Vineyard vigour, microclimate and secondary metabolites in cv Nebbiolo.

The aim of this study is to identify the relationships between vine vigour, canopy microclimate and secondary metabolite accumulation in cv Nebbiolo berries. The aromatic profile was thoroughly studied during ripening period, paying attention to the carotenoids and their break down products, the C13 norisoprenoid compounds. Both synthesis and degradation of carotenoids may depend on cluster modifications related to/influenced by microclimate but an influence of the cultivar is also probable. Specific reaction of cv Nebbiolo is of high interest for wine industry. Data presented in this paper concern the 2012 growing season and were collected in a commercial vineyard, located in Sinio (CN, Piedmont, North-West Italy), characterized by high vigour heterogeneity. Vineyard parcels were sorted in vine vigour classes, at first, on the base of spring visual aspect; at veraison time, Normalized Difference Vegetation Index (NDVI) of the vineyard was mapped using an Unmanned Aerial Vehicle (UAV) system equipped with a high-resolution multispectral camera. In the vineyard parcels characterized by different vigour level, Photosynthetically Active Radiation (PAR) and air temperature inside the bunch zone were measured in continuous from pea size stage to harvest time. From 15 days after flowering until harvest, berry samples were collected and berry size and main analytical parameters of the must were assessed; the amount of carotenoids and C13 nor-isoprenoid compounds in the berries were also measured. Finally “Total PAR index (TP)” and “thermal index (TI)” were calculated over each period between two berry samplings. UAV remote survey was a fast and reliable tool to estimate the NDVI: thanks to high image resolution, the pixels corresponding to singular plants were identified allowing to subdivide the vineyard in numerous parcels of different vigour. Differences in into-the-foliage microclimate indexes (TP and TI) were found as determined by the plot vigour; nonetheless, only few differences were appraised concerning berry chemical composition. It seems that the variation in cumulative temperature, both below 15 °C during pre harvest weeks and exceeding 35 °C around veraison, may influenced berry composition at harvest but the exact interaction between this two aspects needs further investigation.