Effect of Rootstock on anthocyanins profile in blood oranges

Blood oranges are characterized by their high content of anthocyanins which, in addition to conferring the fruit its characteristic red color, are related to human health properties due to their antioxidant activity. The aim of this study was to evaluate the effect of rootstock on the internal color and anthocyanin content of 'Moro' and 'Tarocco Rosso' throughout the harvest period. The rootstocks studied were ‘Carrizo’ (CC), ‘C-35’, ‘Cleopatra’ mandarin (CL), ‘Citrus volkameriana’ (VK), ‘citrus macrophylla’ (M), ‘Swingle’ citrumelo (CT), ‘Forner-Alcaide 5’ (FA5) and ‘Forner-Alcaide 13’ (FA13). Over fruit collected at three harvest times, four anthocyanins were determined in the fruit juice: delphinidin 3-glucoside (Dp-3-glu), cyanidin 3-glucoside (Cy-3-glu), cyanidin 3-(6″-malonyl)-glucoside (Cy-3,6″mal-glu) and cyanidin 3-(6″-dioxalyl)-glucoside (Cy-3,6″diox-glu). A significant effect of rootstock was found in both cultivars. Fruit juice of 'Moro' grafted on CL presented the highest internal color index throughout the harvest period studied. CT fruit, with the lowest values at first harvest, exhibited the least reduction as the season progressed. C35, M and VK fruit displayed a significant decrease in color and reached similar values to CT fruit at the third harvest. No significant changes were found in the juice color of 'Tarocco Rosso' oranges as the harvest advanced. C35, M and CT induced the lowest color values, while the highest values were found in FA5 fruits. The higher color of ‘Moro’ juice compared to ‘Tarocco Rosso’ was explained by the content of all the individual anthocyanins. Cy-3-glu and Cy-3,6″mal-glu were the major compounds in both varieties followed by Cy-3,6″diox-glu and Dp-3-glu. In ‘Moro’, Cy-3,6″mal-glu and Cy-3,6″diox-glu contributed mostly to juice color intensity and their degradation at the last harvest caused a loss of juice color in most rootstocks. In ‘Tarocco Rosso’, the rootstocks with the lowest color were those with the lowest content of all anthocyanins determined.