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2011 APS Annual Meeting Abstract


Evaluations and modifications of semi-selective media for improved isolation of Agrobacterium tumefaciens biovar 1 from cultivated walnut
L. E. YAKABE (1), S. R. Parker (1), D. A. Kluepfel (1)
(1) USDA, Agricultural Research Service, Crops Pathology/Genetics Research Unit, Davis, CA, U.S.A.
Phytopathology 101:S196

Agrobacterium tumefaciens, the causal agent of crown gall of walnut, is an aerobic, Gram negative bacterium belonging to the family Rhizobiaceae. Like many in this group, A. tumefaciens is a common inhabitant of soil and plant host tissue. Isolation from these complex environments is difficult even with the use of semi-selective media. Many semi-selective media have been developed for A. tumefaciens and more recent studies of Agrobacterium species have relied on the medium1A. In this study, six previously published semi-selective media were evaluated using a panel of A. tumefaciens biovar 1 and closely related Rhizobiaceae species isolated from walnut orchards in California. Based on the antibiotic and carbon-utilization profiles of twelve A. tumefaciens isolates, D1 and 1A recipes were modified by antibiotic amendment or substitution of the primary carbon source to increase isolation efficiencies and/or selectiveness out of a complex environment. The antibiotics ampicillin, trimethoprim, and vancomycin were evaluated in addition to the carbon sources proline, serine, theonine, and β-hydroxybutyric acid. Results from these experiments revealed significant variation in isolation efficiency within a genetically diverse group of A. tumefaciens isolates and allowed development of a more selective medium for diagnostics and quantification from soil.

2011 by The American Phytopathological Society. All rights reserved.