Fungal Endophyte Infection and Host Genotype Jointly Modulate Host Response to an Aphid-transmitted Viral Pathogen

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Interactions between microbial pathogens and their hosts may be modified by other microbes, including mutualistic symbionts. B/CYDVs are aphid-transmitted, hostgeneralist plant viruses that can negatively impact natural and agricultural ecosystems. Endophytic fungal symbionts are vertically transmitted intercellular fungi that form obligate associations with grasses and relieve both biotic and abiotic stresses through the accumulation of alkaloids. In the greenhouse, we factorially manipulated virus infection and endophyte presence with two genotypes of tall fescue (Schedonorus phoenix), one in which the endophyte produces alkaloids (KY 31) and one that posses a novel endophyte that does not produce alkaloids (PDF). Endophyte infection decreased overall plant biomass for the KY 31 genotype but tended to increase overall plant biomass for the PDF genotype. Furthermore, endophyte infection altered plant response to virus infection. Across endophyte status and genotype, virus infection decreased the root fraction of endophyte-free plants, but when endophyte infection is taken into account, root allocation for virus infected plants increased. Overall, this work indicates that to understand the full impact of B/CYDV infection in plant hosts, we must not only consider the mutualists with which they associate but the origin of that association as well.


Presented at the 28th New Phytologist Symposium, Rhodes, Greece.