Functional profiling of novel glufosinate ammonium-tolerant, and secondary metabolite-secreting plant growth-promoting rhizobacteria

Abstract

Despite its toxicity, glufosinate ammonium (G-A) remains a popular herbicide. While microbial and plant-based detoxification have advanced, gaps still exist. This study aims to unravel strains with diverse metabolic and biochemical capabilities for G-A degradation. Herein, rhizospheric isolates from non-G-A contaminated sites were assayed for detoxification and plant growth promotion (PGP) using gradient concentration (0.0, 1.0, 1.5, 2.0, and 2.5 mM) over 84-hours. In between, PGP traits, including production of indole acetic acid (IAA), exopolysaccharides (EPS), siderophores, and phosphate solubilization and – secretion of sugars and amino acids were assayed. Six G-A tolerant isolates were identified through 16S rDNA analysis. Inoculation of soybean with cultures (1.4 × 10⁻⁴ CFU/mL, OD₆₀₀ nm) and 2.5 mM G-A treatment (1.0 mL/plant) increased germination (90 %), lengths of radicle (6.6 cm), mesocotyl (4.5 cm), and total fresh weight (1.83 mg) compared to controls (100 %, 7.12 cm, 5.1 cm, and 1.90 mg, respectively), and enhanced catalase, superoxide dismutase and glutathione antioxidants activities by 82, 78, and 60 percent respectively. Soil drench and foliar treatment of isolates and G-A in pot trials showed differential resistance, enhanced biomass, and increased chlorophyll concentration. Phylogenetic analysis revealed significant sequence similarities; OC-1042 to Stenotrophomonas sp. (97.5 %), OC-1054 to Klebsiella penumoniae (99 %), RB-1011, GH-1050, OC-1040 by 100, 99.9, and 99.8 percent respectively to Serratia marcescens, and UF-1050 to Pseudomonas nitroreducens (99.9 %). In conclusion, the diversity of G-A tolerant isolates facilitates detoxification, colonization, plant growth, and resilience. This variation contributes to their adaptability and roles, highlighting a path toward sustainable weed management.