• Mycobiology
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• v.51 no.2
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• pp.67-71
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• 2023

A powdery mildew (Erysiphaceae) has been continuously collected on the leaves of Lonicera harae in the southern part of the Korean Peninsula, where this shrub is indigenous. Microscopic examination of the asexual morphs revealed that the current collections are differentiated from the all known Erysiphe species on Lonicera spp. by its longer conidiophores and longer conidia. Although the morphology of the chasmothecia is reminiscent of Erysiphe ehrenbergii and E. lonicerae, the specimens on L. harae differ from them in having smaller ascospores. A phylogenetic tree generated from a combined dataset of the internal transcribed spacer region and 28S rDNA gene sequences demonstrates that sequences obtained from three powdery mildew collections on L. harae clustered together as an independent species clade with high bootstrap values distant from other Erysiphe species on Lonicera, representing a species of its own. Based on morphological differences and molecular-phylogenetic results, the powdery mildew on L. harae is proposed as a new species, Erysiphe lonicerigena, and the holomorph of the fungus is described and illustrated in this study.

• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.556-566
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• 2011

A total of 31 Acinetobacter isolates were obtained from the rhizosphere of Pennisetum glaucum and evaluated for their plant-growth-promoting traits. Two isolates, namely Acinetobacter sp. PUCM1007 and A. baumannii PUCM1029, produced indole acetic acid (10-13 ${\mu}g$/ml). A total of 26 and 27 isolates solubilized phosphates and zinc oxide, respectively. Among the mineral-solubilizing strains, A. calcoaceticus PUCM1006 solubilized phosphate most efficiently (84 mg/ml), whereas zinc oxide was solubilized by A. calcoaceticus PUCM1025 at the highest solubilization efficiency of 918%. All the Acinetobacter isolates, except PUCM1010, produced siderophores. The highest siderophore production (85.0 siderophore units) was exhibited by A. calcoaceticus PUCM1016. Strains PUCM1001 and PUCM1019 (both A. calcoaceticus) and PUCM1022 (Acinetobacter sp.) produced both hydroxamate-and catechol-type siderophores, whereas all the other strains only produced catechol-type siderophores. In vitro inhibition of Fusarium oxysporum under iron-limited conditions was demonstrated by the siderophore-producing Acinetobacter strains, where PUCM1018 was the most potent inhibitor of the fungal phytopathogen. Acinetobacter sp. PUCM1022 significantly enhanced the shoot height, root length, and root dry weights of pearl millet seedlings in pot experiments when compared with controls, underscoring the plant-growth-promoting potential of these isolates.

• Applied Biological Chemistry
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• v.47 no.1
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• pp.17-21
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• 2004

This study was investigated the physiological properties of auxin-producing bacteria that have plant growth promoting activity and plant pathogen antagonistic ability. Auxin-producing bacteria were isolated from field soils of Gyeongsan, Korea. Selected strains were identified as a Pseudumonas fulva N21 and a Pantoea agglomerans; K35 by morphological and physiological test, and Biolog (Microlog) system. Auxins were determined by Salkowski in vitro test and mungbean adventitious root induction bioassay. Also produced indole-3-acetic acid (IAA) was identified by TLC. During cell growth, auxin production were highest in their idiophase after log phase and $35^{\circ}C$ at pH 7.5.

• Applied Biological Chemistry
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• v.50 no.3
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• pp.178-186
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• 2007

42 compounds such as ester, sulfonyl ester, phosphoyl ester and ether derivatives of 4-isopropylphenol (I) and 2-isopropylphenol (II) were synthesized. These derivatives were identified by IR, GC/MS and $^{1}H-NMR$ spectra. Their in vitro antifungal activities were tested against 10 plant pathogenic fungi. Among them, several compounds showed potent in vitro antifungal activity. The selected compounds showing potent in vitro antifungal activity were tested for their in vivo antifungal acitvities against 5 plant diseases such as rice blast, rice sheath blast, cucumber anthracnose, cucumber gray mold and tomato late blight. As a result, 2-isopropylphenyl piperonyloate (II-7a) showed a potent in vivo antifungal activity against cucumber anthracnose and tomato late blight, 4-isopropylphenyl 4-methoxybenzenesulfonate (I-6b) effectively inhibited the development of rice blast.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4854-4862
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• 2010

