Infection studies of Discula quercina, an endophyte of Quercus garryana

Abstract

Discula quercina is a ubiquitous endophyte in Oregon white oak (Quercus garryana). We determined which tree parts were infected with this endophyte, censused how infection levels in leaves varied on a temporal scale over the growing season and on a spatial scale between leaves and within leaves, and described growth patterns of the endophyte away from infection sites. The endophyte can be isolated from leaves, tree bark, acorn shells and cotyledons but rarely from wood. Infection in leaves is via rain dispersed conidia and increases with time and rainfall. When spring rains stop in Oregon, infection levels do not increase. Endophyte distribution between leaves is aggregated, within leaves the endophyte infections are more frequent along the midrib versus the lamina and gradually decrease in frequency from the petiole end of the leaf towards the distal end of the leaf. Methods used to successfully grow trees with leaves free of endophytes and consequences of infection by endophytes are discussed.

Key Words:

• Discula quercina
• endophyte
• horizontal infection
• infection cycle
• latent pathogen
• Oregon white oak
• Quercus garryana
• rain dispersed spores