Factors driving the distribution and diversity of protistan plant pathogens in grasslands and forests of the Biodiversity Exploratories

Plant-microbe interactions are considered the main drivers of plant diversity and community composition. Oomycetes (eg Pythium) and cercozoan parasites (eg Plasmodiophora) contain some of the most destructive ubiquituous plant pathogens. They are functionally diverse, spanning a range of facultative and obligatory parasites to free-living bacterivores, with some parasitic taxa spending part of their life cycle as saprotrophs. We have assessed the diversity and natural reservoirs of these two groups of protists in soils of all 300 grassland and forestplots of the Biodiversity Exploratories, using high-throughput Illumina sequencing. The Biodiversity Exploratories offer the opportunity to study the effects of land-use intensification on plant parasites and their free-living relatives in different geographic regions of Germany. Network analyses will be applied to identify i) central interacting plant pathogens (i.e. hubs) in microbial communities, ii) potential suppressive soil communities. This will be the first large-scale study to reveal the distribution of these highly diverse and functionally important protists in natural habitats. This study will help identifying the management practices suppressing plant parasites and give hints on the circumstances of pathogen outbreaks.