CRISPR-Cas9 mediated mutagenesis of a DMR6 ortholog in tomato confers broad-spectrum disease resistance

Abstract

Pathogenic microbes are responsible for severe production losses in crops worldwide. The use of disease resistant crop varieties can be a sustainable approach to meet the food demand of the worlds growing population. However, classical plant breeding is usually laborious and time-consuming, thus hampering efficient improvement of many crops. With the advent of genome editing technologies, in particular the CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats-Cas9) system, we are now able to introduce improved crop traits in a rapid and efficient manner. In this work, we genome edited durable disease resistance in tomato by modifying a specific gene associated with disease resistance. Recently, it was 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 up-regulated during pathogen infection, and mutations in the dmr6 gene results in increased salicylic acid levels. The tomato SlDMR6-1 orthologue Solyc03g080190 is also up-regulated 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 frameshift 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.