• The Plant Pathology Journal
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• v.23 no.3
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• pp.180-186
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• 2007

The biocontrol agent, Serratia plymuthica A21-4, has been developed for controlling pepper Phytophthora blight. Serratia plymuthica A21-4 strongly inhibits the mycelial growth, zoospore formation, and cyst germination of Phytophthora capsici in vitro. The application of a cell suspension of strain A21-4 to pepper plants in pot experiments and in greenhouse successfully controlled the disease. The bacteria produced a potent antifungal substance which was a key factor in the suppression of Phytophthora capsici. The most active chemical com-pound was isolated and purified by antifungal activity-guided fractionation. The chemical structure was identified as a chlorinated macrolide $(C_{23}H_{31}O_8Cl)$ by spectroscopic (UV, IR, MS, and NMR) data, and was named macrocyclic lactone A21-4. The active compound significantly inhibited the formation of zoosporangia and zoospore and germination of cyst of P. capsici at concentrations lower than $0.0625{\mu}g/ml$. The effective concentrations of the macrocyclic lactone A21-4 for $ED_{50}$ of mycelial growth inhibition were $0.25{\mu}g/ml,\;0.25{\mu}g/ml,\;0.30{\mu}g/ml \;and\;0.75{\mu}g/ml$ against P. capsici, Pythium ultimum, Sclerotinia sclerotiorum and Botrytis cinerea, respectively.

• Journal of Microbiology and Biotechnology
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• v.16 no.3
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• pp.450-456
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• 2006

Pseudomonas fluorescens MC07 is a growth-promoting rhizobacterium that suppresses mycelial growth in fungi such as Rhizoctonia solani, Pythium ultimum, Fusarium oxysporum, and Phytophthora capsici. To determine the role of the bacterium's antifungal activity in disease suppression, we screened 2,500 colonies generated by Tn5lacZ insertions, and isolated a mutant 157 that had lost antifungal activity. The EcoRI fragment carrying Tn5lacZ was cloned into pBluescript II SK(+) and used as a probe to isolate wild-type clones from a genomic library of the parent strain, MC07. Two overlapping cosmid clones, pEH4 and pEH5, that had hybridized with the mutant clone were isolated. pEH4 conferred antifungal activity to the heterologous host P.fluorescens strain 1855.344, whereas pEH5 did not. Through transposon mutagenesis of pEH4 and complementation analyses, we delineated the 14.7-kb DNA region that is responsible for the biosynthesis of an antifungal compound. DNA sequence analysis of the region identified 11 possible open reading frames (ORF), ORF1 through ORF11. A BLAST search of each putative protein implied that the proteins may be involved in an antifungal activity similar to polyketides.

• Research in Plant Disease
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• v.21 no.1
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• pp.12-19
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• 2015

Antimicrobial activities of nano-materials were tested against several plant pathogens. Twelve different nano-materials were used to observe the antagonistic activity against three kinds of mold and sixteen different kinds of watermelon fruit rot pathogens (Acidovorax citrulli). According to the results, no antagonism have been found against the pathogen, Cylindrocarpon destructans. However in the case of Pythium ultimum, combination of Brass/Glucose 1,000 ppm confirmed the mycelial growth reduction by 94%. In addition, little effect was found against Rhizoctonia solani by Ag/Glucose 3,000 ppm. The remaining other nano-materials have different antimicrobial effect depending on the strains of A. citrulli. But in the case of lime (Cu/Salt 1,000 ppm) highest antimicrobial activity was observed with 97%. Moreover growth of five different strains of A. citrulli was checked by 99% with the combination of Ag/Glucose 1,000 ppm. 92% reduction of A. citrulli growth was observed with $Brass/CaCO_3$ 3,000 ppm. Tested nano-materials against different plant pathogens in this study showed the antimicrobial activity at the range of 24-70%.

• The Plant Pathology Journal
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• v.26 no.3
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• pp.253-259
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• 2010

In vitro and in vivo mycofumigation effects of the volatileproducing fungus Nodulisporium sp. CF016 isolated from stem of Cinnamomum loureirii and the role of its volatile compounds were investigated against phytopathogenic fungi. The volatile compounds produced by Nodulisporium sp. CF016 inhibited and killed a wide range of plant and storage pathogens including to Pythium ultimum, Rhizoctonia solani, Fusarium oxysporum, Phytophthora capsici, Sclerotinia sclerotiorum, Colletotrichum coccodes, Magnaporthe oryzae, Alternaria panax, Botrytis cinerea and Penicillium expansum. Mycofumigation with wheat bran-rice hull cultures of Nodulisporium sp. CF016 showed in vivo antifungal activity against gray mold caused by B. cinerea and blue mold caused by P. expansum of apple. The most abundant volatile compound produced by Nodulisporium sp. CF016 was $\beta$-elemene followed by 1-methyl-1,4-cyclohexadiene, $\beta$-selinene and $\alpha$-selinene. Nodulisporium sp. CF016 could be an attractive mycofumigant in controlling postharvest diseases of various fruits including apple.

• 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.

• Proceedings of the Turfgrass Society of Korea Conference
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• 2011.02a
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• pp.35-35
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• 2011

A large patch disease caused by Rhizoctonia solani AG2-2(IV) is a serious problem in turfgrass sites including golf courses and sports fields in Korea. The objectives of this study were to isolate some antagonistic microorganisms and to explain some involving mechanisms. Initially single colonies which were formed from the filtrates of various soil samples were obtained from LB culture and then co-cultured with R.solani AG2-2(IV) on PDA plate to explore some antagonistic microbes against for large patch fungus, Rhizoctonia solani AG2-2(IV). Out of total 82 antagonistic isolates which commonly had inhibition effect on Rhizoctonia solani AG2-2(IV) mycelial growth, one candidate (YPIN22) showed the most antifungal effect, which was confirmed by the longest distance from the edge of bacterial colony to the mycelial edge of the Rhizoctonia solani AG2-2(IV) in the dual culture. A succeeding investigation was to test any potential effect of the isolate on growth inhibition of 5 other turfgrass pathogens including R. solani solani AG2-2(IIIB), P. ultimum, C. caudatum, C. lunata, and F.oxysporum. Preliminary result indicated that the new isolate YPIN22 was also found to have antagonistic potential on the growth inhibition of those turfgrass pathogenic fungi, which was explained by inhibition zones ranging from 8 to 22mm. A further explanation of some characteristics of the isolate YPIN22 will be discussed in detail.

