Abstract
In this study, several methods have been used to facilitate shoot formation from nodal explants of local almond ecotypes known as “Beldi” grown in Eastern Morocco. Nodal segments of divers old local genotypes were cultured on various concentrations of auxin (indole-3-butyric acid (IBA)) and cytokinins (6-benzyl-aminopurine (BAP), thidiazuron (TDZ), and kinetin (KIN)) added to two different media (Murashige and Skoog (MS) and Heller medium). The results showed that TDZ was more effective than the other tested hormones for in vitro proliferation of the “Beldi” ecotype. TDZ at the concentration of 1 mg/L significantly improved the nodal shoot proliferation rate, with the highest percentage (63.6% ± 0.63) and number of regenerated shoots (13 ± 0.54) recorded for S1 genotype inoculated on MS medium, while the most significant rooting rate (60.41% ± 0.81) of proliferated shoots and number of roots per shoot (7.3 ± 1.36) were achieved for S2 genotype on 1 mg/L of IBA incorporated to a half-strength MS medium. With 80% of plantlets survival, the rooted shoots were successfully adapted to the in vivo conditions and were grown vigorously in the greenhouse without any morphological abnormalities.
Highlights
Murashige and Skoog (MS) and Heller media were used in the presence and the absence of BAP at the concentration of 1 mg/L, or BAP combined with indole-3-butyric acid (IBA) at the concentration of 0.5 mg/L
MS and Heller media, as well as BAP, had a significant effect on proliferation rate, shoot number, and length. e results showed that a hormone-free Heller nutrient medium gives higher results (45.6%) of shoot proliferation for S2 genotype compared to a hormone-free MS medium (32.43%) noted for the same genotype. e lowest regeneration frequency (27.65%) was obtained on a hormone-free MS medium for S3
Regarding the interaction between media and plant growth regulators, 1 mg/L BAP allowed for better results in both media since proliferation rate was much more enhanced in MS medium than in Heller medium, and the average number of shoots was high (5 times more than without hormone), except for S2 genotype grown in MS medium, where no significant effect has been obtained on the number of shoots
Summary
E almond tree, native to Central Asia [1, 2], is one of the oldest domesticated fruit trees. It has been introduced by Phoenicians, Grecques, and Romans in different Mediterranean regions [3, 4], where it has adapted to various microclimates. Almond is a very polymorphous species due to its self-incompatibility [6] and open pollination in traditional culture [7], and its seed propagation gives highly variable local genotypes creating an important genetic variability in several areas of the Mediterranean basin. The world almond production for 2018-19 was around 1.28 million metric tons
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