Poster: Biology & Disease Mgmt: Biological Control
Quantitative assessment of the efficacy of ZnO nanoparticles against selected fruit fungal contaminants
D. SARDELLA (1), R. Gatt (2), S. Decelis (3), V. Valdramidis (4) (1) University of Malta, Malta; (2) University of Malta, Metamaterials Unit, Malta; (3) Ministry for Health, Malta; (4) University of Malta, Faculty of Health Sciences, Malta
The use of traditional antifungals to control postharvest diseases has been reviewed or banned during the past years. Nanoparticles represent an alternative for postharvest disease management, either as coating agents or embedded into warehouses’ filters. The efficacy of zinc oxide (ZnO) was assessed following the identification of the optimal growth temperature of Penicillium expansum, Alternaria alternata, Botrytis cinerea and Rhizopus stolonifer. Fungi were inoculated (105-106 spores/mL) onto SDA plates and incubated at temperatures from 5°C to 35°C under constant aw. Mycelium diameters were measured and then fitted to a linear model to estimate the growth rate (μ) and the apparent lag time (λ). The properties of ZnO (3 to 15 mM) were evaluated for the previously identified optimal growth temperature by mycelium diameter and optical density (OD) measurements recorded every 20 min for up to 6 days with a 96-well microtitre reader at 600 nm. P. expansum and B. cinerea could grow even at 5°C while R. stolonifer had the highest μ = 0.383 ± 0.002 (cm/h) at 25oC and the shortest λ = 17.703 ± 0.228 (h) at 18oC. The antifungal tests showed R. stolonifer and P.expansum as the most sensitive to ZnO being completely inhibited even at 3 mM. A. alternata and B. cinerea were inhibited at 12-15 mM. These results were confirmed by the OD assay. ZnO nanoparticles thus appear as an effective antifungal and their efficacy can be assessed by quantitative mycological studies.