Evaluation of 6-BA delivery systems for orchid bud-forcing: a case study on Dendrobium spp. conservation

The conservation and reintroduction of endangered plant specimens involve efficient propagation techniques, such as bud-forcing. We investigated the efficacy of different 6-Benzyladenine (6-BA) carriers, including lanolin, polyvinyl carboxy polymer (C940), and potassium hydroxide (KOH) solution, on the critically endangered species Dendrobium officinale Kimura & Migo (1936). Our data revealed that bud-forcing rates achieved with C940 formulations were significantly superior to those obtained with lanolin, a common 6-BA carrier, exhibiting increases ranging from 11% to 53% across treatments. Specifically, C940 yielded a higher overall shoot formation rate 16.08% (range: 9.52%-31.24%) compared to lanolin 12.36% (range: 7.66%-20.40%). This disparity is attributed to 6-BA’s superior solubility in the hydrophilic C940 matrix. The liquid KOH solution consistently yielded the highest bud-forcing across all tested 6-BA concentrations. When directly applied to dormant axillary shoots from pseudobulb segments and intact plants, shoot formation rates were significantly higher in pseudobulb segments than in intact plants (1.4-3.3 times, depending on the treatments). Selected formulations containing 20,000 ppm 6-BA were also applied to nodal shoots from pseudobulb segments of four Dendrobium species (D. adastra, D. anosmum, D. aphyllum, and D. primulinum), revealing species-specific interactions. The study contributes practical insights into enhancing orchid propagation for conservation through the strategic use of plant growth regulators and appropriate delivery methods.