The first set of analyses investigated the impact of a series of foliar spray applications every fifteen days using different mineral concentrations. The minerals tested were Selenium , Iron , Zinc and Manganese. The Selenium was a chemical reagent, while the other minerals were a commercial fertiliser. Before applying the foliar treatments, we marked the branches with open flowers, and we halted the experiment when we observed ripe tomatoes on the marked branches. Following this, the ripe tomatoes were harvested and dried in a hooven at 70 ˚C and pulverised. Finally, the tomato powders were analysed with an Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES), and the mineral contents were compared to 100 grams (g) of fresh tomatoes. During the treatments, a visual analysis was performed to detect any signs of toxicity in the tomato plant leaves due to the mineral applications. Some evidence of mineral content increase in the tomato fruits were found in Zinc and Manganese. Despite the positive results, the targeted mineral levels of 15% in relation to the Recommended Daily Allowance was still far, especially for Zinc, while in Manganese our results inspired greater optimism that we might reach our objectives. Disappointingly, no substantial evidence was found in plants treated with Selenium and Iron.
The most striking result to emerge from this first set of data is that we were able to biofortify the cherry tomatoes with Zinc and Manganese. However, the quantity of minerals accumulated in tomato fruits was lower than the 15% of the Recommended Daily Allowance. Despite this limitation, our findings suggested that it’s possible to test a higher concentration of minerals, due to the absence of toxic sings observed in treated tomato plants. The experiment was then repeated with a less time-consuming approach, to have an agile protocol for subsequent tests. In particular, only one foliar application was performed, and the tomatoes were harvested six days after the foliar application. On average, we found a significant correlation between treated and untreated plants for Selenium, Zinc and Manganese. Interestingly, we reached the highest accumulation in Selenium and Manganese, that we had obtained so far, despite still being quite far from the 15% of the Recommended Daily Allowance, especially for Selenium .
Finally, considering the positive result obtained in the previous experiment, we decided to continue in one foliar application with Selenium, but with higher concentrations. Also, before applying the foliar treatments, we marked the branches with open flowers, and we harvested when was observed ripe tomatoes on the marked branches.Strong evidence of toxic sings was found with all the Zinc concentrations tested and with Manganese, excepted the lowest concentration of Manganese tested. On another hand, no sign of toxicity was found with all the concentration tested of Selenium. Interestingly, high mineral accumulation in fruits was found with Selenium and Manganese. Despite the toxicity induced in plants by the treatment with Zinc, the analysis was performed in any case, showed significant accumulation in fruits The most striking results to emerge from this data is that in Manganese we reached almost 30% of the Daily Recommended Allowance for Manganese and as far as we know, no other authors or inventors have found a biofortification protocol in Tomato, with such high accumulation level of this mineral.
