Influence of thermal requirement in the aerobiological and phenological behavior of two grapevine varieties

Knowledge about the timing of the aerobiological and phenological processes in plants with economic interest results of great agronomical importance, mainly for the establishment of the adaptive capacity of different varieties to various environmental conditions and the optimization of cultural practices. An agrometeorological study in two authorized varieties (Treixadura and Godello) of the Designation of Origin Ribeiro (North-western Spain) was conducted during the years 2008–2011. As consequence of the studied area bioclimatic conditions, the grapevine cycle exceed than 190 days and the varieties cultivated are considered as “late varieties.” The presence of Vitis pollen grains in the vineyard atmosphere was mainly registered during the stages 5 (inflorescence emerge) and 6 (flowering) which benefit a successful fertilization process. The variations in airborne pollen concentrations are related to temperature and humidity. Phenological models proposed in this paper offer a high accuracy as the standard deviation of error between estimated and observed values was low. The prediction variability ranges around 2 phenological scales in 2008 and 1 phenological scale in 2009, 2010 and 2011. These results indicate that the models developed to predict the phenology, in terms of degree days accumulated (GDD) using as a threshold temperature 10 °C, can be a useful tool to forecast the successive phenological events in the Designation of Origin Ribeiro area. During the stage 8 (ripening of berries), the GDD and the Brix Index were particularly correlated, so far as the differences between plants of the same variety are minimal.