• Mycobiology
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• v.51 no.6
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• pp.393-400
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• 2023

During a disease survey in October 2019, leaf spot symptoms with a yellow halo were observed on Korean angelica (Anglica gigas) plants grown in fields in Pyeongchang, Gangwon Province, Korea. Incidence of diseased leaves of the plants in the investigated fields ranged from 10% to 60%. Morphological and cultural characteristics of two single-spore isolates from the leaf lesions indicated that they belonged to the genus Didymella. Molecular phylogenetic analyses using combined sequences of LSU, ITS, TUB2, and RPB2 regions showed distinct clustering of the isolates from other Didymella species. In addition, the morphological and cultural characteristics of the isolates were somewhat different from those of closely related Didymella spp. Therefore, the novelty of the isolates was proved based on the investigations. Pathogenicity of the novel Didymella species isolates was confirmed on leaves of Korean angelica plants via artificial inoculation. This study reveals that Didymella gigantis sp. nov. causes leaf spot in Korean angelica.

• Mycobiology
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• v.51 no.5
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• pp.313-319
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• 2023

During disease surveys of Angelica acutiloba plants in Korea, leaf spot symptoms were observed in a field in Andong in July 2019, and stem rot symptoms in vinyl greenhouses in Yangpyeong in April 2020. Incidence of leaf spot and stem rot of the plants ranged from 10 to 20% and 5 to 30%, respectively. Morphological and cultural characteristics of fungal isolates from the leaf spot and stem rot symptoms fitted into those of the genus Phoma. Molecular phylogenetic analyses of two single-spore isolates from the symptoms using concatenated sequences of LSU, ITS, TUB2, and RPB2 genes authenticated an independent cluster from other Didymella (anamorph: Phoma) species. Moreover, the isolates showed different morphological and cultural characteristics in comparison to closely related Didymella species. These discoveries confirmed the novelty of the isolates. Pathogenicity of the novel Didymella species isolates was substantiated on leaves and stems of A. acutiloba through artificial inoculation. Thus, this study reveals that Didymella acutilobae sp. nov. causes leaf spot and stem rot in Angelica acutiloba.

• Research in Plant Disease
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• v.25 no.3
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• pp.143-148
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• 2019

An outbreak of new disease with leaf and stem blight symptom occurred at bracken-growing fields in Namhae-gun, Gyeongsangnam-do, Korea during the last 4 years. This new disease caused significant yield losses on bracken production in this area. We have collected diseased leaves and stems showing the blight symptom in May, July, and October 2018 to investigate causal pathogens. A total of 92 fungal isolates were obtained from the diseased samples and their pathogenicity was tested on healthy bracken leaves. From the total isolates, 22 isolates were able to produce the leaf blight symptom similar to the original one found in the fields. To identify two fungal pathogens which showed higher virulence levels compared to other pathogenic isolates, we constructed phylogenetic trees using the nucleotide sequences of genes for ribosomal RNA, RNA polymerase beta subunit, beta tubulin, and internal transcribed region. Most phylogenetic trees constructed indicate that both isolates, which are identical to each other, reside in a clade of the genus Didymella and possibly similar to D. rumicicola or D. acetosellae. Nevertheless, the exact identification of these pathogens at the species level needs further investigations. This is the first report of a blight disease on bracken by Didymella sp.

• The Korean Journal of Mycology
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• v.49 no.4
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• pp.555-560
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• 2021

During disease surveys conducted from 2019 to 2021 in Korea, leaf spot symptoms in rhubarb (Rheum rhabarbarum) plants were frequently observed in plants growing in fields located in Cheolwon, Taebaek, and Inje in Gangwon Province. The incidence of diseased leaves of the plants in the fields ranged from 2% to 80%. Nine single-spore isolates of Phoma sp. were obtained from lesions of the diseased leaves; all of them were identified as Didymella rhei based on their cultural, morphological, and molecular characteristics. Three isolates of D. rhei were tested for pathogenicity on rhubarb leaves using artificial inoculation. All the tested isolates caused leaf spot symptoms in the inoculated plants; the symptoms were similar to those observed in plants from the fields investigated. This is the first report of D. rhei causing leaf spot in rhubarb in Korea.

