Effects of Drought Stress Levels on Some Morphological and Physiological Traits to Select The Most Tolerant ones as a Rootstock

One of the major limiting factors of agricultural production in the world is considered to be drought which is a function of Genotype, temperature, rain and water storage capacity of soil. Grape is one of the most important horticultural product in Iran and many other countries and drought stress is the most crucial growth limiting factor in Mediterranean regions. Enforcing drought stress treatments in lab work and selecting cultivars based on stress conditions is one of the methods to select drought tolerant cultivars which has been suggested by others. This project has been conducted in order to compare tolerant cultivars which were already introduced by others to introduce the most tolerant ones.

This research carried out with15 drought stress treatments including four ungrafted grapevine cultivars (Samarghandi, Yaghuti, Rotabi and Chafteh) and 110R rootstock (V. berlandieri x V. rupestris) and three water stress treatments; control (no stress),severe (-2 MPa) and high severe (-2.5 MPa) with three replications as factorial based on randomized block design. Each experiment contained a two-year-old potted grape plant. The measured traits included morphological traits (number of healthy leaves, main and minor branches length, wet and dry weight of root and crown) and physiological traits (total Chlorophyll, ion leakage, relative water content of leaf, Malondialdehyde, soluble sugars, phenol, Glycinbetain and Proline contents).

Most of morphological traits, related to external growth of grape (leaf area, leaf number, root length and wet and dry weight of shoot and root) reduced by increasing the severity of drought stress. In comparison with control (no stress) some of the physiological traits (phenol, chlorophyll a and b and relative water content of leaf) decreased; however the ionic leakage, soluble sugar, proline and Glycinbetain increased in severe and high severe stress conditions. Results of analysis of variance showed that the effect of drought stress had significant effect on all measured traits except the dry weight of root and shoot and malondialehyde levels in rootstock and tolerant cultivars.

Comparison between average of morphological and physiological traits after standardizing showed that Chafte cultivar has been the most tolerant cultivar in high severe stress conditions in comparison with rootstock and other cultivars. Rotabi, Samarghandi and Yaghouti cultivars were placed in order after Chafte, respectively.. The 110R rootstock was realized as the weakest one because of nonalignment between drought stress tolerance indices.