In vitro seed germination and plantlet regeneration of Vanilla siamensis: an endemic species in Thailand

This study reports the in vitro germination of self-pollinated pod of Vanilla siamensis, native to Thailand. The aim of the present work is to determine the effect of culture media and plant growth regulators on seed germination and plantlet regeneration. The vanilla seeds were asymbiotically germinated on different culture media under aseptic conditions. The results showed that, New Dogashima medium (NDM) supplemented with 2% (w/v) sucrose, 15% (v/v) coconut water (CW) and 0.7% (w/v) agar gave the highest levels of seed germination at 10.1%. The fastest and highest percentage seed germination was achieved using NDM supplemented with 2 mg/l gibberellic acid (GA3). Seeds on this culture medium germinated within 7–8 weeks in comparison with 10–11 weeks on culture medium without plant growth regulators. Protocorms were transferred to different culture media with various concentrations of 6- benzyladenine (BA) to assess the protocorm development. The results revealed that 1⁄2 Murashige and Skoog (1⁄2 MS) medium gave the higher result in survival rate of protocorm than NDM. 1⁄2 MS medium with 0.5 mg/l BA was suitable for shoot formation. Plantlet development was completed after subculturing on 1⁄2 MS medium supplemented with 0.5 mg/l α-naphthaleneacetic acid (NAA) for 8 weeks and successfully acclimatized at 91.7%. The protocol outline here can be used for mass propagation of this endangered species and used as a guideline for improvement of V. siamensis and its in vitro conservation.