Abstract: Agrobacterium strains that harbor transformation-enhancing genes on a plasmid capable of replication independently of the Agrobacterium chromosome, the Ti plasmid, and plant transformation binary vectors, and uses for these Agrobacterium strains are provided. Additionally, Agrobacterium strains that are deficient in DNA recombination functions that result in instability or rearrangement of plant transformation binary vectors, and that harbor transformation-enhancing genes on a plasmid capable of replication independently of the Agrobacterium chromosome, the Ti plasmid, and plant transformation binary vectors, and uses for these strains, are also provided. Further included are Agrobacterium strains that harbor transformation-enhancing genes integrated into the Agrobacterium chromosome at a locus that does not interfere with or otherwise compromise the normal growth and plant transformation ability of the Agrobacterium cells, and uses for these Agrobacterium strains.