• Mycobiology
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• v.34 no.4
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• pp.191-195
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• 2006

This study was conducted to investigate the different effects of ectomycorrhizal fungal (ECMF) species on the growth of seedlings of Pinus densiflora, and the effects of ECMF diversity on plant productivity. A total of five species of ECMF were isolated from root tips of pine seedlings collected from Mt. Songni and used as inocula. Pots containing pine seedlings were inoculated with either a single ECMF species or a mixture of five ECMF species. All of the seedlings formed ECM on their roots except for the control plants. The pine seedlings' growth responses varied by the different ECMF species. Also, pine seedlings inoculated with a mixture of five ECMF species showed the highest growth response. The results of the study suggest that the colonization of diverse species of ECMF will increase plant productivity, and the selection of suitable ECMF species could be an important factor for plant growth.

• The Korean Journal of Mycology
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• v.37 no.2
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• pp.134-138
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• 2009

This study was conducted to investigate colonization of ectomycorrhizal fungi(ECM) in roots of Abies koreana which is an endemic and endangered species in Korea. Roots of A. koreana were collected at Mt. Halla. ECM root tips were classified using morphotyping and identified using sequences of internal transcribed spacer (ITS) region of the fungal rDNA. Total 8 species of ECM fungi were identified from roots of 11 seedlings of A. koreana : Cenococum geophilum, Russula brevipes, 2 species of Russula, 2 species of Thelephora, Cortinarius camphorates and 2 species of Helotiales. These species were known to be typical ectomycorrhizal fungi found in coniferous mature forests.

• The Plant Pathology Journal
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• v.31 no.4
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• pp.334-342
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• 2015

Two fumonisin-nonproducing strains of Fusarium verticillioides and their fumonisin producing progenitors were tested for aggressiveness toward maize, sorghum, rice, and beetroot seedlings grown under greenhouse conditions. None of the plants showed obvious disease symptoms after root dip inoculation. Fungal biomass was determined by species-specific real-time PCR. No significant (P = 0.05) differences in systemic colonization were detected between the wild type strains and mutants not producing fumonisins. F. verticillioides was not detected in any of the non-inoculated control plants. The fungus grew from roots to the first two internodes/leaves of maize, rice and beet regardless of fumonisin production. The systemic growth of F. verticillioides in sorghum was limited. The results showed that fumonisin production was not required for the infection of roots of maize, rice and beet by F. verticillioides.

• Journal of Korean Society of Forest Science
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• v.99 no.2
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• pp.172-178
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• 2010

The status of ectomycorrhizal (ECM) fungal colonization in Pinus thunbergii seedlings was investigated 2 years after planting in an eastern coastal area of Korea. We established three $10{\times}10$ m plots at a P. thunbergii plantation in Gangneung and sampled lateral roots from 10 seedlings in each plot. ECMs were classified into morphological groups and the number of root tips of each morphotype was counted. In total, 8 ECM morphotypes were observed and fungal species that form each morphotype were identified by sequencing of the internal transcribed spacer (ITS) region of the nuclear rDNA. Suillus granulatus was the most abundant species (44.1-65.7% of relative abundance) in all plots, followed by Tomentella ellisii (14.0-37.8%) and unidentified fungus belonged to Atheliaceae (10.6-20.1%). These 3 fungal species accounted for almost all of the ECM abundance in each plot (94.9-99.8%). The remaining 5 fungal species were uncommon and rare. There was no clear difference in ECM fungal communities among plots. Community structure of ECM fungi in the young P. thunbergii plantation was simple and composed of fungal species that were also observed in mature coastal pine forests.

• Korean Journal of Plant Resources
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• v.23 no.3
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• pp.248-255
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• 2010

We previously demonstrated that root colonization of the rhizobacterium, Pseudomonas chlororaphis O6, induced expression of a galactinol synthase gene (CsGolS1), and resulting galactinol conferred induced systemic resistance (ISR) against fungal and bacterial pathogens in cucumber leaves. To examine the role of galactinol on ISR, drought or high salt stress, we obtained T-DNA insertion Arabidopsis mutants at the AtGolS1 gene, an ortholog of the CsGolS1 gene. The T-DNA insertion mutant compromised resistance induced by the O6 colonization against Erwinia carotovora. Pharmaceutical application of 0.5 - 5 mM galactinol on roots was sufficient to elicit ISR in wild-type Arabidopsis against infection with E. carotovora. The involvement of jasmonic acid (JA) signaling on the ISR was validated to detect increased expression of the indicator gene PDF1.2. The T-DNA insertion mutant also compromised tolerance by increasing galactinol content in the O6-colonized plant against drought or high salt stresses. Taken together, our results indicate that primed expression of the galactinol synthase gene AtGolS1in the O6-colonized plants can play a critical role in the ISR against infection with E. carotovora, and in the tolerance to drought or high salt stresses.

