Inhibitory effect and mechanism of slight water loss combined with cinnamon essential oil coating on gray mold in <i>Actinidia arguta</i> fruit

Abstract Actinidia arguta is susceptible to infection by gray mold (Botrytis cinerea), which causes fruit rot and reduces marketable value. Both slight water loss (SWL) and cinnamon essential oil (CEO) coatings can inhibit fungal growth and induce defensive responses in plants. This study investigated the inhibitory effect of SWL (4%) combined with a CEO coating (1%) on gray mold in A. arguta fruit, as well as the underlying mechanism of action. The results showed that SWL, CEO coating, and the combined treatment significantly reduced decay incidence. Among these treatments, the combined application was the most effective, reducing decay incidence from 66.7% to 44.7%. This composite treatment effectively maintained fruit sensory quality, including color, texture, soluble solids, titratable acidity, total phenols, flavonoids, and organic acid content, while enhancing the activities of phenylalanine ammonia-lyase (PAL), 4-coumarate-CoA ligase (4CL), cinnamate 4-hydroxylase (C4H), and shikimate dehydrogenase (SD) and increasing lignin content in A. arguta fruit. In addition, the treatment suppressed increases in relative electrical conductivity and malondialdehyde content. These findings suggest that the combined treatment may activate the phenylpropanoid metabolism pathway by enhancing enzyme activities, thereby increasing lignin accumulation and ultimately improving the resistance of A. arguta fruit to gray mold through synergistic effects. This provides a useful reference for controlling postharvest gray mold in Actinidia arguta.