• The Korean Journal of Mycology
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• v.25 no.1 s.80
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• pp.10-19
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• 1997

Fusarium wilt of radish (Raphanus sativus L.) is caused by the Fusarium oxysporum f. sp. raphani (FOR) which mainly attacks Raphanus spp. The pathogen is a soil-borne and forms chlamydospores in infected plant residues in soil. Infected pathogen colonizes the vascular tissue, leading to necrosis of the vascular tissue. Growth promoting beneficial organisms such as Pseudomonas fluorescens WCS374 (strain WCS374), P. putida RE10 (strain RE10) and Pseudomonas sp. EN415 (strain EN415) were used for microorganisms-mediated induction of systemic resistance in radish against Fusarium wilt. In this bioassy, the pathogens and bacteria were treated into soil separately or concurrently, and mixed the bacteria with the different level of combination. Significant suppression of the disease by bacterial treatments was generally observed in pot bioassy. The disease incidence of the control recorded 46.5% in the internal observation and 21.1% in the external observation, respectively. The disease incidence of P. putida RE10 recorded 12.2% in the internal observation and 7.8% in the external observation, respectively. However, the disease incidence of P. fluorescens WCS374 which was proved to be highly suppressive to Fusarium wilt indicated 45.6% in the internal observation and 27.8% in the external observation, respectively. The disease incidence of P. putida RE10 mixed with P. fluorescens WCS374 or Pseudomonas sp. EN415 was in the range of 10.0-22.1%. On the other hand, the disease incidence of P. putida RE10 mixed with Pseudomonas sp. EN415 was in the range of 7.8-20.2%. The colonization by FOR was observed in the range of $2.4-5.1{\times}10^3/g$ on the root surface and $0.7-1.3{\times}10^3/g$ in the soil, but the numbers were not statistically different. As compared with $3.8{\times}10^3/g$ root of the control, the colonization of infested ROR indicated $2.9{\times}10^3/g$ root in separate treatments of P. putida RE10, and less than $3.8{\times}10^3/g$ root of the control. Also, the colonization of FOR recorded $5.1{\times}10^3/g$ root in mixed treatments of 3 bacterial strains such as P. putida RE10, P. fluorescens WCS374 and Pseudomonas sp. EN415. The colonization of FOR in soil was less than that of FOR in root part. Based on soil or root part, the colonization of ROR didn't indicate a significant difference. The colonization of introduced 3 fluorescent pseudomonads was observed in the range of $2.3-4.0{\times}10^7/g$ in the root surface and $0.9-1.8{\times}10^7/g$ in soil, but the bacterial densities were significantly different. When growth promoting organisms were introduced into the soil, the population of Pseudomonas sp. in the root part treated with P. putida RE10 was similar in number to the control and recorded the low numerical value as compared with any other treatments. The population density of Pseudomonas sp. in the treatment of P. putida RE10 indicated significant differences in the root part, but didn't show significant differences in soil. The population densities of infested FOR and introduced bacteria on the root were high in contrast to those of soil. P. putida RE10 and Pseudomonas sp. EN415 used in this experiment appeared to induce the resistance of the host against Fusarium wilt.

• Weed & Turfgrass Science
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• v.2 no.1
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• pp.30-37
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• 2013

The objective of this research was to understand herbicidal activity of essential oils isolated from leaves of pine (Pinus densiflora), nut pine (Pinus koraiensis), larch (Larix kaempferi) and khingan fir (Abies nephrolepsis) in Korea. In a seed bioassay, essential oils of nut pine, larch and khingan fir inhibited the growth of rapeseed (Brassica napus) seedlings by 50% at 4,766, 1,865, $5,934{\mu}g\;ml^{-1}$, respectively, however, that of pine did not show any herbicidal effect. In a green house experiment, fall panicum, Southern crabgrass, sorghum, barnyardgrass, quackgrass, black nightshade, Indian jointvetch, velvet leaf, and Japanese morningglory were controlled in 24 hours by the foliar application of 10% essential oils from pine, nut pine, larch and khingan fir. The treated plant parts showed burndown effect, however, new shoots appeared 3 days after treatment. Results of GC-MS analysis showed that essential oils from pine, nut pine, larch and khingan fir contained 16, 25, 25, and 16 compounds, respectively, with hydrocarbons, alcohols, ketones, and esters. The major compounds of the essential oils were 3-carene, bornyl acetate, camphene, limonene, ${\alpha}$-pinene, ${\beta}$-pinene and ${\beta}$-phellandrene.

