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Erlacher A.,University of Graz | Cardinale M.,University of Graz | Grosch R.,Leibniz Institute of Vegetable and Ornamental Crops | Grube M.,University of Graz | Berg G.,University of Graz
Frontiers in Microbiology | Year: 2014

Lettuce belongs to the most commonly raw eaten food worldwide and its microbiome plays an important role for both human and plant health. Yet, little is known about the impact of potentially occurring pathogens and beneficial inoculants of the indigenous microorganisms associated with lettuce. To address this question we studied the impact of the phytopathogenic fungus Rhizoctonia solani and the biological control agent Bacillus amyloliquefaciens FZB42 on the indigenous rhizosphere and phyllosphere community of greenhouse-grown lettuce at two plant stages. The rhizosphere and phyllosphere gammaproteobacterial microbiomes of lettuce plants showed clear differences in their overall and core microbiome composition as well as in corresponding diversity indices. The rhizosphere was dominated by Xanthomonadaceae (48%) and Pseudomonadaceae (37%) with Rhodanobacter, Pseudoxanthomonas, Dokdonella, Luteimonas, Steroidobacter, Thermomonas as core inhabitants, while the dominating taxa associated to phyllosphere were Pseudomonadaceae (54%), Moraxellaceae (16%) and Enterobacteriaceae (25%) with Alkanindiges, Pantoea and a group of Enterobacteriaceae unclassified at genus level. The preferential occurrence of enterics in the phyllosphere was the most significant difference between both habitats. Additional enhancement of enterics on the phyllosphere was observed in bottom rot diseased lettuce plants, while Acinetobacter and Alkanindiges were identified as indicators of healthy plants. Interestingly, the microbial diversity was enhanced by trea tment with both the pathogen, and the co-inoculated biological control agent. The highest impact and bacterial diversity was found by Rhizoctonia inoculation, but FZB42 lowered the impact of Rhizoctonia on the microbiome. This study shows that the indigenous microbiome shifts as a consequence to pathogen attack but FZB42 can compensate these effects, which supports their role as biocontrol agent and suggests a novel mode of action © 2014 Erlacher, Cardinale, Grosch, Grube and Berg. Source


Franken P.,Leibniz Institute of Vegetable and Ornamental Crops | Franken P.,Humboldt University of Berlin
Applied Microbiology and Biotechnology | Year: 2012

The successful conversion of plant production systems from conventional resource-exhausting to sustainable strategies depends on knowledge-based management of environmental factors. Root-inhabiting fungi came more and more into focus because their hyphae connect in ideal manner resources and challenges of the surrounding with the plant. A paradigm for such root endophytes is presented by the basidiomycete Piriformospora indica. This fungus possesses a broad host spectrum and positively affects different aspects of plant performance. This so far unique combination of attributes makes P. indica and its close relatives among the Sebacinales very interesting tools for cultivation of various crops. This review will outline the different aspects required to apply this root endophyte in agri- and horticulture concerning plant growth, plant nutrition and plant defence or tolerance thereby explaining what is known about the biological basis for the observed effects. Open questions and challenges for successful inoculum production and application will be discussed. © Springer-Verlag Berlin Heidelberg 2012. Source


Lueck E.,University of Potsdam | Ruehlmann J.,Leibniz Institute of Vegetable and Ornamental Crops
Geoderma | Year: 2013

GEOPHILUS ELECTRICUS (nickname GEOPHILUS) is a novel system for mapping the complex electrical bulk resistivity of soils. Rolling electrodes simultaneously measure amplitude and phase data at frequencies ranging from 1. mHz to 1. kHz. The sensor's design and technical specifications allow for measuring these parameters at five depths of up to ca. 1.5. m. Data inversion techniques can be employed to determine resistivity models instead of apparent values and to image soil layers and their geometry with depth. When used in combination with a global positioning system (GPS) and a suitable cross-country vehicle, it is possible to map about 100. ha/day (assuming 1 data point is recorded per second and the line spacing is 18. m). The applicability of the GEOPHILUS system has been demonstrated on several sites, where soils show variations in texture, stratification, and thus electrical characteristics. The data quality has been studied by comparison with 'static' electrodes, by repeated measurements, and by comparison with other mobile conductivity mapping devices (VERIS3100 and EM38). The high quality of the conductivity data produced by the GEOPHILUS system is evident and demonstrated by the overall consistency of the individual maps, and in the clear stratification also confirmed by independent data.The GEOPHILUS system measures complex values of electrical resistivity in terms of amplitude and phase. Whereas electrical conductivity data (amplitude) are well established in soil science, the interpretation of phase data is a topic of current research. Whether phase data are able to provide additional information depends on the site-specific settings. Here, we present examples, where phase data provide complementary information on man-made structures such as metal pipes and soil compaction. © 2013 Elsevier B.V.. Source


Ruppel S.,Leibniz Institute of Vegetable and Ornamental Crops
Communications in Soil Science and Plant Analysis | Year: 2013

Plant growth-promoting rhizobacteria (PGPR) may enhance the plant availability of phosphorus (P) in soil. A greenhouse pot experiment was conducted cultivating maize (Zea mays L.) on a P-deficient soil. Three bacterial treatments (control without PGPR and application of either Enterobacter radicincitans sp. nov. strain DSM 16656 or Pseudomonas fluorescens strain DR54) were tested in conjunction with three P treatments [no P addition, inorganic P as triplesuperphosphate (TSP), and organic P as phytin] at two different growth stages of maize (V6 and V9). Amendment with TSP enhanced growth, P uptake, and highly bioavailable P pools in soil to a greater extent than phytin. In contrast, arbuscular mycorrhiza (AM) formation of maize roots after phytin application doubled those for the TSP treatment or the control without P. Application of PGPR was also able to increase AM formation and P uptake of maize, especially when no P source was added. Furthermore, P. fluorescens inoculation resulted in an increase of highly soluble soil P pools at the early growth stage. Greater impacts of phytin on P nutrition of maize may exist in a longer term as a result of slow P release and promotion of AM fungi. Benefits to maize P nutrition derived from PGPR application can be expected under P deficiency. © 2013 Copyright Taylor and Francis Group, LLC. Source


Ruehlmann J.,Leibniz Institute of Vegetable and Ornamental Crops
Archives of Agronomy and Soil Science | Year: 2013

The Box Plot Experiment in Grossbeeren was set up in 1972 to investigate the efficiency of diverse fertilization strategies within an irrigated vegetable crop rotation system for three different soils. Here, we report on the long-term effects on nitrogen, carbon and energy balances of applying various organic amendments and different amounts of mineral N fertilizer to soils. Fertile soils (sandy loam and clayey silt) were characterized by higher yield and N removal potential by plants, higher acceptable N input amounts, and a higher proportion of total N input recovered by soil N storage and N uptake by plants. After 40 years, organic carbon equilibrium in the soil has not been reached. Rates of change of organic carbon stocks are still affected by the different organic matter levels at the beginning of the experiment. An increasing net N supply increased and organic C input decreased net C gains. Because of the manifold possibilities of producing energy from current or former agricultural land, energetic evaluation of land use needs to become more complex if direct comparisons are to be made. Including the energy contents of organic amendments and soil organic matter in the energy balances would be a first step in this direction. © 2013 Copyright Taylor and Francis Group, LLC. Source

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