Efficient Plant Regeneration from Explants of Compact Oregano (<i>Origanum compactum</i> Bentham)

Abstract

Origanum compactum Benth., a species endemic to Morocco characterized by its biological activities, is overexploited because of its commercial value and threatened with extinction. Accordingly, measures for its conservation are needed. Micropropagation serves as a solution for the protection and the domestication of this species. In this investigation, we established a protocol for vegetative multiplication in vitro of Origanum compactum by the axillary bud technique. Six culture media (SH, SD, N30K, MS, MSm, B5) were tested to determine the most suitable mineral medium for growth and development of explants. Four cytokinins: Kinetin, Zeatin, BAP (6-Benzylaminopurine), 2ip (2-Isopentenyladenine) and three compounds with cytokinin activity: Adénine, 1,3-Diphenylurea (DPU) and Thidiazuron (TDZ) at five concentrations (0.44, 1.33, 2.22, 3.11, 4.44 μM) were tested on budding, growth, hyperhydria and rooting. Then three auxins, Indole-3-acetic acid (IAA), Naphthalene acetic acid (NAA) and Indole butyric acid (IBA) at four concentrations (1.14, 2.85, 4.56, 6.27 μM) in presence of 2.22 μM BAP were evaluated. The combination of Gibberellic acid (0.29, 1.5, 2.60, 2.89 μM GA3) and three polyamines (Putrescine, Spermidine, Spermine) at five concentrations (1.134, 3.402, 5.67, 7.938, 11.34 μM) with cytokinins and auxins were considered. Our results show that Margara medium is the most efficient and BAP at 2.22 μM is the best cytokinin for development of the aerial parts, with a regeneration rate of 88, 90%; rhizogenesis is successful with the combination of 6.27 μM IAA and 2.22 μM BAP. Moreover, the integration of 2.89 μM GA3 with 2.22 μM BAP and 6.27 μM IAA promotes vitroplant growth, bud and shoot multiplication and elongation of the aerial part. The addition of polyamines with 2.22 μM BAP and 6.27 μM IAA does not improve the root part, but Spermine at 5.67 μM promotes bud and shoot multiplication with a high percentage of regeneration, and spermidine at the same concentration gives long explants. Finally, plantlets with good root development were successfully acclimatized to natural conditions and served as a source to establish in vitro culture again.