• Korean Journal of Microbiology
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• v.50 no.1
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• pp.40-45
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• 2014

In order to increase the persistence of plant growth promoting rhizobacteria (PGPR) in rhizpsphere soil, the growth of tomato was examined after the application of Arthrobacter woluwensis ED immobilized in alginate bead, which was known as PGPR. When tomato seedlings were treated with A. woluwensis ED of $1{\times}10^6$ cells g $soil^{-1}$ and incubated for 30 days in a plant growth chamber, the shoot length, root length, fresh weight and dry weight of the grown tomato plants treated with the suspended inoculants significantly increased by 36.2, 59, 51.1, and 37.5%, respectively compared to those of the uninoculated control. The treatment of the immobilized bacteria increased those by 42, 67.4, 62.5, and 60.4%, respectively compared to those of the uninoculated control. Therefore, the enhancement of tomato growth by the treatment of the immobilized bacteria was higher than those by the suspended inoculants. The effects of the inoculation on indigenous bacterial community and the fate of the inoculated bacteria were monitored by denaturing gradient gel electrophoresis analysis. The DNA band intensity of A. woluwensis ED in the tomato rhizosphere treated with the suspended inoculants continuously decreased after the inoculation, but the band intensity in the tomato rhizosphere soils treated with the immobilized inoculants showed the maximum at 1 week after inoculation and the decreasing rate was less than that of the suspended inoculants, which indicated the longer maintenance of the immobilized bacteria at rhizosphere soils. Therefore, encapsulation of PGPR in alginate beads may be more effective than liquid inoculant for the plant growth promotion and survival of PGPR at plant rhizosphere.

• Research in Plant Disease
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• v.14 no.1
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• pp.32-36
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• 2008

Bacterial wilt caused by Ralstonia solanacearum has become a severe problem on tomato in Korea and no effective control measures are available yet. Pseudomonas species play key roles for the biocontrol of many plant diseases especially in soil. A rhizobacterial population of 150 Pseudomonas strains, isolated from the rhizosphere soil of various plants grown at different sites, was screened for 2,4-diacetylphloroglucinol producing gene (PhlD) by PCR. Two strains (P83 and P84) among them were found to be phlD positive. When the isolates were analysed by 16S rDNA (Sensu Stricto), all isolates yielded amplified products of 1,018bp. Of the 150 isolates of Pseudomonas spp., a bacterial strain P. putida P84 isolated from tomato rhizosphere showed to suppress a wide range of phytopathogenic bacteria in vitro. The best source of carbon for P84 strain were glucose, arabinose, inositol and melibiose. In greenhouse experiments, P84 strain suppressed the development of bacterial wilt in tomato with a control value of 60%.

• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1613-1620
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• 2012

Bacterial wilt caused by Ralstonia solanacearum is a devastating disease of many economically important crops. Since there is no promising control strategy for bacterial wilt, phage therapy could be adopted using virulent phages. We used phage PE204 as a model lytic bacteriophage to investigate its biocontrol potential for bacterial wilt on tomato plants. The phage PE204 has a short-tailed icosahedral structure and double-stranded DNA genome similar to that of the members of Podoviridae. PE204 is stable under a wide range of temperature and pH, and is also stable in the presence of the surfactant Silwet L-77. An artificial soil microcosm (ASM) to study phage stability in soil was adopted to investigate phage viability under a controlled system. Whereas phage showed less stability under elevated temperature in the ASM, the presence of host bacteria helped to maintain a stable phage population. Simultaneous treatment of phage PE204 at $10^8$ PFU/ml with R. solanacearum on tomato rhizosphere completely inhibited bacterial wilt occurrence, and amendment of Silwet L-77 at 0.1% to the phage suspension did not impair the disease control activity of PE204. The biocontrol activities of phage PE204 application onto tomato rhizosphere before or after R. solanacearum inoculation were also investigated. Whereas pretreatment with the phage was not effective in the control of bacterial wilt, post-treatment of PE204 delayed bacterial wilt development. Our results suggested that appropriate application of lytic phages to the plant root system with a surfactant such as Silwet L-77 could be used to control the bacterial wilt of crops.

• Korean Journal of Organic Agriculture
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• v.14 no.2
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• pp.219-228
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• 2006

This study was conducted to examine the distribution of arbuscular mycorrhizal fungi (AMF) in the soil grown tomato plants in Damyang districts. We collected twenty one soil samples from the rhizosphere of tomato plants which were grown under structure. Number of spores/g in the soil sized over $500{\mu}m,\;355{\sim}500{\mu}m,\;251{\sim}354{\mu}m,\;107{\sim}250{\mu}m\;and\;45{\sim}106{\mu}m$ were 0.01, 0.02, 0.09, 0.9, and 2.0. Total number of spores/g in the fresh soil were 3.02. Mycorrhizal root infection by vesicles, hyphae and arbuscules were 18.0%, 6.0% and 2.0%. To identify the genus of arbuscular mycorrhizal fungi, isolated mycorrhizal spores from the soil grown tomato plants were inoculated into the host plant of sudangrass and mass propagated for 4 months. As a result of identification, mycorrhizal spores were identified as Glomus sp., Gigaspora sp. and Acaulospora sp.

• Korean Journal Plant Pathology
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• v.10 no.1
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• pp.25-28
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• 1994

One hundred fifty four our of 262 isolates of Fusarium oxysporum obtained from healthy plant tissues of various crops and their rhizosphere soil were found to be nonpathogenic to cucumber plants. The nonpathogenic isolates were frequently found from sesame plant tissues and rhizosphere soil, but less from healthy plant tissues of cucumber and water melon. When the 154 nonpathogenic isolates were preinoculated into cucumber seedlings, and then challenge-inoculated with Fusarium wilt pathogen, 21 isolates protected effectively cucumber plants from Fusarium wilt infections. A year later, 9 out of 21 isolates fully sustained their protective effect. Among 9 isolates showing good protective effects, 7 were isolates from cucumber plants. These 9 isolates except 1 isolate, were not pathogenic to water melon, chines melon, tomato and sesame.

