Ascorbic Acid Derivatives in the Sauvignon Blanc Cultivar (Vitis vinifera L.) During Berry Development in the Wellington and Elgin Regions

Abstract

The exposure of grapevines to unfavourable conditions such as drought, high or low temperature andpathogenic attack increases the production of reactive oxygen species, thus inducing oxidative stress.One of the most important non-enzymatic antioxidants is ascorbic acid, which is used by plants toprotect themselves against these toxic oxygen intermediates. DHA, DKG and threonate are ascorbic acidmetabolites that are found during ascorbic acid catabolism. This study was done in two regions, the onein Wellington, classified as a warmer climate, and the other in Elgin, classified as a cooler climate. Ineach region, two Sauvignon blanc vineyard blocks were selected, with north to south and east to west rowdirections. Vines were monitored during the growing season to investigate the trends in the development ofascorbic acid metabolites in both regions. Canopy management practices were done at different ripeningstages. Grape berries were sampled at different phenological stages according to the Eichhorn Lorenzscale: E-L 32, E-L 34, E-L 35, E-L 37 and E-L 38. Ascorbic acid derivative concentrations in the two regionsvaried significantly in that Elgin showed higher concentrations than Wellington at E-L 32 and E-L 38. Boththe cool and warm regions had high concentrations of threonate, with no significant difference amongstages of ripeness. The DHA, DKG and threonate levels were the highest at the E-L 32 phenological stagefor both regions, with no significant differences among the other phenological stages, especially for DHAderivative concentrations. No significant effect on the DHA, DKG and threonate levels of the grapes wasobserved between row directions in each region.