Chemical-induced resistance against post-harvest infection enhances tomato nutritional traits

Grey mould post-harvest infection caused by Botrytis cinerea, one of the main causes of decay in harvested tomato, was controlled by inducing resistance with the plant activator benzothiadiazole (BTH, Bion™). Ripened red tomatoes (cv. Ciliegino), of uniform size and colour, were sprayed every other day with 0.3 mM BTH, three times, then inoculated by injection of a conidial suspension (105 spores ml−1) deep into the pericarp. In BTH-untreated controls, mycelium developed concentrically from the inoculation site at the 48th h after incubation at 20 °C, 99% relative humidity (RH), and disease markedly increased after the 4th day, with a maximum development at the 8th day, when most of the berry was infected. In BTH-treated tomatoes, the reduction of mycelium spreading was 71%, though in many cases fungal growth was completely inhibited. HPLC analysis showed an increase of lycopene content in treated vs. control tomatoes by 15.7%, while tocopherol and salicylic acid remained unchanged. The increased lycopene content was confirmed by an innovative technique, based on the microscopic analysis of lycopene crystalloids with epifluorescence and a dichroic mirror. These results showed that post-harvest induced resistance, besides being successfully employed in crop protection, could be a valid tool for improving the health benefits of plant foodstuffs.