Provenance-based responses of beneh (Pistacia atlantica subsp. kurdica) seedlings to drought stress: insights into morpho-physiological and molecular climate adaptation strategies

Key message

This study highlights significant drought tolerance variations among seedlings from different provenances of beneh in the Zagros forests, with dry–warm southern genotypes showing superior morphophysiological and molecular responses.

Abstract

Drought poses a significant threat to the growth and stability of forest ecosystems globally. Beneh (Pistacia atlantica subsp. kurdica), an important tree species in the Zagros forests of western and southern Iran, has been increasingly affected by drought in recent years. In this study, we assessed the morpho-physiological and gene expression responses of 14-month-old seedlings sourced from the climatic edges of the species' distribution in Zagros forests with the aim of provenance-specific recommendations to enhance afforestation success and promote adaptation to future challenges. Significant variation in drought tolerance was revealed among provenances. Temperate northern provenances exhibited a more pronounced decline in shoot and root growth (45–62%), accompanied by significant variations in carbon (C) and nitrogen (N) levels. The dry–warm southern provenances showed more growth suppression in shoots compared to roots. In addition, they exhibited significantly higher rates of photosynthesis (An), chlorophyll fluorescence (Fv/Fm), and intrinsic water use efficiency (iWUE). In drought, levels of malondialdehyde (MDA) and protective osmolytes, as well as the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) enzymes, increased in seedlings, with a more pronounced effect observed in drier provenances. The expression patterns of CTD, GST, MKK5, WRKY, CYP90, SDH, P5CS genes differed between temperate northern and dry–warm southern provenances, suggesting key roles in stress response pathways. In conclusion, the drier provenances exhibited enhanced drought tolerance, improved morphology and physiology, and distinct root gene expression patterns. This study enhances understanding of local adaptation of beneh trees to drought, crucial for climate change strategies and predicting drought impacts on beneh forests.