Effects of plastic screens on virus infection, yield and qualitative characteristics of small tomatoes

The covering of crops with plastic screens has increased during last years for their protective capacity against vegetable insect pests and virus. To investigate if crop covering can also affect yield level and fruit nutritional quality, we have compared two small tomato varieties ("Corbarino" and "Faino") cultivated in open field and under high tunnel made by two types of covering tissue: a white, 90% transparent tissue ("anti-aphid net") and a "non-woven fabric" ("t-nt"). The "t-nt", which has a closer mesh than "anti-aphid net", proves to be efficient against both pathogens CMV and TSWV, while the other is only effective against CMV. Both covering tissues led to a 30% average reduction of the light intensity; to a rise of 10% in the production yield; to an increase of fruit weight and to a more uniform size of the fruits with respect to the control. Carotenoids concentration in "Corbarino" increased by about 20% with both types of covering tissues, while it remained unchanged in "Faino". Flavonoids concentration was not affected in both varieties. The data on carotenoids were confirmed by a corresponding increase observed only for "Corbarino" tomatoes in the lipophilic antioxidant activity.