Production dynamics in relation to ontogenetic development and induction of genetic instability through in vitro approaches in Pelargonium graveolens: A potential essential oil crop of commercial significance

Rose-scented geranium (Pelargonium graveolens L’ Hert.) is a fragrant and bushy essential oil bearing crop of significant industrial and commercial importance. In an attempt to overcome the constraints imposed by sexual sterility for genetic improvement and restricted environmental adaptability of Pelargonium, the present study was aimed at exploring new niches for its cultivation in northern most sub-tropical part of India (Jammu). The flowering stage was found to be the optimum stage for harvesting in relation to essential oil quantity (0.16–0.18%, Fresh Weight Basis; FWB) and quality (geraniol 18% and citronellol 37%) during different phenophases of plant growth. Dynamics of essential oil turnover correlated well with the glandular trichome ontogeny using scanning electron microscopy (SEM). The present study also entailed induction of somaclonal variations via in vitro organogenesis. Organogenetic callus induction was achieved on B5 (Gamborg's) basal medium supplemented with kinetin/2,4-dichlorophenoxyacetic acid (Kn/2,4-D) and kinetin/indole-3-butyric acid (Kn/IBA). Frequency of callus induction ranged from 54–85%. Field established in vitro regenerated plants/somaclones displayed appreciable variability in fresh leaf biomass (365–2020 g, FWB), essential oil content (0.06%–0.26%) and quality (geraniol and citronellol as major constituents). To evaluate the genetic instability of calliclones, RAPD (Random Amplification of Polymorphic DNA) markers were used to assess the genetic basis of variability. Further, the identity of Pelargonium was confirmed by DNA bar-code analyses using three plant based barcoding loci (ITS, rbcL and psbA/trnH). They may be used as a standard reference system for varietal identification and protection of Intellectual Property Rights (IPR). Overall, the present investigation demonstrates the feasibility of Pelargonium cultivation in sub-tropical niches as a short duration winter crop, with desirable essential oil content and composition for commercial purposes. It also establishes a viable method for induction of variability for genetic amelioration of sexually sterile crop.