The Experts below are selected from a list of 2172 Experts worldwide ranked by ideXlab platform
M J Bailey - One of the best experts on this subject based on the ideXlab platform.
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chromosomal insertion of phenazine 1 carboxylic acid biosynthetic pathway enhances efficacy of Damping off Disease control by pseudomonas fluorescens
Molecular Plant-microbe Interactions, 2000Co-Authors: T M Timmswilson, R J Ellis, D Rhodes, A Renwick, Dmitri V Mavrodi, David M Weller, Linda S Thomashow, M J BaileyAbstract:A disarmed Tn5 vector (pUT∷Ptac-phzABCDEFG) was used to introduce a single copy of the genes responsible for phenazine-1-carboxylic acid (PCA) biosynthesis into the chromosome of a plant-growth-promoting rhizobacterium Pseudomonas fluorescens. The PCA gene cluster was modified for expression under a constitutive Ptac promoter and lacked the phzIR regulators. PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce Damping-off Disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation. Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures. Similarly, when the in vitro nutrient supply was limited, P. fluorescens∷phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development. Soil-based bioassays confirmed that the level of PCA biosynthesis correlated...
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ecological basis for biocontrol of Damping off Disease by pseudomonas fluorescens 54 96
Journal of Applied Microbiology, 1999Co-Authors: R J Ellis, T M Timmswilson, John E Beringer, D Rhodes, A Renwick, L Stevenson, M J BaileyAbstract:Pseudomonas fluorescens 54/96, originally isolated from the rhizosphere of sugar beet, has been shown to be commercially effective in field trials for the suppression of a number of fungal Diseases of seedlings. In vitro and microcosm-based assays revealed that both the timing and method of application of bacteria were important for effective control of Pythium ultimum, the causative agent of Damping-off Disease. Following transposon mutagenesis (Tn5lac), mutants deficient for the suppression of Pythium ultimum infections of peas were isolated. Three major classes of insertional mutants of Ps. fluorescens 54/96 were identified which either inhibited sporulation, reduced mycelial growth or affected the regulation of bacterial metabolic activity. Evaluation of the metabolic capability of pathogen and antagonist revealed evidence for direct competition, as both the fungus and bacterium had similar sole carbon source nutrient utilization profiles. Further comparisons of the activity of the transposon mutants indicated that although the mechanisms of Disease control were multifactorial, the most significant factor was the prevention of rapid spore germination in the presence of pea seeds.
Susan L Hamilton - One of the best experts on this subject based on the ideXlab platform.
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role of essential oils in control of rhizoctonia Damping off in tomato with bioactive monarda herbage
Phytopathology, 2010Co-Authors: Kimberley D. Gwinn, Sharon E Greene, Miranda M Clark, Chelsea L Taylor, Tiffany N Springfield, David Trently, James F Green, Ann Reed, Bonnie H Ownley, Susan L HamiltonAbstract:Plants in the genus Monarda produce complex essential oils that contain antifungal compounds. The objectives of this research were to identify selections of monarda that reduce Rhizoctonia Damping-off of tomato, and to determine relationships between essential oil composition of 13 monarda herbages (dried and ground leaves) and Disease suppression. Herbages were grouped into five chemotypes, based on essential oil composition and effective concentrations for reducing growth by 50% for Rhizoctonia solani. Replicated and repeated Disease control assays were conducted with monarda herbages in greenhouse medium, with or without Rhizoctonia. Percent survival, seedling height, and stem diameter were evaluated at 8 weeks. Survival, seedling height, and stem diameter in herbage-only treatments were not different from the control (no-herbage, no-pathogen) for most herbage treatments. In the pathogen control (no-herbage + Rhizoctonia), seedling survival was 10% that of the control. In pathogen-infested media, seedling survival ranged from 65 to 80% for treatments with thymol chemotypes and 55 to 65% for carvacrol chemotypes. Effective control of Rhizoctonia Damping-off was correlated with phenolic monoterpenes; herbages classified as carvacrol chemotypes effectively protected tomato seedlings from Rhizoctonia Damping-off Disease without phytotoxicity. This study provides evidence that monarda herbages have potential as growing media amendments for control of Rhizoctonia Damping-off Disease.
