Physiological, Biochemical, and Molecular Characterization of the Response of Potato Cultivar Astanalyk to Osmotic Stress

Climate change and the increasing frequency of extreme weather events highlight the need to investigate the mechanisms underlying potato tolerance to water deficit and osmotic stress. This study aimed to evaluate the physiological, biochemical, and molecular responses of potato cultivar Astanalyk to different osmotic agents. Plants were exposed to PEG-6000, sorbitol, and NaCl, after which chlorophyll and malondialdehyde (MDA) contents, catalase (CAT) activity, and the expression levels of the StuNAC, TRE, and OST2 genes were determined in leaves and roots. The stress response varied depending on the type of osmotic agent and tissue. A statistically significant decrease in chlorophyll content was observed only under 8% PEG-6000 treatment. Under this treatment, MDA content reached its maximum value of 12.08 nmol/g, which was 60% higher than the control. The most pronounced increase in CAT activity was observed under 75 mM NaCl treatment, reaching 46.9% above the control level. Treatment with 8% PEG-6000 induced the highest expression of StuNAC, TRE, and OST2, particularly in roots, where their expression levels increased 3.31-, 3.24-, and 2.89-fold, respectively. A strong positive correlation was observed between the expression levels of the investigated genes and CAT activity. These results demonstrate a differential and tissue-specific response of potato cultivar Astanalyk to different osmotic agents and may contribute to the comprehensive assessment of potato stress tolerance.