• The Plant Pathology Journal
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• v.25 no.1
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• pp.103-107
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• 2009

In the course of a searching natural antifungal compounds from plant seeds, we found that the methanol extract of Psoralea corylifolia seeds showed potent control efficacy against tomato late blight caused by Phytophthora infestans and wheat leaf rust Puccinia recondita. Under bioassay-guided purification, we isolated two furanocoumarins, psoralen and isopsoralen, with anti-oomycete activity against P. infestans. By 1-day protective application, both compounds strongly reduced the disease development of P. infestans on tomato seedlings, but hardly controlled development of leaf rust on wheat seedlings. This is the first report on the anti-oomycete activity of P. corylifolia as well as that of psoralen and isopsoralen.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.192-196
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• 1994

Two hundred and fourty-seven isolates of Phytophthora infestans obtained from infested potato leaves from the spring of 1991 to the fall of 1993 from potato fields in various regions of Korea were tested for their fungicides resistances. A total of 20.9% isolates were not suppressed at 50 ppm of metalaxyl in 1991, but isolates from 1993 were suppressed at 50 ppm of metalaxyl. Ten resistant isolates and 10 susceptible isolates to metalaxyl were selected and tested against oxadixyl, fosetyl-Al, and phosphorous acid. Effectiveness of these chemicals were no better than that of metalaxyl. Dimethomorph suppressed all isolates at 1 $\mu\textrm{g}$/ml suggesting that it might be a potential chemical to control Phytophthora infestans. Mating types of all isolates from diseased leaves in 1993 turned out to be A2 type.

• Microbiology and Biotechnology Letters
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• v.30 no.2
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• pp.162-166
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• 2002

Two bithiazole-type antibiotics were isolated from the culture broth of a Myxococcus species which isolated from the marine sediment off the coast of Cheju Island, Korea. The structures of these metabolites were determined as KR025 and melithiazole F, previously reported bithiazoles, using combined spectroscopic methods. Both compounds showed an antifungal activity. In in vivo tests, these compounds exhibited potent controlling activities against tomato late blight, wheat leaf rust, and barley powdery mildew with control values more than 80% at a concentraton of 20 $\mu\textrm{g}$/ml.

• Journal of Microbiology
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• v.39 no.2
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• pp.126-132
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• 2001

For rapid and secure differentiation of P. infestans from other Phytophthora species, two fragments obtained from randomly amplified polymorphic DNA (RAPD) profiles were selected as markers. Also, primers for in polymerase chain reaction (PCR) to detect P. infestans specifically were developed by analyzing the sequences of ITSII regions in rDNA of Phytophthora species. The primers, PISP-1 and ITS3 amplified a single. Fragment 450 bp of about in P. infestans, but not in other fungal or bacterial isolates. Annealing temperatures and template DNA quantities were varied for the optimization of PCR conditions. From the result of the PCR detection study, species-specific primers were selected under annealing temperatures ranging from 55$^{\circ}C$ to 61$^{\circ}C$, and template DNA levels ranging from 10 pg to 100 ng.

• 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.25 no.2
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• pp.165-171
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• 2009

Biological control activity of Acremonium strictum BCP, a mycoparasite on Botrytis cinerea, was examined against six plant diseases such as rice blast, rice sheath blight, cucumber gray mold, tomato late blight, wheat leaf rust, and barley powdery mildew in growth chambers. The spore suspension of strain BCP showed strong control activities against five plant diseases except against wheat leaf rust. On the other hand, the culture filtrate of A. strictum BCP was effective in controlling only cucumber gray mold and barley powdery mildew. Further in vivo biocontrol activities of A. strictum BCP against tomato gray mold were investigated under greenhouse conditions. Control efficacy of the fungus on tomato gray mold increased in a concentration-dependent manner. Treatment of more than $1{\times}10^6$ spores/ml significantly controlled the disease both in tomato seedlings and in adult plants. The high disease control activity was obtained from protective application of the strain BCP, whereas the curative application did not control the disease. Foliar infections of B. cinerea were controlled with $1{\times}10^8$ spores/ml of A. strictum BCP applied up to 7 days before inoculation. In a commercial greenhouse, application of A. strictum BCP exhibited the similar control efficacy with fungicide procymidone (recommended rate, $500{\mu}g/ml$) against strawberry gray mold. These results indicate that A. strictum BCP could be developed as a biofungicide for Botrytis diseases under greenhouse conditions.

