High-efficiency direct somatic embryogenesis and plant regeneration from leaf base explants of turmeric (Curcuma longa L.)

This study describes for the first time a simple and quick direct somatic embryogenesis and plant regeneration protocol for turmeric (Curcuma longa L.) using leaf base explants. Preincubation of explants was carried out on solid Murashige and Skoog (MS) medium containing 4.49 μM 2,4-dichlorophenoxy acetic acid for 20 days under continuous dark condition. Subsequently transfer of the explants for 2 weeks to MS liquid medium containing 1.32 μM 6-benzyladenine (BA) under illuminated condition resulted in the highest percentage of somatic embryo (91.1 %) induction. Secondary somatic embryos which originated from primary somatic embryos were also observed in the same medium supplemented with 2.20 and 2.64 μM BA. Thereafter, mature somatic embryos germinated readily and the maximal plantlet development (87 %) was achieved on 1/2-strength MS medium containing gibberellic acid (GA₃) under dark condition. Histological analysis revealed that the proembryogenic masses were initiated directly from the area near the vascular tissues of the leaf base explants. Presence of clear protoderm in the globular structure and procambial strands in the matured stage of somatic embryos confirmed that these structures were true somatic embryos. Somatic embryos were successfully acclimatized ex vitro at a survival rate of 72.9 % and they were normal phenotypes.