Study of Plant Growth Promoting Effects by a Phosphate Solubilizing Acinetobacter sp Strain AM1(OR430119.1) on Vigna radiata

Ahana Mondal¹, Manasi Upadhyay¹ and Biswajit Saha^2*

¹Department of Microbiology, University of Calcutta, Ballygunge Campus,West Bengal,India.

²Department of Microbiology, Bijoy Krishna Girls’ College, Howrah, West Bengal, India.

Corresponding author Email:biswajit.saha1402@gmail.com

Abstract:

In agricultural soils, soil salinity and low phosphorus availability due to frequent precipitation of phosphorus into insoluble complexes lead to unsustainable reliance on chemical fertilizers to grow crops.  This degrades soil quality over time and thus presents significant challenges to agriculture. This study deals with the isolation and characterization of a salt-tolerant, phosphate-solubilizing bacterium from the naturally saline soil in Canning, West Bengal, India, to evaluate its potential as an eco-friendly biofertilizer for stress-affected crops in such adverse soils. This study aims to isolate and characterize such high efficiency PSB from soil that can serve as a biofertilizer.Taxonomic identification via phenotypic, and 16S rRNA sequencing classified the isolate as Acinetobacter sp. AM1 (NCBI Accession: OR430119.1). Quantitative analysis revealed that the bacterium is a phosphate solubilizer. Soluble phosphate concentrations in the culture medium increased significantly from 5.02±0.9 μg/ml on day 1 to 42.37±0.11 μg/ml by day 5 post-inoculation. The strain also exhibited tolerance to salinity (up to 3% NaCl), reducing residual sodium ions in the medium from 10.015 g/l to 9.350 g/l through cellular uptake. Physiological profiling demonstrated that the bacterium also synthesizes 0.16 mg/ml of the indole acetic acid (IAA) — a phytohormone that helps in plant growth. To evaluate plant growth promoting capacity, a 25-day pot experiment was conducted with green gram (Vigna radiata) seeds using sawdust, cow dung, and combined matrices as bacterial carriers Furthermore, bio-inoculated soil enhanced chemical fertility, increasing soil nitrogen by 9.51%, potassium by 12.52%, and phosphorus by 25% relative to the uninoculated control. This study, thus by statistical validation of improved plant biomass and soil macronutrient profiles, proves that Acinetobacter sp. AM1 has clear potential as a functional biofertilizer for sustainable agriculture in saline, soluble phosphate-poor soil. Under standard and saline (3% NaCl) soil conditions.

Keywords:

A. oleivorans; Bio-inoculants; IAA; Nutrient solubilizers; NPK; PGP; 16s rRNA

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