing dry rot during cold storage at 20℃ and 4℃ in vivo. The disease diameter of potatoes stored at room temperature (about 20℃) was reduced to 13.0 mm in the prochloraz 100 ppm teatment, and 10.7 mm in the chlorpropham 50.4 ppm treatment compared to 13.7 mm in the control tuber at 70 days of storage. The disease progression in all treatments including control was similar with no statistically significant difference at 4℃ air temperature. From the results of this study, it is considered that treatment with 50.4 ppm of chlorpropham after harvest will be useful for suppressing dry rot of stored potatoes.

• The Plant Pathology Journal
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• v.22 no.3
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• pp.278-282
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• 2006

Bacillus vallismortis EXTN-1, a biocontrol agent in cucumber, tomato and potato was tested in rice pathosystem against rice fungal pathogens viz. Magnaporthe grisea, Rhizoctonia solani and Cochliobolus miyabeanus. Apart from increasing the yield in the bacterized plants (11.6-12.6% over control), the study showed that EXTN1 is effective in bringing about disease suppression against all the tested fungal pathogens. EXTN-l treatment resulted in 52.11% reduction in rice blast, 83.02% reduction in sheath blight and 11.54% decrease in brown spot symptoms. As the strain is proven as an inducer for systemic resistance based on PR gene expression in Arabidopsis and tobacco models, it is supposed that a similar mechanism works in rice, bringing about disease suppression. The strain could be used as a potent biocontrol and growth-promoting agent in rice cropping system.

• Journal of the Korean Society of Tobacco Science
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• v.28 no.2
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• pp.158-161
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• 2006

Main tobacco diseases were surveyed on major flue-cured leaf tobacco fields throughout South Korea in 2006. Mosaic caused by potato virus Y and bacterial wilt caused by Ralstonia solanacearum were most severe during harvest season. During last ten years, the damage by tobacco mosaic virus was reduced but the incidence of bacterial wilt increased. These changes of the disease incidences coincide with release time of the tobacco cultivar resistant to the tobacco mosaic virus but susceptible to bacterial wilt pathogen. Wild fire(Pseudomonas syringae pv. tabaci strain ungulate) occurred severely at Kangwon province, though the symptom of wild fire with yellow halo was not observed.

• Korean Journal Plant Pathology
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• v.14 no.2
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• pp.145-149
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• 1998

Four nonpathogenic isolates of Fusarium oxysporum isolated from spinach showed suppressive effect on the occurrence of the Fusarium wilt of spinach caused by F. oxysporum f. sp. sprinaciae, among which NF01 controlled the disease most effectively. And NF01 was not pathogenic to tomato, cucumber, radish and spinach. This isolate was further tested for the biological control of the disease. The isolate was not inhibitory to the growth of the pathogen on potato sucrose agar medium, however the Fusarium wilt disease occurred less by drenching spore suspension of the nonpathogenic isolate. The control effect of the isolate was higher at lower inoculum level of the pathogen than at the higher inoculum level, and in the pretreatments than the simultaneous treatment of the isolate with the pathogen inoculation. The nit mutants of the isolate were easily formed on chlorate containing media, and was reisolated selectively as nit mutant from infected soil and plants. The reisolation rate of the isolate as opposed to pathogen was high at preinoculated soil and plants relative to the simultaneous inoculation of the isolate with the pathogen.

• Research in Plant Disease
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• v.9 no.1
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• pp.32-35
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• 2003

Pink rot of potato (Solanum tuberosum L.) occurred at Pyeongchang in Gangwon and at Bosung in Junnam province since 1999. The disease incidence in the surveyed areas was about 5% of harvested potatoes in 2002. Affected tubers showed a dull brown appearance and the lenticels and eyes on tubers turned dark brown. The cut surface of the diseased tuber colored faint pink and the entire surface of the diseased tuber becomes deep salmon pink within 30 min. The pathogen isolated from the diseased tubers was identified as Phytophthora erythroseptica based on morphological and cultural characteristics. Mycelial mat was fairly fluffy, rosette or stellate patterns and rounded or angular hyphal swellings were farmed in water, Temperature for mycelial growth was ranged from 5 to 3$0^{\circ}C$ and optimal temperature was $25^{\circ}C$. Non-papillate sporangia were persistent on stalk and ellipsoid, ovoid, obpyriform or distorted in shape, often with a constriction distal in the middle. Size of sporangia was 41.3~69.6$\times$26.8~47.4 (av, 55.5$\times$37.1) ${\mu}{\textrm}{m}$. Sexuality of Phytophthora erythroseptica was homothallic. Oogonia were 30~46 ${\mu}{\textrm}{m}$ in diameter and oospores were 28~35 ${\mu}{\textrm}{m}$ in diameter, Elongated or cyclindrical antheridia were all amphigynous. This is the first report on potato pink rot caused by Phytophthora erythroseptica in Korea.