Assessment of glucosinolate-derived isothiocyanates as potential natural antifungal compounds against citrus sour rot disease agent Geotrichum citri-aurantii

In this study, the antifungal effects of six different isothiocyanate (ITCs) compounds (methyl, allyl, butyl, ethyl, benzyl and 2-phenylethyl ITCs) were investigated to be use against the citrus sour rot disease caused by Geotrichum citri-aurantii in vitro and semi-commercial (in vivo) conditions. Antifungal activities of the vapour phases of different ITC compounds were examined on the arthroconidia germination and mycelial growth of G. citri-aurantii. Mycelial growth of G. citri-aurantii was inhibited in a concentration-dependent way. The minimum inhibitory concentrations of benzyl, methyl, allyl and ethyl ITCs on mycelial growth were 0.06, 0.08, 0.10 and 0.10 mu l/L, respectively. Arthroconidia germination of G. citri-aurantii was completely inhibited by benzyl, methyl, allyl and ethyl ITCs at concentrations of 0.05, 0.07, 0.07 and 0.07 mu l/L, respectively. Light microscopy observations revealed that the ITC compounds, at completely inhibiting concentrations, caused considerable morphological changes in the fungal hyphae. Under in vivo conditions, the average rotting area caused by G. citri-arantii was inhibited 100% by ethyl, methyl and allyl ITC compounds at concentrations of 8.0, 12.0 and 12.0 mu l/L, respectively. Results suggest that ITC's may be useful and effective natural antifungal compounds to control the citrus sour rot disease agent.