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role of essential oils in control of rhizoctonia Damping off in tomato with bioactive monarda herbage
Phytopathology, 2010Co-Authors: Kimberley D. Gwinn, Sharon E Greene, Miranda M Clark, Chelsea L Taylor, Tiffany N Springfield, David Trently, James F Green, Ann Reed, Bonnie H Ownley, Susan L HamiltonAbstract:Plants in the genus Monarda produce complex essential oils that contain antifungal compounds. The objectives of this research were to identify selections of monarda that reduce Rhizoctonia Damping-off of tomato, and to determine relationships between essential oil composition of 13 monarda herbages (dried and ground leaves) and Disease suppression. Herbages were grouped into five chemotypes, based on essential oil composition and effective concentrations for reducing growth by 50% for Rhizoctonia solani. Replicated and repeated Disease control assays were conducted with monarda herbages in greenhouse medium, with or without Rhizoctonia. Percent survival, seedling height, and stem diameter were evaluated at 8 weeks. Survival, seedling height, and stem diameter in herbage-only treatments were not different from the control (no-herbage, no-pathogen) for most herbage treatments. In the pathogen control (no-herbage + Rhizoctonia), seedling survival was 10% that of the control. In pathogen-infested media, seedling survival ranged from 65 to 80% for treatments with thymol chemotypes and 55 to 65% for carvacrol chemotypes. Effective control of Rhizoctonia Damping-off was correlated with phenolic monoterpenes; herbages classified as carvacrol chemotypes effectively protected tomato seedlings from Rhizoctonia Damping-off Disease without phytotoxicity. This study provides evidence that monarda herbages have potential as growing media amendments for control of Rhizoctonia Damping-off Disease.
D Rhodes - One of the best experts on this subject based on the ideXlab platform.
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chromosomal insertion of phenazine 1 carboxylic acid biosynthetic pathway enhances efficacy of Damping off Disease control by pseudomonas fluorescens
Molecular Plant-microbe Interactions, 2000Co-Authors: Tracey M Timmswilson, D Rhodes, A Renwick, Dmitri V Mavrodi, David M Weller, Linda S Thomashow, Richard J Ellis, Mark J BaileyAbstract:A disarmed Tn5 vector (pUT::Ptac-phzABCDEFG) was used to introduce a single copy of the genes responsible for phenazine-1-carboxylic acid (PCA) biosynthesis into the chromosome of a plant-growth-promoting rhizobacterium Pseudomonas fluorescens. The PCA gene cluster was modified for expression under a constitutive Ptac promoter and lacked the phzIR regulators. PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce Damping-off Disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation. Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures. Similarly, when the in vitro nutrient supply was limited, P fluorescens::phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development. Soil-based bioassays confirmed that the level of PCA biosynthesis correlated directly with the efficacy of biological control and the persistence of inocula in soil microcosms. They also showed that soil pretreatment with bacteria provides a suitable method for plant protection by reducing infection, effectively decontaminating the soil. These data demonstrate that the insertion of a single chromosomal copy of the genes for a novel antifungal compound, PCA, enhances the ecological fitness of a natural isolate already adapted to the rhizosphere and capable of suppressing fungal Disease.
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chromosomal insertion of phenazine 1 carboxylic acid biosynthetic pathway enhances efficacy of Damping off Disease control by pseudomonas fluorescens
Molecular Plant-microbe Interactions, 2000Co-Authors: T M Timmswilson, R J Ellis, D Rhodes, A Renwick, Dmitri V Mavrodi, David M Weller, Linda S Thomashow, M J BaileyAbstract:A disarmed Tn5 vector (pUT∷Ptac-phzABCDEFG) was used to introduce a single copy of the genes responsible for phenazine-1-carboxylic acid (PCA) biosynthesis into the chromosome of a plant-growth-promoting rhizobacterium Pseudomonas fluorescens. The PCA gene cluster was modified for expression under a constitutive Ptac promoter and lacked the phzIR regulators. PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce Damping-off Disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation. Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures. Similarly, when the in vitro nutrient supply was limited, P. fluorescens∷phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development. Soil-based bioassays confirmed that the level of PCA biosynthesis correlated...
