Chemical compositions and in vitro antifungal activities of essential oils obtained from different Origanum species against postharvest gray mold rot of persimmon fruit

A gray mold disease agent, Botrytis cinerea causes considerable losses during storage and transportation of persimmon fruit. Although fungicides were commonly used for postharvest disease management of persimmon fruit, restrictive regulations regarding fungicide residues, the emergence of fungicide-resistant isolates, and increasing public concern on pesticide have led to a global increase in the need for safer postharvest alternatives to control the decay of fruits. In this study chemical compositions and antifungal activities of essential oils (EOs) obtained from different Origanum species, such as O. syriacum, O. vulgare, O. onites, O. minutiflorum and O. majorana were determined. The antifungal activities were determined by measuring inhibitory effect against mycelial growth of B. cinerea in vitro. Chemical compositions of EOs of O. syriacum, O. vulgare, O. onites and O. minutiflorum were characterized with the presence of high amounts of carvacrol, thymol and γ-terpinene as major compounds. Different concentrations of the EOs were found to inhibit the growth of B. cinerea in a dose-dependent manner. Among the EOs tested, EOs from O. syriacum showed the strongest antifungal activity, with minimum inhibition concentration (MIC) value of 0.5 μL Petri^-1 followed by O. vulgare, O. onites and O. minutiflorum EOs with MIC values of 0.75, 1.0 and 2.0 μL Petri^-1, respectively. Complete mycelial growth inhibition of B. cinerea by EOs of O. majorana was observed at relatively higher concentration (8.0 μL Petri^-1). The high antifungal activities of EOs of O. syriacum, O. vulgare, O. onites, O. minutiflorum appear to be related to their chemical compositions. Chemical compositions of O. syriacum, O. vulgare, O. onites, O. minutiflorum EOs were characterized as rich in carvacrol and thymol. The strong antifungal activities displayed by EOs rich in carvacrol and thymol from O. syriacum, O. vulgare, O. onites and O. minutiflorum may be considered as good alternatives for developing bio-fungicides to suppress the postharvest disease agent tested in this study.