• Mycobiology
• /
• v.30 no.1
• /
• pp.31-36
• /
• 2002

Soil bacteria were screened for the ability to control cucumber anthracnose caused by Colletotrichum orbiculare through induced systemic resistance(ISR). Sixty-four bacterial strains having in vitro antifungal activity were used for selecting ISR-inducing strains in cucumber. Cucumber seeds(cv. Baeknokdadagi) were sown in potting mixtures incorporated with the soil bacteria, at a rate of ca. $10^8$ cells per gram of the mixture. Two week-old plants were then transplanted into the steam-sterilized soil. Three leaf-stage plants were inoculated with a conidial suspension($5{\times}10^5$ conidia/ml) of C. orbiculare. Diseased leaf area(%) and number of lesions per $cm^2$ leaf were evaluated on third leaves of the plants, $5{\sim}6$ days after inoculation. Among 64 strains tested, nine strains, GC-B19, GC-B35, GK-B18, MM-B22, PK-B14, RC-B41, RC-B64, RC-B65, and RC-B77 significantly(P=0.05) reduced anthracnose disease compared to the untreated control. In contrast, some bacterial strains promoted susceptibility of cucumber to the disease. From the repeated experiments using the nine bacterial strains, GC-B19, MM-B22, PK-B14, and RC-B65 significantly(P=0.05) reduced both diseased leaf area(%) and number of lesions per $cm^2$ leaf in at lease one experiment. These strains with control efficacy of $37{\sim}80%$ were determined to be effective ISR-inducing strains.

• Journal of Microbiology and Biotechnology
• /
• v.20 no.12
• /
• pp.1605-1613
• /
• 2010

Twenty-nine P. polymyxa strains isolated from rhizospheres of various crops were clustered into five genotypic groups on the basis of BOX-PCR analysis. The characteristics of several plant growth-promoting factors among the isolates revealed the distinct attributes in each allocated group. Under gnotobiotic conditions, inoculation of pepper roots with P. polymyxa isolates significantly increased the biomass in 17 of total 29 treated plants with untreated plants. Experiments on induced systemic resistance (ISR) against bacterial spot pathogen Xanthomonas axonopodis pv. vesicatoria in pepper by P. polymyxa strains were conducted and only one isolate (KNUC265) was selected. Further studies into ISR mediation by the KNUC265 strain against the soft-rot pathogen Erwinia carotovora subsp. carotovora in tobacco demonstrated that the tobacco seedlings exposed to either bacterial volatiles or diffusible metabolites exhibited a reduction in disease severity. In conclusion, ISR and plant growth promotion triggered by P. polymyxa isolates were systemically investigated on pepper for the first time. The P. polymyxa KNUC265 strain, which elicited both ISR and plant growth promotion, could be potentially used in improving the yield of pepper and possibly of other crops.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.105.3-106
• /
• 2003

Bacillus subtilis strain BAC02-4 was tested for its ability induced systemic resistance(ISR) in rice against Magnaporthe grisea We extend these studies to investigate the biological induction of systemic resistance in rice following treatment with the inducer isolate BAC02-4 and naturally infested with Pyricularia oryzae. We also determine levels of ISR activity during the period between disease development and the onset of systemic resistance. Comparition of lesion number according to applied concentration of BAC02-4 to 'Nagdongbyeo' when naturally infested with the conidia of P. grisea. Results from the blast nusery trial using the 'Nagdongbyeo' showed very low rice blast severity with the inducer concentration of 10$\^$8/ cfu level. Considering the low level of treatment and untreated control were observed to have developed typical susceptible lesion type. Highest protection against the rice blast pathogen when applied three times with 5 days interval as root drench at 5 to 6 leaf stage before pathogen challenge. But higher dose of bacterial inducer produced a little stunted plants with less number lesions and delayed disease development. Diseased leaf area of treated with suspension of the isolate which gave about 80％ of control efficacy at 20 days later comparable to that in noninfested, inducer-free soil.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2002.11a
• /
• pp.86.1-86
• /
• 2002

• Mycobiology
• /
• v.33 no.1
• /
• pp.35-40
• /
• 2005

Selected isolates of Pseudomonas fluorescens (Pf4-92 and PfRsC5) and P. aeruginosa (PaRsG18 and PaRsG27) were examined for growth promotion and induced systemic resistance against Fusarium wilt of chickpea. Significant increase in plant height was observed in Pseudomonas treated plants. However, plant growth was inhibited when isolates of Pseudomonas were used in combination with Fusarium oxysporum f. sp. ciceri (FocRs1). It was also observed that the Pseudomonas spp. was colonized in root of chickpea and significantly suppressed the disease in greenhouse condition. Rock wool bioassay technique was used to study the effect of iron availability on the induction of systemic resistance to Fusarium wilt of chickpea mediated by the Pseudomonas spp. All the isolates of Pseudomonas spp. showed greater disease control in the induced systemic resistance (ISR) bioassay when iron availability in the nutrient solution was low. High performance liquid chromatography (HPLC) analysis indicated that an the bacterial isolates produced more salicylic acid (SA) at low iron ($10\;{\mu}M$ EDDHA) than high iron availability ($10\;{\mu}Fe^{3+}$ EDDHA). Except PaRsG27, all the three isolates produced more pseudobactin at low iron than high iron availability.

