In Vitro Antifungal Activity of White Thyme, Oregano, and Savory Oils Against Five Monilinia fructicola Isolates from the Southeastern United States

Abstract

Monilinia fructicola is a primary pathogen causing fruit brown rot of peach during pre- and postharvest in the southeast of the United States. In this in vitro study, we assessed the antifungal activity of four plant essential oil treatments against five isolates of M. fructicola obtained from naturally infected peaches in Florida, Georgia, and South Carolina. The tested essential oils were white thyme oil, oregano oil, summer savory oil, and a 1:1 mixture of thyme and oregano oils. We evaluated isolates’ growth using a Gompertz growth curve model. All tested essential oils exhibited antifungal activity against all isolates, with thyme, oregano, and the 1:1 mixture of thyme and oregano oils showing no significant differences and no evidence of synergy. Savory oil showed the least effectiveness and stability of the four essential oil treatments. We observed diverse sensitivities of different M. fructicola isolates to the essential oils. The minimum inhibitory concentration values for the essential oils ranged from 200 to 500 μl/liter, and the minimum fungicidal concentration values varied from 500 to 750 μl/liter, depending on the fungal isolate and essential oil treatment. All isolates were inhibited by the essential oils at 500 μl/liter and killed at 750 μl/liter. Our findings provide a basis for future in vivo research on the use of these essential oils for controlling fruit brown rot caused by M. fructicola in peach postharvest handling. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .