Effect of rhizobacterial volatile organic compounds (VOCs) in the production of essential oil of Mentha piperita L.

SANTORO, M., CAPPELLARI, L., GIORDANO, W., BANCHIO, E.

San Miguel de Tucumán

Congreso; VII congreso Argentino de Microbiología General (SAMIGE); 2011

SAMIGE

Inoculation of plant with PGPR (promoting-growth plant rizobacteria) bacteria is a useful tool to increase biomass. These microorganisms can cause their effect in the plant by producing soluble molecules and/or volatile compounds, (which diffuse in aqueous or aerial media, respectively). Mentha piperita L was subject to volatile organic compounds (VOCs) produced by different PGPRs such as Pseudomonas fluorescens WCS417r, Bacillus subtilis GB03 and Azospirillum brasilense SP7. The aim of this work was to determinate if the action of VOCs affect the production of essential oil (EO) in Mentha piperita L. Plant growth parameters such as shoot fresh weight, number and area of leaves, were measured. The plants in contact with VOCs of P. fluorescens and B. subtilis showed a 2-fold increase in shoot fresh weight and area of leaves relative to control plants not exposed to VOCs, without changes in number of leaves. No significant variations in the parameters analyzed were observed in plant exposed to VOCs of A. brasilense. The content of essential oil was also analyzed. Gas chromatography was used to determinate qualitatively and quantitatively the composition of monoterpenes. A 2-fold increase in total EO was observed with VOCs of P. fluorescens, relative to control. In this plants were also detected a 2,5-fold increase in content of pulegone and a 10-fold increase in content of menthone. The plants in contact with VOCs of A. brasilense showed a comparable increased in content of menthone, but was observed a 5-fold decrease of the content or menthol and to a 6-fold decrease of the content of menthofurane relative to control and the others bacterial VOCs analyzed. No significant variation was detected in relative percentage of majority monoterpenes; although plants exposed to VOCs of P. fluorescens displayed a major number of compounds in chromatographic profile relative to control and the others bacteria. Plants in contact with VOCs of B. subtilis not showed remarkable increase of monoterpenes in spite of the increment presented in biomass. Even when knowledge of plant promoting-growth activity of VOCs and its mechanism of action are very poor, we consider that bacterias like P. fluorescens are able to improve the production of essential oils in aromatic plants such as Mentha piperita L.