Anatomical Examination of Phytophthora ramorum Infection in Camellia

Elizabeth Geltz, Jessica McHugh, Lisa Baird, Department of Biology, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, 619-260-4073, baird@sandiego.edu; Sibdas Ghosh, Peter Thut, Department of Natural Sciences and Mathematics, Dominican University of California, San Rafael, CA 94901; Mietek Kolipinski, National Park Service, Pacific West Regional Office, Oakland, CA 94607

In spring 2004 Phytophthora ramorum infection of camellia plants was reported at multiple nursery sites in California. Our research was initiated to examine the mode of infection of camellia plants with P. ramorum at the whole plant and cellular level. Camellia leaves were infected with P. ramorum via zoospores or plug inoculation. Leaf samples were harvested 3 hours and 1, 2 and 4 days after infection and fixed immediately for light and electron microscopy. Examination with light and scanning electron microscopy indicate that possible anatomical pathways for infection of camellia leaves include stomates and large sub-epidermal oil glands located on abaxial surfaces of leaves. Preliminary scanning electron microscopy in our laboratory indicates that stomates are the most likely site of initial infection.

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