Multi-trophic interactions in the entomopathogenic fungus, Metarhizium spp.

Crop protection relies heavily on synthetic chemical pesticides. As a result of new legislation and the evolution of resistance in pest populations their availability is declining. One of the alternative tactics to pest management are biopesticides, agents based on living micro-organisms or natural products. Fungi in the Metarhizium complex (Hypocreales: Clavicipitaceae) are ubiquitous opportunistic pathogens of arthropods used worldwide as environmental friendly biopesticides. Even though Metarhizium play major role in natural ecosystems, the various interactions it is involved in are probably underestimated. To date, we know that the Metarhizium complex include both broad and narrow host-range pathogens of arthropods but also rhizosphere competent and plants endophytes. In a previous study we compared the pathogenesis process in different pathosystems including hosts that support infection (susceptible) and hosts that limit infections (resistant). We concluded that the composition of the host cuticle is a major factor determining successful fungal infection since it may support conidial germination and hyphal growth but, it may restrict penetration of hyphae into the hemoceol (host body cavity). Furthermore, the cuticle, the outer layer of the arthropod host, of a resistant host appears to contain compounds that actively suppress fungal growth and survival on the tick surface. Our current research focus on complex tri-trophic interactions occurring between EPF and plants, arthropods pests and beneficial organisms. We apply fungal transformation, live imaging and genetic approaches to reveal the high versatility displayed by EPF which mark it as a unique model organism but also as a flexible biopesticide product.