• The Korean Journal of Ecology
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• v.17 no.3
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• pp.251-260
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• 1994

Nitrification potential bioassay and terpenoid analyses were performed to determine the roles of terpenoid as an inhibitor of nitrification in the Douglas fir (Pseudotsuga menziesii) forests. The effect of terpenoids in the forest floor was also tested by adding $10{\mu}g/ml$ of four terpenoids(${\alpha}-pinene,{\beta}-pinene,{\gamma}-terpinene, and terpinolene) to mineral soils. The amount of terpenoids in the litter was higher than that in the soil and varied over time, but the amount of terpenoids in the soils was relatively constant. The correlation between the amount of terpenoids in the litter and ammonium oxidation was in inverse proportion to that in the mineral layers $(r^2=0.678)$. Inhibition of ammonium oxidation by terpenoids in the litter was always higher than in the mineral layer, but nitrite oxidation was different from the ammonium oxidation. The fact that there was greater nitrate production from ammonium in the mineral layer than in the forest floor layer seems to be due to the less amounts of terpenoids in the mineral layer. The result of the experiment in which four terpenoids were added to the mineral layer suggests that, after some lag time, the four terpenoids were effective in inhibiting ammonium oxidation. However, nitrite oxidation did not appear to be affected by the four terpenoids. Accordingly, all of our results suggested that terpenoids in Douglas fir forests apparently would act as a part of the inhibitors of nitrification.

• The Korean Journal of Pesticide Science
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• v.7 no.4
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• pp.248-257
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• 2003

The objective of this experiment was to search plant species with herbicidal activity in Korea. Two hundred native plants were collected and their methanol extracts were obtained. Herbicidal activity of methanol extracts were determined by seed bioassay using canola (Brassica napus L.) seedlings. Six plants such as Staphylea bumalda, Wistaria floribunda, Allium victorialis, Rumex crispus, Chionanthus retusa, and Ulmus parvifolia were highly herbicidal: their $GR_{50}$ values were < $1,000{\mu}g\;g^{-1}$. In addition, seventeen plants such as Galium spurium, Zelkova serrata, Campsis grandiflora, Eucommia ulmoides, Sorbus commixta, Deutzia glabrata, Cercis chinensis, Alnus hirsuta, Zanthoxylum schinifolium, Quercus acutissima, Robinia pseudoacacia, Gleditsia japonica, Kerria japonica, Ligustrum obtusifolium, Thuja orientalis, Chamaecyparis obtusa, and Pulsatilla koreana showed herbicidal activity: their $GR_{50}$ values were between 1,000 and $2,000{\mu}g\;g^{-1}$. However, 177 plants showed no herbicidal activity. Plants with herbicidal activity found in this study could be used for weed management and herbicidal compounds in such herbicidal plants could be used as lead compounds in the development of new herbicides.

• Food Science and Preservation
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• v.16 no.3
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• pp.435-441
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• 2009

Activity-guided isolation from the ethylacetate (EtOAc)-soluble portion of a methanolic extract of the seeds of Eriobotrya japonica, using several bioassays, led to the isolation and identification of six phenolic compounds of previously known structure: benzaldehyde (1), chlorogenic acid (2), caffeic acid (3), benzoic acid (4), ferulic acid (5), and amygdalin (6). Of these, benzaldehyde (1) exhibited tyrosinase inhibitory activity in a bioassay. In addition, chlorogenic acid (2) and caffeic acid (3) were found to have strong antioxidative effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and superoxide dismutase (SOD)-like activity.

• Korean Journal of Food Science and Technology
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• v.38 no.5
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• pp.684-690
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• 2006

Eriobotrya japonica has been used as a folk medicine for treatment of skin diseases, inflammation, coughing, phlegm, and ulcers in Korea and other Asian countries. In a search for possible bioactive agents from natural sources, we found that the methanolic extracts from various parts of E. japonica showed moderate antioxidative and antimicrobial activities in several in vitro bioassay systems. Additionally, the respective parts of E. japonica were irradiated at 20 kGy to investigate the effects of irradiation. Gamma irradiation of E. japonica extracts removed the deep greenish color without affecting its natural biological activities such as its antioxidative and antimicrobial properties. Based on these findings, the methanolic extracts of this plant source may be not affected by gamma irradiation as its bioactive constituents may be insensitive to this irradiation. Moreover, the methanolic extract of E. japonica may serve as a good natural resource for beneficial functions in food and other related industries.

