Deacclimation Rate in Cultivated and Wild Grapes is Dependent on Dormancy Stage and Temperature

Grapevine buds must survive the winter in order to burst and produce shoots and flowers during the following spring. During the winter, buds are acclimated and can survive temperatures below -30 °C due to supercooling. In the spring, accumulation of growing degree-days leads to deacclimation of these tissues, however the rates of deacclimation can vary depending on the dormancy stage of the buds. The objective of this study was to determine the rate of deacclimation of four different grapevines exposed to different temperatures at endodormant and ecodormant stages: Vitis vinifera ‘Cabernet Sauvignon’, V. vinifera ‘Riesling’, V. amurensis, and V. riparia. All plant material was collected from vineyards located in Geneva, NY. Endodormant material was collected on 11 Nov. 2014, and rate of deacclimation was evaluated at continuous 4 °C or 22 °C regimen for 7 days. Ecodormant material was collected on 10 Mar. 2015, and was evaluated for 10 days at the same temperatures as endodormant, and also with daily changes between 4 °C and 22 °C (4/22 °C). Buds were sampled daily and subjected to differential thermal analysis to evaluate the temperature to which buds were able to supercool. For endodormant buds, there was no deacclimation observed in the period observed. All grapevines maintained their supercooling ability unchanged over the course of 7 days regardless of the temperature of storage (‘Cabernet Sauvignon’: –18.7  °C ±0.4 °C; ‘Riesling’: –21.1 °C ±0.5 °C; V. amurensis: –21.7 °C ±0.5 °C; and V. riparia: –24.0  °C ±0.5 °C). For ecodormant buds however, the rate of deacclimation was dependent on the interaction between temperature of storage and grapevine. At 4 °C, ‘Cabernet Sauvignon’, ‘Riesling’ and V. riparia had similar deacclimation rate (~0.32 °C/day), while V. amurensis had a much higher rate (1.03 °C/day). At 4/22 °C, ‘Cabernet Sauvignon’ and ‘Riesling’ had an average deacclimation rate of 0.86 °C/day, while V. amurensis and V. riparia averaged 1.40 °C/day. At 22 °C, there were no differences between the grapevines tested (~1.43 °C/day). All grapevines had higher rate of deacclimation at 4/22 °C compared to 4 °C, but only ‘Cabernet Sauvignon’ and ‘Riesling’ had a higher deacclimation rate in the 22 °C treatment compared to 4/22 °C. All species had a similar pattern in deacclimation rates, with deacclimation rates being positively correlated to exposed temperatures. V. amurensis had the highest deacclimation rate at 4 °C, which may indicate that this species has a lower base temperature.