Tomato Bacterial Canker Disease Management: Molecular Interactions and Role of Biocontrol Agents (BCAs) Against Clavibacter michiganensis

Tomato bacterial canker disease, caused by Clavibacter michiganensis subsp. michiganensis (Cmm) represents a burden on tomato cultivation around the world. No efficient chemical treatment and no resistant varieties are available. In recent years, the study of soil bacteria, particularly plant growth promoting rhizobacteria (PGPR), antagonistic toward phytopathogens has made great progress. The most studied bacteria belong to Pseudomonas and Bacillus, which are used as biocontrol agents (BCAs) against several plant diseases. Researches on screening for antagonistic bacteria went from isolating in vitro effective antagonists to application under greenhouses and field conditions. However, few are effective under greenhouse against Cmm. Thus, only little headway has so far been made to develop formulated BCAs. Most studies have focused on direct interactions displayed by BCAs through inhibition of Cmm growth and development, while relatively little attention has been paid to indirect interactions including those inducing reinforcement of tomato resistance to subsequent attack by the pathogen. It is also not clear which mechanisms take the lead in combatting this pathogen in soil. Therefore, in this chapter, we focused on the following questions: how C. michiganensis infect tomato plants and what are, molecular traits underlying interactions between tomato and C. michiganensis? What are the main bacterial canker disease management strategies? How to detect early the presence of Cmm in tomato seeds, plants, and soil? What are the most effective antagonistic microorganisms, especially PGPR to control tomato bacterial canker? What are the mechanisms displayed by antagonistic soil bacteria and how induction of tomato resistance could be a promising tool? Finally, our experience of work project “BIO-BIZ-01/2017,” aiming at selecting PGPR with multiple traits as effective antagonists toward C. michiganensis and inducers of tomato resistance is highlighted.