Publications by authors named "Nan Hee Yu"

22 Publications

  • Page 1 of 1

First Report of Shot-hole on Flowering Cherry Caused by and pv. .

Plant Dis 2021 Jun 18. Epub 2021 Jun 18.

Chonnam National University College of Agriculture and Life Sciences, 98413, 77 Yongbong-ro, Buk-gu, Gwangju, Korea (the Republic of), 61186;

The shot-hole disease (SH) is one of the most common and important diseases affecting the flowering cherry (FC; Matsumura; 'Somei-yoshino') trees in South Korea every year, resulting in premature defoliation and reduced flowering in the following year. However, pathogens associated with the disease remain unknown, which has rendered disease management challenging. Here, the pathogens associated with SH, their biochemical characteristics, and their host range were elucidated. Detached leaf and assays revealed that two biofilm-forming bacteria, namely (Bc) and pv. (Pss), caused SH of FC trees. These pathogens were recorded for the first time as the causes of SH of FC trees in South Korea. Additionally, the two pathogens induced similar disease symptoms in several stone fruits belonging to the genus , including peach (), plum (), and apricot (), with peach being the most susceptible. These results indicate that Bc and Pss caused SH on FC trees and presented a broad spectrum of hosts. Furthermore, pv. , the causative agent of leaf spot on stone fruits, incited brown spots and shot holes on FC leaves. Therefore, FC trees are susceptible to infections by various pathogenic bacteria, including Bc, Pss, and Xap. These findings will be of great importance as a reference for effective management of SH in the face of possible cross-infection between species in the future.
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http://dx.doi.org/10.1094/PDIS-03-21-0547-SCDOI Listing
June 2021

and Antibacterial Activity of Serratamid, a Novel Peptide-Polyketide Antibiotic Isolated from C1, against Phytopathogenic Bacteria.

J Agric Food Chem 2021 May 29;69(19):5471-5480. Epub 2021 Apr 29.

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Republic of Korea.

A new hybrid non-ribosomal peptide-polyketide antibiotic (serratamid) for phytoprotection was isolated from the ethyl acetate layer of tryptic soy agar culture of the soil bacterium C1 through bioassay-guided fractionation. Its chemical structure was elucidated using instrumental analyses, such as mass and nuclear magnetic resonance spectrometry. Serratamid showed antibacterial activity against 15 phytopathogenic bacteria, with minimum inhibitory concentration (MIC) values ranging from 0.244 to 31.25 μg/mL. , it displayed strong antibacterial activity against and four spp., with MIC values (0.244-0.488 μg/mL) superior to those of streptomycin sulfate, oxolinic acid, and oxytetracycline. Further, serratamid and the ethyl acetate layer of C1 effectively reduced bacterial wilt caused by on tomato seedlings and fire blight caused by on apple fruits in a dose-dependent manner. These results suggest that serratamid is a promising candidate as a potent bactericide for controlling bacterial diseases.
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http://dx.doi.org/10.1021/acs.jafc.1c01162DOI Listing
May 2021

Deciphering the Relationship Between Cycloheximides Structures and Their Different Biological Activities.

Front Microbiol 2021 7;12:644853. Epub 2021 Apr 7.

Department of Agricultural Chemistry, College of Agriculture and Life Science, Institute of Environmentally Friendly Agriculture, Chonnam National University, Gwangju, South Korea.

