Park, IS, et al., Journal of Wood Science 58: 64-68 (2012)
We attempted to develop a method for the regeneration of plantlets from mature seeds of medically important Magnolia obovata via the induction of somatic embryogenesis in vitro. We initially cultured halves of mature seeds on either Murashige and Skoog (MS) medium or B5 medium that contained 0, 1, 5 or 10 lM gibberellic acid (GA3) for 1 month and then transferred the half-seeds to half-strength MS basal medium or B5 basal medium for further culture in the absence of GA3. Proembryogenic masses (PEMs) were observed 1 month after the transfer of the halved mature seeds to the medium without GA3. The frequency of formation of PEMs was higher (28%) after initial culture in MS basal medium plus 1 µM GA3 than in other tested media (0 or 4%). Somatic embryos that had been developed from PEMs were cultured on half-strength MS basal medium or B5 basal medium for completion of maturation and then transferred to fresh aliquots of the same medium for initiation of germination. The frequency of germination, with the formation of normal primary leaves and roots, was above 80%. We transferred the somatic embryo-derived plantlets to soil for acclimatization and the plantlets continued to thrive.
The main aim of the present study was to induce the formation of proembryogenic masses (PEMs) and the regeneration of complete plantlets from mature seeds of M. obovata.
Mature seeds were collected from an approximately 60-year-old specimen of M. obovata on the campus of the Tokyo University of Agriculture and Technology in Fuchu, Tokyo, Japan, on 16 August 2007
The surface of seeds was sterilized by washing seeds as follows: immersion in 70% ethanol for 2 min; immersion in a solution of 6% sodium hypochlorite that contained a few drops of Tween 20 for 30 min; immersion in sterile distilled water for 10 min (repeated a total of five times); immersion in 0.01 M HCl for 3 min; and immersion in sterile distilled water for 5 min (repeated a total of three times).
The addition of 1 lM GA3 to initial MS basal medium might promote the induction of PEMs from mature half-seeds of M. obovata.
For the induction of somatic embryos that had been developed from PEMs, they were cultured on half-strength MS basal or B5 basal medium plus 30 g/L sucrose and 3 g/L gellan gum with replacement by fresh medium at monthly intervals at 25oC in darkness.
Plantlets were cultured for 4 months in vitro and then transferred to potting soil (peat moss, vermiculite, perlite; v/v, 1:1:1).