Genomic identification and pathogenicity of Ralstonia pseudosolanacearum MSG-1 isolated from mulberry tree in China

Strain MSG-1 was isolated from diseased mulberry branches collected in Nanning (Guangxi Province, China) for pathogenicity characterization. Through molecular biology techniques and pot experiments, the strain MSG-1 was identified and designated as Ralstonia pseudosolanacearum MSG-1, which can cause whole-plant disease and belongs to race 5, biovar I, phylotype I and sequevar 12. The complete genome assembly of R. pseudosolanacearum MSG-1 (5.8 Mbp, 66.85% GC) was organized into a tripartite structure comprising one chromosome, one mega-plasmid and one small plasmid. A total of 1,991 genes of R. pseudosolanacearum MSG-1 were found to be significantly differentially expressed (|log2(FC)|>1, FDR<0.05) during the infection of mulberry seedlings, with 1,324 genes significantly up-regulated and 667 genes significantly down-regulated. Integrated analysis of the pathogen genome and host-pathogen interaction transcriptomics revealed seven pathogenicity-associated candidate genes. Through gene knockout experiments and assessments of pathogenicity-associated phenotypes in the mutants, it was confirmed that the genes OUY08_21705, OUY08_17745, OUY08_17805, OUY08_26440, OUY08_01115 and OUY08_13190 play crucial roles in the pathogenicity of R. pseudosolanacearum MSG-1. This study integrates genomic insights with pathogenicity mechanisms of R. pseudosolanacearum MSG-1, providing an experimental foundation for accelerating the breeding of mulberry-resistant varieties and precision-based wilt control in sericulture.