• Research in Plant Disease
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• v.21 no.1
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• pp.20-23
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• 2015

A sequential planting method was developed to screen rice plants with durable resistance against rice blast in a short time, and applied for several years in Korean rice breeding program. In this study, we showed the advantages of a sequential planting method compared to other pathogenicity tests. The correlation analysis among three pathogenicity tests and other factors demonstrated that durable resistance depended on the average of diseased leaf area and the number of compatible pathogens. Significant correlations were found in the nursery test but not in the field test result. In addition, we traced changes in the pathogen population during sequential planting stages through re-isolation of the pathogen. The portion of compatible pathogens was increased during sequential planting. Through this study, we provide an effective sequential planting method and direction of durable resistance in a breeding program.

• Research in Plant Disease
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• v.21 no.4
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• pp.261-267
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• 2015

During the period from 2013 to 2014, disease occurrences by various pathogens in apple cultivars have been investigated in northern Gyeongbuk province of Korea. Anthracnose, white rot, Alternaria leaf spot, Marssonina blotch, and bacterial shoot blight as major diseases have been observed. Pathogens isolated from the symptomatic plants were identified as Colletotrichum gloeosporioides for anthracnose, Botryosphaeria dothidea for white rot, Alternaria alternata for Alternaria leaf spot, Marssonina mali for Marssonina blotch, and Pseudomonas syringae pv. syringae for bacterial shoot blight. Of all diseases, the bacterial shoot blight has been severely increased in chronically infested fields in Gyeongbuk province.

• Applied Biological Chemistry
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• v.39 no.1
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• pp.20-24
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• 1996

Pseudomonas fluorescens ps88 was isolated from the rhizosphere soil produced the secondary metabolite called siderophore under iron Limited conditions. On iron limiting KMB medium this strain inhibited the growth of Pythium ultimum, Pyricularia oryzae, Rhizoctonia solani and Xanthomonas oryzae. Cucumber seeds were coated with the strain ps88 and were grown in green house soil. Forty days after the seed emergence, disease incidence caused by Fusarium oxysporium was reduced up to 50%. When the cucumber plants were grown in vermiculite, a significant fresh weight was increased. Root development of red pepper plants was also enhanced on MS medium supplemented with siderophore.

• Journal of Microbiology and Biotechnology
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• v.27 no.6
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• pp.1157-1162
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• 2017

The goal of this study was to identify and characterize selected Trichoderma isolates by metabolic profiling and enzyme assay for evaluation of their potential as biocontrol agents against plant pathogens. Trichoderma isolates were obtained from the Rural Development Administration Genebank Information Center (Wanju, Republic of Korea). Eleven Trichoderma isolates were re-identified using ribosomal DNA internal transcribed spacer (ITS) regions. ITS sequence results showed new identification of Trichoderma isolates. In addition, metabolic profiling of the ethyl acetate extracts of the liquid cultures of five Trichoderma isolates that showed the best anti-Phytophthora activities was conducted using gas chromatography-mass spectrometry. Metabolic profiling revealed that Trichoderma isolates shared common metabolites with well-known antifungal activities. Enzyme assays indicated strong cell wall-degrading enzyme activities of Trichoderma isolates. Overall, our results indicated that the selected Trichoderma isolates have great potential for use as biocontrol agents against plant pathogens.

• Research in Plant Disease
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• v.26 no.1
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• pp.57-60
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• 2020

Citrus scab symptoms were observed on leaves of trifoliate orange (Poncirus trifoliata) in open field of Citrus Research Institute, National Institute of Horticultural and Herbal Science. Typical scab pustules were formed and they were elevated protuberances form and light brown to grey. The pathogens were isolated from the symptomatic leaves and then were identified to Elsinoë fawcettii by morphological characteristics, pathogenicity and PCR assay. The morphological characteristics of colonies formed very slow-growing, pulvinate, or raised and deeply fissured, gummy to mucoid or tomentose colonies on potato dextrose agar medium. The pathogens were pathogenic to leaves of Satsuma mandarin, lemon, sour orange and grapefruit with typical scab symptoms. In PCR assay, specific amplified of products of 717 bp with Efaw-1 and 384 bp with Efaw-2 were observed from trifoliate isolates and E. fawcettii as reference but not from E. australis. This is first report of trifoliate orange being positive for citrus scab disease.

• The Plant Pathology Journal
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• v.31 no.2
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• pp.115-122
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• 2015

Anthracnose, caused by Colletotrichum gloeosporioides (C. gloeosporioides; Teleomorph: Glomerella cingulata), is the most destructive disease that affects sweet persimmon production worldwide. However, the biology, ecology, and genetic variations of C. gloeosporioides remain largely unknown. Therefore, in this study, the development of fungicide resistance and genetic diversity among an anthracnose pathogen population with different geographical origins and the exposure of this population to different cultivation strategies were investigated. A total of 150 pathogen isolates were tested in fungicide sensitivity assays. Five of the tested fungicides suppressed mycelial pathogen growth effectively. However, there were significant differences in the sensitivities exhibited by the pathogen isolates examined. Interestingly, the isolates obtained from practical management orchards versus organic cultivation orchards showed no differences in sensitivity to the same fungicide. PCR-restriction fragment length polymorphism (RFLP) analyses were performed to detect internal transcribed spacer regions and the ${\beta}$-tubulin and glutamine synthetase genes of the pathogens examined. Both the glutamine synthetase and ${\beta}$-tubulin genes contained a complex set of polymorphisms. Based on these results, the pathogens isolated from organic cultivation orchards were found to have more diversity than the isolates obtained from the practical management orchards.

• Horticultural Science & Technology
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• v.32 no.6
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• pp.901-905
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• 2014

The efficacy of ozone micro-bubble water (OMBW) in reducing microbial populations on alfalfa seeds was investigated in this study. We observed the surface of alfalfa seeds using microscopy and found that many cracks and crevices existing on the surface could harbor pathogens. Alfalfa seeds were treated with tap water (TW), micro-bubble water (MBW), ozone water (OW), ozone micro-bubble water (OMBW), and chlorine water (CL) for 5 min, and total microbial population, E. coli and Salmonella spp. colonies were determined. Also, the sterilized seeds were germinated and cultivated for 5 d after sowing to investigate the percentage of germination and the growth of alfalfa sprouts. The treatments with OMBW and CL were most effective in reducing total microbial populations and E. coli was eliminated by OW, OMBW, and CL treatments. CL treatment reduced the percentage of germination and fresh weight of alfalfa sprouts, but OMBW did not cause any negative effects on the germination and growth of alfalfa sprouts. These results indicate that OMBW can be used as an effective sanitizer for eliminating seed-borne pathogens without detrimental effects on seed viability.

• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.484-490
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• 1998

Microorganisms associated with seed-rhizome rot of gingers preserved in three underground storage caves were identified with respect to rot types. Rot patterns were grouped into 4 different types : yellow soft rot, brown rot, localized ring rot, and water-soaked rot. Water-soaked rot was highest in frequency with 40% and ring rot the least with 14%. Causal pathogens differed with rot type, yellow soft rot by Erwinia carotovora and Pseudomonas aeruginosa, brown rot by Fusarium solani and Pseudomonas aeruginosa, localized ring rot by F. solani, and water-soaked rot by Pythium spinosum and P. ultimum. Pythium myriotylum, the causal pathogen of ginger rhizome rot which occurs severely in fields was rarely detected from storage seed-rhizomes suggesting its minor involvement with storage rot. Pathogenic Pythium isolates were frequently obtained from both rhizome surface and inner tissues of rotten rhizomes. Detection frequency of Pythium isolates in inner tissues decreased as increasing distance from rhizome surface. In wound-inoculation tests, above pathogens caused a varying degree of rot on healthy rhizomes at 15$^{\circ}C$, 2$0^{\circ}C$ and 3$0^{\circ}C$ with increasing severity at higher temperatures.

• Korean Journal of Veterinary Research
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• v.56 no.2
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• pp.91-95
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• 2016

This study was conducted to investigate the prevalence and antimicrobial resistance of Salmonella spp. and Escherichia (E.) coli isolated from ducks in Korea. A total of 400 cecal content samples were collected from 40 duck farms in Korea. Isolated Salmonella spp. and E. coli strains were 83 and 364 of the 400 cecal samples, respectively. The most prevalent serotype among the 83 Salmonella isolates was Salmonella Typhimurium (51 isolates: 61.45%). Resistance to the tested antimicrobial agents by Salmonella isolates was low except for erythromycin, while the resistance of the E. coli isolates to the other tested antimicrobial agents was high and 90.9% (331/364) of E. coli isolates showed multi-antimicrobial resistance. Antimicrobial resistance in duck zoonotic pathogens should be of concern to the Korean duck industry, as these pathogens exhibit a high rate of antimicrobial resistance and pose a potential hazard to public health.

• Mycobiology
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• v.42 no.4
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• pp.376-384
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• 2014

Roselle (Hibiscus sabdariffa L.) is one of the most important medicinal crops in many parts of the world. In this study, the effects of microelements, antioxidants, and bioagents on Fusarium oxysporum, F. solani, and Macrophomina phaseolina, the causal pathogens of root rot and wilt diseases in roselle, were examined under field conditions. Preliminary studies were carried out in vitro in order to select the most effective members to be used in field control trials. Our results showed that microelements (copper and manganese), antioxidants (salicylic acid, ascorbic acid, and EDTA), a fungicide (Dithane M45) and biological control agents (Trichoderma harzianum and Bacillus subtilis) were significantly reduced the linear growth of the causal pathogens. Additionally, application of the previous microelements, antioxidants, a fungicide and biological control agents significantly reduced disease incidence of root rot and wilt diseases under field conditions. Copper, salicylic acid, and T. harzianum showed the best results in this respect. In conclusion, microelements, antioxidants, and biocontrol agents could be used as alternative strategies to fungicides for controlling root rot and wilt diseases in roselle.