Could Base Temperatures be Negative for Grapes? Deacclimation of Cultivated and Wild Grapes in Controlled Environment

Grapevines (Vitis spp.) are native to temperate and subtropical climate zones, predominantly in the Northern Hemisphere. In order to survive winter temperatures, perennial plants such as grapevines developed dormancy mechanisms. Ecodormant buds are responsive to heat accumulation, leading to deacclimation, budbreak, and growth. The objective was to determine the deacclimation base temperature (T_base) and rate of different Vitis species. Four species were used: V. aestivalis, V. amurensis, V. riparia, and V. vinifera. For vinifera, four cultivars were used (‘Cabernet Franc’, ‘Cabernet Sauvignon’, ‘Riesling’, and ‘Sauvignon Blanc’), and two genotypes for riparia (588562 and 588711). Single node cuttings were collected in early March from vineyards located in Geneva, NY, and placed in growth chambers. Cuttings were exposed to five different temperatures (T_storage): 2, 4, 8, 10, and 22 °C. Using an arbitrary T_base of 0 °C, samples were collected in ~20 growing degree-days (GDDs) intervals for differential thermal analysis (DTA), using low temperature exotherms as a measurement of deacclimation. Multiple linear regression was used to determine the actual T_base for deacclimation of each genotype based on DTA data. GDDs were then calculated for each collection time point for all genotypes. A model was then used to calculate deacclimation rates based on GDD. ANOVA showed no differences for T_base between the genotypes of either vinifera and riparia, indicating that this characteristic might be defined by the species. The base temperature was lowest for amurensis, at −4.12 °C, followed by riparia (−1.13 °C) and aestivalis  (−0.21 °C). The highest T_base was of vinifera at 1.35 °C. The rates of deacclimation were also not affected by genotypes within species, but there was a significant interaction between species, GDD, and T_storage. V. aestivalis had the highest rate of deacclimation (0.143 °C/GDD at 10 °C), followed by amurensis and riparia (0.084 and 0.080 °C/GDD at 10 °C, respectively). V.­ vinifera had the lowest deacclimation rate: 0.044 °C/GDD at 10 °C. Although aestivalis had a higher deacclimation rate than amurensis, amurensis accumulates GDDs much faster due to its lower T_base. V. vinifera had the highest T_base and lowest deacclimation rate, resulting in a very slow deacclimation compared to the other species. Therefore, vinifera hybrids made from crosses with any of the other species tested could result in more rapid deacclimation rate, which may be detrimental if used in breeding programs for places with erratic spring weather.