• Korean Journal of Microbiology
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• v.3 no.1
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• pp.24-26
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• 1965

In July, 1963, a virulent outbreak of late blight in the potato field of Daekwanlyung area was studied and it was known as epidemics. Two stocks are $T_1$ and $T_1$ of Phytophthora infestans (Mont.) De Bary which isolated from Irish Cobbler were inoculated at field and green house respectively by cutted leaves method. Two strains have been distinguished in reactions to leaves: $T_1$: Irish Cobbler (r), Morin No. 1 (r) have shown infectivity of disease and Kennebec ($R_1$), 1512-C(16) ($R_2$), Pentland Ace ($R_3$) and Hokkai No. 17 ($R_4$) have not shown infectivity of disease; $T_1$: Irish Cobbler (r), Norin No. I (r) and Kennebec ($R_1$) have shown infectivity of disease and 1512-C (16) ($R_2$), Pentland Ace ($R_3$) and Hokkai No. 17($R_4$) have not shown infectivity of disease. Both are the first record of race O and race 1 of Phytophthora infestans (Mont.) De Bary in Korea.

• The Plant Pathology Journal
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• v.26 no.3
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• pp.280-285
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• 2010

In the course of a searching natural antifungal compounds from plant sources, we found that the methanol extract ($3,000\;{\mu}g/ml$) of Malus domestica fruits had potential of control against rice blast (Magnaporthe grisea) and tomato late blight (Phytophthora infestans). Under bioassay-guided purification, we isolated phloretin, a phenolic compound, with in vivo antifungal activity against M. grisea. By 1-day protective application of phloretin ($500\;{\mu}g/ml$), the compound strongly inhibited the disease development of M. grisea and P. infestans on rice and tomato seedlings, respectively. And red pepper anthracnose caused by Colletotrichum coccodes also was moderately suppressed. However, rice sheath blight (Rhizoctonia solani AG1), and barley powdery mildew (Blumeria graminis f. sp. hordei) were hardly controlled. In addition, the compound showed in vitro antifungal activity against some plant pathogenic fungi including Phytophthora capsici, Alternaria panax, Sclerotinia sclerotiorum, R. solani AG4, and M. grisea. This is the first report on the antifungal activity of phloretin against plant pathogenic fungi.

• Mycobiology
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• v.31 no.4
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• pp.229-234
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• 2003

A total of 24 isolates of Phytophthora infestans were tested and analyzed for their resistance to metalaxyl fungicides. Sensitivity to metalaxyl was determined by growing isolates on 20% V8 medium amended with 0, 5, and 100 ${\mu}g/ml$ metalaxyl. Four isolates among the 24 tested were resistant to metalaxyl. Eleven isolates were intermediate and nine isolates were sensitive. Amplified fragment length polymorphism(AFLP) assay was used to identify the amplification products of resistant isolates. As a result, selected fragments were cloned, sequences and primer pairs were developed which linked to metalaxyl insensitivity in P. infestans using competitive PCR.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1272-1275
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• 2017

Two dimeric sesquiterpenes were separated from Chloranthus japonicus Sieb. and identified as shizukaols C and F. They exhibited potent antifungal activities ($MICs=4-16{\mu}g/ml$) in vitro against various plant pathogenic fungi (Pythium ultimum, Phytophthora infestans, Botrytis cinerea, Colletotrichum lagenarium, Alternaria kikuchiana, and Magnaporthe grisea). Shizukaol C showed 88% and 91% protective activities in the greenhouse against Puccinia recondita (wheat leaf rust) and Phytophthora infestans (tomato late blight), respectively, at $100{\mu}g/ml$; shizukaol F exhibited 93% antifungal activity against Puccinia recondita at the same concentration. Therefore, these compounds might serve as interesting candidates for effective antifungal agents.

• The Plant Pathology Journal
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• v.15 no.4
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• pp.228-235
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• 1999

Genetic diversity of ninety-five Korean isolates of Phytophthora was investigated on the basis of PCR-RFLP of ribosomal DNA. The isolates were previously identified as following fifteen species by mycological and cultural characteristics; P. boehmeriae, P. cactorum, P. cambivora, P. capsici, P. cinnamoni, P. citricola, P. citrophthora, P. cryptogea, P. drechsleri, P. erythroseptica, P. infestans, P. megasperma, P. nicotianae, P. palmivora and P. sojae. The regions of small subunit (SSU) and internal transcribed spacer (ITS) of rDNA were amplified with primer pair, NS1 and ITS4, by polymerase chain reaction (PCR) and digested with nine restriction enzymes. P. boehmeriae, P. cactorum, P. cambivora, P. capsici, P. cinnamomi, P. citricola, P. citrphthora, P. infestans, P. nicotianae and P. palmivora showed specific band patterns for each species. However, P. sojae and P. erythroseptica presented identical band patterns and P. cryptogea, P. drechsleri and P. megasperma were divided into six groups, which were not compatible with delineation of the species. A group originated from cucurbits showed distinct band patterns from other groups, but the other five groups were closely related within 96.0% similarity, forming one complex group. Consequently, Korean isolates of Phytophthora were divided into thirteen genetic groups and each group was readily differentiated by comparing digestion patterns of AvaII, HaeIII, MboI, HhaI and MspI. Therefore, PCR-RFLP of rDNA using the five enzymes can be used to differentiate or identify the Phytophthora species reported in Korea so far.

