Ultraviolet-B alleviates the uncoupling effect of elevated CO2and increased temperature on grape berry (Vitis viniferacv. Tempranillo) anthocyanin and sugar accumulation

Abstract

Background and Aims Atmospheric carbon dioxide (CO2) levels and temperature are expected to increase in the next decades. In addition, changes in climate as well as the stratospheric ozone concentration may affect the exposure of viticultural regions to UV-B. The aim of the present study was to investigate the effect of combined elevated CO2 and increased temperature (+CO2/+T) regimes and UV-B radiation on anthocyanin and flavonol biosynthesis in grape berries. Methods and Results Three UV-B doses [0, 5.98 and 9.66 kJ/(m2·d)] and two CO2–day/night temperature regimes (390 μmol/mol CO2–24/14°C and 700 μmol/mol CO2–28/18°C) were imposed on Vitis vinifera cv. Tempranillo fruit-bearing cuttings from fruitset to maturity. Berry mass, composition and expression of selected genes were monitored. The time to reach veraison and maturity was reduced under +CO2/+T. Anthocyanin concentration under +CO2/+T was higher 2 weeks after veraison, but lower at maturity. Ultraviolet-B radiation slowed berry development and upregulated flavonol and anthocyanin biosynthesis. Conclusions The effect of UV-B, which modulates the accumulation of sugars and upregulates anthocyanin biosynthesis, compensated the deleterious effect of elevated CO2 and increased temperature on berry anthocyanin concentration. Significance of the Study Certain viticultural practices, such as leaf removal, that modify the exposure of grapes to UV-B and the leaf surface to fruit mass ratio, may alleviate the effect of elevated CO2 and increased temperature on grape anthocyanin concentration.