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ecological basis for biocontrol of Damping off Disease by pseudomonas fluorescens 54 96
Journal of Applied Microbiology, 1999Co-Authors: R J Ellis, T M Timmswilson, John E Beringer, D Rhodes, A Renwick, L Stevenson, M J BaileyAbstract:Pseudomonas fluorescens 54/96, originally isolated from the rhizosphere of sugar beet, has been shown to be commercially effective in field trials for the suppression of a number of fungal Diseases of seedlings. In vitro and microcosm-based assays revealed that both the timing and method of application of bacteria were important for effective control of Pythium ultimum, the causative agent of Damping-off Disease. Following transposon mutagenesis (Tn5lac), mutants deficient for the suppression of Pythium ultimum infections of peas were isolated. Three major classes of insertional mutants of Ps. fluorescens 54/96 were identified which either inhibited sporulation, reduced mycelial growth or affected the regulation of bacterial metabolic activity. Evaluation of the metabolic capability of pathogen and antagonist revealed evidence for direct competition, as both the fungus and bacterium had similar sole carbon source nutrient utilization profiles. Further comparisons of the activity of the transposon mutants indicated that although the mechanisms of Disease control were multifactorial, the most significant factor was the prevention of rapid spore germination in the presence of pea seeds.
A Renwick - One of the best experts on this subject based on the ideXlab platform.
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chromosomal insertion of phenazine 1 carboxylic acid biosynthetic pathway enhances efficacy of Damping off Disease control by pseudomonas fluorescens
Molecular Plant-microbe Interactions, 2000Co-Authors: Tracey M Timmswilson, D Rhodes, A Renwick, Dmitri V Mavrodi, David M Weller, Linda S Thomashow, Richard J Ellis, Mark J BaileyAbstract:A disarmed Tn5 vector (pUT::Ptac-phzABCDEFG) was used to introduce a single copy of the genes responsible for phenazine-1-carboxylic acid (PCA) biosynthesis into the chromosome of a plant-growth-promoting rhizobacterium Pseudomonas fluorescens. The PCA gene cluster was modified for expression under a constitutive Ptac promoter and lacked the phzIR regulators. PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce Damping-off Disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation. Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures. Similarly, when the in vitro nutrient supply was limited, P fluorescens::phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development. Soil-based bioassays confirmed that the level of PCA biosynthesis correlated directly with the efficacy of biological control and the persistence of inocula in soil microcosms. They also showed that soil pretreatment with bacteria provides a suitable method for plant protection by reducing infection, effectively decontaminating the soil. These data demonstrate that the insertion of a single chromosomal copy of the genes for a novel antifungal compound, PCA, enhances the ecological fitness of a natural isolate already adapted to the rhizosphere and capable of suppressing fungal Disease.
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chromosomal insertion of phenazine 1 carboxylic acid biosynthetic pathway enhances efficacy of Damping off Disease control by pseudomonas fluorescens
Molecular Plant-microbe Interactions, 2000Co-Authors: T M Timmswilson, R J Ellis, D Rhodes, A Renwick, Dmitri V Mavrodi, David M Weller, Linda S Thomashow, M J BaileyAbstract:A disarmed Tn5 vector (pUT∷Ptac-phzABCDEFG) was used to introduce a single copy of the genes responsible for phenazine-1-carboxylic acid (PCA) biosynthesis into the chromosome of a plant-growth-promoting rhizobacterium Pseudomonas fluorescens. The PCA gene cluster was modified for expression under a constitutive Ptac promoter and lacked the phzIR regulators. PCA-producing variants significantly improved the ability of the wild-type P. fluorescens to reduce Damping-off Disease of pea seedlings caused by Pythium ultimum, even under conditions of heavy soil infestation. Under conditions of oxygen limitation that are typical of the rhizosphere, PCA production per cell in vitro was greater than that recorded in fast-growing, nutrient-rich cultures. Similarly, when the in vitro nutrient supply was limited, P. fluorescens∷phz variants that produced the most PCA effectively competed against P. ultimum by suppressing mycelial development. Soil-based bioassays confirmed that the level of PCA biosynthesis correlated...
