Managing disease resistance at the level of cultivated areas

In plant epidemiology, the idea of developing management strategies for resistant varieties at the landscape scale is being explored with increasing frequency. Following a review of the literature, we demonstrate, based on an analysis of datasets collected across France, that the resistance of cultivated varieties, as observed in the field, is influenced by the varietal composition of the landscape as a whole. Furthermore, we show that taking into account the quantitative aspects of the host–parasite relationship is essential to explain the evolution of the pathogen population at this scale. To take this exploration further, we have developed a set of models and investigated the effect of landscape characteristics on pathogen population dynamics. We have shown that landscape fragmentation can lead to an overall reduction in epidemics but also, under certain conditions, to an increase in disease severity in varieties with quantitative resistance. Finally, landscape structure has a strong effect on the evolution of the pathogen population towards specialist or generalist forms.