Response of Grape Rootstocks to Soil Moisture Stress

Studies on root and shoot morphology, endogenous hormones and water use efficiency in five grape rootstocks namely Dogridge, 1613 C, Salt Creek, St. George and Vitis champinii clone (VC Clone) at three levels of moisture stress viz., no stress (100% irrigation), 50% stress (50% irrigation) and 100% stress (without irrigation) for 14 days revealed that Dogridge and Salt Creek rootstocks maintained the highest ratios of root to shoot length and root to shoot dry weight as compared to other rootstocks. Water use efficiency increased with increased soil moisture stress and was the highest in Dogridge and Salt Creek. The abscisic acid content in the leaves of Dogridge was maximum at 50% stress followed by that of Salt Creek. Similarly the cytokinin content (both t-ZR and DHZR) was minimum in Dogridge and Salt Creek at 50% stress while it was maximum in 1613 C and St.George. The root to shoot length ratio was positively correlated with ABA content under moisture stress conditions. The higher levels of abscisic acid content in Dogridge and Salt Creek under soil moisture stress suggested their better drought tolerance capacity through a reduction of stomatal conductance and increased water use efficiency.