Essential Oil Yield and Composition of Moldavian Balm (Dracocephalum moldavica L.) As Affected by Inoculation Treatments Under Drought Stress Condition

Abstract

The Moldavian balm essential oil contains numerous medicinal values in addition to its other wide application. The present study was carried out to evaluate the effect of plant growth-promoting bacteria and mycorrhiza-like fungi inoculation on Moldavian balm (Dracocephalum moldavica L.) essential oil yield and composition under drought stress condition. The experiment was arranged as factorial based on a randomized complete block design with three replications. The first factor was drought stress at four levels including no drought stress, low, medium and high drought stress. The second factor was inoculation treatments comprising of non-inoculated control, inoculation with Enterobacter sp., Pseudomonas sp., Agrobacterium sp. and Piriformospora indica. The results indicated that the interaction effect of drought stress × inoculation was significant on dry weight, essential oil content and yield of D. moldavica. Under all drought stress levels, inoculation with Enterobacter, Agrobacterium and Piriformospora increased the dry weight and essential oil yield of D. moldavica, compared with those in non-inoculated control. While the result of dry weight and essential oil yield from inoculation with Pseudomonas was almost equal to that of the non-inoculated control. The main components of essential oil were geranial followed by geraniol, geranyl acetate, neral, neryl acetate and geranyl formate. The chemical composition of essential oil was affected by drought stress and inoculation levels. Under all drought stress levels, the geranyl acetate content was found to increase in inoculation treatments with Enterobacter sp., Pseudomonas sp., Agrobacterium sp. and Piriformospora indica respectively. In general, inoculations with Piriformospora indica, Agrobacterium and Enterobacter increased the dry weight and essential oil yield under all drought stress levels and could be recommended to growers to reduce the application of chemical fertilizers in D. moldavica production.