Analyzing Drought Resistance of two Contrasting Pistachio Hybrid Rootstocks using Key Stress Tolerance Indices

Root morphological and growth responses of two contrasting nine-month saplings of Pistacia atlantica × Pistacia integerrima hybrids, 'C۸-۳' (sensitive) and 'C۹-۴' (resistant), were assessed following ۳۰-day period of water withholding. The assessment focused on several traits, including the drought susceptibility index (DSI), stress tolerance index (STI), root-to-shoot ratio, network volume (NWVL), network area (NWCA), and root redox potential. Our findings indicated that neither STI nor DSI based on root biomass effectively distinguished between high-yield clones under both stress and non-stress conditions. Interestingly, the root-to-shoot ratio, which is often elevated in drought-resistant species, did not exhibit a significant increase in the resistant clone. Additionally, water stress negatively affected root architecture traits, leading to reduced NWVL and NWCA in the resistant clone. Measurements of root redox potential revealed elevated values in the sensitive clone under drought conditions. Overall, among the traits evaluated, NWCA, NWVL, and root redox potential were particularly effective in differentiating clones with high yields in both stressful and non-stressful environments. These results enhance our understanding of the drought tolerance mechanisms in pistachio hybrids and underscore the significance of selecting suitable rootstocks for areas facing water scarcity.

Keywords:

Clonal hybrid , DSI , Redox , STI , Water withholding