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

Abstract

Dormancy is a survival strategy for withstanding exposure to adverse environmental conditions. Grapevines (Vitis vinifera L.) are often exposed to water deficits during the growing season and freezing temperatures during winter, yet the influence of water stress on dormancy has received little research attention.  In this study, we monitored the onset of endodormancy, transition to ecodormancy and acquisition of cold hardiness in field-grown, Malbec grapevines. Replicated trial plots were irrigated weekly to supply 35, 70 or 100% of estimated vine water demand (ET_c). Canes from each irrigation amount were sampled at periodic intervals for a period of 100 days beginning 30 days prior to harvest. On each sampling date, buds at nodes two through eight were either cut into single-node segments and held under bud-forcing conditions for 60 days, or excised to measure cold hardiness using differential thermal analysis.  The onset of endodormancy occurred later in vines under 35% ET_c than vines under 70 or 100% ET_c and transition to ecodormancy occurred earlier in vines under 35 and 70% ET_c than in vines under 100% ET_c. Since all vines were exposed to identical air temperatures and photoperiod, the observed differences in dormancy transitions suggest that vine water status during the growing season can alter the signaling pathway for dormancy initiation and the cold exposure requirements for resumption of growth. This topic warrants further investigation to understand the underlying mechanisms by which water status influences grapevine resilience to adverse environmental conditions.