Abstract
Arbutus unedo L. is a perennial tree, native in the Mediterranean area, and tolerant to stress conditions. Due to its economic potential, there is an increasing demanding for plants by producers and farmers. In order to offer cloned material with assured quality, several micropropagation protocols have been developed, including somatic embryogenesis induction. However, little is known about this process on strawberry tree and a great deal of work is still necessary to successfully clone in A. unedo through somatic embryogenesis. Thus, the main goals of this work were: (i) to test the effect of the genotype on somatic embryogenesis induction, (ii) to analyse the role of adult and young materials on induction, and (iii) to perform a comparative histological analysis between somatic embryos and their zygotic counterparts. Somatic embryogenesis was induced on apical expanded leaves from in vitro shoots of several genotypes in Andersson medium with 3% sucrose and different concentrations of BAP (2.0 mg L−1) and NAA (0.5, 1.0, 2.0, 5.0, 10.0, 15.0 and 20.0 mg L−1). Embryogenesis induction rates ranged from 0 to 94.5%. Higher induction rates were achieved on the medium with 2 mg L−1 BAP and 2 mg L−1 NAA, and are genotype dependent. After a 3-month induction period, the highest somatic embryogenesis induction rate was 94.5% on genotype AU4. Embryos at different developmental stages were found, as well as abnormal somatic embryos. SEM images showed different anomalies being the most common embryos displaying more than two cotyledons or fused embryos. Embryo germination was not genotype dependent and the maximum embryo conversion rate achieved was 73.5%. However, only 39.21% of the embryos were able to grow into plantlets which displayed a normal chromosome number (2n = 26). Histological analysis showed differences in the cell organization between somatic and zygotic embryos, as well as several morphological anomalies. Overall, the developed somatic induction protocol proved to be very efficient, with high induction rates achieved, both from seedling and adult material, but its genotype dependent. However, embryo conversion still needs to be improved, in order to fully seize the potential of this micropropagation technique.
Key message
Somatic embryogenesis was induced in leaves of micropropagated shoots established from selected adult trees. Induction is genotype dependent and higher induction rates (94.5 %) were achieved with 2 mg L−1 BAP and 2 mg L−1 NAA.
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Data availability
The datasets generated and analysed during the current study are available from the corresponding author on reasonable request.
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Funding
This research was funded by Foundation for Science and Technology (Portugal), who supported J. Martins PhD fellowship (SFRH/BD/122478/2016), ReNATURE project (CENTRO-01-0145-FEDER-000007) and F4F-Forest for the future (CENTRO-08-5864-FSE-000031, Programa Operacional Regional do Centro, Fundo Social Europeu). This work was carried out at the R&D Unit Center for Functional Ecology—Science for People and the Planet (CFE), with reference UIDB/04004/2020, and CESAM (UIDB/50017/2020+UIDP/50017/2020), financed by FCT/MEC through national funds, and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020.
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Conceptualization, JM and JC; formal analysis, JM; data analysis, JM; writing—original draft preparation, JM; writing—review and editing, GP, SC and JC; funding acquisition, JC.
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Communicated by Paloma Moncaleán.
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Martins, J., Correia, S., Pinto, G. et al. Cloning adult trees of Arbutus unedo L. through somatic embryogenesis. Plant Cell Tiss Organ Cult 150, 611–626 (2022). https://doi.org/10.1007/s11240-022-02314-4
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DOI: https://doi.org/10.1007/s11240-022-02314-4