Evaluating the Phytohormone Proficiencies of Multifarious Bacillus rugosus for Growth Promotion in Arachis hypogaea (L.).

Abstract

The application of Plant Growth-Promoting Rhizobacteria (PGPR) in agriculture is increasingly emphasized as a sustainable alternative to hazardous agrochemicals. This study aimed to isolate and characterize PGPR strains from the rhizospheric soil of Arachis hypogaea L., hypothesizing that the rhizosphere of a healthy plant harbors beneficial microbes with significant plant growth-promoting (PGP) attributes. The isolate AB1 demonstrated promising PGP traits, including phosphate solubilization (56.44 µg mL⁻¹), zinc solubilization (6.1 µg mL⁻¹), ammonia production (3.8 µM µg mL⁻¹), and the synthesis of hydrogen cyanide (HCN) and phytohormones. Objectives included identifying these traits and evaluating their impact on the growth of Arachis hypogaea L. Phytohormonal profiling of AB1 through Gas Chromatography-Mass Spectrometry (GC-MS) and Fourier Transform Infrared Spectroscopy (FTIR) confirmed indole fractions with characteristic peaks at 3338 cm⁻¹ (N-H stretching), 1641 cm⁻¹ (C-N bond of the indole ring), and 2984 cm⁻¹ (C-H aromatic stretching). Cytokinins and gibberellins were also detected. Molecular, physiological, and biochemical analyses identified the isolate as Bacillus rugosus AB1, with gene sequences deposited under GenBank accession number MZ373174. The present study is the first report of Bacillus rugosus AB1 as a PGPR, showcasing multifaceted PGP traits that significantly enhanced root and shoot growth, biomass, and chlorophyll content in Arachis hypogaea L., demonstrating its potential as a biofertilizer for sustainable agriculture.