• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.831-838
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• 2018

Trophic interactions of introduced biocontrol fungi with soil animals can be a key determinant in the fungal proliferation and activity. This study investigated the trophic interaction of an introduced biocontrol fungus with soil nematodes. The biocontrol fungus Trichoderma harzianum ThzID1-M3 and the fungivorous nematode Aphelenchoides sp. (10 per gram of soil) were added to nonsterile soil, and microbial populations were monitored for 40 days. Similar results were obtained when the experiment was duplicated. ThzID1-M3 stimulated the population growth of indigenous nematodes (p < 0.05), regardless of whether Aphelenchoides sp. was added. Without ThzID1-M3, indigenous nematodes did not increase in number and the added Aphelenchoides sp. nematodes almost disappeared by day 10. With ThzID1-M3, population growth of nematodes was rapid between 5 and 10 days after treatment. ThzID1-M3 biomass peaked on day 5, dropped at day 10, and then almost disappeared at day 20, which was not influenced by the addition of nematodes. In contrast, a large quantity of ThzID1-M3 hyphae were present in a heat-treated soil in which nematodes were eliminated. Total fungal biomass in all treatments peaked on day 5 and subsequently decreased. Addition of nematodes increased the total fungal biomass (p < 0.05), but ThzID1-M3 addition did not affect the fungal biomass. Hyphae of total fungi when homogenously distributed did not support the nematode population growth; however, hyphae of the introduced fungus did when densely localized. The results suggest that soil fungivorous nematodes are an important constraint on the hyphal proliferation of fungal agents introduced into natural soils.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.296-304
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• 1994

Antibiotic substances were produced by Bacillus subtilis YB-70, a potential biocontrol agent found to suppress root-rot of eggplant (Solanum melonggena L) caused by Fusarium solani, in a dextrose glutamate medium and isolated by isoelectric precipitation. Partial purification was performed by column chromatography on silica gel with two solvent systems: chloroform-methanol and methanol-chloroform-water as eluting solvents, This active fraction YBS-1 s contained antifungal activity were soluble in ethanol, methanol, and water, but were not soluble in other solvents including acetone, butanol, ethyl ether, dimethylformamide, propanol, and etc. High performance liquid chromatography and thin layer chromatographic separation of YBS-1s showed that they have been composed of three biological active bands that were named YBS-1A, -1B, and -1C. The substances were stable to heat and resistant to protease. YBS-1s were active against a wide range of plant pathogenic fungi but did not inhibit the growth of bacteria and yeasts. They were not only fungicidal but also fungistatic against chlamydospores of F. solani. The $ED_{50}$ values for the chlamydospore germination and the germ-tube growth of F. solani were $O.725\mu\textrm{m}/ml\;and\;O.562\mu\textrm{m}/ml$, respectively. Microscopic observations proved the substances restricted the growth of phytopathogenic fungus F. solani by spore burst followed by dissolving of its germ-tube, and caused abnormal hyphal swelling after application to chlamydospores or growing hyphae. Cultural filtrate of B; subtilis YB-70 also suppressed the development of root-rot of eggplant in pot tests.

• The Plant Pathology Journal
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• v.27 no.1
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• pp.68-77
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• 2011

Fifty five species of medicinal plant materials were tested for their antifungal activity in vitro against Rhizoctonia solani AG 2-1 and Trichoderma harzianum to select plant species that can be used to improve the biocontrol efficacy of T. harzianum. Six species were effective against R. solani AG 2-1 but were also antagonistic to T. harzianum, except for Cinnamomum loureirii stem bark (CSB). CSB inhibited mycelial growth of R. solani AG 2-1 by 73.7% but showed an inhibitory effect on mycelial growth of T. harzianum by only 2.2%. Scanning electron microscophs showed that the CSB treatment resulted in deformed R. solani AG 2-1 hyphal cells, and transmission electron microscophs revealed degenerated cell structures such as degenerated cytoplasm and disentangled cell wall and the accumulation of electron-dense inclusions (asterisks) in the CSB treatment. The biocontrol efficacy of radish damping-off increased greatly following the combined treatments of T. harzianum and CSB and the combined treatment increased efficacy from 6.4-23.1% to 37.1-87.3% compared with either treatment alone. CSB did not affect T. harzianum population growth, as it was almost the same in rice-bran peat medium (culture) amended with 0.1% and 1.0% CSB powder as in non-amended medium. The formulation of T. harzianum in rice-bran peat medium amended with CSB powder reduced the severity of radish damping-off by 80.6%, suggesting that T. harzianum and CSB can be formulated as a biocontrol product for the control of R. solani AG 2-1.

