• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.408-412
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• 1998

In order to illustrate the role of conidia of Mycosphaerella nawae as a secondary inoculum in nature, pseudothecial development on persimmon leaves was investigated microscopically. The fungal ascospores have been believed as the primary or only inoculum source in nature, however, pseudothecia were readily formed on persimmon leaves infected naturally and artificially by conidia. The pseudothecia of M. nawae were found to form in the tissues of infected leaves while the leaves were still hanging on the trees. The size of pseudothecia were approximately 51.0~122.4$\times$51.0~112.2 ${\mu}{\textrm}{m}$ (82.8 $\times$72.5 ${\mu}{\textrm}{m}$in average), the shapes were spherical, ovoid or occidental pear type. The sizes of asci were approximately 30.6~61.2$\times$8.2~10.2 ${\mu}{\textrm}{m}$(46.6$\times$9.4 ${\mu}{\textrm}{m}$ in average) and the shapes were cylinder or banana. The ascospores were mostly spindle type, and the sizes were 10.2~12.2$\times$3.1~4.1 ${\mu}{\textrm}{m}$ (11.4$\times$3.2 ${\mu}{\textrm}{m}$ in average)-like. The pseudothecial formation was initiated before defoliation and morphological characteristics of the pseudothecia, ascus and ascospores on the infected leaves were fully illustrated in this study. Results indicated that conidia of M. nawae induce circular leaf spot of persimmon as much as ascospores, and might play an important role of the disease epidemics in nature.

• Korean Journal Plant Pathology
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• v.12 no.4
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• pp.395-401
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• 1996

국내의 고추, 사과, 포도, 스타티스(statice)에서 분리한 Glomerella cingulata 균주들의 병원성과 체세포화 합성군(vegetative compatibility group : VCG)과의 관계를 조사하였다. 사과, 포도, 스타티스에서 분리된 균주들은 전기주에 모드 병원성을 나타내었으나 고추에는 병원성이 없었다. 한편, 고추에서 분리된 균주들은 무상처접종시 병원성을 나타내지 못하였다. Nitrate nonutilizing(nit) mutant는 1.5%의 KClO\ulcorner을 첨가한 최소배지에서 선발하였다. nit mutnat들은 nit1, nit2, nit3, nitM의 4가지 표현형 중 하나에 속하였다. VCG는 표현형이 다른 nit mutan간의 대치배양을 통해 결정하였는데 사과, 포도, 스타티스에서 분리한 균주들간에는 같은 VCG를 나타낸 반면 고추에서 분리된 균주들은 다른 VCG로 나타났다. 따라서 G. cingulata 균주들의 체세포화합성은 병원성과 밀접하게 관련되어 있음을 알수 있었다. 또한 동일한 VCG에 속하며 기주가 다른 균주들의 대치배양시 heterokaryon을 형성했으나 자낭을 형성하지는 않았다.

• Korean journal of applied entomology
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• v.12 no.3
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• pp.121-124
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• 1973

From the new rice variety Tong-il, disease symptoms similar to Fusarium leaf spot reported in Japan was observed in Korea. Causal organism was isolated and identified as Fusarium nivale causing Fusarium leaf spot through the study of conidia shape, ascus formation on diseased spot, and ascospore. These results also showed good agreement with that of other investigators. Under the field condition, marked occurrence of this disease has observed by heavy nitrogen application. The optimum temperature for the growth of this fungus was $24^{\circ}C$.

• Research in Plant Disease
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• v.10 no.4
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• pp.209-216
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• 2004

The circular leaf spot of persimmon is occurred almost every place where persimmon is cultivated, especially the disease outbreak severely in southern part of Korea. The disease reveals unusually long incubation period after pathogen invade into leaf tissue and no practical control measure is available once the symptom has appeared. Most of the farmers just follow the suggested spray schedules calculated on the basis of weather condition of ordinary years. Therefore the damages due to circular leaf spot greatly differ year after year. In this article, we tried to describe and summarized the investigation on the circular leaf spot pathogen, Mycosphaerella nawae, related to disease outbreak such as overwintering of pathogen, inoculum formation and spread, incubation period after infection, and secondary inoculum. With the summary of these results, we suggest the disease cycle of circular leaf spot of persimmon. The pathogen overwinters in diseased leaves as mycelial form or pseudoperithecial premodium. The pseudoperitheria become matured in spring as the temperature raise and forms asci and ascospores. The maturation of pseudoperithecia are closely related to the temperatures during March and early April. The ascospores completely mature in early May and the ascospores released when the pseudoperithecia absorbed enough moisture after rainfall. The release of ascospores are diverse greatly with the variation of maturity of pseudoperithecia. Generally the spore start to release from middle of May to early of July. Duration of ascospore release is depend on the weather condition of particular year, especially amount and number of precipitation. The ascospores produced from pseudoperithecia is known to the only inoculum for circular leaf spot disease. But according to the results obtained from our investigations, the conidia formed on the lesions which incited by natural infection. This conidia are infectious to persimmon leaves and formed identical symptom as natural infection. The time of producing secondary inoculum of circular leaf spot of persimmon is considered too late to develop new disease. Generally the importance of secondary inoculum is low but the conidia produced in early September are competent to develop new disease and new infection also significantly affect to harvest of persimmon. The importance of circular leaf spot disease is recognized well to farmers. The approaches to control of the disease should be initiated on the basis of the knowledges of inoculum dynamics and ecology of disease development. The forecasting system for circular leaf spot is need to be developed.

• The Korean Journal of Mycology
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• v.26 no.2 s.85
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• pp.287-292
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• 1998

The perfect state of Bipolaris coicis, causing leaf blight of Job's tears, was in duced under in vitro conditions. Eighty nine isolates of the fungus were collected from 17 locations in Korea from 1994 to 1996. They were crossed on Sach's nutrient agar, on which a piece of rice straw was placed, and incubated at $25^{\circ}C$. Pseudothecia were produced only by certain combinations of compatible isolates. Although pseudothecia were usually produced on rice straw two weeks after incubation, asci and ascospores were observed only in a few pseudothecia examined. The pseudothecia were black and globose with protruding ostiolar beaks. The locules were filled with a mass of hyaline and filamentous pseudoparaphyses. Asci were cylindrical to clavate and straight or slightly curved. The ascus wall was bitunicate with short stipes. Ascospores were filiform, hyaline, and arranged parallel to slightly coiled in the asci, measuring $143-166.4{\times}2.6-3.8\;{\mu}m$. Perfect state of the fungus was identified as Cochliobolus nisikadoi (Tsuda, Ueyama & Nishihara Alcorn), based on the morphological characteristics.