LB 30-252 - The effects of arbsucular mycorrhizal fungi on volatile mediate communication in response to insect herbivory in tomato plants

Plants damaged by insect herbivores (i.e., emitters) emit a complex blend of volatile organic compounds (VOCs) to which neighbor plants (i.e., receivers) react by priming their defenses and becoming more resistant to herbivores, a phenomenon termed plant communication. This process has been documented in a wide variety of plant species, but its context-dependency remains underexplored. For instance, associations with beneficial organisms such as arbuscular mycorrhizal fungi (AMF) can promote the emission of VOCs and induce resistance in plants, thus enhancing plant communication. To test this hypothesis, I paired emitter and receiver tomato plants (Solanum lycopersicum) in a crossed factorial design to examine the effects of AMF-plant associations on VOC-mediated communication in response to herbivory by the generalist chewing insect Spodoptera exigua. I first tested whether receiver plants paired with herbivore-damaged emitters were more resistant to S. exigua than receiver plants paired with undamaged emitters (i.e., test of plant communication). Then, I tested whether plant communication was stronger when emitter or receiver plants were inoculated with AMF. I did not observe increased induced resistance in receivers exposed to VOCs from herbivore-induced emitters, with the exception of a weak response in receivers inoculated with AMF. Specifically, AMF-inoculated receivers paired with herbivore-induced emitters had lower damage than AMF receivers paired with control emitters. Surprisingly, I observed that root colonization by AMF in inoculated receiver plants was greater when these were paired with herbivore-induced emitters vs. control emitters, suggesting that plant-plant communication also acts by promoting stronger AMF associations.