The Evolution and Ecology of Virulence in Xylella fastidiosa

Abstract

This thesis investigates the ecology and evolution of virulence in Xylella fastidiosa, a xylem-limited bacterium with significant impacts on countless important agricultural plant species. Through microfluidic chamber experiments simulating plant xylem conditions, we assess the potential of X. fastidiosa strain EB92-1 to be used as a biocontrol agent against the highly virulent Temecula strain. Our results demonstrate that Xylella fastidiosa strain EB92-1 can outcompete a more virulent strain within mixed culture. Additionally, we investigate strain interactions and colonization dynamics in tomato plants, revealing systemic colonization patterns and strain interactions important for developing effective biocontrol strategies. Drawing from individual-based simulation models, we explore the intricate interplay between genetic trade-offs, population structure, and virulence evolution in pathogen populations. We find a general set of conditions in which selection for improved pathogen performance in a vector can cause correlational and potentially maladaptive changes to virulence in the host. This research reveals the complex evolutionary and ecological factors shaping virulence in X. fastidiosa and informs future approaches for disease management in agricultural settings.