• Korean Journal Plant Pathology
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• v.12 no.1
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• pp.72-79
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• 1996

보리로부터 분리한 Fusarium sp. BYA-1균주의 감자한천배지 배양체로부터 여러 식물병원곰팡이에 길항력을 나타내는 세 개의 항생물질을 분리하였다. 추출한 세 개의 항생물질은 silica gel관 크로마토그래피와 분취 HPLC, 그리고 Phytolhthora capsici 검정을 이용하여 정제하였다. 이들 분리한 항생물질들을 동정하기 위하여 융점 결정, 자외선흡광법, 질량분석 및 핵자기공명법 등의 기기분석을 실시하였다. 그 결과, 세 개의 항진균성 항생물질들은 fusarielin A, enniatin B, 그리고 enniatin B\ulcorner으로 각각 동정되었다. 분리한 세 개의 물질 중 fusarielin A가 공시된 곰팡이에 가장 강한 항균활성을 나타내었으며, 최소저해농도는 40$\mu\textrm{g}$/ml이하였다. Fusarium속 균주가 구조적으로 다른 두 종류의 항진균성 항생물질인 fusarielin A와 enniatins을 동시에 생성한다는 것은 본 논문에서 처음으로 보고하는 것이다.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.594-597
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• 1998

The optimal quantity of inoculum was determined to screen resistance of garlic cultivars against Sclerotium cepivorum and 30 cultivars was tested. The growth of the pathogen in detached roots, Disease incidence was increased when the inoculum density was raised form 10 to 100 sclerotia. The optimal inoculum density to differentiate resistance or susceptibility of garlic cultivars was seemed to be 50 sclerotia. The cultivars collected from England, Japan, Nepal and Turkey, and cultivars such as common red, PI1356104 and PI135693 were less than the other cultivars in their disease incidence. The growth of S. cepivorum in detached roots varied from 23 to 33 mm according to garlic cultivars. There was no relationship between the disease incidence and the growth in detached roots. The sclerotial germination was increased significantly when root extract was extract was added. The addition of only distilled water resulted in 13% germination, but the addition of 0.25 g of root extract in 100 ml distilled water resulted in more than 85% germination. There was no difference in the stimulation of sclerotial germination among cultivars which showed different resistance.

• Korean Journal Plant Pathology
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• v.14 no.2
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• pp.130-135
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• 1998

This study was carried out to detect cymbidium mosaic potexvirus (CymMV) and odontoglossum ringspot tobamovirus (ORSV) in cultivated orchid plants in Korea. The standard double antibody sandwich enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR) were carried out for detection of the viruses in the collected orchid samples. ELISA was suitable for massive-scale diagnostic method for virus detection in orchids. RT-PCR was rapid, time-saving and reliable detective method, and detection limit data showed that RT-PCR was 103 times more sensitive than ELISA. Of the 321 individual orchids representing 5 orchids genera tested by the ELISA, CymMV and ORSV were detected in 15.6% and 22.4%, and mixed infection of the both viruses with 4.9%, respectively. Of the Cymbidium plants tested, cultivated plants showed 52.5% virus infection rate with either CymMV or ORSV and both viruses.

• Korean Journal Plant Pathology
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• v.2 no.2
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• pp.89-95
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• 1986

The five short-chain fatty acids such as isobutyric(C-4), butyric(C-4), isovaleric(C-5), valeric(C-5) and caproic (C-6) acids obtained from the extract of common purslane showed wide antifungal spectra against spore germination and mycelial growth of the twenty five phytopathogenic fungi tested in vitro, although there were differences in antifungal potency among them. The antifungal potency of each fatty acid varied significantly against different fungi in spore germination and mycelial growth. The seventeen fungi used for spore germination test and the sixteen fungi used for mycelial growth test can be divided into three groups depending upon differences in minimal inhibitory concentration of each fatty acid for them, respectively. Caproic acid was significantly more toxic to germination than to mycelial growth of the test fungi, while the other four fatty acids did not show such a significant differences in toxicity with a few of exceptions as shown in valerie acid. The longer the chain-length of fatty acid was, the higher the antifungal potency was shown. The normal fatty acids such as butyric and valerie acid were more toxic than their isomers to spore germination and mycelial growth of the test fungi. Each fatty acid was more toxic to spore germination of obligate parasites and some of facultative parasites, and mycelial growth of facultative parasites than to spore germination and mycelial growth of saprophytes, respectively.

