Classification for timing of flowering and veraison of a wide range of Vitis vinifera cultivars with the “GFV” model

Abstract

In viticulture, the timing of phenology is critical to optimize grape quality potential particularly so in cool climates. Flowering and veraison are key phenological stages for grapevines. The timing of phenology is primarily driven by genotype (cultivar) and temperature. Recently, a Grapevine Flowering Veraison model (hereafter called GFV model) has been developed to predict flowering and veraison for the species Vitis vinifera L. by summing daily mean temperatures starting at Day Of the Year 60 (Northern hemisphere) with a base temperature of 0°C. Heat requirements vary according to the cultivar. This research aims in establishing a classification for the timing of flowering and veraison for wide range of Vits vinifera cultivars. For this purpose, a database was created including over 2000 flowering and over 2000 veraison observations from 123 locations (predominantly in France), spanning over 48 vintages. For each phenology observation, daily mean temperatures were available from a weather station located less than 5km from the point of observation. The altitude difference between the point of phenology observation and the weather station was less than 100m. The output of this research is a classification of the heat requirements for Vitis vinifera cultivars, based on the GFV model. Various statistical measures were used to assess the performance and predictions of the model at the cultivar level. Model outputs can be used in combination with predicted climate change scenarios in order to provide primary information of the adaptability of cultivars under future climate conditions.