Evaluation of some physiological responses to drought stress in grafted and ungrafted almond rootstocks

The effect of drought stress were studied on some physiological aspects of five grafted and ungrafted rootstocks including GF677, Garnem, peach seedlings, almond seedlings and a selected local almond ×peach  hybrid (LAP), with Ferragnes cultivar as scion. Three different drought stress levels including moderate (Ψsoil= -0.9 Mpa) sever (Ψsoil= -1.5 Mpa) and a control (Ψsoil= -0.3 Mpa) were applied in a randomized complete block design as factorial with three replications in pot plants during four weeks. Physiological traits including chlorophyll (Chl) fluorescence indices, leaf relative water contents (RWC), membrane stability index (MSI), free proline and concentrations of leaf pigments were recorded.Results showed that photochemical efficiency of photosystem II (Fv/Fm), RWC, Chl a, Chl b and total Chl were reduced significantly under drought stress while minimum fluorescence (F0), MSI and Free proline were increased noticeably. Drought stress affected significantly on evaluated traits in ungrafted rootstocks compared to grafted ones. According to results, almond seedlings, GF677 and local LAP almost showed similar responses to drought stress and had more tolerance than Garnem rootstock. Peach seedlings were affected significantly by drought stress more than the other rootstocks. Present study suggests chlorophyll fluorescence index as a simple trait for evaluation of almond rootstocks exposed to sever drought stress.