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ecological basis for biocontrol of Damping off Disease by pseudomonas fluorescens 54 96
Journal of Applied Microbiology, 1999Co-Authors: R J Ellis, T M Timmswilson, John E Beringer, D Rhodes, A Renwick, L Stevenson, M J BaileyAbstract:Pseudomonas fluorescens 54/96, originally isolated from the rhizosphere of sugar beet, has been shown to be commercially effective in field trials for the suppression of a number of fungal Diseases of seedlings. In vitro and microcosm-based assays revealed that both the timing and method of application of bacteria were important for effective control of Pythium ultimum, the causative agent of Damping-off Disease. Following transposon mutagenesis (Tn5lac), mutants deficient for the suppression of Pythium ultimum infections of peas were isolated. Three major classes of insertional mutants of Ps. fluorescens 54/96 were identified which either inhibited sporulation, reduced mycelial growth or affected the regulation of bacterial metabolic activity. Evaluation of the metabolic capability of pathogen and antagonist revealed evidence for direct competition, as both the fungus and bacterium had similar sole carbon source nutrient utilization profiles. Further comparisons of the activity of the transposon mutants indicated that although the mechanisms of Disease control were multifactorial, the most significant factor was the prevention of rapid spore germination in the presence of pea seeds.
Satoshi Tahara - One of the best experts on this subject based on the ideXlab platform.
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suppression of Damping off Disease in host plants by the rhizoplane bacterium lysobacter sp strain sb k88 is linked to plant colonization and antibiosis against soilborne peronosporomycetes
Applied and Environmental Microbiology, 2005Co-Authors: Md Tofazzal Islam, Yasuyuki Hashidoko, Abhinandan Deora, Toshiaki Ito, Satoshi TaharaAbstract:ABSTRACT We previously demonstrated that xanthobaccin A from the rhizoplane bacterium Lysobacter sp. strain SB-K88 suppresses Damping-off Disease caused by Pythium sp. in sugar beet. In this study we focused on modes of Lysobacter sp. strain SB-K88 root colonization and antibiosis of the bacterium against Aphanomyces cochlioides, a pathogen of Damping-off Disease. Scanning electron microscopic analysis of 2-week-old sugar beet seedlings from seeds previously inoculated with SB-K88 revealed dense colonization on the root surfaces and a characteristic perpendicular pattern of Lysobacter colonization possibly generated via development of polar, brush-like fimbriae. In colonized regions a semitransparent film apparently enveloping the root and microcolonies were observed on the root surface. This Lysobacter strain also efficiently colonized the roots of several plants, including spinach, tomato, Arabidopsis thaliana, and Amaranthus gangeticus. Plants grown from both sugar beet and spinach seeds that were previously treated with Lysobacter sp. strain SB-K88 displayed significant resistance to the Damping-off Disease triggered by A. cochlioides. Interestingly, zoospores of A. cochlioides became immotile within 1 min after exposure to a SB-K88 cell suspension, a cell-free supernatant of SB-K88, or pure xanthobaccin A (MIC, 0.01 μg/ml). In all cases, lysis followed within 30 min in the presence of the inhibiting factor(s). Our data indicate that Lysobacter sp. strain SB-K88 has a direct inhibitory effect on A. cochlioides, suppressing Damping-off Disease. Furthermore, this inhibitory effect of Lysobacter sp. strain SB-K88 is likely due to a combination of antibiosis and characteristic biofilm formation at the rhizoplane of the host plant.
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interaction between rhizoplane bacteria and a phytopathogenic peronosporomycete aphanomyces cochlioides in relation to the suppression of Damping off Disease in sugar beet and spinach
Bulletin OILB SROP, 2004Co-Authors: Md Tofazzal Islam, Yasuyuki Hashidoko, Abhinandan Deora, Toshiaki Ito, Satoshi TaharaAbstract:We investigated the modes of root colonization and antibiosis of Lysobacter sp. strain SBK88 and other rhizoplane bacteria of spinach and sugar beet antagonizing a Peronosporomycete pathogen, Aphanomyces cochlioides. The SB-K88 has huge long brush-like fimbriae at one pole of the sessile bacterial rod. Scanning electron microscope (SEM) analysis of two weeks old seedlings of sugar beet and spinach upon inoculation of seeds revealed that SB-K88 densely colonized to the root and cotyledon surfaces of plants in a perpendicular fashion using polar fimbriae and developed biofilm-like structures on roots covered by root mucigel. Seed treated with either SB-K88 or its culture fluids significantly suppressed Damping-off Disease in both sugar beet and spinach caused by A. cochlioides. In dual culture assay, SB-K88 and other rhizoplane bacteria caused excessive branching, swelling and loss of radial growth in the approaching hyphae of A. cochlioides. TEM also visualized remarkable ultrastructural alterations in the affected hyphae. Interestingly, zoospores of A. cochlioides, were rendered immotile within 1 min of exposure to cell suspension or cell free culture supernatant or EtOAc extracts or pure xanthobaccin A (1) isolated from SB-K88, and subsequent lysis occurred within 30 min. Our observations provide the convincing evidence that Lysobacter sp. exerts a direct inhibitory effect on A. cochlioides and suppresses Damping-off Disease in sugar beet and spinach through a combination of antibiosis and high root colonization.
