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Organogenesis is the in vitro regeneration technique used in Morocco for rapid and large-scale propagation of date palm. Unfortunately, this technique is hampered by tissue browning, a physiological disorder that decreases the proliferation capacity of shoot buds and affects the quality of the multiplied plants, and by endophytic bacteria, which are introduced in vitro even if explants are well disinfected. In order to solve these problems, the effects of different concentrations of the methanolic extracts from six Opuntia species were evaluated during shoot bud multiplication of date palm cv. Mejhoul. Organogenic cultures of date palm cv. Mejhoul were cultured for 4 months on semi-solid and half-strength Murashige and Skoog (MS/2) medium, supplemented with plant growth regulators (PGRs) and different concentrations (1, 5 or 10 ml/l) of the methanolic extracts from cladodes of Opuntia megacantha, O. ficus indica, O. robusta, O. aequatorialis, O. leucotricha and O. inermis. Our results showed that, regardless of the cactus pear species used, the concentration of 10 ml/l of the methanolic extract is not suitable for shoot bud multiplication since it results in considerable phytotoxicity. The optimal concentration for shoot bud multiplication was 1 ml/l of the extracts of O. ficus indica, which showed the highest number of shoot buds per explant (14.2), 5% tissue browning and the elimination of endophytic bacteria. The use of the methanolic extracts from cactus pear petals also resulted in bacterium elimination. However, it did not improve the multiplication rate. After the multiplication phase, shoot buds were transferred to the elongation-rooting medium then to glasshouse where a high survival rate of 80% was observed. |
