2017 ASHS Annual Conference

Grapevines (Vitis spp.), much like other temperate and subtropical plants, set overwintering buds during the late summer and fall. These buds must survive winter temperatures in order to produce a crop in the following year. The level of cold hardiness of the buds varies throughout the winter, largely due to air temperature. The objective of this study was to determine the level of response to temperatures during both acclimation and deacclimation phases. The genotypes used were V. vinifera ‘Cabernet Franc’, ‘Cabernet Sauvignon’, ‘Riesling’, ‘Sauvignon blanc’, and two wild grapevine species, V. riparia PI588711, and V. aestivalis PI483143. Buds were collected from the field and prepared as single node cuttings. For acclimation responses, buds were collected in late October, and placed in growth chambers at constant 2, 7, and 11 °C. After four weeks, subsets from the 3 temperatures were moved into a chamber with a temperature cycle ranging from 1.5 °C – 12.5 °C, resulting in an average age temperature of 7 °C (7 °C Cycle). For deacclimation responses, buds were collected in late February, and placed in chambers at constant 2, 7, 11 °C, and in 7 °C Cycle. Samples were collected at regular intervals to determine the effect of temperature on cold hardiness using differential thermal analysis (DTA) to measure low temperature exotherms. Multiple linear regression was used to evaluate the effects of temperature and temperature cycle on acclimation and deacclimation rates. Results demonstrate that constant temperature treatments did not lead to further acclimation, thus field levels of cold hardiness were not enhanced. However, buds that were exposed to the 7 °C Cycle were seen to increase cold hardiness significantly, regardless of genotype and temperature from where they were moved. For deacclimation, loss of cold hardiness was related to temperature, and higher temperatures resulted in a faster deacclimation. V. riparia had the highest deacclimation rate, and there was no differences between the other genotypes. In contrast to acclimation response, temperature cycling did not differ from constant temperature exposure in the deacclimation. Therefore, the deacclimation response to temperature may be simply an effect of temperature on enzyme reaction rates, not requiring temperature sensing by the plant. However, the acclimation process appears sensitive to a more sophisticated mechanism in which the perception of temperature variation is necessary.