Twenty five compounds isopropylmethylphenyl benzenesulfonate derivatives of thymol (1), 4-isopropyl-3-methylphenol (2), 5-isopropyl-3-methylphenol (3), 4-isopropylphenol (4), and 2-isopropylphenol (5) derivatives were synthesized. These compounds were analyzed for their structural confirmation with IR, GC/MS, and $^1H$-NMR. Synthetic compounds were tested against phytopathogenic fungi activities such as Pyrcularia grisea, Rhizoctonia solani, Phytophthora infestans, Colletotrichum orbiculare, and Sphaerotheca fusca. 2-Isopropyl-5-methylphenyl o-toluenesulfonate (1a), 2-isopropylphenyl 2,4,5-trichloro-benzenesulfonate (5b) and 2-isopropylphenyl 2-methyl-5-nitrobenzenesulfonate (5e) showed a potent in vivo antifungal activity against Pyrcularia grisea, Phytophthora infestans and Sphaerotheca fusca.

• Journal of Microbiology and Biotechnology
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• v.21 no.4
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• pp.379-386
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• 2011

The objective of this work was to investigate the ability of the plant growth-promoting rhizobacterium Pseudomonas aureofaciens 63-28 to induce plant defense systems, including defense-related enzyme levels and expression of defense-related isoenzymes, and isoflavone production, leading to improved resistance to the phytopathogen Rhizoctonia solani AG-4 in soybean seedlings. Seven-day-old soybean seedlings were inoculated with P. aureofaciens 63-28, R. solani AG-4, or P. aureofaciens 63-28 plus R. solani AG-4 (P+R), or not inoculated (control). After 7 days of incubation, roots treated with R. solani AG-4 had obvious damping-off symptoms, but P+R-treated soybean plants had less disease development, indicating suppression of R. solani AG-4 in soybean seedlings. Superoxide dismutase (SOD) and catalase (CAT) activities of R. solani AG-4-treated roots increased by 24.6% and 54.0%, respectively, compared with control roots. Ascorbate peroxidase (APX) and phenylalanine ammonia lyase (PAL) activities of R. solani AG-4-treated roots were increased by 75.1% and 23.6%, respectively. Polyphenol oxidase (PPO) activity in soybean roots challenged with P. aureofaciens 63-28 and P+R increased by 25.0% and 11.6%, respectively. Mn-SOD (S1 band on gel) and Fe-SOD (S2) were strongly induced in P+R-treated roots, whereas one CAT (C1) and one APX (A3) were strongly induced in R. solani AG-4- treated roots. The total isoflavone concentration in P+Rtreated shoots was 27.2% greater than the control treatment. The isoflavone yield of R. solani AG-4-treated shoots was 60.9% less than the control.

• Microbiology and Biotechnology Letters
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• v.31 no.4
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• pp.421-428
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• 2003

To develop the functional-compost containing antifungal substance by using antagonistic microorganisms, Spinacia oleracea L and Rhizoctonia solani Kuhn O-28 were used as a model plant and phytopathogen, respectively. Total 80 strains were isolated from the compost of various waste foods mixture processed for a year. Among them, No.15-2 strain was selected due to its highest antifungal activity against R. solani Kuhn O-28 and was identified phyno- and phylogenotypically as Burkholderia cepacia genomovar V. which is rare probability in pathogen, by 16S rDNA sequencing and specific primer pair PCR method. B. cepacia No.15-2 preferentially dominated during the compost and its cell numbers were maintained almost $${\times}$10^{13}$ cuf/g for 15 days. The morbidity caused by R. solani Kuhn O-28 in S. oleracea L cultivation was reduced to 40% by addition of B. cepacia No.15-2. In conclusion, the antifungal compost using B. cepacia No.15-2 could be applied to biocontrol of various crops blights caused by fungal pathogen.

