Effects of varying ratios of the mineral nutrients nitrogen, phosphorus and sulfur, on Neotyphodium endophyte-mediated resistance in tall fescue (Schedonorus arundinaceus (Schreb.) Dumort)

Fungal endophytes in the genus Neotyphodium have evolved symbiotic relationships with several important turf and forage grass species. While the fungus benefits from access to plant nutrients and structural support provided by the plant, the plant benefits from resistance to herbivory, through the production of alkaloids, and enhanced environmental stress tolerance. Alkaloid concentrations in endophyte infected plants are known to vary with the availability of certain resources, particularly soil nutrients, which can also alter plant biochemical pathways involving plant storage compounds, growth, and metabolism. Even though several studies have examined the influence of individual nutrients on endophyte mediated resistance, the effects stemming from mixtures of available nutrients remain largely unknown. Therefore the focus of my project is to evaluate how varying ratios of three essential mineral nutrients (nitrogen, phosphorus and sulfur) influence the relationship between plant growth (root and tissue biomass), biochemical pathways (carbohydrates and amino-N) and defense (alkaloid concentration) in endophyte-infected tall fescue, and how potential trade-offs between these competing pathways influences herbivory by fall armyworm (Spodoptera frugiperda). The results and implications of this study will be discussed.