Study On Ascorbic Acid Metabolism Of Actinidia Eriantha Cv.’White’ During Storage

Ascorbic acid(AsA)is a vital antioxidant compound,which plays an important role in human health.Cultivar of Actinidia eriantha cv.’White’can constantly maintain higher AsA level as compared to the other cultivars of kiwifruit after harvest.In this paper,’White’ fruit was carried out as test materials,and some main changes in terms of quality of’White’ were studied during storage at 20℃.In order to understand the AsA metabolism in harvested ’White’ fruit,the changes of AsA content,the related substances,the activities of enzymes and relative expression of genes involved in AsA metabolism of ’White’ were also investigated during storage at 20℃,respectively.The main results were as follows:1.The contents of soluble solids and titratable acid were not reduced in ’White’ after 21 days in storage;the fruit maintained good taste and strong storage tolerance.The chlorophyll content increased in the whole storage and malondialdehyde content increased at the early period of storage and then decreased gradually,and weightlessness rate was not more than 10%after storage.Thus,the fruit had high nutritional value and antioxidant capacity.2.AsA content in ’White’ increased at the early period of storage and then slightly decreased,which attributed to AsA biosynthesis and regeneration.L-galactose pathway as the priority to biosynthesis of AsA supplemented by D-galacturonic acid pathway might collectively contribute to AsA accumulation in fruits during storage.In L-galactose synthesis pathway,L-galactose dehydrogenase(GalDH)might be the limited enzyme.The oxidation of AsA was mainly affected by ascorbate oxidase(AO)activity,and dehydroascorbate reductase(DHAR)might be the main enzyme that regenerated AsA from dehydroascorbate(DHA).3.Relative expressions of 11 genes involved in AsA metabolism of’White’,including 7 synthetase genes,2 oxidase genes and 2 regeneration enyme genes,were investigated.The results also showed that the AsA accumulation resulted from the combination of AsA biosynthesis and regeneration.Genes of GDP-D-mannose pyrophosphorylase(GMP),L-galactose-1-phosphate phosphatase(GPP)and GalDH might have control roles in AsA biosynthesis of Actinidia eriantha cv.’White’,but GDP-mannose-3’,5’-epimerase(GME),GDP-L-galactose phosphorylase(GGP),L-galactono-1,4-lactone dehydrogenase(GalLDH)and D-galacturonic acid reductase(GalUR)did not play control roles in regulating on AsA accumulation.AO was the main gene of AsA oxidation.DHAR was the main gene of AsA regeneration.