Interaction of Botrytis cinerea with the intermediate C3-CAM plant Mesembryanthemum crystallinum

The interaction between necrotrophic Botrytis cinerea and Mesembryanthemum crystallinum, a C3/CAM intermediate plant, was followed macroscopically, microscopically, by analyzing CAM (Crassulacean Acid Metabolism) related and H2O2 accumulation in leaf tissue. In response to infection, M. crystallinum in both C3 and CAM states exhibited hypersensitive response (HR)-like defence response or soft-rot spreading lesions depending on the post-inoculation environmental conditions. Our results point out to the fact that light is required for plant resistance, and HR-like necrotic lesions are co-localized with thermal effects visible on the infrared images possibly related to water disturbances, stomatal closure and H2O2 accumulation. In C3 plants, these changes were followed by metabolic shifts towards weak diurnal oscillations of malate content. We suppose that light-dependent processes related to CAM and H2O2 accumulation are in parallel with resistance to B. cinerea. This may explain at least partly why CAM plants could be less sensitive to biotic stress factors.