Carbon isotope composition of sugars in grapevine, an integrated indicator of vineyard water status

Abstract

Photosynthetic carbon isotope composition ((δ13C) was measured on sugars in mature fruits from field-grown grapevines. Sugar δ13C and summer predawn leaf water potential were significantly correlated. The survey of different vineyards during four growing seasons showed that sugar δ13C in must at harvest varied from -20‰ to -26‰ when conditions during berry maturation varied from dry to wet. This range allows a very sensitive detection of grapevine water status under natural conditions. However, local differences due to soil capacity to supply water to grapevines are maintained, whatever the annual water balance. Leaf nitrogen content variations of field-grown grapevines did not change δ13C values. Genetic variability of δ13C between 31 grapevine varieties for δ13C was observed. Must sugar δ13C can be used to characterize vineyards for their soil structural capacity to provide water to grapevines. It was concluded that isotope carbon composition in grapevine measured on sugars at harvest can be applied to compare the capacities of vineyard soils and canopy management to induce mild water stress in order to produce premium wines.