Current knowledge on plant/canopy architectural traits that reduce the expression and development of epidemics

To reduce the use of pesticides, innovative studies have been developed to introduce the plant as the centre of the crop protectionsystem. The aim of this paper is to explain how architectural traits of plants and canopies induce a more or less severe epidemic and how they may be modified in order to reduce disease development. In particular, it focuses on three key questions: i) which processes linked to epidemics can be influenced by architecture ii) how can architecture be characterized relative to these modes of action, and iii) how can these effects be explored and exploited? The roles of plant/canopy architecture on inoculum interception, on epidemic development via the microclimateand on tissue receptivity are discussed. In addition, the concepts of disease avoidance, canopy porosity and an ideotypeunfavourable for disease development are described. This paper shows that many advances have already been made, but progress is still required in four main fields: microclimatology, mathematical modelling of plants, molecular genetics and ideotypeconception.