Genomic and Phylogenetic Characterization of Eight Novel Ralstonia solanacearum Strains Associated With Potato Brown Rot in Georgia

Ralstonia solanacearum is a soil‐borne, Gram‐negative bacterial pathogen that causes bacterial wilt in a wide range of economically important crops. In Georgia, potato production is increasingly threatened by the emergence of aggressive R. solanacearum strains. In this study, we performed whole‐genome sequencing and comparative genomic analyses of eight R. solanacearum strains (GEO_6, GEO_55, GEO_57, GEO_81, GEO_96, GEO_99, GEO_230, and GEO_304) collected from infected potato plants in Georgia. Phylogenetic relationships were inferred using 16S rRNA, the endoglucanase ( egl ) gene, and whole‐genome single‐nucleotide polymorphism (SNP) analyses, complemented by average nucleotide identity (ANI) comparisons. All Georgian strains clustered within phylotype IIB‐1 and exhibited high genomic similarity to strains IPO1609, UY031, RS2, UW551, POPS2, NCPPB_282, and 23_10BR. Comparative analysis of type III effector repertoires revealed a conserved core set of effectors across the Georgian strains, accompanied by lineage‐specific gene losses, pseudogenization, and copy‐number variation. Pan‐genome analysis of 24 R. solanacearum strains demonstrated a highly conserved core genome comprising 2378 gene clusters, while Georgian strains exhibited a markedly reduced cloud genome. Collectively, these findings indicate that the Georgian strains represent a distinct phylotype IIB‐1 lineage of R. solanacearum and provide new insights into the genomic evolution and epidemiology of this important plant pathogen.