Data from: The effectiveness and costs of pathogen resistance strategies in a perennial plant

Plants have evolved different strategies to resist pathogens, but little
is known about how effective, stable and costly these mechanisms are in
perennial plants across multiple growing seasons. We conducted a
laboratory experiment to assess resistance variation in Plantago
lanceolata against the powdery mildew-causing fungus Podosphaera
plantaginis and to measure possible trade-offs between the different
resistance strategies. To test stability and costs of resistance, we
established common garden populations of plants possessing three different
resistance strategies: qualitative resistance that is the ability to block
pathogen infection, quantitative resistance that is the ability to
mitigate pathogen development and susceptibility. We measured their
performance with and without disease for 3 years. There were no trade-offs
between qualitative and quantitative resistance, and the components of
quantitative resistance were positively correlated. Throughout the 3-year
common garden study, pathogen loads were significantly affected by host
resistance in the study populations. Qualitative resistance efficiently
blocked infections but contrary to laboratory obtained results;
quantitative resistance did not hinder epidemic growth. We detected costs
in plant performance for qualitative and quantitative resistance compared
to susceptible plants in absence of the pathogen. The costs of infection
varied according to resistance strategy, pathogen load and plant age.
Synthesis. In perennial plants, the costs and benefits of resistance need
to be evaluated over multiple years as they may change with plant age. Our
results give new insights into how polymorphism in resistance can be
maintained through costs of resistance in plant performance and through
shifts in resource allocation between vegetative growth and reproduction
under infection.