Foliar Application of a Tagatose-Based Product Reduces Downy Mildew Symptoms through Induction of Grapevine Resistance and Anti-Oomycete Action

Downy mildew caused by the oomycete Plasmopara viticola represents one of most devastating diseases in vineyards. Current ways to control this disease rely mainly on fungicide applications, but agro-ecological concerns have raised interest sustainable alternative methods. Certain rare sugars, like D-tagatose, shown efficacy reducing various plant diseases, including grapevine downy mildew. However, mechanism action D-tagatose against is not understood. The aim study was characterize and a D-tagatose-based formulated product (IFP48) compare it with correspondent active molecule, pure (TAG). Whereas IFP48 root treatment provided scarce protection, leaf efficient, especially at dosage 5 g/L. In particular, directly inhibited P. sporangia germination, upregulated expression defense-related genes, increased content stilbene phytoalexins. Conversely, genes phytoalexins were only slightly affected TAG, suggesting that formulation possibly improved effects grapevine.