• The Plant Pathology Journal
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• 제17권3호
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• pp.154-158
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• 2001

A severe root rot of kiwifruit caused by a species of Phytophthora occurred in 1-to 5-year-old vines at the south coast region of Korea in 1997. Infected vines exhibited leaf chlorosis, scorch and defoliation, root and stem rot, and eventual death. The disease was relatively severe in poorly drained lowlands, of which 19 out of 23 fields were damaged by the disease. Meanwhile, only one among 58 upland fields was infected by the disease. Incidence of infected vines reached over 80% in heavily damaged fields and a species of Phytophthora was isolated from inner tissues of roots, stems, and rhizosphere soils of the plants. The causal pathogen was identified as P. drechsleri based on its mycological characteristics. Pathogenicity of the fungus was confirmed by artificial inoculation to seedlings of kiwifruit 'Hayward'. The pathogen was re-isolated from the inoculated plants showing symptoms similar to those observed in the fields. Root rot of kiwifruit caused by P. drechsleri has not been reported previously in Korea.

• The Plant Pathology Journal
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• 제25권2호
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• pp.113-120
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• 2009

Microscopic study of chili pepper (Capsicum annuum L.) infected with Phytophthora capsici, causing Phytophthora blight of chili pepper, was conducted to compare histological and cytological characteristics in the root and stem of susceptible (C. annuum cv. Bugang) and resistant (C. annuum cv. CM334) pepper cultivars. The susceptible pepper roots and stems were extensively penetrated and invaded by the pathogen initially into epidermal cells and later cortical and vascular cells. Host cell walls adjacent to and invaded by the infecting hyphae were partially dissolved and structurally loosened with fine fibrillar materials probably by cell wall-degrading enzymes of the pathogen. In the resistant pepper, the pathogen remained on root epidermal surface at one day after inoculation, embedded and captured in root exudation materials composed of proteins and polysaccharides. Also the pathogen appeared to be blocked in its progression at the early infection stages by thickened middle lamellae. At 3 days after inoculation, the oomycete hyphae were still confined to epidermal cells of the root and at most outer peripheral cortical cells of the stem, resulting from their invasion blocked by wound periderms formed underneath the infection sites and/or cell wall appositions bounding the hyphal protrusions. All of these aspects suggest that limitation of disease development in the resistant pepper may be due to the inhibition of the pathogen penetration, infection, invasion, and colonization by the defense structures such as root exudation materials, thickened middle lamellae, wound peridems and cell wall appositions.

• The Plant Pathology Journal
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• 제40권3호
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• pp.299-309
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• 2024

The rice blast disease, caused by the fungal pathogen, Magnaporthe oryzae (syn. Pyricularia oryzae), poses a significant threat to the global rice production. Understanding how this disease impacts the plant's microbial communities is crucial for gaining insights into host-pathogen interactions. In this study, we investigated the changes in communities of bacterial and fungal endophytes inhabiting different compartments in healthy and diseased plants. We found that both alpha and beta diversities of endophytic communities do not change significantly by the pathogen infection. Rather, the type of plant compartment appeared to be the main driver of endophytic community structures. Although the overall structure seemed to be consistent between healthy and diseased plants, our analysis of differentially abundant taxa revealed the specific bacterial and fungal operational taxonomic units that exhibited enrichment in the root and leaf compartments of infected plants. These findings suggest that endophyte communities are robust to the changes at the early stage of pathogen infection, and that some of endophytes enriched in infected plants might have roles in the defense against the pathogen.

