Herbicidal Control Potential of the Endophytic Bacterium B. pseudorignonensis BFYBC-8 Isolated from E. crus-galli Seeds

The long-term application of traditional chemical herbicides has caused a significant escalation in herbicide resistance of barnyard grass (<i>Echinochloa crus-galli</i>). As an eco-friendly alternative, biological herbicides demonstrate substantial application potential. Acknowledging the growing herbicide resistance of <i>E. crus-galli</i>, this study aimed to screen target bacteria with inhibitory effects on the growth for bio-herbicide development. By using ungerminated <i>E. crus-galli</i> seeds as the screening substrate, a bacterial strain (BFYBC-8) with potent inhibitory activity was isolated and identified as <i>Brucella pseudorignonensis</i>. Pot experiments revealed that inoculation with <i>B. pseudorignonensis</i> BFYBC-8 significantly suppressed <i>E. crus-galli</i> growth, reducing plant height by 16.7% and root length by 85.1%, while markedly inhibiting biomass accumulation. Fluorescent labeling with green fluorescent protein (GFP) showed that BFYBC-8 successfully colonized the root intercellular spaces of <i>E. crus-galli</i> and extended continuously along the tissue matrix. Additionally, the strain's supernatant metabolic products exhibited exceptional thermostability: inhibitory activity against <i>E. crus-galli</i> was maintained after thermal treatment at 28 °C, 60 °C, 80 °C, and 100 °C. Crucially, the bacterium displayed no toxicity to agronomically important crops such as rice, wheat, and corn. This study highlights <i>B. pseudorignonensis</i> BFYBC-8 as a promising candidate for bioherbicide development and provides an important reference for applying seed-associated pathogenic bacteria in developing bioherbicides for sustainable weed management.