Abstract: This study was undertaken in order to investigate the biocontrol effect of the ethyl acetate extract of the fermentation broth of Gymnopus sp. 0612-9 (GSFE) on blue and green molds in ‘Nanfeng’ citrus and to evaluate the efficacy in inducing disease resistance. Citrus fruit were pre-treated with different concentrations (0, 0.25, 0.55 and 5.50 mg/mL) of GSFE, and then artificially wounded and inoculated with spore suspensions of blue and green molds. Subsequently, the infection rate was quantified and changes in peel defense enzyme activities were measured regularly. The results indicated that the infection rate and disease index were both significantly reduced by GSFE treatment at all concentrations tested when compared with the control group, being the most effective at a concentration of 5.50 mg/mL. Moreover, the activities of phenylalanine ammonialyase, superoxide dismutase, peroxidase were enhanced remarkably by GSFE treatment. GSFE increased significantly the contents of total phenolics and total flavonoids, decreased the accumulation of malondialdehyde (MDA) and lipoxygenase (LOX) activity, and reduced membrane lipid peroxidation, thereby improving disease resistance. This study provides an idea for the development of GSFE as a postharvest citrus preservative.

Key words: extract of the fermentation broth of Gymnopus sp. 0612-9; induction of disease resistance; Penicillium italicum; Penicillium digitatum; biocontrol