Abstract
Despite considerable studies on the adaptation of plant pathogens to qualitative resistance, few theoretical studies have investigated whether and how quantitative resistance can select for increased pathogen aggressiveness. In this paper, we formulate an integro-differential model with nonlocal effects of mutations to describe the evolutionary epidemiology of fungal plant pathogens in heterogeneous agricultural environments. Parasites reproduce clonally and each strain is characterized by several pathogenicity traits corresponding to the basic infection steps (infection efficiency, latent period, sporulation capacity depending on the age of infection). We first derive a general expression of the basic reproduction number ℛ0 for fungal pathogens in heterogeneous host environments, typically several cultivars cultivated in the same field (cultivar mixtures) or in different fields landscape (mosaics). Next, by characterizing the evolutionary attractors of the coupled epidemiological evolutionary dynamics, we investigate how the choice of quantitative resistances altering different pathogenicity traits impact the evolutionary dynamics of the pathogen population both at equilibrium and during transient epidemiological dynamics. We show that the model admits an optimization principle relying on an ℛ0 maximization approach for traits involved in the infection cycle after spore germination. We also highlight that within-host correlation between such traits (typically between the latent period and total number of spores produced during the infectious period) impact resistance durability and, more generally, how one may take advantage of evolutionary dynamics to increase the durability of quantitative resistance. Our analyses can guide experimentations by providing testable hypotheses and help plant breeders to design breeding programs.