• Korean Journal of Soil Science and Fertilizer
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• v.43 no.2
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• pp.180-187
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• 2010

The study was performed to investigate the property of rhizosphere microorganisms, and community structure during GMO, and Non-GMO rice cultivation. In the dilution plate technique, there were no significant differences in microbial populations of rhizosplane with genetically modified, and non-genetically modified rice cultivation, and rhizosphere were also the same results. Dominant bacterial genera were Afipia 12.5%, Spingomonas 10.0%, Ramlibacter 10.0%, Mycobacterium 7.5%, and Tetrasphaera 7.5% in rhizosphere soil of genetically modified rice plant, while Afipia 7.3%, Spingomonas 12.2%, Ramlibacter 7.3%, Mycobacterium 17.1%, Tetrasphaera 14.6% in non-genetically modified cultivated at Suwon test fields in 2006. Majorgenera isolated from root surface cultivated in Yesan fields were Arthrobacter 12.7% in rhizoplane of genetically modified plant, and Burkholderia 22.2% of non-genetically modified plant in 2007, Paucimonas 26.6% of genetically modified plant, Chryseobacterium 15.4% of non-genetically modified plant in 2008. Also the microbial communities in rhizosphere soils of genetically modified, and non-genetically modified plants were characterized using phospholipid fatty acid, and denaturing gradient gel electrophoresis. The phospholipid fatty acid profiles of soils in this condition showed different pattern, but did not show significant differences between soils cultivated with genetically or non-genetically modified rice plants.

• Korean Journal of Environmental Agriculture
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• v.32 no.2
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• pp.95-101
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• 2013

BACKGROUND: Rice (Oryza sativa) is the most important staple food of over half the world's population. This study was conducted to evaluate the possible impact of transgenic rice cultivation on the soil microbial community. METHODS AND RESULTS: Microorganisms were isolated from the rhizosphere of GM and non-GM rice cultivation soils. Microbial community was identified based on the culture-dependent and molecular biology methods. The total numbers of bacteria, fungi, and actinomycete in the rhizosphere soils cultivated with GM and non-GM rice were similar to each other, and there was no significant difference between GM and non-GM rice. Dominant bacterial phyla in the rhizosphere soils cultivated with GM and non-GM rice were Actinobacteria, Firmicutes, and Proteobacteria. The microbial communities in GM and non-GM rice cultivated soils were characterized using the denaturing gradient gel electrophoresis (DGGE). The DGGE profiles showed similar patterns, but didn't show significant difference to each other. DNAs were isolated from soils cultivating GM and non-GM rice and analyzed for persistence of inserted gene in the soil by using PCR. The PCR analysis revealed that there were no amplified protox gene in soil DNA. CONCLUSION(S): These data suggest that transgenic rice does not have a significant impact on soil microbial communities, although continued research may be necessary.

• The Plant Pathology Journal
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• v.32 no.3
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• pp.228-241
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• 2016

In our previous study, we reported that a novel endophytic bacterium Bacillus oryzicola YC7007 has suppressed bacterial diseases of rice via induced systemic resistance and antibiotic production. This endophytic strain, B. oryzicola YC7007 was used as a biological control agent against bakanae disease of rice caused by Fusarium fujikuroi, and its mechanism of interaction with the pathogen and the rice was further elucidated. Root drenching with B. oryzicola YC7007 suspension reduced the disease severity of bakanae significantly when compared with the untreated controls. The treatments of B. oryzicola YC7007 suspension ($2.0{\times}10^7cfu/ml$) to the rice rhizosphere reduced bakanae severity by 46-78% in pots and nursery box tests containing autoclaved and non-autoclaved soils. Moreover, in the detached rice leaves bioassay, the development of necrotic lesion and mycelial expansion of F. fujikuroi were inhibited significantly by spraying the culture filtrate of B. oryzicola YC7007. Drenching of ethyl acetate extracts of the culture filtrate to the rhizosphere of rice seedlings also reduced the bakanae disease severity in the plant culture dish tests. With the root drenching of B. oryzicola YC7007 suspension, the accumulation of hydrogen peroxide was observed at an early stage of rice seedlings, and a hormonal defense was elicited with and without pathogen inoculation. Our results showed that the strain B. oryzicola YC7007 had a good biocontrol activity against the bakanae disease of rice by direct inhibition, and was also capable of inducing systemic resistance against the pathogen via primed induction of the jasmonic acid pathway.

