• Research in Plant Disease
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• v.13 no.2
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• pp.104-109
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• 2007

Pink root disease of onion, a known worldwide constraint upon onion production, significantly reduces crop levels in the main Korea cultivation area. In order to examine the effect of flooding on incidence of pink root disease caused by Pyrenochaeta terrestris and on onion growth and on populations of soil fungi, field experiments were conducted during two seasons, 2003/04 and 2004/05 at Onion Research Institute. Populations of soil fungi from fields were assayed on selective media. Flooding treatment was effective in reducing populations of P. terrestris, Pythium spp., and Rhizoctonia sp. in soil; fungal populations in soils flooded for 90 days were reduced to 1/2 to 1/3 of those in non-flooded soils. In nursery bed, protective activities of soils flooded for over 60 days were 93.5 to 99.2% and their pink root incidences were less than 5%, which were 1/11 to 1/18 of that in control. Increased yield of onion bulbs was associated with control of soil borne pathogenic fungi by flooding treatments. As flooding period was prolonged, bulb grade showed the tendency to increase. Soil flooding for over 60 days resulted in effective disease control, facilitated accurate planning of plant population in the field, extension of the growing-season and consequently higher yields of better quality.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2004.10a
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• pp.62-65
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• 2004

To protect the watermelon against soil-borne pathogens, we are currently producing disease-resistant transgenic root stock for the growth of watermelon, A defensin gene (J1-1) from Capsicum annum, a ACC deaminase gene from Pseudomonas syringae, a galactinol synthase (CsGolS) gene from Cucumis sativus, and a WRKY (CvWRKY2) gene from Citullus vulgaris were used as transgenes for disease resistance. The gene were transformed into a inbred line (6-2-2) of watermelon, Kong-dae watermelon and a inbred line (GO702S) of gourd, respectively, by Agrobacterium-mediated transformation. Putative transgenic plants were selected in medium containing 100mg/L kanamycin, and then integration of the genes into the genomic DNA were demonstrated by PCR analysis. Successful integration of the gene in regenerated plants was also confirmed by PCR (Figf 1), genomic Southern blot (Fig 2), RT-PCR (Fig 3), and Northern blot analysis(Fig 4). Several T1 lines having different transgene were produced, and disease resistance of the T1 lines are under estimation.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.252-257
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• 1995

Growth rates of the low temperature growing isolates, Pseudomonas fluorescens M45 and MC07, reached maximum stationary phase within 50 hrs at the low temperature, 4$^{\circ}C$. But an ordinary biocontrol agent P. putida Pf3 did not reach logarithmic growth phase until 80 hrs. The culture filtrates of M45 and MC07 significantly inhibited the mycelial growths of Pythium ultimum, Rhizoctonia solani and Phytophthora capsici. Detached cotyledons of cucumber grown on Murashige and Skoog agar medium were much enhanced in their growth, compared to those without the filtrates. Population densities of M45 and MC07 in the rhizosphere at 14$^{\circ}C$ were more stable than at 27$^{\circ}C$. When M45 and MC07 were treated into soil, the population density of MC07 continuously increased up to 9 days after treatment, and sustained the initial inoculum density up to 60 days. Cucumber damping-offs caused by P. ultimum and R. solani were significantly reduced by applying M45 as seed-inoculant and by soil treatment with MC07. The combined treatment of M45 and MC07 provided greater effect in reducing the disease incidence than that obtained by single treatments.

• Korean Journal of Soil Science and Fertilizer
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• v.51 no.1
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• pp.28-34
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• 2018

Yuzu (Citrus junos) gummosis disease, caused by Phytophthora nicotianae, was first reported in 1997. As known in citrus, Phytophthora is the most fastidious soil-borne pathogen to control. In order to minimize its damage to Citrus spp., integrated pest management (IPM) approach, including fungicide chemicals and resistant cultivars, is necessary. Therefore, in this study we tried to evaluate tolerance of yuzu cultivars and its related species against yuzu Phytophthora. Trifoliate orange was evaluated as a susceptible host to yuzu Phytophthora by both mycelial growth onto extract media and immature fruit inoculation. However, in zoospores spray-inoculation on 2-year-old cuttings tree, trifoliate orange appeared to have a resistant property as showing less than 6% diseased leaf rate. Among yuzu cultivars only 'Namhae No. 1' appeared resistant property against both P. nicotianae and P. citrophthora. The 'Namhae No. 1' showed 5.7% and 10.6% diseased leaf ratio by P. nicotianae and P. citrophthora, respectively. Clearly, in order to reduce damages caused by two yuzu Phytophthora, we suggest that growers may utilize a trifoliate orange as a rootstock and 'Namhae No. 1' as a scion for fruit production.

