FURTHER EVIDENCE THAT THE VITOPINE-TYPE PTIS OF AGROBACTERIUM-VITIS REPRESENT A NOVEL GROUP OF TI PLASMIDS

To study the incompatibility properties of the vitopine Ti plasmids of Agrobacterium vitis, pPM739 containing the cloned ori region of pTiS4 was introduced by triparental mating into seven Agrobacterium tumefac iens strains carrying incRh-1, incRh-2, and incAg-1 plasmids and into eight A. vitis strains, All strains containing pPM739 retained their o riginal plasmids and virulence or the ability to grow on tartrate, exc ept for the three vitopine strains S4, Sz1, and NW11, Furthermore, pTi S4 was stably maintained in S4 cells following introduction of the ori /inc clones of the incRh-1, incRh-2, and incRh-3 plasmids, These resul ts show that vitopine Ti plasmids represent a novel incompatibility gr oup for which we propose the name incRh-4.