Systemic Induction of Monoterpene Biosynthesis in Origanum × majoricum by Soil Bacteria

Abstract

Italian oregano (Origanumxmajoricum) was subjected to root system inoculation with three species of plant growth-promoting rhizobacteria (PGPRs) (Pseudomonas fluorescens, Bacillus subtilis, Azospirillum brasilense), and essential oil (EO) content and plant growth were measured. Composition of monoterpenes, a major EO component, was analyzed qualitative and quantitatively by gas chromatography. Total EO yield for plants inoculated with P. fluorescens or A. brasilense was 3.57 and 3.41 microg/mg fresh weight, respectively, approximately 2.5-fold higher than controls, without change of quantitative oil composition. The major EO compounds, cis- and trans-sabinene hydrate, gamma-terpinene, carvacrol, and thymol, showed increased biosynthesis. Carvacrol was the only terpene showing significant increase of R% in plants inoculated with A. brasilense. Plant growth parameters (shoot and root fresh and dry weights, numbers of leaves and nodes) were evaluated. Shoot fresh weight was significantly increased by all three PGPR species, but only P. fluorescens and A. brasilense increased root dry weight. These two species have clear commercial potential for economic cultivation of O.xmajoricum. Knowledge of the factors affecting yield and accumulation of monoterpenes is essential for improving production of these economically important plant compounds.

Plant growth‐promoting effects of native Pseudomonas strains on Mentha piperita (peppermint): an in vitro study

“…Similar findings have been obtained in inoculation trials in other aromatic plants, e.g. our studies of Origanum majoricum, O. majorana and Tagetes minuta grown in vermiculite pots and inoculated with WCS417r (Banchio et al 2010;Cappellari et al 2013).…”

Systemic Induction of Secondary Metabolite Biosynthesis in Medicinal Aromatic Plants Mediated by Rhizobacteria

“…γ-terpinene showed a significant increase only in P. fluorescenstreated plants. Carvacrol showed a significant increase (~9-fold; p < 0.05) only in A. brasilense-treated plants (Banchio et al 2010). …”

“…O. x majoricum contains up to 3 % volatile oils, comprising more than 35 different compounds (Tabanca et al 2004). The major EOs, accounting for~55 % of the total oil volume, are cis-and trans-sabinene hydrate, terpinene, carvacrol, and thymol (Banchio et al 2010).…”

The genetic basis of foliar terpene yield: Implications for breeding and profitability of Australian essential oil crops

“…Myrtaceae is also interesting because to date, induction, a process that has been shown to be important in influencing terpene concentration in other species of woody plants (Banchio et al 2009;Mumm et al 2003;Phillips et al 2007) has not been demonstrated in the family (Henery et al 2008). Although Henery argued that induction might not be expected in an evergreen woody plant like Eucalyptus, there is scope for studies with other stimuli that have induced terpenes in other plants.…”