Pseudomonas putidaGR12-2R3 promotes the emergence and growth of diverse plant species. Analyses of TnphoAinsertion mutations are revealing bacterial characteristics pertinent to the plant–microbe interaction.Pseudomonas putidaPG269 is a TnphoAinsertion derivative of GR12-2R3 that expresses canola seed exudate-inducible alkaline phosphatase (PhoA) activity. It promoted the growth of canola roots, as well as strain GR12-2R3, and outgrew its parent when they were cocultured in the presence of canola roots or in liquid seed exudate medium. (In contrast, mutant PG126 failed to promote canola root growth and was outgrown by its parent strain.) The PhoA activity of strain PG269 was induced by glucosamine and other sugars; glucosamine inhibited the growth of strain GR12-2R3 and stimulated the growth of strain PG269. Strain PG269 contained two TnphoAinsertions:seiA1:: TnphoAandseiB1:: TnphoA. Strain PG312, which contained only insertionseiA1:: TnphoA, shared all aspects of the PG269 phenotype, except the ability to outcompete strain GR12-2R3 during coculture. InsertionseiA1::TnphoAinterrupted an open reading frame related in sequence to members of the MalF family of sugar transporter subunits. The PhoA-inducing fraction of canola seed exudate was hydrophilic, low in molecular weight, and heat stable. It cochromatographed with basic amino acids and amino sugars, and was inactivated by strains GR12-2R3 and PG269. GeneseiAmay encode a subunit of an ABC transporter with broad specificity for glucose and related sugars whose expression can be induced by exudate sugars.Key words:Pseudomonas putida, canola, exudate, sugar transport, rhizobacterium.