• Research in Plant Disease
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• v.22 no.2
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• pp.100-106
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• 2016

We have studied the mycelia growth of four soil-borne fungal pathogens under light qualities and two lighting types (continuous and intermittent) provided by light-emitting diodes (LEDs). As a result, each mycelia growth on Phytophthora cactorum KACC40166, Athelia rolfsii KACC40170, and Helicobasidium mompa KACC40836 strain showed the similar growth rates within 10% or less difference among treatments compared to dark control, regardless of lighting types. However, the mycelia growth on Rosellinia necatrix KACC40168 strain was significantly suppressed by blue, blue+green and blue+red LED as well as fluorescent lamp compared to a dark control, in common with lighting types. The melanin pigment on R. necatrix KACC40168 strain showed relatively to induce more strongly under green LED and fluorescent lamp, whereas no induction under red LED and a control, regardless of lighting types. Thus, the hypha width on R. necatrix KACC40168 was significantly thinned by blue and blue+green LED compared to a control, in common with lighting types.

• Korean journal of applied entomology
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• v.24 no.2 s.63
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• pp.107-114
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• 1985

This experiment was performed to see the possibility if soil-borne disease in green house can be controlled by soil solarization in Korea. Thermal death profiles of propagules of some soil-borne fungi, Fusarium oxysporum f. lycopersici, Fusarium oxysporum f. niveum, Rhizoctonia salani, Sclerotinia sclerotiorum, Sclerotium rolfsii and Pythium debaryanum, were obtained under the conditions in water-suspension and in soil. Except Pythium debaryanum, all the fungal units in water-suspension that were colonized on barley grains lost a viability within 7 days in water bath at $45^{\circ}C$. When the soil in test tubes in which barley grains infected with the fungi were also buried all the fungi tested including Pythium debaryanum were completely killed within 7 days in water bath at $45^{\circ}C$. From July to August in Korea, soil temperature at depth of 5cm and 15cm within tunnel in plastic house reached $38^{\circ}C\;to\;57^{\circ}C$ and $40^{\circ}C\;to\;47^{\circ}\C$, in 1982 and 1983 respectively. Even at 15cm depth, soil temperature were kept over $43^{\circ}C$ for 12 hours a day. Adiabatic material set under ground or under mulching with the transparent polyethylene-film on the soil surface had a boostering effect for higher soil-temperature and longer duration. Fungi buried in adiabatic block of the soil in plastic house were completely killed at 15cm depth 14 days after, and at 20cm depth 21 days after soil solarization. The exposure of the pathogens to fluctuating temperature was much more effective than to constant. From the above results, soil-borne diseases may be effectively controlled by soil solarization in the closed plastic house in hot summer season in Korea.

• Journal of The Korean Society of Grassland and Forage Science
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• v.15 no.1
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• pp.1-12
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• 1995

This study was to investigate an effective biological control of forage diseases and provide a basic data and a model in improving variety of antagonistic bacteria, with growth promoting effect on forage, through cell fusion. The results obtained were summarized as follows; 1. The antagonistic himbacterium against soil-borne phathogenic fungi Fusarium oxysporum and Rhizoctonia solani was isolated from continuous cropping himsphere soil of forage, and its biological and physiological characteristics were investigated. This bacterium was identified as Bacillus subrilis and named BS 101. Another strain for cell fusion was Bacillus thur ingiensis ssp. kurstaki HD-I(BT 37669) with insecticidal crystal. 2. The auxotropic mutants of BS 101 and BT 37669 were derived after mutagenesis using N-methyl-N'nitro- Nitrosoguanidine(NTG) to give amino acid requirement marker. n e s e auxotropic mutants of BS 101 and BT 37669 were named BS 1013(his-) and BT 69(asp-), respectively. 3. The best protoplast requirement was obtained using DM 3 medium, containing 5% casamino acid, 1 M $MgCI_2$ and 2% bovine semm albumin, to give Fusant 3, 7 and 8. BT toxin gene was not identified with fusants by Southern blotting. However, SDS-PAGE analysis of strains showed various protein patterns among fusants. 4. From the dark culture experiment, growth of forage in inoculated soil with antagonistic bacteria was delayed than that of non-inoculated soil with antagonistic bacteria in each continuous cropping soil and in each sterilized soil. On the other hand, growth duration of forage was different between continuous cropping soil and sterilized soil. 5. Seed germination of Alfalfa, Italian ryegrass and Orchardgrass were significantly improved by inoculation of antagonistic bacteria(p< 0.05).

