Inhibitory Mechanisms of trans-2-Hexenal on the Growth of Geotrichum citri-aurantii

Geotrichum citri-aurantii(G. citri-aurantii) is one of the most important postharvest pathogens leading to a postharvest loss of citrus by causing sour rot. In this study, the antifungal activity oftrans-2-hexenal, a natural component of essential oil, againstG. citri-aurantiiwas evaluated.Trans-2-hexenal treatment inhibited the mycelia growth ofG. citri-aurantiiwith a minimum inhibitory concentration and minimum fungicidal concentration oftrans-2-hexenal at 0.50 and 1.00 μL/mL, respectively. Moreover,trans-2-hexenal efficiently reduced the incidence of sour rot of Satsuma fruit inoculated withG. citri-aurantii. Ultrastructural observations and Fourier transform infrared (FT−IR) results showed thattrans-2-hexenal treatment affected the cell wall and cell membrane instructions ofG. citri-aurantii. The content ofβ-1,3-glucan was significantly decreased aftertrans-2-hexenal treatment, but the cell wall permeability was not changed. The decrease in lipid and ergosterol contents might be responsible for this antifungal activity. Several important genes,FKS1,ERG1,ERG7, andERG11, showed decreasing expression levels aftertrans-2-hexenal treatment. Molecule-docking results also indicated thattrans-2-hexenal could join with the protein of FKS1, ERG1, ERG7, and ERG11 to impact enzyme activities. These results demonstrated thattrans-2-hexenal is a promising fungicide for controlling sour rot of harvested citrus fruit by damaging the membrane integrity ofG. citri-aurantii.Keywords:G. citri-aurantii;trans-2-hexeanl;antifungal mechanism;cell wall;cell membrane