Abstract:

The present work was conducted to investigate the effects of treatment with Ginkgo biloba L. leaf extract (EGb)
on disease resistance against Penicillum expansum infection and the possible mechanisms involved. The kiwifruit were
treated with EGbs containing 0.25, 0.50 and 0.75 mg/mL flavonoids and distilled water (control) after harvest, respectively.
Twenty-four hours after the treatment with EGb, the fruit were inoculated with 20 μL of conidial suspension of Penicillium
expansum (1 × 104 spores/mL) and incubated at 23 ℃ and 85%–90% relative humidity (RH) for disease development. In
addition, to investigate the resistance mechanism against Penicillum expansum infection, kiwifruit with four treatments
namely EGb, P. expansum, EGb + P. expansum and control were tested. Results showed that disease incidence and lesion
diameter in kiwifruit after the inoculation were significantly (P < 0.05) reduced by 0.50 mg/mL EGb during the incubation.
Moreover, the activities of polyphenol oxidase, peroxidase, phenylalnine ammonialyase, chitinase and β-1,3-glucanase as
well as the content of total phenolics and flavonoids were markedly and/or promptly enhanced in the EGb + P. expansum
treatment compared with those treated with EGb or inoculated with pathogen alone. Besides, the content of MDA was
decreased by EGb treatment. Its mechanisms may be closely correlated with the induction of fruit resistance by priming
activation upon challenge with pathogen. These results suggest that the efficacy of EGb at 0.50 mg/mL on controlling blue
mold decay in kiwifruit may be related to the priming of defense responses.

Key words: ‘Qinmei&rsquo, kiwifruit, Penicillum expansum, Ginkgo biloba L. leaf extract (EGb), induced resistance