Possible fungicidal effect of citral on kiwifruit pathogens and their mechanisms of actions

The current study was conducted to evaluate the inhibitory effects of citral against various fungal pathogens viz: Botryosphaeria dothidea, Phomopsis macrospore, and Botrytis cinerea. The present study aimed to describe the antifungal mechanism of citral against B. dothidea, which is not fully elucidated yet. According to the results, citral showed potent inhibition on the hyphal growth of the three studied fungi with a minimum inhibitory concentration of 0.4 μL/mL. Citral changed the morphological characteristics of fungal hyphae of B. dothidea by resulting in the loss of cellular content and distortion of mycelia. Membrane permeability was increased by citral, as evidenced by increases in extracellular electrical conductivity and optical density (OD260) and a decrease in soluble protein content in B. dothidea. A decline in the range of ergosterol levels proved that citral impaired the physiology of the cell membrane. Furthermore, the higher citral concentrations decrease the level of respiration-associated enzymes resulting in the disruption of energy metabolism. Importantly, citral also showed positive effects on fruit quality and reduced the decay rate of kiwifruit. These findings suggest that the antifungal activity of citral could be attributed to the increase in membrane permeability and the damage in the cell membrane. Citral can potentially be used as an alternative for kiwifruit storage.