Characterization of interactions and their mechanisms between replant disease and soil mesofauna (Collembola)

• Applicant: Professor Dr. Rainer Meyhöfer
• Subject Area: Plant Breeding and Plant Pathology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 523608346

Apple replant disease (ARD) is considered worldwide as an important soil born disease with negative impact on yield and tree growth in apple production. It occurs mainly when apple trees (Malus domestica Borkh.) are repeatedly regrown on the same site. Causal factors are up to know not fully understood, but alterations in the microbial and nematode community as a response to apple trees seem to play a major role. Within the soil ecosystem complex interactions between soil properties, faunal vectors, and trophic cascades occur, and include genotype specific effects on plant secondary metabolism. Own results so far show negative effects of ARD on biodiversity of the soil mesofauna as well as negative behavioral responses of several Collembola species. The objectives of the project are to investigate the fundamental mechanisms of Collembolan strong avoidance of apple replant diseased soil in detail. Our major interests are to characterize the behavioural mechanisms, to identify the ARD related cues, which trigger Collembolan behaviour and to analyse signal interactions (multisensory orientation). Most likely volatile organic compounds (VOCs) are responsible for behavioural responses but other secondary metabolites, e.g. feeding or contact cues, cannot be ruled out fully now. Therefore, ARD causing organisms (i.e., bacteria, fungi and oomycetes), which are identified by the ORDIAmur project group, will be used to investigate their specific effect on Collembolan behaviour in bio test setups ranging from no-choice to choice situations under constant environmental conditions. To underline the relevance of cues over evolutionary timescales the impact on insect fitness will be additionally considered. Based on the results specific cues will be chemically characterised by GC-MS. The relevance of major compounds will be confirmed by behavioural bioassays. Finally, bio tests will be setup to study the interaction between different stimuli, i.e. olfactory cues and feeding stimulants, to rank the importance of the information content in general. Our results will highlight the impact of ARD causing fungal pathogens on behavioural ecology of important Collembola species and contribute to the identification of novel substances that could be of major interest for development of strategies overcoming ARD and to control other important soil born pests, e.g. wireworms or grubs.

• DFG Programme: Research Grants
• Co-Investigators: Privatdozent Dr. Ulrich Krings; Dr. Torsten Meiners