In vitro regeneration of Gerbera jamesonii under mannitol-induced osmotic stress using plant growth regulators

Abstract

Gerbera is a commercially important ornamental species that is highly susceptible to drought stress, which can significantly limit growth and productivity under adverse environmental conditions. This study aimed to evaluate the effects of osmotic stress on in vitro regeneration and to optimize plant growth regulator combinations for improving regeneration under drought-simulated conditions. Osmotic stress was induced by supplementing Murashige and Skoog medium with mannitol at concentrations of 10-50 g L-1, and plant growth responses were evaluated. The results indicated that increasing mannitol levels progressively inhibited growth, with 40 g L-1 causing marked reductions in plant height, leaf number, leaf area, and fresh weight. To alleviate these effects, different cytokinins and auxins were applied. Among cytokinin treatments, 0.5 mg L-1 benzyladenine significantly enhanced shoot proliferation, producing more than 13 shoots per explant. In addition, all auxin treatments resulted in 100% rooting efficiency and significantly improved root number and length. These findings demonstrate that appropriate combinations of plant growth regulators can effectively mitigate drought-induced inhibition and promote regeneration under osmotic stress. The optimized regeneration protocol provides a foundation for future in vitro selection and the subsequent development of drought-tolerant gerbera genotypes.