Direct somatic embryogenesis as a rapid and efficient system for in vitro regeneration of Arabidopsis thaliana

A simple, rapid and effective system to regenerate Arabidopsis plants via direct somatic embryogenesis has been established. Somatic embryogenesis was induced directly during culture of immature zygotic embryos. The frequency of somatic embryogenesis was strongly influenced by the stage of development of the explants. Explants in different developmental stages were cultured on B5 agar medium containing 5 M 2,4-dichlorophenoxyacetic acid and the highest frequency (up to 90%) of somatic embryogenesis was observed in zygotic embryos with fully-developed cotyledons. The first somatic embryos developing directly from explant tissue were noticed after 8 days of culture. Somatic embryogenesis of a high frequency (87–96%) was observed in cultures of the all six genotypes tested (Columbia, C-24, RLD, Wassilewskaja, Landsberg erecta and Wilna). Subculture of somatic embryos onto auxin-free medium resulted in their conversion into plants with an average frequency of 79.5%. The regenerates showed normal morphological characteristics and were fertile. All 56 analysed plants displayed a diploid number of chromosomes and two out of 96 (2.1%) tested plants carried a chlorophyll or embryo-lethal mutation.