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

• Journal of Microbiology and Biotechnology
• /
• v.18 no.10
• /
• pp.1659-1662
• /
• 2008

Pseudomonas chlororaphis O6 exhibits induced systemic resistance (ISR) against P. syringae pv. tabaci in tobacco. To identify one of the ISR metabolites, O6 cultures were extracted with organic solvents, and the organic extracts were subjected to column chromatography followed by spectroscopy analyses. The ISR bioassay-guided fractionation was carried out for isolation of the metabolite. High-resolution mass spectrometric analysis of the metabolite found $C_{9}H_{9}O_{3}N$ with an exact mass of 179.0582. LC/MS analysis in positive mode showed an $(M+H)^{+}$ peak at m/z 180. Nuclear magnetic resonance ($^{1}H,\;^{13}C$) analyses identified all protons and carbons of the metabolite. Based on the spectroscopy data, the metabolite was identified as 4-(aminocarbonyl) phenylacetate (4-ACPA). 4-ACPA applied at 68.0 mM exhibited ISR activity at a level similar to 1.0 mM salicylic acid. This is the first report to identify an ISR metabolite produced by P. chlororaphis O6 against the wildfire pathogen P. syringae pv. tabaci in tobacco.

• The Plant Pathology Journal
• /
• v.17 no.3
• /
• pp.174-179
• /
• 2001

The plant growth-promoting Pseudomonas strains, WR8-3 (Pseudomonas fluorescens), WR9-11 (Pseudomonas sp.) and WR9-16 (P.putida), which induced resistance systematically in watermelon to gummy stem rot were investigated on their induced systemic resistance(ISR)-related characteristics. The pyoverdine production was repressed in the standard succinate medium by increasing the concentration of $\textrm{FeCL}_3$. But the iron-binding ability on chrome azurol S agar media (CAS) was observed only in the strains, WR8-3 and WR9-16. When the two strains were mutated, the resulting iron-binding siderophore-negative mutants, WR8-3m and WR 9-16m, failed to promote the growth of watermelon and to induce resistance. The strains, WR8-3 and WR 9-16, slightly inhibited the growth of Didymella bryoniae at a low concentration of $\textrm{FeCL}_3$ on Kong's medium B, but not to exert control dffect. The strain WR9-11 showed antagonism in the concentration of $\textrm{FeCL}_3$ from 0 to $1,000\mu\textrm{M}$. When the crude lipoplysaccharide of each strain was treated in the rhizosphere of watermelon, mean lesion area was similar to that of the untreated control. The strains, WR9-11 and WR9-16 produced some level of hydrogen cyanide (HCN). Salicylic acid production was not detected in all of the strains.

• Korean Journal of Plant Resources
• /
• v.20 no.2
• /
• pp.216-219
• /
• 2007

Root colonization by a rhizobacterium, Pseudomonas chlororaphis O6, elicited induced systemic resistance (ISR) in the leaves of cucumber plants against fungal and bacterial pathogens. To understand the role of unique genes during strain O6-mediated ISR, a suppressive subtractive hybridization method was undertaken and led to isolation of twenty-five distinct genes. The transcriptional levels of all the genes showed an increase much earlier under O6 treatment than in water control plants only after challenge with pathogen, while no difference detected on the plants without pathogen challenge. This suggests that O6-mediated ISR is associated with the priming phenomenon, an enhanced capacity for the rapid and effective activation of cellular defense responses after challenge inoculation.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.90.1-90
• /
• 2003

Colonization of Pseudomonas chlororaphis O6, a nonpathogenic rhizobacterium, on the roots induced systemic resistance in cucumber plants against tai-get leaf spot, a foliar disease caused by Corynespora cassiicola. A cDNA library was constructed using mRNA extracted from the cucumber leaves 12 h after inoculation with C. cassiicola, which roots had been previously treated with O6. To identify the genes involved in the O6-mediated induced systemic resistance (ISR), we employed a subtractive hybridization method using mRNAs extracted from C cassiicola-inoculated cucumber leaves with and without previous O6 treatment on the plant roots. Differential screening of the cDNA library led to the isolation of 5 distinct genesencoding a GTP-binding protein, a putative senescence-associated protein, a galactinol synthase, a hypersensitive-induced reaction protein, and a putative aquaporin. Expressions of these genes are not induced by O6 colonization alone. Before challenge inoculation, no increase in the gene transcriptions could be detected in previously O6-treated and untreated plants but, upon subsequent inoculation with the pathogenic fungus, transcription levels in O6-treated plants rose significantly faster and stronger than in untreated plants. Therefore, the O6-mediated ISR may be associated with an enhanced capacity for the rapid and effective activation of cellular defense responses which becomes apparent only after challenge inoculation on the distal, untreated plant parts, as suggested by Conrath et al. (2002). This work was supported by a grant R11-2001-092-02006-0 from the Korea Science and Engineering Foundation through the Agricultural Plant Stress Research Center at Chonnam National University.