Virulence evolution through a latency-transmission trade-off Implications as to the durability of resistance in agriculture

In evolutionary epidemiology, most of the existing models address virulence evolution through a transmission-virulence trade-off. Although some models consider a coupling with other host-parasite interaction features such as clearance, there seem to be no model considering a coupling with a trait which is however often measured, and may have some lifehistorical significance: the latent period. In this note, we use a simple model that explicitly incorporates the latent period to gain some insight into the virulence evolution determinants. We discuss the model's implications as to the durability of resistance in agriculture. In particular, we show that an anti-growth-rate resistance may, contrarily to the classical insight, lower intrinsic virulence. This is because latency, as an additional ldquodegree of freedomrdquo, may absorb what would otherwise result in an virulence increase towards less resistant hosts. Moreover, this goes with a greater healthy host density, regardless whether the crop is resistant or not, thanks to maladaptation.