In vitro flowering, glandular trichomes ultrastructure, and essential oil accumulation in micropropagated Ocimum basilicum L.

Abstract

The aromatic and medicinal properties of Ocimum basilicum L. (sweet basil) are related to the unique essential oil chemistry in different cultivars. This study describes efficient micropropagation and in vitro flowering protocols from shoot tips and reveals information on seed germination capability, glandular trichomes ultrastructure, and essential oil content and composition at different plant developmental stages from micropropagated O. basilicum ‘Sweet Thai’, chemotype methyl chavicol. Shoot tips from 2-mo-old aseptic seedlings were induced to proliferate shoots on Murashige and Skoog (MS) medium supplemented with 6-benzyl-aminopurine (BAP) and gibberellic acid (GA3) either alone or in combination with α-naphthaleneacetic acid (NAA). Maximum shoot formation was achieved in MS medium supplemented with 1.0 mg L−1 BAP. The micropropagated plants were successfully acclimatized ex vitro with an 80% survival rate. All of the micropropagated plants flowered in vitro on MS medium supplemented with 1.0 mg L−1 GA3. Relative to the mother plant, in vitro plants flowered at a younger stage of plant development but showed a lack of seed formation, fewer fully filled peltate glandular trichomes, lower essential oil content, and higher methyl chavicol content. Ex vitro plants flowered at an intermediate stage of plant development and formed seed with nearly the same seed germinability, essential oil content, and methyl chavicol content as the mother plant.