This research was performed with the aim of studying the influence of cluster thinning at véraison (CT) and pre-flowering leaf removal (PFLR) on some maturation and quality parameters of grape Refošk.
Polyphenol content was related to the pattern of a flavonoid transporter present in the skin. This protein cross-reacted with an antibody raised against a sequence of the mammalian bilitranslocase, an enzyme involved in dietary polyphenol assumption.
This antibody was used in ELISA test to probe the presence of the transporter in ripening Refošk grape berry. The bilitranslocase-like translocator expression was increased at the véraison and the onset of maturation by CT treatment, when compared to untreated grapevines, while PFLR showed the opposite trend. Nevertheless, at harvest, untreated samples showed an increment of protein concentration, which was significantly higher than in the other treatments.
These results seem not strictly related with the total anthocyan content in grape berry, since total pigments increased more in CT and PFRL rather than in control samples, due to a favourable shift in photosynthetic area and reproductive organ balance induced by these agronomic practices. Similarly, also the phenolic potential, specifically evaluated at the harvest stage, showed a positive increase of all the parameters examined in the PFLR samples and of some of them in the CT ones. In conclusion, although the viticultural practices able to increase source/sink ratio in the cluster lead to a reduced expression of bilitranslocase-like translocator, its level and the one of other transporter proteins would be adequate enough to accomplish secondary metabolite translocation.
