L-Phenylalanine and bio-fertilizers interaction effects on growth, yield and chemical compositions and content of essential oil from the sage (Salvia officinalis L.) leaves

Sage (Salvia officinalis L.) as the main herb in the world is cultivated in many countries. Essential oil from the sage leaf is used as raw material in pharmaceutical and cosmetics industries. To determine the effects of bio-fertilizers and foliar splay of L-phenylalanine on growth and morphophysiological characteristics and the main constituents and yield of essential oil from the sage leaves, a field experiment in a 2-year study (2016 and 2017) was done according to a combined design in southwestern Iran. Foliar spray levels of L-phenylalanine were 0, 250, and 500 ppm and various bio-fertilizers including control or without inoculation (i), inoculation of the roots of sage seedlings with arbuscular mycorrhizal fungi (ii), inoculation of the roots of seedlings with P. fluorescens bacterium as a plant growth-promoting rhizobacteria (iii), inoculation of the roots with equal mixture of arbuscular mycorrhizal fungi and P. fluorescens bacterium in prepared suspension (iv). The main constituents of the essential oils from the sage leaves were oxygenated monoterpenes including 1,8-cineole, camphor, α-thujone, and β-thujone. Results indicated that the foliar spray of L-phenylalanine significantly influenced measured characteristics, especially quantity and quality of the essential oils from the sage leaves. The foliar spray of L-phenylalanine improved the concentration of chlorophylls, fresh and dry herbage weights, and essential oil yield under treatments of inoculation (fungi and bacteria). Generally, the highest contents of oxygenated monoterpenes in the essential oil of sage were obtained from the foliar spray of L-phenylalanine at 500 ppm under inoculation of the roots of sage seedlings with P. fluorescens bacterium. Indeed, the applied biofertilizers and L-phenylalanine had synergistic effects on the amounts secondary metabolites of sage especially oxygenated monoterpenes. In conclusion, we found that the foliar application of L-phenylalanine along the inoculation of arbuscular mycorrhizal fungi and P. fluorescens and as well as their equal mix can be improved the growth, quantity and quality yields of the essential oil of sage in organic and sustainable agriculture systems.