species are the most important sources of antibacterial, antifungal, and phytotoxic metabolites. In this study, cycloheximide (CH) and acetoxycycloheximide (ACH) were isolated from the fermentation broth of sp. JCK-6092. The antifungal and phytotoxic activities of the two compounds (CH and ACH) and a cycloheximide derivative, hydroxycycloheximide (HCH), were compared. CH exhibited the strongest antagonistic activity against all the true fungi tested, followed by ACH and HCH. However, both CH and ACH displayed similar mycelial growth inhibitory activities against several phytopathogenic oomycetes, and both were more active than that of HCH. Disparate to antifungal ability, ACH showed the strongest phytotoxic activity against weeds and crops, followed by HCH and CH. ACH caused chlorophyll content loss, leaf electrolytic leakage, and lipid peroxidation in a dose-dependent manner. Its phytotoxicity was stronger than that of glufosinate-ammonium but weaker than that of paraquat in the experiments. CH and its derivatives are well-known protein synthesis inhibitors; however, the precise differences between their mechanism of action remain undiscovered. A computational study revealed effects of CHs on the protein synthesis of (oomycetes), (true fungus), and (plant) and deciphered the differences in their biological activities on different targets. The binding energies and conformation stabilities of each chemical molecule correlated with their biological activities. Thus, molecular docking study supported the experimental results. This is the first comparative study to suggest the ribosomal protein alteration mechanisms of CHs in plants and fungi and to thus show how the protein inhibitory activities of the different derivatives are altered using molecular docking. The correlation of structures features of CHs in respect to bond formation with desired protein was revealed by density functional theory. Overall collective results suggested that CHs can be used as lead molecules in the development of more potent fungicides and herbicides molecules.
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http://dx.doi.org/10.3389/fmicb.2021.644853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8058199PMC
April 2021

First Report of Associated with Leaf Spot on Flowering Cherry in South Korea.

Plant Dis 2021 Jan 18. Epub 2021 Jan 18.

Chonnam National University College of Agriculture and Life Sciences, 98413, 77 Yongbong-ro, Buk-gu, Gwangju, Korea (the Republic of), 61186;

Flowering cherry (FC, Matsumura; Somei-yoshino cherry) is an ornamental tree, planted across South Korea and producing stunning flowers in spring. The seasonal blooms are annually celebrated during cherry blossom festivals in many locations across the country. The leaf spot disease is among the most common and important diseases affecting FC trees every year, resulting in premature defoliation and reduced flowering of cherry blossoms in the following year. In May 2018, brown spots (2 to 5 mm), circular to irregular and with dark borders were observed on FC leaves in Hadong, Gyeongsangnamdo, South Korea (35°07'48.9"N, 127°46'53.8"E), with a disease incidence of 55%. Single lesions often coalesced and were sometimes perforated, leaving shot holes. Sampled leaves were surface sterilized with 1% NaOCl for 1 min and 70% ethanol for 30 s, and then rinsed twice with sterile distilled water. About 2-mm-long infected leaf pieces from the margins of lesions were put onto water agar (WA, 1.5% agar) plates and incubated at 25oC for 72 h. Mycelia grown from symptomatic tissue were transferred to PDA plates, and five similar fungal isolates were obtained from hyphal tips. They produced a strong reddish-orange diffusible pigment on PDA after 5 d and exudates after 8 d. Conidia were globular to pear-shaped, dark, verrucose, multicellular, and 14.8 to 23.5 μm in diameter (av. = 18.7 μm, = 30) for isolate JCK-CSHF10. These morphological characteristics were consistent with the genus. Three loci, ITS, , and , from three isolates JCK-CSHF8, JCK-CSHF9, and JCK-CSHF10 were amplified using the primer pairs ITS1F/LR5 (Gardes and Bruns 1993; Vilgalys and Hester 1990), Btub2Fd/Btub4Rd (Woudenberg et al. 2009), and RPB2-5F2/RPB2-7cR (Liu et al. 1999; Sung et al. 2007), respectively. The ITS, , and sequences of the three isolates were deposited in Genbank (MW368668-MW368670, MW392083-MW392085, and MW392086-MW392088, respectively), showing 99.6 to 100% identity to (E33), a later synonym for (Hou et al. 2020). The phylogenetic tree using concatenated sequences of the three loci placed the three isolates in a cluster of (CBS 232.59, CGMCC 3.18362, and CBS 384.36; Hou et al. 2020). Taken together, the three isolates were identified as . The pathogenicity of JCK-CSHF10 was tested on 15 healthy leaves on three FC trees (cv. Somei-yoshino, 1.2 m in height) kept in a greenhouse. Five-mm-diameter plugs from 7-d-old fungal cultures grown on PDA or mycelia-free PDA plugs as controls were placed on the abaxial side of a leaf at three points, previously wounded by a sterile needle (Zlatković et al. 2016). Inoculation sites were covered with moist cotton plugs. Trees were then covered with a clear plastic bag and maintained in high humidity at 25oC in darkness for 24 h, followed by a 12-h photoperiod. Brown spots appeared on inoculated leaves after 7 d, identical to those observed in the field, while control leaves remained symptomless. This experiment was repeated three times. A fungus with the same morphology as JCK-CSHF10 was recovered from lesions, thus confirming Koch's postulates. (syn. ) has been reported as a leaf spot-causing agent on sp. (Chen et al. 2017) and (Chen et al. 2020). To date, there is no report on the occurrence of from leaf spots on FC. To our knowledge, this is the first report of causing leaf spot on FC in South Korea.
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http://dx.doi.org/10.1094/PDIS-12-20-2711-PDNDOI Listing
January 2021

