Modelling the evolution of pathogen virulence in forest pathosystems

For the understanding of forest diseases and their management, it is essential to couple epidemiology and evolutionary biology (Desprez-Loustau et al. 2016). Indeed, fungi have evolved diverse abilities to disperse, reproduce and infect different plants or organs. This evolution can occur over short time scales, in response to strong selective pressures exerted by the environment and/or management options. Because sustainable management of forest diseases must be designed at landscape scale and on long timeframes, modelling plays an essential role. We will present an individual-based model used to investigate the effects of management practices on virulence evolution in root rot fungi in pine plantations (Soularue et al. 2017). Based on quantitative genetics theory, this model is genetically and spatially explicit and makes possible to investigate the co-occurring evolutionary and epidemiology processes in practical contexts. Our simulations indicated that shortening the rotation length in pine plantations accelerates both the pathogen virulence and the development of the epidemics. The key influence of the level of genetic variation in emerging fungal pathogen populations was confirmed: it changed quantitatively both the evolutionary change of virulence and the speed of the epidemic. This modelling approach offers the opportunity to study evolutionary and epidemiological dynamics in various species and ecological contexts. It was adapted to the chestnut blight fungus