Direct adventitious shoot organogenesis and plant regeneration from cotyledon explants in Neolamarckia cadamba

Neolamarckia cadamba is a fast-growing and deciduous tropical hardwood with anatomical, morphological, and chemical characteristics that make it suitable for building materials, pulp production, and medicine raw materials. In this study, a protocol for direct adventitious shoot organogenesis and plant regeneration from the aseptic cotyledons of N. cadamba was established. The cotyledons with petioles from 3-week-old seedlings were used for adventitious shoot induction in DCR medium containing 22.20 mu M 6-benzyladenine (BA) and 0.27 mu M alpha-naphthaleneacetic acid (NAA). The frequency of adventitious shoot induction was 54.2%. Micro-shoots were then transferred to MS medium containing 4.44 mu M BA and 0.25 mu M indole-3-butyric acid (IBA) for shoot propagation. Available shoots per explant reached 5.9. The highest rooting percentage (98.3%) was obtained when shoots were transferred to half-strength MS medium supplemented with 0.27 mu M NAA and 0.25 mu M IBA. The rooted plantlets could be successfully acclimatized to a greenhouse with more than 95% survival, and the regenerated plants showed the same morphological characteristics as those of the control plants in fields. Histological observations revealed that the adventitious shoots only originated from the epidermal tissue around the edge of the cut zone of the cotyledonary petiole.