Effects Of Postharvest Melatonin Treatment On Blue Mould And Storage Quality Of Jujube Fruit

Jujube is rich in vitamin C(also known as ascorbic acid),which is a good source of ascorbic acid of human body,but does not bear storing.In this paper,jujube fruit(cv.Sanxing)was used as the material to study the inhibitory effect of melatonin on the growth of Penicillium polonicum in vitro and the effect of postharvest melatonin treatment on its quality,ascorbate-glutathione cycle,fruit softening and blue mould.The main results are as following:1.Melatonin inhibited mycelia growth and spore germination of Penicillium polonicum in vitro,and inhibited the lesion development of jujube fruit inoculated with P.polonicum.The optimal concentration of melatonin for controlling blue mould of jujube fruit is 25 ?mol/L.2.The results showed that melatonin treatment had no significant effect on the weight loss of the fruit,but inhibited the respiratory rate and ethylene production of jujube fruit.Melatonin treatment also refined the color,delayed softening of the fruit and maintained the content of titratable acid.3.Melatonin treatment enhanced the activity of ascorbate peroxidase(APX),glutathione reductase(GR)and monodehydroascorbate reductase(MDHAR)in jujube fruits,and increased the content of ascorbic acid(AsA),dehydroascorbic acid(DHA)and reduced glutathione(GSH).4.Melatonin treatment inhibited the activity of pectin methyl esterase(PME),polygalacturonase(PG),cellulase(Cx)and ?-glucosidase(?-glu)related to fruit softening and delayed the production of soluble pectin while maintaining the content ofthe protopectin.Therefore,Melatonin treatment maintained the hardness of the fruit.Taken together,all these results suggest that melatonin treatment could inhibit the growth of P.polonicum,and maintain the fruit quality,delay the fruit softening,improve the antioxidant capacity of the fruit,and thus delay fruit senescence and prolong the storage period of jujube fruit.