Establishment and Shoot Development Responses of Hylocereus undatus Under Plant Growth Regulator Treatments

Background/Objectives: Hylocereus undatus is a high-value crop whose conventional propagation is inefficient for commercial scaling. This study aimed to develop an optimized protocol for in vitro establishment and to define optimal plant growth regulator (PGR) formulations for shoot multiplication. Methods: methods involved testing six surface sterilization protocols using combinations of a surfactant, a systemic fungicide, ethanol, and sodium hypochlorite. Subsequently, nodal explants were cultured on Murashige and Skoog (MS) medium supplemented with ten different concentrations of benzylaminopurine (BAP) and indole-3-butyric acid (IBA), with morphogenic responses evaluated over 60 days. Results: We identified a sterilization treatment that achieved contamination-free cultures with high explant survival percentages. Shoot multiplication was strictly dependent on cytokinin supplementation, with the highest BAP concentration inducing maximal shoot proliferation, while lower concentrations favored shoot elongation. The inclusion of IBA demonstrated a synergistic effect; a balanced BAP–IBA combination optimized shoot proliferation and vigor, whereas a high auxin-to-cytokinin ratio severely repressed organogenesis. Conclusion: this research establishes a reproducible, two-phase protocol that integrates rigorous aseptic establishment with tailored PGR application, effectively balancing high multiplication with superior shoot morphology for the commercial micropropagation of pitahaya.