Development of Differential Screening Panels for Slash Pine-Fusiform Rust Reaction Types

Understanding the genetic basis for disease resistance is crucial to ensure a successful breeding and deployment strategy for slash pine. A complementary genetic interaction model has been hypothesized for the pine-fusiform rust pathosystem. In such a model, resistance is due to a major gene effect that confers resistance to some strains of pathogens, but not others. If this model for the pine-fusiform rust pathosystem is correct, it will be necessary to identify the genes for resistance in order to develop successful strategies. Some resistance genes are dispersed throughout the genome and can be identified by genetic mapping. However, resistance genes may be clustered in the host and it may be possible to identify them only by empirically determining their differential interaction with different pathogen strains. In the latter case, it will be necessary to develop a panel of slash pine parents that can be used to screen for presence/absence of avirulence among collections of the pathogen and a panel of pathogen strains that can be used to screen for presence/absence of resistance genes in the host. The feasibility of developing such screening panels was tested by evaluating 43 slash pine (Pinus elliottii, Engelm. var elliottii) parents with 8 single-urediniospore cultures of Cronartium quercuum f. sp. fusiforme. The slash pine parents were selected to include a range of resistance levels based on their performance in an earlier screening trial. Each parent was control-pollinated with a pollen mix collected from 10 trees known to be highly susceptible to bulk inocula. The 8 inocula were derived from eight single-urediniospore rust cultures obtained from galls from across the southeastern USA. Examination of the reaction data under the assumption of a gene-for-gene host:pathogen system allowed us to infer the presence of at least 8 putative genotypes for resistance in the host and pathogenicity in the fungus, suggesting that screening panels can be developed with current propagation technologies.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

The Impact of Biofilms and Dissolved Organic Matter on the Transport of Nanoparticles in Field-Scale Streams

The fate and transport of nanoparticles (NPs) in streams is critical for understanding their overall environmental impact. Using a unique field-scale stream at the Notre Dame-Linked Experimental Ecosystem Facility, we investigated the impact of biofilms and the presence of dissolved organic matter (DOM) on the transport of titanium dioxide (TiO2) NPs. Experimental breakthrough curves were analyzed using temporal moments and fit using a mobile-immobile model. The presence of biofilms in the stream severely reduced the transport of the TiO2 NPs, but this was mitigated by the presence of DOM. Under minimal biofilm conditions, the presence of DOM increased the mass recovery of TiO2 from 4.2% to 32% for samples taken 50 m downstream. For thriving biofilm conditions only 0.5% of the TiO2 mass was recovered (50 m), but the presence of DOM improved the mass recovery TiO2 to 36%. The model was suitable for predicting early, peak, tail, and truncation time portions of the breakthrough curves, which attests to its ability to capture a range of processes in the mobile and immobile domains of the stream. The model outcomes supported the hypothesis that DOM changed the interaction of NP-biofilm from an irreversible to a reversible process. Collectively, these outcomes stress the importance of considering biogeological complexity when predicting the transport of NPs in streams

Characteristics And Role Of The Mite, Phyllocoptes fructiphilus (Acari, Eriophyidae) In The Etiology Of Rose Rosette

Volume: 97Start Page: 163End Page: 17