• Korean journal of applied entomology
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• v.20 no.2 s.47
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• pp.107-111
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• 1981

Effect of light and pH on mycelial growth and sporangium formation of Phytophthora capsici Leon, causal fungus of fruit rot of red pepper was carried out on culture media. The maximum mycelial growth occurred at $25^{\circ}C$ and pH 6.0 on potato sucrose agar. The fungus did not produce sporangia readily in dark condition. However, abundant sporulation occurred by illuminating continuous cool white fluorescent light with 2000 lux for 48 hrs. at $20{\pm}2^{\circ}C$. Oat meal agar was one of the best media for sporangia formation.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.186-186
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• 2022

Phytophthora root and stem rot (PRSR) and wildfire disease (WFD) of soybean are frequently observed in the field of South Korea. The most environmentally friendly way to control PRSR and WFD is to use soybean varieties with resistance to Phytophthora sojae (P. sojae) and Pseudomonas amygdali pv. tabaci. Plant germplasm is an important gene pool for soybean breeding and improvement. In this study, hundreds of soybean accessions were evaluated for the two pathogens, and genome-wide association analyses were conducted using 104,955 SNPs to identify resistance loci for the two pathogens. Of 193 accessions, 46 genotypes showed resistance reaction, while 143 did susceptibility for PRSP. Twenty SNPs were significantly associated with resistance to P. sojae on chromosomes (Chr.) 3 and 4. Significant SNPs on Chr.3 were located within the known Rps gene region. A region on Chr. 4 is considered as a new candidate resistance loci. For evalation of resistance to WFD, 18, 31,74,36 and 34 genotypes were counted by a scale of 1-5, respectively. Five SNP markers on Chrs 9,11,12,17 and 18 were significantly associated with resistance to P. amygdali pv. tabaci. The identified SNPs and genomic regions will provide a useful information for further researches and breeding for resistance to P. sojae and P. amygdali pv. tabaci.

• The Plant Pathology Journal
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• v.38 no.6
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• pp.673-678
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• 2022

Vapours from origanum oil (O) and thyme oil (T) were applied to the four soil-borne strawberry pathogens Fusarium oxysporum f. sp. fragariae, Colletotrichum fructicola, Lasiodiplodia theobromae, and Phytophthora cactorum, causing Fusarium wilt, anthracnose, dieback, and Phytophthora rot, respectively. Increasing T vapour doses in the presence of O vapour strongly inhibited mycelial growths of the four pathogens and vice versa. When mycelia of F. oxysporum f. sp. fragariae and P. cactorum exposed to the combined O + T vapours were transferred to the fresh media, mycelial growth was restored, indicating fungistasis by vapours. However, the mycelial growth of C. fructicola and L. theobromae exposed to the combined O + T vapours have been slightly retarded in the fresh media. Prolonged exposure of strawberry pathogens to O + T vapours in soil environments may be suggested as an alternative method for eco-friendly disease management.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.128.1-128
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• 2003

A leaf blight disease was found on Fatsia japonica plants growing in the first author's apartment garden in May, 2003. Major symptoms were leaf blight and petiole rot. A species of Phytophthora was isolated from the lesions. The isolate readily produced sporangia and sex organs on V8 juice agar plates. Sporangia were papillate, ovoid to subspherical and caducous with a pedicel. Sporangia were 33.6-38.4 ${\times}$ 33.6$\mu\textrm{m}$ with 1/b ratio approximately 1.14, papillae 4-5$\mu\textrm{m}$ high, pedicels also 4-5$\mu\textrm{m}$ long. Oogonia were spherical, 28.8$\mu\textrm{m}$ in diameter. Antheridia were globose, 14.4$\mu\textrm{m}$ in diameter and mating with oogonia paragynously. Mycelia grew best at 30$^{\circ}C$ and did not grow at 35$^{\circ}C$ or above, and at 5$^{\circ}C$. The morphological characteristics conformed to P. cactorum (Leb. And Cohn) Schroeter.

• Research in Plant Disease
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• v.22 no.3
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• pp.198-201
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• 2016

Recently, severe dieback of apple tree has occurred in the apple orchards of Chungbuk province. Dieback rate and its casual agents have been investigated on the Chungbuk province apple orchards in 2013-2015. Out of 29,265 apple trees in the 27 orchards throughout Chungbuk province, 4,000 apple trees (13.7%) showed dieback symptoms. The causes of dieback were Phytophthora rot (50.4%), violet root rot by Helicobasidium sp. (27.1%), rodents (10%), white root rot by Rosellinia sp. (6.3%), and freezing injury (6.3%). Compared to previous reports published in 1995 and 2006, Phytophthora rot was the most dominant disease, which is thought to be due to high temperature during growing season and the increase of lowland cultivation. Results of this study will be useful to establish of the management strategy of apple tree dieback that has been increased recently.

