• Asian Journal of Turfgrass Science
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• v.26 no.1
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• pp.8-16
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• 2012

The objective of this study was to identify bacterial antagonists of R. solani AG2-2 (IV) on zoysiagrass and to evaluate their antifungal activity in vitro and in vivo to select an antagonistic isolate. Antagonistic isolates that inhibit large patch disease caused by R. solani AG2-2 (IV) in zoysiagrass were selected from several soils, and their antagonistic activities were investigated in vitro and in vivo. Of 216 bacterial isolates, 67 inhibited several plant pathogenic fungi. The isolates that inhibited stem-segment colonization by R. solani AG2-2 (IV) in zoysiagrass were tested in a growth chamber. Eleven isolates were active as plant growth promoting isolates. Among them, five plant growth promoting isolates and their concentration dependent efficiency on zoysiagrass following inoculation with R. solani AG2-2 (IV) was evaluated. Isolate H33 was one of the potential antagonistic isolates, and it was further tested against various plant pathogens. H33 not only suppressed the disease caused by R. solani AG2-2 (IV) on zoysiagrass but also promoted leaf weight and leaf height of zoysiagrass under growth chamber and greenhouse conditions. The H33 isolate, which belongs to Streptomyces arenae, was identified through physiological, biochemical, and 16S rDNA studies. Further studies will investigate the cultural characterization of S. arenae H33 and isolation and identification of antifungal substance produced by S. arenae H33.

• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.220-223
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• 2004

Club root caused by Plasmodiophora brassicae is found in crucifers. Among the over hundreds of Streptomyces isolated from soil in Korea. One strain showed prominent activity against P. brassicae. The strain was identified based on 16S rDNA sequencing and the morphology by a method of scanning electron microscopy. An active compound in the fermented broth obtained from the strain was separated. Even though the complete assignments of the compound remain for future work, the results regarding the isolation and characterization of the strain with a certain activity against P. brassicae are shown in this paper.

• The Korean Journal of Pesticide Science
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• v.16 no.3
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• pp.209-216
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• 2012

In the continued research on natural fungicides for control of plant diseases by using plant-derived products, we found that Spatholobus suberectus Dunn had a strong fungicidal activity against several plant pathogens. S. suberectus (1 kg) was extracted with 80% aqueous MeOH and then the concentrated extract was partitioned with n-hexane, EtOAc, n-BuOH and $H_2O$ successively. The four layers were tested their disease contron efficacies against 6 plant diseases such as rice blast (RCB), rice sheath blight (RSB), tomato grey mold (TGM), tomato late blight (TLB), wheat leaf rust (WLR), and barley powdery mildew (BPM). The EtOAc fraction was highly active showing over 80% control against RCB, TGM, TLB, and BPM. By using silica gel chromatography, preparative TLC and HPLC, six compounds that were expected to have antifungal activity were separated. Their chemical structures were identified as ethanone, hydroxytyrosol, epicatechin, procyanidin B2, dimethoxy daizein and formononetin by ESI-MS, $^1H$-NMR, $^{13}C$-NMR, and 2D-NMR spectroscopic analyses. The chemicals except epicatechin were first reported in S. suberectus. Study on in vitro and in vivo antifungal activities of the isolated compounds is in progress.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1402-1407
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• 2005

The fungicidal activities of Coptis japonica (Makino) extracts and their active principles were determined against Botrytis cineria, Erysiphe graminis, Phytophthora infestans, Puccinia recondita, Pyricularia grisea, and Rhizoctonia solani using a whole plant method in vivo, and compared with natural fungicides. The responses varied according to the plant pathogen tested. At 2,000 mg/l, the chloroform and butanol fractions obtained from methanolic extracts of C. japonica exhibited strong/moderate fungicidal activities against B. cinerea, E. graminis, P. recondita, and Py. grisea. Two active constituents from the chloroform fractions and one active constituent from the butanol fractions were characterized as isoquinoline alkaloids, berberine chloride, palmatine iodide, and coptisine chloride, respectively, using spectral analysis. Berberine chloride had an apparent $LC_{50}$ value of approximately 190, 80, and 50 mg/l against B. cinerea, E. graminis, and P. recondita, respectively; coptisine chloride had an $LC_{50}$ value of 210,20, 180, and 290 mg/l against B. cinerea, E. graminis, P. recondita, and Py. grisea, respectively; and palmatine iodide had an $LC_{50}$ value of 160 mg/l against Py. grisea. The isoquinoline alkaloids were also found to be more potent than the natural fungicides, curcumin and emodin. Therefore, these compounds isolated from C. japonica may be useful leads for the development of new types of natural fungicides for controlling B. cinerea, E. graminis, P. recondita, and Py. grisea in crops.

