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Water deficit severity during berry development alters timing of dormancy transitions in wine grape cultivar Malbec

Shellie, Krista, Kovaleski, Alisson P., Londo, Jason P.
Scientia horticulturae 2018 v.232 pp. 226-230
Vitis, budbreak, buds, canes, climate change, cold treatment, cultivars, deficit irrigation, dormancy, drought, growing season, harvesting, vines, water stress, wine grapes
The objective of this study was to test the hypothesis that vine water stress during the growing season can lengthen the dormancy cycle by inducing earlier transition into endodormancy. A bud forcing assay was used to compare the dormancy transitions of field-grown ‘Malbec’ grapevines that had been deficit-irrigated for seven consecutive growing seasons to supply 35 or 70% of estimated water demand to that of fully-watered vines. Canes were field-sampled from deficit-irrigated and fully-watered plots at multiple time points over a span of 100 days, beginning 30 days prior to harvest. Buds at nodes two through eight were cut into single-node segments, held under bud-forcing conditions for 60 days, and evaluated daily for the occurrence of bud break. Contrary to our initial hypothesis, water stress shortened the dormancy cycle by delaying the onset of endodormancy, decreasing the amount of chilling required for release from endodormancy and increasing the readiness to resume growth during ecodormancy. Results support the idea that drought stress-induced regulatory networks ‘cross-talk’ with environmental and hormonal regulatory signals that modulate the activity-dormancy cycle. Understanding the underlying mechanisms by which drought stress alters the activity-dormancy cycle may be critical for sustaining vine productivity in a changing climate.