• Journal of Forest and Environmental Science
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• v.34 no.5
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• pp.376-381
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• 2018

For the control of oak wilt caused by Raffaelea quercus-mongolicae, an antifungal microorganism, Streptomyces blastmyceticus, was used as a potential agent. Culture suspension of S. blastmyceticus was injected into Quercus mongolicae in the research forest of Kangwon National University by $ChemJet^{(R)}$ trunk injection and Macro-infusion at root flare injection. $Alamo^{(R)}$ (a.i., propiconazole 14.5%), a fungicide currently used for the control of oak wilt in USA, was also treated by both methods to compare the efficacy. For preventive efficacy, culture suspension of the pathogen was inoculated at 1 month after injection of either agent. Tested trees were cut at 3 months after treatment, stained with 1% Fuchsin acid, and then non-conductive area (NCA) and re-isolation frequency (RIF) of oak wilt fungus were compared among treatments. While NCA was the highest as 47.3% in pathogen only treatment, it was the lowest as 16.0% in sterilized water treatment by Macro-infusion. NCAs of Alamo treatment by Macro-infusion and ChemJet injection were 25.3% and 32.1%, respectively. NCA of S.blastmyceticus treatment by ChemJet injection was 32.3%, similar with Alamo treatment's by ChemJet injection. All treatments by either injection method showed significantly lower NCA compared to the pathogen only treatment. These results indicate that S. blastmyceticus injection shows the preventive efficacy against oak wilt disease by suppressing the growth of pathogen injected. NCA of Macro-infusion injection of sterilized water was lower as 16.0%, compared to 21.3% of ChemJet injection. It means that Macro-infusion is more effective in translocation of sterilized water than ChemJet injection by even distribution. RIF from wood discs of treated trees showed high in pathogen only treatment, but relatively low in S. blastmyceticus treatment. RIF results were correlated with NCA results. From the above results, it was confirmed that S. blastmyceticus showed preventive efficacy against oak wilt disease by ChemJet trunk or Macro-infusion at root flare injection.

• Research in Plant Disease
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• v.14 no.2
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• pp.79-84
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• 2008

A wilt disease on lettuce was observed in 2006 and 2007 in commercial plastic house at main production areas of lettuce in Icheon, Yongin and Goyang of Gyeonggi Province. The disease was characterized by the wilting of lower leaves, accompanied by stunting symptoms of the whole plants. Old affected stems showed the black streak in the vascular system. The pathogen, Fusarium oxysporum f. sp. lactucae was isolated from stems and roots of diseased plants. Isolated pathogen also produced the microconidia and macroconidia with chlamydospores on carnation leaf agar medium. The pathogen easily invaded and made many chlamydospores on the roots of lettuce and also made dark streaking through the vascular in the lettuce stems. The density of Fusarium sp. in the severely diseased field soil was more higher populations than that in the healthy and less diseased field soil. The minimum population of pathogen would be above $10^3$cfu/g soil to induce the Fusarium wilt on lettuce in plastic house. The results of pathogenicity test showed 'Sunpung' and 'Mipungpochap' was high susceptible to Fusarium pathogen isolates while some cultivar 'Mihongjeokchukmyeon' and 'Jinjachukmyeon' showed moderate resistance. Disease development for some lettuce was related to treated temperature, so the symptom was more severe above $25^{\circ}C$. Selection of appropriate lettuce cultivar and planting time should be related for the successful control of Fusarium wilt.

• Research in Plant Disease
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• v.26 no.1
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• pp.29-37
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• 2020

Stem blight symptom of soybean was severely developed in 2016 in Hwaseong and Yeoncheon. During the seedling period, the damping-off of seedlings and the brown or black spots of cotyledons were observed. After August, the leaves began to be yellowed, and partially browned areas on leaves began to develop. After September, microsclerotia began to form even on the surface of the stems that had exhibited water-soaking symptom. After mid-October of the harvest season, the epidermis of the stem was peeled off, resulting in the formation of a large number of microsclerotia in the cortex. The pathogens isolated from these symptoms were the best in mycelial growth at 32-35℃, and the formation of microsclerotia was the most at 20-28℃. The pathogen was identified as Macrophomina phaseolina through the morphological characteristics of the pathogen and the sequencing of the internal transcribed spacer region gene. In addition, when inoculated with a soybean stem using toothpicks cultured with the pathogen, the same symptoms as seen on the soybean field occurred. When the pathogen was re-isolated at the lesion site, the same pathogen was isolated and identified as Macrophomina phaseolina. Based on the results, the disease is reported as soybean charcoal rot.

