• The Korean Journal of Mycology
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• v.51 no.2
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• pp.141-146
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• 2023

Stem rot symptoms were observed in Gondre (Cirsium setidens) plants growing in a vinyl greenhouse in Taebaek, Korea during a disease survey in June 2022. The plants presented with dark brown to black rot on the stems at or above the soil line. Severely diseased plants displayed wilt and blight. Disease incidence among these plants ranged from 1 to 5%. Three isolates of Rhizoctonia sp. were obtained from the stem lesions of diseased plants. All isolates were identified as Rhizoctonia solani AG-2-2(IV) based on the morphological and cultural characteristics, results of the anastomosis test, and phylogenetic analysis. The pathogenicity of the isolates to Gondre plants was confirmed using an artificial inoculation test. The lesions induced by the inoculation test were similar to those observed in the investigated vinyl greenhouse. Here, we report a case of R. solani AG-2-2(IV) causing stem rot in Gondre.

• 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.

• Korean Journal Plant Pathology
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• v.14 no.3
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• pp.260-267
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• 1998

This study was undertaken to find a new formulation of soil amendment, and selection of antogonists and to effectively control brown and large patch of turfgrasses caused by Rhizoctoniz solani AG1-1 and AG 2-2. Fourteen inorgainc chemicals (1%, w/w) were added individually in vitro, and some chemicals showed suppressiveness to R. solani. Alum suppressed effectively mycelial growth of R. solani in the range of 17 to 77% as compared with control. The four chemicals such as Al2(SO4)3, alum, CaO, and NH4NO3 were finally selected. Out of three organic compounds, composted pine bark (CPB) showed prominent suppressive effect as compared with milled alfalfa and pine leaves. After inoculation of R. solani isolates AG-1 and AG2-2 on the turf seedlings, water soaked lesions and blight symptoms were developed on the whole seedlings. According to inhibition zone method, mycelial growth of the fungus were greatly suppressed by culture filterates of the antagonists, Gliocladium virens (Gl1-) and Pseudomonas sp. (P713). CPB soil amendment mixed with antagonists (1% w/w) controlled not only brown and large patch of turfgrasses, but also promote the good growth of the seedlings. In addition, the controlling effect was maintained more than 30 days. Especially, the controlling effect of two antagonists was similar to Cㅖㅠ soil amendment with the antagonists and also stimulated a favorable growth of the seedlings. Therefore, its is expected that continuous control of Rhizoctonia blight of turfgrasses can be obtained in field by subsequent applications of the antagonists.

• Journal of Microbiology and Biotechnology
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• v.5 no.6
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• pp.335-340
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• 1995

Two types of Rhizoctonia solani esterases induced by cutin hydrolysate were partially purified by ammonium sulfate precipitation and gel filtration. The esterase I with hydrolyzing activity toward both ${\rho}-ni-trophenyl$ butyrate and ${\rho}-nitrophenyl$ palmitate and the esterase II with hydrolyzing activity toward only ${\rho}-ni-trophenyl$ butyrate were inhibited by ebelactone B, an esterase inhibitor produced by actinomycetes with $IC_{50}$ values of 0.01 and $0.09{\;}\mu\textrm{g}/l$, respectively. Spraying on rice seedling with ebelactone B at a concentration of $30{\;}\mu\textrm{g}/ml$ completely suppressed infection by R. solani. Ebelactone B could not protect the wounded rice seedling and did not show any inhibitory effect on the mycelial growth at a concentration of 1 mg/ml. These results indicate that ebelactone B, an esterase inhibitor protects rice plants from infection with R. solani by inhibition of penetration, not through fungitoxic or fungicidal effect.

• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.437-441
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• 1990

For the genetic development of more powerful antagonistic Pseudomom - YPL-1 as a biocontxol agent against soilborne plant pathogenic Fuaarium solani causing root rot of many important crops, mutants improving the productivity of chitinase were obtained by mutation with UV radiation or NTG treatment, P. stutzeri YPL-M26 (UV mutant) and P. stutzeri YPL-MI78 (NTG mutant) could improve the productivity of chitinase by 2.5 and 2.0 times, and its antifungal activity by 1.7 and 1.5 times, respectively. The antifungal mechanism of P. stutzeri YPL-M26 was caused by lysis of the fungal cell wall by hydrolytic enzymes such as chitinase. The antifungal activity of crude chitinase of P. stutzeri YPLM26 on the mycelial growth of F. solani was observed to be much higher than that of the original strain. The enzymes produced by P. stutzeri YPL-M26 were the same as the original strain in enzymatic properties such as optimal pH and temperature.

• The Plant Pathology Journal
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• v.27 no.1
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• pp.68-77
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• 2011

Fifty five species of medicinal plant materials were tested for their antifungal activity in vitro against Rhizoctonia solani AG 2-1 and Trichoderma harzianum to select plant species that can be used to improve the biocontrol efficacy of T. harzianum. Six species were effective against R. solani AG 2-1 but were also antagonistic to T. harzianum, except for Cinnamomum loureirii stem bark (CSB). CSB inhibited mycelial growth of R. solani AG 2-1 by 73.7% but showed an inhibitory effect on mycelial growth of T. harzianum by only 2.2%. Scanning electron microscophs showed that the CSB treatment resulted in deformed R. solani AG 2-1 hyphal cells, and transmission electron microscophs revealed degenerated cell structures such as degenerated cytoplasm and disentangled cell wall and the accumulation of electron-dense inclusions (asterisks) in the CSB treatment. The biocontrol efficacy of radish damping-off increased greatly following the combined treatments of T. harzianum and CSB and the combined treatment increased efficacy from 6.4-23.1% to 37.1-87.3% compared with either treatment alone. CSB did not affect T. harzianum population growth, as it was almost the same in rice-bran peat medium (culture) amended with 0.1% and 1.0% CSB powder as in non-amended medium. The formulation of T. harzianum in rice-bran peat medium amended with CSB powder reduced the severity of radish damping-off by 80.6%, suggesting that T. harzianum and CSB can be formulated as a biocontrol product for the control of R. solani AG 2-1.

