9520662 CLAY Parasites may be important evolutionary agents for the maintenance of genetic diversity and reproduction in many species. Plants can either self-fertilize or outcross with another plant. The latter produces greater genetic variability than self-fertilization. Although many plants can use both mechanisms, the conditions in which mixed systems are advantageous are not well understood. Danthonia spicata is a grass that can reproduce through outcrossing and selfing flowers. When infected with the fungus Atkinsonella hypoxylon, the development of outcrossing flowers is prevented and a fungal structure that bears infective spores develops in its place. The fungus can also spread by infecting the seeds produced through selfing. This parasite strategy of preventing outcrossing has been observed in other systems and might be advantageous for the parasite to reduce genetic variability of host plants or because more plant resources are available for fungal reproduction. This project will investigate whether the fungus A. hypoxylon acts to maintain the mixed reproductive system in the host D. spicata, and how the host's reproductive system affects the success of the parasite. The advantage of each fungal transmission mode (contagious spread or infection of host seeds) is of interest because each mode is associated with different levels of parasite effect on the host and can lead to different disease spread patterns. Comparison of the host success through selfing and outcrossing in the presence of pathogens will shed light on the importance of maintaining genetic diversity in plants. This information is important for constructing conservation policies for minimizing disease damage in endangered species. It will also be of potential value for developing better agricultural practices to alleviate pathogen damage to crops.
