• The Plant Pathology Journal
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• v.18 no.1
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• pp.43-49
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• 2002

Direct effects of atmospheric ozone on conidia of the rice blast pathogen, Magnaporthe grisea, were investigated to evaluate ozone-induced effects on infection potential of the rice blast fungus. Acute ozone exposure (200 nl $1^{-1}$, 8 h $day^{-1}$3 days) during sporulation significantly affected conidial morphology, appressorium formation, and disease development on rice loaves. Ozone caused reduction in conidial size and change in conidial shape. Relative cytoplasmic volume of lipids and vacuoles were increased in ozone-exposed conidia. Inhibition of appressorium formation and simultaneous increase in endogenous levee of polyamines were found in ozone-exposed conidia. The inverse relationship between appressorium formation and level of polyamines implies that ozone-mediated increase in intracellular level of polyamines may inhibit appressorium formation in rice blast fungus. Furthermore, rice plants inoculated with ozone-fumigated conidia exhibited less severe disease development than those with unfumigated conidia. This result suggests that the anti-conidial consequence of acute ozone will eventually weaken the rice blasts potential for multiple infection cycle. This further suggests that consequently, rice blast can be transformed from an explosive disease to one that has limited epidemiological potential in the field.

• The Korean Journal of Mycology
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• v.19 no.1
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• pp.27-31
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• 1991

Formation of conidium, an asexual organ on the hyphae, was examined from ten species of Pleurotus. Conidiospores of them were distinguished into two types of spores; an elliptical and a globose spores. Dikaryotic hyphae of ten species and monokaryotic hyphae of three species were observed to produce conidiospore. Conidia were observed on the hyphae grown on mushroom complete agar medium but were not on mushroom minimal agar medium. Two aconidial mutants were obtained by the ultraviolet irradiation.

• The Korean Journal of Mycology
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• v.21 no.3
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• pp.224-229
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• 1993

The optimum temperature for germination of conidia and germ tube elongation were between $20\;and\;30^{\circ}C$ in C. dematium and C. gloeosporioides. Appressoria were fairly formed well at $20^{\circ}C$ despite the delay of conidial germination. At $30^{\circ}C$, both the germination and germ tube elongation are favored, but appressoria were poorly detected to be formed. In C. acutatum, the optimum temperature for germination of conidia was from $20\;to\;30^{\circ}C$, but at $25^{\circ}C$, germ tube elongation are accelerated. The conidia become septate and one or both doughter cells become conidiogenous instead of producing germ tubes and a secondary conidia produced, resulting in an arborescent type of connected conidia. Appressoria are infrequently formed by germinating conida. At $20\;to\;25^{\circ}C$ was the optimum for appressorium formation. But conidia that germinated at $30^{\circ}C$ seemed to lose the ability to form appressoria. The relation of temperature to germination of conidia and appressorium formation in Colletotrichum acutatum, C. dematium and C. gloeosporioides are discussed.

• The Plant Pathology Journal
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• v.15 no.4
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• pp.223-227
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• 1999

Pre-penetration behavior of Boytryosphaeria dothidea on apple fruits was investigated with scanning electron microscopy. Once conidia were deposited on the fruit surface, they germainted and produced germ tubes from one or both ends of the conidia. Germ tubes grew over the fruit surface and entered the fruits through lenticels or surface cracks formed naturally. Germ tubes of the fungus also appeared to penetrated the fruits directly with or without forming appressoria. Globose appressoria were frequently formed at the tip of germ tubes on the fruit surface, where no lenticels or surface cracks were found. The conidia collapsed and became flattened to the fruit surface after appressorial formation. Cuticles of fruit surface underneath appressoria and tips of some germ tubes were evidently altered, indicating possibility of direct penetration of the fungus by enzymatic degradation of the cuticle layers. This the first report on the formation of appressoria by B. dothidea.

• The Plant Pathology Journal
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• v.16 no.1
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• pp.19-24
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• 2000

The direct effects of acute $\textrm{O}_3$ on the growth, sporulation and infection of Pyricularia grisea, rece blast pathogen, were investigated to understand the interactions between ozone and the pathogen. Acute exposure of 200 nl $\textrm{l}^{-1}$ ozone for 8 h significantly reduced conidia germination on water atar. Ozone exposure of 200 nl $\textrm{l}^{-1}$ for 8h per day for 5 days had no effect on increase in colony diameter, but severely damaged actively growing aerial mycelia. However, the damage to mycalia was recovered during the following 16 h exposure of unpolluted air. Conidial production was also stimulated by the acute ozone exposure for 5 days. The conidia exposed to the acute ozone for 5 days normally germinates but slightly reduce appressoria formation on rice leaf. However, the conidia produced by artificial stimulation under the same ozone concentration for 10 days showed significant reduction in appressorea for mation on a hydrophobic film. This study suggests that the acute ozone could ingibit appressoria formation as well as vegetative growth of the pathogen, resulting in decrease in rece blast development in the field during summer when high ozone episodes could occur occasionally.

