Rapid plant regeneration, analysis of genetic fidelity and essential aromatic oil content of micropropagated plants of Patchouli, Pogostemon cablin (Blanco) Benth. - An industrially important aromatic plant

Rapid and prolific shoot regeneration via direct organogenesis was induced from leaf explants of Patchouli, Pogostemon cablin (Blanco) Benth., an aromatic plant of immense industrial value, on Murashige and Skoog (MS) medium with benzylaminopurine (BAP) and α-naphthaleneacetic acid (NAA) within 4 weeks. The adventitious shoot bud induction and plant regeneration were greatly influenced by the origin, age of donor plant, and leaf position on stem. Leaf explants prepared from in vivo plants of different ages showed higher regeneration response as compared to the explants from in vitro plantlets of respective age. The shoot regeneration ability of explants was significantly related to the age of the donor plants as well as the leaf position on the stem. The highest number of shoots (94.6/explants) was obtained from 96.2% of leaf explants derived from the leaves located on the second node of the 3-month-old in vivo plants on Murashige and Skoog's (MS) medium containing 2.5μM benzylaminopurine (BAP) and 0.5μM naphthaleneacetic acid (NAA). Incorporation of 1.0μM gibberellic acid (GA₃) in MS medium significantly improved the shoot elongation (1.8-fold) within 2 weeks in 95% of the cultures. Regenerated shoots rooted spontaneously on growth regulator-free half strength MS medium and were successfully hardened and transferred to nursery with 96-100% survival rate. Genetic fidelity of the in vitro derived plants was assessed using random amplified polymorphic DNA (RAPD). Fourteen arbitrary decamers displayed same banding profile within all the micropropagated plants and in vivo explant donor plant. The molecular analysis complemented and compared well and showed genetic stability in the plants regenerated through direct shoot bud differentiation from leaf explants. The gas chromatogram of the extracted oils from in vitro derived plants and the mother stock plant showed similar essential oil profiles. Rapid and high multiplication frequency, molecular, genetic and essential oil content stability ensure the efficacy of the protocol developed for the production of this industrially important aromatic plant.