• The Plant Pathology Journal
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• v.33 no.3
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• pp.238-248
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• 2017

Pokkah Boeng is a serious disease of sugarcane, which can lead to devastating yield losses in crop-producing regions, including southern China. However, there is still uncertainty about the causal agent of the disease. Our aim was to isolate and characterize the pathogen through morphological, physiological, and molecular analyses. We isolated sugarcane-colonizing fungi in Fujian, China. Isolated fungi were first assessed for their cell wall degrading enzyme capabilities, and five isolates were identified for further analysis. Internal transcribed spacer sequencing revealed that these five strains are Fusarium, Alternaria, Phoma, Phomopsis, and Epicoccum. The Fusarium isolate was further identified as F. verticillioides after Calmodulin and EF-$1{\alpha}$ gene sequencing and microscopic morphology study. Pathogenicity assay confirmed that F. verticillioides was directly responsible for disease on sugarcane. Co-inoculation of F. verticillioides with other isolated fungi did not lead to a significant difference in disease severity, refuting the idea that other cellulolytic fungi can increase disease severity as an endophyte. This is the first report characterizing pathogenic F. verticillioides on sugarcane in southern China.

• Mycobiology
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• v.31 no.3
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• pp.179-182
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• 2003

A total of 187 endophytic fungi were isolated from 11 plant species, which were collected from 11 locations in Korea. Their antifungal activities were screened in vivo by antifungal bioassays after they were cultured in potato dextrose broth and rice solid media. Antifungal activity against plant pathogenic fungi such as Magnaporthe grisea(rice blast), Corticium sasaki(rice sheath blight), Botrytis cinerea(tomato gray mold), Phytophthora infestans(tomato late blight), Puccinia recondita(wheat leaf rust), and Blumeria graminis f. sp. hordei(barley powdery mildew) was determined in vivo by observing the inhibition of plant disease development. Twenty(11.7%) endophytic fungi fermentation broths were able to control, by more than 90%, at least one of the six plant diseases tested. Among 187 liquid broths, the F0010 strain isolated from Abies holophylla had the most potent disease control activity; it showed control values of more than 90% against five plant diseases, except for tomato late blight. On the other hand, fourteen(7.5%) solid culture extracts exhibited potent disease control values of more than 90% against one of six plant diseases. The screening results of this study strongly suggested that metabolites of plant endophytic fungi could be good potential sources for screening programs of bioactive natural products.

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.1
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• pp.31-40
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• 1999

This study was conducted to investigate the effects of rhizosphere bacterium and pathogenic fungi on the growth of corn(Zea may L.) in continuous corn cultivation soil(CCCS) and non-continuous cultivation soil(NCCS). Corn was established by seeding into pots of 30 cm in diameter and 50 cm in depth containing 1 : 1 mixture of soil and vermiculite. Rhizobacterium and pathogenic fungi were inoculated into the soils. The field experiment was carried out at the Animal Research Station, College of Agriculture, Chonnam National University. Sample of corn was taken from each pot at 50 days and 90 days after sowing. Corn was cultivated in a vinyl house with three replications under natural daylight conditions. The bacterium used in this study was Bacillus subtilis. B. subtilis was directly isolated and identified from forage rhizosphere soil. Dry matter(DM) of coron plant in treatment without B. subtilis was lower than that in treatment of B. subtilis. DM of corn plant inoculated with B. subtilis was higher than that of corn inoculated with pathogenic fungi in both CCCS and NCCS. DM of corn plant in NCCS was more increased than that in CCCS. The effect of B. subtilis inoculation on the growth of corn was better in NCCS than in CCCS. However, DM of corn plant was apparently decreased by the inoculation of the pathogenic fungi in both CCCS and NCCS.

• Korean Journal of Microbiology
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• v.52 no.4
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• pp.437-443
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• 2016

In this study Streptomyces strains were isolated from soils and their antifungal activities and involved mechanisms were investigated. Among over 400 isolates of actinomycetes, Streptomyces costaricanus HR391 was selected as a potential antagonist to control several plant-pathogenic fungi. S. costaricanus HR391 inhibited mycelial growth of Fusarium oxysporum f. sp. raphani, F. oxysporum f. sp. niveum, F. oxysporum f. sp. lycopersici, and Rhizoctonia solani by 26.5, 26.2, 21.2, and 23.8%, respectively compared to those of uninoculated control after 7-day incubation on PDB medium. S. costaricanus HR391 produced $89{\mu}M$ of siderphore, and showed fungal cell wall-degrading activity including $0.46{\mu}mol/min/mg$ of chitinase and $0.83{\mu}mol/min/mg$ of ${\beta}$-1,3 glucanase. S. costaricanus HR391 secreted 87.49 mg/L of rhamnolipid, and produced 9.49 mg/L and 4.3 mM of lipopeptide, iturin A and surfactin, respectively, all they are membrane-disrupting biosurfactants. It also produced antimicrobial peptide and antibiotics phenazine. In addition to antifungal substances, S. costaricanus HR391 secreted plant growth-promoting phytohormones, zeatin, gibberellins and IAA. These results suggest that S. costaricanus HR391 may be utilized as an environment-friendly biocontrol agent against some important pathogenic fungi.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.88-107
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• 2023

