Study of the effect one strain of Azospirillum spp on the changes of essential oil of Ocimum basilicum L. Affected by drought stress

Recognition of environmental factors has an important role in the success of medicinal plants cultivation. Growth-promoting bacteria, through their effects on biosynthesis cycles, cause changes in plant products. In ord levels of control (field capacity), 20% FC, 40% FC, 60% FC and 80% FC. Characteristics such as plant height, , number of leaves, leaf area fresh and dry weight of the shoot, as well as essential oil percentage and and analyzed by GC/MS yield were measured. The results showed with increasing the drought stress the growth and yield in basis decreased. But inoculation of plants with PGPR increased the growth under drought stress conditions and improved the plant performance in such conditions. The highest fresh and dry weight of shoot was in inoculated plants and irrigation control (FC) treatment and the least amount of these traits were obtained in non-inoculated plants and 20% FC treatment, these traits were reduced by 50% and 70%, respectively, compared to plants inoculated with bacteria and FC irrigation. Also, the highest percentage of basil essential oil was obtained in bacteria inoculated plants and 40% FC treatment. The highest yield of essential oil was observed in the control treatment and the effect of the bacteria was not observed. The use of growth-promoting rhizobacteria (PGPR) can improve the production of medicinal plants in environmental stresses such as drought stress and greatly repair the effects of this stress.