RUI: Mediation of Induced Resistance to Insects by a Fungal Endophyte

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9527749 Bultman The presence of an endophytic fungus is often associated with enhanced survival and reproduction of the host grass. Because insect herbivores often cause less damage to grasses infected by the fungi compared to grasses lacking the fungal associates, the grass-fungus association has been described as a defensive mutualism. A hypothesized mechanism for this defense may be fungal-produced alkaloids that can be toxic to insects. The proposed study specifically tests if the advantage of endophyte infection to grasses is due to enhanced resistance to insects following plant damage. Laboratory experiments manipulating nutrient levels, plant damage, and fungal infection will be conducted using Chewings, hard, and tall fescues and perennial ryegrass. Plant tissue will be fed to fall and true armyworm larvae and their growth and survival monitored to assess the presence and magnitude of base level and wound-induced resistance in fungal-infected and fungal-free plants. The level of plant protein nitrogen and alkaloids will also be monitored to help interpret differences in insect performance among experimental treatments. Biomass gain and consumption of the two insect herbivores will be assessed to further evaluate mechanisms responsible for treatment effects on insect performance. The economic significance of fungal endophytes of grasses is well documented. The fungi, and the toxins they produce, have detrimental effects on livestock that translate to annual revenue losses of over $600 million in the US. The proposed research, by providing information on the basic ecology of grass endophytes, should assist efforts to manage them in agricultural settings.