Relationship between bud cold hardiness and budbreak in two vitis vinifera L cultivars, chardonnay and thompson seedless

Abstract

The lack of winter cold is a severe limitation for the cultivation of grapevines (Vitis vinifera L) in areas with warm winter climates. This phenomenon is currently becoming quite important due to global warming, which will increase winter temperatures in many temperate regions of the planet where grapevines are cultivated. Although various physical and chemical stimuli have been used to address the lack of winter cold in grapevine cultivation, quantitative studies on its effects on different cultivars are limited. Here, the effects of (a) low temperatures during endodormancy (ED), (b) temperature increases during eco-dormancy (ECD) and (c) the effects of dormancy-breaking compounds such as hydrogen cyanamide (HC) and sodium azide (AZ) on the budburst of an early budbreak cultivar, Chardonnay, and an late budbreak cultivar, Thompson seedless, were assessed. The results were analysed by the Kaplan-Meier method, and the log-rank test was used to establish statistical significance between the control and treatments. In general, Chardonnay grapevines were more sensitive than Thompson seedless grapevines to all budbreak stimuli, and a temperature increase during ECD was the stimulus that had the greatest effect on the budbreak in both cultivars. Exposure to cold temperatures during ED increased the cold hardiness and improved the budbreak in both cultivars. Based on the results, a relationship between the degree of bud cold hardiness and budbreak potential is suggested, and it is proposed that the greater the cold hardiness achieved by the buds, the better their subsequent budbreak will be.