Direct Shoot Organogenesis in Murraya paniculata (L.) Jack: A Prerequisite for Genetic Transformation

An efficient in vitro regeneration system through direct shoot organogenesis was established for Murraya paniculata (L.) Jack (Orange Jessamine). Epicotyls, leaves, roots, and cotyledons from in vitro-germinated seedlings and several plant growth regulators (PGRs) were evaluated for their effects on plant regeneration. Longitudinally cut epicotyl segments were observed to be the optimal explants followed by uncut epicotyls (not longitudinally cut). Roots, leaves, and cotyledons were not suitable as explants as a result of little or no shoot induction. Adventitious shoot induction was enhanced by the addition of 6-benzyladenine (BA). The highest percentage of shoot induction (87%) and the greatest number of shoots per explant (12.7) occurred on Murashige and Skoog (MS) medium supplemented with 15 mu M BA from longitudinally cut epicotyls followed by 5.2 shoots per explant from uncut epicotyls. Optimal concentration of gibberellic acid (GA(3)) for shoot elongation was observed to be 15 mu M. Eighty-five percent of the regenerated shoots produced roots with an average of three roots per shoot on MS medium supplemented with 5 mu M indole-3-butyric acid (IBA). Our protocol for direct shoot organogenesis can potentially lead to the development of a robust method for production of transgenic plants of M. paniculata through Agrobacterium-mediated genetic transformation.