2018 ASHS Annual Conference

Canopy management and fruit load control aim to keep a balance between vine’s sources and sinks. In fact, balanced vines may produce more consistent yields and have a more even ripening. This study aims to study the relationship between source–sink ratios and important parameters for production logistics and grape quality, such as progress of ripening and grape composition at harvest. After homogenizing all vines by removing laterals and adjusting the number of shoots to 20, we tested three levels of canopy density and fruit load combined in a factorial design (3 by 3). This is, 3 canopy levels, 100%, 66% and 33% of the leaves combined with 3 fruit loads, 100%, 66% and 33% of the fruit corresponding to 30, 20 and 10 clusters per vine, respectively. Onset of ripening was sequentially delayed in 66% and 33% canopy treatments. The progress of ripening, accumulation of soluble solids and loss of acidity (increase in pH and decrease in total acidity), also occurred slower in 66% and 33% canopy treatments compared to 100% of the canopy. In fact, the time to reach commercial maturity (>25°Brix) was delayed 6 weeks for the 33% canopy level. Surprisingly, fruit load did not have a significant effect on the progress of ripening. When comparing all treatments at commercial maturity, the treatment maintaining 100% of the canopy had the highest total acidity and lowest pH. Berry flavonoids at harvest were similar in the case of anthocyanins and flavonols. Contrarily, proanthocyanidins in both skins and seeds were lower in treatments keeping 33% of the canopy and 33% of the fruit. These results provide the basis for the control of the speed of ripening, and the understanding of flavonoid profile development in the different yielding strategies in wine grape production.