• The Plant Pathology Journal
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• v.16 no.5
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• pp.286-289
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• 2000

Mechanol extracts of three cold-tolerant eucalyptus trees-Eucalyptus darlympleana, E. gunnii and E. unigera were screened for antimicrobial activity against twenty two phyto-pathogenic fungi and six food-borne bacterial pathogens. E. unigera showed the antagonistic activity against all the tested pathogens. Among the tested fungal pathogens, Pythium species were highly sensitive to the leaf extracts. Especially, P. vanterpoolii, a causal agent of leaf blight in creeping bentgrass (Agrostis palustris), was completely inhibited by the extracts. The eucalyptus extracts were also effective in inhibiting the fungal growth of Botrytis cinerea and Phomopsis sp. isolated from the lesions of kiwifruit soft rot during post-harvest storage. Escherichia coli O-157 was less sensitive to the inhibition than the other bacterial pathogens tested. It was likely that Gram positive bacteria-Bacillus subtilis and Streptococcus mutans were more sensitive to the eucalyptus extracts than Gram negative bacteria-Escherichia coli, Salmonella enteritidis and Pseudomonas aeruginosa. Our findings suggest that the cold-tolerant eucalyptus species have antimicrobial properties that can serve the development of novel fungitoxic agents or food preservatives.

• The Plant Pathology Journal
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• v.30 no.1
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• pp.102-108
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• 2014

The bacterial strain T-9, which shows strong antifungal activity, is isolated from the soils of Samcheok, Gangwondo and identified as Paenibacillus kribbensis according to morphological and taxonomic characteristics and 16S rRNA gene sequence analysis. The P. kribbensis strain T-9 strongly inhibits the growth of various phytopathogenic fungi including Botrytis cinerea, Colletotricum acutatum, Fusarium oxysporum f. sp. radicis-lycopersici, Magnaporthe oryzae, Phytophthora capsici, Rhizoctonia solani, and Sclerotium cepivorum in vitro. Also, the P. kribbensis strain T-9 exhibited similar or better control effects to plant diseases than in fungicide treatment through in vivo assays. In the 2-year greenhouse experiments, P. kribbensis strain T-9 was highly effective against clubroot. In the 2-year field trials, the P. kribbensis strain T-9 was less effective than the fungicide, but reduced clubroot on Chinese cabbage when compared to the control. The above-described results indicate that the strain T-9 may have the potential as an antagonist to control various phytopathogenic fungi.

• The Plant Pathology Journal
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• v.23 no.3
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• pp.180-186
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• 2007

The biocontrol agent, Serratia plymuthica A21-4, has been developed for controlling pepper Phytophthora blight. Serratia plymuthica A21-4 strongly inhibits the mycelial growth, zoospore formation, and cyst germination of Phytophthora capsici in vitro. The application of a cell suspension of strain A21-4 to pepper plants in pot experiments and in greenhouse successfully controlled the disease. The bacteria produced a potent antifungal substance which was a key factor in the suppression of Phytophthora capsici. The most active chemical com-pound was isolated and purified by antifungal activity-guided fractionation. The chemical structure was identified as a chlorinated macrolide $(C_{23}H_{31}O_8Cl)$ by spectroscopic (UV, IR, MS, and NMR) data, and was named macrocyclic lactone A21-4. The active compound significantly inhibited the formation of zoosporangia and zoospore and germination of cyst of P. capsici at concentrations lower than $0.0625{\mu}g/ml$. The effective concentrations of the macrocyclic lactone A21-4 for $ED_{50}$ of mycelial growth inhibition were $0.25{\mu}g/ml,\;0.25{\mu}g/ml,\;0.30{\mu}g/ml \;and\;0.75{\mu}g/ml$ against P. capsici, Pythium ultimum, Sclerotinia sclerotiorum and Botrytis cinerea, respectively.

• Korean Journal of Medicinal Crop Science
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• v.14 no.4
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• pp.202-205
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• 2006

Ginseng is major medicinal plant in Korea. Because of its long cultivation period the yield losses of 5 years of ginseng is 50% due to various diseases. The objective of this study is to select potential biocontrol agents. As the result of research so far achieved to contribute to rational prevention of ginseag plant disease for the stable cultivation of ginseng, three bacterial strains, Streptomyces lauretii strain B8180, Bacillus subtilis strain 8856, and Burkholderia cepacia strain 7944 were isolated from oak leaf compost. The strains showed antagonistic activities against five ginseng pathogenic fungi (Cylindrocarpon destructans, Rhizoctonia solani, Phytophthora cactorum, Botrytis cinerea, Fusarium solani f. sp. panacis) and control effects on Phytophthora blight.

• Journal of Korean Society of Forest Science
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• v.94 no.5 s.162
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• pp.334-337
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• 2005

Pine wood nematode isolates from Haman, Gyoungsangnam-do were cryopreserved with three different cryoprotectants (glycerol, ethylene glycol and dimethylsulfoxide), Nematode Growth medium (NGM) and M 9 buffer solution, respectively, and then survival rate, reproduction ability, and pathogenicity of stored nematodes were compared. Survival rates of juvenile was excellent in 15% glycerol solution as $72{\pm}5.3%$. The survival ability of nematodes at juvenile stage was more efficient than that of nematodes at adult stage. Pre-incubation treatment at $4^{\circ}C$ before storing in liquid nitrogen didn't affect the survival ability of pine wood nematode. When the reproduction ability of nematodes was confirmed on Botrytis cinerea agar plates at $28^{\circ}C$ incubator, there was no difference between cryopreserved and non-cryopreserved. Pathogenic ability of cryopreserved nematodes was also evaluated and confirmed by artificially inoculating them on 2-year old red pine seedlings.

