• The Plant Pathology Journal
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• v.27 no.1
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• pp.78-84
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• 2011

Antagonistic rhizobacteria, more specifically fluorescent pseudomonads and certain species of Bacillus, are known as biocontrol agents of fungal root diseases of agronomic crops. In this study, 144 bacteria were isolated from cucumber rhizosphere and screened as potential biological control agents against Phytophthora drechsleri, the causal agent of cucumber root rot, in vitro condition. Non-volatile compounds of 23 isolates showed noticeable inhibition zone (> 30%) against P. drechsleri, whereas volatile compounds of 7 isolates could prevent more than 30% of the mycelial growth of the fungus. All promising isolates, except of Pseudomonas flourescens V69, promoted significantly plant growth under in vitro condition. P. flourescens CV69 and V11 exhibited the highest colonization on the root. Results of the greenhouse studies showed that a reduction in disease incidence by use of some strains, and particularly use of strains CV6 and V11 as a soil treatment, exhibited a reduction in disease incidence so that suppressed disease by 85.71 and 69.39% respectively. Pseudomonas flourescens CV6 significantly suppressed disease in comparison to Ridomil fungicide. The use of mixture bacterial strains in the soil inoculated by the fungus resulting in falling down the most of the plants which didn't show significant difference with infected control soils without bacteria.

• The Korean Journal of Mycology
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• v.20 no.4
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• pp.337-346
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• 1992

Trichoderma spp. are an effective control agent for damping-off or other plant diseases. The interaction between. T. hamatum and Rhizoctonia solani on the rhizosphere or surface soil were examined to assess the possible roles of antibiosis or competition in the mechanisms of biological control agents as a basic research. In a proportional comparison, total bacteria, fungi, actinomycetes and Trichoderma spp were 65%, 8.8%, 25.9% and 0.28% respectively in their distribution in the soil. Among Trichoderma spp isolated, the 5 species of Trichoderma spp were indentified as T. koninggii, T. pseudokoninggii, T. aureoviridi, T. hamatum and T. viride respectively. In a mycoparasitic test, one isolate of T. hamatum strain Tr-5 showed an enzymatic ability to break fungal hyphae into piecies and infected on the R. solani hyphae showing a parasitism. Spore germination of the all isolates of Trichoderma spp showed a 1.7-7.3% of germination in natural soil conditions, but the percentage was high in sterile soil indicating all the natural soil were fungistatic on conidia of Trichoderma spp. In rhizosphere competent assay in pea plant, the antagonistic T. hamatum, T. viride, T. koninggii, T. pseudokoninggii showed a colonizing upper soil depth in rhizosphere around 1-3 cm in root zone, but the colonizing ability was much reduced along the deeper the soil depth. Propagule density was decreased in deeper the soil layer. Disease development rate treated alone with plant pathogens, Fusarium solani, Rhizoctonia solani, Cylindrocarpon destructans increased, but disease incidence rate reduced in treatment with combinations with antagonistic T. hamatum strain Tr-5.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.105.1-105
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• 2003

The Plant growth Promoting rhizobacteria (PGPR), Pseudomonas sp. (A3) and Bacillus sp. (AT33) were isolated from the rhizosphere of Amaranthus blitum collected from soil contaminated with chromium. Both bacterial strains quantitatively reduced hexavalent chromium to trivalent chromium. Pseudomonas sp. broughter greater conversion of Cr6+ in the medium (100％) as compared to Bacillus sp.(62％). Phaseolus mungo seeds inoculated with Pseudomonas sp. or Bacillus sp. were grown under different concentration of chromium. The monitored parameters included elongation of shoot and root, fresh weight, dry weight and concentration of chromium in the shoot and root systems. As compared to non inoculated seedlings those inoculated with A3 and AT33 exhibited better growth.

• Journal of Microbiology and Biotechnology
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• v.18 no.6
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• pp.1005-1010
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• 2008

The genus Burkholderia consists of extremely versatile bacteria that occupy diverse niches and are commonly encountered in the rhizosphere of crop plants. In this study, we characterized three plant growth promoting strains assigned as Burkholderia sp. using biochemical and molecular characterization. The Burkholderia spp. strains CBMB40, CBPB-HIM, and CBPB-HOD were characterized using biochemical tests, BIOLOG carbon substrate utilization, fatty acid methyl ester analysis, analysis of recA gene sequences, and DNA-DNA hybridization. The results from these studies indicated that the strains CBMB40, CBPB-HIM, and CBPB-HOD can be assigned under Burkholderia vietnamiensis, Burkholderia ubonensis, and Burkholderia pyrrocinia, respectively.