• Journal of Microbiology and Biotechnology
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• v.24 no.9
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• pp.1269-1279
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• 2014

Xanthomonas oryzae pv. oryzae (Xoo) strains are plant pathogenic bacteria that can cause serious blight of rice, and their virulence towards plant host is complex, making it difficult to be elucidated. Caenorhabditis elegans has been used as a powerful model organism to simplify the host and pathogen system. However, whether the C. elegans is feasible for studying plant pathogens such as Xoo has not been explored. In the present work, we report that Xoo strains PXO99 and JXOIII reduce the lifespan of worms not through acute toxicity, but in an infectious manner; pathogens proliferate and persist in the intestinal lumen to cause marked anterior intestine distension. In addition, Xoo triggers (i) the p38 MAPK signal pathway to upregulate its downstream C17H12.8 expression, and (ii) the DAF-2/DAF-16 pathway to upregulate its downstream gene expressions of mtl-1 and sod-3 under the condition of daf-2 mutation. Our findings suggest that C. elegans can be used as a model to evaluate the virulence of Xoo phytopathogens to host.

• The Korean Journal of Pesticide Science
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• v.10 no.3
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• pp.201-209
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• 2006

Antifungal activities of 43 different plant oils were evaluated against different phytopathogenic fungi. Thyme oil showed highest antifungal activity among the tested oils. The major of thyme oil were found to be thymol, carvacrol, bomeol, p-cymene and linalool. Thymol and carvacrol were found to be responsible for thyme's antifungal activity. The spore germination assay was conducted on Alternaria mail and Botrytis cinerea. Thymol and carvacrol strongly inhibited spore germination in the fungi test. In addition, thymol and carvacrol showed a curative effectiveness to gray mold disease on cucumber crop. The antifungal activities of alkylphenol and alkylaniline compounds, which has similar molecular structure to that of thymol or cavacrol, were also tested. It was found that alkylphenol compounds also show higher inhibition to spore germination. Thus, thymol, carvacrol and alkylphenol compounds can be used an potent antifungal agents.

• Korean Journal of Environmental Agriculture
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• v.30 no.3
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• pp.346-356
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• 2011

BACKGROUND: Chemical fungicides not only may pollute the ecosystem but also can be environmentally hazardous, as the chemicals accumulate in soil. Biological control is a frequently-used environment-friendly alternative to chemical pesticides in phytopathogen management. However, the use of microbial products as fungicides has limitations. This study isolated and characterized a three-antifungal-enzyme (chitinase, cellulase, and ${\beta}$-1,3-glucanase)-producing bacterium, and examined the conditions required to optimize the production of the antifungal enzymes. METHOD AND RESULTS: The antifungal enzymes chitinase, cellulase, and ${\beta}$-1,3-glucanase were produced by bacteria isolated from an sawmill in Korea. Based on the 16S ribosomal DNA sequence analysis, the bacterial strain AM50 was identical to Streptomyces sp. And their antifungal activity was optimized when Streptomyces sp. AM50 was grown aerobically in a medium composed of 0.4% chitin, 0.4% starch, 0.2% ammonium sulfate, 0.11% $Na_2HPO_4$, 0.07% $KH_2PO_4$, 0.0001% $MgSO_4$, and 0.0001% $MnSO_4$ at $30^{\circ}C$. A culture broth of Streptomyces sp. AM50 showed antifungal activity towards the hyphae of plant pathogenic fungi, including hyphae swelling and lysis in P. capsici, factors that may contribute to its suppression of plant pathogenic fungi. CONCLUSION(S): This study demonstrated the multiantifungal enzyme production by Streptomyces sp. AM50 for the biological control of major plant pathogens. Further studies will investigate the synergistic effect, to the growth regulations by biogenic amines and antifungal enzyme gene promoter.