Biological Control of Tomato Bacterial Wilt, Kimchi Cabbage Soft Rot, and Red Pepper Bacterial Leaf Spot Using JCK-5075.

Front Plant Sci 2020 1;11:775. Epub 2020 Jul 1.

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea.

The over and repeated use of chemical bactericides to control plant bacterial diseases has resulted in unwanted effects, such as environmental pollution, residual toxicity, and resistance buildup in bacterial pathogens. Many previous studies have aimed to develop biological control agents to replace chemical bactericides. In this study, the antibacterial efficacy of the fermentation broth of JCK-5075 and its antibacterial compounds were evaluated against plant pathogenic bacteria, using both and bioassays. Pelgipeptins (PGPs) A, B, C, and D that were isolated from JCK-5075 displayed broad-spectrum antibacterial activity against various plant pathogenic bacteria. The fermentation broth of JCK-5075, at 5-fold dilution, effectively suppressed the development of tomato bacterial wilt, Kimchi cabbage soft rot, and red pepper bacterial leaf spot in pot experiments with control values of 81, 84, and 67%, respectively. PGP-A and C, at 200 μg/ml, were also found to markedly reduce the development of Kimchi cabbage bacterial soft rot by 75% and tomato bacterial wilt by 83%, respectively, and their disease control efficacy was comparable to that of oxolinic acid with control values of 81 and 85%, respectively. Additionally, the antibacterial activity of PGP-C was found to be directly correlated with membrane damage mechanisms. These results indicates that JCK-5075 producing PGPs could be used as a biocontrol agent for the control of plant bacterial diseases. This is the first report on the and antibacterial activity of PGPs against bacterial plant pathogens.
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http://dx.doi.org/10.3389/fpls.2020.00775DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7340725PMC
July 2020

Corrigendum: The Hsp90 Inhibitor, Monorden, Is a Promising Lead Compound for the Development of Novel Fungicides.

Front Plant Sci 2020 20;11:635. Epub 2020 May 20.

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Science, Chonnam National University, Gwangju, South Korea.

[This corrects the article DOI: 10.3389/fpls.2020.00371.].
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http://dx.doi.org/10.3389/fpls.2020.00635DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7251308PMC
May 2020

The Hsp90 Inhibitor, Monorden, Is a Promising Lead Compound for the Development of Novel Fungicides.

Front Plant Sci 2020 2;11:371. Epub 2020 Apr 2.

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Science, Chonnam National University, Gwangju, South Korea.

Endophytic fungi are great resources for the identification of useful natural products such as antimicrobial agents. In this study, we performed the antifungal screening of various plant endophytic fungi against the dollar spot pathogen and finally selected sp. JS-0112 as a potential biocontrol agent. The bioactive compound produced by the strain JS-0112 was identified as monorden known as an inhibitor of heat shock protein 90 (Hsp90). Monorden exhibited strong antagonistic activity against most tested plant pathogenic fungi particularly against tree pathogens and oomycetes with the minimum inhibitory concentration values less than 2.5 μg mL. Extensive assays revealed that monorden effectively suppressed the development of several important plant diseases such as rice blast, rice sheath blight, wheat leaf rust, creeping bentgrass dollar spot, and cucumber damping-off. Especially, it showed much stronger disease control efficacy against cucumber damping-off than a synthetic fungicide chlorothalonil. Subsequent molecular genetic analysis of fission yeast and suggested that Hsp90 is a major inhibitory target of monorden, and sequence variation among fungal Hsp90 is a determinant for the dissimilar monorden sensitivity of fungi. This is the first report dealing with the disease control efficacy and antifungal mechanism of monorden against fungal plant diseases and we believe that monorden can be used as a lead molecule for developing novel fungicides with new action mechanism for the control of plant diseases caused by fungi and oomycetes.
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http://dx.doi.org/10.3389/fpls.2020.00371DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7144829PMC
April 2020

Structure and antifungal activity of pelgipeptins from Paenibacillus elgii against phytopathogenic fungi.

