Comparison of host susceptibilities to native and exotic pathogens provides evidence for pathogen-imposed selection in forest trees

• Published in: The New phytologist Vol. 221; no. 4; pp. 2261 - 2272
• Main Authors: Freeman, Jules S., Hamilton, Matthew G., Lee, David J., Pegg, Geoff S., Brawner, Jeremy T., Tilyard, Paul A., Potts, Brad M.
• Format: Journal Article
• Language: English
• Published: England Wiley 01.03.2019; Wiley Subscription Services, Inc
• Subjects: Additives; Austropuccinia psidii (myrtle rust); coevolution; Corymbia citriodora; Corymbia citriodora ssp. variegata; disease resistance; Eucalyptus; Eucalyptus - genetics; Eucalyptus - microbiology; Eucalyptus globulus; forest tree; forest trees; Forests; Fungi; Fungi - physiology; Genetic diversity; genetic variation; Germplasm; Host plants; host resistance; Host-Pathogen Interactions; hosts; Inbreeding; indigenous species; Inheritance Patterns - genetics; introduced species; Pathogens; pathogen‐imposed selection; Plant population; Plant populations; Plant species; Population differentiation; Populations; Proliferation; Quambalaria; Quambalaria pitereka; Teratosphaeria; Trees - microbiology; Wild plants; pathogen-imposed selection; Eucalyptus globulus; host resistance; Teratosphaeria; Austropuccinia psidii (myrtle rust); Quambalaria pitereka; Corymbia citriodora ssp. variegata; forest tree
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.15557

• The extent to which spatial structuring of host resistance in wild plant populations reflects direct pathogen-imposed selection is a subject of debate. To examine this issue, genetic susceptibilities to an exotic and a coevolved native fungal pathogen were compared using two Australian host tree species. • Damage to common host germplasm of Corymbia citriodora ssp. variegata (CCV) and Eucalyptus globulus, caused by recently introduced (Austropuccinia psidii) and native (Quambalaria pitereka and Teratosphaeria sp.) pathogens was evaluated in common-garden experiments. • There was significant additive genetic variation within host species for susceptibility to both the exotic and native pathogens. However, susceptibility to A. psidii was not genetically correlated with susceptibility to either native pathogen, providing support for pathogen-specific rather than general mechanisms of resistance. • Population differentiation (Q ST) for susceptibility to the native pathogens was greater than neutral expectations (molecular F ST), arguing for divergent selection. Coupled with lower native, but not exotic, pathogen susceptibility in host populations from areas climatically more prone to fungal proliferation, these findings suggest that pathogen-imposed selection has contributed directly to a geographic mosaic of host resistance to native pathogens.