• The Korean Journal of Mycology
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• v.40 no.2
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• pp.118-123
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• 2012

In order to develop environment friendly fungicide for the control of citrus green mold (Penicillium digitatum) using endophytic bacteria, the 21 bacterial isolates were isolated from citrus leaves in seven different orchards in Jeju Province. Among the 21 bacterial isolates, 5 bacterial isolates presented antifungal activity against green mold pathogen P. digitatum. The CB3 isolate, which showed the most strong antagonistic effect, was selected through opposite culture against the pathogen. The rod-shaped, gram-positive bacterium CB3 was identified as Bacillus velezensis based on morphological, physiological characteristics, 16S rDNA, and gyr A gene sequence analysis. The isolate CB3 showed strong antifungal activity against two citrus postharvest pathogen P. digitatum. Citrus fruits were treated by wound inoculation with P. digitatum pathogen, and the control efficacy of CB3 culture broth was 66.7% ($1{\times}10^8$ cfu/ml). In conclusion, The stability of CB3 and its strong antifungal activity also lead us to believe that it has potential for application as an environment friendly biological control agent.

• Korean Journal of Veterinary Service
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• v.39 no.3
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• pp.187-192
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• 2016

Diarrhea is reported as one of the most common diseases in calves. It is thought to be a major cause of productivity and economic loss to cattle producers. The aim of this study is to provide a better understanding of well-known diarrheagenic pathogens and incidence of diarrhea in Korean calves. In this study, the relationship of calf diarrhea and pathogens were investigated from calves under 60 days of age in five areas of Korea from April to July, 2016. Of examined fecal samples, 38.3% was positive for any pathogens, and Giardia was the most common pathogen (25.5%). The incidence of diarrhea was 31% from pathogen-negative fecal samples whereas 61.1% from pathogen-positive fecal samples, suggesting high correlation between pathogenic factor and diarrhea. In addition, 80% of E. coli (K99) positive calves showed diarrhea, suggesting E. coli (K99) could be highly pathogenic. The incidence of diarrhea and infection rate increased with age. Rotavirus was revealed as a major pathogen in calves under 20 days of age, and the infection rate of Giardia increased rapidly in calves 20 to 39 days of age. The information on interconnections between clinical diarrhea and pathogens would contribute to developing strategies for treatment of calf diarrhea.

• Weed & Turfgrass Science
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• v.6 no.2
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• pp.151-156
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• 2017

Summer patch is the most serious disease at turfgrass field or golf course established with Kentucky bluegrass during high temperature season in Korea. Nevertheless, chemicals for the summer patch control are not yet registered in Korea. We isolated the pathogens from the turfgrass showing typical summer patch symptoms and identified as Magnaporthiopsis poae by using the internal transcribed spacer ITS1 and ITS4 sequences of rDNA. The inhibition rates of the pathogen were investigated for 10 fungicides. As results, the pathogen growth was suppressed when chemicals concentration increased and negatively correlated with incubation period with the chemicals. In triazole group, all chemicals (metconazole, myclobutanil, propiconazole and tebuconazole) treated showed the inhibition rates by 100%. Thiophanate-methyl showed the next highest inhibition effect against a summer patch pathogen. In strobilurin group, pyraclostrobin was the highest suppression effect compared with azoxystrobin and trifloxystrobin. Inhibition effect of fludioxonil and fluxapyroxad on pathogen was similar to the trifloxystrobin. Based on the results, triazole and carboxamide groups are strongly recommended due to the highest inhibition effect on the summer patch pathogen, Magnaporthiopsis poae.

• Journal of Plant Biotechnology
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• v.33 no.2
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• pp.93-97
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• 2006

The calmodulin as a Ca$^{2+}$-binding protein mediates cellular Ca$^{2+}$ signals in response to a wide array of stimuli in higher eukaryotes. Plants produce numerous calmodulin isoforms that exhibit differential gene expression patterns and sense different Ca$^{2+}$ signals. SCaM-5 is a soybean calmodulin that is involved in plant defense signaling. Here, we constructed a SCaM-5 CDNA under control of CaMV 35S promoter and transformed it into tomato (Lycopersicon esculentum). The constitutive over-expression of SCaM-5 in tomato plants exhibited a high levels of pathogenesis-related (PR) gene expression, and conferred an enhanced resistance to two fungal pathogen (Phytophthora capsici, Fusarium oxysporum), and a bacterial pathogen, Pseudomonas syringae pv. tomato DC3000. Thus, this results collectively suggest that SCaM-5 plays an important role in plant defense of tomato.

