• 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.

• Korean Journal of Organic Agriculture
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• v.25 no.1
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• pp.113-124
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• 2017

Cotton aphid (Aphis gossypii) and green peach aphid (Myzus persicae) are serious pests damaging various crops including vegetables such as pepper, cucumber, and Chinese cabbage. We conducted a study to control two aphids with secondary metabolite of entomopathogenic fungus Beauveria bassiana. A B. bassiana was already selected as a high virulence isolate against cotton aphid and green peach aphid. The culture filtrate of the isolate showed high pathogenicity against both aphids as 100% mortality against cotton aphid 3 days after treatment and 99% against green peach aphid 5 days after treatment. A different fraction extracts with $CHCl_3$ : MeOH of B. bassiana culture filtrate (30:1, 50:1, 70:1, 90:1, 100:1; v/v) through silica gel column chromatography showed different control effect to aphids. Among them, 50:1 ($CHCl_3$ : MeOH) fraction had highest mortality as 77.3% and 75.4% against A. gossypii and M. persicae, respectively. A mixture of each fraction (1:1) had no synergistic effects because control effect of every mixture was lower than only 50:1 extract; for example, mortality of 50:1 + 70:1 showed $2^{nd}$ highest as 72% of cotton aphid and 70.2% of green peach aphid and other mixtures were lower than these values. In future we will study the identification and mass production of aphicidal compound isolated from 50:1 fraction to develop stable aphid control agent.

• Journal of Microbiology and Biotechnology
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• v.10 no.3
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• pp.287-292
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• 2000

Recombinant Aspergillus niger was constructed to express and secrete a biologically active murine granulaocyte macrophage-colony stimulating factor (mGM-CSF). A 500 bp fragment encoding the signal peptide and terminator of glyceraldehyde-3-phosphate dehydrogenase (gpd). The hygromycin phosphotrasferase gene (hph) was used as a selection marker for the fungal transformants. An expression vector was introduced into A. niger ATCC 9642, and a Northern blot analysis indicated the presence of a considerable amount of transcripts from the introduced mGM-CSF. The biological activity of recombinant mGM-CSF (rmGM-CSF) isolated from the culture filtrate was confirmend by measuring the proliferationof the GM-CSF dependent FDC-P1 cell line. It appeared that rmGM-CSF was amenable to the proteolytic activity produced by A. niger, since biological actibity was only observed when the transformants were grown in a protease-repressing medium, and the activity of rmGM-CSF dramatically decreased with an increase of age of the culture. The yield of rmGM-CSF, as determined by ELISA. was 640 ng/l of culture filtrate. Accordingly, its specific activity is estimated to be approximately two-and-a-half times higher than that of a commercial preparation from E. coli.

• Korean Journal Plant Pathology
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• v.11 no.4
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• pp.292-297
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• 1995

We developed an in vitro assay method for evaluating plant growth promotion and providing an evidence that the growth promotion is rendered by growth enhancing factors. The amendment of culture filtrates of Trichoderma harzianum T95 and Gliocladium virens G872 and G872B in Murashige and Skoog (MS) agar medium enhanced the cotyledon growth of cucumber in terms of fresh weight and primary leaf area of cucumber cotyledon cuttings, of which the treatment of G. virens G872B was the most effective. The mycelial culture filtrate of G872B was more effective in the growth promotion than its conidial germling filtrate. The addition of 1% sucrose in MS mineral medium with 0.1% culture filtrates of the antagonists (T95 and G872B) was optimum for enhancing the effect of the filtrates on the growth of cotyledon cuttings in vitro. When cucumber seeds treated with G872B, Pseudomonas putida Pf3 or the G872B-Pf3 mixture were planted in a greenhouse, the rate of seed germination, biomass of shoot and root, and yield of cucumber fruits were increased, especially by G872B or the G872B-Pf3 mixture. Correspondingly, cucumber fruit yields in early to middle-cycles of harvest were significantly greater in the plots of G872B than the control and Pf3-treated plots, and the final yield was highest in the plots of the G872B-Pf3 mixture applications.

• Mycobiology
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• v.43 no.1
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• pp.87-91
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• 2015

Eighteen endophytic fungi with different colony morphologies were isolated from the roots of Nymphoides peltata growing in the Dalsung wetland. The fungal culture filtrates of the endophytic fungi were treated to Waito-c rice seedling to evaluate their plant growth-promoting activities. Culture filtrate of Y2H0002 fungal strain promoted the growth of the Waito-c rice seedlings. This strain was identified on the basis of sequences of the partial internal transcribed spacer region and the partial beta-tubulin gene. Upon chromatographic analysis of the culture filtrate of Y2H0002 strain, the gibberellins (GAs: $GA_1$, $GA_3$, and $GA_4$) were detected and quantified. Molecular and morphological studies identified the Y2H0002 strain as belonging to Aspergillus clavatus. These results indicated that A. clavatus improves the growth of plants and produces various GAs, and may participate in the growth of plants under diverse environmental conditions.

