Histological analysis reveals the formation of shoots rather than embryos in regenerating cultures of Eucalyptus globulus

Tissue Culture of Corymbia and Eucalyptus

“…Other surface sterilants such as hydrogen peroxide (H 2 O 2 ), combinations of H 2 O 2 and ethanol, and alkyldimethylbenzalkonium chloride have been used occasionally for decontaminating eucalypt explants [47,[69][70][71][72][73][74][75][76]. A drop of detergent or wetting agent such as Tween 20 ® is often added to the solution to improve contact between the sterilant and the explant surface, which is often hairy in the case of eucalypt shoots or leaves.…”

“…For example, nodular regenerating structures form on the hypocotyls of E. globulus zygotic embryos plated onto MS medium containing 16.2 µM NAA [47]. These resemble somatic embryos, but microscopic examination demonstrates that they are formed via an organogenic, rather than an embryogenic, developmental pathway.…”

“…These resemble somatic embryos, but microscopic examination demonstrates that they are formed via an organogenic, rather than an embryogenic, developmental pathway. These authors [47] suggested that the numerous reports of eucalypt somatic embryogenesis using similar protocols may, in fact, have described organogenesis, and that histological examination of numerous serial sections is required to confirm an embryogenic pathway. Similarly, some reports of eucalypt organogenesis from nodes must be treated with caution because eucalypt leaf axils contain multiple accessory buds, which may be released from dormancy by the same growth regulators, especially cytokinins, that induce callus formation.…”

“…Histological examination is required to ultimately confirm the developmental pathway of embryo-like structures, although this has not been attempted in many reports of eucalypt embryogenesis [47]. In practice, the morphology of the proliferative tissue might not be important provided that the tissue can be converted easily into either somatic emblings or plantlets.…”

Vascular expression driven by the promoter of a gene encoding a high-affinity potassium transporter HAK5 from Eucalyptus grandis

“…To check whether the isolated genomic fragment contained promoter activity, an expression cassette harboring a promoter-GUS fusion was constructed and stably introduced into tobacco. Tobacco was chosen due to the technical difficulties generally associated with Eucalyptus regeneration (Dobrowolska et al 2017). Promoter-driven expression patterns were subsequently assessed by histochemical GUS assays on intact seedlings from three independent transgenic tobacco lines (namely 6, 17 and 18).…”