Microbial attachment to endoparasitic phytonematodes in soil

• Applicant: Dr. Holger Heuer
• Subject Area: Plant Breeding and Plant Pathology ; Microbial Ecology and Applied Microbiology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270451289

Sedentary plant-parasitic nematodes are among the most damaging pests in agriculture. The control of these emerging pests is becoming more difficult since recently nematicides have been banned which are severe threats to health and environment. The observation that biotic factors of some soils act suppressive against plant-parasitic nematodes, and that this can be enhanced by organic soil amendments led to the suggestion for an integrated soil biology management. However, a directed soil biology management is impeded by a lack of knowledge on the species and processes that are involved in soil suppressiveness. In pre-experiments we showed that specific soil microbes attached to second-stage juveniles (J2) of nematodes, which migrate to and penetrate roots of the host plant. There the J2 evade the plant immune system, establish a feeding site, and build progeny. We recently showed for one soil that propagation can be significantly affected by soil microbial communities, while in two other soils suppression of the nematode was significantly lower. Our objective is to characterize the microbiome of J2 that they acquire in soil and investigate the specificity and ecological role of the microbial attachment, especially with respect to soil suppressiveness. It will be investigated whether the attached microbes interact with the plant immune system so that a better defence against the nematode is achieved. Specifically the following research questions will be addressed:Q1. Which microorganisms attach to J2 of endoparasitic nematodes in soil? To what extent is this microbial attachment to J2 specific for different soil types?Q2. To what extent the microbial attachment in a suppressive soil differs between populations or species of plant-parasitic nematodes? Does specificity of microbial attachment correlate with soil suppressiveness to the different nematodes?Q3. Attachment of which microbial species is correlated with suppressiveness of the soil towards propagation of the nematodes in roots or survival in soil?Q4. Is microbial attachment to J2 mediating soil suppressiveness towards the nematodes, or are microbes from suppressive soil rather directly interacting with the roots to induce systemic resistance against the nematode? Are genes, which are involved in the immune response of the plant, differentially expressed when nematodes invade the roots with attached microbes from suppressive compared to non-suppressive soil?The answers to these questions will be crucial for a further in-depth understanding of soil suppressiveness against plant-parasitic nematodes. The results will elucidate the involvement of induced host responses in soil suppressiveness, and provide the opportunity to better target measures within an integrated soil biology management for a sustainably productive agriculture.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Johannes Hallmann