• The Plant Pathology Journal
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• v.38 no.1
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• pp.33-45
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• 2022

To screen antagonistic fungi against plant pathogens, dual culture assay (DCA) and culture filtrate assay (CFA) were performed with unknown soil-born fungi. Among the different fungi isolated and screened from the soil, fungal isolate ANU-301 successfully inhibited growth of different plant pathogenic fungi, Colletotrichum acutatum, Alternaria alternata, and Fusarium oxysporum, in DCA and CFA. Morphological characteristics and rDNA internal transcribed spacer sequence analysis identified ANU-301 as Aspergillus terreus. Inoculation of tomato plants with Fusarium oxysporum f. sp. lycopersici (FOL) induced severe wilting symptom; however, co-inoculation with ANU-301 significantly enhanced resistance of tomato plants against FOL. In addition, culture filtrate (CF) of ANU-301 not only showed bacterial growth inhibition activity against Dickeya chrysanthemi (Dc), but also demonstrated protective effect in potato tuber against soft rot disease. Gas chromatography-tandem mass spectrometry analysis of CF of ANU-301 identified 2,4-bis(1-methyl-1-phenylethyl)-phenol (MPP) as the most abundant compound. MPP inhibited growth of Dc, but not of FOL, in a dose-dependent manner, and protected potato tuber from the soft rot disease induced by Dc. In conclusion, Aspergillus terreus ANU-301 could be used and further tested as a potential biological control agent.

• The Plant Pathology Journal
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• v.22 no.3
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• pp.289-294
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• 2006

Two isolates of mucous bacteria, mc75 and pc78, were isolated from fungal culture plate as culture contaminants with an interesting swarming motility. Both isolates were identified as Pseudomonas fluorescens based on microscopy, biochemical analysis, Biolog test and DNA sequence analysis of the 16S rRNA gene. Both strains have the exactly the same 16S rRNA gene sequences, and yet their biological control activity were not identical each other. In vitro analysis of antagonistic activity of two isolates against several plant pathogenic fungi indicated that both produced diffusible and volatile antifungal compounds of unknown identities. Treatment of the bacterial culture of P. fluorescens pc78 and its culture filtrate exhibited a strong biological control activity against rice sheath blight in vivo among six plant diseases tested. More effective disease control activity was obtained from treatment of bacterial culture than that of culture filtrate. Therefore, in addition to antifungal compound and siderophore production, other traits such as biofilm formation and swarming motility on plant surface may contribute to the biological control activity of P.fluorescens pc78 and mc75.

• Applied Biological Chemistry
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• v.36 no.5
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• pp.352-357
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• 1993

The effects of culture broth filtrates, sugar changes and utilizationon the growth and acid production of P. freudenreichii KFCC 31227and L. acidophilus KFCC 32825 were investigated in S.G.Y.(Skim milk, glucose, yeast extract) and SMW (skin milk whey)medium by the single and mixed cultures. The growth and acid production by mixed culture and in cultured broth filtrate of the other party were more affected than those of single culture and self-cultured broth filtrate. When the two strains were cultured, P. freudenreichii KFCC 31227 utilized with lactose more than glucose and L. acidophilus KFCC 32825 was glucose more than lactose in the growth and acid production. The mixed culture of two strains was more affected to sugar utilization than single culture. This result was considered due to the synergistic effect by interaction of these two strains in mixed culture.

• International Journal of Industrial Entomology and Biomaterials
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• v.35 no.1
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• pp.58-62
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• 2017

The two-spotted spider mite (Tetranychus urticae) has sustained damage on more than 200 host plants worldwide. Many farmers have relied on chemical acaricides to control mite, but the abuse of acaricides has caused serious resistance to mite. To overcome this problem, microbial control using entomopathogenic fungi have been studied. Entomopathogenic fungi have been an important role against the control of pest, and most of their culture products have been demonstrated to have virulence against pest population. In this study, we evaluated and compared the virulence of culture filtrates, aerial conidia and blastospores of selected Metarhizium anisopliae 4-2 and Beauveria bassiana 2R-3-3-1, respectively, among two-spotted spider mite-pathogenic fungi. As a result, the virulence was confirmed in all treatments, and the accumulated mortality rates were between 77 and 100% within 7 days. Especially, treatment with the fungal culture filtrate alone exhibited quite high virulence, and combined treatment with aerial conidia or blastospores enhanced activity. However, the median lethal time of treatments was not significantly different. When two isolates were compared, M. anisopliae 4-2 showed higher virulence than B. bassiana 2R-3-3-1. These results suggest that the selected two fungal isolates and their culture products could be used effectively for the control of two-spotted spider mite.

• Weed & Turfgrass Science
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• v.2 no.2
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• pp.202-206
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• 2013

Biocontrol potential of an isolate of Helicosporium spp. against Rhizoctonia solani, Fusarium oxysporium and Phytophthora drechsleri was evaluated in vitro and in vivo. A selected biocontrol agent designated as Helicosporium 0635BP strongly inhibited growth and lysed mycelium of Rhizoctonia solani and Fusarium oxysporium on PDA. Autoclaved culture filtrate of the agent also completely inhibited growth of the turfgrass large patch pathogen, R. solani AG2-2 IV at the concentration of 50 ml $L^{-1}$. The pathogen was killed when dipped under the 20% filtrate for four hours or 50% for one hr. In a field trial, plots applied with the crude or times diluted culture filtrate showed 100% control efficacy of the turfgrass large patch as a chemical applied for a comparison. Results indicated that Helicosporium 0635BP is a promising biocontrol agent on control of the turfgrass large patch disease and its culture filtrate contained unknown heat suitable antifungal substance (s). Further studies on mass production, purification and identification of the unknown compound (s) are in progress for practical use.