• Research in Plant Disease
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• v.30 no.1
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• pp.13-19
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• 2024

In July 2022 and 2023, black mold symptoms were observed sporadically on fruits of sweet pepper (Capsicum annuum) plants grown in a greenhouse located in Suwon, Korea. The incidence of black mold on the fruits was 5-24% (average 14.8%) in variety SP-504 (yellow and elongate type) and 1-8% (average 5%) in variety SP-505 (red and round type) investigated. Four single-conidium isolates of Alternaria sp. obtained from the diseased fruits were identified as Alternaria alternata based on the morphological characteristics and molecular phyogenetic analyses. The isolates were tested for pathogenicity to sweet pepper fruits of varieties SP-504 and SP-505 through artificial inoculation. The isolates mostly induced large lesions on fruits of the two varieties in the wound inoculation, but only two isolates small lesions on fruits of the variety SP-504 in the non-wound inoculation. No lesions formed on fruits of the variety SP-505 in the non-wound inoculation. The pathogenicity tests revealed that susceptibility of sweet pepper fruits to the disease differs between the varieties. The symptoms induced by pathogenicity tests with the isolates were similar to those observed on fruits from the greenhouse investigated. This is the first report of A. alternata causing black mold on sweet pepper fruits in Korea.

• Korean Journal Plant Pathology
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• v.2 no.3
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• pp.185-192
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• 1986

Upon germination, a conidium was septated in accordance with number of germ tubes. The percentages of ppressorial formation were not different between the resistant cultivars (Kumchang NO. 2 and Hongilpum) and the susceptible cultivars (Haneulcho and Saegochu). Appressorial form was various such as round, elliptic or star-shapped. The maximum number of appressoria was shown at 12 hours after inoculation. By 24 hours fter inoculation, hypersensitive tiny brown lesions were observed on the leaves and fruits of the resistant cultivars. Epidermal cells under cuticle layer of the resistant Kumchang NO. 2 fruit showed severe plasmolysis, while on the susceptible cultivars, the lession was largely extended to following incubation. Subcuticular infection hyphae were profusely colonized in the disintegrated tissues. Acervuli and setae on the stromatic structure ere formed at 96 hours. The infected seed coat was not only severely collapsed, but also infection hyphae were observed on the disintegrated seed coat, resulting severe plasmolysis of nucellus and embryo.

• 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.35 no.6
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• pp.564-574
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• 2019

Like many fungal pathogens, the conidium and appressorium play key roles during polycyclic dissemination and infection of Magnaporthe oryzae. Ran-binding protein microtubule-organizing center (RanBPM) is a highly conserved nucleocytoplasmic protein. In animalia, RanBPM has been implicated in apoptosis, cell morphology, and transcription. However, the functional roles of RanBPM, encoded by MGG_00753 (named MoRBP9) in M. oryzae, have not been elucidated. Here, the deletion mutant ΔMorbp9 for MoRBP9 was generated via homologous recombination to investigate the functions of this gene. The ΔMorbp9 exhibited normal conidial germination and vegetative growth but dramatically reduced conidiation compared with the wild type, suggesting that MoRBP9 is involved in conidial production. ΔMorbp9 conidia failed to produce appressoria on hydrophobic surfaces, whereas ΔMorbp9 still developed aberrantly shaped appressorium-like structures at hyphal tips on the same surface, suggesting that MoRBP9 is involved in the morphology of appressorium-like structures from hyphal tips and is critical for development of appressorium from germ tubes. Taken together, our results indicated that MoRBP9 played a pleiotropic role in polycyclic dissemination and infection-related morphogenesis of M. oryzae.

• Research in Plant Disease
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• v.10 no.2
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• pp.126-129
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• 2004

In July of 2002, leaf spot disease was found on kudzu (Pueraria lobata) leaves in Jeonbuk province. A small leaf spot was appeared on leaves as a typical symptom and the spot was then surrounded by chlorotic halo. The lesions were expended and coalesced and the infected leaves became yellow leaf and later fall out. A causal fungal pathogen was isolated and the colony of the pathogen was light gray green to dark green on PDA. The pathogen produced mostly the single conidium but rarely long chain of 3 to 8 conidia. The conidia were dark brown in color, long ellipsoid or oval and 20-60 ${\times}$ 10-25 ${\mu}{\textrm}{m}$ in size. Their septa were 4-8 transverse and 1-2 longitudinal or oblique. The pathogen was, therefore, identified as Alternaria tenuissima based on cultural and morphological characteristics. This is the first report on the leaf spot of kudzu caused by A. tenuissima in Korea.

• Korean Journal of Microbiology
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• v.44 no.1
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• pp.63-68
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• 2008

Strain Kan-23 was extracted from nematophagous fungi, which were isolated from the soil sample of oriental melon field. The strain exhibited the slow-growing characteristic forming conidia after prolonged incubation for 30 days. Morphological features of strain Kan-23 were observed under scanning electron microscope (SEM). It possesses erect conidiophores which contain $2{\sim}3$ side branches, with each branch producing $5{\sim}10$ conidia. The size of conidiophores were between $160{\sim}450\;{\mu}m$. Conidia were ellipsoidal with three septa[septum] in each conidium. Strain Kan-23 captured nematodes by means of giant constricting rings, which were observed in the glucose peptone agar medium. ITS region of rDNA sequence was analyzed. On the basis of the high sequence similarity of ITS region (99%), the Kan-23 strain was closely related to Drechslerella brochopaga (U51950). This is the first report on Drechslerella brochopaga as a nematophagous fungus in Korea.

