EFFECTS OF THE AMOUNT OF LIGHT ON THE NUTRITIONAL COMPOSITION AND QUALITY OF THOMPSON SEEDLESS BUNCHES

The amount of light a vine receives affects its nutritional composition and fruit quality. In highly productive four-year old Thompson Seedless vineyards, from Chile’s central region (33º 44' 37.90" S, 70º 45' 50.23" W), samples of bunches that received high (PAR ~ 946 µmol m^-2 s^-1), and low (PAR ~ 103 µmol m^-2 s^-1) light levels were analyzed. At harvest time fruit nutritional composition, mean berry weight (g), sugar content (°Brix), acidity (%) and firmness (Durofel unit), and N, P, K, Ca and Mg concentrations in skin and pulp of berries were measured. Results showed that bunches grown under high light levels were larger, and had significantly firmer and larger berries than those under low light levels. There were significantly higher concentrations of Ca and K in bunches under high light condition, but Mg and N were higher in bunches under low light levels. In the case of pulp’s composition, N, P and Mg concentrations were significantly higher under low light levels. P concentration in the skin was similar in both types of bunches, but not in the pulp, which was higher in berries under low light conditions. Higher Ca levels in bunches under high light might explain why those berries were firmer, which in turn may result in fruit with longer post-harvest life. On the other hand, higher N level from low light bunches may result in higher berry susceptibility to post harvest diseases.