• Journal of Bio-Environment Control
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• v.10 no.2
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• pp.95-100
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• 2001

In countries that consumes rice as a main staple, rice hulls are natural resources composed of a large amount of organic compounds and high uniformity in size. Rice hulls are expanded to get rid of a defect in untreated rice hulls and to be used as a hydroponic substrate. Research on rice hulls is continuing for the agricultural application. This research was conducted to stabilize rhizosphere pH of the expanded rice hull substrates because of high pH caused by repeated use in ERH(expanded ride hull) substrates and without increasing the cost of developing new substrates. Sphagnum peatmoss (pH 3.0-4.0) wee mixed with the expanded rice hull substrate in the ratio of 10% (v/v), and this ratio kept the pH range of 6.0 to 6.5 in the root area of tomato plants during growth and at the time of harvest of tomato fruits. Also absorbtion of nutrients was highly increased. The yield increased from 1,051 to 1,266 kg per tomato plant which were harvested by two clusters.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.829-835
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• 2012

The cultivation of genetically modified (GM) crops has increased due to their economic and agronomic advantages. Before commercialization of GM crops, however, we must assess the potential risks of GM crops on human health and environment. The aim of this study was to investigate the possible impact of Bt rice on the soil microbial community. Microbial communities were isolated from the rhizosphere soil cultivated with Bt rice and Nakdong, parental cultivar and were subjected to be analyzed using both culture-dependent and molecular methods. The total counts of bacteria, fungi, and actinomycetes in the rhizosphere of transgenic and conventional rice were not significantly different. Denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rRNA genes revealed that the bacterial community structures during cultural periods were very similar each other. Analysis of dominant isolates in the rhizosphere cultivated with Bt and Nakdong rice showed that the dominant isolates from the soil of Bt rice and Nakdong belonged to the Proteobacteria, Cloroflexi, Actinobacteria, Firmicutes, and Acidobacteria. These results indicate that the Bt rice has no significant impact on the soil microbial communities during cultivation period. Further study remains to be investigated whether the residue of Bt rice effect on the soil environment.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.3
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• pp.355-365
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• 2015

Environment-friendly growth enhancers for rice are being promoted to reverse the negative impact of intensive chemical-based and conventional rice farming on yield sustainability and environmental problems. Several rhizosphere microorganisms and pyroligneous acids (PA) had demonstrated beneficial influence on growth, yield and grain quality of rice. Since most of the previous study had evaluated the effect of PGPR and PA on paddy rice singly, the effect of combined application of these on the growth and yield of paddy rice and on some soil chemical properties were determined. A four factorial pot experiment was conducted to evaluate the effect of PGPR, PA in combination with fertilizers and on different soil types. There were 54 treatment combinations including the control with three replications under complete randomized design. Plant growth parameters were evaluated using standard procedures during tillering and heading stages. Rice yield and some soil chemical properties were determined at harvest. Results showed that inoculation of Bacillus licheniformis and Fusarium fujikuroi enhanced plant growth by increasing the plant height which could be ascribe to its ability to promote IAA and GA production in plants. Inoculation of Rhizobium phaseoli enhanced chlorophyll content indicative to its ability to improve the N nutrition. However, these plant growth benefits during the vegetative stage were override by the fertilizer application effect especially during the maturity stage and grain yield. High fertilization rates on coarse-textured soil without nutrient loss resulted to high available nutrients and consequently high yield. Wood vinegar application however improved nutrient availability in soil which could be beneficial for improving soil quality. Further evaluation is necessary to fully assess the potential benefits that could be derived from inoculation of these organisms and wood vinegar application in different soil environment especially under different field conditions.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.1
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• pp.69-76
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• 1987

The aerobic heterotrophic bacteria in the histosphere associated with grasses (Gramineae, Caryphyllaceae, Crucifereae) and rice cultivars in saline and reclaimed saline paddy soils were varied with species and rice cultivars. The fraction of aerobic heterotrophic $N_2$-fixing bacteria to the total aerobic heterotrophic bacteria were averaged to eighteen percent in the histosphere of grasses and rice. Acetylene reducing activity of these bacteria were ranged from 1 to 24 n mole/tube/hr. Most of the bacteria strains were predominated of hydrogen utilizing bacteria. The majority of these bacteria were closed to Pseudomonas, Azospirillum, Klebsiella and Agrobacter.

