• Asian-Australasian Journal of Animal Sciences
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• v.11 no.3
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• pp.277-284
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• 1998

This experiment was carried out to study the effects of lactic acid bacteria (LAB) inoculation and addition of cell wall degrading enzymes on the fermentation characteristics and chemical compositions of Italian ryegrass silage. An inoculant LAB with or without a cell wall degrading enzyme of Acremoniumcellulase (A), or Meicellulase (M) or a mixture of both (AM), was applied to 1 kg of fresh Italian ryegrass sample. The treatments were control untreated, LAB-treated (application rate $10^5$ cfu/g fresh sample), LAB+A 0.005%, LAB + A 0.01%, LAB+A 0.02%, LAB + M 0.005%, LAB + M 0.01%, LAB + M 0.02%, LAB+AM 0.005%, LAB + AM 0.01% and LAB+AM 0.02%. The sample was ensiled into 2-L vinyl bottle silo, with 9 silages of each treatment were made (a total of 99 silages). Three silages of each treatment were incubated at 20, 30 and $40{^{\circ}C}$ for an approximately 2-months storage period. All silages were well preserved as evidenced by their low pH values (3.79-4.20) and high lactic acid concentrations (7.71-11.34% DM). The fermentation quality and chemical composition of the control untreated and the LAB-treated silages were similar, except that for volatile basic nitrogen (VBN) content was lower (p < 0.05) in the LAB-treated silages. LAB + cellulase treatments improved the fermentation quality of silages by decreasing (p < 0.01) pH values and increasing (p<0.01) lactic acid concentrations, in all of cellulase types and incubation temperatures. Increasing amount of cellulase addition resulted in further decrease (p < 0.01) of pH value and increases (p < 0.01) of lactic acid and residual water soluble carbohydrate (WSC) concentrations. LAB + cellulase treatments reduced (p<0.01) NDF, ADF, hemicellulose and cellulose contents of silages compared with both the control untreated and LAB-treated silages. LAB + cellulase treatments did not affect the silage digestibility due to fact of in vitro dry matter digestibility (IVDMD) was similar in all silages. The silages treated with cellulase A resulted in a better fermentation quality and a higher rate of cell wall reduction losses than those of the silages treated with cellulases M and AM. Incubation temperature of $30{^{\circ}C}$ seemed to be more suitable for the fermentation of Italian ryegrass silages than those of 20 and $40{^{\circ}C}$.

• Research in Plant Disease
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• v.19 no.3
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• pp.188-195
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• 2013

This study was carried out for the downy mildew resistant test between 2010 and 2012. A set of 22 accessions belonging to 2 wild species and 20 varieties of the genus Cucumis, originating mainly from the Asian Vegetable Research and Development Center (AVRDC) Gene Centre, was evaluated for resistance to Pseudoperonospora cubensis, causal agent of cucumber downy mildew. The youngest fully expanded true leaves were found suitable for in vitro screening. Both leaf discs and full leaves could be kept fresh longer when applying 0.2 ${\mu}g/ml$ of gibberellin acid (GA). The incubation temperature of $20^{\circ}C$ was found to be the most suitable temperature for symptom development comparing with 15 and $25^{\circ}C$. Symptom development was faster when contact diseased leaf discs (2 weeks after inoculation) on to fresh leaf samples comparing with using conidia suspension ($10^5$ spores/ml). The numbers of spots in 'C-19' were lower than other varieties. 'C-19' variety was also showed the highest level of downy mildew resistant at $20^{\circ}C$ chamber in 6 days after inoculating with pathogen and displayed 0.90 (under 10%) of the infected rate. However, other varieties displayed susceptible in the pathogen sprayed plots. 'C-19' was the most resistant variety and no lesion was observed. Based on all data, 'C-19' can be a useful variety for the prevention of downy mildew.

• The Korean Journal of Mycology
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• v.41 no.4
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• pp.248-254
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• 2013

A Gram-negative bacterium was isolated from mushroom media that markedly reduces the level of extracellular toxins (i.e., tolaasins) produced by Pseudomonas tolaasii, the most destructive pathogen of cultivated mushrooms. The HC1 strain was selected as detoxifying tolaasin by bioassay on potato and it was identified Pseudomonas sp. by the cultural, morphological and physiological characteristics, and analysis of the 16S rRNA. The isolated bacterium is saprophytic but not parasitic nor pathogenic to cultivation mushroom. The isolated bacterium for P. tolaasii cell, was sufficient for detoxification in vitro. Inoculation of the isolated bacterium prevents the development of bacterial disease in Pleurotus ostreatus, Flammunia velutipes and Agaricus bisporus. Control efficacy of brown blotch of strain HC1 treatment was 69, 68 and 55% on Agaricus bisporus, Flammulina velutipes and Pleurotus ostreatus, respectively. The suppressive bacterium may be useful in future for the development of biocontrol system and the construction of genetically modified edible fungi resistant to the disease caused by P. tolaasii.

