Bacterial consortium interactions in changing climate for mitigating abiotic stress in summer mungbean
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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 Rhizobium (LSMR-32, LSMR-29, LSMR-52 and LSMR-45) and rhizobacteria (LSMRS-3 and LSMRS-7) possessing plant growth promoting traits to mitigate multiple abiotic stresses (salinity, drought and temperature) in summer mungbean. Single and consortium inoculants were screened for abiotic stress tolerance viz. salinity (0-10% 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 with LSMR-32 with LSMRS-3 (OD600nm≈0.781 and 0.574) and LSMRS-7 (OD600nm ≈0.757 and 0.499) at 45○C under normal vs stressed conditions respectively. Further, consortium of LSMR-32 with LSMRS-3 and LSMRS-7 also possessed multiple plant growth promoting traits viz. indole acetic acid (9.92, 7.89 and 7.19 μgml-1) and (9.62, 7.26 and 7.92 μgml-1), phosphate solubilization (6.234, 3.321 and 2.258 mg100 ml-1) and (6.187, 3.001 and 2.508 mg100 ml-1); 1-aminocyclopropane-1-carboxylate deaminase (OD600nm ≈0.4402, 0.5964 and 0.5386) and (OD600nm ≈ 0.5436, 0.5209 and 0.5006) respectively under normal, induced salt and drought stress. 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. Field 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 summer mungbean revealed improvement in all parameters over un-inoculated control. Higher amount of antioxidant enzymes viz .superoxide dismutase (26.03 μmol O2 mg-1 protein-1), catalase (13.14 H2O2 mg-1 protein), peroxidase (5.62 H2O2 min-1mg-1protein) and osmolyte proline (14.61 μgml-1) were noticed with LSMR-32+LSMRS-3 in induced drought stress over control treatment. Combination of Rhizobium LSMR-32 with rhizobacteria LSMRS-3 increased grain yield by 1.29 fold in comparison to un-inoculated control. Present study highlights the role of consortium treatment of Rhizobium and rhizobacteria in ameliorating the oxidative damage induced by drought stress in summer mungbean.