Location: Horticultural Crops ResearchTitle: Water deficit severity during berry development alters timing of dormancy transitions in wine grape cultivar Malbec Author
Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/26/2017
Publication Date: 1/7/2018
Citation: Shellie, K., Kovaleski, A., Londo, J.P. 2018. Water deficit severity during berry development alters timing of dormancy transitions in wine grape cultivar Malbec. Scientia Horticulturae. 232:226-230. https://doi.org/10.1016/j.scienta.2018.01.014.
DOI: https://doi.org/10.1016/j.scienta.2018.01.014 Interpretive Summary: Wine grapes are widely grown in arid regions with winter temperatures that are unfavorable for growth. To avoid injury, the vines undergo an annual cycle of growth and dormancy that is synchronized with seasonal changes in the environment. During active growth, the vines are often exposed to drought from either a lack of precipitation or from irrigation amounts that supply only a percentage of vine water demand. Vine response to drought has been shown to alter the sensitivity to environmental signals that coordinate the cycling between growth and dormancy. The objective of this study was to test the hypothesis that vine water stress during the growing season lengthens the dormancy cycle by inducing an earlier transition into dormancy. The dormancy transitions of field-grown ‘Malbec’ grapevines that had been deficit-irrigated at differing severities for seven consecutive years was compared to that of well-watered vines. Contrary to our initial hypothesis, water stress shortened the dormancy cycle by delaying the onset of dormancy and increasing the readiness to resume growth. This could render the vines more vulnerable to injury from variable winter temperatures or extreme winter temperature events. Since the incidence of drought is likely to increase with increasing average annual temperatures, a better understanding of the underlying mechanisms by which drought stress alters the activity-dormancy cycle could become critical for sustaining vine productivity under changing climatic conditions.
Technical Abstract: 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 to supply 35 or 70% of estimated water demand (ETc) for seven consecutive growing seasons to that of well-watered vines. Canes were field-sampled from deficit-irrigated and well-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.