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Gas exchange and water-use efficiency of cv. Sangiovese grafted to rootstocks of varying water-deficit tolerance

Galbignani, M., Merli, M. C., Magnanini, E., Bernizzoni, F., Talaverano, I., Gatti, M., Tombesi, S., Palliotti, A., Poni, S.
Irrigation science 2016 v.34 no.2 pp. 105-116
Vitis, canopy, carbon dioxide, drought, drought tolerance, gas exchange, genotype, global warming, irrigation, leaf area, leaf water potential, problem solving, rootstocks, summer, transpiration, water stress, water supply, water use efficiency
Testing of new rootstocks for drought tolerance targets traditionally rain-fed districts where supplemental irrigation is more frequently needed due to the pressures of global warming. A seasonal evaluation of gas exchange and water-use efficiency (WUE) of cv. Sangiovese grafted to the new drought-tolerant genotype M4 in a dry-down trial against the commercial SO4 stock is reported. The experiment was conducted in 2014 on twelve 2-year-old, non-fruiting potted Sangiovese grapevines grafted on M4 and SO4 stocks and assigned to SO4-WW (well-watered), SO4-WS (water-stressed), M4-WW and M4-WS treatments. Progressive water deficit was imposed by reducing water supply to 70, 50 and 30 % of whole-canopy demand derived from concurrent measurements of transpiration in WW. Unlike SO4, M4 showed slower stress progression, as highlighted by pre-dawn leaf water potential, and retained higher whole-canopy net CO₂ exchange rates (NCER) and transpiration rates per unit of leaf area at all replenishment levels as well as exhibiting higher canopy WUE at both 50 and 30 % WW. Although single-leaf assessment was in partial disagreement with data recorded on the whole-canopy basis, robust data were acquired to confirm that the M4 stock performs better than SO4 at any water replenishment level in terms of higher NCER/leaf area and/or canopy WUE. Findings feed expectations that grafting Sangiovese to the M4 rootstock should result in a problem-solving tool for rain-fed areas subject to temporary summer drought.