Improvements in blueberry micropropagation: Surface disinfection and pH dynamics depending on the gelling agent

In this study, the micropropagation of the Vaccinium corymbosum cultivars ‘Duke’ and ‘Liberty’ was optimized, and the gel and pH dynamics of agar- and gelrite-solidified media were characterized. Nodal segments were established in vitro using 10 g/l sodium dichloroisocyanurate (NaDCC) as a surface disinfectant, which maintained the physiological pH and simplified handling. In ‘Liberty’, propagation factors did not differ between co‑autoclaved zeatin and sterile‑filtered zeatin added after autoclaving, supporting a cost‑ and time‑saving co‑autoclaving option. Because blueberries prefer low pH, which impairs medium solidification, gel strength analysis revealed that 3.0 g/l gelrite provided gel characteristics comparable to those of 9.0 g/l plant agar, enabling direct comparison of the gelling agents. During 8 weeks of culture, the pH of the gelrite-solidified medium was more stable than that of the agar-solidified medium. While the numbers of large shoots (≥7 mm) differed only marginally, significantly fewer short shoots formed on the agar-solidified medium. In ‘Liberty’, 90% of the shoots rooted on gelrite-solidified media versus 70% on agar-solidified media; in ‘Duke’, gelrite yielded higher root numbers than agar did. These physico‑chemical data and procedural adjustments (NaDCC surface disinfection, zeatin co‑autoclaving and optimized gelrite concentration) offer practical improvements for commercial blueberry micropropagation. Significance of the study What is already known on this subject? Micropropagation is a well-established method for rapid clonal multiplication of Vaccinium corymbosum . Mostly, agar is used as a gelling agent, but low pH (optimal for blueberries) weakens agar gels. The gelling agent was shown to influence propagation and rooting in other crops. Additionally, the filter-sterilization of growth regulators such as zeatin and their addition after autoclaving causes labour, costs and the risk of contamination. What are the new findings? This study demonstrates for the first time in blueberry that sodium dichloroisocyanurate (NaDCC, 10 g/l) enables effective surface disinfection and is easy to use. Zeatin can be co-autoclaved without loss of biological activity, which saves time and costs. Gelrite at 3.0 g/l provides a gel strength comparable to that of 9.0 g/l plant agar, has better pH stability during culture passages and results in improved shoot development and higher rooting rates. What are the expected impacts on horticulture? The optimized protocol − featuring NaDCC disinfection, co-autoclaving of zeatin and gelrite as a gelling agent instead of plant agar − offers more consistent and efficient commercial micropropagation of high-value blueberry cultivars.