In the present investigation, bacterial isolates from infected apple trees causing apple canker during winter were studied in the northern Gyeongbuk Province, Korea. The pathogen was identified as Pseudomonas syringae pv. syringae (Pss) through various physiological and biochemical characterization assays such as BIOLOG, gas chromatography of fatty acid methyl esters, and 16S rRNA. Bioassays for the production of phytotoxins were positive for syringopeptin and syringomycin against Bacillus megaterium and Geotrichum candidum, respectively. The polymerase chain reaction (PCR) method enabled the detection of toxin-producing genes, syrB1, and sypB in Pss. The differentiation of strains was performed using LOPAT and GATTa tests. Pss further exhibited ice nucleation activity (INA) at a temperature of -0.7℃, indicating an INA⁺ bacterium. The ice-nucleating temperature was -4.7℃ for a non-treated control (sterilized distilled water), whereas it was -9.6℃ for an INA^- bacterium Escherichia coli TOP10. These methods detected pathogenic strains from apple orchards. Pss might exist in an apple tree during ice injury, and it secretes a toxin that makes leaves yellow and cause canker symptoms. Until now, Korea has not developed antibiotics targeting Pss. Therefore, it is necessary to develop effective disease control to combat Pss in apple orchards. Pathogenicity test on apple leaves and stems showed canker symptoms. The pathogenic bacterium was re-isolated from symptomatic plant tissue and confirmed as original isolates by 16S rRNA. Repetitive element sequence-based PCR and enterobacterial repetitive intergenic consensus PCR primers revealed different genetic profiles within P. syringae pathovars. High antibiotic susceptibility results showed the misreading of mRNA caused by streptomycin and oxytetracycline.

• Analytical Science and Technology
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• v.9 no.1
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• pp.107-111
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• 1996

A phytotoxic compound was isolated from a culture of Bipolaris cynodontis, a fungus pathogenic to Bermuda grass. The structure was determined by spectroscopic analyses including 2D NMR experiments, to be sesquiterpene having a 9-carbon unit side chain. The compound inhibits the root growth of the seedlings of Italian ryegrass and rice plant, the host plant of the B. cynodontis, by about 100% at 100ppm, and it is suggested that this may play an important role in the expression of the disease symptom.

• The Plant Pathology Journal
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• v.17 no.5
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• pp.290-294
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• 2001

Forty(40) isolates of Fusarium oxysporum isolated from wilting tomato plants at Buyeo of Korea in 1997 were inoculated to four tomato cultivars (Ponderosa, Okitsu 3, Walter, and Zuiken) to examine pathogenic reactions. Isolation rates of F. oxysporum f. sp. lycopersici (FOL) races 1 and 2, and F. oxysporum f. sp. radicis-lycopersici(FORL) were 3.5%, 24.5%, and 57.5%, respectively. Mycelial growth on potato-dextrose agar at different temperature for the three pathogens was $26^{\circ}$. In the pathogenicity tests, however, the range of optimum temperature for disease development for FORL was between 15 and $20^{\circ}$, while that for races 1 and 2 of FOL were specifically pathogenic to tomato only. This suggests that host ranges of FORL and FOL differ significantly.

• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.1120-1123
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• 2001

Screening tests against six plant pathogenic fungi were performed in order to develop biopesticides. Actinomycetes were used to discriminate Bacillus thuringiensis for wide use as a microbial pesticide. From more than 100 actinomycetes tested, twelve strains showed potent antifungal activities. We report in vivo screening results from fermentation broths of these twelve strains and identification of the strain taxa.

• Journal of Wetlands Research
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• v.9 no.1
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• pp.91-98
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• 2007

Antifungal activity of compost teas was evaluated in vitro and in vivo experiments. In vitro test, fourteen compost teas were produced using five different composts and through six different methods for compost tea production. Eleven pathogenic fungi were used as indicators of antifungal activity of compost teas. In vivo test, one of the compost teas used in vitro test was sprayed to cucumber leaves which were infected with powdery mildew in order to evaluate antifungal activity of compost tea. From the results of the tests, it was found that all compost teas used this study showed antifungal activity and the proper application of compost teas against pathogenic fungi for obtaining optimal effects was important to know.

• Korean Journal Plant Pathology
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• v.3 no.3
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• pp.236-238
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• 1987

A bacterial disease of elephant foot, Hydrosome rivieri Engl., was newly found in Taejon, Korea in August 1986. The affected plants showed symptoms of soft rot on leaf blades and petioles. Bacterial isolates from affected plants found to be pathogenic to elephant foots by antificial inoculation, producing similar symptoms with those produced naturally. The baterium was also pathogenic to carrot, Chinese cabbage, radish, potato and onion, and developed symptom of soft root on them. On the basis of bacteriological characteristics and pathogenicity, tested bacterium was identified as Erwinia carotovora subsp. carotovora and this disease was proposed to name 'Bacterial soft rot of elephant foot'.