• 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.

• 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.

• 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.

• Microbiology and Biotechnology Letters
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• v.32 no.3
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• pp.238-242
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• 2004

Antifungal agents, flavofungin and fungichromin were isolated from the fermentation culture broth of a Streptomyces sp. SKM338. Biological evaluation of these antibiotics indicated that the compounds possesses broad spectrum antifungal activity against various pathogens. Especially, these compounds inhibited throughly growth of Didymella bryoniae, caused Gummy stem blight of melons, occurs in the southeastern Korea. Inhibition of this pathogen may be prevented from directly reducing both pre- and post-harvest yields.

• 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.

• Mycobiology
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• v.48 no.1
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• pp.9-19
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• 2020

Two fungal species of ascomycetes were discovered during the screening of soil microflora from the Gangwon Province in Korea: Didymella chlamydospora sp. nov. (YW23-14) and Microdochium salmonicolor sp. nov. (NC14-294). Morphologically, YW23-14 produces smaller chlamydospores (8.0-17.0 × 7.0-15.0 ㎛) than D. glomerata and D. musae. The strain NC14-294 was characterized by smaller conidiogenous cells (4.9-8.8 × 2.0-3.2 ㎛) compared with the closest strains M. fisheri and M. phragmitis. The detailed descriptions, illustrations, and discussions regarding the morphological and phylogenetical analyses of the closely related species are provided to support the novelty of each species. Thus, YW23-14 and NC14-294 are described here as newly discovered species.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.57-62
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• 2001

Twelve antagonistic strains against Fusarium wilt of watermelon-rootstock gourd were selected from 54 bacterial isolates which were isolated from the rhizosphere of crop plants growing in various locations. They showed strong inhibitory effects on growth of Fusarium osysporum f. sp. niveum, the causal agent of watermelon-rootstock gourd Fusarium wilt. Among these antagonists, the isolate YJ-3 was the most pronounced in growth-promoting ability for watermelon-rootstock gourd. The growth of watermelon-rootstock gourd in bed soil inoculated with YJ-3 was better by 46 and 13% than those in commercial bed soil alone and in bed soil inoculated with commercial microbial inoculant, respectively. The antagonistic plant growth-promoting rhizobacterium, strain No. YJ-3, was identified as Bacillus sp. on MIDI system. Furthermore, Bacillus sp. YJ-3 showed antifungal activity on growth against Alternaria cucumerina, Botrytis cinerea, Colletotrichum orbiculare, Didymella bryoniae, Rhizoctonia solani and Fusarium oxysporum.

• Research in Plant Disease
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• v.15 no.1
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• pp.30-35
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• 2009

This study was carried out to determine the causal agents of soil-borne fungal diseases that pose a threat to the muskmelon production in Cheong Yang, Korea and to investigate the potential effects of hot water drenching and three fumigant (metam sodium, dazomet and methyl bromide) on these diseases. As the agents of the diseases, Monosporascus cannonballus, Didymella sp., Fusarium sp., Phytophthora sp., were detected. Hot water and the fumigants were treated on two successive cropping seasons of melon. Soil temperature was measured at 0, 10, 20 and 30 cm soil depth. In 2005, soil sterilization by hot-water was more effective significantly to control of the diseases than by fumigant. yield was the highest in hot-water sterilized plot as $39\;ton{\cdot}ha^{-1}$. Dazomet ($50\;g/m^2$) treated plot was followed as $23\;ton{\cdot}ha^{-1}$. In 2006, hot water sterilized plot showed higher yields than non-treated plots ($14.8\;ton{\cdot}ha^{-1}$). But the other three fumigant contained Dazomet ($50\;g/m^2$) were no difference (P<0.05) in yield.