• Research in Plant Disease
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• v.17 no.2
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• pp.161-168
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• 2011

To establish simple and reliable screening method for resistant radish to Plasmodiophora brassicae Woron. using soil-drenching inoculation, the development of clubroot on radish seedlings inoculated with P. brassicae GN-1 isolate according to several conditions such as inoculum concentration, plant growth stage and incubation period after inoculation was studied. To select resistant radish against clubroot, 10-day-old seedlings were inoculated with P. brassicae by drenching the roots with the spore suspension of the pathogen to give $1{\times}10^9$ spores/pot. The inoculated seedlings were incubated in a growth chamber at $20^{\circ}C$ for 3 days then cultivated in a greenhouse ($20{\pm}5^{\circ}C$) for 6 weeks. Under the optimum conditions, 46 commercial cultivars of radish were tested for resistance to YC-1 (infecting 15 clubroot-resistant cultivars of Chinese cabbage) and GN-1 (wild type) isolates of P. brassicae. Among them, thirty-five cultivars showed resistance to both isolates and one cultivar represented susceptible response to the pathogens. On the other hand, the other cultivars showed different responses against the tested P. brassicae pathogens. The results suggest that this method is an efficient system for screening radish with resistance to clubroot.

• Research in Plant Disease
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• v.20 no.2
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• pp.119-125
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• 2014

Root-knot nematodes represent a significant problem in cucumber, causing reduction in yield and quality. To develop screening methods for resistance of cucumber to root-knot nematode Meloidogyne incognita, development of root-knot nematode of four cucumber cultivars ('Dragonsamchuk', 'Asiastrike', 'Nebakja' and 'Hanelbakdadaki') according to several conditions such as inoculum concentration, plant growth stage and transplanting period was investigated by the number of galls and egg masses produced in each seedling 45 days after inoculation. There was no difference in galls and egg masses according to the tested condition except for inoculum concentration. Reproduction of the nematode on all the tested cultivars according to inoculum concentration increased in a dose-dependent manner. On the basis of the result, the optimum conditions for root-knot development on the cultivars is to transplant period of 1 week, inoculum concentration of 5,000 eggs/plant and plant growth stage of 3-week-old in a greenhouse ($25{\pm}5^{\circ}C$). In addition, under optimum conditions, resistance of 45 commercial cucumber cultivars was evaluated. One rootstock cultivar, Union was moderately resistant to the root-knot nematode. However, no significant difference was in the resistance of the others cultivar. According to the result, we suggest an efficient screening method for new resistant cucumber to the root-knot nematode, M. incognita.

• Research in Plant Disease
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• v.7 no.1
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• pp.20-24
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• 2001

As stand-missing rate (SMR) of ginseng plants in fields are directly related to the ginseng root rot, the forecasting model for the root rot progress in ginseng fields was developed, using the estimated SMRs by disease incidence (DI) of ginseng seedling in the soil-indexing bioassay and the estimate of DI derived from soil environmental factors or rhizoplane microflora. For fitness analysis of the forecasting model, simple correlation and linear regression between SMRs at different planting ages in fields and their estimates by 3 factors of the model were evaluated.The SMR estimated from the factor of DI in the bioassay had much higher fitness to the SMR observed in fields than that from the factors of soil environments and rhizoplane microflora. The estimated SMRs in young and aged ginseng fields by DI in the bioassay were significantly correlated with the observed SMRs in 3- and 5-year-old ginseng fields, respectively (p=0.01). this implicates that indexing preplanting field soils with the forecasting model using DI in the bioassay can provide an information to determine the suitability of the fields for ginseng cultivation, and that indexing cultivating field soils can be helpful to determine the time of harvesting to reduce further yield loss by root rot in continuous cultivation in the next year.

