Plants respond to annual climate conditions, the grapevine being particularly sensitive to temperature and water regime. The variation in length of physiological states such as ripening, and the final composition of grapes, show a crop response to the weather. The aim of this study was to analyze the evolution of the bio-indices and determine the cv. Tannat plant responses to climate variability observed in a number of years in southern Uruguay. In a period of sixteen years, we assessed climate conditions through bio-indices (Index of Hulgin Heliothermic IH, Freshness Index of Nights IF, and IS Drought Index), considering temperature, precipitation and potential evapotranspiration during growing season. We analyzed dates of veraison and harvest, water status, berry weight and berry composition at harvest. Bio-climatic indices showed a strong variability for the studied period. IHshowed an increase of 2.25%, while IF declined 0.43 ºC. IS was the index of highest variability, with wet years and years with moderate drought. We observed the shortening of the ripening period, an advance in verasion and harvest dates (R2 =0.91, P=0.0001 and R2 =0.74, P=0.0001 respectively), and a change in the final composition of the berry, with a tendency of reducing grape acidity at harvest (R2 =0.82, P=0.0001)
