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 (TM)). 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 (10(5) 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 degrees 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.