Differences among grapevine cultivars in their stomatal behavior and water use efficiency under progressive water stress

Evaluation of different mechanisms adopted by grapevine cultivars to deal with drought is of major importance to carry out more efficient cultivar selection. In this report, 23 cultivars, including local and foreign grape cultivars, were studied under field conditions in order to identify the different behaviors in response to water deficit, and how it can affect water use efficiency (WUE) at leaf level (intrinsic water use efficiency (WUEi) and leaf carbon isotope composition (δ13C)). Ψstem was used to assess plant water status. Under a common environment, a high variability was found in photosynthetic parameters, stomatal response, WUEi and leaf δ13C. This large variability observed represents an opportunity for genotype selection. Using different physiological traits we were able to select suitable cultivars for current and future viticulture. Under non-water stress situation the cultivar Escursac combined high rates of net photosynthesis with low stomatal conductance, resulting in high WUEi. In response to drought, strong, and moderate water saving behavior of local cultivars Manto Negro, Giró Ros, Argamussa and Vinater Negre resulted in higher WUEi. Long-term WUE (leaf δ13C) corroborate these cultivars as high water use efficient.