In vitro propagation and callus induction of Hedychium longicornutum Griff. ex Baker using different explants

Hedychium longicornutum Griff. ex Baker (Zingiberaceae) is an endemic plant of the Malay Peninsula. This plant has a high potential to develop into a new ornamental plant because of wonderful multicolor with an exotic form of its inflorescence. However, the limited number of H. longicornutum in nature cannot meet consumer demand. Therefore, this study aimed to establish an efficient in vitro H. longicornutum propagation method through organogenesis. For direct organogenesis, shoot tips and leafy-shoot bases were cultured on Murashige and Skoog (MS) gelrite medium supplemented with different concentrations of N⁶-benzyladenine (BA) or thidiazuron (TDZ), for 4 weeks. Then, explants were transferred onto PGRs-free MS gelrite medium for another 12 weeks. The results revealed that shoot regenerated from leafy-shoot bases showed a higher amount and height when compared to regenerated shoots from shoot tips in every culture medium. Leafy-shoot bases that had been cultured on MS gelrite medium supplemented with 4 mg L^‑1 BA generated a large number of new plants (14.00±1.05 shoots explant^‑1) with the longest shoot (14.21±0.37 cm). Plants regenerated from this medium spontaneously rooted and exhibited a survival rate at 85% after acclimatization for 4 weeks. In indirect organogenesis, this study firstly investigated a suitable callus condition before establishing the indirect H. longicornutum organogenesis method for further study. Leaves and leafy-shoot bases were cultured on Hedychium callus induction medium (HEDM) supplemented with various combinations of 2,4-dichlorophenoxy acetic acid (2,4-D) and kinetin (KN) under light and dark conditions. After 8 weeks, leaves failed to induce callus in all treatments. In contrast, leafy-shoot bases cultured on HEDM supplemented with 1 mg L^‑1 2,4-D and 2 mg L^‑1 KN under light condition induced callus at 100% with the highest callus fresh weight (1.78±0.37 g explant^‑1). The information from this study will be a useful tool for mass-rapid in vitro multiplication of H. longicornutum, a valuable plant, on a commercial scale.