Effect of algae and yeast on the production of essential oil and some active constituents in rosemary

Background Rosemary is an important medicinal plant and one of the main aromatic spices in the world. Nowadays, it is very important to use natural substances such as algae and yeast in the green agriculture to increase quantity and quality of crops, in addition to preserving environment from the harms of using chemicals in the agriculture. Objective The study aimed to investigate growth, yield, and active constituents of rosemary under foliar spraying of different concentrations of both algae and yeast extracts. Materials and methods The experiment was performed during the two successive seasons 2019 and 2020 in completely randomized blocks design and consisted of seven treatments: two biostimulants with three levels of each factor, in addition to the control (tap water). Algae extract was sprayed with concentrations of 0.5, 1, and 2 g/l, whereas yeast concentrations were 5, 10, and 20 g/l. The growth parameters, total phenolics, antioxidant activity, essential oil percentage, yield, and its main constituents were studied. Results and conclusion The main components of essential oil were found to be endo-borneol followed by (+)-2-bornanone. The growth, yield, total phenolics, antioxidant activity, essential oil, and the main components of rosemary increased with all used concentrations of algae and yeast extracts compared with control. These increments reached their maximum with application of algae at 1 and 2 g/l and yeast extract at 10 and 20 g/l. In general, spraying yeast extract resulted in the highest average of growth, yield, and chemical constituents of rosemary, and the best parameters were obtained by spraying yeast at 20 g/l. It is recommended to spray rosemary with yeast extract at a dose of 20 g/l to obtain the best plant herbal yield, essential oil, total phenolic content, and antioxidant activity.