• Research in Plant Disease
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• v.8 no.3
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• pp.184-188
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• 2002

An antagonistic bacteria, Bacillus licheniformis Nl strain which effectively inhibited mycelial growth of gray mold rot pathogen, Botrytis cinerea was isolated from the rhizosphere of perilla crop. Powder soy formulation by B. lichentfomis Nl strain as a biocontrol agent was developed far the first time and estimated its control effect on perilla leaves in this study. First of all, far the mass production of antifungal metabolites of B. lichentfomis Nl strain in flask liquid culture, the most effective carbon and nitrogen source were selected as glucose and tryp-tone, respectively, For the formulation, vegetative biomass of B. licheniformis Nl strain from 5-day-old liquid culture in nutrient broth added glucose and tryptone was mixed with soy flour, rice flour glucose, FeSo$_4$~7$H_2O$, and MnCl$_2$. 4$H_2O$, and dried and pulverized. In plastic house test, powder soy formulation effectually controlled gray mold rot as the control value of 93.1 %, was more effective than chemical fungicide, benomyl showing the control value of 86.1%. Thus, development of powder soy formulation of B. lichentfomis Nl will aid large-scale application of biological control in field trials.

• Research in Plant Disease
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• v.10 no.4
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• pp.324-330
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• 2004

This studies were investigated the occurrence of sclerotinia rot at the crisphead lettuce field in Uiryeong-Gun, Gyeongsangnam-Do from January to May in 2003. Average incidence rates of sclerotinia rot on crisphead lettuce was up to 21.9% at the five plastic houses. A total of 140 isolates of Sclerotinia sp. were obtained from diseased leaves of crisphead lettuce. Among them, the fungi YR-1 was isolated, which showed highly virulent on the whole plant. the YR-1 was identified as Sclerotinia sclerotiorum based on the formation, color, shape and size of sclerotium and apothecium. For the pathogenicity test, the most suitable inoculum quantity of YR-1 strain was selected as the triturated mycelial suspension of $A_{550}$=0.8, 40 ml showing disease incidence of 94%, and the symptom showed as same as at the fields, the leaves and stem had rotten and developed white downy mycelial at the diseased lesion on the leaves and stems, and produced black and irregular sclerotinia. This is the first report on the pathogenicity test using by triturated mycelial suspension-inoculum of the pathogen for the sclerotinia rot of crisphead lettuce.

• Research in Plant Disease
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• v.23 no.3
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• pp.228-233
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• 2017

Six commercial rootstock varieties were tested for resistance to bacterial wilt (Ralstonia solanacearum) by dipping the roots of seedlings in the bacterial suspension at seedling stage. 'Shincheonggang' and 'B-Blocking' ranked top and second in resistance to bacterial wilt, respectively. For disease index of the grafted plants, 'Dotaerang' grafted onto 'Shincheonggang' was the least, followed by 'Ultra', 'Fighting', 'B-Blocking', 'Special', and 'Connection' grafts. Thus, disease development on the grafted plants was correlated with resistance of rootstocks. The effect of rootstocks on horticultural characteristics including days to flower of scion was minimum or negligible. In correlation between horticultural characteristics of rootstocks and scions grafted thereon, statistically significant negative correlation was observed in days to flower and fruit height but no significant correlation was observed in yield per plant, fruit diameter and soluble solid content in the fruits. Thus, selection of resistant rootstock varieties that support the growth and yield of scion well is necessary for effective control of the disease and yield increase.

• Research in Plant Disease
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• v.25 no.4
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• pp.220-225
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• 2019