• Research in Plant Disease
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• v.22 no.3
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• pp.198-201
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• 2016

Recently, severe dieback of apple tree has occurred in the apple orchards of Chungbuk province. Dieback rate and its casual agents have been investigated on the Chungbuk province apple orchards in 2013-2015. Out of 29,265 apple trees in the 27 orchards throughout Chungbuk province, 4,000 apple trees (13.7%) showed dieback symptoms. The causes of dieback were Phytophthora rot (50.4%), violet root rot by Helicobasidium sp. (27.1%), rodents (10%), white root rot by Rosellinia sp. (6.3%), and freezing injury (6.3%). Compared to previous reports published in 1995 and 2006, Phytophthora rot was the most dominant disease, which is thought to be due to high temperature during growing season and the increase of lowland cultivation. Results of this study will be useful to establish of the management strategy of apple tree dieback that has been increased recently.

• The Plant Pathology Journal
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• v.29 no.2
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• pp.125-135
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• 2013

In agro-ecosystems worldwide, some of the most important and devastating diseases are caused by soil-borne necrotrophic fungal pathogens, against which crop plants generally lack genetic resistance. However, plants have evolved approaches to protect themselves against pathogens by stimulating and supporting specific groups of beneficial microorganisms that have the ability to protect either by direct inhibition of the pathogen or by inducing resistance mechanisms in the plant. One of the best examples of protection of plant roots by antagonistic microbes occurs in soils that are suppressive to take-all disease of wheat. Take-all, caused by Gaeumannomyces graminis var. tritici, is the most economically important root disease of wheat worldwide. Take-all decline (TAD) is the spontaneous decline in incidence and severity of disease after a severe outbreak of take-all during continuous wheat or barley monoculture. TAD occurs worldwide, and in the United States and The Netherlands it results from a build-up of populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent Pseudomonas spp. during wheat monoculture. The antibiotic 2,4-DAPG has a broad spectrum of activity and is especially active against the take-all pathogen. Based on genotype analysis by repetitive sequence-based-PCR analysis and restriction fragment length polymorphism of phlD, a key 2,4-DAPG biosynthesis gene, at least 22 genotypes of 2,4-DAPG producing fluorescent Pseudomonas spp. have been described worldwide. In this review, we provide an overview of G. graminis var. tritici, the take-all disease, Pseudomonas biocontrol agents, and mechanism of disease suppression.

• Microbiology and Biotechnology Letters
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• v.46 no.4
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• pp.346-359
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• 2018

Xanthomonas oryzae, a bacterial pathogen causing leaf blight disease (BLB) in rice, can cause widespread disease and has caused epidemics globally, resulting in severe crop losses of 50% in Asia. The pathogen is seed-borne and is transmitted through seeds. Thus, control of BLB requires the elimination of the pathogen from seeds. Concern about environment-friendly organic production has spurred improvements in a variety of biological disease control methods, including the use of bacteriophages, against bacterial plant pathogens. The present study explored the potential of bacteriophages isolated from diseased plant leaves and soil samples in killing the bacterial pathogen in rice seeds. Eight different phages were isolated and evaluated for their bacteriolytic activity against different pathogenic X. oryzae strains. Of these, a phage designated ${\varphi}XOF4$ killed all the pathogenic X. oryzae strains and showed the broadest host range. Transmission electron microscopy of ${\varphi}XOF4$ revealed it to be a tailed phage with an icosahedral head. The virus was assigned to the family Siphoviridae, order Caudovirales. Seedlings raised from the seeds treated with $1{\times}10^8pfu/ml$ of ${\varphi}XOF4$ phage displayed reduced incidence of BLB disease and complete bacterial growth inhibition. The findings indicate the potential of the ${\varphi}XOF4$ phage as a potential biological control agent against BLB disease in rice.