• Research in Plant Disease
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• v.29 no.1
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• pp.60-63
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• 2023

During disease surveys from 2019 to 2021, the authors frequently encountered leaf spot symptoms on Fischer's ragwort plants growing at fields at six locations of Gangwon Province, Korea. The symptoms displayed brown to dark brown, circular or irregular spots on the plant leaves. The disease surveys at the six locations revealed 1-90% of diseased leaves of the plants. Phoma sp. was dominantly isolated from the diseased leaf lesions. Seven single-spore isolates of the fungus were selected and identified as Didymella ligulariae by investigation of their cultural, morphological, and molecular characteristics. Artificial inoculation test to Fischer's ragwort leaves was conducted with three isolates of D. ligulariae. The inoculation test revealed that the tested isolates cause leaf spot symptoms in the plants similar to the natural ones. The fungal pathogen has never been reported to cause leaf spot in Fischer's ragwort. Leaf spot of Fischer's ragwort caused by D. ligulariae is first reported in this study.

• Research in Plant Disease
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• v.10 no.4
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• pp.313-318
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• 2004

Internal fruit rot of cucumber was observed in several locations in Korea. Incidence of the disease reached up to 21.5% and averaged 4.2% in the fields surveyed. The disease started at blossom ends of cucumber fruits. Internal tissues of infected fruit tips showed brown discoloration over 2 cm in length and 2 mm in diameter. Subsequently, the brown discoloration was extended into the carpels, and the surface of the infected fruit tips was rugged. Fungal isolates from the internal tissues of diseased fruits were identified as Didymella bryoniae based on mycological characteristics. Temperature for mycelial growth of isolates ranged $5{\sim}32^{\circ}C$ with optimal temperature between $26{\sim}28^{\circ}C$. Similar symptoms were developed in the internal part of the cucumber fruit when conidial suspensions of the isolates were inoculated to the flower of cucumber. Furthermore, Didymella bryoniae isolates from other plant parts of cucumber, watermelon, oriental melon, melon and pumpkin also showed the similar symptoms in the internal part of cucumber fruits by inoculation tests. Temperature range for occurrence of internal fruit rot of cucumber was $10{\sim}32^{\circ}C$ with optimal temperature of $25{\sim}28^{\circ}C$.

• Korean Journal of Microbiology
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• v.42 no.2
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• pp.135-141
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• 2006

We isolated a bacterium which produces antifungal substances from the Sanktpeterburg soils at Russia. The iso-lated strain was identified as Brevibacillus sp. and shown a strong antifungal activity on plant pathogenic fungi. Brevibacillus sp. KMU-391 produced maximum level of antifungal substances under incubation aerobically at $30^{\circ}C$ for 48 hours in trypticase soybean broth containing 1.0% sucrose and 1.0% polypeptone at 180 rpm and initiated pH adjusted to 7.0. Precipitate of culture broth by $30{\sim}60%$ ammonium sulfate precipitation exhibited strong antifungal activity against Didymella bryoniae by dry cell weight. Butanol extract of cultured broth also shown fungal growth inhibitory activity against Botrytis cinerea KACC 40573, Botrytis fabae KACC 40962, Colletotrichum gloeosporioides KACC 40804, Colletotrichum orbiculare KACC 40808, Didymella bryoniae KACC 40669, Fusarium graminearum KACC 41040, Fusarium oxysporum KACC 40037, Fusarium oxysporum KACC 40052, Fusarium oxysporum f, sp. radicis-Iycopersici KACC 40537, Fusarium oxysporum KACC 40902, Monosporascus cannonballus KACC 40940, Phytophthora camvibora KACC 40160, Rhizoctonia solani AG-1(IA) KACC 40101, Rhizoctonia solani AG-4 KACC 40142, and Scleotinia scleotiorum KACC 41065 by agar diffusion method.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.133.1-133
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• 2003

