Pathogen and host genotype differently affect pathogen fitness through their effects on different life-history stages

Emily Bruns, Martin Carson, Georgiana May

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Background: Adaptation of pathogens to their hosts depends critically on factors affecting pathogen reproductive rate. While pathogen reproduction is the end result of an intricate interaction between host and pathogen, the relative contributions of host and pathogen genotype to variation in pathogen life history within the host are not well understood. Untangling these contributions allows us to identify traits with sufficient genetic variation for selection to act and to identify mechanisms of coevolution between pathogens and their hosts. We investigated the effects of pathogen and host genotype on three life-history components of pathogen fitness; infection efficiency, latent period, and sporulation capacity, in the oat crown rust fungus, Puccinia coronata f.sp. avenae, as it infects oats (Avena sativa). Results: We show that both pathogen and host genotype significantly affect total spore production but do so through their effects on different life-history stages. Pathogen genotype has the strongest effect on the early stage of infection efficiency, while host genotype most strongly affects the later life-history stages of latent period and sporulation capacity. In addition, host genotype affected the relationship between pathogen density and the later life-history traits of latent period and sporulation capacity. We did not find evidence of pathogen-by-host genotypic (GxG) interactions. Conclusion: Our results illustrate mechanisms by which variation in host populations will affect the evolution of pathogen life history. Results show that different pathogen life-history stages have the potential to respond differently to selection by host or pathogen genotype and suggest mechanisms of antagonistic coevolution. Pathogen populations may adapt to host genotypes through increased infection efficiency while their plant hosts may adapt by limiting the later stages of pathogen growth and spore production within the host.

Original languageEnglish (US)
Article number135
JournalBMC evolutionary biology
Issue number1
StatePublished - 2012

Bibliographical note

Funding Information:
We thank Jerry Ochocki (USDA Cereal Disease Lab) and Julia Beni (undergraduate research assistant) for their help growing and inoculating plants.We also thank Ruth Shaw, Peter Tiffin and two anonymous reviewers for valuable comments on the manuscript. A Hatch Grant (MIN-71-024) from the Minnesota Agricultural Experiment Station and Department of Plant Biology at the University of Minnesota and an NSF grant (1045608) funded the work.


  • Avena sativa
  • Density-dependence
  • Fitness
  • Host-pathogen interactions
  • Life history
  • Pathogen reproductive rate
  • Puccinia coronata


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