Elementi minerali anche in traccia nel sistema suolo-vite: accumulo e distribuzione nelle bacche e tracciabilità geografica delle uve

As yet, there is not in-depth knowledge of the biological role and concentration levels in plants for most mineral and trace elements in the soil-vine system. Analysis of the mineral element profile is considered a promising fingerprinting technique for determination of the geographical or geological origin of agricultural and food products. This research aims to quantify more than 50 mineral elements in soil, soil-water, xylem exudates, leaf and berry samples, to describe the mineral element increase in the berry during development and maturation using a mathematical model, and to define mineral element distribution in the different parts of the berry. A further aim is to statistically link soil and berry mineral composition in order to make it possible to trace the origin of grapes. The first step in the research was to optimise preparatory and analytical ICP-MS methods for subsequent analysis. In 2006, 2 vineyards were chosen, with different pedoclimatic characteristics but similar in terms of management and trellising systems and the cultivar studied. Leaf and berry samples - these last being subdivided into seed and skin parts in the final phase of maturation - were collected here during the vegetative season. During harvesting, leaf and berry samples were also collected in a further 9 vineyards in Trentino (Italy) and this sampling was partially repeated over 2 years. Soil samples were collected in each vineyard and analysed in order to determine the mineral content extractable with aqua regia and the bioavailable content. For evaluation of this second fraction, 4 extraction methods were compared: using ammonium acetate 1M pH 7, ammonium nitrate 1M, with DTPA 0.005M+CaCl2 0.01M (for alkaline soils), EDTA 0.02M+ammonium acetate 0.5M (for acid soils) and citric acid 0.1 mM. On the basis of the different accumulation and distribution patterns in the berry studied in the 2 vineyards with alkaline soil, it was possible to classify trace mineral elements into 3 different groups: elements mainly present in the seeds accumulating before veraison, those localised in the flesh accumulating continuously during the development and maturation of the berry and other elements, localised mainly in the skin or equally distributed between the skin and the flesh, which accumulate above all before veraison but also during maturation. Of the different soil extraction methods compared, on average ammonium acetate solution gave the best results, the mineral composition of this soil extract being statistically correlated with that of the berries growing on it. Using a regression model linking the concentration of 10 elements in grapes and ammonium acetate extracted soil and knowing the mineral composition of grapes, it is possible to predict the mineral composition of the soil of origin. The effectiveness of the model was verified using 7 grape samples not previously included within the model, which were correctly associated with the soil of origin