Plant antagonists

Prof. Dr. Michael Bonkowski, Cologne, Germany
Prof. Dr. Sigrid Neuhauser, Innsbruck, Austria

SP09 investigates how drought affects protistan plant antagonists (Oomycota and Cercozoa-Phytomyxea) and resulting negative soil legacy effects in dependence on plant diversity. The main objective of this subproject is to study the temporal stability, resistance, and recovery of these protistan plant antagonists in response to drought and how these factors are affected by plant diversity. Our central hypothesis is that drought may amplify negative soil legacy effects by plant antagonists, especially at low plant diversity levels, as outlined by the multiple-mechanisms hypothesis. We designed four coordinated work packages (WPs) to assess:
i) changes in the community composition, structure and phylogenetic representation of microbial antagonists as affected by (normal) seasonal variation and extreme (hot drought) events and ii) the combined biotic and abiotic stresses affecting plant growth-defence trade-offs along the plant diversity gradient.

We hypothesize clear seasonal effects on the abundance and diversity of plant antagonists caused by changes in the soil (e.g. moisture) and the plants (e.g. changing rhizodeposition). We aim to determine the “normal operation range” in seasonal (January, May, August, November) community turnover of Oomycota and Cercozoa-Phytomyxea over two years in the Main Experiment (WP1) and compare these to data obtained in 2017 (roofed control plots in the Drought Experiment) and 2021 (+SH+PH in the Main Experiment). We will quantify the resistance of communities of protistan plant antagonists to a hot drought in the DrY Experiment
(WP2). By targeting the ‘active’ microbial communities and functional genes for root pathogen attack (RNA-based metatranscriptomics), we will assess the resistance and resilience of microbiota, as well as assess the microbial impact on the plant defence systems in the ResCUE Experiment (WP3). Finally, we will set up a CoMic Experiment to specifically investigate
the role of the growth-defence trade-off in (de)stabilizing plant performance with increasing drought intensity and plant species richness (WP4).