Paenibacillus polymyxa Role Involved in Phosphate Solubilization and Growth Promotion of Zea mays Under Abiotic Stress Condition

This investigation is aimed to analyse in vitro phosphate solubilization activity of Paenibacillus polymyxa under abiotic stress condition and their growth promotion potential on maize ( Zea mays ) seeds including the abilities to antagonize phytopathogens. Performance of this strain is greatly influenced to fix available phosphorus, making it essential to ascertain this strain for improving phosphate-solubilizing ability and alleviating the extreme environmental condition effects. In this study, P. polymyxa was screened on the basis of phosphate-solubilizing bacteria using PVK agar, inorganic phosphate and tricalcium phosphate {Ca 3 (PO 4 ) 2 } in order to detect the presence of halo zone, indicating the solubilization occurrence. The strain also exhibited the ability to solubilize the phosphate in varying pH treatment (5–9), temperature (25–35 °C) and heavy metal tolerance (0.02–0.05 M Ni and Zn). The maximum phosphate-solubilizing activity was found to be 2635.3 μg ml −1 after 5 days of incubation with the decrease in pH of the medium from 6.08 to 3.28. The effect of the strain on growth of maize seedlings and its other promoting attributes (cell wall-degrading enzymes, N 2 fixation ability and biocontrol activity against Fusarium oxysporum and Botrytis cinerea ) were studied. Remarkably, the strain P. polymyxa inoculant resulted in almost twofold greater in fresh weight and shoot length of maize seedlings as compared to others. Paenibacillus polymyxa strain used in this study showed efficient phosphate mineralizing and solubilization ability with the view of utilizing them as inoculant sources in correspondence to boost the fertility of soils.