Factors affecting maintenance, proliferation, and germination of secondary somatic embryos of Eucalyptus globulus Labill
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The described protocol for repetitive somatic embryogenesis (SE) in Eucalyptus globulus produced more somatic embryos than the primary SE protocol. Primary somatic embryos (induced on MS3NAA) were transferred to the same medium, leading to new cycles of somatic embryos, for at least 2 years. The influence of medium (MS and B5), plant growth regulators (auxins and cytokinins), and light on secondary SE was tested. The MS medium without growth regulators (MSWH) was more efficient for cotyledonary embryo formation and germination than the B5 medium. Reducing auxin (NAA) levels increased the proliferation of globular somatic embryos and allowed SE competence to be maintained on medium free of plant growth regulators. The addition of two cytokinins (BAP and KIN) to the MS medium did not improve proliferation of globular secondary embryos, but was crucial during later stages of the SE process (germination and conversion). Data also show that light may influence the quality of the process, depending on its stage. Darkness should be maintained until the cotyledonary stage is reached, after which exposure to light is recommended.
KeywordsEmbryogenic competence Eucalyptus Growth regulators Media composition Secondary somatic embryogenesis
Murashige and Skoog medium
α-Naphthalene acetic acid
MS medium without growth regulators
Plant growth regulators
Authors thank Celbi for providing the material used in this study and for supporting part of the project. The Portuguese Foundation for Science and Technology FCT/MCT project POCI/AGR/60672/2004 also supported part of the project. Thanks are also due to José Dias and Armando Costa for technical assistance. FCT supported Glória′s (FCT/SFRH/BPD/26434/2006), Sónia′s (SFRH/BD/32257/2006) fellowships.
- Boulay M (1987) Recherches preliminaires sur l’embryogénèse somatique d’Eucalyptus gunnii. Ann Rech silvi Assoc. Cellulose:23–37.Google Scholar
- Merkle SA (1995) Strategies for dealing with limitations of somatic embryogenesis in hardwood trees. Plant Tissue Cult Biotechnol 1:112–121Google Scholar
- Muralidharan EM, Mascarenhas AF (1995) Somatic embryogenesis in Eucalyptus. In: Jain SM, Gupta PK, Newton RJ (eds) Somatic embryogenesis in woody plants, vol 2—angiosperms. Kluwer Academic Publishers, Dordrecht, pp 23–40Google Scholar
- Oller J, Celestino C, López-Vela D, Alegre J, Toval G, Toribio M (2006) Induction of somatic embryogenesis in mature zygotic embryos of Eucalyptus globulus Labill. 2nd Simposio Iberoamericano de Eucalyptus globulus. Pontevedra, Spain, 17–20 OctoberGoogle Scholar
- Pinto G, Silva S, Santos C, Neves L, Araújo C (2004b) Somatic embryogenesis of Eucalyptus globulus labill. and assessement of genetic stability. In: Borralho NMG, Pereira JS, Marques C, Coutinho J, Madeira M, Tomé M (eds) Eucalyptus in a changing world. Proceedings IUFRO Conference, Aveiro, Portugal, pp 543–544, 11–15 OctoberGoogle Scholar
- Prakash MG, Gurumurthi K (2005) Somatic embryogenesis and plant regeneration in Eucalyptus tereticornis Sm. Curr Sci 88(8):1311–1316Google Scholar
- Watt MP, Blakeway FC, Termignoni R, Jain SM (1999) Somatic embryogenesis in Eucalyptus grandis and E. dunnii. In: Jain SM, Gupta PK, Newton RJ (eds) Somatic embryogenesis in woody plants, vol 5. Kluwer Academic Publishers, Dordrecht, pp 63–78Google Scholar