The use of resistant plant cultivars is an efficient, cost-effective and environmentally-friendly method of disease control, particularly against viral pathogens. However, resistance is subject to breakdown, through the often rapid adaptation of viral populations to newly deployed resistant genotypes. As it exerts a weaker selection pressure on parasite populations, plant tolerance to parasites - the mechanisms that reduce the negative impact of infection on host fitness or yield, despite relatively elevated parasite concentrations - appears as an interesting alternative to resistance sensu stricto - mechanisms that reduce pathogen accumulation (1). However, the durability of tolerance has seldom been experimentally tested, and counter-examples exist (2). Moreover, littie is known about the genetic determinants controlling tolerance to pathogens. We have chosen the interaction between pepper and Cucumber mosaic virus (CMV) as a model to study plant tolerance to viral pathogens and evaluate the durability of tolerance.