Plant growth–promoting rhizobacteria are under extensive investigation to supplement the chemical fertilizers due to cost-effective and eco-friendly nature. However, their consistency in heterogeneous soil and diverse ecological settings is unclear. The current study presents in vitro and field evaluation of pre-characterized PGPR strain Enterobacter sp. Fs-11 (GenBank accession # GQ179978) in terms of its potential to enhance sunflower yield and oil contents under diverse environmental conditions. Under in vitro conditions, strain Fs-11 showed optimal growth at a range of temperature (15 to 40 °C) and pH values (6.5 to 8.5). Extracellular and intracellular localizations of the strain Fs-11 in sunflower root cortical cells through transmission electron microscopy confirmed its epiphytic and endophytic colonization patterns, respectively. In field experiments, conducted at three different agro-climatic locations, inoculation of strain Fs-11 at 50% reduced NP fertilizer resulted in a significant increase in growth, achene yield, nutrient uptake, and oil contents. Inoculation also responded significantly in terms of increase in mono- and polyunsaturated fatty acids (oleic and linoleic acids, respectively) without rising saturated fatty acid (palmitic and stearic acids) contents. We concluded that Enterobacter sp. Fs-11 is a potential candidate for biofertilizer formulations to supplement chemical fertilizer requirements of sunflower crop under diverse climatic conditions.
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