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

Abstract

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.