Fluctuation of Essential Oil Constituents in Origanum syriacum subsp. sinaicum in Response to Plant Growth Promoting Bacteria

Abstract

Plant growth promoting bacteria are used as potential tools to enhance the growth and metabolism of different crops and aromatic plants. Bacillus SK1, Bacillus SK2, Serratia SK3, and Serratia SK1a were isolated from the wild plant; Origanum syriacum subsp. sinaicum and used in this study based on their compatibility with this plant. Furthermore, a pot experiment was designed to assess the effect of these isolates as well as Paenibacillus polymyxa (lab bacterial isolate) and gibberellic acid (GA3) on essential oil (EO) contents in Origanum. The harvested samples of Origanum were subjected to hydro-distillation, and the yielded oil was analyzed by gas chromatography/mass spectrometry (GC/MS). Growth performance and biochemicals of treated Origanum plants were affected by various bacterial strains isolated from wild Origanum rather than P. polymxa or GA3. The EOs content increased in treated plants in the following order: Serratia SK1a > P. polymxa> Serratia SK3 > Bacillus SK2 > Bacillus SK1. Fifteen compounds were identified, where monoterpenes were a major class. Carvacrol, γ-terpinene, and p-cymene were the major components in all treatments. Carvacrol was enhanced by about 69.9 % in response to Serratia SK3. The present results indicated that EO of aromatic plants could be engineered as a response to bacterial inoculation, particularly those isolated from the wild habitat of the plant.

Key words:

• Beneficial microbes
• Bacillus
• volatile organic compounds
• Origanum syriacum
• Serratia