• Korean Journal of Medicinal Crop Science
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• v.10 no.3
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• pp.155-161
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• 2002

Using semi-selective (SS-) and selective (Jee-) medium, we identified the pathogens isolated from the symptomatic plants and soils collected from different locations, such as Suwon, Andong, and Youngju, as P. drechsleri, which is Phytophthora root rot causal agent of A. macrocephala. At $25^{\circ}C$, these isolates were grown faster on 10% V8A (V8 juice agar) medium than on PDA (potato dextrose agar) with hyphal swelling, but no growing was observed at below $5^{\circ}C$ and over $40^{\circ}C$. In order to identify the pathogenicity of each isolate, seedlings of A. macrocephala were inoculated with mycelium -zoospore suspended inoculum, which was prepared by culturing on 10% V8A medium and homogenizing in distilled water. By this method, wide ranges of pathogenicity were observed as follows; $5.0%{\sim}26.4%$ of disease severities concerning the lesion areas of the top plants and $23.5%{\sim}72.2%$ of disease incidences. Therefore, this was considered as a efficient method to identify the pathogenicity of P. drechsleri in large scale screening. P-A200073, isolated from soils in Andong, and P-9755, from the root of symptomatic plant of A. macrocephala in Suwon, showed the highest degree of pathogenicity to the seedlings. By these isolates, lesion areas and disease incidences of the inoculated seedlings were occurred $26.4%{\sim}63.2%$ and $25.1%{\sim}72.2%$, respectively. However, no symptoms were observed in uninoculated control. Same pathogens were reisolated from roots and lower stems of the inoculated plants, but not from leaves.

• The Plant Pathology Journal
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• v.25 no.3
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• pp.263-269
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• 2009

Bacterial wilt, Fusarium wilt and Foot rot caused by Ralstonia solanacearum, Fusarium oxysporum, and Phytophthora capsici respectively, continue to be severe problems to tomato, potato and black pepper growers in Vietnam. Three bio-products, Bacillus vallismortis EXTN-1 (EXTN-1), Bacillus sp. and Paenibacillus sp. (ESSC) and Bacillus substilis (MFMF) were examined in greenhouse bioassay for the ability to reduce bacterial wilt, fusarium wilt and foot rot disease severity. While these bio-products significantly reduced disease severities, EXTN-1 was the most effective, providing a mean level of disease reduction 80.0 to 90.0% against bacterial wilt, fusarium wilt and foot rot diseases under greenhouse conditions. ESSC and MFMF also significantly reduced fusarium wilt, bacterial wilt and foot rot severity under greenhouse conditions. Bio-product, EXTN-1 with the greatest efficacy under greenhouse condition was tested for the ability to reduce bacterial wilt, fusarium wilt and foot rot under field condition at Song Phuong and Thuong Tin locations in Ha Tay province, Vietnam. Under field condition, EXTN-1 provided a mean level of disease reduction more than 45.0% against all three diseases compared to water treated control. Besides, EXTN-1 treatment increased the yield in tomato fruits 17.3% than water treated control plants.

• Journal of Ginseng Research
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• v.9 no.2
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• pp.163-169
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• 1985

The efficacy of fungicides was compared for control of root rot as well as leaf blight caused by Phytophthora cactorum on ginseng plants. Growth of P. cactorum in rlitro was completely or highly inhibited by metalaxyl, tetracyclin, captafol, carbendazim, and thiophanate + thiram. In field trials, the disease was significantly reduced not only in the root rot but also in the leaf blight when metalaxyl was applied at 4.17 mg a.i. per plant for soil drenching and 1.25 mg a.i. for foliage application. Also captafol was effective on control of the leaf blight but its effect was inferior to that of metalaxyl. Metalaxyl lost its effectiveness in vivo between the 5th and 7th week after soil wren ching. Phytotoxicity was, however, observed on 2 years old ginseng plants when metalaxyl was drenched at 8 mg a.i. while no phytotoxic symptom was developed on 2 years old ginseng plants at 4k mg a.i. and 3 years old at 16 mg a.i. per plant, respectively.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.04a
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• pp.41.2-41
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• 1999

• Proceedings of the Korean Society of Crop Science Conference
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• 2001.05a
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• pp.208-209
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• 2001