Construction of a derivative of Agrobacterium tumefaciens C58 that does not mutate to tetracycline resistance

Agrobacterium tumefaciens C58 mutates to tetracycline resistance at high fr equency, complicating the use of many broad-host-range cloning and binary v ectors that code for resistance to this antibiotic as the selection marker. Such mutations are associated with a resistant gene unit, tet(C58), that i s present in the genome of this strain. By deleting the tet(C58) locus, we constructed NTL4, a derivative of C58 that no longer mutates to tetracyclin e resistance. The deletion had no detectable effect on genetic or physiolog ical traits of NTL4 or on the ability of this strain to transform plants.