• The Korean Journal of Pesticide Science
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• v.11 no.4
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• pp.313-319
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• 2007

Nine plant growth regulators (PGRs) were tested for in vivo antifungal activities against on rice blast. They showed higher in vivo antifungal activities when they were applied on rice plants by soil drench rather than foliar spray. Except for 2,4-D at $500\;{\mu}g\;mL^{-1}$, the others showed a very low or no activity against the disease in foliar spray applications. In contrast, 2,4-D, indole butyric acid (IBA) and triiodobenzoic acid, at $500\;{\mu}g\;mL^{-1}$, showed control values of 98.9, 97.8 and 88.9% in soil drench applications. Furthermore, the control activity of IBA was dependent on its concentration against rice blast; IBA suppressed the development of rice blast by 71.7% at $125\;{\mu}g\;mL^{-1}$ and 85.8% at $250\;{\mu}g\;mL^{-1}$. IBA also controlled the development of rice blast on adult plants by 63.9% at a dosage of 2.56 kg/10a. The results revealed that IBA has a good activity against rice blast when it is applied by soil drench.

• 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.

• Applied Biological Chemistry
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• v.45 no.3
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• pp.157-161
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• 2002

New 2-benzoylimino-1,3-oxathile derivatives 3 were synthesized and tested their fungicidal activities for the development of new agrochemical fungicide. Reaction of ${\gamma}-chloro-{\beta}-keto$ anilide derivative 5 with potassium thiocyanate followed by the treatment of acid catalyst gave cyclyzed 2-imino-1,3-oxathiole 3. New compound 3 reacted with benzoyl· chlorides to afford the corresponding 2-benzoylimino-1,3-oxathiole derivatives 7. Antifungal screening (in vivo) of the synthesized compounds against typical plant diseases, which include rice blast, rice sheath blight, cucumber gray mold, tomato late blight, wheat leaf rust, and barley powdery mildew, was carried out. No significant fungicidal activities were shown of the synthesized compounds at 100 mg/l.

• Research in Plant Disease
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• v.18 no.1
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• pp.10-16
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• 2012

This study was conducted to examine the effects of the seeding rate on the disease incidence of sharp eyespot(Rhizoctonia cerealis) on three different varieties and to select effective chemicals to control the disease. When the seeds were sown twice as many as the recommendation, the disease incidence increased by approximately 13%. However, the susceptible variety 'Jopummil' alone showed the significantly enhanced disease incidence at a two-fold seeding rate. Two chemicals such as Hexaconazole EC and Tebuconazole EC highly inhibited the fungal growth on agar medium. However, two strobilurin fungicides such as Pyraclostrobin EC and Trifloxystrobin SC were relatively weak. The fungicides tested displayed the similar in vivo antifungal activities as in vitro activities. Hexaconazole EC and Tebuconazole EC showed the strongest both protective and curative activities and the protective activities of the chemicals were generally higher than the curative activities. Hexaconazole EC and Tebuconazole EC controlled the disease by 64% and 73%, respectively, and the two chemicals reduced the disease by 45% and 39%, respectively, when they were applied one day after pathogen inoculation. These results indicate that both Hexaconazole EC and Tebuconazole EC could be used to control sharp eyespot on wheat.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1223-1229
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• 2009

To construct a new recombinant strain of Bacillus velezensis that has antifungal and insecticidal activity via the expression of the insecticidal Bacillus thuringiensis crystal protein, a B. thuringiensis expression vector (pHT1K-1Ac) was generated that contained the B. thuringiensis cry1Ac gene under the control of its endogenous promoter in a minimal E. coli-B. thuringiensis shuttle vector (pHT1K). This vector was introduced into a B. velezensis isolate that showed high antifungal activities against several plant diseases, including rice blast (Magnaporthe grisea), rice sheath blight (Rhizotonia solani), tomato gray mold (Botrytis cinerea), tomato late blight (Phytophthora infestans), and wheat leaf rust (Puccinia recondita), by electroporation. The recombinant B. velezensis strain was confirmed by PCR using cry1Ac-specific primers. Additionally, the recombinant strain produced a protein approximately 130 kDa in size and parasporal inclusion bodies similar to B. thuringiensis. The in vivo antifungal activity assay demonstrated that the activity of the recombinant B. velezensis strain was maintained at the same level as that of wild-type B. velezensis. Furthermore, it exhibited high insecticidal activity against a lepidopteran pest, Plutella xylostella, although its activity was lower than that of a recombinant B. thuringiensis strain, whereas wild-type B. velezensis strain did not show any insecticidal activity. These results suggest that this recombinant B. velezensis strain can be used to control harmful insect pests and fungal diseases simultaneously in one crop.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.3
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• pp.251-258
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• 2016

A rhizobacterium LPN-2, which showed strong antifungal activity and auxin producing ability, was isolated from a farmland in North Gyeongsang Province, South Korea. Based on analysis of the 16S rDNA sequence, strain LPN-2 was identified as a novel strain of Burkholderia and was designated as Burkholderia sp. LPN-2. In vitro experiments showed that the isolated stain LPN-2 significantly produced auxin within 48 hr incubation. In order to check for PGPR function we performed in vivo growth promoting test in different crops, including mung bean, pea and cabbage. Application of Burkholderia sp. LPN-2 showed dramatic growth promoting effect on all the tested plants. We also confirmed siderophore and cellulase productions by Burkholderia sp. LPN-2 using CAS blue agar and CMC plate test. Further treatment with LPN-2 and the crude culture broth was effective in suppressing anthracnose in vitro test and also reduced incidence and severity of anthracnose in apple and pepper. Taken together, we conclude that Burkholderia sp. LPN-2 might be used as organic fertilizer for effective crop production in organic farming.