Quel lien entre l’épidémiologie, la création variétale et le potentiel de durabilité des résistances ? Illustration chez le phoma du colza.

How epidemics reduce crop yield is influenced by plants, pathogens, environment, time and human actions. Genetic resistance undeniably is one tactic contributing to crop protection, using qualitative and/or quantitative resistances. Because it acts on the epidemiology, plant breeding can contribute to the goal of increasing the potential durability of resistance. The adaptation of pathogen populations causing the loss of efficacy of resistance does not depend solely on the epidemic dynamics on one field in one season, butrather on pluriannual dynamics including transmission of inoculum between seasons. Understand the epidemiology including the transmission of the fungus between years and between plots can allow using breeding potential more thoroughly and to building crop protection strategies based on the complementarity with cropping practices or the deployment of varieties. The practical implementation of strategies depends on the ability to accurately measure the expression of resistance in varieties, that relies on the development of corresponding methodologies. We will illustrate these points in the case of Phoma stem canker of oilseed rape