• 미생물학회지
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• 제11권1호
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• pp.19-30
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• 1973

The sweet potatoes infected with witches'-broom disease were collected in the growing fields in Jeon-bug area, Korea. As a possible control plant, Ipomoea batatas L.var. Suwon 147 was selected. The pathogen was identified by various methods ; such as mechanical transmission, antibiotic reactions and electron microscopy. In the results attained the author believed the pathogen of the sweet potato infected with witches' broom to be a mycoplasma-like organism. the results are as follows : 1. Mycoplasma-like bodies were occurred in the phloem region of the sweet potatoes infected with witches'-broom and its particles were sized in the range of about 200-2,500m.mu.. The membrane of the pathogen was observed to be made of an unit. 2. Responsibilities to the antibiotices were sensitive in case of tetracycline and terramycin, and root dipping method showed remarkable than foliage spray. 3. The infection was developed by the grafting transmission but by the insects, Myzus persicae and Cicadella viridis. 4. rosette, witches'-broom, stunt, yellowish, mosaic and necrosis were observed as the symptomps of the disease.

• 한국응용곤충학회지
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• 제19권4호
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• pp.228-233
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• 1980

The infection rate of soybean black root rot disease caused by Calonectria crotalariae was about $14\%$. The isolated fungi from the infected soybean roots and stems were Calonectria crotalariae, Fusarium solani, F. roseum, Phomopsis sojae, Pythium aphanidermatum, Rhizoctonia solani and Macrophomina sp. Among them, C. crotalariae was the most virulent pathogen under the laboratory conditions. Mycelial growth and microsclerotial formation were good on PSA containing 1000cc of water, 100g of potato and 20g of sugar. Mycelial growth, sporulation and microsclerotial formation were good on sterilized root. Perithecial formation was better in the dark condition than in the light. Survival of macroconidia was not available between $0\~25\%$ soil water content. Microsclerotia and mycelium in infected plant debris were survived for 4 months at to $8\%\;50\%$ soil water content. The plant height, when inoculated with $1.2\%$ inoculum density, reached approximately half of uninoculated plants. Disease severity was much higher at nonsterilized soil than completely sterilized soil. It was determined that the host range of this pathogen includes soybean, peanut, green bean and red bean.

• 한국균학회지
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• 제47권4호
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• pp.427-435
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• 2019

최근 경남 산청, 함양의 딸기 재배지역의 육묘하우스에서 딸기 묘목의 뿌리와 관부를 썩게 하고 지상부의 생육을 저해하며 최종적으로 식물체를 시들게 하는 뿌리썩음병(가칭)증상이 발생하였다. 이러한 병반을 나타내는 딸기 식물체 뿌리와 관부로부터 병원균을 분리하고 균학적 특성을 조사하였으며, 유전자 염기서열 분석과 계통학적 분석을 수행하였다. 그 결과, 딸기 육묘과정에서 발생한 뿌리썩음병(가칭)의 병원균은 Neopestalotiopsis clavispora로 확인되었으며, 건전한 딸기 식물체를 대상으로 접종실험을 수행한 결과 딸기에 대한 병원성을 확인하였다. 지금까지 국내에서 N. clavispora에 의한 딸기 뿌리썩음병이 보고되지 않았으므로 본 연구결과를 바탕으로 이병을 딸기뿌리썩음병으로 국내 최초로 보고한다.

• 미생물과산업
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• 제25권2호
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• pp.11-18
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• 1999

전북지방에 만연되고 있는 고구마 위축병에 관한 병원성 검정에 따른 결과는 다음과 같다. 1. 본고구마 위축병의 병원은 mycoplasma-like organism(또는 PPLO)으로서 그 형태는 타원형이며 크기는 200~2500범위이다. 2.항생물질 효과는 oxytetracycline이 가장 효과적이다. 3.전자현미경 관찰 결과 mycoplasma-like bodies 는 엽맥 관세포 속에 밀집되여 있고, 항생물질에 의해 모구조의 파괴현상이 나타난다. 4. 감염경로는 접목전염만이 되고, 즙액전염, 곤충전염에서는 감염이 되지 않았다.

