Maturation and Conversion of Somatic Embryos Derived from Seeds of Olive (Olea europaea L.) cv. Dahbia: Occurrence of Secondary Embryogenesis and Adventitious Bud Formation.

Mouaad Amine Mazri,Rachida Naciri,Ilham Belkoura

doi:10.3390/plants9111489

Abstract

Maturation and conversion of somatic embryos are two crucial steps that hamper the development of efficient somatic embryogenesis systems in olive. Herein, a simple and efficient protocol for the maturation and conversion of olive somatic embryos is reported. Globular somatic embryos derived from seeds of cv. Dahbia were cultured on either half-strength olive (OM) or olive cyclic embryogenesis (ECO) media, with and without plant growth regulators (PGRs). The embryos reached the cotyledonary stage in 9 weeks, but those cultured on ECO medium containing 0.1 mg·L−1 6-(dimethylallylamino)purine (2iP), 0.1 mg·L−1 6-benzyladenine (BA) and 0.05 mg·L−1 indole-3-butyric acid (IBA) exhibited the largest sizes, with an average of 4.7 mm. Somatic embryo conversion into plantlets was evaluated using different culture media (half-strength OM or one-third strength Murashige and Skoog (MS)), light conditions (light or dark) and desiccation pretreatments. The highest rate of somatic embryo conversion (45%) was observed under a 16 h photoperiod on half strength OM medium containing 0.1 mg·L−1 gibberellic acid (GA3) and 0.1 mg·L−1 1-naphthalene acetic acid (NAA). The embryos that failed to germinate showed either necrosis, cotyledon greening with no further conversion, adventitious bud formation or secondary embryogenesis. The findings of this study will be beneficial for biotechnological applications in olive.

Highlights

Olive (Olea europaea L.) belongs to the Oleaceae family and is an economically important species native to the eastern Mediterranean, Asia Minor and northern Iraq, cultivated for fruits and edible oil production [1,2,3].Olive propagation and genetic improvement are generally performed by conventional techniques.Olive is commercially propagated by stem cuttings
The findings showed that somatic embryo growth varies depending on culture medium (Table 1)
Regeneration through somatic embryogenesis is difficult to achieve in olive, and the results reported in literature concern only a limited number of cultivars

Summary

Introduction

Olive (Olea europaea L.) belongs to the Oleaceae family and is an economically important species native to the eastern Mediterranean, Asia Minor and northern Iraq, cultivated for fruits and edible oil production [1,2,3].Olive propagation and genetic improvement are generally performed by conventional techniques.Olive is commercially propagated by stem cuttings. Olive (Olea europaea L.) belongs to the Oleaceae family and is an economically important species native to the eastern Mediterranean, Asia Minor and northern Iraq, cultivated for fruits and edible oil production [1,2,3]. Olive propagation and genetic improvement are generally performed by conventional techniques. Olive is commercially propagated by stem cuttings. In many genotypes, vegetative propagation through cuttings is hampered due to recalcitrance to rooting [4]. Genetic improvement through conventional cross-breeding is limited by many factors including the long juvenile period, high heterozygosis and seed germination difficulties [5]. In vitro culture of olive could be a good alternative to conventional methods. Tissue culture techniques such as somatic embryogenesis have been applied to several plant species, to Plants 2020, 9, 1489; doi:10.3390/plants9111489 www.mdpi.com/journal/plants

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