Antifungal Activity of Essential Oil Compounds (Geraniol and Citral) and Inhibitory Mechanisms on Grain Pathogens (Aspergillus flavus and Aspergillus ochraceus)

Abstract

The grain contamination by <i>Aspergillus</i> spp. has been a serious issue. This study exhibited the excellent antifungal effects of the essential oil compounds (EOCs) geraniol and citral against common grain pathogens (<i>A. flavus</i> and <i>A. ochraceus</i>) in vitro and in situ. The inhibitory mechanisms were also evaluated from the perspective of cell membrane permeability, reactive oxygen species (ROS) generation, and <i>Aspergillus</i> spp. growth-related gene expression. Meanwhile, the combined effects of EOCs in the vapor phase and modified atmosphere packaging (MAP) were examined to find an alternative preservation method for controlling <i>Aspergillus</i> spp. The results indicated that citral exhibited the antifungal activity mainly by downregulating the sporulation- and growth-related genes for both pathogens. Geraniol displayed inhibitory effectiveness against <i>A. flavus</i> predominantly by inducing the intracellular ROS accumulation and showed toxicity against <i>A. ochraceus</i> principally by changing cell membrane permeability. Furthermore, the synthetic effects of EOCs and MAP (75% CO₂ and 25% N₂) induced better grain quality than the current commercial fumigant AlP. These findings reveal that EOCs have potential to be a novel grain preservative for further application.