• The Plant Pathology Journal
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• v.18 no.6
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• pp.328-332
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• 2002

Wheat samples showing typical spot blotch symptoms on stems and sheaths were collected from the field after physiological maturity, and were sealed in paper bags and stored in the laboratory at room temperature to study the survival of Bipolaris sorokiniana conidia on wheat straw. The materials were observed at monthly intervals to assess the conidia viability during storage. After 4 months, the frequency of individual conidia already present on wheat straw at the time of sampling was reduced and appeared to be progressively replaced by the formation of round structures consist-ing of conidia aggregates. After 5 months, distinct, individual conidia were no longer detected, and only 'clumps of conidia' were observed. These dark black aggregates or 'clumps of conidia’measured 157-170$\mu\textrm{m}$ in diameter and were grouped into boat-shaped olivacious conidia showing thick wall and measuring 50-82$\times$20-30$\mu\textrm{m}$. The germination was unipolar and below 0.5%, suggesting the occurrence of dormancy, In contrast, individual conidium produced on wheat during the growing season were 96-130$\times$16-20$\mu\textrm{m}$, slightly curved, hyaline to light pale, and euseptate with a bipolar germination reaching 98-100%. Bipolaris sorokiniana conidia produced on PDA were 55-82$\times$20-27$\mu\textrm{m}$, tapered at both ends, dark brown to olivacious, distoseptate, showed up to 1% germination, and were predominantly unipolar. Results of the present study suggest that B. sorokiniana conidia belonged to two different physiological categories corresponding to the pathogen's infection phase and its survival, respectively. The infection phase is characterized by a high germination percentage as opposed to the survival phase harboring apparent dormancy.

• Journal of Korean Society of Forest Science
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• v.96 no.1
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• pp.58-64
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• 2007

Overwintering adults of sycamore lace bug (Corythucha ciliata) infected by an unidentified pathogenic fungus were found on the stems of street trees of sycamore in Cheongju city. The objective of this study was to describe this entomopathogenic fungus infecting overwintering sycamore lace bug adults. This unidentified fungus colonized the insect adult body and formed white colony with subglobose clusters of conidiocarps. The size of conidiocarps was 300 to $400{\mu}m$ and each conidium was 15 to $20{\mu}m$. The conidiospore was globus and 2.5 to $3.0{\mu}m$ in diameter, and the hyphae were 1 to $5{\mu}m$ thick. This fungus was successfully isolated and cultivated on potato dextrose agar medium (PDA). The fungal colony was white and then became light yellow. When conidia from this pure culture were inoculated into the overwintering adults, the fungus formed conidiocarps with the same morphology on the insect body and the lethal rate by the fungus was $88{\pm}16%$. This fungus has over 99% homology with Cordyceps bassiana (imperfect fungal name is Beauveria bassiana) in ITS-5.8s rDNA base sequence. The fungal ecology and the infection process of the fungus into its host need to be clarified before using this fungus as a biological control agent.

• Korean Journal of Environmental Agriculture
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• v.35 no.1
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• pp.72-78
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• 2016

BACKGROUND: Entomopathogenic fungi have been studied to develop for biological control agents as an alternative to chemical control agents in insect pest management. This investigated to determine the optimal culture conditions in ceramic balls for maximal sporulation of entomopathogenic fungi Beauveria bassiana M130 by use rice bran extract.METHODS AND RESULTS: METHODS AND RESULTS: A culture of entomopathogenic fungi for 12day on rice bran extract(1:8, w/v) incubated in ceramic matrix at 28℃. Natural zeolite ceramic ball was high production of 4.2×108 conidial/mL. The culture condition optimized initial pH, temperature, rice bran extract concentration, adhesives substance and concentration of NaCl, respectively. The high production of spore optimal conditions were temperature 28℃, initial pH 3, rice bran extract 3 mL, starch 33 g, 5 % NaCl and sopre suspension 7 mL, respectively.CONCLUSION: This study was carried out for the mass production of entomopathogenic fungi conidia recover rate 65% in matrix of natural zeolite ceramic ball, and to develop ingredient-used formulation of Beauveria bassiana M130 conidia for biological control agents.

• Korean Journal of Environmental Agriculture
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• v.36 no.4
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• pp.299-305
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• 2017

BACKGROUND: Although the filamentous fungal pathogen Colletotrichum species causing anthracnose disease on various fruits including peach, apple, persimmon and grape, there is no report on Japanese plum in Korea. METHODS AND RESULTS: In 2016, diseased fruits showing typical anthracnose symptoms of Japanese plum were collected in market and ochards. Diseased tissue was cut off and disinfected subsequently with 70% ethanol for 1 min, and in 1% sodium hypochloride solution for 1 min, followed by three washes with sterile distilled water. The disinfected tissues were placed onto potato dextrose agar (PDA), and incubated at $25^{\circ}C$ in the dark for 5 to 7 days. For single-spore isolation, conidia were scraped off the plate using a loop, and suspended with 10 mL sterile distilled water. One hundred microliter of the conidial suspension was spread on PDA plates and incubated at $25^{\circ}C$. Finally, one germinated conidium was transferred onto PDA plates. Morphological and cultural characteries of colonies and spores of isolated Colletotrichum were observed after 7 to 10 days incubation on PDA. Molecular identification of isolates were analyzed by comparing rDNA-ITS gene sequences with NCBI GeneBank. CONCLUSION: Of eleven isolates of Colletotrichum isolated from anthracnose diseased Japanese plum fruits, six were identified as C. acutatum, and five as C. gloeosporioides based on diagnostic characteristics such as colony growth rate, shape and size of conidia, and rDNA-ITS sequences. This is the first report of Colletotrichum causing the anthracnose on Japanese plum in Korea.