Bud dormancy and cold hardiness are critical adaptations for surviving winter cold stress for temperate perennial plant species. In grapevine, acquisition of cold hardiness requires dormancy induction in the early winter and careful maintenance of dormancy state throughout winter. With sufficient exposure to low, non-freezing temperatures (chilling requirement), grapevine buds transition between early (endodormant) and late winter (ecodormant) states. The objective of this study was to uncover the relationship between fulfilment of the chilling requirement and the effects of various temperatures on loss of cold hardiness (deacclimation). The relationship between chilling requirement and temperature as it affects the rate of deacclimation ( k deacc ) was examined for dormant cuttings of Vitis vinifera , V. aestivalis , V. amurensis and V. riparia . The effect of temperature on k deacc was exponential at low and logarithmic at high temperatures. Deacclimation rates also increased in magnitude as chilling accumulated demonstrating a change in deacclimation potential (Ψ deacc ), following a logarithmic response. The combination of Ψ deacc and k deacc indicates genotype-specific thermal efficiency for deacclimation and growth in Vitis that may be overlooked by simple growing degree-day computations. The Ψ deacc and k deacc parameters are genotype-specific and will greatly increase the refinement of models predicting effects of climate change on phenology. Deacclimation rates represent a quantitative determinant of dormancy transition and budbreak in grapevine and will assist researchers in selecting germplasm for differences in chilling requirement and thermal efficiency.
Low-temperature stresses limit the sustainability and productivity of grapevines when early spring frosts damage young grapevine leaves. Spring conditions often expose grapevines to low, but not damaging, chilling temperatures and these temperatures have been shown to increase freeze resistance in other model systems. In this study, we examined whole-transcriptome gene expression patterns of young leaf tissue from cuttings of five different grapevine cultivars, exposed to chill and freeze shock, in order to understand the underlying transcriptional landscape associated with cold stress response. No visible damage was observed when grapevine leaves were exposed to chilling temperatures while freeze temperatures resulted in variable damage in all cultivars. Significant differences in gene expression were observed between warm control conditions and all types of cold stress. Exposure to chill stress (4 °C) versus freezing stress (−3 °C) resulted in very different patterns of gene expression and enriched pathway responses. Genes from the ethylene signaling, ABA signaling, the AP2/ERF, WRKY, and NAC transcription factor families, and starch/sucrose/galactose pathways were among the most commonly observed to be differentially regulated. Preconditioning leaves to chill temperatures prior to freezing temperatures resulted in slight buffering of gene expression responses, suggesting that differences between chill and freeze shock perception complicates identification of candidate genes for cold resistance in grapevine. Overall, the transcriptional landscape contrasts observed between low temperature and freezing stresses demonstrate very different activation of candidate pathways impacting grapevine cold response.
-The objective of this work was to assess the effect of six rootstocks on yield, fruit quality, and growth of 'Oneco' mandarin during the first seven harvesting seasons, in Butiá, Rio Grande do Sul State, Brazil. The rootstocks evaluated were: 'Swingle' citrumelo (Citrus paradisi × Poncirus trifoliata
Background and Aims Grapevine production in cool climates is limited by aspects of winter survival and frost risk. Cold hardiness‐related traits are key to future viticultural sustainability as climate variations, including acute cold events and frost, are predicted to increase even in traditional cultivation regions. This study examines the variation in dormant bud cold hardiness (supercooling) and dormancy (chilling requirement) in 43 different genotypes of the wild grapevine species Vitis riparia, the dominant wild species used to incorporate cold hardiness traits into new hybrid grapevine cultivars. Methods and Results Cold hardiness was evaluated bi‐weekly in 2 years using measures of low temperature exotherms. Whole winter responses were modelled to determine significant factors affecting cold hardiness and determine genotypic differences. Results demonstrate significant differences in supercooling ability and deacclimation rate (loss of cold hardiness) between genotypes. Conclusions This study determined that genotypic differences contribute to initial differences in cold hardiness. However, data modelling suggests that midwinter cold hardiness changes are driven by environment as all Vitis riparia tested in this study respond to temperature in the same manner during the endodormant period of winter. In contrast, responses to warming temperature during ecodormancy are significantly different by genotype. Significance of the Study This study has demonstrated that these two traits interact to determine differences in early versus late winter cold hardiness and help identify breeding germplasm with delayed loss of cold hardiness.
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