Integrating cold hardiness and deacclimation resistance demonstrates a conserved response to chilling accumulation in grapevines

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To survive the harsh conditions of winter, woody perennial species such as grapevine have adapted to use environmental cues to trigger physiological changes to induce dormancy, acquire cold hardiness, and measure the length of winter to properly time spring budbreak. Human-induced climate change disrupts these cues by prolonging warm temperatures in autumn, reducing the depth and consistency of midwinter, and triggering early budbreak through false spring events. We evaluated variation in dormant bud cold hardiness and chilling hour requirements of 31 different grapevine varieties over 3 years. Differential thermal analysis was used to track changes in cold hardiness, and deacclimation resistance was assessed throughout the season to track dormancy progression. Results demonstrate wide variation in the maximum deacclimation rate (1.03-2.87 °C d-1) among varieties under forcing conditions. Significant correlations were noted of wild species distributions or cultivar provenance with cold hardiness and deacclimation rates, demonstrating the likely climate-adaptive nature of these traits. When integrated with variation in cold hardiness, these rates revealed a relationship between winter cold hardiness, changes in deacclimation rate, and budbreak phenology. Standardizing rates among varieties as deacclimation potential demonstrated a conserved response to chilling exposure among varieties that alters our interpretation of the concept of high and low chill varieties and chilling requirement in grapevine.