Understanding dormancy release in apricot flower buds (Prunus armeniaca L.) using several process-based phenological models.

tThe present study was an initial attempt to calibrate a phenological process-based model of dormancyrelease with experimental data for apricot flower buds. A large experimental database (88 data points)on dormancy release, concerning several cultivars grown at different geographical sites, was used for themodel parameterization. We compared five phenological models. None of them provided accurate pre-diction of the date of dormancy release at the species level. This inaccuracy appeared to be due to the highvariance in dormancy release dates among cultivars. Models fitted for different dormancy release pre-cocity groups provided much more accurate predictions. Parameter estimate analysis of the best modelfor each cultivar group showed very marked differences in apricot flower bud response to temperaturewithin the species. While in early cultivars dormancy release seemed to be driven by the daily minimumtemperature, the daily mean temperature appeared to be the controlling factor in intermediate and latecultivars. Our results show that the apricot dormancy release date cannot be predicted accurately at thespecies level and that different models should be used for different precocity groups.