Development, maturation and conversion of somatic embryos of Actaea racemosa L.

Somatic embryogenesis is a very effective clonal propagation system in rather slowly multiplying plants as Actaea. However, in Actaea the slow development, asynchronous histodifferentiation and maturation of the somatic embryos are the obstacles for effective multiplication systems. Therefore, in the presented study, the effect of genotype, the influence of pre-culture and conversion media on development and conversion of isolated somatic embryos, as well as on further plant development were investigated. For this, embryogenic clusters from three Actaea genotypes have been cultivated on a modified MS-medium with 0.1% activated charcoal (AC), 2.25 mu M 2,4-dichlorophenoxyacetic acid (2,4-D) or with 3 mu M gibberellic acid (GA(3)) for at least 3 months in darkness. Single somatic embryos characterized by their histodifferentiation stage have been observed in terms of their response for 6 months. All the cotyledonary stage embryos converted while only 40% of torpedo embryos and less than 10% of earlier developmental stages converted within this time. The use of a medium enriched with activated charcoal was not appropriate to stimulate embryo maturation and conversion in some genotypes. Therefore, application of 0.6 mu M GA(3) or 0.9 mu M 6-benzylaminopurine (BAP) compared to the medium with activated charcoal was evaluated for an acceleration of somatic embryo maturation, conversion, and plant development. The application of BAP accelerated greening of embryos and conversion in all genotypes. A long term effect of plant growth regulators as 2,4-D and GA(3) in pre-culture medium could be reduced by application of BAP to the conversion medium. From the converted embryos, only 50-70% developed into plants after 14 weeks on MS-medium with 0.1% activated charcoal.