[en] TaqMan-based quantitative PCR (qPCR) assays were developed to study the persistence of two well-characterized strains of plant growth-promoting rhizobacteria (PGPR), Pseudomonas fluorescens Pf153 and Pseudomonas sp. DSMZ 13134, in the root and rhizoplane of inoculated maize plants. This was performed in pot experiments with three contrasting field soils (Buus, Le Caron and DOK-M). Potential cross-reactivity of the qPCR assays was assessed with indigenous Pseudomonas and related bacterial species, which had been isolated from the rhizoplane of maize roots grown in the three soils and then characterized by Matrix-Assisted Laser Desorption Ionization (MALDI) Time-of-Flight (TOF) mass spectrometry (MS). Sensitivity of the qPCR expressed as detection limit of bacterial cells spiked into a rhizoplane matrix was 1.4 × 102 CFU and 1.3 × 104 CFU per gram root fresh weight for strain Pf153 and DSMZ 13134, respectively. Four weeks after planting and inoculation, both strains could readily be detected in root and rhizoplane, whereas only Pf153 could be detected after 8 weeks. The colonization rate of maize roots by strain Pf153 was significantly influenced by the soil type, with a higher colonization rate in the well fertile and organic soil of Buus. Inoculation with strain DSMZ 13134, which colonized roots and rhizoplane to the same degree, independently of the soil type, increased yield of maize, in terms of biomass accumulation, only in the acidic soil of Le Caron, whereas inoculation with strain Pf153 reduced yield in the soil Buus, despite of its high colonization rate and persistence. These results indicate that the colonization rate and persistence of inoculated Pseudomonas strains can be quantitatively assessed by the TaqMan-based qPCR technique, but that it cannot be taken for granted that inoculation with a well-colonizing and persistent Pseudomonas strain has a positive effect on yield of maize.
Mosimann, Carla; Department of Environmental Sciences, Botany, Zürich-Basel Plant Science Center, University of BaselBasel, Switzerland, Research Institute of Organic Agriculture (FIBL)Frick, Switzerland
Oberhänsli, Thomas; Research Institute of Organic Agriculture (FIBL) Frick, Switzerland
Ziegler, Dominik; Mabritec AG Riehen, Switzerland
Nassal, Dinah; Institute of Soil Science and Land Evaluation, University of Hohenheim Stuttgart, Germany
Kandeler, Ellen; Institute of Soil Science and Land Evaluation, University of Hohenheim Stuttgart, Germany
Boller, Thomas; Department of Environmental Sciences, Botany, Zürich-Basel Plant Science Center, University of Basel Basel, Switzerland
Mäder, Paul; Research Institute of Organic Agriculture (FIBL) Frick, Switzerland
Thonar, Cécile ; Université de Liège - ULiège > Département GxABT > Plant Sciences ; Research Institute of Organic Agriculture (FIBL) Frick, Switzerland
Language :
English
Title :
Tracing of Two Pseudomonas Strains in the Root and Rhizoplane of Maize, as Related to Their Plant Growth-Promoting Effect in Contrasting Soils.
FP7 - 312117 - BIOFECTOR - Resource Preservation by Application of BIOefFECTORs in European Crop Production
Funders :
EU - European Union
Funding text :
We thank following persons for the provision of bacterial strains: J. Fuchs (FiBL, Switzerland) for P. fluorescens Pf153, W. Vogt (Sourcon-Padena, Germany) for Pseudomonas sp. DSMZ 13134, K. Smalla (Julius K?hn Institute, Germany) for P. jessenii RU47 and M. Maurhofer (ETH Z?rich, Switzerland) for P. protegens CHA0, P. protegens Pf-5 as well as P. chlororaphis LMG 1245. We thank H.-M. Krause (FiBL, Switzerland) for provision of the plasmid for the internal standard as well as D. Gobbin (Tecan Group Ltd, Switzerland) for the sequence of the SCAR fragment. This study was funded by the BIOFECTOR project (Resource preservation by application of BIOefFECTORs in European crop production, grant agreement number 312117) under the 7th Framework Program (FP7), European Commission, Brussels, Belgium.
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