Plants have evolved fine-tuned mechanisms to fight enemies based on a conserved immune system that allows the recognition of aggressors and the activation of multifaceted defence mechanisms, including physical and chemical barriers and genetic, protein and chemical defences. This basal resistance or innate immunity can be enhanced by multiple stimuli, including beneficial microbes, leading to
Induced Resistance (IR). As a consequence, there is a great potential for the integration of IR inducing microbial inoculants as bioestimulants and biopesticides in Integrated Pest Management (IPM) programs. IR is usually associated with defence priming, consisting in a boost of plant immunity leading to a more efficient activation of defence mechanisms upon challenge. Among beneficial microbes inducing IR, arbuscular mycorrhizal fungi (AMF) are of great interest as they colonize the roots of most plant species, including crops, providing multiple benefits to the host plant. Remarkably, mycorrhizal plants are more resistant to pathogens and pests, a phenomenon known as MIR (Mycorrhiza Induced Resistance). MIR is strongly context dependent and multiple factors may influence their performance, including the partners genotypes, plant nutritional status, environmental conditions and the biotic context. On the other hand, AM symbiosis and MIR also influence the surrounding ecosystem by modifying plant interactions with insects and microbes. In previous projects (RESISTEMIC and MIRtoPest), we focused on the mechanisms underlying MIR and defence priming in tomato plants against the foliar fungal pathogen Botrytis cinerea and the chewing insect Spodoptera exigua. Although MIR is context-dependent and involves a horizontal multicomponent defences that may vary with the challenger, common molecular features were identified. In this sense, we confirmed that MIR is based on priming of JA-regulated defences, and identified as number of primed metabolites in the different pathosystems. Our goal now is to expand and deepen our knowledge into pests of economic
interest, such as Tuta absoluta and Tetranychus urticae, addressing the molecular mechanisms and the modulatory role of P and N fertilization in the success of MIR. We also aim to evaluate the indirect impact of MIR on neighboring plants and on third trophic levels, the natural enemies of these pests, such as infecting bacterial and viral entomopathogens, predators and parasitoids. High-throughput -omics will provide very useful information about the complex biological processes regulating plant interactions with microbes and pests. Integrating multi-omics data using robust bioinformatics and data mining tools can lead to the identification of relevant correlations and the construction of hierarchical models describing the regulation of different processes and helping in the identification of common priming fingerprints related to MIR. Overall, PRIME4MORE aims to characterize MIR against the devastating pests T. absoluta and T. urticae in crops with high economic value such as tomato and citrus. We aim to identify common fingerprints and regulation cascades orchestrating plant immune priming in MIR, evaluate the impact of nutrient availability on the phenomena and assess how MIR influences pest natural enemies, with the final
goal of integrating AMF and MIR in IPM programs.