Consideration of dynamical plant-pathogen interactions for animproved management of powdery mildew epidemics in grapevine

Abstract: The current control of grape powdery mildew requires news strategies, able to limit thepathogen development and requesting a reduced number of chemical sprayings. This studyproposes to exploit host plasticity in order to investigate the effect of a plant growth changing oneither the epidemic process, or organs susceptibility. An experimental plot combining twocultivars, three rootstocks and two opposite crop management for creating a vigour differentialwas surveyed regularly during the vegetative growth and different variables were measured tocharacterise host growth and pathogen. Shoots coming from vinestocks localized in the differentvigour area were sampled for organ susceptibility assessment. Two groups of vigour wereobtained, not based on the established treatment but on the individual growth potential, that differmainly by the number of secondary leaves. The vigorous group presents the higher level ofdisease, increasing with the appearance of secondary leaves. A low vigour modifies thesusceptibility of the tissues, by an earlier appearance of ontogenic resistance phenomenon. Therelevance of vigour control and the concomitant physiologist mechanisms are discussed asintegrative strategy in the grape powdery mildew management.