Abstract: A pathogenic fungal strain was isolated from naturally infected satsuma mandarin fruit. On the basis of morphological characteristics, rDNA-internal transcribed spacer (rDNA-ITS) sequence analysis and pathogenicity test, the pathogen was identified as Penicillium italicum. The in vitro test showed that the growth of Penicillium italicum was completely inhibited at a sophorolipid concentration of 0.1 g/L; in the fruit test, the smallest lesion diameter and the lowest incidence of blue mold were observed at a sophorolipid concentration of 35 g/L. Treatment with 35 g/L sophorolipid effectively enhanced disease resistance in inoculated satsuma mandarin fruit by increasing the activities of peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonialyase (PAL). Our experimental results offer a theoretical basis for the prevention and control of postharvest blue mold in satsuma mandarin fruit.

Key words: satsuma mandarin, Penicillium italicum, sophorolipid, induced disease resistance