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possible role of xanthobaccins produced by stenotrophomonas sp strain sb k88 in suppression of sugar beet Damping off Disease
Applied and Environmental Microbiology, 1999Co-Authors: Takato Nakayama, Yasuyuki Hashidoko, Yoshihisa Homma, Junya Mizutani, Satoshi TaharaAbstract:Three antifungal compounds, designated xanthobaccins A, B, and C, were isolated from the culture fluid of Stenotrophomonas sp. strain SB-K88, a rhizobacterium of sugar beet that suppresses Damping-off Disease. Production of xanthobaccin A in culture media was compared with the Disease suppression activities of strain SB-K88 and less suppressive strains that were obtained by subculturing. Strain SB-K88 was applied to sugar beet seeds, and production of xanthobaccin A in the rhizosphere of seedlings was confirmed by using a test tube culture system under hydroponic culture conditions; 3 mg of xanthobaccin A was detected in the rhizosphere on a per-plant basis. Direct application of purified xanthobaccin A to seeds suppressed Damping-off Disease in soil naturally infested by Pythium spp. We suggest that xanthobaccin A produced by strain SB-K88 plays a key role in suppression of sugar beet Damping-off Disease. Damping-off Disease in sugar beet seedlings is caused by a number of soilborne plant pathogens, including Rhizoctonia solani, Pythium ultimum, and Aphanomyces cochlioides .I t is one of the most serious Diseases affecting sugar beet production in Japan. Biological control with antagonistic microorganisms has been investigated as a possible means of controlling the Disease (17, 19, 20, 23, 25). Homma et al. (10) reported that when applied as a seed coating, a rhizobacterium of sugar beet, strain SB-K88, suppressed seedling Damping-off Disease almost as effectively as conventional chemical control. Based on certain bacterial characteristics (lack of an umbonate colony form, no growth on a medium containing 4% sodium chloride and 0.1% triphenyl tetrazolium chloride), strain SB-K88 was considered a member of a Stenotrophomonas species (formerly classified as a Xanthomonas species) but not Stenotrophomonas maltophilia (8). It became apparent in the course of investigating the mechanism of Disease suppression by strain SB-K88 that this bacterium produces some antifungal substances that are effective in vitro against fungi that cause Damping-off Disease (18). Because antibiotics are thought to play a major role in Disease suppression by rhizobacteria (14, 21), we focused on the relationship between the production of antifungal substances in the culture medium and in the rhizosphere of sugar beet by this strain and the suppression of Damping-off Disease. We first isolated three antifungal compounds, xanthobaccin A (XB-A), XB-B, and XB-C, from the culture fluid of strain SB-K88. The chemical structure of XB-A was reported recently and is shown in Fig. 1 (6). This compound is a macrocyclic lactam that has a unique 5,5,6-tricyclic skeleton (tricyclo [7.3.0.0 2,7 ]dodecane) and a tetramic acid moiety as a putative chromophore; the plane structure is the same as that of maltophilin, which is produced by S. maltophilia (12). In order to clarify the role of xanthobaccins in Disease suppression, we investigated the relationship between the production of XB-A (the major antifungal compound) in vitro and the degree of Disease suppression by using less suppressive (LS) strains derived from strain SB-K88. In this paper we also describe the detection and quantification of XB-A produced by strain SBK88 in the rhizosphere of sugar beet seedlings by using a test tube culture system and Disease suppression by XB-A applied directly to sugar beet seeds.
