Application and Mechanism of Action of Carvacrol Against Aspergillus niger Causing Postharvest Rot of Garlic Scapes (Allium sativum L.)

During prolonged storage of garlic scapes (Allium sativum L.), the proliferation of microorganisms, particularly fungi, frequently results in postharvest rot, which negatively impacts both product quality and market value. Carvacrol, a promising natural food preservative, exhibits broad-spectrum bioactivity against various microorganisms. In this study, a specific pathogenic fungal strain causing postharvest rot in garlic scapes, designated as HQ, was initially isolated from symptomatic garlic scapes. Based on a combination of physiological characteristics and molecular identification techniques, the HQ strain was identified as Aspergillus niger. Our findings further demonstrated that carvacrol exhibits significant in vitro inhibitory effects against Aspergillus niger with an EC50 value of 75.99 μg/L. Moreover, scanning electron microscopy (SEM) observations revealed that carvacrol induces irreversible morphological and structural changes in the hyphae, resulting in deformation and rupture. Additionally, integrated transcriptomic and proteomic analyses indicated that carvacrol primarily targets the cell wall integrity (CWI) signaling pathway within the mitogen-activated protein kinase (MAPK) signaling pathway in Aspergillus niger, thereby compromising cell membrane integrity and stability, which ultimately suppresses fungal growth and proliferation.