Abstract
Heterogeneity for plant defences determines both the capacity of host populations to buffer the effect of infection and the pathogen´s fitness. However, little information is known on how host population structure for tolerance, a major plant defence, impacts the evolution of plant-pathogen interactions. By performing 10 serial passages of Turnip mosaic virus (TuMV) in Arabidopsis thaliana populations with varying proportion of tolerant genotypes simulating different structures for this trait, we analysed how host heterogeneity for this defence shapes the evolution of both virus multiplication, the effect of infection on plant fecundity and mortality, and plant tolerance and resistance. Results indicated that a higher proportion of tolerant genotypes in the host population promotes virus multiplication and reduces the effect of infection on plant mortality, but not on plant fecundity. These changes resulted in more effective plant tolerance to virus infection. Conversely, a lower proportion of tolerant genotypes reduced virus multiplication, boosting plant resistance. Our work for the first time provides evidence of the main role of host population structure for tolerance on pathogen evolution and on the subsequent feedback loops on plant defences.