Surviving the Potato Stems: Differences in Genes Required for Fitness by and .

Bacteria belonging to the genus cause blackleg and soft rot symptoms on many plant hosts, including potato. Although there is considerable knowledge about the genetic determinants that allow to colonize host plants, as well as the genes that contribute to virulence, much is still unknown. To identify the genes important for fitness in potato stems, we constructed and evaluated randomly barcoded transposon mutant (RB-TnSeq) libraries of and . We identified 169 and 157 genes important for growth in and a in stems, respectively. This included genes related to metabolic pathways, chemotaxis and motility, transcriptional regulation, transport across membranes, membrane biogenesis, detoxification mechanisms, and virulence-related genes, including a potential virulence cluster , c-di-GMP modulating genes, and pectin degradation genes. When we compared the results of the stem assay with other datasets, we identified genes important for growth in stems versus tubers and in vitro conditions. Additionally, our data showed differences in fitness determinants for and . These data provide important insights into the mechanisms used by when interacting with and colonizing plants and thus might provide targets for management.