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.