P-424 - The role of temperature stress in plant-pathogen interactions: Insights from the barley-Zymoseptoria passerinii host-pathogen system

Understanding the combined effects of abiotic and biotic stress on quantitative disease resistance and plant-pathogen interactions is crucial for diminishing crop loss in the face of climate change. Plant responses to abiotic and biotic stress are well-studied individually, however, their concurrent impact remains unclear. Our research examines how temperature stress influences quantitative disease resistance and plant-microbe interactions in the barley (Hordeum vulgare) - Zymoseptoria passerinii system. We first characterized the responses of both barley and its pathogen to heat stress. Z. passerinii growth was restricted at 30°C, while chlorophyll fluorescence measurements suggest that barley tolerates 30°C without major signs of stress. However, we find that barley is influenced by temperatures above 32°C. To assess whether temperature influences early pathogen recognition, we performed a luminescence-based ROS burst assay in barley leaf discs using the elicitor laminarin, a β-1,3-glucan that triggers the biotic stress response. Luminescence measured at 20°C, 25°C, 30°C, and 35°C suggests that high temperatures (30°C, 35°C) enhance the ROS burst compared to lower temperatures (20°C, 25°C). We will further explore how mild and strong temperature stress influence infection progression, in particular the formation of necrosis and asexual spore structure (pycnidia) of Z. passerinii, to assess effects on quantitative disease resistance.