Somatic embryogenesis from immature zygotic embryos ofGinkgo biloba

Abstract

Immature zygotic embryos ofG. biloba were taken, at various developmental stages, from ovules harvested in November 1993. Zygotic embryos showing the beginning of the cotyledonary development cultured on modified Murashige & Tucker (1969) media proliferated intensely. In fact, 98.5% of the immature zygotic embryos produced embryogenic and undifferentiated tissues (calluses), in proportions varying depending on the hormonal composition of the induction media. After two weeks of culture, direct embryogenesis was observed on the hypertrophic cotyledons when benzyladenine 10 μM was used as the sole plant growth regulator in the induction media. The addition of different concentrations of NAA (5–10–20 μM) and of BA (5 μM) to the induction media led to an indirect embryogenesis after two months, when the calluses were transferred to the development media without auxin. The highest frequency of embryogenic tissues (90–95%) and the highest number of somatic embryos per explant (9.6) were obtained with benzyladenine (10 μM) as the sole exogenous growth factor. Some embryos isolated mechanically or ‘in situ’ on the callus developed as far as the later cotyledonary stage.