Cool Grass, Hungry Caterpillars: How Temperature Shapes Endophyte-Mediated Resistance to Porina *

<p dir="ltr">* ISGME Programme title: <i>Temperature-driven variations in Epichloë endophyte-mediated porina resistance in perennial ryegrass</i></p><p dir="ltr">New Zealand’s pastoral systems rely heavily on perennial ryegrass (<i>Lolium perenne</i>), which are intentionally associated with selected <i>Epichloë</i> fungal endophytes that form a mutualistic symbiosis that protects the host against herbivorous insects through the production of alkaloids. The commercially available endophyte Epichloë LpTG-3 strain AR37 is a perennial ryegrass endophyte that confers resistance against the larvae of porina (<i>Wiseana</i> spp.), a significant pest in cooler regions of New Zealand. To expand pest management options, a newly identified strain of <i>Epichloë</i>, designated AR128 has been identified. This study investigates how temperature influences alkaloid concentrations in AR37 and AR128-infected perennial ryegrass and the subsequent effects on porina fitness, plant damage, and plant size. Perennial ryegrass plants, both with and without AR37 or AR128, were grown at three temperature regimes: 8°C, 13°C, and 18°C. After 4 weeks of growth, one porina larva was added to each plant, and left to feed for 8 weeks. Following this feeding period, the tillers were assessed for feeding damage using a scoring system from 0-5. Porina survival and weight gain were also measured. </p><p dir="ltr"><br></p><p dir="ltr"><br></p><p><br></p>