• The Plant Pathology Journal
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• v.21 no.1
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• pp.68-72
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• 2005

The production of antibiotic substances by Serratia plymuthica A21-4 was greatly enhanced by modifying components of a growth medium. When the minimal medium containing $K_2HPO_4$ 0.7%, $KH_2PO_4$ 0.2%, $(NH_4)_2SO_4$ 0.1%, $MgSO_4$ 0.01% was used as basal medium, the best carbon source for antibiotic production was glycerol and the most favorable nitrogen source was ammonium sulfate. The modified medium for antibiotic production also increased colonization ability of A21-4 on pepper root and in the rhizosphere soil. When the cells of A21-4 were suspended in modified medium, the population density of A21-4 on pepper root was 10-100 times higher than that suspended in 0.1 M $MgSO_4$. The population density of A21-4 on root did not decrease under $10^6$ cfu/groot up to 21 days after treatment although the inoculum of A21-4 was reduced to $10^7$ cell/ml. Similar tendency was also observed in the rhizosphere soil. Consequently, Phytophthora blight of pepper was successfully controlled by A21-4 with $10^7$ cell/ml suspended in the modified buffer solution instead of $10^9$ cfu/ml suspended in 0.1 M $MgSO_4$.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.3
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• pp.135-149
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• 2017

In order to obtain promising rice growth-promoting microbial strains that can be used as substitutes for chemical fertilizers, 172 bacterial strains were isolated from rice roots grown in Korean and Russian soils. Out of them, the strains KR076, KR083, KR181 and RRj228 showed plant growth-promoting activities on maize seedlings. Bacillus megaterium KR076 and Bacillus sp. KR083 showed both nitrogen-fixing and plant growth-promoting activities, while Rhizobium sp. KR181 and Pseudomonas sp. RRj228 appeared to support only plant growth-promotion, but not $N_2$ fixation. Especially, RRj228 showed high growth promoting activity at low concentrations. Inoculation studies with KR083 and RRj228 revealed a high affinity to the Japonica rice variety such as Junambyeo than the Korean Tongil type variety such as Arumbyeo. Both KR083 and RRj228 strains showed rhizoplane and/or endophytic colonization in Japonica and Tongil types rice when soaked with the bacterial suspension of $1.1{\times}10^5cfu\;ml^{-1}$ for six and twelve hours. However, the total bacterial cell numbers were higher in the roots of Japonica variety than in the Tongil type. In inoculation trials with Daesanbyeo rice variety, the seedlings inoculated with KR181 and RRj228 at the rate of $2.0{\times}10^6cfu\;ml^{-1}$ showed yield increment of 35% and 33% (p < 0.01), respectively, so that they contributed to the replacement of chemical fertilizer at half doses of N, $P_2O_5$, and $K_2O$ in pots. In Junambyeo rice seedlings, the strain RRj228, when inoculated with a cell suspension of $1.8{\times}10^6cfu\;ml^{-1}$, promoted 3.4% higher yield at 70% dose than at a full dose level of N $110kg\;ha^{-1}$ in field. These results suggest that the rhizobacteria KR181 and RRj228 are prospective strains for enhancing rice performance.

• Korean Journal of Soil Science and Fertilizer
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• v.31 no.3
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• pp.291-300
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• 1998

A study was carried out to evaluate the effect of different salts and their Quantities on the fluctuation and rhizosphere colonization of soil microorganisms. The results obtained are as follows. The electrical conductivities(ECs) of $KNO_3$, $K_2HPO_4$, KCl and $K_2SO_4$ showed negative correlations to the number of gram positive bacteria and gram negative bacteria : the number of bacteria was significantly decreased in the KCl or $KNO_3$ treated group compared to the $K_2HPO_4$ or $K_2SO_4$ treated group. The highest microorganism density of gram negative bacteria, gram positive bacteria and Fusarium sp. in balanced salts-treated soil was observed at $0.5dS\;m^{-1}$, $2.1dS\;m^{-1}$ and $8.0dS\;m^{-1}$ of EC, respectively. The ratio of bacteria to fungi ratio in balanced salts-treated soil substantially decreased as the EC of soil increased. Ten and thirty days after soil treatment with balanced salts, the ratio of bacteria to fungi decreased to 757-1571 and 89-215, respectively. Root colonization density of Fluorescent Pseudomonas in cucumber and tomato significantly decreased as the EC of soil increased, whereas that of Fusarium sp. increased.

• Weed & Turfgrass Science
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• v.5 no.1
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• pp.29-34
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• 2016

Large patch disease in Zoysia japonica Steud. is the most destructive disease in turfgrass. For large patch management, it has been dependent on chemical controls but pesticides are harmful to soil, water and biodiversity. In this study, we evaluated 4 Streptomyces spp. strains (S2, S5, S8 and S12) which were selected in previous studies using metagenome approaches. Root colonization of the strains, large patch suppressing effect and the pathogen density change in actual golf course were investigated to evaluate biological control potential of the strains. All strains exhibited reliable root colonization ability that strains populations were higher than $6log\;cfu\;g^{-1}$ in turfgrass rhizosphere. The pathogen density, with S8 treatment, was detected average of 0.7 after a week and average of 1.2 after 4 weeks. Disease control and suppressive the pathogen population by S8 strain showed higher efficiency than other strains. S8 was applied in an actual golf course for the large patch control and pathogen density. The pathogen density in S8 treatment plot was detected below 1.6 per toothpick and lower compared with untreated plot. The results indicated that pathogen density was suppressed by S8 and the stain has great potential as a biological control agent for the large patch.

• 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.