A protocol for efficient micropropagation of rare orchid Vanda brunnea Rchb.f.

• The first effective micropropagation protocol for the rare orchid Vanda brunnea. • ORCHIMAX multiplication medium has a subsequent effect on the acclimatization stage. • Brassinolide (BL) can relieve the damaging effects of stress during acclimatization. Orchids are one of the most popular groups of ornamental plants, and growing demand for them forces the horticultural industry to increase their production. This can be effectively done by in vitro propagation. This study focued on the development of an efficient protocol for in vitro propagation of a rare orchid species, Vanda brunnea (syn. Vanda henryi Schltr.). Two media, ORCHIMAX and Murashige and Skoog (MS) were tested, with or without 0.5 mg·L−1 benzyladenine (BA). Acclimatization of microplants to ex vitro conditions was done using water, 0.05% brassinolide (BL), or 1% abscisic acid (ABA). The best regeneration (100%, 6 microplants/explant) was observed on the ORCHIMAX medium (regardless of the BA presence). At the acclimatization stage, a lower stomatal conductance was observed in microplants regenerating on ORCHIMAX medium and treated with 0.05% BL. Plants regenerating on ORCHIMAX had a lower hydrogen peroxide content and a higher catalase activity than regenerants from the MS. In general, the lowest peroxide level and the highest catalase activity were found in microplants treated with BL which evidently contributed to the reduction of the oxidative stress at the acclimation stage. This resulted in 100% survival rate and a highlly efficient method for micropagation of this species. [ABSTRACT FROM AUTHOR]