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Received: 1 June 2016 /Accepted: 17 October 2017 /Published online: 19 January 2018 / Editor: Nancy Reichert
© The Society for In Vitro Biology 2018
Abstract Rhododendron wattii Cowan is a rare and endangered plant found in northeast India. In an effort to boost specimen numbers, experiments of in vitro seed germination, shoot induction on different media supplemented with the cytokinin isopentenyladenine (2iP), and root induction with auxins a-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA) and indole-3-acetic acid (IAA) in woody plant medium (WPM) were carried out. A maximum mean shoot number of 7.72 per explant were obtained from nodal explants cultured on WPM and 39.36 µM 2iP with a maximum mean shoot length of 2.30 cm per explant. Among the auxins investigated for root induction, IBA at 2.45 µМ was found to produce the most and the longest roots, when compared to other treatments. However, WPM supplemented with 0.2% (w/v) activated charcoal also showed 100% root formation with shoots having broader leaves compared to auxin treatments. About 60% of in vitro rooted plantlets transferred from lab to greenhouse conditions survived. Sixty acclimatized plants were reintroduced in the vicinity of their natural habitat at Naga Heritage Village, Kisama, Nagaland, in May 2016 for ex situ conservation. Survival of the reintroduced plants was confirmed during the field visit conducted in November 2016.
Keywords Rhododendron wattii . Seed germination . Micropropagation . In vitro induction of shoots and roots
Introduction
Rhododendron is the largest woody plant genus in the family Ericaceae. The name Rhododendron is derived from the Greek words rhodon (rose) and dendron (tree), meaning rose tree. The genus is represented by 1025 species in the world (Wu et al. 2015). Distribution of this genus ranges from southeastern Asia, specifically the regions of northwestern Himalaya through Nepal, Sikkim (India), eastern Tibet, Bhutan, north-eastern India (Arunachal Pradesh, Mizoram, Manipur, Nagaland, and Meghalaya), and upper Myanmar, to Western and Central China (Singh and Gurung 2009). In India, 135 taxa of Rhododendron have been recorded, of which 132 are found in northeastern India (Mao et al. 2017), excluding 3 taxa, namely, Rhododendron arboreum subsp. nilagiricum in southern India and Rhododendron collettianum Aitch. and Hemsl. and Rhododendron rawatii in Western Himalaya (Rai and Adhikari 2012).
R. wattii is endemic to...