• Journal of Microbiology and Biotechnology
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• v.33 no.5
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• pp.607-620
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• 2023

The biocontrol approach using beneficial microorganisms to control crop diseases is becoming an essential alternative to chemical fungicides. Therefore, new and efficient biocontrol agents (BCA) are needed. In this study, a rhizospheric actinomycete isolate showed unique and promising antagonistic activity against three of the most common phytopathogenic fungi, Fusarium oxysporum MH105, Rhizoctonia solani To18, and Alternaria brassicicola CBS107. Identification of the antagonistic strain, which was performed according to spore morphology and cell wall chemotype, suggested that it belongs to the Nocardiopsaceae. Furthermore, cultural, physiological, and biochemical characteristics, together with phylogenetic analysis of the 16S rRNA gene (OP869859.1), indicated the identity of this strain to Nocardiopsis alba. The cell-free filtrate (CFF) of the strain was evaluated for its antifungal potency, and the resultant inhibition zone diameters ranged from 17.0 ± 0.92 to 19.5 ± 0.28 mm for the tested fungal species. Additionally, the CFF was evaluated in vitro to control Fusarium wilt disease in Vicia faba using the spraying method under greenhouse conditions, and the results showed marked differences in virulence between the control and treatment plants, indicating the biocontrol efficacy of this actinomycete. A promising plant-growth promoting (PGP) ability in seed germination and seedling growth of V. faba was also recorded in vitro for the CFF, which displayed PGP traits of phosphate solubilization (48 mg/100 ml) as well as production of indole acetic acid (34 ㎍/ml) and ammonia (20 ㎍/ml). This study provided scientific validation that the new rhizobacterium Nocardiopsis alba strain BH35 could be further utilized in bioformulation and possesses biocontrol and plant growth-promoting capabilities.

• Journal of Ginseng Research
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• v.40 no.4
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• pp.315-324
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• 2016

Background: Biocontrol agents are regarded as promising and environmental friendly approaches as agrochemicals for phytodiseases that cause serious environmental and health problems. Trichoderma species have been widely used in suppression of soil-borne pathogens. In this study, an endophytic fungus, Trichoderma gamsii YIM PH30019, from healthy Panax notoginseng root was investigated for its biocontrol potential. Methods: In vitro detached healthy roots, and pot and field experiments were used to investigate the pathogenicity and biocontrol efficacy of T. gamsii YIM PH30019 to the host plant. The antagonistic mechanisms against test phytopathogens were analyzed using dual culture, scanning electron microscopy, and volatile organic compounds (VOCs). Tolerance to chemical fertilizers was also tested in a series of concentrations. Results: The results indicated that T. gamsii YIM PH30019 was nonpathogenic to the host, presented appreciable biocontrol efficacy, and could tolerate chemical fertilizer concentrations of up to 20%. T. gamsii YIM PH30019 displayed antagonistic activities against the pathogenic fungi of P. notoginseng via production of VOCs. On the basis of gas chromatography-mass spectrometry, VOCs were identified as dimethyl disulfide, dibenzofuran, methanethiol, ketones, etc., which are effective ingredients for antagonistic activity. T. gamsii YIM PH30019 was able to improve the seedlings' emergence and protect P. notoginseng plants from soil-borne disease in the continuous cropping field tests. Conclusion: The results suggest that the endophytic fungus T. gamsii YIM PH30019 may have a good potential as a biological control agent against notoginseng phytodiseases and can provide a clue to further illuminate the interactions between Trichoderma and phytopathogens.

