Development of plant growth promoting microbial consortium for alleviating abiotic stress in soybean

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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
The present study was aimed to screen consortium of authenticated Bradyrhizobium sp. (LSBR-3) and rhizobacteria (LSE-1, LSE-2, LSE-3 and LSE-4) possessing plant growth promoting traits to mitigate concerted abiotic stresses (salinity, drought and temperature) in soybean. Single and consortium inoculants were screened for abiotic stress tolerance viz. salinity (0-25% NaCl), drought (Polyethylene glycol (PEG 0-30%) and temperature (28, 37°& 45°C) in terms of growth by spectrophotometer and agar plate assay. Maximum growth of all treatments was observed at 5% each of NaCl and PEG (6000). Single and consortium inoculants exhibited luxuriant growth at 28° and 37°C.Whereas, sharp decline was noticed at 45°C. In concerted stress, dual inoculants revealed higher growth over single inoculant and maximum growth was observed in LSBR-3 with LSE-3 (OD600nm 0.737 and 0.858) and LSE- 1 (OD600nm 0.676 and 0.688) at 45°C under normal vs stressed conditions respectively. Further, consortium of LSBR-3 with LSE-3 and LSE-1 also possessed multiple plant growth promoting traits viz. indole acetic acid (12.62, 6.65 and 6.96 μgml-1) and (13.95, 6.34 and 7.78 μgml-1), phosphate solubilization (10.09, 6.91 and 7.83 mg/100ml) and (10.33, 7.01 and 10.36 mg/100ml); 1-aminocyclopropane-1-carboxylate deaminase (OD600nm 0.3062, 0.6449 and 0.6081) and (OD600nm 0.3197, 0.6271and0.5871) respectively under normal, induced salt and drought stress at 45°C. At 45°C highest biofilm formation and total soluble sugars was noticed with NaCl and PEG treated dual treatments upto 24 h of incubation. Induced salinity and drought enhanced proline content of dual inoculants over control treatment. Greenhouse experiment conducted for normal and induced drought stress conditions with different abiotic stress tolerant consortium inoculants for growth, symbiosis, nutrient acquisition, antioxidants and yield in soybean revealed improvement in all parameters over un-inoculated control. Higher amount of antioxidant enzymes viz .superoxide dismutase (26.21μmol O2 mg-1 protein-1), catalase (12.01H2O2 mg-1 protein), peroxidase (0.315min-1mg-1) and osmolyteproline (7.81μgml-1) were noticed with LSBR-3+LSE-3 in induced drought stress over control treatment. Under stressed conditions, 1.5 and 2.9 folds enhancement in grain yield was observed with consortium of Bradyrhizobium sp. LSBR-3 with rhizobacteria LSE- 3, as compared to rhizobacterium single inoculants LSE-3 and control respectively. Present study highlights the role of consortium treatment of Bradyrhizobium sp. and rhizobacteria in ameliorating the oxidative damage induced by drought stress in soybean.
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