ARS | Publication request: Genetics of Pathogen Fitness: Correlations with Virulence and Effects of Host Genotype

Submitted to: Society for the Study of Evolution
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 2010
Publication Date: N/A

Technical Abstract: In plant pathology, a large body of work has focused on changes in virulence, the traits allowing infection of otherwise resistant hosts, while relatively few studies have examined changes in quantitative fitness traits, those affecting the reproductive success of the pathogen after infection has occurred. Yet, quantitative reproductive traits are a critical component of pathogen fitness, and a clear understanding of the relationship between virulence and quantitative reproduction traits will provide insight into potential constraints on the evolution of virulence. We investigated the effects of pathogen virulence and host genotype on fitness traits of Puccinia coronata, the causal agent of oat crown rust. We found no significant correlation between the virulence level (the number of plant resistance genes a pathogen genotype can defeat) and within-host fitness in 29 isolates of P. coronata collected from across the Great Plains, suggesting that there is a not significant cost of virulence in the oat crown rust system. Next we asked if ecological mechanisms, such as host genotype could affect pathogen fitness. We measured fitness components of five pathogen genotypes on five different, susceptible host lines and found that host genotype strongly affects spore production and development time. Our results suggest that the evolution of virulence in P. coronata, a broadly distributed, sexually recombining plant pathogen is unlikely to be constrained by inherent fitness costs, but that ecological factors such as the host genotype and host diversity may play an important role.