• Journal of Life Science
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• v.13 no.1
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• pp.90-98
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• 2003

An allium rhizobacterium Serratia plymuthica AL-1 was previously selected as a biocontrol agent of allium white rot. The chitinase from S. plymuthica AL-1 produced in medium containing colloidal chitin was purified by ammonium sulfate precipitation (40~70%), affinity adsorption, column chromatography on DEAE-sephadex A-50 and sephadex C-200 gel filtration. The enzyme was purified 10.8-fold with a yield of 7.3% from the starting culture broth. The purified chtinase gave a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis, it's molecular weight was estimated to be 55 kDa. The optimum pH and temperature of the purified enzyme were pH 5.5 and $55^{\circ}C$, respectively and it is stable up to $50^{\circ}C$ and maintains around 90% of its activity for 60min. The enzyme were activated by $Ca^{2+}$, $Mn^{2+}$ and $Mg^{2+}$ and inhibited by $Cu^{2+}$, SDS, $\rho$-CMB, MIA, respectively. The purified chitinase showed broad spectrum of antifungal activities against plant pathogenic fungi Sclerotium cepivoruin, Alternana alternnta, Colletotrichum glceosporioidrs, Phoma sp., Sclerotinia sclerotiorum, Stemphylium solani, Fusarium oxysporium f. sp. niveum but rarely inhibited Phytophthora capsici and Pythium ultimum.. The purified chitinase from S. plymuthica AL-1 caused swelling, lysis, deceleration and degradation of the hyphal tips of S. sczerotiorum causing allium white rot. It suggest that S. prymuthica AL-1 chitinase play an important part in the bifunctional chitinase / lysozyme activity.

• Korean Journal of Organic Agriculture
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• v.22 no.2
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• pp.303-319
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• 2014

The study researched germination of the plants and growth of experimented bacteria according to concentration of water extract in order to provide basic data for developing natural agricultural resources by using naturalized plants including Solidago altissima, Amaranthus retroflexus and Sida spinosa. As concentration of water extract increased, most of test plants showed a decrease in relative germinability. Sida spinosa(r=-0.540, p<0.01), Physalis wrightii(r=-0.693, p<0.01), Amaranthus retroflexu(r=-0.724, p<0.01), Solidago altissima(r=-0.728, p<0.01) and Eclipta prostrata(r=-0.779, p<0.01) showed tendency of decrease in relative germinative power in order, respectively. For average germination period, as concentration of the processed group increased, the time for germination increased (r = 0.769, p<0.01) and according to donor plants and test plants, there was a little difference. Also, as concentration of water extract of donor plant, length of above-aerial part(r=-0.587, p<0.01), length of underground part(r=-0.741, p<0.01), fresh weight(r=-0.574, p<0.01) and generation of root hair decreased. An then, for growth of test fungi according to concentration of water extract of donor plants, growths of Botrytis cinerea(r=-0.266, p<0.05), Diaporthe citri(r=-0.323 p<0.01), Colletotrichum gloeosporioides(r=-0.512, p<0.01), Pythiumultimum(r=-0.581, p<0.01) and Rhizoctonia solani(r=-0.806, p<0.01) were repressed in order, respectively. For total amount of content of phenol with herbicidal and Antifungal activities, S. altissima $17.3{\pm}0.5mg/g$, A. retroflexus $13.1{\pm}0.3mg/g$, P. wrightii $12.0{\pm}0.4mg/g$, S. spinosa $9.5{\pm}0.1mg/g$ and E. prostrata L. $4.1{\pm}0.1mg/g$ showed in order, respectively. As these results are summarized, donor plants which were naturalized, have competitive advantage because they release phenolic compounds with allelopathic effect and affect on germination, growth and fungi growth on underground flora compared to native plants and they have eligibility for natural herbicide and germicide.

• Microbiology and Biotechnology Letters
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• v.36 no.4
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• pp.268-275
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• 2008

In order to develop the multi-functional rhizobacteria that can exert positive effect on the growth of plants growing in the coastal sand dune located along East Coast of Korea, rhizospheral bacteria of 11 different plants from this area were isolated 1,330 rhizobacteria. Among these, 23 strains were able to produce auxin and had spectrum of antagonism toward various phytopathogenic microbes. To know the mechanism of this antifungal activity, these 23 strains were subjected to further analyses; 19 strains of these produced siderophore as determined by color reaction on CAS-blue plate, 4 strains produced antifungal cellulase as judged by color change on CMC-Congo red plate, 17 strains were able to utilized insoluble phosphate salts, also determined by clear zone formation on PVK medium. Identification of the strain was assigned to all 23 strains by l6s rDNA sequence analysed, and all were identified to be in the genus of Bacillus and Pseudomonas. One strain of these, denoted Pseudomonas fluorescens IB4-14, showed ACC deaminase activity which is known to be involved in the resistance of environmental stress such as salt and drought. Also, P. fluorescens IB4-l4 showed the germination stimulation and roots growth promoting activity on the in vivo assay of Lysimachia mauritiana Lam. (spoonleaf yellow loosestrife).