Antioxidant metabolites in tomato organs as response to virus infection

The study regards the effects of eggplant mottled dwarf virus (EMDV) on Campanian tomato ecotypes Tondo Giallo, characterized by long shelf life, and Maiese, on ascorbic acid and polyphenol accumulations as plant response to the infection stress. Such response to virus is little studied, thus, we explored this on ecotypes for which we already found a different pattern of the metabolite accumulations during ripening that we associated also to their different shelf life. The EMDV was mechanically inoculated onto tomato plants grown in greenhouse until the second leaf stage, and virus infection was monitored by symptom expression and ELISA test. Both ecotypes showed almost similar susceptibility to the infection. In post inoculation, for both ecotypes total ascorbic acid (ascorbic and dehydroascorbic acids, tAsA) increased in leaves of diseased plants respect to healthy plants, in these latters higher tAsA was recorded for Maiese than for Tondo Giallo. Also, in leaves, although healthy Maiese showed lower total polyphenols (tPph) than healthy Tondo Giallo, in the diseased ecotypes the relative contents were inverted because tPph contents increased in Maiese and decreased in Tondo Giallo respect to the levels in the respective healthy plants. Both ecotypes, transferred in field, showed higher tPph in the typical discoloured symptomatic fruits, than in those from healty plants at any stage of sampling: immature, mature green, turning and ripe. Instead, tAsA in diseased fruits was generally lower for Tondo Giallo, and at turning and at ripe higher for Maiese, than in fruits from the respective healthy plants. Although both ecotypes were susceptible to EMDV infection, the host response seems to depend by the genotype, since Tondo Giallo did not always show increase in the antioxidant metabolites in the diseased organs as expected, because virus usually upregulates response genes. Investigations on gene regulations in tomatoes by EMDV have to be carried out.