Short Exposure to Sublethal Heat Shock Facilitates Dormancy Release in Grapevines

Abstract

A wet heat shock (WHS) treatment in a water bath at 50°C for 1 hr is a powerful stimulus for grapevine budbreak. However, this treatment is not feasible as a horticultural practice in commercial vineyards. The development of an effective horticultural dormancy release practice favors a short, intense heat shock that combines convenient application and effective stimulation of budbreak. Thus, the influence of heat shock temperature and duration on dormancy release of grapevine buds was studied. Results suggested that in both WHS and dry heat shock (DHS) treatments, increased temperature can compensate for shortened shock duration. In addition, it appeared that buds better tolerate DHS than WHS. Based on these results, we analyzed the effect of short and intense heat shock on budbreak. A DHS of 10 to 30 sec at the sublethal temperature of 150°C served as a powerful stimulus of dormancy release. This short shock induced production of acetaldehyde and ethylene from the buds, as follows application of hydrogen cyanamide. This similarity suggests that analogous mechanisms are activated by the short, sublethal temperature pulse and the commercially used chemical stimulus. The efficiency of short and intense heat shock, which has not been previously documented, will aid the development of a feasible and practical treatment in commercial vineyards.