Different approaches of combating bacterial canker in tomato: in pursuit of resistance

The quarantine pathogen, Clavibacter michiganensis subsp. michiganensis (Cmm), is one of the most important bacterial pathogens affecting tomatoes. The quarantine status and the devastating disease symptoms caused by Cmm are problematic for many parties. Even though resistance/tolerance breeding is one of the most important and successful ways to manage diseases, other paths can also be walked to manage disease symptoms. We developed a new and an efficient way to screen big tomato populations in vitro and used it to fine map the QTL on chromosome 7. The region has been reduced to 211 Kb which resulted in 15 annotated genes. Furthermore, several susceptibility (S) genes were used to test effectiveness against Cmm and we found WAT1 confers higher tolerance. Lastly, alternative approaches were applied to reduce Cmm disease symptoms by applying grafting and utilizing biocontrol agents, respectively. From this method, we found reduced wilting symptoms only when the pathogen enters from the roots. In conclusion, we developed a new protocol that could ease disease screening, fine mapped the QTL on chromosome 7 to a smaller region, found a potential new tolerance against Cmm by manipulating the WAT1 gene and tested two alternative approaches to minimize wilting symptom.