Pestic Biochem Physiol 2020 Feb 13;163:154-163. Epub 2019 Nov 13.

Department of Chemistry, Chonnam National University, Gwangju 61186, Republic of Korea. Electronic address:

Paenibacillus elgii JCK1400 shows strong antifungal activity against various plant pathogenic fungi in vitro, but little is known about its mode of action. Four antifungal lipopeptides were isolated from P. elgii JCK1400 using bioassay-directed fractionation. Their chemical structures were determined to be pelgipeptins (PGPs) using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. Among the four lipopeptides, PGP-C showed the strongest mycelial growth inhibitory activity against several plant pathogenic fungi-with minimum inhibitory concentration (MIC) values ranging from 4 to 32 μg mL-followed by PGP-D, -A, and -B. In pot experiments, PGP-C also effectively suppressed the development of important fungal diseases in crops. In particular, PGP-C was effective in controlling tomato grey mold and wheat leaf rust, with control values of 91% and 73%, respectively, at a concentration of 125 μg mL. The fermentation broth of the antagonistic bacterium reduced the development of creeping bentgrass dollar spot and Kentucky bluegrass brown patch in a dose-dependent manner. However, our study on the effect of PGP-C on the fungal cell membrane-using microscopic observation with propidium iodide (PI) fluorescence-indicated that PGP-C does not target the fungal cell walls, but instead targets the cell membranes. This is the first study to report the in vitro and in vivo antifungal activity of PGP-C against various plant pathogenic fungi. Our results suggest that P. elgii JCK1400, which produces PGPs, could serve as a potential biocontrol agent for plant diseases caused by various fungi.
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http://dx.doi.org/10.1016/j.pestbp.2019.11.009DOI Listing
February 2020

Biological control of tomato bacterial wilt by oxydifficidin and difficidin-producing Bacillus methylotrophicus DR-08.

Pestic Biochem Physiol 2020 Feb 9;163:130-137. Epub 2019 Nov 9.

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Republic of Korea. Electronic address:

Bacillus methylotrophicus DR-08 exhibited strong antibacterial activity against Ralstonia solanacearum, a causal agent of tomato bacterial wilt. This study aimed to identify the antibacterial metabolites and evaluate the efficacy of the strain as a biocontrol agent for tomato bacterial wilt. A butanol extract of the DR-08 broth culture completely inhibited the growth of 14 phytopathogenic bacteria with minimum inhibitory concentration (MIC) values of 1.95-500 μg/mL. R. solanacearum was highly sensitive to the DR-08 extract, with an MIC value of 12.62 μg/mL. Two antibacterial metabolites were isolated and identified as difficidin and oxydifficidin derivatives through bioassay-guided fractionation and instrumental analyses. Both metabolite derivatives inhibited the growth of most of the phytopathogenic bacteria tested and the oxydifficidin derivatives generally presented a stronger antibacterial activity than the difficidin derivatives. A 30% suspension concentrate of DR-08, at a 500-fold dilution, effectively suppressed the development of tomato bacterial wilt in pot and field experiments. It also effectively reduced the development of bacterial leaf spot symptoms on peach and red pepper. The results of this study suggests that B. methylotrophicus DR-08 can be utilized as a biocontrol agent for various bacterial plant diseases including tomato bacterial wilt.
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http://dx.doi.org/10.1016/j.pestbp.2019.11.007DOI Listing
February 2020

Biological Control of Root-Knot Nematodes by Organic Acid-Producing WiKim0069 Isolated from Kimchi.

Plant Pathol J 2019 Dec 12;35(6):662-673. Epub 2019 Dec 12.

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Science, Chonnam National University, Gwangju 61186, Korea.