• Journal of Microbiology and Biotechnology
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• v.27 no.10
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• pp.1763-1772
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• 2017

This study aimed to isolate and characterize antibacterial metabolites from Pharbitis nil seeds and investigate their antibacterial activity against various plant pathogenic bacteria. The methanol extract of P. nil seeds showed the strongest activity against Xanthomonas arboricola pv. pruni (Xap) with a minimum inhibition concentration (MIC) value of $250{\mu}g/ml$. Among the three solvent layers obtained from the methanol extract of P. nil seeds, only the butanol layer displayed the activity with an MIC value of $125{\mu}g/ml$ against Xap. An antibacterial fraction was obtained from P. nil seeds by repeated column chromatography and identified as pharbitin, a crude resin glycoside, by instrumental analysis. The antibacterial activity of pharbitin was tested in vitro against 14 phytopathogenic bacteria, and it was found to inhibit Ralstonia solanacearum and four Xanthomonas species. The minimum inhibitory concentration values against the five bacteria were $125-500{\mu}g/ml$ for the n-butanol layer and $31.25-125{\mu}g/ml$ for pharbitin. In a detached peach leaf assay, it effectively suppressed the development of bacterial leaf spot, with a control value of 87.5% at $500{\mu}g/ml$. In addition, pharbitin strongly reduced the development of bacterial wilt on tomato seedlings by 97.4% at $250{\mu}g/ml$, 7 days after inoculation. These findings suggest that the crude extract of P. nil seeds can be used as an alternative biopesticide for the control of plant diseases caused by R. solanacearum and Xanthomonas spp. This is the first report on the antibacterial activity of pharbitin against phytopathogenic bacteria.

• Research in Plant Disease
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• v.17 no.3
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• pp.302-310
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• 2011

Elsinoe fawcettii is one of major pathogenic fungi which cause citrus scab diseases, resulting in fruit blemishes that reduce the economic value of fruit. By increasing interest to safe products of crops, the alternative methods of disease control is highly required. We investigated whether the 215 bacterial strains isolated from Jeju Island possess antifungal effect or suppression effect on the symptom development by Elsinoe fawcettii on citrus. Among them, three bacterial strains THJ 609-3, MRL408-3, and TRH423-3 that exhibited antifungal capacity against Elsinoe fawcettii were selected. To illustrate the disease suppression mechanism, pre-inoculation with the selected bacterial strains was carried out whether could suppress the citrus crab on the leaves. The observation with a fluorescence microscope revealed that the selected bacteria could decrease the number of fungal spores. The ratio of germ tube formation was also decreased by the selected bacterial strains at one day after fungus challenge. The strain THJ 609-3 was identified as Pseudomonas putida as a result of analyzing the internal transcript spaces of the rhizobacterial rDNA. The strains MRL 408-3 and TRH 423-3 were identified as Burkholderia gladioli. Our results may be valuable when the selected rhizobacterial strains used as the environment-friendly microbe for biological control on citrus scab caused by Elsinoe fawcettii.

• Korean Journal of Organic Agriculture
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• v.23 no.3
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• pp.567-582
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• 2015

Botrytis cinerea infects stems, leaves and fruits of greenhouse tomato and can cause serious economic losses. This study was conducted to develop organic farming control method against tomato gray mold. Twenty two organic farming materials including mineral and plant extracts were screened for the suppressive activity against Botrytis cinerea, in vitro and in vivo. Among the organic farming materials, sulfur, copper, Chinese twinleaf extract and rhubarb extract decreased by 51.7-90% of the spore germination of Botrytis cinerea. Also, gray mold incidence was reduced more than 90% on tomato stems by treating sulfur, seaweed extracts, rhubarb root extracts and Chinese twinleaf extract. After the selected four organic farming materials were applied on tomato cultivated in greenhouse, their control effects against the tomato gray mold were tested. When the water soluble sulfur was foliar-sprayed on the tomato leaves infected by artificial inoculation with spore suspension of Botrytis cinerea, it showed 87.9% of control value. Also, control activity of the water soluble sulfur was paralleled with chemical fungicide, diethofencarb+carbendazim. The above mentioned results indicate the sulfur formulation can be used as chemical fungicide alternatives for controlling tomato gray mold in the greenhouse.

• The Korean Journal of Mycology
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• v.42 no.4
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• pp.312-321
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• 2014

Tricholoma bakamatsutake is one of the edible ectomycorrhizal mushrooms as an allied species of Tricholoma matsutake. This is the first report on physical characteristics of T. bakamatsutake strains collected from Quercus mongolica forests in Korea. The pure cultures of these strains were isolated from the tissues of fruit bodies and the culture characteristics were investigated under different conditions (media, temperatures, nitrogen sources). Most strains showed the highest mycelial growth on potato dextrose agar (PDA) at 20 or $25^{\circ}C$. Two strains of T. bakamatsutake preferred the ammonium-form rather than the nitrate-form as an inorganic nitrogen source. T. bakamatsutake showed significantly slower mycelial growth when compared with T. matsutake from a Korean forest, although the optimum culture conditions for the two allied species were similar. We also tested the ability to form mycorrhizae as well as cellulase activity of T. bakamatsutake. All strains showed cellulase activity on a carboxymethylcellulose (CMC) agar plate. The mycorrhizae on axenic Pinus densiflora seedlings were formed by two strains of T. bakamatsutake after 3 or 8 months of inoculation. P. densiflora seedlings inoculated with T. bakamatsutake had a much higher biomass than un-inoculated seedlings.

