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Synergistic Effects of Plant-Growth-Promoting Rhizobacterium and Growth-Regulating Small Molecules on Drought Mitigation and Yield Sustainability of Rice


                                Plant-growth promoting rhizobacteria are considered as eco-friendly andsustainable inputs for providing nutrients and to ameliorate the crops fromabiotic and biotic stresses. The present work was aimed to assess thestimulatory effects of plant growth-promoting rhizobacteria in associationwith plant-growth regulating hormonal small molecules on droughtmitigation and yield of rice. The multifunctional PGPR strain Pseudomonaschlororaphis (ZSB15) was inoculated in rice (cultivar Co51) and assessedits synergistic impacts with three different plant-growth regulating hormonalsmall molecules under field conditions. The cell extracts of Saccharomycescerevisiae, cell extract of Corynebacterium glutamicum, salicylic acid weresprayed on the foliage of rice plant under water-sufficient and water-deficitconditions. Application of cell extracts of Corynebacteria as a foliar spray atthe seedling stage and the panicle initiation stage significantly combat thedrought-induced physiological stresses of rice. It reduced the mean canopytemperature (10%), catalase activity (21%) and proline content (13.6%) of ricecompared to water-sprayed control under water-deficit condition. The sprayof the cell extract of Corynebacteria also improved the relative water content(15%) of the rice as compared to control under water-deficit conditions. Italso improved the yield attributes and yield of rice both under water-sufficientand water-deficit conditions. The cell extract of yeast and salicylic acid areat par performance and relatively lower than Corynebacterial cell extractin terms of drought mitigation and synergistic impacts with PGPR in rice.Hence, combining the plant-growth-promoting rhizobacteria and plant-growthregulating hormonal small molecules could be a sustainable and profitableapproach to increase the drought tolerance in rice to mitigate the yield losses.

Key words : Drought tolerance; PGPR; Proline; Rice; Salicylic acid; Water deficit

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