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Yvan Moënne-loccoz - One of the best experts on this subject based on the ideXlab platform.

  • Rhizosphere ecology and phytopRotection in soils naturally suppressive to Thielaviopsis Black Root Rot of tobacco
    Environmental Microbiology, 2014
    Co-Authors: Juliana Almario, Daniel Muller, Geneviève Défago, Yvan Moënne-loccoz
    Abstract:

    Soil suppressiveness to disease is an intriguing emerging property in agroecosystems, with important implications because it enables significant pRotection of susceptible plants from soil-borne pathogens. Unlike many soils where disease suppressiveness requires crop monoculture to establish, certain soils are naturally suppressive to disease, and this type of specific disease suppressiveness is maintained despite crop Rotation. Soils naturally suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco and other crops occur in Morens region (Switzerland) and have been studied for over 30 years. In Morens, vermiculite-rich suppressive soils formed on morainic deposits while illite-rich conducive soils developed on sandstone, but suppressiveness is of microbial origin. Antagonistic pseudomonads play a role in Black Root Rot suppressiveness, including Pseudomonas pRotegens (formerly P. fluorescens) CHA0, a major model strain for research. However, other types of rhizobacterial taxa may differ in prevalence between suppressive and conducive soils, suggesting that the microbial basis of Black Root Rot suppressiveness could be far more complex than solely a Pseudomonas property. This first review on Black Root Rot suppressive soils covers early findings on these soils, the significance of recent results, and compares them with other types of suppressive soils in terms of rhizosphere ecology and plant pRotection mechanisms.

  • Evaluation of rhizobacterial indicators of tobacco Black Root Rot suppressiveness in farmers' fields
    Environmental Microbiology Reports, 2014
    Co-Authors: Martina Kyselková, Daniel Muller, Juliana Almario, Jan Kopecký, Markéta Ságová-marečková, Jacqueline Haurat, Geneviève L. Grundmann, Yvan Moënne-loccoz
    Abstract:

    Very few soil quality indicators include disease-suppressiveness criteria. We assessed whether 64 16S rRNA microarray probes whose signals correlated with tobacco Black Root Rot suppressiveness in greenhouse analysis could also discriminate suppressive from conducive soils under field conditions. Rhizobacterial communities of tobacco and wheat sampled in 2 years from four farmers' fields of contrasted suppressiveness status were compared. The 64 previously identified indicator probes correctly classified 72% of 29 field samples, with nine probes for Azospirillum, Gluconacetobacter, Sphingomonadaceae, Planctomycetes, Mycoplasma, Lactobacillus crispatus and Thermodesulforhabdus providing the best prediction. The whole probe set (1033 probes) revealed strong effects of plant, field location and year on rhizobacterial community composition, and a smaller (7% variance) but significant effect of soil suppressiveness status. Seventeen additional probes correlating with suppressiveness status in the field (noticeably for Agrobacterium, Methylobacterium, Ochrobactrum) were selected, and combined with the nine others, they improved correct sample classification from 72% to 79% (100% tobacco and 63% wheat samples). Pseudomonas probes were not informative in the field, even those targeting biocontrol pseudomonads producing 2,4-diacetylphloroglucinol, nor was quantitative polymerase chain reaction for 2,4-diacetylphloroglucinol-synthesis gene phlD. This study shows that a subset of 16S rRNA probes targeting diverse rhizobacteria can be useful as suppressiveness indicators under field conditions.

  • Assessment of the relationship between geologic origin of soil, rhizobacterial community composition and soil receptivity to tobacco Black Root Rot in Savoie region (France)
    Plant and Soil, 2013
    Co-Authors: Juliana Almario, Daniel Muller, Martina Kyselková, Jan Kopecký, Markéta Ságová-marečková, Geneviève L Grundmann, Yvan Moënne-loccoz
    Abstract:

    Background and aims In Morens (Switzerland), soils formed on morainic deposits (which contain vermiculite clay and display particular tobacco rhizobacterial community) are naturally suppressive to Thielaviopsis basicola-mediated tobacco Black Root Rot, but this paradigm was never assessed elsewhere. Here, we tested the relation between geology and disease suppressiveness in neighboring Savoie (France).