Root-knot nematodes (RKNs) are among the most destructive plant-parasites worldwide, and RKN control has been attempted mainly using chemical nematicides. However, these chemical nematicides have negative effects on humans and the environment, thus necessitating the search for eco-friendly alternative RKN control methods. Here, we screened nematicidal lactic acid bacteria (LAB) isolated from kimchi and evaluated their efficacy as biocontrol agents against RKNs. Of 237 bacterial strains, WiKim0069 showed the strongest nematicidal activity against the second-stage juveniles (J2) of , . , and and inhibited the egg hatch of . . The culture filtrate of WiKim0069 had a pH of 4.2 and contained acetic acid (11,190 μg/ml), lactic acid (7,790 μg/ml), malic acid (470 μg/ml), and succinic acid (660 μg/ml). An artificial mixture of the four organic acids produced by WiKim0069 also induced 98% J2 mortality at a concentration of 1.25%, indicating that its nematicidal activity was derived mainly from the four organic acids. Application of WiKim0069 culture filtrate suppressed the formation of galls and egg masses on tomato roots by in a dose-dependent manner in a pot experiment. The fermentation broth of WiKim0069 also reduced gall formation on melon under field conditions, with a higher efficacy (62.8%) than that of fosthiazate (32.8%). This study is the first report to identify the effectiveness of kimchi LAB against RKNs and to demonstrate that the organic acids produced by LAB can be used for the RKN management.
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http://dx.doi.org/10.5423/PPJ.OA.08.2019.0225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6901259PMC
December 2019

Draft Genome Sequence of JS-1675, an Endophytic Fungus from .

Microbiol Resour Announc 2019 May 16;8(20). Epub 2019 May 16.

Genetic Resources Assessment Division, National Institute of Biological Resources, Incheon, South Korea

The fungus strain JS-1675 has been reported to exert antimicrobial effects against various plant-pathogenic bacteria and fungi. Here, we report the draft genome sequence of for the first time. The assembly comprises 48,177,783 bp with 18 scaffolds.
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http://dx.doi.org/10.1128/MRA.00069-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6522779PMC
May 2019

Nematicidal activity of verrucarin A and roridin A isolated from Myrothecium verrucaria against Meloidogyne incognita.

Pestic Biochem Physiol 2018 Jun 26;148:133-143. Epub 2018 Apr 26.

Division of Applied Bioscience and Biotechnology, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Republic of Korea. Electronic address:

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http://dx.doi.org/10.1016/j.pestbp.2018.04.012DOI Listing
June 2018

Chemosensitization of to Chemical Fungicides Using Cyclic Lipopeptides Produced by Strain JCK-12.

Front Plant Sci 2017 27;8:2010. Epub 2017 Nov 27.

Department of Agricultural Chemistry, Institute of Environmentally-Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, South Korea.

Fusarium head blight (FHB) caused by infection with leads to enormous losses to crop growers, and may contaminate grains with a number of Fusarium mycotoxins that pose serious risks to human and animal health. Antagonistic bacteria that are used to prevent FHB offer attractive alternatives or supplements to synthetic fungicides for controlling FHB without the negative effects of chemical management. Out of 500 bacterial strains isolated from soil, JCK-12 showed strong antifungal activity and was considered a potential source for control strategies to reduce FHB. JCK-12 produces several cyclic lipopeptides (CLPs) including iturin A, fengycin, and surfactin. Iturin A inhibits spore germination of Fengycin or surfactin alone did not display any inhibitory activity against spore germination at concentrations less than 30 μg/ml, but a mixture of iturin A, fengycin, and surfactin showed a remarkable synergistic inhibitory effect on spore germination. The fermentation broth and formulation of JCK-12 strain reduced the disease incidence of FHB in wheat. Furthermore, co-application of JCK-12 and chemical fungicides resulted in synergistic antifungal effects and significant disease control efficacy against FHB under greenhouse and field conditions, suggesting that JCK-12 has a strong chemosensitizing effect. The synergistic antifungal effect of JCK-12 and chemical fungicides in combination may result from the cell wall damage and altered cell membrane permeability in the phytopathogenic fungi caused by the CLP mixtures and subsequent increased sensitivity of to fungicides. In addition, JCK-12 showed the potential to reduce trichothecenes mycotoxin production. The results of this study indicate that JCK-12 could be used as an available biocontrol agent or as a chemosensitizer to chemical fungicides for controlling FHB disease and as a strategy for preventing the contamination of harvested crops with mycotoxins.
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http://dx.doi.org/10.3389/fpls.2017.02010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5711811PMC
November 2017

Characterization of DA12 Showing Potent Antifungal Activity against Mycotoxigenic Species.

