豆科牧草 菌核病菌 Sclerotinia trifoliorum Erikss의 交配形 S 菌株의 生活環

嚴在烈 COLLEGE OF AGRICULTURE KYUNGPOOK NATIONAL UNIVERSI 1984 慶北大農學誌 Vol.2 No.-

The recent new finding on the sexual mechanism of Sclerotinia trifoliorum Erikss., the causal fungus of sclerotial rot on forage legumes, alluds another aspect of life cycle of the fungus. This study was conducted to demonstrate the expected behavior of the sclerotia formed on the plants infected by the ascospores of mating type "S" which give rise to the heterothallic strains. The possibility of spermatization by the microconidia of mating type "L" strains, the opposite mating type to the "S", which formed on the diseased plants was demonstrated by the pot experiments. The cultural morphology of the ascospore progeny showed a great variability when two morphologically distinct cultures were crossed. This facts were thought to be more appropriate explanation on the mechanism of new biotype occurrence than the heterokaryosis which has hitherto been asserted. The sclerotia of mating type "S" culture retained fertilization ability for about two months when the sclerotia were kept on the surface of moistened soil in the pots under 15C.

Chitosan이 사과 겹무늬썩음병균 Botryosphaeria dothidea의 생육에 미치는 영향

이승지,엄재열,이용현 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1996 한국미생물·생명공학회지 Vol.24 No.3

고분자물질에 의한 사과 겹무늬썩음병 방제법을 개발함에 있어서 chitosan을 코팅용 소재로 활용하기 위하여, 사과 겹무늬썩음병균인 Botryosphaeria dothidea에 대한 Chitosan의 항진균활성을 고체배양 및 액체배양 조건하에서 검토하였다. Chitosan은 고체배양시 B. dothidea의 균사생장억제, 자라난 균사의 응집, 균사의 팽윤 및 세포의 미세구조의 변화를 유발하였다. 액체배양실험 결과 chitosan은 낮은 농도에서도 강력한 균체생육 억제효과를 보였으며, 1.0mg/ml의 첨가농도에서 90% 이상의 억제효과를 나타내었다. 또한 균사의 신장과정에 영향을 미쳐 균사체의 응집현상이 관찰되었다. 또한 chitosan이 포자의 발아를 지연시켰을 뿐만 아니라 발아관의 형태적 변화를 유발시켰다. 단량체인 glucosamine은 glucosamine은 B. dothidea의 생육저해를 유발하지 않았으며, 항진균 활성은 chitosan polymer에 의한 것임을 알았다. To examine the potential utilization of chitosan, the biodegradable natural ploymer, as a control agent of apple white rot caused by Botryosphaeria dothidea in a new control measure by coating it on the diseased branches, the various antifungal activites of chitosan was investigated. Chitosan showed significant inhibitory effect on the mycelial growth of B. dothidea, along with the morphological changes including hyphal swelling and ultrastructural changes on solid PDA medium. In liquid PD broth medium, the chitosan showed more significant effect on the growth of B. dothidea also forming cell clusters indicating affection on the hyphal extension. The growth of B. dothidea was inhibited more than 90% at the concentration of 1.0 mg/ml. Chitosan also detained the spore germination and induced the morphological change of germ tubes. Glucosamine, monomer of chitosan, did not affect on the growth of B. dothidea indicating the antifungal activity was caused by chitosan polymer.

S-1. Mating Type Mutation in Sclerotinia trifolirum Frikss , the Causal Fungus of the Sclerotial Rot of the Forage Legumes

Uhm, Jae Youl 한국균학회 1985 韓國菌學會誌 Vol.13 No.2

Sclerotinia trifoliorum Erikss. displays dimorphism in spore size, with 4 : 4 segregation of large and small ascospores in each ascus. The two sized spores are arranged in six types of first and second meiotic division. The second meiotic division frequency(mean =20.8%) did not vary significantly among isolates of various sources. This indicated that the dimorphism in spore size was regulated by the same allelic pair in all isolates. The single ascosporic strains derived from the large and small ascospores of an ascus were very similar in morphology, growth rate and pathogenicity. Without exception, however nonpaired cultures from single ascosporic strains derived from small spores (small spore strains) failed to produce apothecia, whereas those from large spores (large spore strains) produced sporulating apothecia but their asci again showed the 4 : 4 segregation for spore size. Mating experiments revealed that the small spore strains are self-sterile but cross-fertile only with the large spore strains. From the mating behavior of the small spore strains, this fungus which has hitherto been known as homothallism was determined to have bipolar heterothallism. The spore size difference was determined to be a pleiotropic expression of mating type allele, since the factors determining mating type and ascospore size were inseparable. The mating types of large and small spore strains were designated as L and S, respectively. Apothecial formation by single large spore strains is due to mutation for mating type and subsequent pairing of parental type and mutated nuclei in the same thallus; therefore, the resulting asci show segregation for spore size as well as mating type mutation, however, occurs in one direction only, from L to S, since the small spore strains are invariably selfsterile. The sexual role of the microconidia was demonstrated for the first time by successful mating in which spermatization of the sclerotia of small spore strains was accomplished using microconidia of large spore strains.

