Wheat stripe rust (WSR), also called yellow rust of wheat (Tricitum spp.), causal agent Puccinia striiformis f.sp. tritici (Pst), is a foliar disease of major economic importance on wheat, especially grown in temperate locations. WSR causes major losses of wheat yield, estimated at nearly $ 1 billion per year, and...
Primary disease gradients of wheat stripe rust, caused by the aerially dispersed fungal pathogen Puccinia striformis, were measured in Madras and Hermiston, OR in the springs of 2002 and 2003. Disease foci were created by inoculating a 1.52m x 1.52m area in each of three replicate field plots (6.1m wide...
At the intersection of basic science research and clinical relevance, cancer metastasis and cell invasion is a multifaceted problem that has been investigated for the past several decades. Importantly, cancer cell plasticity, the ability of a single cell to change its phenotype without genetic mutations in response to environmental cues,...
The public controversy over possible health hazards from radioactive fallout from atomic bomb testing began in 1954, shortly after a thermonuclear test by the United States spread fallout world wide. In the dissertation, I address two of the fundamental questions of the fallout controversy: Was there a threshold of radiation...
A study consisting of three parts was undertaken to investigate how variation in species interactions, population genetic structure, epidemiological parameters, and plant breeding system may influence the ecology and biological control of an apomictic invasive plant, Chondrilla juncea (Asteraceae). Interactions between natural enemy species may modify their net effect on...
Disease detection through traditional techniques such as scouting fields on foot, molecular assays, or morphological identification of plant pathogens is time consuming and costly. Disease diagnosis in the field can be extremely subjective, and largely depends on the experience and knowledge of pathogen identification and disease quantification. This thesis provides...
Grapevine red blotch virus (GRBV), the causal agent of red blotch disease (RBD) in grapevine, Vitis vinifera L., is an emerging pathogen of significance to the wine grape industry of Oregon, USA. To address knowledge gaps of GRBV epidemiology, spread of GRBV was evaluated in Oregon vineyards over four years....
Bacterial soft rot of potato (Solanum tuberosum), caused by Pectobacterium and Dickeya species, is among the most common and destructive potato diseases in the United States. These pathogens cause a variety of vascular wilts, and in potato cause a disease complex that includes tuber soft rot, blackleg, aerial stem rot,...
Podosphaera macularis, causal agent of hop powdery mildew, is known to produce cleistothecia (syn. chasmothecia) in eastern North America and Europe, but ascocarps are not reported from the Pacific Northwestern region of North America. Reasons for the apparent absence of cleistothecia in the Pacific Northwest are unknown. We established that...
Plant pathogens in the genus Phytophthora are known to cause disease on field crops, nursery plants, and forest trees. The best known example probably is Phytophthora infestans, which triggered the infamous Irish potato famine. Other important Phytophthora species include: P. ramorum (sudden oak death pathogen), P. sojae (soybean root rot...