RAPID IN VITRO PRODUCTION OF TRUE-TO-TYPE PLANTS OF POGOSTEMON HEYNEANUS THROUGH DEDIFFERENTIATED AXILLARY BUDS

Rapid propagation of Pogostemon heyneanus Benth. (Lamiaceae) was accomplished through culture of node explants on Murashige and Skoog (MS) medium containing N6-benzyladenine (BA). Random amplified polymorphic DNA (RAPD) and gas chromatographic (GC) analysis of in vitro-derived progenies were used to determine the true-to-type nature of in vitro-derived plantlets. At the optimum level of BA (2.22 μM), the axillary buds underwent a degree of dedifferentiation to become small globular green masses from which a mean of 17.1 shoots were developed within 40 d. Retaining the culture without subculture enhanced the number of shoots (>30 shoots). Increased callus proliferation was observed at higher concentrations of BA in concomitance with a reduction in number of shoots. However, prolonged culture without subculture (more than 60 d) initiated 25–30 shoot buds from the callus. Culture of node segments excised from in vitro shoots on fresh medium with optimal BA (2.22 μM) exhibited a similar response, but with an increase of shoots (mean of 26.3 shoots per node) within 40 d. Subculture of shoot clumps on half-strength MS basal medium resulted in elongation (more than 4 cm) of most of the shoots along with the development of new shoots. Shoots developed were rooted most successfully on half-strength MS medium with 4.9 μM indole-3-butyric acid (IBA). Plantlets derived from the best rooting medium established in small cups exhibited 95% survival. Plantlets successfully established in field conditions exhibited morphological characteristics identical to the source plant. The RAPD profile of the in vitro-derived plants and source plant, using 10 random primers, was similar. The gas chromatogram of the extracted oils from in vitro-derived plants and the source plant showed similar patterns.