Plant Growth-Promoting Bacteria Improve Growth and Modify Essential Oil in Rose (Rosa hybrida L.) cv. Black Prince

Abstract

Rose essential oil is rich in compounds widely used by the pharmaceutical and cosmetic industry, due to the biological activities it presents. However, obtaining oil is costly, as the yield per plant is low, which requires several techniques that aim to increase its production. The application of growth-promoting bacteria has been studied for this purpose. Thus, the objective of this work was to select efficient bacteria for production and evaluate their influence on the phytotechnical characteristics and composition of the essential oils of roses. Seven species of bacteria were evaluated for the potential to promote growth in vitro, being tested for nitrogen fixation, phosphate solubilization, protease production and auxin production. From bacteria tested, four were selected and inoculated on rose plants of cultivar Black Prince to evaluate the influence on phytotechnical variables of flower and stem and the oil production. The evaluation of the production of roses was performed through the characteristics of the flowers (size, weight, and diameter of the stem) and floral bud. The essential oils from the inoculated flowers were extracted and evaluated in terms of content, yield, and chemical composition. The application of B. acidiceler, B. subtilis and B. pumilus resulted in flowers with a diameter up to 29% larger. The floral stem was increased by up to 24.5% when B. acidiceler and B. pumilus were used. Meanwhile, the stem diameter was around 41% greater in the presence of B. acidiceler, B. subtilis and in the control. Bacillus pumilus also increased the weight of fresh petals (104%) and essential oil yield (26%), changing the chemical composition of the extracted essential oil. Thus, it is concluded that B. acidiceler, B. pumilus, and B. subtilis improved the phytotechnical characteristics of roses. Among bacteria, B. pumilus increased the essential oil content as well as positively changed the chemical composition of the extracted essential oil.