Plant Pathol J 2017 Oct 1;33(5):499-507. Epub 2017 Oct 1.

Division of Applied Bioscience and Biotechnology, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Korea.

In an attempt to develop a biological control agent against mycotoxigenic species, we isolated strain DA12 from soil and explored its antimicrobial activities. DA12 was active against the growth of mycotoxigenic , , , and both and (maize). Further screening using dual culture extended the activity range of strain DA12 against other fungal pathogens including , , , , , and . The butanol extract of the culture filtrate of DA12 highly inhibited the germination of macroconidia with inhibition rate 83% at a concentration of 31.3 μg/ml and 100% at a concentration of 250 μg/ml. The antifungal metabolite from the butanol extract was identified as iturin A by thin layer chromatography-bioautography. In addition, volatile organic compounds produced by DA12 were able to inhibit mycelial growth of various phytopathogenic fungi. The volatile compounds were identified as 2-heptanone, 5-methyl heptanone and 6-methyl heptanone by gas chromatography-mass spectrometry (GC-MS) analysis. These results indicate that the antagonistic activity of DA12 was attributable to iturin A and volatile heptanones, and the strain could be used as a biocontrol agent to reduce the development of diseases and mycotoxin contamination of crops.
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http://dx.doi.org/10.5423/PPJ.FT.06.2017.0126DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624492PMC
October 2017

Diffusible and Volatile Antifungal Compounds Produced by an Antagonistic G341 against Various Phytopathogenic Fungi.

Plant Pathol J 2017 Oct 1;33(5):488-498. Epub 2017 Oct 1.

Division of Applied Bioscience and Biotechnology, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Korea.

The aim of this study was to identify volatile and agar-diffusible antifungal metabolites produced by sp. G341 with strong antifungal activity against various phytopathogenic fungi. Strain G341 isolated from four-year-old roots of Korean ginseng with rot symptoms was identified as based on 16S rDNA and sequences. Strain G341 inhibited mycelial growth of all phytopathogenic fungi tested. experiment results revealed that -butanol extract of fermentation broth effectively controlled the development of rice sheath blight, tomato gray mold, tomato late blight, wheat leaf rust, barley powdery mildew, and red pepper anthracnose. Two antifungal compounds were isolated from strain G341 and identified as bacillomycin L and fengycin A by MS/MS analysis. Moreover, volatile compounds emitted from strain G341 were found to be able to inhibit mycelial growth of various phytopathogenic fungi. Based on volatile compound profiles of strain G341 obtained through headspace collection and analysis on GC-MS, dimethylsulfoxide, 1-butanol, and 3-hydroxy-2-butanone (acetoin) were identified. Taken together, these results suggest that G341 can be used as a biocontrol agent for various plant diseases caused by phytopathogenic fungi.
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http://dx.doi.org/10.5423/PPJ.OA.04.2017.0073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624491PMC
October 2017

Antibacterial Activity of Pharbitin, Isolated from the Seeds of , against Various Plant Pathogenic Bacteria.

J Microbiol Biotechnol 2017 Oct;27(10):1763-1772

Department of Agricultural Chemistry, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 61186, Republic of Korea.

This study aimed to isolate and characterize antibacterial metabolites from seeds and investigate their antibacterial activity against various plant pathogenic bacteria. The methanol extract of seeds showed the strongest activity against pv. (Xap) with a minimum inhibition concentration (MIC) value of 250 μg/ml. Among the three solvent layers obtained from the methanol extract of seeds, only the butanol layer displayed the activity with an MIC value of 125 μg/ml against Xap. An antibacterial fraction was obtained from seeds by repeated column chromatography and identified as pharbitin, a crude resin glycoside, by instrumental analysis. The antibacterial activity of pharbitin was tested in vitro against 14 phytopathogenic bacteria, and it was found to inhibit and four species. The minimum inhibitory concentration values against the five bacteria were 125-500 μg/ml for the n-butanol layer and 31.25-125 μg/ml for pharbitin. In a detached peach leaf assay, it effectively suppressed the development of bacterial leaf spot, with a control value of 87.5% at 500 μg/ml. In addition, pharbitin strongly reduced the development of bacterial wilt on tomato seedlings by 97.4% at 250 μg/ml, 7 days after inoculation. These findings suggest that the crude extract of seeds can be used as an alternative biopesticide for the control of plant diseases caused by and spp. This is the first report on the antibacterial activity of pharbitin against phytopathogenic bacteria.
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http://dx.doi.org/10.4014/jmb.1706.06008DOI Listing
October 2017