• Journal of Ginseng Research
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• v.20 no.1
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• pp.88-95
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• 1996

The effects of media, incubation time, temperature and pH on production of conidia and chlamydospore of Cylindrocarpon destructans (Zinssm.) Scholen causing root rot of Panax ginseng were studied. Microconidia of the pathogen were abundantly produced on V-8 juice agar as a solid substrate with 5.73(log conidia/mm2) and in V-8 broth as a liquid substrate with 6.65 (log conidia/ml) among media tested. No difference was observed on the length of microconidia produced from the media with a range of 9.50∼11.38 $\mu\textrm{m}$. However, tryptic soy agar produced the broadest microconidia (average 5.00 $\mu\textrm{m}$) among the media tested. All the media produced chlamydospores In a range of 1.06∼4.37 (log chlamydospores/mm2) without a significant difference in number, while V-8 juice agar produced the bigger one (18.39 $\mu\textrm{m}$ in diameter) as compared to the tested media. The fungus began to sporulate conidia after three days of incubation and reached maximum at the 8th day. It seemed to be in a stationary phase until 30 days of incubation but was decreased thereafter. Chlamydospore was produced at 4th day after incubation. Maximum production was observed at 8th day and the number seemed to be maintained during the observation period. Both conidia and chlamydospore of the pathogen were able to be spoluated at 10∼25$^{\circ}C$. However, optimum temperatures of conidia and chlamydospore formation were 15∼25$^{\circ}C$ and 10∼20$^{\circ}C$, respectively. C. destrmtans produced conida with an wide range of pH from 3.3 to 8.0 and chlamydospore from 2.8 to 8.0. Number of conidia was increased with an increase of pH up to 4.0. There was no significant difference in the number between 4.0 to 8.0. It seemed to have two optimum pH ranges, 3.3∼4.0 and 7.1∼8.0 for the chlamydospore formation.

• Korean journal of applied entomology
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• v.47 no.2
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• pp.169-174
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• 2008

The growth characteristics of Paecilomyces tenuipes according to the passage in the two kind of liquid media were investigated by comparing the mycelium and conidium formation degrees. The potato dextrose broth medium and the silkworm larvae medium containing the silkworm powder were used as the liquid media, and the potato dextrose agar medium and the brown rice medium containing the powder of silkworm pupa were used as the solid media. The conidium formation degree in liquid media differed by the passages but that in solid media was not. This suggested that the passage in liquid media did not affect significantly the conidium formation in solid media. When the brown rice media were inoculated with the concentration of $1{\times}10^{10}$ conidia/ml, $1{\times}10^8$ conidia/ml and $1{\times}10^6$ conidia/ml, respectively, the conidium formation degrees were similar. This indicated that the optimal inoculation concentration of conidium to the brown rice media is $1{\times}10^6$ conidia/ml.

• Korean Journal Plant Pathology
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• v.13 no.1
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• pp.30-36
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• 1997

The effects of carbon and nitrogen sources on the mycelial growth and sporulation of microconidia and chlamydospores of five isolates of Cylindrocarpon destructans (Zinssm.) Scholten causing root rot of Panax ginseng were studied. For the carbon sources, fructose, glucose, maltose, and sucrose in Czapek-Dox broth showed good mycelial growth of 178∼201 mg in dry weight compared with 64 mg of the control. The best carbon sources tested for conidial formation were sucrose and maltose with 2.75 and 3.03 log conidia/ml, respectively. For the nitrogen sources, aspartic acid, NaNO3, KNO3, arginine, threonine, and leucine increased mycelial growth of the fungi to 208∼231 mg in dry weight without significant difference (p=0.05) among them. Meanwhile the growth with cystine was poor (26.3 mg dry weight), and no conidium and chlamydospore were formed. Maximum microconidial formation was observed in the media with NaNO3 and KNO3 as 3.37 and 3.35 log conidia/ml, and for the chlamydospore formation the (NH4)2SO4-containing medium and the nitrogen-absent medium were the best as 3.40 and 3.57 log chlamydospores/ml, respectively. No conidium was found in the medium without nitrogen sources, in which chlamydospore formation increased 6 times more than in the nitrogen-amended medium. However, deletion of carbon source in the medium did not affect on the formation of conidia and chlamydospores of C. destructans.

• Mycobiology
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• v.33 no.2
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• pp.118-120
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• 2005

Most commonly occurring predacious fungus Arthrobotrys oligospora showed great variation in size and shape of conidia on some media. The formation of larger conidia was recorded on beef extract and nutrient agar media. The length of conidia in Richard's YPSS, Sabouraud's, PDA and com meal agar media was of medium size while smaller conidia were produced on Czapek's, Jensen's, Martin's medium. Maximum width of conidia was recorded on YPSS medium followed by Sabouraud's medium. The average size of spores on nematode infested com meal agar medium was slightly increased than those on com meal agar medium.

• The Plant Pathology Journal
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• v.18 no.2
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• pp.81-84
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• 2002

Effects of temperature and dew period on sporulation of a mycoherbicide, Epicoccosorus nematosporus, on the lesion of its host, Eleocharis kuroguwai were determined. Conidia formation was first observed after 10 days on plants incubated for either 12 or 16 h in a dew chamber at 28$^{\circ}C$; 16 h dew period resulted in more conidia formation. As the dew period was decreased to less than 8 h, fewer conidia formed. Conidial production was most abundant at 28$^{\circ}C$ and produced as much as 3.3$\times$10$^4$conidia per lesion, while 0.1$\times$10$^3$and 2.3$\times$10$^3$conidia per lesion were produced at 16$^{\circ}C$ and 36$^{\circ}C$, respectively. Alternating temperature regimes, i.e., 30/15, 30/20, 28/20, and 28/15$^{\circ}C$ (day/night) were much better than constant temperature, i.e., 30/30, 28/28/, and 20/2$0^{\circ}C$ for sporulation. In the second sporulation, there were as much as 3.1$\times$10$^4$conidia per lesion (ca. <50% of the first sporulation). Then, sporulation dropped sharply to 6.2$\times$10$^2$conidia per lesion in the third sporulation. Results of this study suggest that temperature combined with dew period is the primary limiting factor in the use of E. nematosporus as a mycoherbicide off, kuroguwai.