• The Plant Pathology Journal
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• v.27 no.2
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• pp.156-163
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• 2011

Antifungal activity of three Myxococcus spp., KYC 1126, 1136, and 2001, was tested in vitro against three phytopathogenic fungi (Botrytis cinerea, Colletotrichum acutatum, and Pyricularia grisea). Spore germination and mycelial growth of the three pathogenic fungi were completely inhibited by bioactive substances from a myxobacterium KYC 1126. In addition, the activity of KYC 1126 was fungicidal, but liquid culture filtrate of KYC 1126 did not affect protoplast reversion in C. acutatum. A bioassay of KYC 1126 filtrate against anthracnose in hot pepper was conducted in the greenhouse and field at 2009 and 2010. The incidence of anthracnose in control seedlings was 74%, but was reduced to 29% after KYC 1126 treatment. The control value with KYC 1126 was 60% while that with the fungicide dithianon was 42%. In the greenhouse, disease incidence with KYC 1126 was consistentely 10-35% lower than with fungicide as a positive control. The control value with KYC 1126 was 13.4% and 41.0%, whereas that with the fungicide was 52.3% and 63% in 2009 and 2010, respectively. Although anti-anthracnose activity of KYC 1126 was not maintained for long time in the field, the bacteriolytic myxobacterium KYC 1126 could be a prospective biocontrol agent.

• Research in Plant Disease
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• v.20 no.3
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• pp.182-188
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• 2014

Because bacterial isolates from only a few genera have been developed commercially as biopesticides, discovery and characterization of novel bacterial strains will be a key to market expansion. Our previous screen using plant bioassays identified 24 novel biocontrol isolates representing 12 different genera. In this study, we characterized the 3 isolates showing the best biocontrol activities. The isolates were Pantoea dispersa WCU35, Proteus myxofaciens WCU244, and Exiguobacterium acetylicum WCU292 based on 16S rRNA sequence analysis. The isolates showed differential production of extracellular enzymes, antimicrobial activity against various fungal or bacterial plant pathogens, and induced systemic resistance activity against tomato gray mold disease caused by Botrytis cinerea. E. acetylicum WCU292 lacked strong in vitro antimicrobial activity against plant pathogens, but induced systemic resistance against tomato gray mold disease. These results confirm that the trait of biological control is found in a wide variety of bacterial genera.

• Mycobiology
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• v.34 no.3
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• pp.138-142
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• 2006

Soil cyanobacteria isolated from the rice paddy fields of 10 different locations across Korea were evaluated by agar plate diffusion test for antifungal activity. Aqueous, petroleum ether, and methanol extracts from one hundred and forty two cyanobacterial strains belonging to the 14 genera were examined for antifungal properties against seven phytopathogenic fungi causing diseases in hot pepper (Capsicum annuum L). Of total cyanobacteria, nine cyanobacteria (6.34%) exhibited antifungal effects. The nine cyanobacteria selected with positive antifungal activities were two species of Oscillatoria, two of Anabaena, three of Nostoc, one of Nodularia, and one of Calothrix. Alternaria alternata and Botrytis cinerea were inhibited by nine and eight species of cyanobacteria, respectively. Rhizopus stolonifer was suppressed by only methanol extract of Nostoc commune FK-103. In particular, Nostoc commune FK-103 and Oscillatoria tenuis FK-109 showed strong antifungal activities against Phytophthora capsici. Their antifungal activity at the late exponential growth phase is related to the growth temperature and not associated with the growth parameters such as cell biomass and $chlorophyll-{\alpha}$ concentration. The high inhibition levels of antibiotics were 22.5 and 31.8 mm for N. commune FK-103 and O. tenuis FK-109, respectively. The optimal temperature for antibiotic productivity was $35^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.3 no.1
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• pp.12-18
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• 1993

Pseudomonas aeruginosa strain B5 with antagonistic activity against Phytophthora capsici and Magnaporthe grisea, was isolated from pepper-growing soil. From the culture of P. aeruginosa strain B5 grown on King's medium B, antibiotic substances were purified using XAD-2 column chromatography. XAD-2 eluates inhibited not only the mycelial growth of P. capsid and M. grisea, but also the development of Phytophthora blight on pepper plants. The crude antibiotic substances were further purified by using silica gel column chromatography, Sephadex LH-20 column chromatography, thin layer chromatography on silica gel plates, and high performance liquid chromatography. Silica gel column chromatogrphy gave good separation of the four antibiotic substances. The pure antibiotics P1, P2, and P3 finally purified by preparative HPLC inhibited the mycelial growth of P. capsici, at concentrations from 7 to 10 $\mu g/ml$. Only P1 and P2 had antifungal activity against M. grisea at 8 $\mu g/ml$. P1 and P3 were highly inhibitory to the mycelial growth of Botryosphaeria dothidea and Botrytis cinerea at relatively low concentrations. However, the three antibiotics had no antifungal activity against Rhizoctonia solani. The chemical structures of these antibiotics are being identified.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1272-1275
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• 2017

Two dimeric sesquiterpenes were separated from Chloranthus japonicus Sieb. and identified as shizukaols C and F. They exhibited potent antifungal activities ($MICs=4-16{\mu}g/ml$) in vitro against various plant pathogenic fungi (Pythium ultimum, Phytophthora infestans, Botrytis cinerea, Colletotrichum lagenarium, Alternaria kikuchiana, and Magnaporthe grisea). Shizukaol C showed 88% and 91% protective activities in the greenhouse against Puccinia recondita (wheat leaf rust) and Phytophthora infestans (tomato late blight), respectively, at $100{\mu}g/ml$; shizukaol F exhibited 93% antifungal activity against Puccinia recondita at the same concentration. Therefore, these compounds might serve as interesting candidates for effective antifungal agents.