Seasonal evolution impact on Montepulciano grape ripening

Abstract. In an environmental background characterized by climate change, the seasonal trend increasingly affects the qualitative and quantitative expression of the vineyards. The sugar concentration, titratable acidity, the ratio sugar/acids and yield were related with heat accumulation (growing degree days accumulation), calculated in different period of grapevine cycle. The 21.5 °Babo threshold has been reached by Montepulciano grapes in the various years (2007-2019) even with 40 days difference. Over a period of 13 years, the sugar of Montepulciano grapes was influenced by thermal evolution between March to July. The relationship with high coefficient determination (R2 0.74) was obtained between heat accumulation and titratable acidity. According to this forecasting model, increases in heat accumulation of 100 degree-days in the period from March to June correspond to a reduction of about 0.85 g/l of acidity of the must at the harvest associated with an increase of 0.75 degree-days in the ratio between sugars and acids. The thermal evolution between June and July was correlated with yield of Montepulciano, an increase of 100 degree-days is associated with a decrease of about 1.86 t/ha. The thermal evolution between March and July is crucial for yield and grape quality of Montepulciano.