Recently, scientists demonstrated that inactivation of a single gene called DMR6 (downy mildew resistance 6) confers resistance to several pathogens in Arabidopsis thaliana. This gene is specifically upregulated during pathogen infection, and mutations in the dmr6 gene results in increased salicylic acid (SA) levels. The tomato SlDMR6-1 orthologue Solyc03g080190.2 is also upregulated during infection by Pseudomonas syringae pv. tomato and Phytophthora capsici. Using the CRISPR-Cas9 system, we generated tomato plants with small deletions in the SlDMR6-1 gene that result in frame shift and premature truncation of the protein. Remarkably, these mutants do not have significant detrimental effects in terms of growth and development under greenhouse conditions and show disease resistance against different pathogens, including P. syringae, P. capsici and Xanthomonas spp. Preliminary data indicate that SA levels are increased in the Sldmr6-1 mutants in comparison to the wild type tomato plants, suggesting that resistance correlates with increased SA levels. We are working on understanding and characterizing the mechanism underlying DMR6-mediated disease resistance in tomato.