Assessment of tropospheric ozone phytotoxic effects on the grapevine (Vitis vinifera L.): A review

The grapevine (Vitis vinifera L.) is a crop with great cultural, economic and ecological relevance for Mediterranean environments besides being the fruit crop with largest acreage and economic value at the global scale. Its exposure to high levels of tropospheric ozone (O3) can result in phytotoxic effects and thus it is important to comprehensively re-evaluate these effects as well as related processes. A review of the validity and limitations of the standards used for the protection of vegetation in relation to ambient O3, the state-of the-art knowledge on O3 phytotoxic effects on the grapevine and the available means to assess its impact are presented and discussed. It is concluded that wide regions in the world, mainly between latitudes 30o and 50o N, where the grapevine has been traditionally cultivated, are exposed to O3 concentrations that can affect both the yield and quality of the grape. Recently reported studies for global cultivars such as Cabernet Sauvignon or Merlot, along publicly available maps on O3 standards to protect vegetation at the European and global scale, indicate potential yield reductions in the range of 20-31% and the quality of the grape can also be affected by reductions of total polyphenols in the range of 15-23% for these areas. Although a tendency to reduce ambient O3 levels has been registered since 2000 in the western European Mediterranean basin, the flux of O3 into the grapevine leaves could still exceed critical levels with phenological advancement driven by the increase of temperatures or interaction between O3 and other climatic variables such as drought or high summer light intensities. Higher O3 exposures are reported in western United States of America and eastern China, with this last region maintaining an increasing tendency in summer ambient O3 levels. It is still necessary to adopt common experimental and monitoring protocols to establish grapevine-specific O3 relationships and critical levels, as there is not yet a coherent and shared database for detailed risk assessment for this crop.