Seasonal Variation in Freezing Tolerance and Dehydrin Protein Expression in Canes of Frontenac and Seyval Blanc Grapevine Cultivars

The cold hardiness of primary buds of grapevine cultivars (Vitis sp.) is typically used as a principal indicator of grapevine cold hardiness; however, freezing tolerance of cane tissues has received little attention. Our investigation characterized freezing tolerance and protein profiles (including dehydrins) of grapevine cultivars that are very hardy (Frontenac) and moderately hardy (Seyval blanc) during the autumnal cold acclimation, midwinter, and vernal deacclimation period (20 Aug to 22 Apr) in a research vineyard. Cane samples collected in the field (a total of 15 sampling dates with ~2 samples/month) were subjected to controlled laboratory freezing tests to assess the freezing tolerance of bark + vascular cambium and xylem + pith tissues. SDS-PAGE profiles and immunoblots were used to determine qualitative and quantitative changes in proteins, including dehydrins. During early autumn (20 Aug to 28 Oct), an increase in bark + vascular cambium and xylem + pith freezing tolerance of the two cultivars was similar (by about 12 °C relative to the starting date). ‘Frontenac’ bark + vascular cambium appears more responsive to colder/freezing temperatures for cold acclimation during mid-winter (28 Oct to 5 Jan) than ‘Seyval blanc’, and at the peak hardiness, it was about 15 °C more freeze tolerant. For xylem + pith tissues of both cultivars, the kinetics of cold acclimation and differences in cultivars’ peak freezing tolerance were similar to those for bark + vascular cambium tissues. The bark + vascular cambium and xylem + pith of both cultivars deacclimated between 15 Jan and 23 Mar, with ‘Seyval blanc’ losing ~3 to 6 °C more in hardiness than ‘Frontenac’. Both cultivars exhibited reacclimation following deacclimation in response to freeze events of late March to early April, whereby ‘Seyval blanc’ showed a greater reacclimation capacity. Polypeptides in bark + vascular cambium and xylem + pith of ‘Seyval blanc’ (23kDa and 17 kDa) and ‘Frontenac’ (23 kDa, 19kDa, and 17 kDa) accumulated during cold acclimation, followed by reduced abundance with deacclimation. A ~13 kDa dehydrin protein in the bark + vascular cambium of both cultivars exhibited a similar accumulation pattern and was not detected in xylem + pith tissues.