Preventing fungal proliferation in postharvest grains is critical for guaranteeing the quality and safety of stored grains and their derived products (Atanda, 2011; Milani, 2013). Aspergillus flavus is a filamentous pathogenic fungus that commonly infects cereal grains and produces aflatoxins that contaminate stored grains, can cause serious harm to human and animal health, and consequently, can further result in serious economic losses (Boudjaber et al., 2023; Li et al., 2022a; Zhang et al., 2023). Therefore, sustainable measures are required to control A. flavus infestation in post-harvest grains. Fumigation is a simple and efficient method used to inhibit fungal growth and prevent fungal contamination (Li et al., 2016). Natural gaseous fungicides have shown great potential as biofumigants to control fungal decay in postharvest agricultural products owing to their low toxicity, high efficacy, and environmental friendliness (Li et al., 2021b; Xiang et al., 2020).

Plant volatile organic compounds (PVOCs) are low-molecular-weight, high-vapor-pressure, lipophilic chemicals that can freely pass through the cell membrane and are released into the surrounding environment (Muhlemann et al., 2014; Mun and Townley, 2021; Vuerich et al., 2023). One of the main physiological functions of PVOCs is to protect plants from phytopathogenic infestations. It has also been demonstrated that PVOCs have great potential for controlling phytopathogens and fungal decay in postharvest agricultural products (Duan et al., 2023b; Mari et al., 2016). For example, trans-2-hexenal, carvacrol, and citral have been shown to have fungicidal activities against Monilinia laxa in vitro (Neri et al., 2007), while linalool fumigation has an evident inhibitory effect on strawberries infected with Botrytis cinerea (Xu et al., 2019). Thus, exploration of PVOCs and their active constituents could facilitate the development of effective biofumigants. Oregano (Origanum vulgare L.) is an aromatic plant that is commonly used as a spice and as herbal medicine. Oregano essential oils (EO) have been extensively studied for their antibacterial, antifungal, and antioxidant properties (Kimera et al., 2021). Oregano EO reportedly exhibits significant inhibitory activity against the multidrug-resistant bacteria Acinetobacter baumannii, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus (Lu et al., 2018). Buonsenso et al. (2023) reported that vapor fumigation with oregano EO resulted in significant antifungal activity against Penicillium expansum in vitro. However, the main volatile compounds in oregano EO that exert antifungal activity and their antifungal effects against A. flavus remain unknown.

This study aimed to identify the main volatile components of oregano EO using gas chromatography–mass spectrometry (GC–MS) and investigate the effects of the main volatile constituents of oregano EO on the control of A. flavus infestation during wheat storage. The mechanism underlying the inhibitory effect of the main active volatile constituents of oregano EO on the growth of A. flavus was elucidated using RNA-seq and biochemical analyses. Our findings are expected to provide an effective alternative biofumigant to control A. flavus infestations during the storage of agricultural products.