Cold hardiness, deacclimation, and budbreak phenology in grapevine

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 fall, 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
maximum deacclimation rate (1.03 – 2.87 °C/day) among varieties under
forcing conditions. Absolute maximum rates of deacclimation show
signatures of species-level responses to forcing temperatures. 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.