• 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.

• Microbiology and Biotechnology Letters
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• v.34 no.2
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• pp.180-184
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• 2006

Nineteen nitrogen-fixing bacteria were isolated from rice roots cultivated in the southern part of the Korean peninsula. Among them, three isolates - Stenotrophomonas sp. KNUC89, Pseudomonas sp. KNUC116, and Delftia sp. KNUC133 - showed antifungal activities against phytopathogenic fungi Rhizoctonia solani and Fusarium oxysporum. Besides they could produce auxin and siderophores.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2003.10b
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• pp.14-14
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• 2003

The aim of the present study isto assess the importance of siderophore producing rhizosphere bacteria on the growth of Brassica junceaunder chromium stress. Pseudomonassp. (A4) produced an iron chelating substance siderophores in iron deficient medium. Under chromium stress condition Pseudomonassp. (A4) markedly increased the root and shoot length and also biomass of Brassica juncea as compared to Pseudomonas sp. (A3). This plant growth promotion has been related to the microbial production of siderophore.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2003.10b
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• pp.57-57
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• 2003

The plant growth promoting rhizobacteria (PGPR), Pseudomonas sp. (A3) and Bacillus sp. (AT33) were isolated from the rhizosphere of Amaranthus blitum collected from soil contaminated with chromium. Bothbacterial strains quantitatively reduced hexavalent chromium to trivalent chromium. Pseudomonas sp. broughter greater conversion of Cr6+ in the medium (100%) as compared to Bacillus sp.(62%). Phaseolus mungo seeds inoculated with Pseudomonas sp. or Bacillus sp. were grown under different concentration of chromium. The monitoredparameters included elongation of shoot and root, fresh weight, dry weight and concentration of chromium in the shoot and root systems. As compared to non inoculated seedlings those inoculated with A3 and AT33 exhibited better growth.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2003.10a
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• pp.20-29
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• 2003

The aim of the present study isto assess the importance of siderophore producing rhizosphere bacteria on the growth of Brassica junceaunder chromium stress. Pseudomonassp. (A4) produced an iron chelating substance siderophores in iron deficient medium. under chromium stress condition Pseudomonassp. (A4) markedly increased the root and shoot length and also biomass of Brassica juncea as compared to Pseudomonas sp. (A3). This plant growth promotion has been related to the microbial production of siderophore.

• The Plant Pathology Journal
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• v.33 no.2
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• pp.170-183
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• 2017

Bacterial fruit blotch (BFB), which is caused by Acidovorax citrulli, is a serious threat to watermelon growers around the world. The present study was conducted to screen effective rhizobacterial isolates against 35 different A. citrulli isolates and determine their efficacy on BFB and growth parameters of watermelon. Two rhizobacterial isolates viz. Paenibacillus polymyxa (SN-22), Sinomonas atrocyanea (NSB-27) showed high inhibitory activity in the preliminary screening and were further evaluated for their effect on BFB and growth parameters of three different watermelon varieties under greenhouse conditions. The greenhouse experiment result revealed that SN-22 and NSB-27 significantly reduced BFB and had significant stimulatory effect on total chlorophyll content, plant height, total fresh weight and total dry weight compared to uninoculated plants across the tested three watermelon varieties. Analysis of the 16S ribosomal RNA (rRNA) sequences revealed that strains SN-22 belong to P. polymyxa and NSB-27 to S. atrocyanea with the bootstrap value of 99% and 98%, respectively. The isolates SN-22 and NSB-27 were tested for antagonistic and PGP traits. The result showed that the tested isolates produced siderophore, hydrolytic enzymes (protease and cellulose), chitinase, starch hydrolytic enzymes and they showed phosphate as well as zinc solubilizing capacity. This is the first report of P. polymyxa (SN-22) and S. atrocyanea (NSB-27) as biocontrol-plant growth promoting rhizobacteria on watermelon.