The effect of different periods of water restriction on the concentration of phenolic compounds and some of the phenolic acids of two grapevine cultivars

This research was carried out with the aim of investigating and comparing changes in the concentration of phenolic compounds and some of the phenolic acids, in two grapevine cultivars, differing in drought tolerance, to different levels of water restriction. For this purpose, a factorial experiment was conducted in a completely randomized design with six replications in greenhouse conditions. Drought stress was performed in the summer by the method of cut off irrigation in four levels of 0 (control), 6, 12 and 18 days on the potted seedlings of the two Yaghuti and Bidanesefid cultivars. Total phenolic compounds were measured by reaction with Folin-Ciocalteu reagent, and phenolic acids were quantified by HPLC method. Based on the results of this research, in 6 dws plants of both cultivars, no significant change was observed in the content of total phenolics compared to respective control vines, but two other stress levels caused a significant increase in the content of phenolic compounds of both cultivars. Six phenolic acids, including ferulic acid, p-coumaric acid, Gallic acid, chlorogenic acid, caffeic acid, and resveratrol, were identified by quantitative estimation of phenolic acids in the leaves of two cultivars. Depending on the duration of the stress and the cultivar, each of the measured phenolic acids showed a different reaction, but, generally, the concentration of most detected phenolic acids increased under the influence of different periods of drought stress. Among these compounds, gallic acid had the highest, and chlorogenic acid had the lowest concentration in leaves of control, and stress samples in both cultivars. These results indicate that identified phenolic acids play a key role in protecting grapevine cultivars in drought stress conditions.