In vitro shoot culture of Rhododendron fortunei: An important plant for bioactive phytochemicals

Abstract

Plants in the genus Rhododendron L. produce more than 200 compounds and have been considered an important source for bioactive phytochemicals. Production of these plants, however, requires healthy and genetically uniform propagules. This study evaluated effects of culture media and growth regulators on axillary shoot induction of R. fortunei Lindl. as well as auxin for in vitro and ex vitro rooting of microcuttings. Protocols for in vitro shoot culture of this species were developed. Two-node explants were cultured on either Economou and Read (ER) medium or woody plant medium (WPM) supplemented with 4.0 mg L−1 6-(4-hydroxy-3-methylbut-2-enylamino) purine or zeatin (ZT) and 1.0 mg L−1 naphthaleneacetic acid (NAA). More than 10 axillary shoots were produced per explant regardless of medium. The axillary shoots were used to produce additional two-node explants or as microcuttings for rooting. Two-node explants derived from the axillary shoots cultured on the same media produced even higher numbers of shoots, ranging from 17 to 20 on both ER medium and WPM from the second to the third or fourth cycle of culture, shoot numbers started decreasing in the fourth or fifth cycle. Microcuttings were easily rooted in vitro with rooting percentages of 100% on ER and 84.0% on WPM supplemented with 1.0 mg L−1 indole-3-butyric acid (IBA). The rooting percentages were almost 100% in a peat-based substrate irrespective IBA treatment. Micropropagated plants were morphologically stable and grew vigorously with a 95% survival rate in a greenhouse. The established methods could be used for rapid propagation of disease-free and genetically uniform liners which can be used to produce feedstocks for extracting bioactive phytochemicals.