2.5. Biocontrol experiments on detached grape berries
For each yeast strain, four grape (cv. Italia) bunches, each bearing five mature berries, were prepared, disinfected with 1% sodium hypochlorite for 10 min and rinsed twice with sterile distilled water. Berries were wounded with a sterile needle (2 mm diameter, 1 wound/berry) and whole bunches were dipped into a 50 mL suspension of each antagonist (108 CFU/mL). Bunches were then air-dried and subsequently sprayed until runoff (1 mL/bunch) with an A. carbonarius spore suspension (107 conidia/mL) by using a hand sprayer. After inoculation, grape bunches were placed in plastic boxes (16 × 26 × 10 cm) for 6 days and incubated at 25 °C in the dark under high relative humidity (95 ± 5%). After 6 days berries were checked and a 0–100 disease index was assigned to them according to the percentage (0, 25, 50, 75 and 100%) of berry surface covered by mold.
2.6. VOC experiments on artificially inoculated grape berries
To check whether VOCs produced by the antagonistic yeast strains may inhibit A. carbonarius growth on grape berries, bunches were prepared, wounded and inoculated with the pathogen as previously described. The grape bunches were then placed into plastic boxes whose lids were internally supplied with three open YPD agar (2%) plates inoculated by streaking 100 μL of yeast cell suspension (108 CFU/mL) and previously incubated for 24 h at 25 °C. Plastic boxes were sealed with Parafilm® and cellophane and stored for 6 days at 25 °C under high relative humidity (95 ± 5%). A disease index was then assigned to inoculated berries as previously reported.