• The Plant Pathology Journal
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• v.23 no.3
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• pp.203-209
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• 2007

Infection structures were observed using a fluorescence microscope at the penetration sites on the leaves of potato plants pre-inoculated with the bacterial strains Pseudomonas putida TRL2-3, Micrococcus luteus TRK2-2, and Flexibacteraceae bacterium MRL412, which mediated an induced systemic resistance on potato plants against late blight disease caused by Phytophthora infestans. In order to compare the infection structures on the leaves expressing systemic acquired resistance, the leaves of potato plants pre-treated with DL-3-amino butyric acid (BABA) were also observed after challenge inoculation with the same pathogen. The infection structures were investigated. The total number of germination and appressorium formation of P. infestans were counted. Furthermore, the frequencies of fluorescent epidermal cells at the penetration sites, which indicate a defense response of plant cell, were estimated. There were no differences on the germination rates of the fungal cysts among the untreated control, BABA pre-treated, and bacterial strains pre-inoculated plants. However, appressorium formation was slightly decreased on the leaves of BABA pre-treated plants compared to those of untreated as well as bacterial strains pre-inoculated plants. Furthermore, the frequencies of fluorescent cells of BABA pre-treated and bacterial strains pre-inoculated were higher than that of untreated plants, indicating an active defense reaction of the host cells against the fungal attack. On the other hand, the pre-treatment with BABA caused a stronger fluorescent of epidermal cells at the penetration sites compared to the pre-inoculation with the bacterial strains. Interestingly, the frequency of fluorescent cells by BABA, however, was lower than that by the bacterial strains. Based on the results it is suggested that the infection structures showing resistance reaction on the leaves of potato plants were different between by pre-inoculation with bacterial strains and by pre-treatment with BABA against the late blight pathogen.

• Korean Journal of Environmental Agriculture
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• v.16 no.3
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• pp.212-215
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• 1997

Parent isolates and $first-generation(F_1)$ progenies from single-sporangium of Phytophthora infestans were investigated for the acqusition of metalaxyl and streptomycin sulfate(SM) resistance. The parent isolates, KM10, U6, CDB6 showed resistance to metalaxyl, and F817, DNC303, DN107 to SM. Especially, the average mycelial growth of $F_1$ progenies of F817, CDB6, JD1 was more than 51% than parent isolates on 25ppm metalaxyl added V-8 juice agar, whereas those of KM10, U6, JD1 were extended more than 51% similar on 200ppm SM treatment. They acquired resistance on the basis of the standard in this experiment. There were positive correlations between parent isolates and $F_1$colonies in resistance. The $F_1$ colonies obtained from parent isolates showing above interinediate resistance on metalaxyl amended agar acquired much resistance.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2004.10a
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• pp.28-29
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• 2004

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• Journal of Microbiology and Biotechnology
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• v.15 no.2
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• pp.442-446
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• 2005

Fungicidal activities of Cassia obtusifolia extracts and their active principles were tested against Botrytis cinerea, Erysiphe graminis, Phytophthora infestans, Puccinia recondita, Pyricularia grisea, and Rhizoctonia solani, and compared with synthetic fungicides and two dihydroxyanthraquinones. At 1 g/l, the chloroform fraction of C. obtusifolia extracts showed fungicidal activity against B. cinerea, E. graminis, P. infestans, and Py. grisea, and the ethyl acetate fraction showed fungicidal activity against E. graminis and P. infestans. Danthrone was chromatographically isolated from the chloroform fraction and showed fungicidal activity against B. cinerea, E. graminis, P. infestans, and Py. grisea with 68, 100, 78, and $91\%$ control values at 0.5 g/l, respectively. Specifically, alizarin and quinizarin inhibited E. graminis, P. infestans, and Py. Grisea, but did not inhibit the growth of P. recondita and R. solani. These results indicate at least one of the fungicidal actions of danthrone.

• The Plant Pathology Journal
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• v.21 no.1
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• pp.33-38
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• 2005

Changes of control efficacy of chemical to potato late blight caused by Phytophthora infestans in potato fields from 2001 to 2004 were examined. Control efficacy of metalaxyl was suddenly decreased from 100% in 2002 to 50% in 2004 and that of dimethomorph also was similar to those of metalaxyl. However, the control efficacy of ethaboxam no great change. Both A1 and A2 mating type isolates were isolated from 2001 to 2004 in several areas in Korea. The majority of the P. infestans isolates were A1 mating type. Total 939 isolates of P. infestans obtained from several areas in Korea from 2001 to 2004 were examined for changes of sensitivity to metalaxyl. Frequencies of metalaxyl resistance isolates were gradually increased from 17% in 2001 to 84.2% in 2004, but isolation frequencies of metalaxyl sensitive and intermediate resistant isolate were decreased. Cause of decreasing control efficacy of metalaxyl was thought by increase of resistance isolates in A1 mating type population according to increasing metalaxyl use. Most isolates were grown at 0.5 ${\mu}g/ml of dimethomorph and isolates grown at 1 ${\mu}g/ml of dimethomorph were approximately 10.2-22.9%. However, no isolate was able to grow at 5.0 ${\mu}g/ml. Based on these results, minimum inhibitory concentrations (MIC) of dimethomorph to P. infestans were determined to be 0.5-1.0 ${\mu}g/ml. Our results indicated that the reason decreasing control efficacy of dimethomorph was not caused by occurrence of resistant isolates. About 5% and 12.1% isolates among the total isolates collected in 2003 and 2004 were grown on V-8 juice rye agar containing 1.0 ${\mu}g/ml ethaboxam. The 2.1 and 25.4% isolates had MICs of 0.2-0.4 ${\mu}g/ml, and MIC values of 87.9% and 74.3% isolates were less than 0.2 ${\mu}g/ml concentrations of ethaboxam. Therefore, resistance development by P. infestans to ethaboxam is not likely to occur in the natural condition.