• The Plant Pathology Journal
• /
• v.23 no.2
• /
• pp.70-75
• /
• 2007

We conducted an inoculation test using nine open-pollinated families of pine trees to evaluate their susceptibility and mortality in different densities of pine wood nematode. Three-year-old nine open-pollinated pine families were inoculated with Bursaphelenchus xylophilus at levels of 3,000, 5,000, and 7,000 nematodes/seedling in greenhouse. There were no distinct patterns in latent period among three densities of B. xylophilus in all families. Most families showed the first disease symptoms of needle discoloration within 12-15 days after inoculation. However, open-pollinated progenies of Pinus densiflora showed the longest latent period because none of one-year-old needles were wilted until 14 days after inoculation with 5,000 and 7,000 nematodes. One-year-old needles were wilted earlier than current needles in all tested families with all densities of B. xylophilus. Current needles were not wilted until 14 days after inoculation in all seedlings. The mortality of all seedlings rapidly increased from 35 days to 49 days after inoculation, and all died within 80 days except two seedlings. A 3,000 nematodes/100 ${\mu}L$ with sterilized distilled water are enough to screen 3-year-old pine seedlings for resistance to B. xylophilus.

• Journal of Plant Biology
• /
• v.32 no.1
• /
• pp.1-9
• /
• 1989

An endophyte was isolated from the root nodule of alnus hirsuta. The isolated endophyte was identified as a Frankia sp. through morphological characteristics. Their infectivity and effectivity were confirmed by nitrogen-fixing root nodules induced on inoculated Alnus seedlings. Reisolated endophyte from the induced nodule showed identical morphological characteristics as the first isolate, showing the nodule was induced by the first isolate. Consequently, the first isolate was confirmed as a true symbiont of Almus hirsuta root nodule. The isolate was designated as a Frankia SNU 014201 strain.

• Journal of Korean Society of Forest Science
• /
• v.82 no.4
• /
• pp.319-327
• /
• 1993

The objectives of this study were to isolate ectomycorrhizal fungi associated with roots of Pinus rigida ${\times}$ P. taeda trees planted in Chonbuk and Daejon locations and to identify them, and to observe the morphology of mycorrhizae formed by the isolated fungi. Pinus rigida ${\times}$ P. taeda seedlings formed ectomycorrhizae with Rhizopogon rubescens, Rhizopogon sp. and Suillus pictus isolated from the roots of mature Pinus rigida ${\times}$ P. taeda trees, Pinus rigida ${\times}$ P. taeda seedlings formed ectomycorrhizae with Pisolithus tinetorius too. The root surface of inoculated seedlings was covered with mycelia, and Hartig net were well developed in those roots. The size of vacuole was small, and the protoplasm was planty in ectomycorrhizal cell, compared to nonmycorrhizal cell. But the size of nuclei are not changed even in ectomycorrhizal cell.

• The Korean Journal of Mycology
• /
• v.42 no.4
• /
• pp.312-321
• /
• 2014

Tricholoma bakamatsutake is one of the edible ectomycorrhizal mushrooms as an allied species of Tricholoma matsutake. This is the first report on physical characteristics of T. bakamatsutake strains collected from Quercus mongolica forests in Korea. The pure cultures of these strains were isolated from the tissues of fruit bodies and the culture characteristics were investigated under different conditions (media, temperatures, nitrogen sources). Most strains showed the highest mycelial growth on potato dextrose agar (PDA) at 20 or $25^{\circ}C$. Two strains of T. bakamatsutake preferred the ammonium-form rather than the nitrate-form as an inorganic nitrogen source. T. bakamatsutake showed significantly slower mycelial growth when compared with T. matsutake from a Korean forest, although the optimum culture conditions for the two allied species were similar. We also tested the ability to form mycorrhizae as well as cellulase activity of T. bakamatsutake. All strains showed cellulase activity on a carboxymethylcellulose (CMC) agar plate. The mycorrhizae on axenic Pinus densiflora seedlings were formed by two strains of T. bakamatsutake after 3 or 8 months of inoculation. P. densiflora seedlings inoculated with T. bakamatsutake had a much higher biomass than un-inoculated seedlings.

