• Research in Plant Disease
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• v.26 no.2
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• pp.79-87
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• 2020

Fusarium wilt caused by Fusarium oxysporum f. sp. fragariae (Fof) is the most important diseases of a strawberry field in Korea. We surveyed phylogenetic analysis, pathogenicity test, and fungicide response about Fof isolates isolated from Korea. Twenty-seven isolates of F. oxysporum isolated from strawberry plants were conducted in this study. Specific amplification by Fof specific primer was confirmed in all 26 isolates except Fo080701 isolate. The nuclear ribosomal intergenic spacer region and the translation elongation factor EF-lα gene sequences of isolates revealed three main lineages. Most of all isolates were contained DNA lineage group 1, but 2 and 3 group was shown only one and three isolates, respectively. All isolates were shown in pathogenicity with cv. Seolhyang. The EC₅₀ mean values of prochloraz ranged 0.02-0.1 ㎍/ml except for Fo080701 and effectively inhibited mycelial growth at low concentrations. The EC₅₀ value of metconazole was also 0.04-0.22 ㎍/ml, showing a similar inhibitory effect to that of prochloraz. The EC₅₀ value of pyraclostrobin was 0.23-168.01 ㎍/ml, which was different according to the strain. In the field trial, boscalid+fludioxonil, fluxapyroxad+pyraclostrobin, and prochloraz manganese were selected as the effective fungicides for controlling Fusarium wilt.

• The Korean Journal of Mycology
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• v.24 no.4 s.79
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• pp.246-254
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• 1996

Since the mid of 1980's, cultivation area and production of Ganoderma lucidum have been increased annually in Korea. However, the presence of a fungal disease has become a major limiting factor in the cultivation of Ganoderma lucidum, causing a serious economic loss. The present study was carried out to isolate and identify the pathogenic fungus to Ganoderma lucidum. Several fungi isolated from the wood logs showing typical symptoms were tested whether they are pathogenic to Ganoderma lucidum or not by cross-pairing culture method, flask inoculation method, and wood log inoculation method. The pathogenic fungus produced ascomata. Mature ascomata was spherical, dark, thick-walled, $45{\sim}95\;{\mu}m$ diameter. Asci were thin-walled, evanescent when mature, disintegrate early. Ascospores were spherical, hyaline, glaborous, thick-walled, refractive, $3.6{\sim}4.3\;{\mu}m$ in size. Conidiophores soon became abundantly septate and broke up into arthrospores, which are cylindrical, $3{\sim}6\;{\mu}m$ long and $3{\sim}4\;{\mu}m$ wide. Based on the observations under dissecting microscope, light microscope and scanning electron microscope, teleomorph and anamorph of the pathogenic fungus were identified as Xylogone sphaerospora Von Arx & Nilsson and Sporendonema purpurascens (Bonordon) Mason & Hughes, respectively. X. sphaerospora is first reported as a pathogenic fungus of Ganoderma lucidum.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.325-334
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• 1996

Pepper plants were flooded at 0, 5, 10 and 15cm at seedling stage under the condition of greenhouse. Treatment of flooding times are 6, 12, 24, 48 and 120 hours. The results obtained are summarized as follows. Plant height, number of leaves, shoot and root fresh weight were not recovered the flooding damages regardless of flooding time and depth. Pepper plant died in flooding depth of 5cm or more for over 48 hours. Plants in fallen leaves were found at more than 5cm depth and 6 hours of floodings. Photosynthesis and respiration rate decreased in the 5cm flooding depth or more for 24 hours. Chlorophyll content and root activity decreased for 12 hours or more at all the flooding depth. Also, diffusion resistance of stomata cell increased as increased flooding time and depth. Diseases occurred remarkably in proportion to the depth and hours of flooding treatment. It was not possible to control the desease by fungicide, also then was no effects of foliar spray of urea. Weight of fruit per plant not decrease by the 12 hours of 0cm and the 6 hours of 5cm flooding but decreased at deeper and longer flooding. Average weight of a fruit increased. The yield could not expected in the depth of 5cm or more for over 48 hours, There was significant positive correlation between all the investigated characteristics of growth and yield. There was, however, negative correlation between number of leaf and diffusion resistance of stomata.