• The Plant Pathology Journal
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• v.25 no.1
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• pp.62-69
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• 2009

In this study, we characterized the bacterial strain KJ2C12 in relation with its biocontrol activity against Phytophthora capsici on pepper, and identified this strain using morphological, physiological, biochemical, fatty acid methyl ester, and 16S rRNA gene sequence analyses. Strain KJ2C12 significantly (P=0.05) reduced both final disease severity and areas under the disease progress curves of 5-week-old pepper plants inoculated with P. capsici compared to buffer-treated controls. As for the production of antibiotics, biofilms, biosurfactant, extracellular enzyme, HCN, and swarming activity, strain KJ2C12 produced an extracellular enzyme with protease activity, but no other productions or swarming activity. However, Escherichia coli produced weak biofilm only. Strain KJ2C12 could colonize pepper roots more effectively in a gnotobiotic system using sterile quartz sand compared to E. coli over 4 weeks after treatments. However, no bacterial populations were detected in 10 mM $MgSO_4$ buffer-treated controls. Strain KJ2C12 produced significantly higher microbial activity than the $MgSO_4$-treated control or E. coli over 4 weeks after treatments. Bacterial strain KJ2C12 was identified as Bacillus luciferensis based on morphological, physiological, and biochemical characteristics as well as FAME and 16S rRNA gene sequence analyses. In addition, these results suggested that B. luciferensis strain KJ2C12 could reduce Phytophthora blight of pepper by protecting infection courts through enhanced effective root colonization with protease production and an increase of soil microbial activity.

• The Plant Pathology Journal
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• v.21 no.3
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• pp.275-282
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• 2005

A chitinolytic bacterium, Chromobacterium sp. strain C-61, was found strongly antagonistic to Rhizoctonia solani, a causal agent of damping-off of eggplant. In this study, the biocontrol activity and enzymatic characteristics of strain C-61 were compared with its four Tn5 insertion mutants (C61-A, -B, -C, and -D) that had lower chitinolytic ability. The chitinase activity of a 2-day old culture was about $76\%,\;49\%\;and\;6\%$ level in C61-A, C61-B and in C61-C, respectively, compared with that of strain C-61. The $\beta-N-acetylhexosaminidase$(Nahase) activity was little detected in strain C-61 but increased largely in C-61A, C61-B and C61-C. Activities of chitinase and Nahase appeared to be negatively correlated in these strains. Another mutant, C-61D, produced no detectable extracellular chitinase and Nahase. The in vitro and in vivo biocontrol activities of strain C-61 and its mutants were closely related to their ability to produce chitinase but not Nahase. No significant differences in population densities between strain C-61 and its mutants were observed in soil around eggplant roots. The results of SDS-PAGE and isoelectrofocusing showed that a major chitinase of strain C-61 is 54-kDa with pI of approximately 8.5. This study provides evidence that the biocontrol activity of Chromobacterium sp. strain C-61 against Rhizoctonia solani depends on the ability to produce chitinase with molecular weight of 54-kDa and pI of 8.5.

• Research in Plant Disease
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• v.12 no.3
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• pp.267-271
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• 2006

Botrytis cinerea Pers. was found to be highly virulent to the grapevine plant, especially in greenhouse condition. Pseudomonas species play key roles for the biocontrol of many plant diseases especially in soil. Of the 83 isolates of Pseudomonas spp., a bacterial strain P84, isolated from tomato rhizosphere, was shown to suppress a wide range of phytopathogenic fungi in vitro. The isolate was identified as Pseudomonas putida on the basis of its bacteriological and genetic characteristics. The P. putida P84 strain carry the phlD gene for 2,4-diacetylphloroglucinol biosynthesis and may produce the antibiotics as an antagonistic mechanism involved in biocontrol. The antagonistic activity of the bacterium has a promising implication for its use as a biocontrol agent to control grapevine gray mold.

• Research in Plant Disease
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• v.12 no.3
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• pp.260-266
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• 2006

Pythium blight caused by Pythium spp. is one of major diseases in putting green of golf course. In this study, microorganisms which are anatgonistic to Pythium aphanidermatum, a pathogen of pythium blight, were selected primary through in vitro tests, dual culture method and triple layer agar diffusion method. In vivo test against pythium blight were conducted to select the best candidate biocontrol microorganism by pot experiment in a plastic house. Bacillus subtilis GB-0365 was finally selected as a biocontrol agent against pythium blight. Relative Performance Indies(RPI) was used as a criterion of selecting potential biocontrol agent. B. subtilis GB-0365 showed resistance to major synthetic agrochemicals used in golf course. Alternative application of synthetic agrochemicals and B. subtilis GB-0365 was most effective to successfully contol pythium blight. B. subtilis GB-0365 suppressed the development of pythium bight of bentgrass by 56.4% as compared to non-treated control and its disease control efficacy was 60.9% of a synthetic fungicide Oxapro(WP) efficacy. B. subtilis GB-0365 has a potential to be a biocontrol agent for control of pythium blight.

