• The Plant Pathology Journal
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• v.27 no.4
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• pp.360-366
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• 2011

Bacterial leaf spot of Euphorbia pulcherrima has been reported in many countries. Characterization by polyphasic approaches indicated that the isolates from India, USA and New Zealand could be distinguished based on rep-PCR profiles and gyrB phylogenies, while the Chinese isolates should be ascribed to Xanthomonas axonopodis pv. poinsettiicola.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.89.2-90
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• 2003

Potato late blight, caused by Phytophthora infestans, is one of the important diseases in potato cultivation areas. Though the incidence of late blight was depend on the inoculums and climatic condition In each fields, the foliar blight was reached to 100％ under the severe disease pressure condition in 2003. Outbreak of foliar blight was concentrated from May and July and evaluation of ten fungicides to control of late blight was made at Daekwallryoung area in potato fields. Based on the company recommendation, those fungicides were applied by a sprayer at the recommended rates on a weekly application schedule. Effect of ten fungicides on foliar blight was based on area under disease progress curve (AUDPC). Across all fungicides was reduced by 77％ in AUDPC and dimethomorph was reduced by 92％ in AUDPC during the same period, respectively. Those fungicide were inhibited the mycelial growth of isolate with different rate in chemical amended medium and several fungicides were completely limited the growth of isolate.

• The Plant Pathology Journal
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• v.24 no.2
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• pp.183-190
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• 2008

Plant-cell-wall-degrading enzymes (PCWDEs) of Pectobacterium carotovorum subsp. carotovorum are the key virulence factor in pathogenesis of soft rot disease of vegetables. The production of PCWDEs is controlled in a cell density dependent manner to avoid the premature production of PCWDEs and subsequent activation of plant defense. N-oxoacyl-homoserine lactone (OHL) is essential for quorum sensing in the soft rot pathogen and the expI gene is responsible for OHL production. The ExpI homolog isolated from P. carotovorum subsp. carotovorum SL940 had 94% identity with ExpI of E. carotovora subsp. carotovora scc3193 and 74% identity with Carl of E. carotovora subsp. atroseptica. The transgenic plants that express exp I uner the control of CaMV35S promoter were able to produce diffusible OHL. Transgenic plants producing OHL were very resistant to the infection of P. carotovorum subsp. carotovorum. Since the PR1 gene was strongly induced and NPR1 and NPR4 were induced weakly in transgenic plants compared to the wild type, salicylic acid-dependent pathways is likely involved in the resistance to the soft rot pathogen P. carotovorum subsp. carotovorum in ExpI transgenic plants.

• Journal of Life Science
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• v.18 no.6
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• pp.858-864
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• 2008

In the greenhouse fields for fruits and vegetables during the winter in Korea, there are serious damages by the sclerotium diseases due to the low temperature and humidity. This study was carried out to select an antagonic agent for the biological control of the sclerotium diseases. The 55 antagonic agents were selected from the rhizosphere in soil where the fruits and vegetables were cultivated in the green house fields, and strain AB02 among the tested isolates was estimated to be the strongest antagonist against the sclerotium disease. Using strain AB02, the antifungal spectrum was tested against 5 different plant pathogens. According to the results of the test, strain AB02 . showed the high antagonistic effect against Botrytis cinerea and Sclerotinia sclerotiorum. For the experiment of biological control against the sclerotium disease, it was estimated the suppression effect and the control effect by the strain in the pot experiment using the green perilla. According to the result of the pot experiments, the suppression effect was 40% and the control effect was 62%, respectively. For the stimulation effect of the tested plant growth by strain AB02 compared to the control, it was improved as 120% for the total length, 141% for the liveweight, 121% for the total number of leaves, 185% for the leaf area, and 327% for the liveweight of the root, respectively. Strain AB02 showing the antagonistic effect against the sclerotium disease and the stimulation effect for the plant growth was identified as Bacillus sp.

• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.880-884
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• 2008

A strain of Streptomyces sp. (M10) antagonistic to Botrytis cinerea was isolated from orchard soil obtained from Jeju Island, Korea. An antifungal substance (CN1) was purified from the culture extracts of the strain, and then identified as valinomycin through extensive spectroscopic analyses. Valinomycin showed potent in vitro antifungal activity against Botrytis cinerea and also in vivo control efficacy against Botrytis blight development in cucumber plants. Overall, the disease control efficacy of valinomycin was similar to that of vinclozolin, a commercial fungicide. This study provides the first report on the disease control efficacy of valinomycin against Botrytis blight.

• The Plant Pathology Journal
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• v.25 no.4
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• pp.361-368
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• 2009

The efficacy of the combination of Burkholderia cepacia B23 with 0.75% chitosan and 3% calcium chloride ($CaCl_2$) as a biocontrol treatment of anthracnose disease of papaya caused by Colletotrichum gloeosporioides, was evaluated during storage. The growth of B. cepacia B23 in papaya wounds and on fruit surfaces was not affected in presence of chitosan and $CaCl_2$ or combination throughout the storage period. The combination of B. cepacia B23 with chitosan-$CaCl_2$ was more effective in controlling the disease than either B. cepacia B23 or chitosan or other combination treatments both in inoculated and naturally infected fruits. Combining B. cepacia B23 with chitosan-$CaCl_2$ gave the complete control of anthracnose infection in artificially inoculated fruits stored at $14^{\circ}C$ and 95% RH for 18 days, which was similar to that obtained with fungicide $benocide^{(R)}$. Moreover, this combination offered a greater control by reducing 99% disease severity in naturally infected fruits at the end of 14 days storage at $14^{\circ}C$ and 95% RH and six days post ripening at $28\pm2^{\circ}C$, which was superior to that found with $benocide^{(R)}$ or other treatments tested. Thus, postharvest application of B. cepacia B23 with chitosan-$CaCl_2$ as enhancers represents a promising alternative to synthetic fungicides for the control of anthracnose in papaya during storage.

