Nodal segment explant type and preconditioning influence in vitro shoot morphogenesis in Ginkgo biloba L.

Ginkgo biloba is an ancient tree of high medicinal value due to many phytochemicals it produces. In vitro clonal propagation offers alternative strategy for its rapid clonal multiplication, with application in the conservation of the endangered tree and production of its phytochemicals among which triterpene lactones are the most important. Shoot morphogenic response of G. biloba were studied using woody and herbaceous nodal segment explants. The explants were collected in the winter and summer seasons and cultivated using solid and liquid Murashige and Skoog medium supplemented with concentrations of thidiazuron (TDZ), N6-benzylaminopurine (BAP) or kinetin (Kin). Woody nodal segment explants collected in the two seasons were non-responsive to shoot induction while herbaceous responded to the in vitro morphogenesis. Pretreatment of woody nodal segment explants with TDZ stimulated morphogenic capability with an enhanced shoot formation response. Nodal explants obtained during winter season were more responsive to the in vitro shoot morphogenesis. Induction of the shoots in liquid medium was unsuccessful with all explants obtained from different seasons. Most TDZ-induced micro shoots showed stunted growth but, cultivation on solid medium amended with BAP and alternating solid medium cultivation with the liquid improved shoot growth and quality. The induced micro shoots did not respond to rhizogenesis, with basal callusing and basipetal shoot necrosis encountered during the micropropagation. Results of the experiments showed that explants collection season influenced in vitro clonal propagation in G. biloba and the strategy employed in the study could be of application in the clonal propagation of non-responsive woody nodal segment explants(s) of other species.