• Korean Journal of Soil Science and Fertilizer
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• v.49 no.3
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• pp.251-258
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• 2016

A rhizobacterium LPN-2, which showed strong antifungal activity and auxin producing ability, was isolated from a farmland in North Gyeongsang Province, South Korea. Based on analysis of the 16S rDNA sequence, strain LPN-2 was identified as a novel strain of Burkholderia and was designated as Burkholderia sp. LPN-2. In vitro experiments showed that the isolated stain LPN-2 significantly produced auxin within 48 hr incubation. In order to check for PGPR function we performed in vivo growth promoting test in different crops, including mung bean, pea and cabbage. Application of Burkholderia sp. LPN-2 showed dramatic growth promoting effect on all the tested plants. We also confirmed siderophore and cellulase productions by Burkholderia sp. LPN-2 using CAS blue agar and CMC plate test. Further treatment with LPN-2 and the crude culture broth was effective in suppressing anthracnose in vitro test and also reduced incidence and severity of anthracnose in apple and pepper. Taken together, we conclude that Burkholderia sp. LPN-2 might be used as organic fertilizer for effective crop production in organic farming.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1650-1655
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• 2006

Bacteria belonging to the genus Paenibacillus are facultatively anaerobic endospore formers and are attracting growing ecological and agricultural interest, yet their genome information is very limited. The present study surveyed the genomic features of P. polymyxa ATCC $842^T$ using pulse-field gel electrophoresis of restriction fragments and sample genome sequencing of 1,747 reads (approximately 17.5% coverage of the genome). Putative functions were assigned to more than 60% of the sequences. Functional classification of the sequences showed a similar pattern to that of B. subtilis. Sequence analysis suggests nitrogen fixation and antibiotic production by P. polymyxa ATCC $842^T$, which may explain its plant growth-promoting effects.

• The Plant Pathology Journal
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• v.34 no.6
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• pp.459-469
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• 2018

Plants and microorganisms (microbes) use information from chemicals such as volatile compounds to understand their environments. Proficiency in sensing and responding to these infochemicals increases an organism's ecological competence and ability to survive in competitive environments, particularly with regard to plant-pathogen interactions. Plants and microbes acquired the ability to sense and respond to biogenic volatiles during their evolutionary history. However, these signals can only be interpreted by humans through the use of state-of the-art technologies. Newly-developed tools allow microbe-induced plant volatiles to be detected in a rapid, precise, and non-invasive manner to diagnose plant diseases. Beside disease diagnosis, volatile compounds may also be valuable in improving crop productivity in sustainable agriculture. Bacterial volatile compounds (BVCs) have potential for use as a novel plant growth stimulant or as improver of fertilizer efficiency. BVCs can also elicit plant innate immunity against insect pests and microbial pathogens. Research is needed to expand our knowledge of BVCs and to produce BVC-based formulations that can be used practically in the field. Formulation possibilities include encapsulation and sol-gel matrices, which can be used in attract and kill formulations, chemigation, and seed priming. Exploitation of biogenic volatiles will facilitate the development of smart integrated plant management systems for disease control and productivity improvement.

• Journal of Ginseng Research
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• v.39 no.3
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• pp.213-220
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• 2015

Background: Korean ginseng (Panax ginseng Meyer) is a perennial herb prone to various root diseases, with Phytophthora cactorum being considered one of the most dreaded pathogens. P. cactorum causes foliar blight and root rot. Although chemical pesticides are available for disease control, attention has been shifted to viable, eco-friendly, and cost-effective biological means such as plant growth-promoting rhizobacteria (PGPR) for control of diseases. Methods: Native Bacillus amyloliquefaciens strain HK34 was isolated from wild ginseng and assessed as a biological control agent for ginseng. Leaves from plants treated with HK34 were analyzed for induced systemic resistance (ISR) against P. cactorum in square plate assay. Treated plants were verified for differential expression of defense-related marker genes using quantitative reverse transcription polymerase chain reaction. Results: A total of 78 native rhizosphere bacilli from wild P. ginseng were isolated. One of the root-associated bacteria identified as B. amyloliquefaciens strain HK34 effectively induced resistance against P. cactorum when applied as soil drench once (99.1% disease control) and as a priming treatment two times in the early stages (83.9% disease control). A similar result was observed in the leaf samples of plants under field conditions, where the percentage of disease control was 85.6%. Significant upregulation of the genes PgPR10, PgPR5, and PgCAT in the leaves of plants treated with HK34 was observed against P. cactorum compared with untreated controls and only pathogen-treated plants. Conclusion: The results of this study indicate HK34 as a potential biocontrol agent eliciting ISR in ginseng against P. cactorum.

