A Complete Genome Resource and Bio-Control Activity of Soil-Isolated Pseudomonas citronellolis Strain M03 Against...

Pseudomonas citronellolis M03 was isolated from the soil of a field, which has been under continuous onion production for approximately 20 years. The soil was naturally infested with onion-pathogenic Burkholderia spp. but over the last 2 years bacterial populations had declined. The genome of the bacterial isolate was sequenced. The average nucleotide identity (ANIm) analysis showed > 97% identity and > 84% alignment coverage with the type strain P. citronellolis DSM50332^T. Digital DNA-DNA hybridization (dDDH) values were 73.6% (formula d4) and 77.8% (formula d0), exceeding the 70% species delineation threshold. The genome comprised of a single 6.73 Mb circular chromosome encoding 5802 coding sequences, including 10 pseudogenes, 428 hypothetical genes, and 81 RNA genes (15 rRNAs, 66 tRNAs). We also identified two NRP-metallophore/NRPS biosynthetic gene clusters showing high similarity to the pyoverdine and enantio-pyochelin clusters of Pseudomonas protegens Pf-5, suggesting the presence of uncharacterized metabolites with potential ecological or biocontrol functions. Phenotypic assays demonstrated strong antagonistic activity of P. citronellolis M03 against Burkholderia cepacia and Burkholderia gladioli in vitro, reducing their populations by > 10-fold and approximately 50%, respectively, after 48 h of co-inoculation. Assessment of onion bulb rot showed significant reductions in both disease incidence and severity when P. citronellolis M03 was co-inoculated with B. cepacia. The ability of P. citronellolis M03 to persist and exert antagonistic effects in complex soil microflora highlights its ecological fitness and adaptability in natural environments. This study provides a valuable genomic resource and experimental evidence for the biocontrol capability of this potentially beneficial bacterium.