Sclerotinia trifolorum의 Spermatizatino에 관여하는 要因의 檢索 : Ⅰ. 菌의 受精過程 Ⅰ. Course of Fertilization

嚴在烈,金永兌 慶北大學校出版部 1987 慶北大農學誌 Vol.5 No.-

The process of fertilization and changes in anatomical structure of sclerotia during the apothecial formation in Sclerotinia trifoliorum, the causal fungus of sclerotial rot of forage legumes, were investigated. The time of fertilization could be estimated with fair accuracy by the sequencial spermatization of the sclerotia which kept at 15C in saturated moisture. In the case of one strain used in this experiment, fertilization between the sclerotia and spermatia were estimated to take place at around 18days after the sclerotia were placed under the conditions for apothecial induction (15C, saturated moisture). The fertilizable state was maintained for about 45 days and the spermatization thereafter did not induce the apothecial formation. When the sclerotia reached fertilizable state, a number of interwoven hyphal nests were developed within the medulla of sclerotia, regardless of the sexuality of the cultures. Comparing the process of multiplication and growth of the hyphal nests in homothallic and heterothallic culture, they were identified as ascogonium. These ascognia were persisted for about 45 days. This observation was wellcoincided with the duration of fertilizable state elucidated by the sequencial spermatization experiment.

Liquid Metal Embrittlement of Resistance Spot Welded 1180 TRIP Steel: Effect of Electrode Force on Cracking Behavior

Du‑Youl Choi,Ashutosh Sharma,Sang‑Ho Uhm,Jae Pil Jung 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.1

Liquid metal embrittlement (LME) caused cracking of Galvanized transformation induced plasticity steels was investigatedduring resistance spot welding (RSW). Effect of electrode force (3–5 kN) for a weld time of 400, and 800 ms on crack resistanceof TRIP steel was examined in relation to LME phenomenon. The microstructural characteristics of spot weld jointsand LME cracking tendency were investigated using dye penetration tests, optical microscopy, scanning electron microscopytogether with energy dispersive X-ray spectroscopy. It was found that as the electrode force increases, the crack size decreasesdue to a fast increase in crack tip temperature which rises further with more holding time up to 800 ms in high temperaturezone. Least amount of crack size was observed at 5 kN electrode force and 400 ms of welding time. Finally, the experimentalresults have also been simulated by finite element modeling (FEM) to find suitable mechanism of crack formation, and acombination of 4 kN and 400 ms was suggested for the crack free and less thermal deformation in the spot welded TRIP steel.

Contribution Value of Individual Fungicides Constituting a Spray Program in the Control of Apple Fruit Diseases

Lae Hong Cho,Jae Youl Uhm 한국농약과학회 2003 한국농약과학회 학술발표대회 논문집 Vol.- No.-

Factors Affecting Sporulation, Germination, and Appressoria Formation of Epicoccosorus nematosporus as a Mycoherbicide Under Controlled Environments

Hong, Yeon-Kyu,Cho, Jae-Min,Lee, Bong-Choon,Uhm, Jae-Youl,Kim, Soon-Chul The Korean Society of Plant Pathology 2002 Plant Pathology Journal Vol.18 No.1

To develop Epicoccosorus nematosporus as a mycoherbicide of Eleocharis kuroguwai, the optimum temperature and humidity for sporulation of the pathogen were studied. Conidial production was most abundant at $28^{\circ}C$ with RH 60%, which yielded 661 mg in 9 cm Petri dish. Light intensity of 3,000 up to 7,500 lux was effective in stimulating conidial production of E. nematosporus on oatmeal agar, Light intensity affected sporulation more significantly than temperature. In the pot test, at least 12 h of dew period at $20^{\circ}C$ and $25^{\circ}C$ was required to achieve satisfactory conidial germination and appressorial formation. Few were killed at 8 h of dew period regardless of temperature. Sixteen hours of a single dew treatment immediately after inoculation killed more plants than did two or three repetitive dew treatments of 8-12 h.