• 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.

• Korean Journal of Environmental Biology
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• v.20 no.2
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• pp.130-135
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• 2002

Species of Genus Trichoderma are commercially applied as biological control agents against fungal Pathogens. A powerful biocontrol agent, Trichoderma sp. SJG-99721 was isolated from 305 isolates by morphological characters, chitinase activities and antifungal activities against Phytophthora capsiei. The isolate was identified as Trichoderma harzianum from various features such as growth rate at $27^\circ{C}$, significant growth ratio of $27^\circ{C}$ to $17^\circ{C}$, amount of aerial mycelium, types of branching: system, and disposition patterns of phialide and phialospore. Trichoderma harzianum SJG-99721 have been shown to act as a powerful biological agent against fungal phytopathogens; Botrytis cinerea, Rhizoctonia solani, Phytophthora cryptogea, Phytophthora capsiei, Sclerotinia sclerotiorum, Mycoshaerella melonis, Alternaria sotani, Fusarium oxysporum, Collectotrichum gloesporioodes, Alternaria alternata, Phythium ultimum, Phytophthora drechsleri, Pyricularia grisea.

• Mycobiology
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• v.46 no.2
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• pp.138-146
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• 2018

Two-hundred and fifty-five strains of actinomycetes isolated from soil samples were screened for their antagonistic activities against four well-known wood decay fungi (WDF), including a brown rot fungus, Gloeophyllum trabeum and three white rot fungi Donkioporia expansa, Trametes versicolor, and Schizophyllum commune. A dual culture assay using culture media supplemented with heated or unheated culture filtrates of selected bacterial strains was used for the detection of their antimicrobial activity against four WDF. It was shown that Streptomyces atratus, S. tsukiyonensis, and Streptomyces sp. greatly inhibited the mycelial growth of the WDF tested compared with the control. To evaluate the biocontrol efficacy of S. atratus, S. tsukiyonensis, and Streptomyces sp., wood blocks of Pinus densiflora inoculated with three selected Streptomyces isolates were tested for weight loss, compression strength (perpendicular or parallel to the grain), bending strength, and chemical component changes. Of these three isolates used, Streptomyces sp. exhibited higher inhibitory activity against WDF, especially G. trabeum, as observed in mechanical and chemical change analyses. Scanning electron microscopy showed that cell walls of the wood block treated with Streptomyces strains were thicker and collapsed to a lesser extent than those of the non-treated control. Taken together, our findings indicate that Streptomyces sp. exhibits the potential to be used as a biocontrol agent for wood decay brown rot fungus that causes severe damage to coniferous woods.

• Research in Plant Disease
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• v.11 no.2
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• pp.162-166
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• 2005

Disease progress of gray blight of tea (Camellia sinensis O. Kuntze) cv. Yabukita was investigated during the growing season of 2004 at Boseong Tea Experiment Station, Jeonnam Agriculture Research and Extension Service, Boseong, Jeonnam. The disease began to occur from late June and peaked in late July. Antagonistic bacteria against Pestalotiopsis longiseta, the causal pathogen of causing gray blight of tea plants were isolated from phylloplanes of tea plants. An isolate BD0310 which showed the strongest antifungal activity against the pathogen but nonpathogenic to tea plants was selected as a biocontrol agent for the gray blight. The isolate was identified as Bacillus subtilis based on its cultural, morphological, and biochemical characterization and 16S rDNA sequence analysis.