• Korean Journal of Organic Agriculture
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• v.26 no.3
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• pp.463-475
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• 2018

Salinity and extreme temperature stresses affect growth and productivity of crops negatively. Beneficial bacteria, including plant growth-promoting rhizobacteria (PGPR) induce growth promotion and tolerance of plants under abiotic stress conditions. In the present study, 20 strains were selected from 1944 isolated bacteria based on three plant growth-promoting (PGP) traits-aminocyclopropane-1-carboxylate deaminase activity, phosphate solubilization, indole-3-acetic acid production, and growth ability under salinity and extreme temperature stress conditions. Seven among the 20 strains were selected based on growth-promoting effects on plants under saline or temperature stresses in tomato plants. It was expected that the seven strains could induce tolerance of tomato plants under salinity or extreme temperature stresses, which implies that these seven strains can act as potential inducers of multiple stresses tolerance in tomato plants.

• The Plant Pathology Journal
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• v.28 no.3
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• pp.270-281
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• 2012

The bacteria B1-9 that was isolated from the rhizosphere of the green onion could promote growth of pepper, cucumber, tomato, and melon plants. In particular, pepper yield after B1-9 treatment on the seedling was increased about 3 times higher than that of control plants in a field experiment. Partial 16S rDNA sequences revealed that B1-9 belongs to the genus Pantoea ananatis. Pathogenecity tests showed non-pathogenic on kimchi cabbage, carrot, and onion. The functional characterization study demonstrated B1-9's ability to function in phosphate solubilization, sulfur oxidation, nitrogen fixation, and indole-3-acetic acid production. To trace colonization patterns of B1-9 in pepper plant tissues, we used $DRAQ5^{TM}$ fluorescent dye, which stains the DNAs of bacteria and plant cells. A large number of B1-9 cells were found on the surfaces of roots and stems as well as in guard cells. Furthermore, several colonized B1-9 cells resided in inner cortical plant cells. Treatment of rhizosphere regions with strain B1-9 can result in efficient colonization of plants and promote plant growth from the seedling to mature plant stage. In summary, strain B1-9 can be successfully applied in the pepper plantation because of its high colonization capacity in plant tissues, as well as properties that promote efficient plant growth.

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1001-1010
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• 2005

Bacillus megaterium KL39, an antibiotic-producing plant growth promoting rhizobacterium (PGPR), was selected from soil. The antifungal antibiotic, denoted KL39, was purified from culture filtrate by column chromatography using Dion HP-20, Silica gel, Sephadex LH-20, and prep-HPLC. Thin layer chromatography, employing the solvent system of ethanol:ammonia:water=8:1:1, showed the $R_{f}$. value of 0.32. The antibiotic KL39 showed a negative reaction with ninhydrin solution, positive with iodine vapor, and also positive with Ehrlich reagent. It was soluble in methanol, ethanol, butanol, and acetonitrile, but insoluble in chloroform, toluene, hexane, ethyl ether, or acetone. Its UV spectrum had the maximum absorption at 208 nm. Amino acid composition, FAB-mass, $^{1}H-NMR,\;^{13}C-NMR$, and atomic analyses showed that the antibiotic KL39 (MW=1,071) has a structure very similar to iturin E. The antibiotic KL39 has a broad antifungal spectrum against a variety of plant pathogenic fungi including Rhizoctonia solani, Pyricularia oryzae, Monilinia froeticola, Botrytis cinenea, Altenaria kikuchiana, Fusarium oxysporum, and F. solani. An MIC value of $10\;{\mu}g/ml$ was determined for Phytophthora capsici. Macromolecular incorporation studies with P. capsici using radioactive [$^{3}H-adenine$] as the precursor, indicated that the antibiotic KL39 strongly inhibits the DNA biosynthesis of the fungal cell. Microscopic observation of the antifungal action showed abnormal hyphal swelling of P. capsici. The purified antibiotic KL39 was very effective for the biocontrol of in vivo Phytophthora-blight disease of pepper.

