Beckstead, Julie , Meyer, Susan E. , Bergen, Kelly M. , Dooley, Sandra R. .
Predicting the likelihood of disease from a fungal seed pathogen, Pyrenophora semeniperda, in a complex multi-host system using various seed traits.
Pyrenophora semeniperda is a naturally occurring fungal seed pathogen present in western North American seed banks in semi-arid plant communities. It is a generalist that infects multiple hosts, primarily grass species. Cheatgrass, Bromus tectorum, is an important host for P. semeniperda, due to high densities of seeds in its seed bank and vulnerability to pathogen-caused mortality because of slow-germinating seeds in the spring. Previously, it was found that cheatgrass can also act as an inoculum reservoir that enhances pathogen-caused mortality on co-occurring species. To predict which co-occurring species will likely be impacted by this pathogen, we examined its ability to infect and kill seeds of forty-three potential host species. To characterize seed traits that could mediate levels of disease, we assessed the phylogenetic relationships of the host species, seed germination characteristics (i.e., seed dormancy and germination rates), and seed morphological traits (i.e., seed size). Phylogeny was an important determinant of pathogen infection; species more closely related to cheatgrass, were more likely to be infected. However, phylogeny did not appear to predict seed mortality to the same degree as germination characteristics. Results showed that seeds with greater dormancy sustained greater death from the pathogen. Likewise, slow-germinating seeds experienced greater seed death. Seed morphology was not a good predictor of disease. Given that this seed pathogen has a relatively wide host range, is a naturally-occurring pathogen in semi-arid grasslands, and is under consideration as a biocontrol agent for cheatgrass, it is important that accurate host range predictions can be made. Results obtained here suggest that the rate of disease spread of P. semeniperda through a natural or restored plant community will depend on the phylogenetic structure of the plant community as well as seed germination traits of the species involved.
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1 - Gonzaga University, Department of Biology, 502 East Boone Avenue, Spokane, Washington, 99258, USA
2 - USDA Forest Service, Rocky Mountain Research Station, Shrub Sciences Laboratory, 735 N 500 E, Provo, Utah, 84606, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Wasatch B/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 9:15 AM