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Susceptibility of Pacific yew (Taxus brevifolia Nutt.) to Phytophthora lateralis

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dc.contributor.advisor Hansen, Everett M.
dc.creator Murray, Marion S.
dc.date.accessioned 2012-11-21T20:48:56Z
dc.date.available 2012-11-21T20:48:56Z
dc.date.copyright 1995-04-10
dc.date.issued 1995-04-10
dc.identifier.uri http://hdl.handle.net/1957/35176
dc.description Graduation date: 1995 en_US
dc.description.abstract In 1991 Pacific yew (Taxus brevifolia Nutt.) was reported as a new host for Phytophthora lateralis Tucker and Milbrath which is an aggressive root rot pathogen thought previously to be specific to Port-Orford-cedar. This study was designed to compare the pathogenicity of P. lateralis on the two hosts, and to characterize sites where Pacific yew mortality occurs. The specific objectives were: 1) compare root colonization and mortality of Pacific yew and Port-Orford-cedar seedlings and rooted cuttings; 2) compare lesion length on inoculated Pacific yew and Port-Orford-cedar branches and stems; 3) compare zoospore attraction to freshly cut Pacific yew and Port-Orford-cedar rootlets; 4) compare amount of mortality of Pacific yew and Port-Orford-cedar in infested drainages and determine extent of yew mortality; and 5) characterize sites where P. lateralis causes Pacific yew mortality. Root colonization of P. lateralis was significantly greater in cedar than in yew. Seedling mortality averaged 58% for cedar and 4% for yew. Lesion length on the cedar seedling stems was twice the lesion length on yew stems, and cedar branches had lesions four times longer than yew branches. Abundant zoospore aggregation occurred on cedar rootlets along the zone of elongation and the region of maturation. In comparison, far fewer zoospores encysted along the yew rootlets, and were concentrated on the root hairs. The stream survey of three infested drainages in southwest Oregon and northwest California revealed a total of 1199 dead Port-Orford-cedar (46% mortality), and 86 dead Pacific yew (10% mortality). At sites where P. lateralis-induced mortality occurred, the interaction of slope and distance from the stream was negatively correlated with tree death. Based on results of this study, we conclude that Pacific yew is less susceptible to P. lateralis than Port-Orford-cedar, but that mortality of Pacific yew in the field is greater than previously reported. In addition, Pacific yew mortality was observed most often on level to nearly-level sites close to the stream's edge where root exposure to P. lateralis-infested water was frequent in scope and duration. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Pacific yew -- Diseases and pests -- Oregon en_US
dc.subject.lcsh Pacific yew -- Diseases and pests -- California en_US
dc.subject.lcsh Phytophthora diseases -- Oregon en_US
dc.subject.lcsh Phytophthora diseases -- California en_US
dc.subject.lcsh Phytophthora lateralis -- Oregon en_US
dc.subject.lcsh Phytophthora lateralis -- California en_US
dc.title Susceptibility of Pacific yew (Taxus brevifolia Nutt.) to Phytophthora lateralis en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Master of Science (M.S.) in Plant Pathology en_US
dc.degree.level Master's en_US
dc.degree.discipline Science en_US
dc.degree.grantor Oregon State University en_US
dc.description.digitization File scanned at 300 ppi (Monochrome, 8-bit Grayscale) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us

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