• Microbiology and Biotechnology Letters
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• v.35 no.1
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• pp.58-65
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• 2007

The role of soil microorganisms, specifically rhizobacteria, in the development of rhizoremediation techniques is important to speed up the process and to increase the rate of mobilization or absorption of heavy metals to the plant. In this study, Methylobacterium sp. SY-NiR1 was isolated from the rhizosphere soils of plants in oil and heavy metal-contaminated soil. Based on its pink pigmented colony, rod-shape cells, and belonging in $\alpha-Proteobacteria$, Methylobacterium sp. SY-NiR1 is considered a pink-pigmented facultative methylotroph. SY-NiR1 had the ability to produce indole acetic acid which is one of phytohormones. This bacterium showed resistance against multiple heavy metals such as Cd, Cr, Cu, Pb, Ni, Zn, and the order of its resistance based on $EC_{50}$ was Zn > Ni > Cu > Pb > Cd > Cr. Therefore, Methylobacterium sp. SY-NiR1 can stimulate seed germination and plant growth in soil contaminated with heavy metals.

• Journal of Microbiology and Biotechnology
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• v.15 no.1
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• pp.29-34
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• 2005

W/O/W (water-in-oil-in-water) type multiple emulsion was applied to improve the storage stability of an antagonistic microorganism, Burkholderia gladioli. Encapsulation of microorganism into a W/O/W emulsion was conducted by using a two-step emulsification method. W/O/W emulsion was prepared by the incorporation of B. gladioli into rapeseed oil and the addition of polyglycerin polyriconolate (PGPR) and castor oil polyoxyethylene (COG 25) as the primary and secondary emulsifier, respectively. Microcrystalline cellulose was used as an emulsion stabilizer. To evaluate the usefulness of W/O/W emulsion formulation as a microbial pesticide for controlling the bacterial wilt pathogen (Ralstonia solanacearum), the storage stability and antagonistic activity of emulsion formulation were tested in vitro. The storage stability test revealed that the viability of formulated cells in emulsion was higher than that of unformulated cells in culture broth. At $4^{\circ}C$, the viabilities of formulated cells and unformulated cells at the end of 20 weeks decreased to about 2 and 5 log cycles, respectively. At $37^{\circ}C$, the viability of formulated cells decreased to only 2 log cycles at the end of storage. On the other hand, the viable cells in culture broth were not detected after 13 weeks. In activity test, formulated cells in emulsion were more effective in inhibiting the growth of pathogen than unformulated cells in culture broth. Unformulated cells completely lost their antagonistic activity during storage under similar conditions. The W/O/W multiple emulsion formulation was shown to be useful as the novel liquid formulation for biological control.

• Mycobiology
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• v.36 no.4
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• pp.236-241
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• 2008

The colonization of an arbuscular mycorrhizal fungus Glomus intraradices BEG110 in the soil caused a decrease in disease severity in cucumber plants after fungal inoculation with Colletotrichum orbiculare. In order to illustrate the resistance mechanism mediated by G. intraradices BEG110, infection patterns caused by C. orbiculare in the leaves of cucumber plants and the host cellular responses were characterized. These properties were characterized using transmission electron microscopy on the leaves of cucumber plants grown in soil colonized with G. intraradices BEG110. In the untreated plants, inter- and intra-cellular fungal hyphae were observed throughout the leaf tissues during both the biotrophic and necrotrophic phases of infection. The cytoplasm of fungal hyphae appeared intact during the biotrophic phase, suggesting no defense response against the fungus. However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls. These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast. In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.