Effect of Hot Water Treatment on Systemic Agrobacterium tumefaciens Biovar 3 in Dormant Grape Cuttings. T. J. Burr, Department of Plant Pathology, Cornell University, Geneva, NY 14456. K. Ophel, B. H. Katz, and A. Kerr. Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064; Department of Plant Pathology, Cornell University, Geneva, NY 14456; and Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064. Plant Dis. 73:242-245. Accepted for publication 31 October 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0242.

Agrobacterium tumefaciens biovar 3 (AT3) was eradicated or reduced to below the level of detection in dormant cuttings of grape rootstocks K5140 (Vitis champinii × V. riparia) and Ramsey (V. champinii) and in artificially infested Cayuga White (interspecific hybrid) by a hot water treatment (exposure to 50 C for 30 min). Strains of AT3 varied in their sensitivity to heat, but were generally more sensitive than strains of biovar 1 or biovar 2. Populations of about 10³ colony-forming units per milliliter of AT3 in broth were killed by a 30-min treatment. Biovar 1 strains were apparently unaffected by 50 C, even when exposed for 30 min. Nontumorigenic biovar 1 strains were recovered from hot water treated cuttings. The hot water treatment may offer a simple, effective, economical, and environmentally safe means of eradicating AT3 from dormant cuttings.