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

植物-微生物相互作用被认为是植物多样性和群落组成的主要驱动因素。卵菌（如霉）和尾虫寄生虫（如疟原虫）含有一些最具破坏性的无处不在的植物病原体。除作物植物外，它们还寄居在广泛的寄主范围内，并可能对自然植物群落的多样性产生重要但尚未可知的影响。尽管它们具有重要的功能，但它们在自然生境中的分布从未被系统地研究过。分子环境测序允许以前所未有的细节调查土壤中微生物病原体的多样性和分布。我们计划利用高通量Illumina测序技术，在生物多样性探索项目的所有300个草地和森林试验地（EPs）的土壤以及BELOW子项目的根际样品中，评估两组原生生物（卵菌和尾虫）的多样性和天然储存库。这两类原生生物在功能上是多种多样的，从兼性和强制性寄生虫到自由生活的细菌捕食者，其中一些寄生类群在其生命周期的一部分是腐养生物。生物多样性探索提供了研究土地利用集约化对德国不同地理区域植物寄生虫及其自由生活亲属的影响的机会。网络分析将用于确定i)微生物群落中的中心相互作用植物病原体（即枢纽），ii)潜在的抑制土壤群落，以及iii)它们与根渗出物代谢物和植物性状的关系。这将是首次大规模研究揭示这些高度多样化和功能重要的原生生物在自然栖息地的分布。该研究将有助于确定抑制植物寄生虫的管理措施，并为病原菌爆发情况提供线索。

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. Apart from crop plants, they colonize a wide range of hosts and potentially have an important but yet unknown impact on the diversity of natural plant communities. In spite of their functional importance, their distribution in natural habitats has never been systematically studied. Molecular environmental sequencing allows investigating in unprecedented details the diversity and distribution of microbial pathogens directly in soil. We plan to assess the diversity and natural reservoirs of two groups of protists, the Oomycetes and Cercozoa, in soils of all 300 grassland and forest experimental plots (EPs) of the Biodiversity Exploratories and in rhizosphere samples from the BELOW subproject, using high-throughput Illumina sequencing. These two groups of protists 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. 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, and iii) their relationships to metabolites from root exudation and plant traits. This will be the first large-scale study to reveal the distribution of these highly diverse and functionally important protist in natural habitats. This study will help identifying the management practices suppressing plant parasites and give hints on the circumstances of pathogen outbreaks.