Characterization of Agrobacterium Isolates from Muscadine Grape. K. L. Thies, Research Assistant, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. D. E. Griffin, C. H. Graves, Jr., and C. P. Hegwood, Jr. Postdoctoral Assistant Plant Pathologist, and Professor, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762, and Superintendent, Truck Crops Branch Experiment Station, Crystal Springs, MS 39059. Plant Dis. 75:634-637. Accepted for publication 13 December 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0634.

The systemic presence of a host-restricted strain of Agrobacterium tumefaciens in muscadine grape (Vitis rotundifolia) was confirmed by means of a detached leaf assay procedure using Agrobacterium-free plants. Assays of muscadine plants representing vineyards from throughout the region indicated a widespread systemic presence of A. tumefaciens in roots and vascular fluids of shoots of symptomatic and asymptomatic plants in Mississippi. Not all isolates from muscadine were clearly classified as biovar 1, 2, or 3. Biovar 3 appeared to predominate among isolates from roots and vascular fluids, but the number of biovar 1 and biovar 3 isolates from galled tissues was almost equal. High percentages of biovar 1, biovar 3, and unclassified isolates were pathogenic.

Keyword(s): Vitis vinifera.