Application of proximal and remote sensing on precision viticulture in Sardinia (Italy) – Preliminary results

The anthocyanin content of colored grapes is a useful tool when making decisions in viticulture. The optical portable sensor Multiplex3® (FORCE-A, Paris, France) is a rapid and non-destructive method for screening the colored component of grapes. It is based on the transmission of fruit chlorophyll fluorescence, based on the anthocyanin content of the intact berry skin. As a result it creates some indices to describe this phenomenon. These are ANTH_RG (Anthocyanin excitation in Red-Green fluorescence) and FERARI (Fluorescence Excitation Ratio Anthocyanin Relative Index). The aim of this study is to use wet chemistry analysis to calibrate FERARI and ANTH_RG indices in relation to total anthocyanin content (mg/100g skin). The trial was carried out in two Cagnulari vineyards in Northern Sardinia (Alghero, Sennori). The ANTH_RG and FERARI indices were monitored in the field on bunches of grapes during the 2015 season, from veraison to harvest. The FERARI index showed that there was a good correlation with the anthocyanin concentration derived from spectrophotometric analysis in both samples (Alghero ρ=0.69, Sennori ρ=0.66). The equation obtained for this index is a logarithmic curve. The ANTH_RG index showed a weak inverse correlation with the anthocyanins measured (Alghero ρ=-0.24, Sennori ρ=-0.23). An exponential curve gave the best possible fit. In conclusion, in this first part of the research, we found that the FERARI index may help in making decisions in precision viticulture. Further studies are being carried out to confirm these preliminary results.