Research Institute for Viticulture and Enology, Kecskemét, Hungary; Plant Protection Institute of Hungarian Academy of Sciences, Budapest, Hungary and Department of Plant Pathology, Cornell University, Geneva, NY, USA

The nonvirulent\ antagonistic A`robacterium vitis strain F1:4 was tested for the presence of tartrate utilization plasmid"s# which commonly occur in virulent A[ vitis isolates[ Following transformation of F1:4 plasmidDNA into A`robacterium tumefaciens UBAPF1\ an approxi! mately 119 kbp plasmid coding for tartrate utilization was isolated[ This plasmid\ designated pTrF1:4\ was also transferred by in planta mating between F1:4 and UBAPF1 and was maintained in a stable state in A[ tumefaciens under nonselective conditions[ pTrF1:4 could not be allocated into the known incompatibility groups described so far in A`robacterium[ Two trans! conjugant colonies also acquired an octopine utilization plasmid named pOcF1:4 which is related to the incRh0 Ti plasmids[ Neither pTr nor pOc encodes for the tumour! inhibiting ability of F1:4[