A rapid and non destructive method to assess grape anthocyanins in the vineyard under different seasonal and water conditions

Background and Aims: Monitoring of anthocyanins (Anth) in winegrape (Vitis vinifera L.) is fundamental for the production of top-quality red wines. This work was aimed at testing a new fluorescence-based sensor for Anth detection in the vineyard. Significance of the Study: The present study showed a new important innovative technology for viticulture. The sensor evaluation of the large spatial and temporal heterogeneity in Anth accumulation can be useful as support parameter in the harvest date decision or for vineyard zoning of phenolic maturity. Methods and Results: Anth in grape (cv. Aleatico) bunches attached to the vine were monitored non-destructively in the field using a fluorescence-based sensor during the 2008 and 2009 seasons and under different water regimes. The ANTHRG index = log(far-red-fluorescenceR/far-red-fluorescenceG), with fluorescence signals excited with red (R) and green (G) light, was inversely correlated through an exponential function (r2 = 0.875) to the Anth concentration derived from the HPLC analysis of berry skin extracts. ANTHRG was effective in detecting the earlier ripening process in 2009 with respect to 2008 and differences in the Anth accumulation between seasons and in relation to different water regimes.Water deficit imposed in 2009 enhanced Anth concentration in berries because of a reduction in berry size but also an increase of Anth biosynthesis. This effect was observed by both destructive and ANTHRG non-destructive measurements. Conclusions: Our results show that the employed fluorescence sensor represents a reliable, rapid and non-invasive tool for monitoring and determining Anth accumulation in situ.