Advanced intervention methods for pear fruit fungi and characterization of their growth dynamics

Abstract

As many of the most popular fungicides are expected to be banned, due to their high toxicity and potential carcinogenicity to humans, there is the need to better characterize the pear postharvest fungal pathogens in order to design new specific intervention solutions against them. The postharvest fungi Penicillium expansum, Alternaria alternata, Botrytis cinerea and Rhizopus stolonifer have been selected for this study. A primary cardinal model with inflection (CMI) prediction approach showed that R. stolonifer was the most aggressive fungus since it had the highest μopt= 1.22±0.02 [h-1], while P. expansum could be the most psychrophilic fungus since it showed the lowest estimated Tmin = -7.2°C. Hereafter, the efficacy of zinc oxide nanoparticles (ZnO NPs) has been investigated against the fungal isolates through a preliminarily implemented turbidimetric assay on semi-solid PDA medium. Results showed that ZnO NPs were successfully inhibiting the growth of the four isolates and that turbidimetry is a reliable technique for assessing their antifungal activity. The updated version of the Lambert Pearson model was used to estimate the MIC and the NIC values for the fungus Penicillium expansum, which were found to be 9.8 and 1.8 mM respectively. The physiological effects and the mode of action of ZnO NPs were also investigated by scanning electron microscopy (SEM) and by a chemical assay with EDTA, showing that ZnO NPs cause irreversible morphological aberrations on the fungal structures of all the isolates and that ions release is crucial for their antifungal activity. Finally, the efficacy of compressed polyurethane foams (PU), as an effective antifungal filtration system, is assessed. Controlling the air particulate could be achieved giving potential for future applications in postharvest storage facilities.