Argania spinosa (L.) Skeels is an endangered plant species endemic to Morocco. In recent years, attempts to develop in vitro regeneration systems for this species were made. However, rooting and acclimatization of in vitro plants have been a bottleneck for successful propagation. In the present study, the effects of different concentrations of auxins, putrescine, silver nitrate (AgNO₃) and ammonium nitrate on the in vitro rooting of adventitious shoots of two argan genotypes “Mejji” and “R’zwa”, were evaluated. The highest rooting percentages (86.6% in “Mejji” and 84.4% in “R’zwa”) were observed on Murashige and Skoog (MS) medium modified by reducing the ammonium nitrate concentration and supplemented with 1.5 mg L⁻¹ indole-3-butyric acid (IBA), 0.5 mg L⁻¹ 1-naphthalene acetic acid (NAA), 2 mg L⁻¹ AgNO₃ and 160 mg L⁻¹ putrescine. This medium resulted in the development of a good root system after only 10 days of culture. Plantlet acclimatization was carried out using different substrate mixtures, and high survival rates (100%) were observed when the substrate contained either peat alone or a sand–peat mixture (1:1, w/w). The high percentages of rooting and acclimatization reported in the present study are of high importance for rapid and large-scale propagation of this endangered species.

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.

The effects of major mineral salts, l-glutamine, myo-inositol and carbon source on shoot bud proliferation of date palm (Phoenix dactylifera L.) cv. Mejhoul were evaluated. Different concentrations of ammonium nitrate (NH₄NO₃; 550, 825 or 1650 mg/L), potassium nitrate (KNO₃; 633.3, 950 or 1900 mg/L), calcium chloride dehydrate (CaCl₂·2H₂O; 147, 220 or 440 mg/L), potassium dihydrogen phosphate (KH₂PO₄; 57, 85 or 170 mg/L), magnesium sulfate heptahydrate (MgSO₄·7H₂O; 123, 185 or 370 mg/L), l-glutamine and myo-inositol (0.5, 1, 1.5 and 2 g/L), sucrose, sorbitol, mannitol or commercial granulated sugar (10, 20, 30, 40 or 50 g/L) were tested. The highest number of shoot buds per explant (18.7) occurred on the medium containing 825 mg/L NH₄NO₃, 1900 mg/L KNO₃, 220 mg/L CaCl₂·2H₂O, 170 mg/L KH₂PO₄, 370 mg/L MgSO₄·7H₂O as well as 1 g/L l-glutamine, 2 g/L myo-inositol and 30 g/L sucrose. The results showed that the frequency of hyperhydricity significantly increased in media containing 1650 mg/L NH₄NO₃. The concentrations of l-glutamine, myo-inositol and carbon source significantly affected the number of shoot buds per explant. However, they had no effect on hyperhydricity, tissue browning and precocious rooting. Shoots of 4.5–6.0 cm in length were isolated and transferred onto hormone-free media for elongation and rooting. After 3 months, the developed plantlets were successfully transplanted in a glasshouse and over 90 % survived acclimatization.