Biological Control

The research focus is on the ecological properties of biocontrol pseudomonads as well as the mechanisms that govern interactions among phytopathogens, the plant and the non-target microbiota.

Ongoing Research Projects

  • Molecular determinants contributing to insect and plant associated lifestyles of beneficial pseudomonads (Joint SNF project with Christoph Keel, University of Lausanne)
    Root-associated fluorescent pseudomonads are of agricultural importance because they can improve the health and performance of crop plants due to their manifold plant-beneficial activities, including pathogen control. We discovered that a particular subgroup of these pseudomonads, Pseudomonas protegens and P. chlororaphis, exhibits activity against plant pathogens and pest insects. The bacteria colonize pest insects (in particular Lepidoptera) with ease and exert strong oral and systemic toxicity. In the insect host, production of a potent insect toxin (Fit) is specifically switched on and contributes to insecticidal activity of these bacteria, yet additional virulence factors remain to be unravelled. It is not known which genomic equipment enables the pseudomonads to colonize and kill insects following oral infection and how they switch their lifestyle from a plant to an insect environment. Our project aims at identifying additional/novel factors contributing to insect and plant interactions of P. protegens and P. chlororaphis using an integrated, whole genome-based approach which combines comparative genomics with comparative transcriptomics and targeted and high-density random mutational analyses. We hope to provide pioneering knowledge on the nature of insecticidal activity of plant-beneficial pseudomonads and on host-adapted expression of genes allowing these bacteria to switch from plant to insect hosts.
  • Linking genotypic variation among plant-associated fluorescent pseudomonads with activation of plant defense against pathogens and insects (PSC-Syngenta fellowship with Consuelo de Moraes, ETHZ and Mark Mescher, ETHZ)
    Plant-associated fluorescent pseudomonads (PAFPs) are effective direct controls for soil-borne plant pathogens, and some have recently been shown to additionally have oral insecticide activity against important plant pests. Moreover, PAFPs colonization of plant roots may also affect interactions among plants and insects, suggesting that these bacteria have significant potential for use in the sustainable control of plant antagonists in agriculture. Realizing this potential requires greater understanding of the molecular and biochemical mechanisms underlying the direct and indirect (plant-mediated) effects of PAFPs on plant antagonists and their taxonomic diversity and distribution. In this project we characterize PAFPs belonging to different phylogenetic groups for their ability to induce resistance in plants against pathogens and herbivore insects. The project further aims at documenting the influence of the bacteria on changes in plant gene expression patterns and volatile emissions influencing plant interactions with insects and parasitoids. Comparative genomics and transcriptomics will additionally be used to understand the genetic basis of variation among PAFP strains in their influences on plant phenotypes and plant resistance.
  • Biological control of soilborne insect pests using combinations of plant-beneficial fluorescent pseudomonads with insecticidal activity, entomopathogenic nematodes and entomopathogenic fungi. Joint Mercator-World Food System center research project with Giselher Grabenweger, Agroscope and Ute Vogler, Julius Kühn-Institut, Braunschweig financed by the Mercator foundation.
    Below ground insect pests are a yet unsolved problem not only in organic, but also in conventional crop production because they are difficult to target and the few effective chemical pesticides are already or will be banned in near future due to raising concerns for environmental and consumer safety. This project aims at developing a new approach for the biological control of soil-dwelling pest insects compatible with organic production. We evaluate the potential of a specific group of plant-beneficial fluorescent Pseudomonas bacteria with entomopathogenic activity (EPP) for insect control as a new non-Bacillus bacterial biocontrol agent with a different mode of action. We further investigate whether below-ground insect biocontrol can be improved by combining EPP with entomopathogenic fungi (EPF) and entomopathogenic nematodes (EPN), which are already well-established biocontrol agents (BCA’s) used in organic production. We will test promising EPP-EPN-EPF combinations in greenhouse and on-farm field trials against the cabbage root fly Delia radicum, a pest causing increasing losses in the production of brassicacean crops and for which no satisfactory control measures exist. This project will give exciting new insights into complex interactions between agriculturally important members of the soil and rhizosphere ecosystem. We hope to provide new methods based on the combined application of beneficial soil organisms for the control of an important insect pest in organic and conventional vegetable production, which may be adapted to other problematic soil pests.
  • Functional ecology and genetics of plant microbiome interactions linked to pseudomonads.
    Joint research project with Daniel Croll, University of Neuchâtel within COST action CA16110 financed by SNSF.
    Human pathogenic bacteria can show competence to interact and colonize plant hosts resulting in contamination of plant produce, which poses a severe threat to the health of consumers. Addressing the issue of pathogen emergence in agricultural ecosystems requires understanding the pathogen's ecological interactions in diverse environments. A key question to address is how bacteria interact with dominant members of the agricultural plant microbiome. This project aims to analyse the functional ecology of plant microbiome interactions focusing on pseudomonads and the ubiquitous wheat pathogen Zymoseptoria tritici. Pseudomonads are bacteria, which have adapted to many different environments including water, roots, leaves and some of them can cause opportunistic human infections. We are studying the colonization success and/or competitive exclusion of pseudomonads and Z. tritici and aim to identify genes involved in interactions between these organisms using genome-wide association mapping and transcriptome analysis. Knowledge of these loci will provide important insights into the mechanisms of competitive exclusion and persistence of bacteria in the phyllosphere microbiome.

     
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