Antifungal activity screening for mint and thyme essential oils against Rhizopus stolonifer and their application in postharvest preservation of strawberry and peach fruits

With a goal to identify specific essential oils that can control postharvest Rhizopus rot on strawberry and peach fruits, we performed screening for 26 essential oils based on their antifungal activity against Rhizopus stolonifer in vitro and investigated the underlying mechanism. Mentha spicata (Ms), Mentha piperita (Mp), Thymus vulgaris CT carvacrol (Tc) and Thymus vulgaris CT thymol (Tt) exhibited strong inhibition on R. stolonifer growth in the screening. These essential oils increased plasma membrane permeability of R. stolonifer and resulted in the outflow of intercellular electrolyte, nucleic acid, protein and soluble sugar. Morphology of R. stolonifer mycelia was greatly altered by these essential oils. Hyphae treated by these essential oils exhibited high accumulation of superoxide anion and malonaldehyde. Combination of these essential oils in commercial package reduced Rhizopus rot on strawberry and peach fruits, with Mp showing the strongest efficiency. Ms, Mp, Tc and Tt essential oils inhibited R. stolonifer growth by targeting its plasma membrane and reduced Rhizopus rot on strawberry and peach fruits. This study provides potential applications of natural plant extract, as alternatives to tradition fungicides, to control postharvest decay on fruits and vegetables.