• Research in Plant Disease
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• v.18 no.1
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• pp.57-61
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• 2012

In March 2010, grafted cucumber cultivated in the greenhouse showed a severe rot on crown resulting yellowing and wilting of the leaves. The symptoms of naturally infected plants showed dark brown, watersoaked lesions at the base of the stem. The fungus produced mass of white mycelium and yellow to orange spores in necrotic lesions on dead and dying plants. Fungus was isolated from rotted tissues of the crown and root. On the basis of morphological characteristics, ITS sequence and pathogenicity tests, the isolate was identified as Fusarium solani f. sp. cucurbitae. This is the first report of the crown and foot rot of grafted cucumber caused by F. solani f. sp. cucurbitae in Korea.

• The Korean Journal of Pesticide Science
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• v.14 no.1
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• pp.65-71
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• 2010

This study was performed to investigate the inhibiting activity of etridiazole and thiophanate-mthyl on mycelial growth of Rhizoctonia solani and Pythium ultimum and the effect of inoculum density of each pathogen on the control efficacy of the mixture of etridiazole and thiophanate-methyl in a seedling assay test. In mycelial growth inhibition test, $EC_{50}$ values of etridiazole and thiophanate-methyl against R. solani were 15.87 and 9.34 ${\mu}g\;mL^{-1}$, while those were 0.2 and more than $500\;{\mu}g\;mL^{-1}$ against P. ultimum, respectively. Controlling activity of the mixture of etridiazole and thiophanate-methyl against damping-off of pepper and cucumber, caused by R. solani and P. ultimum was tested in a greenhouse. With the inoculation of R. solani, disease incidences of seedling in pepper were 73% and 95% at 0.5% and 1.0% of inoculum concentration, while in cucumber those were 55% and 62% at 1.0% and 2.0%. When P. ultimum was inoculated into soil by 2.0% of inoculum concentration, those in pepper and cucumber were 66.7% and 96.8%, respectively. The efficacy of the mixture was somehow affected by the concentration of R. solani. While each control value of the mixture was 94.4% and 90.7% in pepper and cucumber at low inoculum concentration (0.05%), the efficacy of the fungicide decreased in pepper and cucumber by 70.7% and 72.9% at high concentration of R. solani (0.1% in pepper and 0.5% in cucumber). However, the control value of the mixture was 100% in pepper and cucumber, irrespective of the inoculum concentration of P. ultimum, however, the increase of inoculum concentration in soil did not result in the decrease of the fungicide efficacy.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.4
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• pp.247-255
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• 2003

A bacterium, KJA-118 showing a strong chitinase activity, was isolated and identified as Bacillus cereus. The strain produced maximum level of chitinase, when grown aerobically at $30^{\circ}C$ for 4 days in basal broth containing 1% colloidal chitin in the initial pH adjusted to 6.0. Among various carbon sources such as crab shell powder, chitin powder, colloidal chitin, and R. solani mycelium, maximum chitinase activity was found in culture broth supplemented with R. solani mycelium. When KJA-118 was incubated with R. solani, the cell wall of the fungus was found to be completely destroyed. SDS-PAGE and active staining results revealed that KJA-118 produced three isoforms of chitinase with molecular weights of 68 kDa, 47 kDa, and 37 kDa. When the suspension of KJA-118 was treated to cucumber seedlings, reducing rate of damping-off caused by R. solani was about 28.1%.

• The Korean Journal of Mycology
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• v.45 no.1
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• pp.74-82
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• 2017

Lisianthus (Eustoma grandiflorum) is a flowering ornamental plant used widely in Korea. In 2015, wilting, damping-off, stunting, and root rot symptoms were observed in lisianthus plants of Yeoju and Gimhae, Korea. Affected seedlings appeared yellow and showed poor development of root systems in the field and in nursery boxes. Furthermore, affected plants were yellow, stunted, and died at approximately 2-3 months after transplanting. Fusarium species were consistently isolated from the basal stems of diseased plants. Nine isolates were identified as Fusarium solani based on morphological characteristics. Macroconidia of isolates were relatively wide, straight-to-slightly curved, and microconidia formed in false heads on long monophialides. Abundant chlamydospores were produced at the middle or tips of hyphae. To confirm this identification, a molecular analysis of the translation elongation factor 1 alpha (TEF) and RNA polymerase II subunit (RPB2) genes was conducted. The sequences of TEF and RPB2 showed 99.2-99.9% and 98.0-98.1% similarity, respectively, to those of reference F. solani strains in NCBI GenBank. Pathogenicity was tested using root dipping inoculation of healthy lisianthus seedlings. Symptoms were observed within 7 days of inoculation only in inoculated plants. This is the first report of F. solani causing Fusarium root rot on lisianthus in Korea.