The aim of this study was to determine if vine regrowth can be used as a strategy to significantly delay ripening by close to two months.
The experiment was done in Spain on Tempranillo grapes grafted onto R110, for one season (2017). Vines were seven years old and trained onto a bilateral double cordon. For the forcing treatment, green shoots were removed leaving two nodes, at the following growth stages:
- G – Flower clusters separated
- I – Bloom
- J – Veraison
Any lateral shoots, leaves and fruit on the leftover nodes were also removed. In the control treatment, conventional practices were followed. Hormonal analysis was also done.
- Compared to the control, the forcing treatments applied at stages G, I and J succeeded in delaying ripening by 18, 27 and 45 days respectively.
- The forcing treatments significantly reduced yield. The number of clusters per vine increased for treatments I and J, yet the cluster weight was significantly reduced in all treatments.
- Acidity in berries in all treatments was much higher.
- After treatments were applied, Cytokinin content increased while Abscisic acid decreased in the latent buds. This is the opposite of what happened in latent buds in the control.
It should be noted that forcing vine regrowth in this way, should be done judiciously. If ripening is delayed until too late in the season, temperatures could be too low to successfully ripen the crop. This experiment was only conducted for one year. There is no data on what the effect would be on vines if this technique is used continuously on the same vineyard.
Significance of the study:
Increasing temperature leads to earlier ripening. This means that grapes tend to reach maturity during a much warmer part of the season, which is not ideal for preserving acidity and anthocyanins. Harvest compression is another challenge to deal with as temperatures rise. Late winter pruning, minimal pruning and shoot trimming have been investigated as options to delay ripening, but these practices delay ripening by 15-20 days. This might not be long enough in future. Having another technique to delay ripening even further, gives producers more options to adapt management practices to mitigate the effects of climate change.
Pou, P. Balda, A. Albacete, F. Martínez de Toda. Forcing vine regrowth to delay ripening and its association to changes in the hormonal balance.Vitis Journal of Grapevine Research. Vol.58: Vitis Special Issue, 95-101 (2019).https://doi.org/10.5073/vitis.2019.58.special-issue.95-101