Cuminaldehyde-induced oxidative stress inhibits growth of Penicillium digitatum in citrus

Cuminaldehyde (CA) has a strong antimicrobial activity against an array of pathogens. In this study, its growth inhibitory effect on a wild type strain (Pds01) and an imazalil-resistant strain (Pdw03) of Penicillium digitatum , the causative agent of postharvest green mold in citrus fruit was examined. CA strongly inhibited mycelial growth of both strains with minimum inhibitory concentration (MIC) of 0.3 mL L -1 and minimum fungicidal concentration (MFC) of 0.6 mL L -1 . In vivo assays revealed that wax + CA (WCA, 10 × MFC) treatment could significantly reduce green mold incidence in Ponkan fruit incubated with P. digitatum . After 5 d of incubation, the disease incidence of 10 × MFC WCA treated fruit was 65.0 ± 3.4 % for Pds01 and 50.0 ± 2.1 % for Pdw03 which were much lower than the corresponding values in the control samples. The antifungal activity was attributed to activation of massive oxidative stress , as evidenced by the accumulation of reactive oxygen species, increased lipid peroxidation , damage to plasma membrane permeability of hyphal cells, leakage of intracellular components and eventual cell death. The imazalil-resistant strain was more susceptible to the damaging effect of CA than the wild type strain. Collectively, our present results suggest that CA may potentially be a new antifungal drug molecule for the control of postharvest green mold in citrus fruit.