• The Plant Pathology Journal
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• 제17권2호
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• pp.94-100
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• 2001

Roots of Chinese cabbage (Brassica campestris var. chinensis) seedlings infected with Plasmodiophora brassicae were examined by light and electron microscopy to reveal histopathological changes related to pathogenesis in the susceptible host. The pathogen colonized the cortex and partly the stele as well, invading up to the xylem. Gall tissues could be differentiated from the initially infected tissues, involving less compact organization and new vascular development. The infected cells were much hypertrophied, and contained one to several plasmodia. Except cellular hypertrophy, no pathological ultrastructural modification was noted in the infected calls. Infected cytoplasm became dense with ground cytoplasm, inconspicuous central vacuole, and increased cellular organelles such as mitochondria and dictyosomes. There were two types of nuclear states of plasmodium, uninucleate and multinucleate. Both plasmodia were structurally similar, filled with lipid droplets, bounded with envelope, and containing mitochondria, endo-plasmic reticulum, and sometimes small vacuoles. Plasmodial fragmentation, which may be regarded as a way to discharge plasmodial materials into host cytoplasm, commonly occurred, forming plasmodial fragments by outgrowth of plasmodial cytoplasm and regional compartmentalization. Plasmodial fragments were degenerated sometimes followed by forming chains of spherical vesicles especially in the uninucleate plasmodial state. These ultrastructural features indicate the biotrophic nature of the pathogen associated with its pathogenesis in the susceptible host.

• 한국초지조사료학회지
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• 제27권1호
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• pp.37-44
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• 2007

병원균 감염에 의한 식물체내 프롤린과 암모니아의 농도 변화와 그것의 스트레스 생리학적 의미를 구명하기 위하여 Rhizoctonia spp.를 처리 후 라지 펫치에 감염된 잔디의 생육 및 관련 화학적 성분을 감염이 되지 않은 대조구와 비교하였다. 라지 펫치에 감염된 잔디의 뿌리의 건사율은 대조구에 비해 약 30% 증가하였다. 가용성 단백질 농도는 병원균 처리후 6일째 잎의 경우를 제외하고는 라지 펫치 감염에 따른 유의적인 영향이 없었다. 암모니아 농도 역시 라지 펫치에 감염된 잎과 줄기에서 공히 유의적으로 증가하였다. 프롤린 농도는 잎과 뿌리에서 대조구에 비해 각각 3.4 및 4.5배 증가하였다. 이러한 결과들은 잔디에 있어 병원균 감염에 따른 프롤린의 축적은 스트레스 강도를 나타내는 민감한 표지물질로서 의미가 있음을 제시한다.

• Journal of Ginseng Research
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• 제43권1호
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• pp.1-9
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• 2019

Background: Korean ginseng is an important cash crop in Asian countries. However, plant yield is reduced by pathogens. Among the Ilyonectria radicicola-species complex, I. mors-panacis is responsible for root-rot and replant failure of ginseng in Asia. The development of new methods to reveal the existence of the pathogen before cultivation is started is essential. Therefore, a quantitative real-time polymerase chain reaction method was developed to detect and quantify the pathogen in ginseng soils. Methods: In this study, a species-specific histone H3 primer set was developed for the quantification of I. mors-panacis. The primer set was used on DNA from other microbes to evaluate its sensitivity and selectivity for I. mors-panacis DNA. Sterilized soil samples artificially infected with the pathogen at different concentrations were used to evaluate the ability of the primer set to detect the pathogen population in the soil DNA. Finally, the pathogen was quantified in many natural soil samples. Results: The designed primer set was found to be sensitive and selective for I. mors-panacis DNA. In artificially infected sterilized soil samples, using quantitative real-time polymerase chain reaction the estimated amount of template was positively correlated with the pathogen concentration in soil samples ($R^2=0.95$), disease severity index ($R^2=0.99$), and colony-forming units ($R^2=0.87$). In natural soils, the pathogen was recorded in most fields producing bad yields at a range of $5.82{\pm}2.35pg/g$ to $892.34{\pm}103.70pg/g$ of soil. Conclusion: According to these results, the proposed primer set is applicable for estimating soil quality before ginseng cultivation. This will contribute to disease management and crop protection in the future.