Induction of systemic defense responses in tomato against Clavibacter michiganensis by application of aerated compost tea

Clavibacter michiganensis is one of the most destructive diseases of tomato (Solanum lycopersicum L.). Studies on the chemical control of C. michiganensis offer variable results. In contrast, aerated compost teas (ACT) are sustainable alternatives for the biological control of plant diseases. We studied the metabolomic changes of the tomato-Clavibacter interaction using apoplastic washing fluids (AWF) and foliar samples of tomato plants with and without application of ACT. The application of ACT yielded a reduction in symptomatology by Clavibacter infection in tomato. Our research determined substantial tomato metabolomic differences between experimental treatments, which suggested the role of different mechanisms in susceptibility and tolerance to C. michiganensis. Notably the pool of apoplastic metabolites derived from the ACT-treated Clavibacter-infected tomato plants likely affected the fitness of C. michiganensis. Therefore, application of ACT on tomatoes could lead to dynamic and multilayered plant responses that result in a reduction in virulence of C. michiganensis in planta. Thus, the results suggest the suitability of biological control of Clavibacter based on ACT application that could lead to a reduction in the intensive use of agrochemicals and reduce environmental contamination.