Rossen S. Sokolov, Bistra Y. Atanassova and Elena T. Iakimova
The objective of this study was to assess the regeneration response of in vitro cultured Magnolia × soulangeana ‘Alexandrina’ and Magnolia liliiflora ‘Nigra’ to nutrient medium composition. In the primary culture (initiated from dormant axillary buds) combinations of Murashige and Skoog (MS) basal salts with 6-benzylaminopurine and α-naphthaleneacetic acid were tested. The primary explants of cv. ‘Alexandrina’ expressed higher regeneration rate than cv. ‘Nigra’. For both species, the regen eration was most strongly potentiated at addition of 0.25 mg dm−3 of the cytokinin alone. The auxin exerted undesir–able effects. Several basal salts media were applied in proliferation stage and their physiological effects were evaluated in reference to traditionally used MS. At culturing on Chée & Pool C2d Vitis Medium (VM) that is for the first time introduced to magnolia and on MS, M. liliiflora formed more but less elongated shoots than M. soulangeana. However, on VM, substantial increase (25-30%) of the number of axillary shoots and leaves, shoot length and fresh and dry weights over MS was established for both species. This suggested VM as promising composition of nutrients in multiplication stage. Microshoots obtained on MS, VM, Rugini Olive Medium and DKW Juglans Medium were successfully rooted in vitro and subsequently established ex vitro. The findings expand the information on magnolia response to culture conditions and contribute to elaboration of innovative elements of protocols for establishing tissue cultures with high regeneration capacity.