• Journal of Mushroom
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• v.10 no.3
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• pp.109-114
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• 2012

To develop new variety of oyster mushroom, 63 intra-specific hybrids between the strain Suhan and #Nongi201 were developed using hyphal anastomosis technique in 2004. The Po2008-275 hybrid between the dikaryon strain 04-154(Suhan x #Nongi201) and the monokaryon strain derived from ASI2487 were developed using hyphal anastomosis in 2008. The Po2008-275 was shown the best cultural characteristics, selected to be a new variety and named as 'Guseol'. The new commercial strain, 'Guseol' had dark grey pilei and grows well under spring and autumn conditions in Korea. The fruiting bodies of 'Guseol' were of an excellent quality in that not only the stipe was thick and long but also the pileus was small and hard. The optimum temperatures for mycelial growth and fruiting body development were $25{\sim}30^{\circ}C$ and $10{\sim}16^{\circ}C$, respectively. Time period required for the initiation of the first fruiting body was about 3 to 5 days depending on the temperatures. The shape of fruiting body was thin funnel shape. Fruiting body production per box($43{\times}43{\times}12cm$) was about $1545{\pm}400.9g$ which was almost 137% quantity compared to that of parental strain 04-154. Relatively low temperature incubation ($11^{\circ}C$) resulted in the development of better quality of 'Guseol' mushrooms. When two different media including potato dextrose medium and mushroom complete medium were compared, the mycelial growth of this mushroom were much faster in mushroom complete medium. Similar results were observed with other variety '#Chunchu2'. Analysis of the genetic characteristics of the new commercial strain 'Guseol' showed a major DNA profile as that of the parental 04-154 when primer URP 1, primer URP 2 and primer URP 5 were used, but different to '#Chunchu2' that was used as a control. This new variety of the dark grey oyster mushroom had smart and high quality image that corresponds well to "health food". We therefore expect that this new strain will satisfy the consumers demand for variety and excellent mushrooms.

• Journal of Microbiology and Biotechnology
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• v.23 no.6
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• pp.856-863
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• 2013

Application of rhizospheric fungi is an effective and environmentally friendly method of improving plant growth and controlling many plant diseases. The current study was aimed to identify phytohormone-producing fungi from soil, to understand their roles in sesame plant growth, and to control Fusarium disease. Three predominant fungi (PNF1, PNF2, and PNF3) isolated from the rhizospheric soil of peanut plants were screened for their growth-promoting efficiency on sesame seedlings. Among these isolates, PNF2 significantly increased the shoot length and fresh weight of seedlings compared with controls. Analysis of the fungal culture filtrate showed a higher concentration of indole acetic acid in PNF2 than in the other isolates. PNF2 was identified as Penicillium sp. on the basis of phylogenetic analysis of ITS sequence similarity. The in vitro biocontrol activity of Penicillium sp. against Fusarium sp. was exhibited by a 49% inhibition of mycelial growth in a dual culture bioassay and by hyphal injuries as observed by scanning electron microscopy. In addition, greenhouse experiments revealed that Fusarium inhibited growth in sesame plants by damaging lipid membranes and reducing protein content. Co-cultivation with Penicillium sp. mitigated Fusarium-induced oxidative stress in sesame plants by limiting membrane lipid peroxidation, and by increasing the protein concentration, levels of antioxidants such as total polyphenols, and peroxidase and polyphenoloxidase activities. Thus, our findings suggest that Penicillium sp. is a potent plant growth-promoting fungus that has the ability to ameliorate damage caused by Fusarium infection in sesame cultivation.

• The Plant Pathology Journal
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• v.20 no.3
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• pp.177-183
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• 2004

Phenylacetic acid (PAA) was evaluated for in vitro anti-oomycete activity and in vivo control efficacy against Phytophthora capsici. Microscopic observation revealed that the high level of anti-oomycete activity of PAA (10 $\mu\textrm{g}$/ml) against P. capsici is mainly due to the lytic effect on zoospores. Zoospore lysis began in the presence of 5 u$\mu\textrm{g}$/ml of PAA and most of the zoospores were collapsed at 10 $\mu\textrm{g}$/ml. PAA showed inhibitory activity against the zoospore germination and hyphal growth of P. capsici at the concentration of 50 $\mu\textrm{g}$/ml. In the glasshouse, the protective effect of PAA against Phytophthora blight was high on pepper plants when treated just before inoculation with P. capsici. In the artificially infested field, protection of pepper plants against the Phyto-phthora epidemic was achieved at a considerable level by PAA treatment.