Gummy stem blight, caused by Didymella bryoniae occurs exclusively on cucurbits. This fungus has been known not to produce its pycnidium in vitro unless irradiated. Through this study, we optimized cultural conditions for mass-production of pycnidiospore by Metal Halide Lamp irradiation. In brief, the mycelial was cultured at $26^{\circ}C$ on PDA, for 2 days under the darkness, and then the plate was illuminated with MH lamp continuously for 3-4 days at $26^{\circ}C$, a great number of pycnidia was simultaneously formed. Thus produced pycnidiospores were used as immunogen. From fusions of myeloma cell (v-653) with splenocytes from immunifed mice were car ried out. And, two hybridoma cell lines that recognized the immunogen Didymella bryoniae were obtained. One Monoclonal Antibody, Db1, recognized the supernatant and the other monoclonal antibody, Db15, recognized the spore. Two clones were selected which were used to produce ascite fluid two MAb Db1 and Db15, were immunotyped and identified as IgG1 and IgG2b, respectively. Titer of MAb Db1 and MAb Db15 was measured absorbance exceeded 0.5 even at a $10^{-5}$ dilution. The MAbs reacted positively with Didymella bryoniae but none reacted with other of fungi and CMV, CGMMV Sensitivity of MAb was precise enough to detect spore concentration as low as $10^{3}$ well by indirect ELISA characterization of the MAb Db1, Db15 antigen by heat and protease treatments show that the epitope recognized by the MAb Bb1, Db15 were a glycoprotein.

• Korean journal of applied entomology
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• v.16 no.4 s.33
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• pp.211-215
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• 1977

The Sporulation of Didymella bryomiae were observed under diurnal cycles of light/darkness of near ultraviolet light (NUV) and artificial daylight (ADL) and continous darkness in eight isolates growing on PDA and V-8 juice agar. Light stimulated pycindial and perithecial formation of this fungus on potato dextrose agar and V-8 juice agar. Sprulation was poor in darkness, but some isolates were able to produce pycnidia and perithecia in the absence of light. Perithecial formation was much better under artificial daylight (ADL) on V-8 juice agar than those grown under near ultraviolet light (NUV). In general, cultures grown on V-8 juice agar sporulated better than cultures grown on PDA under three setsof light condition. Most of the pycnidiospores obtained from each isolates of this fungus grown on PDA were non-septate and microtype, but macrotype of non-septate and uniseptate pycnidiospores were produced on V-8 juice agar. Pycnidiospore produced on V-8 juice agar were similar to those produced on the radicle of naturally infected seeds. The appearance of perithecia were quite distinctive from pycnidia. The mature perithecia were darker than pycnidia and whitish spore masses formed on the ostiole of perithecia.

• Mycobiology
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• v.38 no.3
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• pp.166-170
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• 2010

Gummy stem blight is a major foliar disease of muskmelon (Cucumis melo L.). In this study, morphological characteristics and rDNA internal transcribed spacer (ITS) sequences were analyzed to identify the causal organism of this disease. Morphological examination of the Jeonbuk isolate revealed that the percentage of monoseptal conidia ranged from 0% to 10%, and the average length $\times$ width of the conidia was 70 ($\pm$ 0.96) $\times$ 32.0 ($\pm$ 0.15) ${\mu}m$ on potato dextrose agar. The BLAST analysis showed nucleotide gaps of 1/494, 2/492, and 1/478 with identities of 485/492 (98%), 492/494 (99%), 491/494 (99%), and 476/478 (99%). The similarity in sequence identity between the rDNA ITS region of the Jeonbuk isolate and other Didymella bryoniae from BLAST searches of GenBank was 100% and was 95.0% within the group. Nucleotide sequences of the rDNA ITS region from pure culture ranged from 98.2% to 99.8%. Phylogenetic analysis with related species of D. bryoniae revealed that D. bryoniae is a monophyletic group distinguishable from other Didymella spp., including Ascochyta pinodes, Mycosphaerella pinodes, M. zeae-maydis, D. pinodes, D. applanata, D. exigua, D. rabiei, D. lentis, D. fabae, and D. vitalbina. Phylogenetic analysis, based on rDNA ITS sequence, clearly distinguished D. bryoniae and Didymella spp. from the 10 other species studied. This study identified the Jeonbuk isolate to be D. bryoniae.