• Research in Plant Disease
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• v.11 no.1
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• pp.39-42
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• 2005

Powdery mildew, caused by Sphaerotheca aphanis var. aphanis, is an economically significant disease of strawberry in Korea. When powdery mildew is not controlled adequately, it often spreads rapidly through strawberry plants and damage is associated with reduced yields. Proper timing of fungicide applications is, therefore, essential for effective disease control. This study evaluated the efficacy by application schedule of fungicides before harvest stage for preventing powdery mildew in 2001-2003. The systemic fungicides, azoxystrobin, kresoxim-methyl, and cupper fungicide DBEDC were applied preventively during the first part of the cultivating season. Preventative applications of DBEDC by dipping treatment before transplanting and kresoxim-methyl by foliar spray before blooming stage were one of the most effective control schedule tested to prevent and manage this disease. This research demonstrated the significance of application time to control of powdery mildew, particularly provided elimination unnecessary sprays of agrochemicals and reduction costs for strawberry growers.

• The Plant Pathology Journal
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• v.33 no.5
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• pp.450-457
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• 2017

Scabs caused by Venturia carpophila greatly reduce the quality of the fruits of the Japanese apricot (Prunus mume) when the disease is not properly managed. The disease produces a superficial blemish that is unlikely to affect the overall yield of processed fruit, but reduce the value of fruit intended for the fresh market. Incidence rates of scab at sprayed and unsprayed orchards range from 0% to 21.5% and from 30.2% to 100%, respectively, in the major cultivation regions of Jeonnam Province during the growing season of 2009. The trends in disease progress were quite similar, regardless of regions, and cultivar Namgo was relatively less damaged by scab compared to cultivar Cheonmae among the tested Japanese apricot cultivars. The fruits on branches 1.5 m above the infected Japanese apricot trees and the stem-end parts of the infected fruits were more severely damaged by scabs, possibly because of rain and run-off facilitate dissemination of conidia of V. carpophila and subsequent infection of the fruits or branches. The conidia of V. carpophila were dispersed from March 24 to April 26 in 2010, and more conidia were dispersed from 2-year-old branches than 1-year-old branches. Since the control efficacies were higher than 90% after more than two applications of Trifloxystrobin WG at 10-day-intervals from mid April, it is that effective fungicides be applied at least two times at 10-day-intervals from the middle of April to manage scabs of Japanese apricot in orchards.

• The Plant Pathology Journal
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• v.29 no.4
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• pp.386-396
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• 2013

Reactive oxygen species (ROS) generation in tomato plants by Ralstonia solanacearum infection and the role of hydrogen peroxide ($H_2O_2$) and nitric oxide in tomato bacterial wilt control were demonstrated. During disease development of tomato bacterial wilt, accumulation of superoxide anion ($O_2{^-}$) and $H_2O_2$ was observed and lipid peroxidation also occurred in the tomato leaf tissues. High doses of $H_2O_2$ and sodium nitroprusside (SNP) nitric oxide donor showed phytotoxicity to detached tomato leaves 1 day after petiole feeding showing reduced fresh weight. Both $H_2O_2$ and SNP have in vitro antibacterial activities against R. solanacearum in a dose-dependent manner, as well as plant protection in detached tomato leaves against bacterial wilt by $10^6$ and $10^7$ cfu/ml of R. solanacearum. $H_2O_2$- and SNP-mediated protection was also evaluated in pots using soil-drench treatment with the bacterial inoculation, and relative 'area under the disease progressive curve (AUDPC)' was calculated to compare disease protection by $H_2O_2$ and/or SNP with untreated control. Neither $H_2O_2$ nor SNP protect the tomato seedlings from the bacterial wilt, but $H_2O_2$ + SNP mixture significantly decreased disease severity with reduced relative AUDPC. These results suggest that $H_2O_2$ and SNP could be used together to control bacterial wilt in tomato plants as bactericidal agents.

• Research in Plant Disease
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• v.28 no.3
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• pp.122-131
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• 2022

Colletotrichum acutatum s. lat. 20JDS8 sensitive and 20CDJ6 resistant to pylaclostrobin were used to investigate the cross-resistance with fungicides belonging to the strobilurins and the characteristics of fungicidal controlling activities with different mechanisms against the isolate resistant to the fungicide. The resistant isolate of 20CDJ6 also showed the resistance to azoxystrobin, trifloxystrobin, and kresoxim-methyl, suggesting that there is a cross-resistance relationship. All fungicides with different action mechanisms inhibited mycelial growth of both susceptible and resistant isolates of C. acutatum s. lat., but their disease control effects in fruits were different according to the fungicides. The disease control effect of isopyrazam against 20JDS8 and 20CDJ6 was very low, and fluazinam showed a control effect of 91.9% and 88.1% against 20JDS8 and 20CDJ6 only when it was treated before inoculation by spraying spore suspensions on pepper fruits without wounds. Tebuconazole and prochloraz effectively inhibited not only the mycelial growth of 20JDS8 and 20CDJ6 on potato dextrose agar medium, but also disease incidence in red pepper fruits. As a result of this study, C. acutatum s. lat. 20CDJ6 resistant to pyraclostrobin showed cross-resistance with other strobilurin fungicides. In addition, we think that fluazinam, tebuconazole, and prochloraz can be recommended as alternative fungicides for the control of red-pepper pyranthracnose pathogens resistant pyraclostrobin. However, fluazinam can be effective only if it is treated protectively before the occurrence of the disease.