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.20-20
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• 2015

Endophytic fungi are microorganisms inhabiting living plant tissues without causing apparent harm to the host. They are drawing increasing attention due to their ability to produce various bioactive compounds as well as their effects on host growth and resistance to biotic and abiotic stresses. As a first step to assess biodiversity of plant associated fungi in Korea and the following evaluation on diverse biological activities, we are collecting endophytic fungi from plant in wild followed by systematic long-term storage in liquid nitrogen. Molecular identification using ITS sequences was also incorporated for pure culture by hyphal tip isolation. As of April 2015, about 1,400 fungal strains had been isolated from about 170 plant taxa. Fungal isolates belonging to Pleosporales, Diaporthales, Glomerellales, Hypocreales, and Xylariales were the most abundant. These collections are being used for several complementary researches, including screening of isolates with novel bioactive compounds or conferring drought stress resistance, phylogenetic and genomic study. Genome sequencing was performed for 3 isolates, one Xylaria sp. strain JS573 producing griseofulvin, an antifungal compound, and two Fusarium spp. strains JS626 and JS1030, which are assumed to be new species found in Korea. More detailed analysis on these genomes will be presented. These collections and genome informations will serve as invaluable resources for identifying novel bioactive materials in addition to expand our knowledge on fungal biodiversity.

• The Plant Pathology Journal
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• v.31 no.3
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• pp.278-289
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• 2015

Indigenous strains of Trichoderma species isolated from rhizosphere soils of Tea gardens of Assam, north eastern state of India were assessed for in vitro antagonism against two important tea fungal pathogens namely Pestalotia theae and Fusarium solani. A potent antagonist against both tea pathogenic fungi, designated as SDRLIN1, was selected and identified as Trichoderma viride. The strain also showed substantial antifungal activity against five standard phytopathogenic fungi. Culture filtrate collected from stationary growth phase of the antagonist demonstrated a significantly higher degree of inhibitory activity against all the test fungi, demonstrating the presence of an optimal blend of extracellular antifungal metabolites. Moreover, quantitative enzyme assay of exponential and stationary culture filtrates revealed that the activity of cellulase, ${\beta}$-1,3-glucanase, pectinase, and amylase was highest in the exponential phase, whereas the activity of proteases and chitinase was noted highest in the stationary phase. Morphological changes such as hyphal swelling and distortion were also observed in the fungal pathogen grown on potato dextrose agar containing stationary phase culture filtrate. Moreover, the antifungal activity of the filtrate was significantly reduced but not entirely after heat or proteinase K treatment, demonstrating substantial role of certain unknown thermostable antifungal compound(s) in the inhibitory activity.

• Journal of Microbiology and Biotechnology
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• v.6 no.6
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• pp.439-444
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• 1996

A bacterial strain, designated as WY22, producing extracellular chitinase was isolated from the soil around the Youngduck area, after enrichment culture in a medium containing $1{\%}$ (w/v) wet colloidal chitin as a sole carbon source. The isolate was identified as a strain of Bacillus sp. based on its morphological and physiological characteristics. It was observed that Bacillus sp. WY22 could inhibit the growth of Fusarium oxysporum with hyphal extention-inhibition assay on potato dextrose agar plate supplemented with $1{\%}$ collidal chitin. Optimum culture conditions of Bacillus sp. WY22 were examined for chitinase production in a chitin medium. High level production of chitinase was observed not only in the chitin medium but in a medium supplemented with $1{\%}$ N-glucosamine or lactose instead of chitin. The optimum concentrations of colloidal chitin and yeast extract were 3.0 and $0.5{\%}$, and the optimum culture conditions for initial pH of medium and temperature were 7.0 and $30^{\circ}C$, respectively, for the production of chitinase.

• Research in Plant Disease
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• v.16 no.3
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• pp.323-325
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• 2010

The stem rot of sunflower (Helianthus annuus) occurred sporadically in the experimental field of Gyeongsangnam-do Agricultural Research and Extension Services, on September, 2009. The infected plants were wilted and water-soaked brown spots were formed on the stem, than infected stems were mostly died. White mycelial mats were spread over lesions, and then sclerotia were formed on stem and near soil line. The sclerotia were globoid in shape, 1~3 mm in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$ and the hyphal width was $4{\sim}8\;{\mu}m$. The typical clamp connections were observed in the hyphae of the pathogenic fungus. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii. This is the first report on the stem rot of sunflower by S. rolfsii in Korea.