Hydraulic conductance as an indicator of vascular connection quality in grapevine grafts

Abstract

Grapevine grafting is a major technique for propagation in viticulture, and its success relies on the formation of continuous and functional vascular connections between scion and rootstock. In commercial grapevine nurseries, the quality of grafted plants is commonly assessed through external visual inspection, which evaluates mechanical stability but provides limited information on the internal reconnection between scion and rootstock. As most structural differences at the graft interface are internal, visual inspection is often unable to identify discontinuities or incomplete vascular reconnection that could limit plant performance. Two- and three-dimensional anatomical studies have provided valuable insights into graft formation and vascular continuity (Battiston et al., 2022; Camboué et al., 2025). While these techniques are costly, require specialised equipment, and are not feasible for large-scale assessment, practical measurements based on water flow could represent a complementary and scalable approach to evaluate graft union quality under nursery conditions.

Therefore, present study evaluated hydraulic conductance as an indicator of vascular connection efficiency in Vitis vinifera L. cv. Tempranillo (clone VN69) grafted onto 110 Richter (V. berlandieri × V. rupestris). Four bench grafting methods were compared: omega with completely aligned cambium (OM-CA), omega with partially aligned cambium (OM-PA), hand-made whip and tongue (WTh), and V-shape (V). Grafted plants were grown in pots for one year under controlled conditions. Hydraulic conductance (K; g‧s^-1‧MPa^-1) was gravimetrically determined following the method described in Torres-Ruiz et al. (2012).

Hydraulic conductance varied among grafting methods, reflecting differences in the efficiency of vascular reconnection. OM-CA grafts exhibited the highest and most uniform conductance values, whereas OM-PA and WTh were intermediate, and V grafts displayed lower conductance and greater variability. These results indicated that omega grafts, often criticised by practitioners, achieved equal or even superior functional performance compared with alternative methods under nursery conditions. Moreover, the plants that externally appeared well joined sometimes displayed low hydraulic conductance, confirming that visual inspection alone could not accurately predict graft functionality.

In conclusion, hydraulic conductance measurement seems to be a quantitative, valuable and cost-effective method to evaluate graft union quality. This approach could complement imaging and anatomical analyses and could be implemented in nursery trials to help determine whether early anatomical traits at the graft union are predictive of plant performance.

References

Battiston, E., Falsini, S., Giovannelli, A., Schiff, S., Tani, C., Panaiia, R., Papini, A., Di Marco, S., & Mugnai, L. (2022). Xylem anatomy and hydraulic traits in Vitis grafted cuttings in view of their impact on the young grapevine decline. Frontiers in Plant Science, 13. https://doi.org/10.3389/fpls.2022.1006835

Camboué, M., Janoueix, A., Spilmont, A.-S., Mathieu, G., Ollat, N., Santesteban, L. G., & Cookson, S. (2025). Visualising xylem vessels connections formed one year after grafting using different techniques. OENO One, 59(3), Article 3. https://doi.org/10.20870/oeno-one.2025.59.3.9148

Torres-Ruiz, J. M., Sperry, J. S., & Fernández, J. E. (2012). Improving xylem hydraulic conductivity measurements by correcting the error caused by passive water uptake. Physiologia Plantarum, 146(2), 129–135. https://doi.org/10.1111/j.1399-3054.2012.01619.x