MiRA ESRs have been trained in specialized and transferable skills at five successful MiRA events and at secondments with other MiRA hosts. They have actively interacted in discussions and activities on scientific and practical issues within and across work packages, on career development within mentor groups, and outside MiRA through internet seminars and meetings. These activities have been supported by internal ESR progress reports and feedback, both at individual and consortium level, and by efficient project administration and communication.
The ESRs research focused on (1) context-dependency of MiR, (2) mechanisms and processes, (3) impacts on other beneficial biocontrol organisms, and (4) validation and economy in agriculture.
Effects of mycorrhizal fungi and other plant-associated fungi and bacteria on plant resistance varied depending on drought severity, light conditions, phosphorous and nitrogen availability, and exposure to plant pathogens. Wild tomato species, adapted to different climatic niches, have been evaluated for genotypic differences of microbe-induced resistance. The response of caterpillar’s gut microbiome, which can confer resistance to plant defences, has been evaluated for different combinations of plants and root-associated microbes.
Root-associated microbes, including bacteria and fungi, were found to induce resistance against different insects and plant pathogens through differential regulation of plant defences. Transcriptomic, metabolomic and bioinformatic analyses revealed that such resistance induction depends on phytohormone signalling and primed accumulation of plant chemical defences. Water and nutrient availability, and interactions with other microbes, were shown to impact this differential defence regulation, partly accounting for the context-dependency of the microbially induced plant resistance. Thus, our results confirm that context-dependency of MiR is associated with changes in defence signalling and responses, and identify jasmonates and other fatty acid derivatives, together with phenolic compounds and steroidal glycoalkaloids, as key mediators of MiR in tomato.
Mycorrhizal fungi predominantly reduced survival and growth of herbivores, although the degree depended on environmental conditions (e.g. nutrients). Mycorrhiza generally did not impede parasitoid and predator performance or foraging capacities, suggesting compatibility of resistance-inducing fungi with other biocontrol agents. Mycorrhizal fungi modulated volatiles in different tomato varieties attacked by herbivores, including compounds known to attract generalist predators. The ability of tomato to enhance resistance against pests in response to mycorrhizal inoculation was stronger in a modern domesticated than in ancient varieties.
Root inoculation with beneficial microbes alone and in consortia affected insect herbivore performance negatively and some combinations protected the plants against leaf and root pathogens. Root inoculation methods were developed for beneficial bacteria, Trichoderma and plant-associated insect-pathogenic fungi, and compatibility with mycorrhizal fungi evaluated. Such combinations seem to reduce pathogen performance on tomato leaves confirming systemic effects. Predatory insect larvae were found to transfer beneficial bacteria with their mouthparts from colonized plant material or artificial diets to other plants. Methods for in-planta PCR detection of these bacteria were developed.
The surveys conducted amongst stakeholders suggest that MiR-based innovations face several challenges for future adoption, such as lack of information on ecological and economic effects. The surveys concluded that attitude, norms, and perceived usefulness of MiR innovations are significant predictors of farmers’ intentions to adopt MiR innovation.
