The effects of proline applications on shoot and root development of SO4 vine rootstock growing under salt stress conditions In Vitro

Salinity is a significant issue that leads to the reduction of agricultural land and renders soils unusable. This study aimed to determine the effects of different proline doses on shoot and root development of SO4 grapevine rootstock plantlets under salt stress conditions induced by varying sodium chloride (NaCl) concentrations in vitro. Micro-cuttings derived from SO4 rootstock were cultured for four weeks in MS medium containing 1 mg L⁻¹ BAP to induce shoot formation. The developed shoots were then transferred to MS medium supplemented with 1 mg L⁻¹ IBA for rooting. Explants measuring 2 cm in length and bearing three leaves, derived from rooted plantlets, were cultured in MS medium supplemented with 1 mg L⁻¹ IBA, in combination with 0, 1.0, 1.2, and 1.4 g L⁻¹ NaCl, as well as 0, 1, 2, and 4 mM proline. The results indicated that the combination of 1.2 g L⁻¹ NaCl and 1 mM proline was more effective compared to other treatments. Although differences between salt concentrations were not pronounced, increasing NaCl doses exhibited toxic effects, causing growth retardation in the plantlets. Lower proline doses demonstrated ameliorative effects under low salt stress, while higher doses were found to have toxic effects. Specifically, a proline concentration of 1 mM mitigated the adverse effects of salt stress and enhanced nutrient uptake. The findings revealed that exogenous proline supplementation in specific amounts to the culture medium under in vitro conditions has a protective and tolerance-enhancing effect against salt stress in plants. To generalize the ameliorative effects of proline against salt stress, further long-term studies involving different grapevine rootstocks and grape varieties under both in vitro and in vivo conditions are recommended. Keywords: Grapevine, tissue culture, micro cutting, mineral elements, shoot and root tolerance