Changes in Enzymatic and Non-Enzymatic Defence Systems Induced by ACCd Producing PGPR Aid Sunflower Plants to Tolerate Drought Stress

Author(s): Brijesh Singh, S., Gowtham, H.G., Mohammed Aiyaz, *Niranjana, S.R.

Abstract: The enzyme 1-aminocyclopropane-1-carboxylate deaminase (ACCd) has been spotted in a limited number of bacteria and plays an important role in supporting plant growth and development under abiotic stress conditions by limiting the production of ethylene in plants. In the present study, ACCd producing PGPR were screened for their plant growth promoting properties in sunflower upon induction of drought stress. Among the ten isolates, Bacillus thuringiensis Rhizo SF 23 and Bacillus subtilis Rhizo SF 48 were able to tolerate a maximum PEG 6000 concentration with an IC50 value > 10. The ACCd producing PGPR apart from increasing plant growth promoting properties in sunflower also enhanced the enzymatic (APX and SOD) and non-enzymatic (proline) antioxidants in sunflower upon drought stress induction compared to respective control. The MDA content decreased in ACCd producing PGPR treated sunflower plants, while proline increased their by indicating that the ACCd producing PGPR (Rhizo SF 23 and Rhizo SF 48) were effective in protecting the plants against drought stress induction. Among the two isolates, Rhizo SF 48 was more significant in tolerating the drought tolerance compared to Rhizo SF 23. The study confirms that the ACCd producing PGPR possessed the ability to improve plant growth parameters by inducing antioxidant capacity through detoxification of important ROS molecules upon drought stress induction and support in agricultural production as effective bio-inoculants.

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