Predicting the dormancy and bud break dates for grapevines
Bud break is one of the most critical stages in grapevines since it is the beginning of active growth and an accurate prediction is useful for scheduling of orchard activities. However, the prediction of this particular stage is challenging for growers due to the unobservable transition of dormancy phenology. The objective of this study was to develop a model to predict the dates of endodormancy induction, release and bud break for the grapevine. Samples of 18 nodes for the cultivars 'Cabernet Sauvignon' and 'Chardonnay' were collected weekly starting during the middle of the growing season until the occurrence of bud break in the field for the 2013, 2014 and 2015 growing seasons. The nodes were placed in a temperature control chamber at 24°C for forcing conditions and the number of days between sampling and bud break were recorded. Ecodormancy was determined when bud break occurred in less than 30 days, and endodormancy when bud break occurred after 30 days. The onset of dormancy occurred earlier for 'Cabernet Sauvignon' and different requirements of chilling and thermal units were observed between the two cultivars. Though, the base temperature for heat accumulation was the equal for both cultivars. The differences in dormancy induction suggested that this process could be driven by changes in photoperiod and is associated with different critical day length that leads the beginning of dormancy. Chilling units (CU) accumulation governed the prediction of endodormancy release and heat units accumulation controlled the release of ecodormancy and bud break. Thresholds and the corresponding chilling and heat units requirements were identified for the prediction of the dormancy release and bud break in the two cultivars.
Camargo-A., H.A., Salazar-G., M.R., Zapata, D.M. and Hoogenboom, G. (2017). Predicting the dormancy and bud break dates for grapevines. Acta Hortic. 1182, 153-160
ecodormancy, chilling units, heat units, photoperiod, prediction, thresholds, 'Chardonnay', 'Cabernet Sauvignon'