• The Korean Journal of Mycology
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• v.40 no.4
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• pp.288-291
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• 2012

Korean oak wilt disease caused by Raffaelea quercus-mongolicae is vectored by the ambrosia beetle Platypus koryoensis. To prevent the spread of the disease, the beetle infested oak tree had been cut into logs, covered with plastic vinyl, fumigated with a pesticide, and stored for three years on the site where the tree was cut. This study was carried out to get information on the fungi colonizing the fumigated oak wood. Wood disk samples collected from the fumigated oak logs at two locations in the Taejo Mountain, Cheonan city, were used for fungal isolation. A total of 99 filamentous fungal isolates were obtained from the wood disk samples. Hypocrea spp., Trichoderma spp. and Penicillium spp. were identified based on morphological characteristics and nucleotide sequence analysis of translation elongation factor 1-alpha gene and ITS rDNA region. Trichoderma was the major fungal group. R. quercus-mongolicae, and P. koryoensis were not detected from the fumigated oak wood. Our work provided evidence that after three years of storage, the fumigated oak wilt-diseased logs should be no longer harmful source of oak wilt disease transmission.

• Research in Plant Disease
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• v.15 no.2
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• pp.130-133
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• 2009

We have conducted in vitro experiments with nano-silver liquid for their effect against various plant pathogenic bacteria. Different types of nano-silver liquid WA-CV-WA13B, WA-AT-WB13R and WA-PR-WB13R were used. These are classified based on different manufacturing processes. The tested bacteria were provided by KACC. We experimented ten bacterial isolates in Clavibacter, Erwinia, Pseudomonas, Ralstonia, and Xanthomonas genera. In order to determine the level of concentrations of control effects, different concentrations (10, 25, 50, and 100 ppm) of each different nano-silver liquid were added in the culture media. As a result, WA-CV-WA13B showed high inhibition effect against C-1 at 10 ppm, and showed minor inhibition effects against P-6, X-1, and X-2. WA-AT-WB13R showed bactericidal effect against P-6 at 10 ppm. At 10 ppm, WA-AT-WB13R showed relatively high inhibition effects against C-1, X-1, and X-2. WA-PR-WB13R showed bactericidal effects against P-5, P-6 and X-2 at 10 ppm or higher concentrations. All the tested three nano-silver liquid showed bactericidal effects against all the tested plant pathogenic bacteria at concentrations of 25 ppm or higher. These results indicated the possible use of nano-silver liquid for the control of plant pathogenic bacteria.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.50-56
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• 2001

Thirty-three bacterial and fungal strains were isolated from the rotten soybeans and soybean sprouts to isolate pathogenic microorganisms which cause soybean sprouts rot during soybean sprouts cultivation. In pathogenicity tests of the isolates on soybean sprouts, two isolates(K-17 and K-28) caused soybean sprouts rot and were identified as Erwinia carotovora and Fusarium sp., respectively. To isolate antagonists aganist K-17 and K-28 pathogens, bacteria were isolated from various soybean-cultivated soils and screened by the inhibition zone method. A bacterial isolate(J-232) which inhibited growth of both pathogens was identified as Pseudomonas fluorescens and further examined. The culture filtrate of P. fluorescens J-232 (dilution rate of 500 times) inhibited the growth of Erwinia carotovora K-17 and Fusarium sp. K-28 both on potato dextrose agar medium and on soybean sprouts cultivated in vessel. The development of soybean sprouts rots was observed during cultivation by inoculation of soybean seeds with culture filtrate of both pathogens. The combined inoculation of soybean seeds with culture filtrate of antagonistic bacterium and that of pathogens prevented soybean sprouts rot, and the growth of soybean sprouts was similar to that of control. The soybean sprouts inoculated with antagonists culture filtrate alone did not develop soybean sprouts rot, and the growth of the seedlings was shown to be slightly promoted as compared with that of control.

• The Korean Journal of Mycology
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• v.35 no.2
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• pp.121-127
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• 2007

308 isolates of Ampelomyces sp. were isolated from powdery mildew fungi of 73 plant species in Korea for selection of biocontrol agents. An isolate 94013 isolated from powdery mildew fungus of red bean was selected as an effective biological control agent against cucumber powdery mildew in greenhouse. The morphological characteristics of the isolate is as follows. Pycnidia were sub-globose or elongated to pyriform, pale to dart brown, $52.5{\sim}82.5\;{\times}\;35.0{\sim}47.5\;(ave.\;62.5{\times}40.5){\mu}m$, and conidia were guttulate, straight cylindrical to fusiform, pale brown, $5.0{\sim}8.0\;{\times}\;2.5{\sim}4.3\;(ave.\;6.0{\times}3.0){\mu}m$. The isolate 94013 was identified as Ampelomyces quisqualis by morphological characteristics and rDNA ITS sequencing. The isolate A. quisqualis 94013 was different from that of the commercial product $AQ10^R$ in the rDNA ITS sequence.

