• Journal of Microbiology and Biotechnology
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• v.12 no.2
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• pp.249-257
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• 2002

Pseudomonas fluorescens GL20 is a plant growth-promoting rhizobacterium that produces a large amount of hydroxamate siderophore under iron-limited conditions. The strain GL20 considerably inhibited the spore germination and hyphal growth of a plant pathogenic fungus, Fusarium solani, when iron was limited, significantly suppressed the root-rot disease on beans caused by F. solani, and enhanced the plant growth. The mechanism for the beneficial effect of strain GL20 on the disease suppression was due to the siderophore production, evidenced by mutant strains derived from the strain. Analysis of the outer membrane protein profile revealed that the growth of strain GL20 induced the synthesis of specific iron-regulated outer membrane proteins with molecular masses of 85- and 90 kDa as the high-affinity receptors for the ferric siderophore. In addition, a cross-feeding assay revealed the presence of multiple inducible receptors for heterologous siderophores in the strain. In order to induce increased efficacy and potential in biological control of plant disease, a siderophore-overproducing mutant, GL20-S207, was prepared by NTG mutagenesis. The mutant GL20-S207 produced nearly 2.3 times more siderophore than the parent strain. In pot trials of beans with F. solani, the mutant increased plant growth up to 1.5 times compared with that of the parent strain. These results suggest that the plant growth-promoting P. fluorescens GL20 and the genetically bred P. fluorescens GL20-S207 can play an important role in the biological control of soil-borne plant diseases in the rhizosphere.

• Korean Journal of Plant Resources
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• v.32 no.2
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• pp.144-152
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• 2019

Ginseng (Pnanx ginseng C. A. Meyer) is famous worldwide, and is very important cash crop and medicinal herb in Korea. It takes four to five years to produce harvestable ginseng roots, and ginseng is attacked by several pathogens during cultivation. We investigated the disease rate caused by ginseng root rot from 6 years old ginseng cultivation fields (Chungnam; 9 fields, Chungbuk; 11 fields, Gangwon 5 fields). The highest disease severity was Dangjin D (2.9) and the lowest one was Gaesan C (0.6). Of the 625 isolations, 340 isolations were classified as Ilyonectria radicicola and Fusarium solani. Finally, genetic diversity of I. radicicola and F. solani was confirmed by sequence analysis. Among the I. radicicola group, I. mors-panacis, which is known as highly virulent pathogen, and I. liriodendri, I. robusta and I. cyclamicicola, which are weakly virulent pathogens, were identified. In the case of F. solani, it is divided into two groups, but it is necessary to conduct diversity research through genetic analysis and pathogenetic studies using various markers. Based on these results, it could be used as a basic data for control of ginseng root rot pathogens.

• Journal of Life Science
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• v.14 no.1
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• pp.193-197
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• 2004

A continuous enrichment culture procedure was used to isolate bacteria from various soil sources capable of suppressing large patch disease of turfgrass. Six isolates consistently suppressed large patch in turfgrass, and ranged in the spectrum of extracellular enzymes that they expressed. The best disease- suppressing isolate, TBM912, expressed protease, CMCase, and pectinase activity and inhibited the growth of Rhizectonin solani and Betrytis cinerea in vitro. Here we show that this strain also produces an antibiotic that was identified by TLC, SDS-PACE and HPLC analysis as lipopeptide.

• Microbiology and Biotechnology Letters
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• v.25 no.1
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• pp.62-67
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• 1997

A potential biocontrol bacterium, YB-70 was isolated from a rhizosphere in suppressive soil and identified as a strain of Bacillus subtilis. In several biochemical and in vitro antibiosis tests on Fusarium solani with the culture filterates from B. subtilis YB-70, we found that antifungal mechanism of B. subtilis YB-70 was mediated by antibiotic substances produced from the bacterium. These antifungal substances were appeared to be hear-resistant, micromolecular, and ethy alcohol soluble. Antifungal agents produced by B. subtilis YB-70 showed strong inhibified against root-rotting fungi F. solani in in vivo pot test. An antifungal substance. YBS-1s, was purified from the culture broth of B. subtilis YB-70 by isoelectronic precipitation, silica gel column chromatography and Sephadex LH-20 column chromatography analysis by Fab-MASS, $^{1}$H-NMR, $^{13}$C-NMR, DEPT, and amino acid analyzer revealed that the YBS-1A was a peptide antibiotics of iturin class containing seven amino acids from five different groups, and the other(YBS-1B) was an analogue of iturin group composed of 11 amino acids with larher molecular weight of about 1, 500 dalton, which was lager than that of iturin A.

• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.226-236
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• 2020

Antibiotic resistance by pathogenic bacteria and fungi is one of the most serious global public health problems in the 21^st century, directly affecting human health and lifestyle. Pseudomonas aeruginosa and Staphylococcus aureus with strong resistance to the common antibiotics have been isolated from Intensive Care Unit patients at Zagazig Hospital. Thus, in this study we assessed the biocidal activity of nanoparticles of silver, copper and zinc synthesized by Fusarium solani KJ 623702 against these multidrug resistant-bacteria. The synthesized Metal Nano-particles (MNPs) were characterized by UV-Vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Zeta potential. The Fourier transform infrared spectroscopy (FTIR) result showed the presence of different functional groups such as carboxyl, amino and thiol, ester and peptide bonds in addition to glycosidic bonds that might stabilize the dispersity of MNPs from aggregation. The antimicrobial potential of MNPs by F. solani against the multidrug-resistant (MDR) P. aeruginosa and S. aureus in addition to the mycotoxigenic Aspergillus awamori, A. fumigatus and F. oxysporum was investigated, based on the visual growth by diameter of inhibition zone. Among the synthesized MNPs, the spherical AgNPs (13.70 nm) displayed significant effect against P. aeruginosa (Zone of Inhibition 22.4 mm and Minimum Inhibitory Concentration 21.33 ㎍/ml), while ZINC oxide Nano-Particles were the most effective against F. oxysporum (ZOI, 18.5 mm and MIC 24.7 ㎍/ml). Transmission Electron Microscope micrographs of AgNP-treated P. aeruginosa showed cracks and pits in the cell wall, with internalization of NPs. Production of pyocyanin pigment was significantly inhibited by AgNPs in a concentration-dependent manner, and at 5-20 ㎍ of AgNPs/ml, the pigment production was reduced by about 15-100%, respectively.

• The Plant Pathology Journal
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• v.38 no.3
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• pp.212-219
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• 2022

Fusarium root rot caused by the soil-borne fungus Fusarium solani is one of the most important fungal diseases of cassava in Thailand, resulting in high yield losses of more than 80%. This study aimed to investigate if the exogenous application of salicylic acid formulations (Zacha) can induce resistance in cassava against Fusarium root rot and observe the biochemical changes in induced cassava leaf tissues through synchrotron radiation based on Fourier-transform infrared (SR-FTIR) microspectroscopy. We demonstrated that the application of Zacha11 prototype formulations could induce resistance against Fusarium root rot in cassava. The in vitro experimental results showed that Zacha11 prototype formulations inhibited the growth of F. solani at approximately 34.83%. Furthermore, a significant reduction in the disease severity of Fusarium root rot disease at 60 days after challenge inoculation was observed in cassava plants treated with Zacha11 at a concentration of 500 ppm (9.0%). Population densities of F. solani were determined at 7 days after inoculation. Treatment of the Zacha11 at a concentration of 500 ppm resulted in reduced populations compared with the distilled water control and differences among treatment means at each assay date. Moreover, the SR-FTIR spectral changes of Zacha11-treated epidermal tissues of leaves had higher integral areas of lipids, lignins, and pectins (1,770-1,700/cm), amide I (1,700-1,600/cm), amide II (1,600-1,500/cm), hemicellulose, lignin (1,300-1,200/cm), and cellulose (1,155/cm). Therefore, alteration in defensive carbohydrates, lipids, and proteins contributed to generate barriers against Fusarium invasion in cassava roots, leading to lower the root rot disease severity.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.435-440
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• 2000

A pathogenic fungus causing balloon flower root rot (Platycodon grandiflorum) was isolated from naturally infected roots. The microbial characteristics of the isolated microorganism were similar to those of Rhizoctonia solani. About 500 bacterial species from field soils were screened for a biological agent against the above-mentioned putative pathogen, and several bacteria with the antifungal activity were isolated. Among them, the isolated JS2 was identified as Pseudomonas aeruginosa. This strain showed a broad spectrum of antifungal activity potentially. When the antifungal substance was purified from a broth culture of JS2, it was identified as 2,4-diacetylphloroglucinol (Phl).

