APS Abstracts of Presentations
First report of the pycnidial state of Phaeomoniella chlamydospora, a causal agent of black measles (esca) and Petri disease in California vineyards. A. ESKALEN, S. N. Rooney, and W. D. Gubler. Dept. of Plant Pathology, University of California, Davis, CA 95616. Phytopathology 92:S24. Publication no. P-2002-0167-AMA. Phaeomoniella chlamydospora is considered to be the primary pathogen causing esca and Petri disease. Previous studies have shown that Pa. Chlamydospora has the ability to produce pycnidia in culture. However, these structures had not been documented in California vineyards. Spore traps were placed in selected vineyards throughout the state. Spores of Pa. Chlamydospora were trapped from coastal counties and correlated with rainfall events. Grapevine tissues were collected from vineyards where spores were previously trapped. Tissues were washed and cultured on media. Results showed that spores of Pa. chlamydospora were found on grapevine cordons and pruning wounds of 2-3-year-old spurs. Pycnidia were observed beneath bark and on old pruning wounds. These pycnidia were similar to those that were artificially produced in culture. Spores from pycnidia were shown to be viable. Pathogenicity tests of spores from artificially and naturally produced pycnidia were compared. ITS regions from pycnidiospores were compared to that of known isolates of the Pa. chlamydospora.
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