• Journal of Microbiology and Biotechnology
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• v.24 no.8
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• pp.1015-1025
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• 2014

Microorganisms that live in the rhizosphere play a pivotal role in the functioning and maintenance of soil ecosystems. The study of rhizospheric cyanobacteria has been hampered by the difficulty to culture and maintain them in the laboratory. The present work investigated the production of the plant hormone indole-3-acetic acid (IAA) and the potential of biofilm formation on the rhizoplane of pea plants by two cyanobacterial strains, isolated from rice rhizosphere. The unicellular cyanobacteria Chroococcidiopsis sp. MMG-5 and Synechocystis sp. MMG-8 that were isolated from a rice rhizosphere, were investigated. Production of IAA by Chroococcidiopsis sp. MMG-5 and Synechocystis sp. MMG-8 was measured under experimental conditions (pH and light). The bioactivity of the cyanobacterial auxin was demonstrated through the alteration of the rooting pattern of Pisum sativum seedlings. The increase in the concentration of L-tryptophan and the time that this amino acid was present in the medium resulted in a significant enhancement of the synthesis of IAA (r > 0.900 at p = 0.01). There was also a significant correlation between the concentration of IAA in the supernatant of the cyanobacteria cultures and the root length and number of the pea seedlings. Observations made by confocal laser scanning microscopy revealed the presence of cyanobacteria on the surface of the roots and also provided evidence for the penetration of the cyanobacteria in the endorhizosphere. We show that the synthesis of IAA by Chroococcidiopsis sp. MMG-5 and Synechocystis sp. MMG-8 occurs under different environmental conditions and that the auxin is important for the development of the seedling roots and for establishing an intimate symbiosis between cyanobacteria and host plants.

• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.251-255
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• 1985

Nitrogen-fixing bacteria were isolated from the rice rhizosphere of various paddy fields in our country. The screening of 235 isolates for nitrogen-fixing ability resulted in the isolation of Enterobacter agglomerans NFB264 and three Klebsiella pneumoniae NFB 3, NFB 320. Plasmids of various molecular weight from 1.7 to more than 84 Mal. were detected by agarose gel electrophoresis in three out of four isolates. But, these plasmids had not any nitrogen-fixing genes. Hybridization experiments using Klebsiella pneumoniae M5al nitrogen-fixing genes, nif Q-K and nif DH, as probes revealed the presence of homologous sequences in the chromosomal DNA of all isolates. However the restriction patterns of nif genes of the isolates by various restriction endonucleases were different to those of Klebsiella pneumoniae M5al.

• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.919-927
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• 2007

Antagonistic fluorescent pseudomonads isolated from rhizospheric soil of rice were characterized by 16S rRNA amplicon and fatty acid methyl ester (FAME) analyses. Antagonistic isolates were grown in the fermentation media, and production of antibiotics was confirmed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). Production of fungal cell-wall-degrading enzymes such as protease, cellulase, pectinase, and chitinase was determined. Dendrogram based on the major and differentiating fatty acids resulted into 5 clusters, viz., cluster I (P. pseudoalcaligenes group), cluster II (P. plecoglossicida group), cluster III (P. fluorescens group), cluster IV (P. aeruginosa group), and cluster V (P. putida group). Characteristic presence of high relative proportions of cyclopropane (17:0 CYCLO w7c) was observed in antagonistic bacteria. Data revealed biodiversity among antagonistic fluorescent pseudomonads associated with the rice rhizosphere. Results presented in this study will help to identify the antagonistic isolates and to determine their mechanisms that mediate antagonism against fungal pathogens of rice.