• Korean Journal Plant Pathology
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• v.1 no.1
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• pp.72-78
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• 1985

The effects of temperature. pH, carbon and nitrogen sources on the growth of Rhizoctonia solani were studied by using five hyphal anastomosis groups(four cultural types, 7 isolates) of the fungus. The ranges of optimum temperature were $20^{\circ}C$ in the AG 2-1, AG 2-2 and AG 4, and $25^{\circ}C$ in the AG 1-IA, AG 1-IB, AG 3, AG 5. The optimum pH for the mycelial growth was 6-7 in the fungus. Glucose in the AG 1-lA, AG 1-IB, AG 2-2, AG 3 and AG 5, sucrose in the AG 2-1 and fructose in the AG 4 were the most effective for the mycelial growth, but glycerine, cellulose and lactose were not effectively utilized as nutrients. $Ca(NO_3)_2$ in the AG 1-IA, AG 1-IB and AG 4, asparagine in the AG 2-1, $KNO_3$ in the AG 2-2 and $NaNO_3$ in the AG 5 were the best nitrogen sources for the mycelial growth, but $NH_4NO_3$ was not easily utilized by the fungus. Nitrate and organic nitrogens for the fungal growth were utilized better than ammonium nitrogen.

• Horticultural Science & Technology
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• v.32 no.6
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• pp.879-886
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• 2014

This study was conducted to test in vitro the antagonistic effect of composted liquid manure (CLM) against soil-borne turfgrass pathogenic fungi, Rhizoctonia solani AG-2-2 (IIIB) (brown patch), R. solani AG-2-2 (IV) (large patch), and Sclerotinia homoeocarpa (dollar spot) for environmentally friendly turfgrass management. CLMs were collected from 9 livestock excretion treatment facilities around the country including Gunwi (GW), Hapcheon (HC), Hoengseong (HS), Icheon (IC), Iksan (IS), Muan (MA), Nonsan (NS), and Yeoju (YJ). CLMs of IC, GW, and IS showed s ignificant (p < 0.05) mycelium growth inhibition that was 17.8%, 20.4%, and 48.0% against R. solani AG-2-2 (IIIB), R. solani AG-2-2 (IV), and S. homoeocarpa, respectively. A t otal of 110 bacterial isolates were obtained from the CLMs that showed antagonistic effects. Among them, 5, 4, and 10 microbe isolates showed promising antifungal activity against mycelium growth of R. solani AG-2-2 (IIIB), R. solani AG-2-2 (IV), and S. homoeocarpa, respectively. The bacterial isolates ICIIIB60, GWIV70, and ISSH20 effectively inhibited the mycelial growth of three soil-borne turfgrass pathogens. Selected bacterial isolates were identified as Alcaligenes sp., Bacillus licheniformis Ab2, and B. subtilis C7-3 through 16s rDNA gene sequence analysis. Among 5 fungicides, the most compatible fungicide with ICIIIB60, GWIV70, and ISSH20 was tebuconazol, toclofos-methyl and toclofos-methyl, respectively. These findings suggested that CLMs could be effectively used not only as organic liquid fertilizer sources but also as biological control agents for soil-borne turfgrass diseases such as brown patch, large patch, and dollar spot.

• Research in Plant Disease
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• v.14 no.1
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• pp.43-50
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• 2008

Rhizoctonia blight (large patch) caused by Rhizoctonia solani AG2-2 is one of the major diseases on zoysiagrass in golf courses. In this study, anatgonistic bacteria to R. solani AG2-2 were selected in vitro tests using confrontation bioassay and triple layer agar diffusion method. The most active bacteria, Bacillus subtilis CJ-9 were tested for controlling large patch in pots. Relative Performance Indies (RPI) was used as a criterion for the selection of potential biocontrol agent. B. subtilis CJ-9 showed resistance to major synthetic agrochemicals used in golf course. In field tests at golf course, B. subtilis CJ-9 was more effective in suppression of large patch severity and population development of R. solani AG2-2 in soil than chemical fungicides. B. subtilis CJ-9 could be an alternative to chemical fungicides for eco-friendly management of large patch on zoysiagrass.