Effect of Inoculation with PGPRs and Mycorrhiza-like Fungi on some Growth Traits and Essential Oil Yield of Moldavian balm (Dracocephalum moldavica L.) under Water Deficit Stress

The aim of this experiment was to study the effect of inoculation with growth promoting bacteria and mycorrhiza-like fungi (Piriformospora indica)  under water deficit stress on some morphological traits and essential oil yield of Moldavian balm (Dracocephalum moldavica L.).

a factorial experiment was conducted in University of Tabriz, Iran based on randomized complete block design with three replications in 2017. The first factor was water deficit based on field capacity (FC) at four levels including 80-100 % FC, 70-85%FC, 55-70% FC, 40-55% FC and the second factor was inoculation of Moldavian balm with different microorganisms including Enterobacter, Pseudomonas, Agrobacterium, Piriformospora indica and control (non-inoculation).  

The results showed that the effect of water deficit stress and inoculation treatments on all morphological traits were significant. With increasing water deficit stress, all growth traits including plant height, branch number, main branch length, number of cycle of flowers per main branches, essential oil content and yield were significantly reduced. The highest amount of dry flowering head yield (2.41g/pot) was obtained with Enterobacter sp. However, the highest dry mater yield (59 g/pot), essential oil percentage (0.32%) and essential oil yield (0.19 g/pot) were obtained under Agrobacterium treatment.  

In general, inoculations with Piriformospora indica and Agrobacterium, were the best treatments in terms of dry mater yield and essential oil yield under moderate drought stress conditions and can be recommended as treatments to reduce the application of chemical fertilizers in sustainable production of Moldavian balm.