Genetic and ecological constraints to the evolution of virulence and reproduction in a plant pathogen

Abstract

Hosts and pathogens are engaged in an ongoing evolutionary struggle. In humanmanaged systems, rapid evolution of pathogen populations can reduce the effectiveness of important control methods such as antibiotics and genetic resistance in crop species. My thesis research investigates potential constraints to pathogen evolution by examining genetic and ecological factors affecting the evolution of infection and reproduction in the plant pathogen Puccinia coronata. I first investigate genetic variation underlying three pathogen life history stages within the host and show that variation in pathogen life-history stages within the host is affected by both the pathogen and host genotype. Next, I evaluate the relationship between pathogen infection and reproduction and show evidence of a trade-off between the number of resistant host genotypes infected and two key pathogen life history traits. Finally, I quantify the variation in infection and reproduction among eight different agricultural populations of P. coronata and ask whether the genetic diversity of the host population affects the evolution of pathogen infection and reproduction. While I do not find conclusive evidence that host genetic diversity affects the evolution of these traits, I do I find significant variation among populations that is not explained by pathogen population structure, indicating that selection structures pathogen populations.