  • Assessment of the relationship between geologic origin of soil, rhizobacterial community composition and soil receptivity to tobacco Black Root Rot in Savoie region (France)
    Plant and Soil, 2013
    Co-Authors: Juliana Almario, Daniel Muller, Martina Kyselková, Jan Kopecký, Markéta Ságová-marečková, Geneviève L. Grundmann, Yvan Moënne-loccoz
    Abstract:

    Background and aims In Morens (Switzerland), soils formed on morainic deposits (which contain vermiculite clay and display particular tobacco rhizobacterial community) are naturally suppressive to Thielaviopsis basicola-mediated tobacco Black Root Rot, but this paradigm was never assessed elsewhere. Here, we tested the relation between geology and disease suppressiveness in neighboring Savoie (France). Methods Two morainic and two sandstone soils from Savoie were compared based on disease receptivity (T. basicola inoculation tests on tobacco), clay mineralogy (X-ray diffraction), tobacco rhizobacterial community composition (16S rRNA gene-based taxonomic microarray) and phlD + Pseudomonas populations involved in 2,4-diacetylphloroglucinol production (real-time PCR and tRFLP). Results Unlike in Morens, in Savoie the morainic soils were receptive to disease whereas T. basicola inoculation did not increase disease level in the sandstone soils. Vermiculite was not present in Savoie soils. The difference in rhizobacterial community composition between Savoie morainic and sandstone soils was significant but modest, and there was little agreement in bacterial taxa discriminating soils of different disease receptivity levels when comparing Morens versus Savoie soils. Finally, phlD + rhizosphere pseudomonads were present at levels comparable to those in Morens soils, but with different diversity patterns. Conclusions The morainic model of Black Root Rot suppressiveness might be restricted to the particular type of moraine occurring in the Morens region, and the low disease receptivity of sandstone soils in neighboring Savoie might be related to other plant-pRotection mechanisms.

  • Denaturing gradient gel electrophoretic analysis of dominant 2,4-diacetylphloroglucinol biosynthetic phlD alleles in fluorescent Pseudomonas from soils suppressive or conducive to Black Root Rot of tobacco
    Soil Biology and Biochemistry, 2010
    Co-Authors: Michele Frapolli, Geneviève Défago, Yvan Moënne-loccoz
    Abstract:

    In Switzerland, similar types of rhizosphere pseudomonads producing the biocontrol compound 2,4- diacetylphloroglucinol (Phl) have been found in soils suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco as well as in conducive soils. However, most findings were based on the analysis of a limited number of Pseudomonas isolates, obtained from a single experiment and only from T. basicolainoculated plants. Here, an approach based on denaturing gradient gel electrophoresis (DGGE) of dominant phlD alleles from tobacco rhizosphere provided different phlD migration patterns. Sequencing of phlD-DGGE bands revealed a novel phylogenetic cluster of phlD sequences found in both suppressive and conducive soils in addition to previously-documented phlD alleles. phlD-DGGE bands and alleles differed little from one plant to the next but more extensively from one sampling to the next during the three-year study. Three of the 13 bands and 12 of the 31 alleles were only found in suppressive soil, whereas five bands and 13 alleles were found exclusively in conducive soil. The population structure of phlDþ pseudomonads depended more on the individual soil considered and its suppressiveness status than on inoculation of tobacco with T. basicola. In conclusion, phlD-DGGE revealed additional phlD diversity compared with earlier analyses of individual Pseudomonas isolates, and showed differences in phlDþ Pseudomonas population structure in relation to disease suppressiveness.

Juliana Almario - One of the best experts on this subject based on the ideXlab platform.

  • Rhizosphere ecology and phytopRotection in soils naturally suppressive to Thielaviopsis Black Root Rot of tobacco
    Environmental Microbiology, 2014
    Co-Authors: Juliana Almario, Daniel Muller, Geneviève Défago, Yvan Moënne-loccoz
    Abstract:

    Soil suppressiveness to disease is an intriguing emerging property in agroecosystems, with important implications because it enables significant pRotection of susceptible plants from soil-borne pathogens. Unlike many soils where disease suppressiveness requires crop monoculture to establish, certain soils are naturally suppressive to disease, and this type of specific disease suppressiveness is maintained despite crop Rotation. Soils naturally suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco and other crops occur in Morens region (Switzerland) and have been studied for over 30 years. In Morens, vermiculite-rich suppressive soils formed on morainic deposits while illite-rich conducive soils developed on sandstone, but suppressiveness is of microbial origin. Antagonistic pseudomonads play a role in Black Root Rot suppressiveness, including Pseudomonas pRotegens (formerly P. fluorescens) CHA0, a major model strain for research. However, other types of rhizobacterial taxa may differ in prevalence between suppressive and conducive soils, suggesting that the microbial basis of Black Root Rot suppressiveness could be far more complex than solely a Pseudomonas property. This first review on Black Root Rot suppressive soils covers early findings on these soils, the significance of recent results, and compares them with other types of suppressive soils in terms of rhizosphere ecology and plant pRotection mechanisms.

  • Evaluation of rhizobacterial indicators of tobacco Black Root Rot suppressiveness in farmers' fields
    Environmental Microbiology Reports, 2014
    Co-Authors: Martina Kyselková, Daniel Muller, Juliana Almario, Jan Kopecký, Markéta Ságová-marečková, Jacqueline Haurat, Geneviève L. Grundmann, Yvan Moënne-loccoz
    Abstract:

    Very few soil quality indicators include disease-suppressiveness criteria. We assessed whether 64 16S rRNA microarray probes whose signals correlated with tobacco Black Root Rot suppressiveness in greenhouse analysis could also discriminate suppressive from conducive soils under field conditions. Rhizobacterial communities of tobacco and wheat sampled in 2 years from four farmers' fields of contrasted suppressiveness status were compared. The 64 previously identified indicator probes correctly classified 72% of 29 field samples, with nine probes for Azospirillum, Gluconacetobacter, Sphingomonadaceae, Planctomycetes, Mycoplasma, Lactobacillus crispatus and Thermodesulforhabdus providing the best prediction. The whole probe set (1033 probes) revealed strong effects of plant, field location and year on rhizobacterial community composition, and a smaller (7% variance) but significant effect of soil suppressiveness status. Seventeen additional probes correlating with suppressiveness status in the field (noticeably for Agrobacterium, Methylobacterium, Ochrobactrum) were selected, and combined with the nine others, they improved correct sample classification from 72% to 79% (100% tobacco and 63% wheat samples). Pseudomonas probes were not informative in the field, even those targeting biocontrol pseudomonads producing 2,4-diacetylphloroglucinol, nor was quantitative polymerase chain reaction for 2,4-diacetylphloroglucinol-synthesis gene phlD. This study shows that a subset of 16S rRNA probes targeting diverse rhizobacteria can be useful as suppressiveness indicators under field conditions.

  • Assessment of the relationship between geologic origin of soil, rhizobacterial community composition and soil receptivity to tobacco Black Root Rot in Savoie region (France)
    Plant and Soil, 2013
    Co-Authors: Juliana Almario, Daniel Muller, Martina Kyselková, Jan Kopecký, Markéta Ságová-marečková, Geneviève L Grundmann, Yvan Moënne-loccoz
    Abstract:

    Background and aims In Morens (Switzerland), soils formed on morainic deposits (which contain vermiculite clay and display particular tobacco rhizobacterial community) are naturally suppressive to Thielaviopsis basicola-mediated tobacco Black Root Rot, but this paradigm was never assessed elsewhere. Here, we tested the relation between geology and disease suppressiveness in neighboring Savoie (France).

  • Assessment of the relationship between geologic origin of soil, rhizobacterial community composition and soil receptivity to tobacco Black Root Rot in Savoie region (France)
    Plant and Soil, 2013
    Co-Authors: Juliana Almario, Daniel Muller, Martina Kyselková, Jan Kopecký, Markéta Ságová-marečková, Geneviève L. Grundmann, Yvan Moënne-loccoz
    Abstract:

    Background and aims In Morens (Switzerland), soils formed on morainic deposits (which contain vermiculite clay and display particular tobacco rhizobacterial community) are naturally suppressive to Thielaviopsis basicola-mediated tobacco Black Root Rot, but this paradigm was never assessed elsewhere. Here, we tested the relation between geology and disease suppressiveness in neighboring Savoie (France). Methods Two morainic and two sandstone soils from Savoie were compared based on disease receptivity (T. basicola inoculation tests on tobacco), clay mineralogy (X-ray diffraction), tobacco rhizobacterial community composition (16S rRNA gene-based taxonomic microarray) and phlD + Pseudomonas populations involved in 2,4-diacetylphloroglucinol production (real-time PCR and tRFLP). Results Unlike in Morens, in Savoie the morainic soils were receptive to disease whereas T. basicola inoculation did not increase disease level in the sandstone soils. Vermiculite was not present in Savoie soils. The difference in rhizobacterial community composition between Savoie morainic and sandstone soils was significant but modest, and there was little agreement in bacterial taxa discriminating soils of different disease receptivity levels when comparing Morens versus Savoie soils. Finally, phlD + rhizosphere pseudomonads were present at levels comparable to those in Morens soils, but with different diversity patterns. Conclusions The morainic model of Black Root Rot suppressiveness might be restricted to the particular type of moraine occurring in the Morens region, and the low disease receptivity of sandstone soils in neighboring Savoie might be related to other plant-pRotection mechanisms.

  • Monitoring of the relation between 2,4-diacetylphloroglucinol-producing Pseudomonas and Thielaviopsis basicola populations by real-time PCR in tobacco Black Root-Rot suppressive and conducive soils
    Soil Biology and Biochemistry, 2012
    Co-Authors: Juliana Almario
    Abstract:

    Natural suppressiveness of Swiss soils to Thielaviopsis basicola-mediated tobacco Black Root Rot is thought to depend mainly on fluorescent pseudomonads producing the antimicrobial compound 2,4-diacetylphloroglucinol. However, the relation between these phl+ Pseudomonas populations and both the T. basicola population and disease suppressiveness in these soils is unknown, and real-time PCR tools were used to address this issue. Significant rhizosphere levels of phl+ pseudomonads had been evidenced before in suppressive as well as conducive soils, but this was done using culture-based approaches only. Here, a phlD-based real-time PCR method targeting all phlD+ genotypes, unlike the strain-specific real-time PCR methods available so far, was developed and validated (detection limit around 4 log cells g-1 soil and amplification efficiency >80%). When implemented on Swiss soils suppressive or conducive to Black Root Rot, it clarified the hypothesis that suppressiveness does not require higher levels of phlD+ pseudomonads. The parallel assessment of T. basicola population by real-time PCR (method of Huang and Kang, 2010) suggested that suppressiveness was not due to the inability of the pathogen to colonize the rhizosphere and tobacco Roots in suppressive soils, but rather that phl+ pseudomonads might act by limiting Root penetration by the pathogen in suppressive soils. In conclusion, an effective real-time PCR method was achieved for phlD+ pseudomonads and can be used to monitor this key functional group in various environmental conditions, including here to better understand the ecology of suppressive soils.

Geneviève Défago - One of the best experts on this subject based on the ideXlab platform.

  • Rhizosphere ecology and phytopRotection in soils naturally suppressive to Thielaviopsis Black Root Rot of tobacco
    Environmental Microbiology, 2014
    Co-Authors: Juliana Almario, Daniel Muller, Geneviève Défago, Yvan Moënne-loccoz
    Abstract:

    Soil suppressiveness to disease is an intriguing emerging property in agroecosystems, with important implications because it enables significant pRotection of susceptible plants from soil-borne pathogens. Unlike many soils where disease suppressiveness requires crop monoculture to establish, certain soils are naturally suppressive to disease, and this type of specific disease suppressiveness is maintained despite crop Rotation. Soils naturally suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco and other crops occur in Morens region (Switzerland) and have been studied for over 30 years. In Morens, vermiculite-rich suppressive soils formed on morainic deposits while illite-rich conducive soils developed on sandstone, but suppressiveness is of microbial origin. Antagonistic pseudomonads play a role in Black Root Rot suppressiveness, including Pseudomonas pRotegens (formerly P. fluorescens) CHA0, a major model strain for research. However, other types of rhizobacterial taxa may differ in prevalence between suppressive and conducive soils, suggesting that the microbial basis of Black Root Rot suppressiveness could be far more complex than solely a Pseudomonas property. This first review on Black Root Rot suppressive soils covers early findings on these soils, the significance of recent results, and compares them with other types of suppressive soils in terms of rhizosphere ecology and plant pRotection mechanisms.