• The Korean Journal of Mycology
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• v.37 no.1
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• pp.96-103
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• 2009

For the control of pathogenic microorganisms, Bacillus spp. were isolated from diseased pepper fruits in Korea. Among them, Bacillus sp. IUB158-03 showed high inhibitory effect on mycelial growth and spore germination of C. gloeosporioides and Botrytis cinerea. The strain was identified as B. amyloliquefaciens IUB158-03 based on its physiological, biochemical characteristics and Microlog analysis. The highest level of antifungal substances by B. amyloliquefaciens IUB158-03 were obtained when the bacterium was cultured in medium containing 2% soluble starch, 3% yeast extract, 0.5% tryptone, 0.5% $NH_4H_2PO_4$, and 1% NaCl (pH 6.0) at $25^{\circ}C$ for 72 hrs. The antifungal substances were purified by butanol extraction, silica gel column chromatography, preparative thin layer chromatography, and high performance liquid chromatography. The purified antifungal substance was confirmed $R_f$ 0.27 by TLC. This substance exhibited antifungal activity against Fusarium solani, Rhizoctonia solani, Botrytis cineria, Alternata alternaria of plant pathogenic fungi and Trichophyton mentagrophytes, Epidermophyton floccosum, Cryptococcus neoformans of human pathogenic fungi.

• Journal of Life Science
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• v.19 no.11
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• pp.1672-1678
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• 2009

The purified antifungal substances produced by Bacillus amyloliquefaciens IUB158-03 was positive to ninhydrin but negative to aniline, suggesting that the antifungal substance could be a peptide. FAB-MS, UV adsorption spectrum, and amino acid composition analysis revealed that the molecular weight of the antifungal substance was 1042 and that maximal adsorption was at 220 nm and 277 nm. The antifungal substance was composed of $Asn_3$, $Gln_2$, $Ser_1$, $Gly_1$, and $Tyr_1$. The composition and structural characteristics of antifungal substance were analysed by $^1H$-NMR spectrum, $^1H$-COSY, HMQC, which revealed that the compound belongs to the iturin A family. Temperature and pH had little effect on the stability of the antifungal substance in the ranges of $-70{\sim}121^{\circ}C$ and pH 6.0~10.0, respectively. It showed strong antibiotic activity against fungi. An in vitro cytotoxicity test using NIH3T3 cell showed that the antifungal substance does not have cytotoxicity. The number of circulating leukocytes and the hematobiological analysis of the mice administered with the antifungal substances was similar to those of the control group, indicating no cytotoxicity in vivo. Therefore, the antifungal substances extracted from culture broth of Bacillus amyloliquefaciens IUB158-03 have future potential as biocontrol agents against plant diseases caused by fungi.

• Journal of Life Science
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• v.26 no.10
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• pp.1163-1168
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• 2016

Plant growth-promoting rhizobacteria (PGPR) have gained worldwide importance and acceptance due to their agricultural benefits. These microorganisms are potential tools for sustainable agriculture, with effects on plant growth, biofertilization, induced systemic resistance, and biocontrol of plant pathogens. In this study, four different Pantoea species were isolated from field soil, and their plant growth-promoting characteristics were studied. Based on 16S rDNA gene sequencing analyses, the se were grouped into Pantoea ananatis, Pantoea citrea, Pantoea dispersa, Pantoea vagans and named as Pa1, Pc1, Pd1, Pv1, respectively. All of these strains have their ability for solubilization of insoluble phosphate depending on pH decrease at the range around pH 5 at 1days after inoculation and production of plant hormone indole acetic acid (IAA) with 85.3±16.3 μg/ml of Pa1, 183.9±16.8 μg/ml of Pc1, 28.8±17.3 μg/ml of Pd1 and 114.1±16.5 μg/ml of Pv1, respectively. Pa1, Pc1 and Pd1 also have high activity for production of gibberellin (GA₃) hormone with 331.1±19.2 μg/ml of Pa1, 288.5±16.8 μg/ml of Pc1, 309.2±18.2 μg/ml of Pd1, but Pv1 does not. Furthermore, all these species have significantly promoted the growth of the lettuce seedling plants at the range around 32~37% for fresh weight and 10~15% for shoot length enhancement, so that these microbe could be used as a potential bio-fertilizer agents.