The dual symbiosis of the belowground arbuscular mycorrhizal fungus and aboveground Epichloë endophyte synergistically alleviates perennial ryegrass leaf spots caused by Bipolaris sorokiniana

Arbuscular mycorrhizal fungi (AMF) and Epichloë endophyte are two common symbiotic fungi that enhance plant resistance to stress, but their combined effect on plant responses to biotic stress remains unclear. Using RNA-seq techniques, we evaluated the impact of co-colonization of AMF Claroideoglomus etunicatum and Epichloë festucae var. lolii endophyte on perennial ryegrass (Lolium perenne) response to leaf spot disease caused by Bipolaris sorokiniana. Disease severity, phytohormones, analyzed the differential expression genes related to pathogen defence to perennial ryegrass with or without AMF and Epichloë were evaluated. The co-colonization of AMF and Epichloë reduced leaf spot severity, increased plant defence enzymes, particularly catalase (CAT) and polyphenol oxidase (PPO) in diseased plants. The co-colonization of AMF and Epichloë regulated plant disease resistance genes related to terpenoid backbone biosynthesis, biotin metabolism, and plant-pathogen interaction. Weighted Gene Co-Expression Network Analysis (WGCNA) identified 27 hub genes and 11 resistance-related genes specifically associated with the co-colonization. These findings enhance our understanding of the molecular mechanisms underlying the AMF-Epichloë synergy and their combined effects on perennial ryegrass resistance to leaf spot disease, thereby facilitating the utilization of symbiotic microorganisms in plant disease management.