• Journal of Ginseng Research
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• v.6 no.1
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• pp.38-45
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• 1982

To determine the optimum light intensity for growth of ginseng plants, change of temperature, moisture content in son, occurrence alternaria blight, defoliation rate, chlorophyll contents, and growth of shoots and roots were investigated under different light intensity such as 5%, 10%, 20% and 30% light transmittance rare(L.T.R.). The results obtained were as follows. 1. Maximum temperature under the shading was increased as the increase of light intensity, whereas soil moisture content decreased 2. As the increase of light intensity, stem and Peduncle length, leaf area, and chlorophyll contents decreased significantly but length and width of the leaf was not significant, while stem diameter, special leaf weight and chlorophyll a/chl. b ratio increased 3. Stem color was shown dark purp!e as the increase of light intensity. 4. Photosynthesis during the day was highest at 9 A.M. and decreased as time passed in all plots. The means of photouynthesis during the day showed in the order of 20%, 10%, 30%, 5% L.T.R., and optimum light intensity for highest photosxthesis was 18.4% L.T.R. by theoritical equation. 5. It was showed a tendency that alternaria leaf blight of ginseng plants was increased as the increase of light intensity. 6. Defoliation rate of ginseng plants was increased as the increase of light intensity, especially all plants were defoliated by late June without shading. 7. Yield percentage of the rear line was increased as the increase of light intensity. Root weight per plant showed in the order of 20%, 10%, 30%, 5% L.T.R., and optimum light intensity for the best yield was 18.5% L.T.R. by theeritical equation.

• The Plant Pathology Journal
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• v.21 no.3
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• pp.293-296
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• 2005

A leaf blight caused by a species of Phytophthora was found on fatsia plants (Fatsia japonica Decne et Planch.) growing in an apartment garden in Daegu, Korea in late April to May, 2003. The species of Phytophthora isolated from the diseased plants produced sporangia and sex organs on V8 juice agar medium. Sporangia were papillate, ovoid to subspherical, and caducous with a pedicel. The dimensions of the sporangia were $31.2-46.8\times23.4-33.2{\mu}m$ in range, $39.6\pm4.1\times28.3\pm2.8{\mu}m$ in $average{\pm}standard$ deviation, I/b ratio approximately 1.40, with papillae about $3.6{\mu}m$ high, and pedicels $0.9­5.8{\mu}m$ long. Oogonia were spherical, $25.0-32.5{\mu}m$ in range with an average of $28.2\pm2.3{\mu}m$ in diameter. Antheridia were predominantly paragynous, globose to ovoid, $8.8-13.8\times7.5-10.0{\mu}m$ with an average of $10.9\pm1.2 \times9.2\pm1.1{\mu}m$. Oospores in the oogonia were aplerotic or plerotic, and $20.0-25.0{\mu}m$ in diameter with an average of $23.5\pm1.5{\mu}m$. Pathogenicity of the isolate was confirmed on detached leaves of fatsia. The disease was observed only in April and May of 2003 when the weather was unusually wet. It then diminished with increase of temperature in the year and did not appear again on the same plants in 2004. Thus, the fungus appeared to be a relatively weak pathogen of fatsia.

• Korean Journal Plant Pathology
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• v.1 no.3
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• pp.169-172
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• 1985

Natural sclerotia of Rhizoctonia solani causing rice sheath blight were inoculated at 10 day intervals from June 15 to July 15 in paddy field, Icheon, Korea. Percentage of infected stems, top lesion height and percentage of. lesion height vs. plant height were higher in the early inoculated plots than in the late inoculated ones. However, rio significant differences among inoculation dates of sclerotia were found on the basis of degree of damage at maturing stage and rice yield. These results suggest that the time of initial symptom appearance under the same inoculum potential may not affect the damage of rice plants by the fungus.

• Molecules and Cells
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• v.28 no.4
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• pp.321-329
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• 2009

Rapid production of nitric oxide (NO) and reactive oxygen species (ROS) has been implicated in the regulation of innate immunity in plants. A potato calcium-dependent protein kinase (StCDPK5) activates an NADPH oxidase StRBOHA to D by direct phosphorylation of N-terminal regions, and heterologous expression of StCDPK5 and StRBOHs in Nicotiana benthamiana results in oxidative burst. The transgenic potato plants that carry a constitutively active StCDPK5 driven by a pathogen-inducible promoter of the potato showed high resistance to late blight pathogen Phytophthora infestans accompanied by HR-like cell death and $H_2O_2$ accumulation in the attacked cells. In contrast, these plants showed high susceptibility to early blight necrotrophic pathogen Alternaria solani, suggesting that oxidative burst confers high resistance to biotrophic pathogen, but high susceptibility to necrotrophic pathogen. NO and ROS synergistically function in defense responses. Two MAPK cascades, MEK2-SIPK and cytokinesis-related MEK1-NTF6, are involved in the induction of NbRBOHB gene in N. benthamiana. On the other hand, NO burst is regulated by the MEK2-SIPK cascade. Conditional activation of SIPK in potato plants induces oxidative and NO bursts, and confers resistance to both biotrophic and necrotrophic pathogens, indicating the plants may have obtained during evolution the signaling pathway which regulates both NO and ROS production to adapt to wide-spectrum pathogens.