Mitigation of drought stress in wheat (Triticum aestivum L.) by inoculation of drought tolerant Bacillus paramycoides DT-85 and Bacillus paranthracis DT-97

Drought as an environmental stressor poses threat to crop yields and consequently jeopardizes agricultural sustainability. Microbes harboring in the roots of native plants having ability to promote plant growth can offer a promising tool to combat the drought stress in plants. In this context, drought tolerant Bacillus strains were isolated from the rhizospheric soils from hot arid regions of Jaisalmer district of Rajasthan, India. On screening 120 isolates, two isolates DT-85 and DT-97 identified as Bacillus paramycoides and Bacillus paranthracis, respectively, using 16S rRNA gene sequencing, showed tolerance to high osmotic stress (10–30% polyethylene glycol 6000), salinity (5–15%), and temperature (45°C). Strain DT-97 exhibited efficient plant growth promoting traits such as production of (1) phosphate, (2) siderophores (SPI 2.93), (3) exopolysaccharide (216–244%), (4) indole-3-acetic acid (49–59%), (5) ammonia, and (6) gibberellic acid (110.5%) in comparison to strain DT-85 under both normal watered and drought stress conditions. Drought stress conditions reduced the root-shoot length, leaf area, and chlorophyll content of wheat crops on inoculation of B. paramycoides DT-85 and B. paranthracis DT-97 resulted in mitigation of drought stress by enhanced production of drought combating molecules like superoxide dismutase, peroxidase, catalase and proline. B. paranthracis DT-97 showed better plant growth promoting attributes and thus can be a used as a bioinoculant for mitigating drought in wheat crop.