Nematicidal activity of grammicin produced by Xylaria grammica KCTC 13121BP against Meloidogyne incognita.

Pest Manag Sci 2018 Feb 19;74(2):384-391. Epub 2017 Oct 19.

Division of Applied Bioscience and Biotechnology, Institute of Environmentally Friendly Agriculture, College of Agriculture and Life Sciences, Chonnam National University, Gwangju, Republic of Korea.

Background: The endolichenic fungus Xylaria grammica KCTC 13121BP showed strong nematicidal activity against Meloidogyne incognita. This study aimed to identify the nematicidal metabolites and to evaluate the efficacy of the strain as a biocontrol agent under pot and field conditions.

Results: Bioassay-guided fractionation and instrumental analyses led to grammicin being identified as the nematicidal metabolite. Because patulin is a mycotoxic isomer of grammicin and is known to have strong antibacterial and cytotoxic activities, several biological activities of the two compounds were compared. Grammicin showed strong second-stage juvenile killing and egg-hatching inhibitory effects, with a 50% effective concentration at 72 h (EC ) of 15.9 µg/mL and a 50% effective concentration at 14 days (EC ) of 5.87 µg/mL, respectively, whereas patulin was virtually inactive in both respects. Patulin was strongly active toward various phytopathogenic bacteria in vitro, whereas grammicin was weakly so. Patulin at the concentration range of 0.1-10 µg/mL also showed dose-dependent cytotoxicity toward the human first-trimester trophoblast cell line SW.71, whereas grammicin was not toxic toward this cell line. In pot and field experiments, a wettable powder-type formulation and fermentation broth filtrate of X. grammica KCTC 13121BP effectively suppressed the development of root-knot nematode disease on tomato and melon plants.

Conclusion: The results suggest that X. grammica and grammicin may have potential applications for control of root-knot nematode disease of various crops. © 2017 Society of Chemical Industry.
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http://dx.doi.org/10.1002/ps.4717DOI Listing
February 2018

Development of a Biofungicide Using a Mycoparasitic Fungus BCP and Its Control Efficacy against Gray Mold Diseases of Tomato and Ginseng.

Plant Pathol J 2017 Jun 1;33(3):337-344. Epub 2017 Jun 1.

Department of Biotechnology, Yonsei University, Seoul 03722, Korea.

To develop a commercial product using the mycoparasitic fungus BCP, the scaleup of conidia production from a 5-l jar to a 5,000-l pilot bioreactor, optimization of the freeze-drying of the fermentation broth, and preparation of a wettable powder-type formulation were performed. Then, its disease control efficacy was evaluated against gray mold diseases of tomato and ginseng plants in field conditions. The final conidial yields of BCP were 3.3 × 10 conidia/ml for a 5-l jar, 3.5 × 10 conidia/ml for a 500-l pilot vessel, and 3.1 × 10 conidia/ml for a 5,000-l pilot bioreactor. The conidial yield in the 5,000-l pilot bioreactor was comparable to that in the 5-l jar and 500-l pilot vessel. On the other hand, the highest conidial viability of 86% was obtained by the freeze-drying method using an additive combination of lactose, trehalose, soybean meal, and glycerin. Using the freeze-dried sample, a wettable powder-type formulation (active ingredient 10%; BCP-WP10) was prepared. A conidial viability of more than 50% was maintained in BCP-WP10 until 22 weeks for storage at 40°C. BCP-WP10 effectively suppressed the development of gray mold disease on tomato with control efficacies of 64.7% and 82.6% at 500- and 250-fold dilutions, respectively. It also reduced the incidence of gray mold on ginseng by 65.6% and 81.3% at 500- and 250-fold dilutions, respectively. The results indicated that the new microbial fungicide BCP-WP10 can be used widely to control gray mold diseases of various crops including tomato and ginseng.
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http://dx.doi.org/10.5423/PPJ.FT.04.2017.0087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5461052PMC
June 2017

Notes on the lichen genus leptogium (collemataceae, ascomycota) in South Korea.

