Effects of liquid, temporary immersion bioreactor and solid culture systems on micropropagation of Lilium ledebourii via bulblet microscales— An endangered valuable plant with ornamental potential

Lilium ledebourii (Baker) Boiss. (Liliaceae) is a critically endangered lily species native tonorthern Iran, where it is protected by law. In order to develop a cost effective method for largescalepropagation, the effects of three culture systems (solid, liquid and temporary immersion)and two types of cytokinins [6-Benzyladenine (BA) and Thidiazuron (TDZ)] were studied onthe in vitro plant regeneration of L. ledebourii. To establish the protocol, we used in vitroregenerated bulblets obtained from bulb scale segments that were cultured on solid Murashigeand Skoog (MS) media as starting material. The bulblet microscale transverse thin cell layerswere cultured on MS solid medium containing 3% sucrose and different combinations of plantgrowth regulators. Choice of both, the culture system and the type of cytokinin, affected thedifferentiation of explants. Two types of calli formed on explants: type I callus wasembryogenic, while type II callus was shoot organogenesis. The highest percentage (94%) ofembryogenic callus was obtained when calli were transferred on MS solid media supplementedwith 0.54 μM α-Naphthaleneacetic acid (NAA) and 0.44 μM BA. In addition, it was alsoobserved that the use of temporary immersion bioreactor resulted in a significantly loweramount of shoot organogenesis rather than solid culture systems. Seventy percent of theplantlets were successfully acclimatized to ex–vitro conditions and were phenotypically similarto the mother plants.