Molecular breeding for resistance against powdery mildew in tomato: an overview

Powdery mildew is a group of plant diseases caused by fungi of the Erysiphaceae family and threatening virtually all important crop plants. The main causative agents of powdery mildew in tomato are the fungi Leveilula taurica and Erysiphe neolycopersici . The genetic basis of tomato resistance to powdery mildew includes a series of six Ol- loci conferring resistance to E. neolycopersici and a single Lv locus of resistance to L. taurica. S-genes such as SlMlo1, SlPMR4, and SlDMR1 confer resistance against multiple powdery mildew species and thus are considered more promising targets for molecular breeding using methods of genome editing by CRISPR/Cas system. Specific resistance to powdery mildew is realized through specific leucine-rich repeat (LRR) proteins, as a general mechanism of pathogen-specific plant immunity. The present review focuses on the current advances in the tomato breeding for resistance to powdery mildew, based on the known molecular mechanisms of susceptibility and resistance.