PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

Hymenodictyon orixense (Roxb.) Mabb. (Rubiaceae) also called as Bridal Couch tree, is a medicinal tree species parts of which are rich source of bioactive metabolites imparting the plant an impressive antioxidant, antimicrobial, anti-inflammatory and anti-apoptotic activities. Early loss of viability in seeds, lack of optimized propagation methods and increased anthropogenic pressure has led to conservation concern in this valuable tree species. The paper presents a robust in vitro propagation protocol for mass multiplication of H. orixense through seedling explants. In vitro seed germination was done in basal Murashige & Skoog’s (MS) medium and nodal segments from aseptically grown seedlings were used for further culture establishment. MS medium supplemented with 0.25 mg L^-1 kinetin was found optimal producing the highest mean shoot number (7.67 ± 0.88) and mean shoot length (4.91 ± 0.15cm). The addition of 0.025 mgL^-1 GA₃ during shoot multiplication cycle enhanced the shoot length to a mean 8.49 ± 0.33 cm nearly double the shoot length achieved with kinetin alone.  Root formation was 100% with ½ strength MS medium containing 1 mg L^-1 IAA and 0.025 mg L^-1 kinetin with highest mean number of roots. A 15-day cycle in optimized medium without gelling agent enhanced the quality of in vitro roots and developed plantlets were successfully acclimatized under greenhouse conditions with 85% survival. As the species possesses considerable medicinal importance, the propagation method described in the present study offers significant potential for the large-scale multiplication of selected genotypes exhibiting superior phytochemical characteristics. Furthermore, this approach may serve as an effective strategy for the ex situ conservation of the species, thereby contributing to its sustainable utilisation and long-term preservation.