• Research in Plant Disease
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• v.17 no.3
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• pp.288-294
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• 2011

Rice bakanae disease, caused by the fungus Fusarium fujikuroi, is one of the most important rice diseases and distributed widely in Asia. Resistance screening system in rice field had been established. However, the evaluation results of the system vary according to the environmental conditions when the test is conducted. To develop precise and rapid evaluation method of disease resistance of rice to bakanae disease, in vitro screening system was attempted in this study. The six cultivars namely, 'Nampyeongbyeo', 'Junambyeo', 'Chucheongbyeo', 'Samcheonbyeo', 'Odaebyeo' and 'Hwasinbyeo' were tested. They were planted onto MS agar medium (10 ml) in test tube ($450\;mm{\times}{\phi}30\;mm$) and incubated at $25^{\circ}C$ and $28^{\circ}C$ in growth chamber under 12 hr light condition. Symptoms of over growth appeared a few days after seeding and then seedling were withered 2-3 weeks after over growth. The disease symptoms such as leaf dryness on top of rice were appeared in the 'Nampyeongbyeo' from 28 days at the concentration of $10^5$ spores/ml culturing at $28^{\circ}C$ and then withered completely 35 days after seeding. Whereas the other varieties withered entirely 19-23 days after seeding. Using the in vitro seedling screening method, 72 rice varieties were investigated to select resistant cultivar. Finally, two resistant cultivars ('Nampyeongbyeo' and 'Inwolbyeo') and seven moderately resistant cultivars ('Hwadongbyeo', 'Seokjeongbyeo', 'Samgwangbyeo', 'Sampyeongbyeo', 'Nonghobyeo', 'Heukjinjubyeo' and, 'Joanbyeo') were selected. If in vitro seedling screening method was used for evaluation of bakanae disease resistance, it would be completed within 35 days after sowing of rice seed.

• Research in Plant Disease
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• v.17 no.1
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• pp.19-24
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• 2011

It was identified as a sharp eyespot (Rhizoctonia cerealis) that the isolates from abnormal symptoms in wheat that showed yellowing leaves, necrotic spot on stem base and dead tillers. These isolates have slower growth property and fewer mycelia than Rhizoctonia solani AG-1(1A) (KACC 40106). They showed binuclear cell, same media cultural and DNA characteristics to R. cerealis. They caused same symptoms on leaves and stem base appeared in artificial inoculation test, comparing to diseased wheat fields and also affect to maturing of kernels. They have optimal growth temperature and acidity on the artificial media as $20{\sim}25^{\circ}C$ and pH 5~7, respectively. In the investigation of varietal resistance of Korean winter cereal crops to sharp eyespot, there was no resistant in wheat cultivars that all materials infected over 20% diseased ratio. 12 cultivars including 'Anbaekmil', however, considered to moderate resistance with 20 to 30% infection ratio. The others crops using in feeding, whole crop barley, oat, rye and triticale were resistant below 15% diseased degree except the rye that showed over 50% infection rate. It was the first evaluation to sharp eyespot resistance for the Korean feeding crop cultivars. Most tested Korean barley cultivars for malting and food were moderate and susceptible to the sharp eyespot. Only 3 hulled barley, 'Tapgolbori', 'Albori' and 'Seodunchalbori', showed resistance with less than 10% diseased ratio. All tested naked barley cultivars showed susceptible response to the disease.

• Research in Plant Disease
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• v.18 no.4
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• pp.370-375
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• 2012

Ninety two pepper (Capsicum annuum L.) cultivars were screened for resistance to two common species of root-knot nematodes, Meloidogyne incognita and M. arenaria. All 92 pepper cultivars were resistant to M. arenaria (0-3 eggmass/plant) but were susceptible to M. incognita (76-678 eggmass/plant). Susceptibility to M. incognita were slightly differed; 'Geomok' and 'Shintaepung' had relatively less eggmass (<100 eggmass/plant) when compared to those 29 very susceptible culivars such as 'Bulggotcheoreum' (>300 eggmass/plant). Therefore, pepper is highly recommended as a high-valued rotation crop to only those greenhouses infested with M. arenaria, but should restrict for M. incognita.