Effect of drought stress and inoculation treatments on nutrient uptake, essential oil and expression of genes related to monoterpenes in sage (Salvia officinalis)

Abstract

To investigate the effect of inoculation of Piriformospora indica (P. indica) and Pseudomonas fluorescens (P. fluorescens) on some morphological and physiological traits, nutrient concentration, essential oil (EO) and gene expression in Salvia officinalis under drought stress (100, 70 and 40% Field Capacity (FC)) we designed a factorial experiment in a completely randomized design with three replications. The results showed that by increasing drought stress intensity, percentage of root colonization by P. indica, growth parameters, relative water content, chlorophyll index, essential oil yield, and nutrient concentration decreased. The highest and lowest values of dry herb yield (33.94 and 11.62 g pot−1), RWC (80.20 and 51.60 %), chlorophyll concentration (38.46 and 30.47), essential oil yield (0.22 and 0.20 ml pot−1) and P concentration (0.40 and 0.26 %) were observed in P. indica inoculated plants under well-watered conditions and non-inoculated plants in severe drought stress (40% FC), respectively. The Sabinene synthase (ss) gene expression rate enhanced notably under drought stress and the highest expression rate was obtained in the 40% FC in plants inoculated with P. fluorescens. In contrast, the expression of geranyl diphosphate synthase (gpps) and bornyl diphosphate synthase (bpps) decreased under drought stress. The highest amount of predominant compounds of essential oil including α-Thujone, 1,8-Cineole (36.48 and 13.26%) and Camphor (18.94%) were observed in bacterial inoculation treatment under drought level of 40% FC and non-inoculated plants in well-watered condition, respectively.