Interaction Effect of Plant Growth Regulators on Shoot Micropropagation of Aromatic Plant Origanum elongatum (Bonnet) Emberger & Maire

Abstract

Origanum elongatum (Bonnet) Emb. & Maire, is a medicinal, aromatic and endemic plant of Morocco, characterized by its pharmacological effects, and is commonly used for the production of essential oils and aromas, resulting in high harvest and overexploitation pressure. This is why the present study aims to im-plement the in vitro micropropagation of Origanum elongatum for optimal vi-troplant production. Six macroelements were tested (SH, SD, N30K, MS, MSm and B5) and the SD medium was selected for vegetative propagation of the explants. Seven cytokinins: adenine (Ad), N6-(2-Isopentenyl) adenine, zeatin (Zeat), kinetin (Kin), benzyladenine (BAP), 1,3-diphenylurea (DPU) and thidiazuron (TDZ) were then evaluated at five concentrations (0.44, 1.33, 2.22, 3.11 and 4.44 µM/L) on growth, development, budding, rooting and hyperhydricity. 0.44 µM Kin was selected and combined with three auxins: indole-3-acetic acid (IAA), indole-3-butyric acid (AIB), and 1-naphthaleneacetic acid (NAA) at four concentrations (1.14, 2.85, 4.56 and 6.27 µM/L) to improve rooting and association with 1.14 µM IAA was shown to be efficient for roots development. Different concentrations of gibberellic acid (0.29, 1.5, 2.60 and 2.89 µM/L), combined with 0.44 µM/L Kin and 1.14 µM/L IAA, were tested and 2.60 µM/L GA 3 gave maximum buds and shoots. Then, the combination of three polyamines at five concentrations (1.134, 3.402, 5.67, 7.938 and 11.34 µM/L) with 0.44 µM Kin and 1.14 µM/L IAA showed an increase in the number of buds and shoots for 7.938 µM/L putrescine and 3.402 µM/L spermine. Finally, seedlings with good foliar and root development were acclima-tized.