Whole-genome sequencing and biocontrol functional analysis of Pseudomonas chlororaphis XZL-8 for controlling poplar canker pathogen Cytospora chrysosperma.

INTRODUCTION

Poplar canker triggered by Cytospora chrysosperma severely damages forest production, and screening efficient antagonistic bacteria is a sustainable strategy for eco-friendly disease management. This study aimed to characterize the taxonomic status, genomic features and biocontrol potential of strain XZL-8.

METHODS

Polyphasic identification and whole-genome sequencing were conducted to confirm the species of strain XZL-8. Functional annotation against NR, COG, GO and KEGG databases and antiSMASH secondary metabolite prediction were carried out to decode its functional genes. A series of in vitro antagonistic experiments, as well as detached branch inoculation assays, were implemented to verify its phenotypic traits.

RESULTS

Strain XZL-8 was classified as Pseudomonas chlororaphis subsp. aureofaciens. A total of 22 secondary metabolite biosynthetic gene clusters were predicted in its genome; the gene clusters encoding hydrogen cyanide and pyrrolnitrin synthesis shared high homology with known reference clusters, with similarity coefficients reaching 0.85 and 0.99, respectively. Phenotypic assays showed that the strain inhibited the pathogen via direct antagonism, extracellular metabolites, and volatile substances. Genomic analysis further uncovered candidate genes linked to plant-beneficial properties such as hydrolytic enzyme production, HCN synthesis, and phosphate solubilization. Detached-branch assays confirmed its promising protective effect against woody stem canker.

CONCLUSION

Strain XZL-8 harbors abundant genetic determinants putatively linked to biocontrol and plant-beneficial traits. In vitro and detached-branch tests demonstrated its biocontrol potential against C. chrysosperma, and therefore it is a promising candidate for developing microbial agents for the management of woody stem canker.