  • Denaturing gradient gel electrophoretic analysis of dominant 2,4-diacetylphloroglucinol biosynthetic phlD alleles in fluorescent Pseudomonas from soils suppressive or conducive to Black Root Rot of tobacco
    Soil Biology and Biochemistry, 2010
    Co-Authors: Michele Frapolli, Geneviève Défago, Yvan Moënne-loccoz
    Abstract:

    In Switzerland, similar types of rhizosphere pseudomonads producing the biocontrol compound 2,4- diacetylphloroglucinol (Phl) have been found in soils suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco as well as in conducive soils. However, most findings were based on the analysis of a limited number of Pseudomonas isolates, obtained from a single experiment and only from T. basicolainoculated plants. Here, an approach based on denaturing gradient gel electrophoresis (DGGE) of dominant phlD alleles from tobacco rhizosphere provided different phlD migration patterns. Sequencing of phlD-DGGE bands revealed a novel phylogenetic cluster of phlD sequences found in both suppressive and conducive soils in addition to previously-documented phlD alleles. phlD-DGGE bands and alleles differed little from one plant to the next but more extensively from one sampling to the next during the three-year study. Three of the 13 bands and 12 of the 31 alleles were only found in suppressive soil, whereas five bands and 13 alleles were found exclusively in conducive soil. The population structure of phlDþ pseudomonads depended more on the individual soil considered and its suppressiveness status than on inoculation of tobacco with T. basicola. In conclusion, phlD-DGGE revealed additional phlD diversity compared with earlier analyses of individual Pseudomonas isolates, and showed differences in phlDþ Pseudomonas population structure in relation to disease suppressiveness.

  • Comparison of rhizobacterial community composition in soil suppressive or conducive to tobacco Black Root Rot disease
    The ISME Journal, 2009
    Co-Authors: Martina Kyselková, Geneviève Défago, Michele Frapolli, Jan Kopecký, Markéta Ságová-marečková, Geneviève L Grundmann, Yvan Moënne-loccoz
    Abstract:

    Work on soils suppressive to Thielaviopsis basicola -mediated tobacco Black Root Rot has focused on antagonistic pseudomonads to date. The role of non- Pseudomonas rhizosphere populations has been neglected, and whether they differ in Black Root Rot-suppressive versus -conducive soils is unknown. To assess this possibility, tobacco was grown in a suppressive and a conducive soil of similar physicochemical properties, and rhizobacterial community composition was compared using a 16S rRNA taxonomic microarray. The microarray contains 1033 probes and targets 19 bacterial phyla. Among them, 398 probes were designed for PRoteobacteria , Firmicutes , Actinomycetes , Cyanobacteria and Bacteroidetes genera/species known to include strains relevant for plant pRotection or plant growth promotion. Hierarchical clustering as well as principal component analysis of microarray data discriminated clearly between Black Root Rot-suppressive and -conducive soils. In contrast, T. basicola inoculation had no impact on rhizobacterial community composition. In addition to fluorescent Pseudomonas , the taxa Azospirillum , Gluconacetobacter , Burkholderia , Comamonas and Sphingomonadaceae , which are known to comprise strains with plant-beneficial properties, were more prevalent in the suppressive soil. Mycobacterium , Bradyrhizobium , Rhodobacteraceae , Rhodospirillum and others were more prevalent in the conducive soil. For selected taxa, microarray results were largely corroborated by quantitative PCR and cloning/sequencing. In conclusion, this work identified novel bacterial taxa that could serve as indicators of disease suppressiveness in soil-quality assessments, and it extends the range of bacterial taxa hypothesized to participate in Black Root Rot suppression.

  • prevalence of fluorescent pseudomonads producing antifungal phloroglucinols and or hydrogen cyanide in soils naturally suppressive or conducive to tobacco Black Root Rot
    FEMS Microbiology Ecology, 2003
    Co-Authors: Alban Ramette, Yvan Moenneloccoz, Geneviève Défago
    Abstract:

    Certain soils from Morens, Switzerland, are naturally suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco, and fluorescent pseudomonads are involved in this suppressiveness. Here, we compared two conducive, one moderately suppressive and one suppressive soil from Morens. Disease levels on tobacco after heavy T. basicola inoculation varied from 29% to 85% for the two conducive soils, 10% to 78% for the moderately suppressive soil and 11% to 42% for the suppressive soil, depending on time of the year. In the absence of T. basicola inoculation, disease levels were between 0% and 40% and varied also in time. Fluorescent pseudomonads were isolated from the rhizosphere and Roots of tobacco subjected to T. basicola inoculation and characterized for production of the biocontrol metabolites 2,4-diacetylphloroglucinol (Phl) and HCN. No difference in population size was found between the suppressive and the conducive soils for total, Phl+ and HCN+ fluorescent pseudomonads colonizing the rhizosphere or Roots of tobacco. Yet, the percentage of Phl+ isolates was significantly higher (30–32% vs. 6–11%) in the rhizosphere and Roots for plants grown in the suppressive soil compared with the moderately suppressive and conducive soils. Different restriction profiles for phlD, one of the Phl biosynthetic genes, were often found when analyzing Phl+ isolates colonizing the same plant. Most phlD alleles were recovered from both suppressive and conducive soils, except one allele found only in Root isolates from the suppressive soil.

  • Prevalence of fluorescent pseudomonads producing antifungal phloroglucinols and/or hydrogen cyanide in soils naturally suppressive or conducive to tobacco Black Root Rot
    FEMS Microbiology Ecology, 2003
    Co-Authors: Alban Ramette, Yvan Moënne-loccoz, Geneviève Défago
    Abstract:

    Certain soils from Morens, Switzerland, are naturally suppressive to Thielaviopsis basicola-mediated Black Root Rot of tobacco, and fluorescent pseudomonads are involved in this suppressiveness. Here, we compared two conducive, one moderately suppressive and one suppressive soil from Morens. Disease levels on tobacco after heavy T. basicola inoculation varied from 29% to 85% for the two conducive soils, 10% to 78% for the moderately suppressive soil and 11% to 42% for the suppressive soil, depending on time of the year. In the absence of T. basicola inoculation, disease levels were between 0% and 40% and varied also in time. Fluorescent pseudomonads were isolated from the rhizosphere and Roots of tobacco subjected to T. basicola inoculation and characterized for production of the biocontrol metabolites 2,4-diacetylphloroglucinol (Phl) and HCN. No difference in population size was found between the suppressive and the conducive soils for total, Phl+ and HCN+ fluorescent pseudomonads colonizing the rhizosphere or Roots of tobacco. Yet, the percentage of Phl+ isolates was significantly higher (30–32% vs. 6–11%) in the rhizosphere and Roots for plants grown in the suppressive soil compared with the moderately suppressive and conducive soils. Different restriction profiles for phlD, one of the Phl biosynthetic genes, were often found when analyzing Phl+ isolates colonizing the same plant. Most phlD alleles were recovered from both suppressive and conducive soils, except one allele found only in Root isolates from the suppressive soil.

Martina Kyselková - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of rhizobacterial indicators of tobacco Black Root Rot suppressiveness in farmers' fields
    Environmental Microbiology Reports, 2014
    Co-Authors: Martina Kyselková, Daniel Muller, Juliana Almario, Jan Kopecký, Markéta Ságová-marečková, Jacqueline Haurat, Geneviève L. Grundmann, Yvan Moënne-loccoz
    Abstract:

    Very few soil quality indicators include disease-suppressiveness criteria. We assessed whether 64 16S rRNA microarray probes whose signals correlated with tobacco Black Root Rot suppressiveness in greenhouse analysis could also discriminate suppressive from conducive soils under field conditions. Rhizobacterial communities of tobacco and wheat sampled in 2 years from four farmers' fields of contrasted suppressiveness status were compared. The 64 previously identified indicator probes correctly classified 72% of 29 field samples, with nine probes for Azospirillum, Gluconacetobacter, Sphingomonadaceae, Planctomycetes, Mycoplasma, Lactobacillus crispatus and Thermodesulforhabdus providing the best prediction. The whole probe set (1033 probes) revealed strong effects of plant, field location and year on rhizobacterial community composition, and a smaller (7% variance) but significant effect of soil suppressiveness status. Seventeen additional probes correlating with suppressiveness status in the field (noticeably for Agrobacterium, Methylobacterium, Ochrobactrum) were selected, and combined with the nine others, they improved correct sample classification from 72% to 79% (100% tobacco and 63% wheat samples). Pseudomonas probes were not informative in the field, even those targeting biocontrol pseudomonads producing 2,4-diacetylphloroglucinol, nor was quantitative polymerase chain reaction for 2,4-diacetylphloroglucinol-synthesis gene phlD. This study shows that a subset of 16S rRNA probes targeting diverse rhizobacteria can be useful as suppressiveness indicators under field conditions.

