Effects Of The Extraction Of Ginkgo Biloba L. Leaves And Quercetin On Control Of Postharvest Blue Mould In Kiwifruit

The present work was conducted to investigate the effects of Ginkgo biloba L. leaf extract(EGb) or quercetin treatment on disease resistance against Penicillum expansum infection and the possible mechanisms involved in kiwifruit, as well as the preservation effects of quercetin. The main research results are as follows:1. Effect of EGb on induction of resistance to P.expansum in kiwifruitDisease incidence and lesion diameter in kiwifruit after inoculation were significantly(P< 0.05) reduced by 0.50 or 0.75 mg/m L EGb during the incubation. Moreover, the activities of polyphenol oxidase(PPO), peroxidase(POD), phenylalnine ammonialyase(PAL), chitinase(CHI) and β-1,3-glucanase(GLU) as well as the content of total phenolics and flavonoids were markedly and/or promptly enhanced in the EGb and then challenged with 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.2. Effect of quercetin on the growth of P.expansum in vitro.0.25~1.0 mg/m L of quercetin was significantly inhibited the P.expansum growth in vitro,the efficiency was might be closely associated with the conthentration of quercetin; 0.25mg/m L quercetin had a strong destroyed effect on mycelium cell wall and membrane of P.expansum, and led to the empty of whole cell because of the leakage of intracellular soluble substances. 0.50 mg/m L quercetin treatment led to a disorder of cell structure and empty of some cell.1.00 mg/m L of quercetin resulting in a smaller size of cell structureand empty of some cell.3. Effect of quercetin on resistance-related enzymes and genes expression in kiwifruitDisease incidence and lesion diameter in kiwifruit after inoculation were reduced by 0.10~0.50mg/m L quercetin during the incubation. With the 0.25 mg/m L quercetin treatment, the kiwifruit inoculated by P.expansum had a higher activity of chitinase(CHI),β-1,3-glucanase(GLU),phenylalnine ammonialyase(PAL), polyphenol oxidase(PPO),peroxidase(POD), or the expression of pathogenesis-related NPR1, PR1, CHI and GLU genes,compared with those kiwifruit only treated with quercetin or inoculated by P. expansum.These results suggest that the efficacy of quercetin on controlling blue mold decay in kiwifruit may be related to the priming of defense responses.4. Preservation effect of quercetin on kiwifruitQuercetin treatment could inhibit the decrease of firmness and slow down the increase of soluble solids content, reduced the respiratory intensity, ethylene release rate, increase the marketable fruits rate.This results indicate that quercetin had some preservation effect on kiwifruit during storage. Moreover, 0.50 mg/m L quercetin had a better effect on kiwifruit storage effect compared with 0.25 or 1.00 mg/m L quercetin.