Freeze-Induced Dehydration and Its Impact on Freezing Resistance in Dormant Grapevine Buds

Under freezing stresses, non-lethal cell dehydration in plants can facilitate the concentration of intracellular solutes, thereby improving cold hardiness. While freeze-induced dehydration of primordial tissues has been reported in dormant compound buds of Vitis riparia and the interspecific hybrid grape cultivar 'Yamasachi,' its occurrence in other Vitis species and grape cultivars remains unclear. In this study, we evaluated the presence or absence of freeze-induced dehydration in compound buds of two Vitis vinifera and three interspecific hybrid cultivars and a wild grape (Vitis sp.), mainly using differential thermal analysis. In all tested genotypes, exothermal peaks from compound buds disappeared or diminished after a freeze-dehydration treatment at -15°C for 3 days, indicating that primordial tissues were at least partially dehydrated under freezing stress. In addition, the ability of compound buds of 'Yamasachi' to dehydrate under freezing conditions changed during cold acclimation and deacclimation. These findings suggest that freeze-dehydration is a complementary freezing adaptation strategy in wild grape species and cold-climate commercial cultivars. This mechanism, alongside freezing avoidance, enhances their capacity to endure extreme minimum temperatures, particularly in mid-winter.