• Korean Journal Plant Pathology
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• v.10 no.1
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• pp.29-33
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• 1994

One hundred fifty four out of 262 isolates of Fusarium oxysporum obtained from healthy plant tissues of various crops and their rhizosphere soil were found to be nonpathogenic to cucumber plants. The nonpathogenic isolates were frequently found from sesame plant tissues and rhizosphere soil, but less from healthy plant tissues of cucumber and water melon. When the 154 nonpathogenic isolates were preinoculated into cucumber seedlings, and then challenge-inoculated with Fusarium wilt pathogen, 21 isolates protected effectively cucumber plants from Fusarium wilt infections. A year later, 9 out of 21 isolates fully sustained their protective effect. Among 9 isolates showing good protective effects, 7 were isolates from cucumber plants. These 9 isolates, except 1 isolate, were not pathogenic to water melon, chinese melon, tomato and sesame.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.2
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• pp.121-126
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• 2000

Composition of fungal communities in three microhabitats such as soil, rhizosphere and rhizoplane were studied to understand the root environment of healthy and diseased plants in Phytophthora non-infested and infested fields, respectively. Samples were collected from the tomato- and red pepper-growing greenhouses in Kyungsang-Nam Province on April, 1999. Twenty-five species were isolated from each vegetation field using the dilution plate technique. There were a greater variety of species in infested fields than non-infested and in soils than in both rhizospheres and rhizoplanes. The number of species isolated were varied amongst the different microhabitats. A Trichoderma species was isolated only from non-infested fields.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.2
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• pp.179-183
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• 1987

A series of laboratory experiments were conducted to find out the populations and identification of soil bacteria, fungi and their B/F ratio in the rhizosphere of intensively cultivatad hot-pepper, garlic, flower plants, chinese cabbage, and round onion. The results obtained are summarized as follows: 1. The number of bacteria, fungi and their B/F ratio are remarkably lower than that of normal paddy soils. 2. Nitrate reducers and bacteria which utilized simple sugars for their sole carbon source are predominated in the rhizosphere of intensively cultivated upland crops. 3. Alkaligenetic bacteria predominate in rhizosphere of garlic and tomato cultivated upland soils. 4. Genera of Pseudomonas, Xanthomonas, Bacillus, Arthrobacter, and Achromobacterium are the most common species in the rhizosphere of intensively cultivated upland crops and flower plants. 5. Phytotoxin producers such as Stachybotris sp. were identified in all rhizospheres of intensively cultivated upland crops and flower plants. 6. Most common and highest population of soil fungi were obtained for the genera of Penicillium, Humicola, Phoma and Aspergillus in the rhizosphere of intensively cultivated upland crops and flower plants.

• Korean Journal of Soil Science and Fertilizer
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• v.29 no.3
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• pp.297-302
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• 1996

The effect of application rate of pig or chicken manure on the seasonal change of tomato(Minicarol) rhizosphere microflora was investigated by field experiment were surface soil(16cm) mixed with manures 1 weeks before transplanting. 1. Rhizobacteria population of control plot decreased 5 weeks after transplanting(WAT) than 1 WAT and 1.5~2 times higher colony counting was found in DNB(Diluted nutrient broth medium) than NB(Nutrient broth medium) at 15 WAT. 2. Rhizobacteria population at 1 WAT inereased in NB medium with the application rate of both manures but decreased in DNB with chicken manure. Colony counting in NB of 60 and 120 mg/ha treatment was 100 times higher than that of the control. However, rhizobacteria in DNB at 15 WAT(harvest stage) was much higher than that of NB. 3. Application rate did not affect fungi population 1 WAT in pig manure but decresed in chicken manure. At 15 WAT fungi population was 2 times higher than 1 WAT with chieken manure and highest in 30 mg/ha but with pig manure decreased with rate than the control. 4. Actinomycetes population at 1WAT was not different among pig manure rates and decreased with chicken manure than control. At 15 WAT population increased in all manure rates. especially in 10 mg/ha pig manure and 30 mg/ha chicken manure 4 times that 1 WAT.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.3
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• pp.225-233
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• 1991

This study was conducted to evaluate the potential of indigenous vesicular-arbuscular mycorrhizal fungi(VAMF) in the rhizosphere soil of horticultural crops grown under greenhouse and open-field condition, in the southern area of Kores. Soil samples collected from the rhizosphere of some sellected horticultural crops, such as cucumber, hot pepper, lettuca, tomato and eggplant grown under greenhouse or open-field condition. All tested crops are considered as mycorrhizal plants. The infection rate of horticultural crops investigated ranged from 38% to 70%, hot pepper and eggplant grown under greenhouse condition showed the highest infection being 66.0% and 70.0%, respectively. Spore densities were from 4.8 to 20.0g-1 on dried soil basis. Spore densities of VAMF in the rhizosphere soils under greenhouse condition were higher than that of open-field conditions. The highest distribution of spores in diameter ranged from $75{\mu}m$ to $106{\mu}m$ in the rhizosphere soil of lettuce, cucumber and tomato while those in hot pepper and eggplant ranged from $75{\mu}m$ to $250{\mu}m$. Glomus sp.-type spores predominated in the slightly acid soil(pH 6.3), while Acaulospora sp.-type spores greatly predominated in the very strongly acid field(pH 4.9).