A two-step procedure for in vitro rooting of micropropagated tea [Camellia sinensis L. (O) Kuntze] microshoots

Abstract

SummaryWe have developed a two-step procedure for rooting of tea microshoots in vitro. The effectiveness of different auxin treatments for root formation was found to differ. Among the auxins tested, 25 μM -naphthalene acetic acid (NAA) gave the best results, with 100% rooting, compared to 25 μM indole-3-butyric acid (IBA) or 25 μM indole-3-acetic acid (IAA), which induced 17% and 58% rooting, respectively. Incubation of tea microshoots on 0.33 Murashige and Skoog (MS) medium, supplemented with 25.0 μM NAA or 175.0 μM IBA for 10 d, followed by transfer to auxin-free 0.33 MS medium resulted in 100% rooting, whereas 50.0 μM IAA induced 91.7% rooting. Besides the different auxin treatments, the strength of the MS medium, the duration of incubation of microshoots in auxin-containing medium, the sucrose concentration, the gelling agent, the pH of the medium, the incubation temperature, the light intensity, and the quality of the shoots also played a significant role during in vitro rooting of micropropagated tea shoots. Among the combinations tested, the most effective results were obtained when green microshoots were incubated on 0.33 MS medium supplemented with 25.0 μM NAA, 50.0 mM sucrose, pH 5.5, gelled with 0.2% (w/v) PhytagelTM for 10 d at 25° – 30°C at a light intensity of 40 μmol m–2 s–1, followed by transfer of shoots to auxin-free 0.3 MS medium. This resulted in 100% rooting and, on average, 11 long roots were formed per shoot. Anatomical changes during adventitious rooting of micropropagated tea shoots in vitro were also studied to understand the process of rooting.