VINEYARD MICROCLIMATE AFFECTS ANTHOCYANIN CONTENT AND CANOPY ECOPHYSIOLOGY.

The amount of anthocyanins in grapevine is highly subjected to influence from the climate. Air temperature and radiation inside the canopy affect secondary metabolism pathways in leaf and berry. In this work we compared for two years (2010 and 2011) the anthocyanin content of Nebbiolo berries harvested in three vineyards (Alba, Serralunga and Novello, Cuneo Province, Italy) characterized by different rootstock, soil and climate conditions. A meteorological station was located in each vineyard to measure air temperature, relative humidity and rainfall. Furthermore, in the Serralunga vineyard, wireless micro-sensors of temperature and relative humidity were set to check microclimate differences at the vineyard scale. Leaf gas exchange and water potential were measured during summer in order to check for stress events that could activate responses at the secondary metabolism level. At harvest the anthocyanin content was measured by an optical portable sensor, Multiplex® (ForceA, Paris, France) and by spectrophotometry. GIS software was used to describe the spatial distribution of temperature, photosynthetically active radiation (PAR) and anthocyanin accumulation. Several relationships between anthocyanins, climatic variables (temperature and relative humidity) and bioclimatic indexes (cumulated number of thermal units Σ NHH, and cumulated PAR Σ PAR) were analyzed in order to assess which factors may be favorable or limiting for anthocyanin accumulation. Preliminary results show that in the highly dry 2011 season the higher anthocyanin content was observed in the cooler areas. Ecophysiological analysis allowed identification of drought stress periods influencing leaf gas exchange and following specific patterns in the different vineyards. Identification of drought stress periods during the summer could be used to understand limitations to secondary metabolism either at the vineyard or regional scales.