Optically-assessed preformed flavonoids and susceptibility of grapevine to Plasmopara viticola under different light regimes

A non-destructive tool for rapidly predicting grapevine susceptibility to Plasmopara viticola, the pathogen responsible for downy mildew, is urgently required. These authors use a new spectroscopic tool, the chlorophyll fluorescence-based portable leaf-clip Dualex, for the non-invasive determination of flavonoids in grapevine leaves under two different light regimes, and the evaluation of the relationship between the constitutive flavonoids and the resistance of grapevine to the infection by downy mildew. The results indicate an inverse relationship between preformed flavonoids and the susceptibility of grapevines to infection.