• Molecules and Cells
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• v.27 no.4
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• pp.475-480
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• 2009

The transcription of soybean (Glycine max) calmodulin isoform-4 (GmCaM-4) is dramatically induced within 0.5 h of exposure to pathogen or NaCl. Core cis-acting elements that regulate the expression of the GmCaM-4 gene in response to pathogen and salt stress were previously identified, between -1,207 and -1,128 bp, and between -858 and -728 bp, in the GmCaM-4 promoter. Here, we characterized the properties of the DNA-binding complexes that form at the two core cis-acting elements of the GmCaM-4 promoter in pathogen-treated nuclear extracts. We generated GUS reporter constructs harboring various deletions of approximately 1.3-kb GmCaM-4 promoter, and analyzed GUS expression in tobacco plants transformed with these constructs. The GUS expression analysis suggested that the two previously identified core regions are involved in inducing GmCaM-4 expression in the heterologous system. Finally, a transient expression assay of Arabidopsis protoplasts showed that the GmCaM-4 promoter produced greater levels of GUS activity than did the CaMV35S promoter after pathogen or NaCl treatments, suggesting that the GmCaM-4 promoter may be useful in the production of conditional gene expression systems.

• Current Research on Agriculture and Life Sciences
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• v.32 no.3
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• pp.111-117
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• 2014

Phytophthora blight caused by Phytophthora capsici Leonian is a dangerous disease threatening pepper growers worldwide. The efficacy of chemical control is generally low as the pathogen is soil-borne and rapidly spread by zoospores during the rainy season. Thus, based on the demand for resistant varieties, various good resistant sources, such as CM334, AC2258, and PI201234, have been reported and their inheritance of resistance studied by many different authorities. However, the mode of inheritance remains unclear, as 1 or 2 independent dominant genes, 3 genes, or multiple genes have all been reported as responsible for resistance. Recently, QTL mappings of the gene factors for resistance have been reported, and molecular markers for resistance used in breeding programs. With the release of many resistant commercial hybrid cultivars, differentiation of pathotypes of the pathogen is attracting interest among breeders and plant pathologists. Various authorities have already classified the pathogen strains into different races according to the inter-action between resistant host plants, including the source of resistance, such as CM334 and PI201234, and resistant commercial varieties and P. capsici isolates. However, no standard differential host sets have yet been established, so the results are good only for the pathogen strains used in the experiments. Thus, for breeding varieties with durable resist-ance, it is important to introduce resistance from different sources and use diverse local pathogen strains collected in the target area for distribution in a breeding program.

• Research in Plant Disease
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• v.29 no.1
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• pp.11-22
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• 2023

Resazurin-based microtiter assay was used to evaluate the inhibitory effect of fungicides on the respiration of Colletotrichum acutatum s. lat. 20JDS8 sensitive and 20CDJ6 resistant to strobilurin fungicides. The spores of C. acutatum s. lat. 20JDS8 were inoculated into potato dextrose broth (PDB) at densities of 1x10⁴, 1x10⁵ and 1x10⁶ spores/ml, respectively. The relative fluorescence unit (RFU) of all treatments inoculated at each spore density started to rise after 12 hr of incubation, and were 1,965.5, 5,412.5, and 10,061.0, respectively, after 24 hr of incubation. To evaluate the inhibitory effect of fungicide on the respiration of the pathogen, the spores of the pathogen were inoculated into the PDB and treated with the fungicides 0, 6, 12, and 24 hr after incubation, respectively. After keeping the pathogen culturing for another 24 hr, PrestoBlue reagent was treated into the PDB culturing the pathogen. The RFU of each treatment was examined 1 hr after the reagent was treated. When dithianon, isopyrazam, pyraclostrobin, and fluazinam were treated at high concentrations in the stages of spores (immediately after inoculation [0 hr]), spore germination (after incubation for 6 hr), and hyphal growth (after incubation for 12 hr), the respiration of pathogens was inhibited by 90-100%. When the fungicides were treated after culturing the pathogen for 24 hr, the respiratory inhibitory effects were greatly reduced. With pyraclostrobin-resistant C. acutatum s. lat. 20CDJ6, azxoystrobin, trifloxystrobin and kresoxim-methyl, which have the same mode of action, had very little or no respiratory inhibitory effect in all growth stages of pathogens. Based on the above results, it was thought that the resazurin-based microtiter assay could quickly and accurately evaluate the inhibitory efficacy of the fungicides that inhibited respiration.