  • Assessment of the relationship between geologic origin of soil, rhizobacterial community composition and soil receptivity to tobacco Black Root Rot in Savoie region (France)
    Plant and Soil, 2013
    Co-Authors: Juliana Almario, Daniel Muller, Martina Kyselková, Jan Kopecký, Markéta Ságová-marečková, Geneviève L Grundmann, Yvan Moënne-loccoz
    Abstract:

    Background and aims In Morens (Switzerland), soils formed on morainic deposits (which contain vermiculite clay and display particular tobacco rhizobacterial community) are naturally suppressive to Thielaviopsis basicola-mediated tobacco Black Root Rot, but this paradigm was never assessed elsewhere. Here, we tested the relation between geology and disease suppressiveness in neighboring Savoie (France).

  • Assessment of the relationship between geologic origin of soil, rhizobacterial community composition and soil receptivity to tobacco Black Root Rot in Savoie region (France)
    Plant and Soil, 2013
    Co-Authors: Juliana Almario, Daniel Muller, Martina Kyselková, Jan Kopecký, Markéta Ságová-marečková, Geneviève L. Grundmann, Yvan Moënne-loccoz
    Abstract:

    Background and aims In Morens (Switzerland), soils formed on morainic deposits (which contain vermiculite clay and display particular tobacco rhizobacterial community) are naturally suppressive to Thielaviopsis basicola-mediated tobacco Black Root Rot, but this paradigm was never assessed elsewhere. Here, we tested the relation between geology and disease suppressiveness in neighboring Savoie (France). Methods Two morainic and two sandstone soils from Savoie were compared based on disease receptivity (T. basicola inoculation tests on tobacco), clay mineralogy (X-ray diffraction), tobacco rhizobacterial community composition (16S rRNA gene-based taxonomic microarray) and phlD + Pseudomonas populations involved in 2,4-diacetylphloroglucinol production (real-time PCR and tRFLP). Results Unlike in Morens, in Savoie the morainic soils were receptive to disease whereas T. basicola inoculation did not increase disease level in the sandstone soils. Vermiculite was not present in Savoie soils. The difference in rhizobacterial community composition between Savoie morainic and sandstone soils was significant but modest, and there was little agreement in bacterial taxa discriminating soils of different disease receptivity levels when comparing Morens versus Savoie soils. Finally, phlD + rhizosphere pseudomonads were present at levels comparable to those in Morens soils, but with different diversity patterns. Conclusions The morainic model of Black Root Rot suppressiveness might be restricted to the particular type of moraine occurring in the Morens region, and the low disease receptivity of sandstone soils in neighboring Savoie might be related to other plant-pRotection mechanisms.

  • Comparison of rhizobacterial community composition in soil suppressive or conducive to tobacco Black Root Rot disease
    The ISME Journal, 2009
    Co-Authors: Martina Kyselková, Geneviève Défago, Michele Frapolli, Jan Kopecký, Markéta Ságová-marečková, Geneviève L Grundmann, Yvan Moënne-loccoz
    Abstract:

    Work on soils suppressive to Thielaviopsis basicola -mediated tobacco Black Root Rot has focused on antagonistic pseudomonads to date. The role of non- Pseudomonas rhizosphere populations has been neglected, and whether they differ in Black Root Rot-suppressive versus -conducive soils is unknown. To assess this possibility, tobacco was grown in a suppressive and a conducive soil of similar physicochemical properties, and rhizobacterial community composition was compared using a 16S rRNA taxonomic microarray. The microarray contains 1033 probes and targets 19 bacterial phyla. Among them, 398 probes were designed for PRoteobacteria , Firmicutes , Actinomycetes , Cyanobacteria and Bacteroidetes genera/species known to include strains relevant for plant pRotection or plant growth promotion. Hierarchical clustering as well as principal component analysis of microarray data discriminated clearly between Black Root Rot-suppressive and -conducive soils. In contrast, T. basicola inoculation had no impact on rhizobacterial community composition. In addition to fluorescent Pseudomonas , the taxa Azospirillum , Gluconacetobacter , Burkholderia , Comamonas and Sphingomonadaceae , which are known to comprise strains with plant-beneficial properties, were more prevalent in the suppressive soil. Mycobacterium , Bradyrhizobium , Rhodobacteraceae , Rhodospirillum and others were more prevalent in the conducive soil. For selected taxa, microarray results were largely corroborated by quantitative PCR and cloning/sequencing. In conclusion, this work identified novel bacterial taxa that could serve as indicators of disease suppressiveness in soil-quality assessments, and it extends the range of bacterial taxa hypothesized to participate in Black Root Rot suppression.

