The effect of bagging on ascorbate in Pyrus fruit

Abstract

ABSTRACTHere, the L-ascorbic acid (AsA) content as well as activities of enzymes and genes in AsA biosynthesis were investigated in bagged and unbagged fruit of Pyrus pyrifolia ‘Cuiguan’ during on-tree development. The contents of AsA/dehydroascorbate (DHA) and glutathione (γ-glutamyl-L-cysteinylglycine, GSH)/oxidised glutathione (GSSG) couples, the enzyme activities of L-galactono-1,4-lactone dehydrogenase (GLDH; EC 1.3.2.3), L-galactose dehydrogenase (GalDH; EC 1.1.1.117), ascorbate peroxidase (APX; EC 1.11.1.11), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), glutathione-dependent dehydroascorbate reductase (DHAR; EC 1.8.5.1) and glutathione reductase (GR; EC 1.6.4.2), and the relative expression levels of GLDH and DHAR genes were highest at 20 days after full bloom (DAFB) and then decreased to their minimum at harvest. When the fruit were grown in the dark induced by bagging, the ascorbate contents, enzyme activities and gene expression amounts had a statistical decline compared to the control in the most sampling dates. However, although L-AsA metabolism was affected and the use of light transmitting fruit bags may be preferable, the drop in vitamin C was not really significant in a dietary sense.