During the year 2018, the symptoms of bunch rot on Shine Muscat (Vitis vinifera L.) were observed in Kimcheon-si, Gyeongbuk province in Korea. The disease appears on the Shine Muscat as a black rot due to prolific fungal sporulation after it has invaded into the Shine Muscat which look completely empty and dryness. Colonies of these fungi are present on the Shine Muscat skin from fruit setting and increase in amount from early season to harvest, while become peak at ripening stage. To isolate the causal agent, small fragments (2 to 3 mm) of decayed tissue from the lesion margin were placed onto potato dextrose agar (PDA) plates. Fungal colonies on PDA produced dense white aerial mycelium and then covered with dark black conidial heads. These heads were large and radiate, and vesicles were globose (2.12-32.0×2.0-3.1 ㎛). Based on morphological and cultural characteristics, this fungus was identified as Aspergillus tubingensis. To confirm its identity, the internal transcribed spacer, β-tubulin, and RNA polymerase II was sequenced for molecular identification. BLAST search indicated 99% identity with A. tubingensis. The pathogenicity test on healthy grape of Shine Muscat produced bunch rot, as the original symptoms. To select effective fungicides for the control of brunch rot, an in vitro antifungal activity of seven fungicides were evaluated against the growth of A. tubingensis. Five fungicides (dipenoconazole, tebuconazole, metconazole, iminoctadine, and captan) exhibited significantly strong suppression of the mycelial growth of A. tubingensis.

• Research in Plant Disease
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• v.26 no.3
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• pp.170-178
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• 2020

Most strawberry viruses exist relatively low titers in tissues, and strawberry tissues include high levels of contamination by polysaccharides and phenolic compounds. These traits make the efficiency of strawberry diagnosis difficult. In this study, we tested different commercially available kits and reagents to secure optimal RNA extraction methods to determine virus detection from strawberry leaves. Total RNA was isolated from leaves of strawberry mottle virus (SMoV)-infected strawberry cultivar 'Mihong'. The efficiency of total RNA for virus diagnosis was confirmed through SMoV detection by one-step or two-step reverse transcription and polymerase chain reaction (RT-PCR). Among those, the RNeasy plant RNA kit was best to isolate RNA and the isolated RNA was good enough for further applications. To ensure a reliable detection for strawberry viruses, synthetic diagnosis clones for major seven strawberry viruses such as strawberry mild yellow edge virus, SMoV, strawberry latent ring spot virus, strawberry crinkle virus, strawberry pallidosis associated virus, strawberry vein banding virus and strawberry necrotic spot virus have been constructed. Based on the synthetic genes in each clone, primer sets for seven strawberry viruses were designed and tested an RT-PCR condition through a simultaneous application of the same annealing temperature that allowed to achieve an efficient and convenient diagnosis.

• Research in Plant Disease
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• v.21 no.1
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• pp.12-19
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• 2015

Antimicrobial activities of nano-materials were tested against several plant pathogens. Twelve different nano-materials were used to observe the antagonistic activity against three kinds of mold and sixteen different kinds of watermelon fruit rot pathogens (Acidovorax citrulli). According to the results, no antagonism have been found against the pathogen, Cylindrocarpon destructans. However in the case of Pythium ultimum, combination of Brass/Glucose 1,000 ppm confirmed the mycelial growth reduction by 94%. In addition, little effect was found against Rhizoctonia solani by Ag/Glucose 3,000 ppm. The remaining other nano-materials have different antimicrobial effect depending on the strains of A. citrulli. But in the case of lime (Cu/Salt 1,000 ppm) highest antimicrobial activity was observed with 97%. Moreover growth of five different strains of A. citrulli was checked by 99% with the combination of Ag/Glucose 1,000 ppm. 92% reduction of A. citrulli growth was observed with $Brass/CaCO_3$ 3,000 ppm. Tested nano-materials against different plant pathogens in this study showed the antimicrobial activity at the range of 24-70%.

• Research in Plant Disease
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• v.18 no.3
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• pp.210-216
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• 2012

Clubroot of Chinese cabbage by Plasmodiophora brassicae, was found to be high virulent to the Chinese cabbage, turnips and cabbage. It this study, the endophytic bacteria Flavobacterium hercynium EPB-C313, which was isolated from tissues of Chinese cabbage, was investigated the antimicrobial activity on the inactivation of resting spores and its control effect on clubroot disease by bioassay. The bacterial cells, culture solutions, and culture filtrates of F. hercynium EPB-C313 inactivate the resting spores of P. brassicae with 90.4, 36.8, and 26.0%, respectively. The clubroot was inhibited with 100% by dipping the seedlings of Chinese cabbage in culture solutions of F. hercynium EPB-C313 before planting, however the chemmical 'fluazinam' was 91.7% in pot tests. Complex treatment were highly enhanced control efficacy with 63.7% at field of 50% diseased plants by soil incorporation with the pellet contains organic matter and F. hercynium EPB-C313, seedling drench of culture solution of F. hercynium EPB-C313 and soil drench with 10 days after planting. These results imply that the F. hercynium EPB-C313 is a very useful biological control agent of clubroot disease of Chinese cabbage.