• Korean Journal Plant Pathology
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• v.1 no.1
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• pp.3-11
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• 1985

Three mild mutant strains of tobacco mosaic virus (TMV) were isolated from Nicotiana tabacum var. Samsun incubated at $38^{\circ}C$ for 10 days after inoculation with a wild type of TMV-OM strain. They were designated into Tg 5272, Tw 227 and Tw 333. All mild strains could be distinguished from TMV-OM by their reactions on different indicator plants. The mild strains induced the mild mottling without distinct symptoms, whereas the wild strain produced severe mosaic, rugose and stunting on tobacco and red pepper plants. Tw 227 and Tw 333 produced smaller necrotic spots than those of Tg 5272 and TMV-OM on N. glutinosa and Datura stramonium. The former two strains also produced ring spots and mosaic on Gomphrena globosa compared with necrotic spots by the latter strains. Three mild strains were serologically identical to TMV-OM. Their physical properties were thermal inactivation point $80-85^{\circ}C$, dilution end point between $10^{-4}\;and\;10^{-6}$, and longevity in vitro 7days or longer. Ultraviolet absorption spectra of purified preparations of the mild strains and TMV-OM were identical, with a minimum at 247nm, a maximum at 260nm, and a slight shoulder at 290nm. Electrophoresis of the strains in polyacrylamide-agarose gel showed that all the strains formed one major band and two minor bands, except for one minor band of Tw 333. However, when sodium dodecyl sulfate was added to the purified viruses before electrophoresis, each strain formed only one major band.

• Korean Journal of Soil Science and Fertilizer
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• v.23 no.2
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• pp.152-159
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• 1990

Four active strains, producing siderophore and antagonizing to soil plant disease fungi, were isolated and identified from the wheat rhizosphere to reduce the injurious effects of continuous cropping and study on the biological control. The obtained results were summerized as follow. 1. Four strains of fluorescent Pseudomonas were isolated from the wheat rhizosphere and identified as Pseudomonas fluorescens Biotype A(Ps-1,2,5) and Biotype B(Ps-3) That strains inhibitied growth of R. solani, F.oxysperum and F. solani in vitro 2. Optical density of pigment was maximum at 410nm. 3. Siderophore production by identified strains was decreased with addition of $Fe^{+3}$, although not decreased with addition of $Fe^{+2}$ 4. Pigment of Ps-1, 2 and 3 strain inhibitied growth of R. slani, F. oxysperum and F. solani but pigment of Ps-5 strain did not inhibitie growth of R. solani 5. Effect of inoculation was in order of Ps-2, 1, 5 and 3 strain through the dark culture method, and effect of Ps-1 and Ps-2 was greater than that of treatment of captan 50ppm.

• Journal of fish pathology
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• v.29 no.1
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• pp.35-43
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• 2016

In comparison to the numbers of such studies of fish, few studies have been carried out on the immunity, physiology and ecology of abalone, while studies on abalone disease are also extremely rare. Moreover, mass mortality of cultured abalone due to pathogenic bacteria has not been reported in the southern coast of Korea. However, Vibrio-like bacteria have been isolated from dead abalone, which indicates that a review is required in order to determine the cause of abalone mortality. Use of an antimicrobial agent to minimize the damage caused by disease in abalone farms is common, but the therapeutic effects are insignificant. Demand for probiotics has increased, but research on the development of probiotics for use in abalone culture is very rare. Therefore, the present study isolated KC16-2 from fermented kimchi soup and investigated the characteristics of the isolate as a candidate probiotic bacterium in abalone. KC16-2 was identified as Bacillus amyloliquefaciens (B. amyloliquefaciens KC16-2) based on its biochemical properties and 16S rRNA gene sequence. B. amyloliquefaciens KC16-2 showed inhibitory effects against the growth of various vibrios in vitro, and kept the numbers constant until four days after inoculation in marine water at a temperature of $15{\sim}25^{\circ}C$, indicating the possible use of KC16-2 as a probiotic, except in the winter. The growth of KC16-2 was inhibited by bile salt, but the numbers increased over time suggesting the bacteria were still alive in the abalone's digestive tract. Abalone fed with a diet including KC16-2 for 12 weeks showed good growth, but showed no significant differences from the control group. However, the mortality of the abalone supplied the probiotic diet was reduced to half that of the control group in a challenge test with Vibrio tubiashii. Therefore, we suggest that B. amyloliquefaciens KC16-2 could be used as a probiotic bacterium for control of the mortality of abalone caused by opportunistic pathogenic vibrios.