Foliar Application of a Tagatose-Based Product Reduces Downy Mildew Symptoms through Induction of Grapevine Resistance and Anti-Oomycete Action
2022
Nikola Mijailovic | Andrea Nesler | Michele Perazzolli | Aziz Aziz | Ait Barka Essaïd
Downy mildew caused by the oomycete <i>Plasmopara viticola</i> represents one of the most devastating diseases in vineyards. Current ways to control this disease rely mainly on fungicide applications, but agro-ecological concerns have raised interest in sustainable alternative methods. Certain rare sugars, like D-tagatose, have shown efficacy in reducing various plant diseases, including grapevine downy mildew. However, the mechanism of action of D-tagatose against grapevine downy mildew is not understood. The aim of this study was to characterize the efficacy and mechanism of action of a D-tagatose-based formulated product (IFP48) against grapevine downy mildew and compare it with the correspondent active molecule, pure D-tagatose (TAG). Whereas IFP48 root treatment provided scarce protection, the leaf treatment was the most efficient, especially at the dosage of 5 g/L. In particular, IFP48 treatment directly inhibited <i>P. viticola</i> sporangia germination, upregulated the expression of defense-related genes, and increased the content of stilbene phytoalexins. Conversely, the expression of defense-related genes and the content of stilbene phytoalexins were only slightly affected by TAG, suggesting that the formulation possibly improved D-tagatose effects against downy mildew in grapevine.
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