9509034 Jarosz The potential for cytoplasmic hyperparasites to influence the dynamics of plant-pathogen interactions will be the focus of this collaborative research project. The theoretical portion of the research has three objectives: (1) to identify conditions that allow the hyperparasite to invade a pathogen population, (2) to generate predictions on the effects that hyperparasite invasion has on plant-pathogen population dynamics, and (3) to generate predictions on long-term evolutionary dynamics of the plant-pathogen-hyperparasite system. Empirical studies will examine the chestnut blight system involving the American chestnut, the fungal parasite of chestnut, and a double stranded (ds) RNA hyperparasite of the fungus. One experiment will test predictions for the distribution of dsRNAs within chestnut populations, and the diversity of vegetative compatibility groups with and among fungal populations. A second study will evaluate the genetic interaction between the fungus and dsRNA in determining pathogen virulence. The relation between pathogen virulence and disease transmission rates will be evaluated in a third experiment. This work will determine the influence of hyperparasite infection on the relationship between virulence and transmission rate. The last experiment will test model predictions on the relative transmission rates of dsRNA-free and dsRNA-infected lines that allow dsRNAs to invade fungal populations.
