The role of linalool in managing Alternaria alternata infection and delaying black mold rot in goji berry

Alternaria alternata, a common fungal pathogen causes black mold in postharvest goji fruit. To explore the in vitro and in vivo impacts of linalool on the fungal infection, we treated A. alternata and infected goji fruit with varying linalool concentrations (0, 0.15, 0.45, and 1.35 mL L⁻¹). Linalool repressed hypha growth, spore yield and germination, and germ tube length of A. alternata. Furthermore, we observed abnormal spore and mycelium morphology in the treated samples using optical, scanning electron, and transmission electron microscopy. Linalool reduced lesion diameter and disease incidence in goji fruit. Moreover, transcriptomic analysis of pathogen revealed that linalool inhibited nitrogen metabolism, altered chitin and β-1,3-glucan metabolisms, downregulated the key gene expression related to ergosterol synthesis and sulfur and glutathione metabolisms, regulated the enzymatic antioxidant system, and impacted the proportion of unsaturated fatty acids. Furthermore, linalool damaged the fungal cell wall integrity by inducing alkaline phosphatase and chitinase activities and β-1,3-glucan content and repressing β-1,3-glucanase and chitin synthase activities and chitin levels. Linalool elevated superoxide dismutase and catalase activities and declined peroxidase and glutathione reductase activities and glutathione content in A. alternata, leading to increased H₂O₂ levels and ROS stress. Our data exhibited the promising antifungal effects of linalool with a future application in management of the postharvest rot of goji fruit.