Anthocyanin levels and expression analysis of biosynthesis-related genes during ripening of Sicilian and international grape berries subjected to leaf removal and water deficit

The imposition of managed water deficit and early leaf removal are strategies used to improve the grapes quality in terms of anthocyanin content. The aim of our work was to evaluate the change in total anthocyanin levels during the ripening of the Sicilian grapes (Nero d'Avola and Frappato) and of the international variety of Cabernet Sauvignon, subjected to two different levels of water deficit, 0% (NI) and 30% (I) of estimated crop evapotranspiration, and subjected to Early Leaf Removal (ELR) or Not (NLR). The expression of genes involved in anthocyanin biosynthesis, such as Phenylalanine Ammonia Lyase (PAL) and UDP-glucose-Flavonoid-Glucosyl Transferase (UFGT), was also monitored. Our results indicate that the amount of anthocyanin during the ripening process can be regulated by the application of the aforementioned agronomic practises. The anthocyanin content of Cabernet Sauvignon may be risen either by the simultaneous application of Early Leaf Removal and in water restitution regime (ELR-I) or by the association of water deficit and absence of defoliation (NLR-NI). The analysis of the total content of anthocyanin in Frappato variety has globally revealed that the maximum value in the levels of pigments is reached later than in the other autochthonous Nero d'Avola variety. This finding is of considerable interest since both the harvest time and product processing might be differentiated among varieties. Conversely, the variety Nero d'Avola was not affected by the experimental conditions and showed the highest level of pigments at fully ripe time.