Effectiveness of three GRAS compounds in the in vitro control of two Penicillium italicum strains

One of the main etiological agents of postharvest citrus decay is blue mold caused by Penicillium italicum. This pathogen is currently controlled by the application of synthetic fungicides. The use of postharvest chemicals is essential if fruit is destined for storage, since postharvest life would be significantly reduced. However, concerns regarding human health and environmental risks, associated with chemicals residues in food have driven the search for alternative safe control methods. In the present study three substances as referred as GRAS (Generally Recognized as Save) compounds, previously found active against some phytopathogenic fungi, have been tested in vitro against two Penicillium italicum strains. The tested compounds were acetic acid, acetaldehyde and cinnamic aldehyde used at different concentrations (5, 10, 20 and 50 ppm) and applied as fumigation after 0, 24 and 48 h from inoculation, in order to evaluate the control of the pathogen radial growth. The effectiveness of the treatments was affected by the investigated parameters: characteristics of the GRAS, concentration and time elapsed between inoculation and treatment. The treatment performed after 0 h showed a significant difference, by the three compounds, in the control of the radial growth of the pathogen. Acetic acid revealed the main ability by completely inhibiting the pathogen development at 20 ppm, while acetaldehyde and cinnamic aldehyde were less effective in the control. The treatment applied after 24 h, in general, showed a greater capability in the control, probably related to particular pathogen sensitivity during the different vegetative stages. The treatments carried out after 48 h showed a very low effectiveness for acetaldehyde and cinnamic aldehyde in controlling the pathogen development and significantly reduced for acetic acid. Furthermore the experiment demonstrated that the pathogen strains also affected the effectiveness of the treatments.