Iodine uptake and distribution in horticultural and fruit tree species

Iodine is an essential microelement for humans and iodine deficiency disorder (IDD) is one of the most widespread nutrient-deficiency diseases in the world. Iodine biofortification of plants provides an attractive opportunity to increase iodine intake in humans and to prevent and control IDD. This study was conducted to investigate the iodine uptake and accumulation in edible portion of two fruit trees: plum and nectarine, and two horticultural crops: tomato and potato. Two type of iodine treatments (soil and foliar spray application), and, for fresh market tomato, two production systems (open field and greenhouse hydroponic culture) were tested. The distribution of iodine in potato stem and leaves, and in plum tree fruits, leaves, and branches was investigated. Iodine content of potato tubers after postharvest storage and processing (cooking), and iodine content of nectarine fruits after postharvest storage and processing (peeling) were also determined. Differences in iodine accumulation were observed among the four crops, between applications, and between production systems. In open field, the maximum iodine content ranged from 9.5 and 14.3 μg 100 g−1 for plum and nectarine fruit, to 89.4 and 144.0 μg 100 g−1 for potato tuber and tomato fruit, respectively. These results showed that nectarine and plum tree accumulated significantly lower amounts of iodine in their edible tissues, in comparison with potato and tomato. The experiments also indicated hydroponic culture as the most efficient system for iodine uptake in tomato, since its fresh fruits accumulated up to 2423 μg 100 g−1 of iodine. Iodine was stored mainly in the leaves, in all species investigated. Only a small portion of iodine was moved to plum tree branches and fruits, and to potato stems and tubers. No differences in iodine content after fruit peeling was observed. A significant increase in iodine content of potato was observed after baking, whereas a significant decrease was observed after boiling. We concluded that iodine biofortified fresh market tomato salad, both from field and hydroponics cultivation, and baked potatoes can be considered as potential functional foods for IDD prevention.