Effect of irrigation and variety on oxygen (δ18O) and carbon (δ13C) stable isotope composition of grapes cultivated in a warm climate

Abstract

Background and Aims: δ13C values from Vitis vinifera leaves, whole grape, seed, pulp, skin and/or grape must sugars have been investigated as an integrated marker of vine water status or intrinsic water-use efficiency during berry growth and across region of origin, vintage and variety. The use of 18O/16O isotopic ratio as a marker of water addition, vintage and geographical origin has also been studied. This paper examines the effect of irrigation and grapevine variety on δ18O and δ13C of grape must from eight varieties, all cultivated in the same vineyard to reduce the effects from other variables. Methods and Results: Stable isotope compositions of grape must water and sugar were determined by isotope ratio mass spectrometry. The result of the study showed statistically significant effects of irrigation and vine variety on both δ18O and δ13C. The effect of vintage on δ18O was only significant for non-irrigated vines. Conclusion: This research highlights the effect of variety and irrigation on δ13C and δ18O of grape. Significance of the Study: This is the first report to demonstrate that the varietal effect on δ13C and δ18O of grape is not due only to differences in the vegetative cycle of each variety. It further suggests that water exhibits a lower isotopic discrimination in the indigenous Spanish varieties studied than in non-indigenous varieties. © 2009 Australian Society of Viticulture and Oenology Inc.