Weeding Efficacy of Melanized Formula with Epicoccosorus nematosporus on Eleocharis kuroguwai in the Field

Hong, Yeon-Kyu,Cho, Jae-Min,Uhm, Jae-Youl,Hyun, Jong-Nae,Lee, Bong-Choon,Song, Seok-Bo,Lee, Dong-Chang The Korean Society of Plant Pathology 2003 Plant Pathology Journal Vol.19 No.2

The study was conducted to determine the cultural conditions and the effect of inert fillers for melanization and sporulation abilities of sodium alginate pellets, and the weeding efficacy of the formula in the field. Melanin production of E. nematosporus was affected by striking frequency. Percentage of melanized beads was increased to 80.6% at higher rpm up to 180. The melanized pellets produced more conidia with abundant mucilage than unmelanized pellets. Shaker culture of Epicoccosorus nematosporus with sodium alginate yielded a total of 55 mg per 100 pellets. Percentage of melanized pellets was highest with 81.0% and 83.3% of melanization, when wheat bran and rice polish were amended and produced the conidia with 65.4 and 68.4 mg per 100 pellets, respectively. When 1 L of conidial suspension of 6.0$\times$$10^5$ conidia per ml was applied on 30-day-old plants in a plot, 74.5% of the plants were killed within 20 days, whereas, its melanized sodium alginate pellets killed 57.8% of the plants in the same period. The number of tuber formation of Eleocharis kuroguwai in the untreated control plots was 128.5 per plot, but those of the plots treated with conidial suspension and melanized pellets were 22.1 and 39.7, respectively, at the end of the season. Results of this study showed that melanization of mycelia-mixed sodium alginate are an important sporulation factor in E. namatosporus as a mycoherbicide.

사과나무 腐爛病滴 Valsa ceratosperma에서의 Auxotrophic Mutants의 檢出

洪淵圭,嚴在烈 慶北大學校出版部 1987 慶北大農學誌 Vol.5 No.-

This study was conducted to elucidate the most appropriate method to obtain auxotrophic mutants from Valsa ceratosperma, the causal fungus of apple canker, which may be used as a gene marker in detecting the transfer of the factors of avirulent strains to virulent strains. Among the 3 kinds of synthetic media tested, each have two formula for minimal and complete, the medium which has been used in study if Endothia parasitica (E.P medium) was turned out to be most appropriate for the growth of V. ceratosperma. A medium for single colony formation from pycnidiospore of this fungus was developed by adding 0.5% L- sorbose to the E. P minimal medium. The period of incubation in dark for preventing the photoreactivation after U. V irradiation was estimated as about 60hrs at which most of the spores become binucleate. Largest number of putative auxotrophs were obtained at about 50second of irradiation to the spores smeared on the medium for single colony formation, at which the survival rate of spores was 5 to 6 percent. With these method developed in this experiment, 161 isolates of putative auxotrophs were detected among which the nutrient requirement for 10 isolates were determind. Five out of 10 mutants were still virulent to apple tree and all but one could not sporulate.

Evaluation of Control Efficacy of Biocontrol Agent, Epicoccosorus nematosporus on Eleocharis kuroguwai in the Field

Hong, Yeon-Kyu,Cho, Jae-Min,Uhm, Jae-Youl,Lee, Bong-Choon,Hyun, Jong-Nae,Hwang, Jae-Bok,Kim, Soon-Chul The Korean Society of Plant Pathology 2003 Plant Pathology Journal Vol.19 No.2

This study was conducted to determine the efficacy of Epicoccosorus nematosporus for the control of Eleocharis kuroguwai and to evaluate the meteorological factors which affect weeding efficacy in field conditions for three years (1996-1998). The best time to control E. kuroguwai with E. nematosporus as a biological control agent in the field was in July, when temperature ranged from 20.4 to $23.4^{\circ}C$; the surface wetness duration was 12.6-16.1 hours, and application time of 6:00 p.m. and 8:00 p.m.; and weeding efficacy was 81-90%. On 10 June 1996 in Milyang area, where the field experiments were performed, mean temperature was $16.5^{\circ}C$ with 11.3 hours of dew duration. Meanwhile, on 20 Aug. 1996 the temperature was $21.3^{\circ}C$ with 15.4 hours of dew duration. During these periods, the weeding efficacy was recorded at 61.8 and 60.8%, respectively. Time required for complete plant death was 25.8 and 25.6 days at application times 10 June and 20 Aug., respectively. At the time of application on 7,18, and 27 July 1996, mean temperature was 20.4-$23.4^{\circ}C$ with 12.6-16.5 hours of dew duration. The weeding efficacies of these periods were very hi일 with 81.4-90.8%. Three years of field observations from 1996 to 1998 showed that infection in the field can occur at any time through the summer season, although total infection rates vary between months and between years. In 1996, plant infection rapidly increased from 56% on 30 June, 82.4% on 15 July, 94.6% on 15 August, and 92.8% on 15 September under favorable meteorological conditions such as minimum temperature of $17.6^{\circ}C$ and maximum temperature of $27.1^{\circ}C$, with 86% relative humidity and 977.5 mm of rainfall during E. kuroguwai growing season. However, in 1997, the disease incidence was very low because of unfavorable weather conditions brought about by the hot temperature and the low amount of rainfall at 321.5 mm. Disease progress was slow from 24.4% on 30 June to 49.2% at the end of the growing season.