Mycobiology 2014 Jun 30;42(2):120-31. Epub 2014 Jun 30.

Korean Lichen Research Institute, Sunchon National University, Suncheon 540-950, Korea.

Leptogium (Ach.) Gray is distributed throughout South Korea; however, for nearly two decades no detailed taxonomic or revisionary research on this lichen genus has been conducted. This study examined the specimens deposited in the lichen herbarium at the Korean Lichen Research Institute, and samples were identified using descriptions recently published in the scientific literature. In this revisionary study, a total of fourteen species of Leptogium were documented, including new records of Leptogium delavayi Hue, Leptogium denticulatum Nyl., and Leptogium trichophoroides P. M. Jørg. & A. K. Wallace. Detailed descriptions of each species are given, including their morphological, anatomical, and chemical characteristics. A key to all Leptogium species known to occur in South Korea is also presented.
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http://dx.doi.org/10.5941/MYCO.2014.42.2.120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4112227PMC
June 2014

Draft Genome Sequence of Lichen-Forming Fungus Cladonia metacorallifera Strain KoLRI002260.

Genome Announc 2014 Feb 13;2(1). Epub 2014 Feb 13.

Korean Lichen Research Institute, Sunchon National University, Suncheon, South Korea.

The lichen-forming fungus Cladonia metacorallifera strain KoLRI002260 is capable of producing a number of secondary metabolites, including usnic, didymic, and squamatic acids, which have antitumor, antioxidant, and antibiotic activities. The draft genome assembly has a size of 36,682,060 bp, with a G+C content of 44.91%, and consists of 30 scaffolds.
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http://dx.doi.org/10.1128/genomeA.01065-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3924382PMC
February 2014

Agrobacterium tumefaciens-mediated transformation of the lichen fungus, Umbilicaria muehlenbergii.

PLoS One 2013 30;8(12):e83896. Epub 2013 Dec 30.

Korean Lichen Research Institute, Sunchon National University, Sunchon, Korea.

Transformation-mediated mutagenesis in both targeted and random manners has been widely applied to decipher gene function in diverse fungi. However, a transformation system has not yet been established for lichen fungi, severely limiting our ability to study their biology and mechanism underpinning symbiosis via gene manipulation. Here, we report the first successful transformation of the lichen fungus, Umbilicaria muehlenbergii, via the use of Agrobacterium tumefaciens. We generated a total of 918 transformants employing a binary vector that carries the hygromycin B phosphotransferase gene as a selection marker and the enhanced green fluorescent protein gene for labeling transformants. Randomly selected transformants appeared mitotically stable, based on their maintenance of hygromycin B resistance after five generations of growth without selection. Genomic Southern blot showed that 88% of 784 transformants contained a single T-DNA insert in their genome. A number of putative mutants affected in colony color, size, and/or morphology were found among these transformants, supporting the utility of Agrobacterium tumefaciens-mediated transformation (ATMT) for random insertional mutagenesis of U. muehlenbergii. This ATMT approach potentially offers a systematic gene functional study with genome sequences of U. muehlenbergii that is currently underway.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0083896PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3875497PMC
August 2014

Draft Genome Sequence of Lichen-Forming Fungus Caloplaca flavorubescens Strain KoLRI002931.

Genome Announc 2013 Aug 29;1(4). Epub 2013 Aug 29.

Korean Lichen Research Institute, Sunchon National University, Suncheon, South Korea.

Here we report a draft genome sequence of Caloplaca flavorubescens strain KoLRI002931, isolated from the bark of a gingko tree at Mt. Deogyu, Muju, South Korea. The genome sequence is 34,455,815 bp, with a GC content of 41.89%, consisting of 36 scaffolds.
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http://dx.doi.org/10.1128/genomeA.00678-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3757454PMC
August 2013