H D Shew - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of components of partial resistance to Black Root Rot in burley tobacco
    Plant Disease, 1995
    Co-Authors: C. A. Wilkinson, H D Shew, R. C. Rufty
    Abstract:

    Cultivars with moderate (KY 14), low (Burley 21), and no resistance (Judy's Pride) to Black Root Rot, and the F 1 of KY 14 x Burley 21 were evaluated for components of partial resistance to Thielaviopsis basicola. In addition, transgressive segregants from a previous generation mean analysis were intercrossed and progeny of the following crosses were evaluated: (KY 14 x Burley 21)F 2 x (KY 14 x (KY 14 x Burley 21)F 1 ), (KY 14 x Burley 21)F 2 x (Burley 21 x (KY 14 x Burley 21)F 1 ), and (KY 14 x (KY 14 x Burley 21)F 1 ) x (Burley 21 x (KY 14 x Burley 21)F 1 ). Five-week-old seedlings were transplanted into soil infested with 100 chlamydospores of T. basicola per gram of soil mixture and grown in the greenhouse at an average air temperature of 21°C. Disease severity (percent Root necrosis), number of lesions per Root, lesion length, and population density of the pathogen were estimated 3 weeks after transplanting. Significant differences were observed among genotypes for each component of partial resistance measured. Significant positive correlations were observed between lesion number and disease severity and between lesion number and lesion length. However, a significant negative correlation was observed between lesion number and population density. Selection for components of partial resistance in burley tobacco should lead to increased levels of resistance to Black Root Rot.

  • Effects of host resistance and soil fumigation on Thielaviopsis basicola and development of Black Root Rot on burley tobacco.
    Plant Disease, 1993
    Co-Authors: H D Shew, P. B. Shoemaker
    Abstract:

    Cultivars of burley tobacco (Nicotiana tabacum) with different levels of resistance to Thielaviopsis basicola were planted in fields naturally infested with the pathogen. Severity of Black Root Rot and populations of T. basicola were determined at transplant, midseason, and after final harvest. Cultivars with monogenic resistance to T. basicola derived from Nicotiana debneyi developed little or no Root Rot in all tests and suppressed pathogen reproduction during the growing sermon. The severity of Root Rot and the reproduction of T. basicola were not related to the level of partial resistance

  • soils suppressive to Black Root Rot of burley tobacco caused by thielaviopsis basicola
    Phytopathology, 1991
    Co-Authors: John R Meyer, H D Shew
    Abstract:

    Soils suppressive to Black Root Rot were detected in fields in which the pathogen was present but in which little or no disease had developed on susceptible cultivars of burley tobacco. Suppressive soils were characterized by low base saturation, low calcium, exchangeable aluminum levels of 1 meq/100 g of soil or higher, and soil pH less than 5. Suppressiveness was confirmed under controlled environmental conditions with fumigated field soils reinfested with Thielaviopsis basicola (...)

  • Development of Black Root Rot on burley tobacco as influenced by inoculum density of Thielaviopsis basicola, host resistance, and soil chemistry.
    Plant Disease, 1991
    Co-Authors: John R Meyer, H D Shew
    Abstract:

    Twelve fields infested with Thielaviopsis basicola, selected from 80 surveyed the previous year, were planted with cultivars of burley tobacco with either low (B21× Ky 10) or moderate (Ky 14) resistance to Black Root Rot. One week after transplantation, soil samples were taken around 20 individual plants in each field to determine the inoculum density of the pathogen and to conduct soil chemical analyses. Severity of Black Root Rot, evaluated on each of the same plants 6 wk later, depended on inoculum density, level of host resistance, and soil chemistry (...)