Nutrient application to external host environment stimulates internal viral-pathogen titer (2012)

Undergraduates: Briana Whitaker, Megan Rua

Faculty Advisor: Charles Mitchell
Department: Biology

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Availability of environmental resources can have direct benefits on the organisms consuming those resources, yet what happens if those resources also benefit the enemies that attack the original consumer? An abundance of nutrient resources in the external environment of a host may stimulate internal pathogen population growth to the detriment of the host; a host which could otherwise have benefitted from those resources. I utilized a greenhouse experiment consisting of plant-hosts and a factorial manipulation of nitrogen and phosphorus gradients in order to investigate the dynamics of nutrient-pathogen-host relationships. Both nitrogen and phosphorus increased total biomass of infected host individuals, yet the overall biomass increase coincided with a decrease in root allocation. By comparison, nutrient ratio (N:P) had a non-linear effect on plant biomass, with both low and high values of N:P causing decreases in host growth. Additionally, even after controlling for the influence of host biomass, increasing nitrogen increased viral titer; however, phosphorus additions and the N:P ratio were not found to be important factors in determining viral levels within the host. My results suggest that viral population growth may be greater in high-nitrogen habitats or host species, which will be of increasing concern as global deposition rates of nitrogen and the reliance on fertilizer in agricultural systems continue to rise.