THE ROLE OF CO₂ IN REDUCING GREY MOULD-CAUSED DISEASES ON STORED TABLE GRAPES

Grey mould diseases caused by Botrytis cinerea are one of the main factors reducing table grapes postharvest quality. The effect of high CO₂ concentrations on some fruit biochemical parameters in the presence of a high disease pressure was evaluated. Bunches of ‘Italia’ table grapes were artificially infected by spraying with a conidial suspension of B. cinerea, packed in polyamide/polyethylene bags in three different initial modified atmosphere (MA) conditions and stored at 3°C for 18 days. Changes in phenolic compounds in both skin and flesh, glucose and fructose content, polygalacturonase (PG) activity, and the incidence of grey mould rots were evaluated every 6 days during storage. The results showed that high CO₂ concentrations did not significantly affect PG activity which, on the contrary, was found higher in Botrytis-infected samples than in corresponding non-inoculated samples. Moreover, in artificially infected samples, a positive correlation between high CO₂ levels associated to the lowest disease incidence and the high concentration of caftaric acid (the most representative phenolic compound) in the skin, was found. Therefore, it can be assumed that high CO₂ concentrations could contribute to maintain high levels of phenolic compounds in the table grapes’ skin, which, in turn, might be involved in counteracting the disease development.