Managers of forest and plantation ecosystems are encountering growing problems involving plant pathogens and the expanding geographic ranges of these pathogens. Historically unexposed stands are exceptionally vulnerable when a non-native pathogen is introduced because these pathogens can cause devastating disease in a host population that lacks co-evolved resistance mechanisms. One...
Pseudotsuga menziesii var. menziesii (coast Douglas-fir) is a tree of ecological, economic, and cultural value in its native North American Pacific Northwest (PNW) distribution. P. menziesii is host to a variety of well-documented endophytic foliar microorganisms, including the fungus Nothophaeocryptopus gaeumannii, the causal agent of Swiss needle cast (SNC), and...
Winter squash (Cucurbita maxima) grown in Oregon’s Willamette Valley for edible seed, frozen foods, and fresh markets is susceptible to an undiagnosed soilborne disease. Diseased squash fields exhibit symptoms of stunting, root and crown rot, vascular discoloration, and late-season wilt, which in extreme cases can lead to total crop failure....
Agrobacterium species transform plant cells by targeting a portion of plasmid-encoded bacterial DNA to the host nucleus. Genetic transformation by A. tumefaciens and A. rhizogenes requires secreted effector proteins. The tumor-inducing (Ti) plasmid from virulent A. tumefaciens encodes VirE2, a secreted single-stranded DNA-binding protein required for efficient transformation of hosts....
The Pacific Northwest (Oregon and Washington in the United States and British Columbia in Canada) is one of the major producers of red raspberry (Rubus idaeus L.) and blueberry (Vaccinium corymbosum L.) in the world. The expansion of growing area with these crops has resulted in the emergence of new...
This study explored the relationship of mature ponderosa pine (Pinus ponderosa Dougl. ex Laws) tree vigor and competitive zone density following thinning and fuel reduction treatments. Competitive zone density (CZD) was defined as the total tree basal area (m²/ha) surrounding a given ponderosa pine tree within a 10m fixed radius...
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Figure 9. Relationship of environmental variables to water potential at Lookout Mountain (LM
Invasive plants have the capacity to transform landscapes and alter ecosystem function, causing significant economic and ecological damage. These effects include displacement and reduction of native flora and fauna, altered fire regimes, modification of biotic and abiotic soil properties, as well as local, regional, and global economic impacts. With such...
Rhizopogon is a large genus of ectomycorrhizal (EM) fungi that grows in association with host trees of the family Pinaceae. We have conducted a series of studies investigating the ecology and evolutionary biology of the EM symbiosis shared between R. subgenus Villosuli and trees of the genus Pseudotsuga. Two members...
Vegetation patterns and species distributions are strongly linked to soil moisture regimes, and populations within a species from contrasting climatic regimes could exhibit differences in the degree to which certain functional traits related to establishment are expressed. Tree seedling survival is crucial for forest regeneration, and thus may be a...
Hypersensitive response-like (HR-like) needle reactions to infection by the white pine blister rust pathogen, Cronartium ribicola, have been reported for several species of five needle pines native to western North America. The best-studied examples are in Pinus monticola and P. lambertiana. In these species a "needle spot" phenotype has been...