Increased tolerance to Phytophthora cinnamomi in offspring of ink-diseased chestnut (Castanea sativa Miller) trees

International audience; AbstractKey messageIncreased tolerance toPhytophthora cinnamomiwas observed in small-sized offspring of ink-diseased chestnut trees, suggesting that a virulent pathogen can trigger a defence response of trees in the subsequent generation. Increased tolerance to water stress was not observed in offspring of chestnut trees.ContextIn sweet chestnut (Castanea sativa Miller), P. cinnamomi Rands is responsible for the widespread and destructive ink disease.AimsWe investigated if the susceptibility of C. sativa to water stress and P. cinnamomi depends on the health status of mother trees.MethodsPlants were grown from seeds collected from healthy and ink-diseased chestnut trees. Leaf wilting after drought exposure and plant mortality after pathogen inoculation were assessed.ResultsOffspring of ink-diseased trees had poorer performance in plant height and root biomass than offspring of healthy trees, with allocation of biomass to seeds mediating this effect. Leaf wilting due to water stress was similar in offspring of healthy and P. cinnamomi-infected trees. However, increased tolerance to P. cinnamomi was observed in small-sized seedlings, suggesting that tolerance in C. sativa may involve growth costs. This is the first report of increased tolerance to P. cinnamomi in plants germinating from a diseased tree.ConclusionThe results suggest that an invasive pathogen can regulate the performance and prime a defence response of a forest tree species in the subsequent generation, and generate conflicting selection pressures related to plant size.