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....
Pyrenophora tritici-repentis (Ptr) is the necrotrophic fungus responsible for tan spot of wheat (Triticum aestivum). Ptr causes disease on susceptible wheat cultivars through the production and secretion of host-selective toxins (HSTs). HSTs are compounds that are only known to be produced by fungi and considered to be primary determinants of...
Production of the host selective toxin victorin is causal to pathogenesis of Cochliobolus victoriae on oats. The dominant Vb gene confers oat sensitivity to victorin, and is genetically inseparable from Pc2, which confers resistance to Puccinia coronata f. sp. avena. Victorin induces apoptotic-like cell death, and cell death is 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...
Modeling and analyzing the combined effects of disease and population dynamics
is important in understanding the effects of mechanisms such as pathogen transmission
and direct competition between host species on the distribution and abundance of different
species in an ecological community. Mathematical analysis of such models in a
spatially explicit...
The specificity of quantitative host resistance to plant disease has long been a controversial issue. We examined interactions between wheat (Triticum aestivum) and Mycosphaerella graminicola, causal agent of Septoria tritici blotch, to determine whether specific interactions occur between host and pathogen genotypes that could be involved in eroding quantitatively expressed...
In this dissertation I explore the application of two novel modeling techniques for improving risk analysis of vector-borne disease and discuss their potential use in integrating environmental risk assessment that guides environmental and public health decisions. Techniques for analyzing risk have been considered inadequate due to a lack of understanding...
The major objectives of this study were an
evaluation of the Meteorological Office Rainfall and
Evaporation Calculation System (MORECS) evapotranspiration
(ET) model using the Penman-Monteith equation and
comparison of the MORECS and measured surface resistance.
Meteorological, soil and plant parameters were measured in
an alfalfa field over two growing seasons....
The majority of our modern understanding of bacterial pathogenesis is based on the strategy that involves screening bacterial genomes for the presence of the genes encoding pathogenic factors, and analysis of these genes via forward and reverse genetics. Chlamydiae represent a unique group of pathogenic bacteria in which it is...