Assessment of drought tolerance in peach × almond hybrids to identify promising rootstocks.

Drought is a major environmental stress severely restricting plant growth, development, and productivity in arid regions. In this research, seven interspecific peach × almond hybrids (‘GF677’, ‘GN15’, ‘GN2’, ‘TT’, ‘35.1’, ‘34.2’, and ‘50.10’) were evaluated for their drought stress tolerance to identify promising rootstocks. Drought stress treatments were applied at 40%, 60%, and 100% field capacity (FC). Following a two-month stress period, morphological, physiological, and biochemical traits, along with the concentrations of 10 elements in leaves and roots, were measured. Under severe drought stress, all rootstocks exhibited reductions in plant height, trunk diameter, new branch growth, root and shoot fresh and dry weights, and relative water content, with an increase in the number of necrotic and fallen leaves. Drought stress significantly impaired PSII efficiency. At 40% FC, rootstocks ‘TT’ (0.749) and ‘GF677’ (0.740) exhibited the highest QYmax, while rootstocks ‘50.10’ (0.650) and ‘34.2’ (0.688) had the lowest. Under 40% field capacity (FC) stress, protein content and the activities of APX and CAT decreased, while proline, antioxidant capacity, electrolyte leakage, and aldehyde levels increased. Under drought stress, ‘TT’ displayed higher leaf concentrations of N (2.08%), P (0.17%), Ca (1.45%), Mg (0.56%), Fe (184.71 mg kg−1), Cu (5.07 mg kg−1), and Zn (18.77 mg kg−1). In contrast, rootstock ‘50.10’ exhibited the highest concentrations of Cl (4.83%), P (0.24%), and Zn (18.85 mg kg−1) and the lowest concentrations of N, K, Ca, and Fe. Finally, this research introduces ‘TT’ rootstock as a promising drought-tolerant rootstock.