• Research in Plant Disease
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• v.19 no.4
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• pp.243-253
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• 2013

Rice blast is one of the most serious disease threatening stable production of rice. Breeding of resistant cultivars has been used as the most effective and useful method to controll rice blast caused by Magnaporthe oryzae. To collect rice blast isolates in fields and test their pathogenicity on new cultivars are important for establishment of new resistant cultivars breeding program of rice. Pathotypes of Korean rice blast isolates have been categorized to Korean differential race system developed in 1985. However, it is little known about genetic background of Korean differential cultivars, so that it is hard to understand for relationship between each pathogen and each host plant at genetic level. In this study, we suggested necessity of a new differential system by analyzing pathogenic responses between 24 monogenic rice lines and 200 Korean rice blast isolates. In addition, we determined the nine representative resistant genes based on the resistance responses of the monogenic lines to rice blast isolates, indexed resistant responses of the monogenic lines to ten representative rice blast isolates and selected 30 Korean representative rice blast isolates proper to Korean system. We think the newly developed differential race system can be broadly used to select resistant cultivars to rice blast in Korea.

• Korean Journal Plant Pathology
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• v.3 no.4
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• pp.291-298
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• 1987

Samples showing mosaic symptom of cowpea (Vigna sesquipedalis) with vein banding, chlorotic spot, vein yellow were collected from Chinju areas in Korea, Two viruses were distinguishable by stability in sap, host range, and relations with cells and tissues were examined under an electron microscope, Blackeye cowpea mosaic(BICMV) was sap-transmissible to 7 plant species in 2 families, Of the plants, only leguminous species were systemically infected. This virus was inactivated by heating at $50-65^{\circ}C$ for 10 min, by diluting at $10^{-4}-10^{-5}$, and aging at room temperature for 1-6 days. Preparations examined under the electron microscope by direct negative staining method(DN -method) always showed particles of flexuous filament bout 750nm in length and cytopasmic inclusions. Cytoplasmic inclusions and virus particles were also confirmed to present in the cytoplasm of a mesophyll cell by ultrathin sections of BICMV infected cowpea leaves. Cucumber mosaic virus (CMV) was transmitted by sap- inoculation on inoculated leaves of Chenopodium amaranticolor, C. quinoa producing local lesions, but non-inoculated upper leaves of Nicotiana glutinosa, Cucurbita pepo and Vigna sesquipedalis producting systemic mosaic symptoms. Electron microscopic examination of virus preparation by direct negative staining showed spherical particles of about 30nm in diameter. In ultrathin sections of CMV infected tissues, virus particles of crystalline array were found in the vacuole and a large number of virus particles were found in the cytoplasm and the plasmodesmata of mesophyll cells.

• Research in Plant Disease
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• v.13 no.3
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• pp.177-182
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• 2007

In this experiment, 236 isolates of Botrytis cinerea isolated from the lesions of ginseng grey mold in 2005 and 2006 were examined for their sensitivity to fungicide inhibiting ${\beta}-tubulin$ assembly. The baselines of fungicide resistance were determined as 10.0 and $0.2{\mu}g/ml$ of $EC_{50}$ values for carbendazim and the mixture of carbendazim and diethofencarb, respectively. The ratios of isolates resistant to carbendazim in 2005 and 2006 was investigated to be 87.6 and 96.6%, respectively. In the case of the mixture of carbendazim and diethofencarb, the ratio of the resistant isolates was 23.6% for 2005 and 24.5% for 2006. The ratio of the resistant isolates to the mixed fungicide was fluctuated according to regions where isolates of B. cinerea were obtained. In Yeoncheon of Gyeonggi Province, 4.3% of the isolates used in the experiment was resistant in 2005 and no resistant isolate was obtained in 2006. Among 5 regions, the ratio of resistant isolates was the highest as 70.0% in Yecheon of Gyeongbuk Province.