• Korean Journal of Environment and Ecology
• /
• v.20 no.4
• /
• pp.425-435
• /
• 2006

The objectives of this research were to investigate the drought resistance as well as the growth of Wisteria floribunda seedlings with the soil water conditions. The seedlings for the research were grown in pots with strict water content control on a frame located outdoors. During the experiments, the soil water contents were adjusted to 5, 10, 20, 30, 40, 50, 60, and 70%. In addition, the effects of Rhizobium inoculation on the growth of seedlings were investigated. The experimental results are summarized as follows: 1. The seedlings in the pots with 5% soil water content withered to death due to the water stress. Withering or any distinct growth was not observed from the seedlings in the 10% soil water content. It can be inferred from these results that about 5% of soil water content is the wilting point of W. floribunda seedlings and about 10% is the critical soil water content of its growth in this experiment soils. Therefore, it seems that W. floribunda possesses a good drought resistance. 2. From the analyses of the main growth parameters such as stem elongation, diameter growth, leaf area growth and total dry weight, it was found that the seedling growth can be improved with increasing soil water contents. The relation between each growth parameter(Y) and the soil water contents(W) was well described by a quadratic equation, $Y=a+bW+cW^2$. 3. In soil water contents higher than 20%, the seedling growth(Y) was remarkable along with-its extended growing period, and related to the growing period(D) by a quadratic equation, $Y=a+bD+cD^2$. 4. The artificial inoculation of Rhizobiun promoted the growth of Wisteria floribunda seedlings. 5. Rhizobium was found to be more readily inoculated and to form more root nodules compared to seedlings grown in higher soil water contents.

• Korean Journal of Soil Science and Fertilizer
• /
• v.47 no.3
• /
• pp.141-146
• /
• 2014

The necessity to develop economical and eco-friendly technologies is steadily increasing. Plant growth promoting rhizomicrobial strains PGPR are a group of microorganisms that actively colonize plant roots and increase plant growth and yield. Pot experiments were used to investigate the potential of some rhizobacterial strains to enhance the Brassica rapa growth. Microbial strains were successfully isolated from the rhizosphere of Panax ginseng and characterized based on its morphological and plant growth promotion characters. Surface disinfected seeds of Wisconsin Fast B. rapa were inoculated with the selected PGPR microorganisms. The different pots treatments were inoculated by its corresponding PGPR ($10^7cfu\;mL^{-1}$) and incubated in the growth chamber at $25^{\circ}C$ and 65% RH, the light period was adjusted to 24 hours (day). NPK chemical fertilizer and trade product (EMRO, USA) of effective microorganisms as well as un-inoculated control were used for comparison. Plants harvested in 40 days were found to have significant increase in leaf chlorophyll units and plant height and also in dry weight of root and shoot in the inoculated seedlings. Root and shoot length and also leaf surface area significantly were increased by bacterial inoculation in sterile soil. The study suggests that Rhodobacter capsulatus and Azotobacter chroococcum are beneficial for B. rapa growth as they enhance growth and induced IAA production and phosphorus solubilization. This study presents some rhizomicrobial strains that significantly promoted growth of Wisconsin Fast Plant B. rapa in pot experiment under different soil conditions.

• Korean Journal of Environmental Agriculture
• /
• v.13 no.3
• /
• pp.288-300
• /
• 1994

Fusarium oxysporum was isolated most frequently, followed by F. moniliforme, and F. solani from infected asparagus plants grown in the field. In pathogenicity tests both with seedlings and plantlets, F. moniliforme showed higher virulence than Fusarium oxysporum did in general. Fusarium moniliforme showed more consistent virulence on both seedlings and plantlets than F. oxysporum did. Fusarium oxysporum showed higher virulence on plantlets than on seedlings. Fusarium solani showed very weak or no sign of virulence on seedlings and plantlets, respectively, in both tests. In protection tests with plantlets, most protection of asparagus against virulent fusarial infections occurred when challenge isolates were inoculated five or seven days after inoculation of protective fusarial species. Avirulent F. oxysporum was a more effective protective agent against infection of F. moniliforme than it was against F. oxysporum. Fusarium solani was more effective against infection of F. oxysporum than it was against F. moniliforme.

