Determination of drought resistance of Trakya İlkeren and Black Magic grape varieties with PEG in vitro

Drought is a major environmental factor that significantly impacts agricultural production as well as the morphological, physiological, and biochemical characteristics of plants worldwide. This study investigated the effects of artificial drought stress, induced by varying concentrations of polyethylene glycol (PEG) 6000, on two grapevine varieties, Trakya İlkeren and Black Magic. At the onset of the study, single-node micro-cuttings from both grape varieties were cultured for 4–5 weeks in MS medium supplemented with 1 mg L⁻¹ benzylaminopurine (BAP). The resulting shoots were subsequently transferred to MS medium containing 1 mg L⁻¹ indole-3-butyric acid (IBA) and cultured for 4 weeks to induce rooting. Shoot tips approximately 2 cm in length from rooted plants were then used for drought stress treatments. These shoot tips were cultivated in MS media containing 1 mg L⁻¹ IBA and PEG 6000 at concentrations of 0%, 0.25%, 0.50%, 1.0%, 2.0%, 3.0%, and 4.0%. The results revealed significant differences between the control and PEG treatments in parameters such as plant height, number of nodes, fresh and dry weights of shoots and roots, root number, average root length, leaf relative water content, membrane permeability, SPAD index, plant damage rate, and tolerance indices for both shoots and roots. These findings indicate that Trakya İlkeren and Black Magic grape varieties exhibit high sensitivity to drought stress. In conclusion, future studies are recommended to explore the drought resistance of these grape varieties in greater detail by testing additional PEG concentrations and nutrient media.