• Korean journal of applied entomology
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• v.45 no.3 s.144
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• pp.357-362
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• 2006

Bacillus thuringiensis strains were isolated from the domestic soil and a strain was selected that had a new host range and high toxicity against agriculture insect pest. The 142 samples of soil were sampled from the mountains, paddy fields and patches, in Daejon, Chungnam, Chungbuk and Jeonbuk and used for the investigation. Sixteen B. t strains were isolated from 12 samples among collected samples. There were 11 strains that showed toxical activity on Plutella xylostella (Lepidoptera: Yponomeutidae), 7 steins on Spodoptera litura (Lepidoptera: Noctuidae), 5 strains on Arete coerulea (Lepidoptera: Noctuidae), 5 strains on Culex pipiens pallens (Diptera: Culicidae) among the 16 isolated B. t strains. But there were not any strains that showed activity against Hyphanria cunea (Lepidoptera: Arctiidae) and Sitophilus oryzae (Coleoptera: Rhynchophoridae). And also some of B. thuringiensis strains showed insecticidal activity with 2, 3 or 4 kinds of insects. But there were also 3 strains that did not show any activities to the 6 insects which were used in the experiment. When examined with a phase-contrast microscope, the insecticidal crystal protein produced from 16 selected strains had 13 bipyramidal and 3 spherical shapes. The insecticidal bioactivity of the S. litura showed 100% mortality when there were $1.3{\times}10^{7}\;(cfu/ml)$ of CAB109 isolates.

• Research in Plant Disease
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• v.21 no.3
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• pp.208-214
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• 2015

To develop an effective biopesticide to control pepper anthracnose disease, an isolate which showed strong inhibitory effect on the mycelial growth and conidial germination of Colletotrichum acutatum was selected among the antagonistic bacterial isolates collected from pepper grown soil. The bacterial isolate was identified as Bacillus sp. KBC1004 using 16S rRNA sequence analysis. The liquid culture of KBC1004 was freeze-dried and formulated as a wettable powder(WP). The wettable powder form of KBC1004 required at least 24 hours to activate and to inhibit the conidial germination of C. acutatum. In vitro bioassay using the detached green pepper fruits, biocontrol activity of the WP was not recognizable in simultaneous inoculation, but significant disease suppression was observed pre-treatment (24 hr) of the WP before pathogen inoculation. In field experiment, 4 times foliar applications of the 1/500 diluted wettable powder from the end of June showed great control efficacy similar to that of the chemical fungicide application. These results suggest that the formulated WP product could be an alternative mean to control of pepper anthracnose disease in environmentally friendly farming practices.

• Food Science and Preservation
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• v.15 no.3
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• pp.456-460
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• 2008

Santalum album has been used as a folk medicine for treatment of skin diseases, inflammation, gonorrhea, gleet, and cystitis in India and other Asian countries. In a search for possible bioactive agents from natural sources, we found that the various solvent extracts of S. album showed significant antioxidative effect in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity test and moderate other biological functions submitted to the several bioassay systems for whitening and cytotoxicity evaluations. Among the tested extracts displayed DPPH radical scavenging activity, and the 70% acetone extract showed the most potent activity with an $IC_{50}$ value of $18.6\;{\mu}g/ml$, more potent than a positive control, L-ascorbic acid ($IC_{50}$, $28.7\;{\mu}g/mL$). Also, anti-lipid peroxidation, tyrosinase inhibitory, and cytotoxic effects were determined in each experiment. Total phenolic content of 70% acetone extract was found to be 117.1 mg equivalent of gallic acid per g of extract. Previous phytochemical investigation reveals the presence of phenolic compounds. The results indicate that S. album possess potential antioxidant activity and phenolic constituents are responsible for this capacity.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.139-149
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• 2003

This study was conducted to determine limiting nutrients and the physiological characteristics of phytoplankton in response of nutrients in Lake Paldang from March 2002 to October 2002. A field research was conducted along with laboratory batch culture experiment to find the limiting nutrients and the growth kinetics. According the results of Chl. a TP relationship, TN/TP ratio, and nutrient addition bioassay, phosphorus appeared to be a major limiting nutrient in Lake Paldang and thus the lake productivity was greatly influenced by it. P limitation for the phytoplankton of Lake Paldang varied with season, and the possibility of limitation by nitrogen and silica also occurred. The degree of P limitation was greatest during spring when the concentration of dissolved phosphorus is relatively much lower than summer and autumn. The maximum growth rate (${\mu}_{max}$) and half saturation concentration ($K_u$) of Lake Paldang phytoplankton ranged from 0.8${\sim}$1.1$day^1$ and from 0.1${\sim}$O.8${\mu}M$, respectively. $K_u$ was highest during May ($0.8{\mu}M$) and the lowest during September ($0.1{\mu}M$). Such result may be induced by the phytoplankton cell quota that showed the lowest concentration ($0.13{\mu}gP/{\mu}gChl.$ a) during May. The growth kinetics showed that phytoplankton growth in Lake Paldang was faster during summer and autumn than spring, suggesting that the Potential of algal bloom is high after the summer monsoon season.