Breeding for grapevine downy mildew resistance : a review of ‘‘omics’’ approache

Downy mildew (DM) is one of the most destructive diseases affecting viticulture, especially in temperate-humid climates. This pathogen is able to differentially attack leaves and grapes, and is currently controlled with repeated applications of fungicides that lead to environmental pollution, development of resistant strains, residual toxicity, and pathogen pressure. The use of resistant grapevine varieties, obtained through breeding programs, represents a potential alternative to control grapevine DM, although this approach is constrained by the limits of natural resistance. In this review, we describe the latest breakthroughs achieved in the exploitation of the host-pathogen interaction, which have led to the identification of DM resistance loci, with associated molecular markers, that can be employed to efficiently screen hybrid grapevines and improve (pre-) breeding programs. The development of controlled infection protocols and contemporary "omics'' approaches (next generation sequencing/genomics, QTLomics, transcriptomics, proteomics and metabolomics) integrated with comparative studies are shedding light onto the early host responses to DM attack and the complex plant defence mechanisms that are triggered