抄録
Pseudomonas protegens, a member of the P. fluorescens complex, is a key biocontrol bacterium with well-documented potential to protect plants against diverse pathogens. Although P. protegens strains have been widely examined globally, those originating from Japan have not been well described. In this study, we isolated and characterized a new P. protegens strain, GSF-73, from the rhizosphere of Allium fistulosum in Gifu, Japan, and assessed its performance against several major plant diseases. Draft genome sequencing produced a 7.13-Mbp assembly, and average nucleotide identity values of 97.81–98.26% with reference strains (Cab75, CHA0, and Pf-5) confirmed its species identity. A comparative genomic analysis showed that GSF-73 possessed a larger genome than the reference strains, containing eight conserved biosynthetic gene clusters for antimicrobial compounds and an expanded set of strain-specific genes related to metabolism, regulation, mobilome functions, and secretion. GSF-73 exhibited broad-spectrum antagonistic activity in vitro against fungal, oomycete, and bacterial pathogens. In biocontrol assays, GSF-73 significantly suppressed spinach Fusarium wilt, cucumber anthracnose on detached cotyledons, tomato bacterial wilt, and cucumber downy mildew. In contrast, root and/or seed treatments enhanced Pythium root rot in spinach and anthracnose in pot-grown cucumbers, indicating pathosystem-dependent efficacy. Despite these contrasting outcomes, GSF-73 shows strong biocontrol potential and merits further study to elucidate the mechanisms underlying both beneficial and adverse effects for its optimized use as a locally adapted biocontrol agent for Japanese agriculture.
