APS Abstracts of Presentations

Another canker-causing Phytophthora from California and Oregon forest trees. J. M. Davidson (1), M. Garbelotto (2), E. M. Hansen (3), P. REESER (3), and D. M. Rizzo (1). (1) Dept. Plant Pathology, U.C. Davis, Davis, CA 95616; (2) Dept. Environmental Science, Policy, and Management, U. C. Berkeley, Berkeley, CA 94720; (3) Dept. Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331. Phytopathology 92:S17. Publication no. P-2002-0122-AMA.

Phytophthora ramorum causes sudden oak death on tanoak and coast live oak trees, and foliar and dieback symptoms on other tree species. A second, apparently undescribed Phytophthora species is occasionally isolated from lethal cankers on tanoak and coast live oak, and from foliar lesions on tanoak and myrtlewood, in areas where P. ramorum is also active. ITS DNA sequence indicates close relationship to P. ilicis (a foliar pathogen of holly) and P. psychrophila (newly described from European oak forest soils). It is homothallic with amphigynous antheridia, and has deciduous sporangia. It grows more slowly, with a lower temperature optimum, than P. ramorum. In log inoculation tests it is nearly as pathogenic to tanoak as P. ramorum. It does not infect holly leaves in leaf inoculation tests. In the forest it is usually associated with single killed trees, in contrast to the expanding patches of mortality caused by P. ramorum.

Copyright 2002 by The American Phytopathological Society. All rights reserved.