Drought tolerance assessment and differentiation of grapevine cultivars using physiological metrics: insights from field studies

This study aimed to validate a protocol and compare metrics for evaluating drought tolerance in two Vitis vinifera grapevine cultivars under field conditions. Various metrics were calculated to represent the physiological responses of plants to progressive water deficit. Data were collected from Sauvignon Blanc and Chardonnay plants subjected to three irrigation levels during the 2022-2023 season, along with data from three previous seasons. Hydro-escape areas were used to assess the plant’s ability to reduce water potential with decreasing soil water availability. Sigmoid curves were employed to model the impact of water potential on stomatal conductance (gs) and embolism in shoots. These curves determined the water potential at which gs decreased by 50% () and the water potential at which air extraction from shoots increased by 50% (). Pressure-volume curves estimated the water potential at which leaf turgor loss occurred ().

Additionally, sigmoid curves described the effect of decreased water potential on yield per plant. Results showed that Chardonnay exhibited earlier reduction in gs under moderate water stress compared to Sauvignon blanc, with the latter demonstrating greater water stress tolerance (). S. Blanc maintained higher gs and gas exchange under limited water availability, enabling a 50% reduction in yield per plant () even under low water availability conditions. In contrast, Chardonnay experienced cellular turgor loss () and impaired water conduction in shoots () at lower water availability than S. Blanc, potentially due to a larger hydro-escape area. Overall, cultivars’ capacity to sustain yield per plant under moderate water deficit conditions () was identified as a differentiating metric for cultivars. However, considering the cultivar’s potential yield is crucial to determine the economic viability of partial yield maintenance under a water deficit.

Acknowledgements: Fruit tree physiology Laboratory, ANID Human Capital program.

References:

1. Henry, C., John, G. P., Pan, R., Bartlett, M. K., Fletcher, L. R., Scoffoni, C., & Sack, L. (2019). A stomatal safety-efficiency trade-off constrains responses to leaf dehydration. Nature Communications, 10(1). https://doi.org/10.1038/s41467-019-11006-1
2. Gambetta, G. A., Herrera, J. C., Dayer, S., Feng, Q., Hochberg, U., & Castellarin, S. D. (2020). The physiology of drought stress in grapevine: Towards an integrative definition of drought tolerance. Journal of Experimental Botany, 71(16), 4658–4676. https://doi.org/10.1093/jxb/eraa245

Fig. 1 Hydroscape area                                                                                  

Fig. 2 Metrics representing response to drought