• The Plant Pathology Journal
• /
• v.25 no.3
• /
• pp.256-262
• /
• 2009

The potential of. nonpathogenic Fusarium oxysporum strain Avr5, either alone or in combination with chitosan and Bion, for inducing defense reaction in tomato plants inoculated with F. oxysporum f. sp lycopersici, was studied in vitro and glasshouse conditions. Application Bion at concentration of 5, 50, 100 and $500{\mu}g$/ml, and the highest concentration of chitosan reduced in vitro growth of the pathogen. Nonpathogenic F. oxysporum Avr5 reduced the disease severity of Fusarium wilt of tomato in split plants, significantly. Bion and chitosan applied on tomato seedlings at concentration $100{\mu}g$ a.i./plant; 15, 10 and 5 days before inoculation of pathogen. All treatments significantly reduced disease severity of Fusarium wilt of tomato relative to the infected control. The biggest disease reduction and increasing tomato growth belong to combination of nonpathogenic Fusarium and Bion. Growth rate of shoot and root markedly inhibited in tomato plants in response to tomato Fusarium wilt as compared with healthy control. These results suggest that reduction in disease incidence and promotion in growth parameters in tomato plants inoculated with nonpathogenic Fusarium and sprayed with elicitors could be related to the synergistic and cooperative effect between them, which lead to the induction and regulation of disease resistance. Combination of elicitors and non-pathogenic Fusarium synergistically inhibit the growth of pathogen and provide the first experimental support to the hypothesis that such synergy can contribute to enhanced fungal resistance in tomato. This chemical could provide a new approach for suppression of tomato Fusarium wilt, but its practical use needs further investigation.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.3
• /
• pp.474-480
• /
• 2007

Fusarium wilt of cucumbers was effectively controlled by Escherichia coli expressing an endochitinase gene (chiA), and the rate was as effective (60.0%) as the wild-type strain S. proteamaculans 3095 (55.0%) where the gene was cloned. However, live cells of soil inoculated E. coli host harboring the chiA gene did not proliferate but declined 100-fold from $10^8$ CFU during the first week and showed less than 10 cells after day 14, suggesting that E. coli was able to express and produce the chitinase enzyme to the soil even as the population was gradually decreasing. Because the majority of the strains was alive for only a short period of time and the Fusarium-affected seedlings showed symptoms of wilting within 7-10 days, it seems that the pathogen control was decided early after the introduction of the biocontrol agent, eliminating the survival of the antagonist. These results indicated that soil inoculated E. coli could sufficiently express and produce the recombinant protein to control the pathogen, and root or soil colonization of the antagonist might not be a significant factor in determining the efficacy of biological control.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.11
• /
• pp.1431-1438
• /
• 2009

The role of plant growth-promoting rhizobacteria (PGPR) in the phytoremediation of heavy-metal-contaminated soils is important in overcoming its limitations for field application. A plant growth-promoting rhizobacterium, Serratia sp. SY5, was isolated from the rhizoplane of barnyard grass (Echinochloa crus-galli) grown in petroleum and heavy-metal-contaminated soil. This isolate has shown capacities for indole acetic acid production and siderophores synthesis. Compared with a non-inoculated control, the radicular root growth of Zea mays seedlings inoculated with SY5 can be increased by 27- or 15.4-fold in the presence of 15 mg-Cd/l or 15 mg-Cu/l, respectively. The results from hydroponic cultures showed that inoculation of Serratia sp. SY5 had a favorable influence on the initial shoot growth and biomass of Zea mays under noncontaminated conditions. However, under Cd-contaminated conditions, the inoculation of SY5 significantly increased the root biomass of Zea mays. These results indicate that Serratia sp. SY5 can serve as a promising microbial inoculant for increased plant growth in heavy-metal-contaminated soils to improve the phytoremediation efficiency.