Salinity stress and PGPR effects on essential oil changes in Rosmarinus officinalis L.

Background: Medicinal plant species have been used by the ancestors around the world since ancient times. Rosmarinus officinalis is one of the most used medicinal plants, which belongs to the family Lamiaceae. To investigate the effects of different levels of salinity stress along with the induction of bacterial growth stimulation on the amount of essential oil composition in R. officinalis, an experiment was conducted in a randomized complete block design with 12 treatments and five replications. Salinity treatments included 0 (control), 2.5 (T1), 5 (T2), 7.5 (T3), 10 (T4) and 12.5 (T5) NaCl g/L, and the bacterium was pseudomonas fluorescence. Results: The percentage of essential oils showed a significant relationship with increasing salinity either alone or in composition with plant growth-promoting rhizobacteria (PGPR) inoculation treatments and it increased with increasing salinity levels to treatment 4 (T4, 10 g/L NaCl) but decreased with further increases in salinity levels in treatments without using PGPR and it was constant in treatment with using PGPR. Phellandrene, one of the main compounds of essential oils, showed a trend like the whole amount of essential oils in both group of treatments. Conclusion: Abiotic and biotic factors may influence the different mechanisms and limit the interactions between plant and beneficial bacteria, resulting in less-than-acceptable performance in plant growth promotion and management of diseases. In this context, the results revealed that the application of PGPRs can help improve the essential oil yield in R. officinalis even in salinity conditions. © 2019 The Author(s).