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Research Article

Cold Hardiness of Cold Climate Interspecific Hybrid Grapevines Grown in a Cold Climate Region

Michael North, Beth Ann Workmaster, Amaya Atucha
Am J Enol Vitic.  2021  72: 318-327  ; DOI: 10.5344/ajev.2021.21001

Article Figures & Data

Figures

  • Figure 1
    Figure 1

    Median low temperature exotherm (LT50) trends plotted for five cold climate interspecific hybrid grapevine cultivars, with daily maximum (red line) and minimum (blue line) temperatures for 2017 to 2018 and 2018 to 2019. Vertical dotted line identifies the date that buds tested with differential thermal analysis showed no low temperature exotherms (1 Feb 2019).

  • Figure 2
    Figure 2

    Predicted bud cold hardiness (black, dashed lines) and observed median low temperature exotherm (LT50) values (colored lines and circles) plotted for five cold climate interspecific hybrid grapevine cultivars, with daily maximum and minimum temperature ranges for 2017 to 2018 and 2018 to 2019 (gray shaded area). Predictions were generated using the Ferguson et al. (2011, 2014) model reparametrized for each cultivar.

  • Figure 3
    Figure 3

    Comparison between predicted and observed bud cold hardiness, expressed as median low temperature exotherm (LT50) for five cold climate interspecific hybrid grapevine cultivars including r2, bias (B), and sample size (n) for each cultivar and year. Predictions were generated using the Ferguson et al. (2011, 2014) model reparametrized for each cultivar. RMSE, root mean square error.

Tables

  • Table 1

    Symbols, abbreviations, and units of measurement used in explanatory and predictive models.

    Table 1
  • Table 2

    Parameter levels tested in all combinations stepwise for five cold climate interspecific hybrid grapevine cultivars to minimize root mean square error (RMSE): endodormant temperature threshold (Tth,endo), ecodormant temperature threshold (Tth,eco), endodormant acclimation rate (ka,endo), ecodormant acclimation rate (ka,eco), endodormant deacclimation rate (kd,endo), ecodormant deacclimation rate (kd,eco), theta exponent in deacclimation logistic equation (θ), and ecodormancy boundary (EDB). A total of 2,976,750 combinations were tested per cultivar and for two years (2017 to 2018 and 2018 to 2019).

    Table 2
  • Table 3

    Estimates for parameters and interactions for the explanatory linear regression model describing low temperature exotherms for five cold climate interspecific hybrid grapevine cultivars during two years using the temperature index (σT), Time (days), and Time2 (days2) as parameters. Parameters separated by a colon represent interactions between two parameters. Different letters within a column denote statistical differences between cultivars using a t-test with α = 0.05.

    Table 3
  • Table 4

    Relative contribution of parameters in the explanatory linear regression model calculated using dominance analysis. The temperature index is represented by σT. Parameters separated by a colon represent interactions between two parameters.

    Table 4
  • Table 5

    Parameter value combinations that minimize root mean square error (RMSE) after reparametrizing the predictive discrete-dynamic model to simulate bud cold hardiness for five cold climate interspecific hybrid grapevine cultivars. Cold hardiness (Hc) predictions begin at Hc, initial, which is the earliest median low temperature exotherm (LT50) observed. Predictions are bound by lower (Hc, max) and upper (Hc, min) limits. Hc, max is the lowest LT50 observed, while Hc, min is highest LT50 observed. Other parameters include endodormant temperature threshold (Tth,endo), ecodormant temperature threshold (Tth,eco), endodormant acclimation rate (ka,endo), ecodormant acclimation rate (ka,eco), endodormant deacclimation rate (kd,endo), ecodormant deacclimation rate (kd,eco), theta exponent in deacclimation logistic equation (θ), and ecodormancy boundary (EDB).

    Table 5
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Cold Hardiness of Cold Climate Interspecific Hybrid Grapevines Grown in a Cold Climate Region
Michael North, Beth Ann Workmaster, Amaya Atucha
Am J Enol Vitic.  2021  72: 318-327  ; DOI: 10.5344/ajev.2021.21001
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