Seasonal carbohydrate changes and cold hardiness of Chardonnay and Riesling grapevines

Cold hardiness and endogenous levels of soluble sugars were monitored during the dormant season for Chardonnay and Riesling (Vitis vinifera L.) dormant buds and stem cortical tissues. Endogenous levels of glucose, fructose, raffinose, and stachyose were strongly associated with cold hardening, increasing from the onset of cold acclimation in August to maximum cold hardiness in December and January. During dehardening in March and April, endogenous levels of these sugars dropped as temperature increased. A high ratio of glucose and fructose to sucrose coincided with maximum cold hardiness, and a low ratio was associated with the dehardened condition in fall and spring. Sucrose levels, however, were not associated with cold hardiness in either cultivar. Neither cold hardiness nor soluble sugars of grape tissues were influenced by a late harvest compared to harvest at normal fruit maturity.