Role of rain-splash in the progress of Septoria leaf blotch within a winter wheat variety mixture

International audience; The efficiency of variety mixtures for controlling foliar fungal diseases dispersed by rain-splash is assessed by quantifying physical and genetic barriers against Mycosphaerella graminicola (Septoria tritici). The mixture of a susceptible wheat variety with a partially resistant wheat variety, as well as the mixture with barley, did reduce the disease of the susceptible variety in pure stands by 14% and 56%, respectively. The progress of Septoria disease depends on the number of infectious cycles in relation to rainfall occurrence and characteristics. Two effects have been identified. First, the "umbrella" effect of totally or moderately resistant varieties occurs when raindrops were intercepted. This effect is decreasing with the increase of kinetic energy of rain. Second, the "barrier" effect corresponds to the interception of spore-carrying droplets by the partially or totally resistant plants. The comparison of experimental results with those of a preliminary model of splash-dispersal in a variety mixture shows similar trends.