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United States Department of Agriculture

Agricultural Research Service

Title: Evaluation of Lilac Cultivars for Susceptibility to Phytophthora Ramorum

Authors
item Grunwald, Niklaus
item Kitner, Megan - OREGON STATE UNIVERSITY
item Larsen, M - OREGON STATE UNIVERSITY
item Linderman, Robert
item Parke, J - OREGON STATE UNIVERSITY

Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2006
Publication Date: April 13, 2006
Citation: Grunwald, N.J., Kitner, M.L., Larsen, M.M., Linderman, R.G., Parke, J.L. 2006. Evaluation of lilac cultivars for susceptibility to phytophthora ramorum. Biological and Cultural Tests for Control of Plant Diseases. 21:O005.

Interpretive Summary: The relative susceptibility of 25 lilac species and cultivars to the pathogen Phytophthora ramorum causing Ramorum blight on lilacs was evaluated in detached leaf assays in the laboratory. Two experiments were conducted on 25 Aug and 28 Oct 2005. Three replications were conducted per treatment and isolate. Disease severity was assessed on 2 Sept and 4 Nov by evaluating percent lesion area. Percent lesion areas were averaged over both isolates and statistically analyzed to determine significant differences in resistance. Ramorum blight developed on all lilac species and cultivars evaluated. The factor cultivar had a significant effect on percent lesion area. Cultivars S. vulgaris cv. Ellen Willmott, S. x prestoniae cv. Minuet, and S. vulgaris cv. Katherine Havemeyer had less than 20% lesion area in both independent experiments and appear to be the most resistant.

Technical Abstract: The relative susceptibility of 25 lilac species and cultivars to Phytophthora ramorum was evaluated in detached leaf assays in the laboratory. The first experiment was started on 25 Aug 2005 and the second on 28 Oct. Three replications were conducted per treatment and isolate. Two isolates, namely D12A (A1 mating type isolated in OR) and Pr102 (A2 mating type isolated in CA), were grown on V8 agar for two weeks prior to inoculation. Leaves obtained from field-grown lilac were detached from cut shoots and stored overnight at 4°C. Leaves were placed in plastic containers with 300 ml moistened vermiculite. Separate plastic containers were used for different cultivars and isolates. Leaves were wounded using a flamed, sterile needle on either side of the midvein. Five mm V8 agar plugs were taken from isolate or control agar plates and placed upside down on the wounded site. After inoculation, contents were misted, and containers were incubated in a containment growth chamber at 20°C with a 14-hour light cycle for 8 days. Disease severity ratings were taken 2 Sept and 4 Nov by evaluating percent lesion area using ASSESS software (APS, St. Paul, MN). Percent lesion areas were averaged over both isolates and subjected to analysis of variance. Ramorum blight developed on all lilac species and cultivars evaluated. The factor cultivar had a significant effect on percent lesion area (P < 0.05). Cultivars S. vulgaris cv. Ellen Willmott, S. x prestoniae cv. Minuet, and S. vulgaris cv. Katherine Havemeyer had less than 20% lesion area in both independent experiments and appear to be the most resistant.

Last Modified: 11/22/2014
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