Herbivore-specific induction of defence metabolites in a grass-endophyte association

Plants have developed a variety of defence strategies against herbivores. One possible strategy is the induced production of metabolites following herbivore attack. Plant-associated micro-organisms can be the source of such defensive compounds. For example, cool-season grasses can be associated with systemic endophytic fungi of the genus Epichloё, which produce herbivore-toxic alkaloids. In a controlled common garden approach, we tested the hypothesis that different types of herbivory induce endophyte growth and increase the endophyte-mediated production of three bioactive alkaloids which can deter or toxify herbivores. During 18 weeks, we analysed biweekly endophyte and alkaloid concentrations in the grass Lolium perenne infected with the endophytic fungus Epichloё festucae var. lolii. The experiment was conducted throughout the field season and compared three different herbivore treatments to the control treatment (herbivory exclosure). We showed that the concentration of the verteb...