The effect of various physio-biochemical parameters on the water use efficiency (WUE) of grape varieties, rootstocks and budded vines was studied in 3 separate experiments at 3 levels of irrigation (100%, 50% and no irrigation) for 14 days of stress cycle. None of the varieties or rootstocks could survive beyond 4 days under the no irrigation treatment. Considerable genetic variability was observed for WUE with respect to photosynthetic rate, transpiration rate, stomatal conductance, root to shoot length ratio, abscisic acid, zeatin riboside, carbon isotope discrimination etc. among grape rootstocks, viz., Dogridge, 1613 C, Salt Creek, St. George and Vitis champinii (VC) clone, and varieties, viz., Flame Seedless, Thompson Seedless, Sharad Seedless and Tas-A-Ganesh under 50% moisture stress. Among the rootstocks Dogridge was the most efficient water user, followed by Salt Creek and VC clone, while among the varieties Flame Seedless was the most efficient water user, followed by Thompson Seedless and Sharad Seedless at 50% moisture stress. Sharad Seedless on its own root, which was the least efficient water user under 50% soil moisture stress, increased its WUE when budded on efficient water using rootstocks like Dogridge and Salt Creek. A strong positive correlation was observed between WUE and photosynthetic rate, stomatal conductance, root to shoot length ratio and abscisic acid, while a negative correlation was observed with cytokinin and transpiration rate. The regression model revealed photosynthetic rate and transpiration rate as the major contributing factors for variation in WUE of rootstocks, varieties and budded grape vines under moisture stress conditions.

The effect of various physio-biochemical parameters on the water use efficiency (WUE) of grape varieties, rootstocks and budded vines was studied in 3 separate experiments at 3 levels of irrigation (100%, 50% and no irrigation) for 14 days of stress cycle. None of the varieties or rootstocks could survive beyond 4 days under the no irrigation treatment. Considerable genetic variability was observed for WUE with respect to photosynthetic rate, transpiration rate, stomatal conductance, root to shoot length ratio, abscisic acid, zeatin riboside, carbon isotope discrimination etc. among grape rootstocks, viz., Dogridge, 1613 C, Salt Creek, St. George and Vitis champinii (VC) clone, and varieties, viz., Flame Seedless, Thompson Seedless, Sharad Seedless and Tas-A-Ganesh under 50% moisture stress. Among the rootstocks Dogridge was the most efficient water user, followed by Salt Creek and VC clone, while among the varieties Flame Seedless was the most efficient water user, followed by Thompson Seedless and Sharad Seedless at 50% moisture stress. Sharad Seedless on its own root, which was the least efficient water user under 50% soil moisture stress, increased its WUE when budded on efficient water using rootstocks like Dogridge and Salt Creek. A strong positive correlation was observed between WUE and photosynthetic rate, stomatal conductance, root to shoot length ratio and abscisic acid, while a negative correlation was observed with cytokinin and transpiration rate. The regression model revealed photosynthetic rate and transpiration rate as the major contributing factors for variation in WUE of rootstocks, varieties and budded grape vines under moisture stress conditions.