Research Notes Diverse Types of Tartrate Plasmids in Agrobacterium tumefaciens Biotype III Strains. Ernö Szegedi. Research Institute for Viticulture and Enology, P.O. Box 25, 6000 Kecskemét, Hungary. Léon Otten(2), and Mihály Czakó(3,4). (1)Research Institute for Viticulture and Enology, P.O. Box 25, 6000 Kecskemét, Hungary; (2)Institute of Plant Molecular Biology, 12, Rue du Général Zimmer, 67084 Strasbourg, France; (3)Biological Research Center of the Hungarian Academy of Sciences, Institute of Plant Physiology, P.O. Box 521, 6701 Szeged, Hungary; (4)University of South Carolina, Department of Biological Sciences, Columbia, SC 29208, U.S.A. MPMI 5:435-438. Accepted 14 May 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992.

Twelve biotype III isolates of Agrobacterium tumefaciens that belong to three opine types were mated in planta with a plasmid-free biotype I recipient strain. When selection for tartrate utilization was imposed, seven of the 12 mating combinations resulted in transconjugants. In six combinations, large plasmids were transferred from the donor strains capable of tartrate utilization. In four of the six combinations, the transferred plasmids could be distinguished from the Ti plasmids and were named Tr plasmids. Tr plasmids form a diverse group; they differ in size, transfer frequency, and stability in a biotype I chromosomal background, and three of them were self-conjugal.