The other side of resistance: loss-of-function of susceptibility genes in tomato for resistance against Clavibacter michiganensis subsp. michiganensis

Canker of tomato (Solanum lycopersicum) caused by the bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) is a devastating plant disease occurring worldwide, and resulting in great yield losses. For this reason, the bacterium has been classified as a quarantine organism in the EU and other countries. The disease is the most important bacterial disease in tomato. However, because of the complex genetic background of resistance, no tomato cultivar containing resistance genes (R genes) against Cmm is available on the market.

A new, innovative breeding strategy based on the loss-of-function of susceptibility genes (S genes) is opening up new alternatives for resistance breeding. An S gene is a plant gene that facilitates a compatible plant-pathogen interaction, e.g. a host protein targeted by pathogen effectors. Impairing an S gene may lead to durable and broad spectrum resistance. However, impairment of such a gene could potentially lead to adverse pleiotropic effects.

The objectives of this proposed research are (1) to identify and functionally characterize novel S genes involved in the tomato-Cmm interaction, and to study the effect of their impairment on resistance against Cmm; and (2) to identify novel Cmm effectors (and their host targets).

The final goal of this project is to use impaired S genes to achieve durable and broad spectrum resistance to Cmm in tomato as well as other crops since the characterization of novel S genes in tomato can lead to the exploration of orthologs in other major crops.