First Detection of Crown Gall Disease on Florida Hopbush Caused by Agrobacterium tumefaciens in Italy

During the period from 2008 to 2011, symptoms similar to crown gall disease have been detected in potted Dodonaea viscosa cv. ‘Purpurea’ plants in several nurseries located in Catania province (Italy). Gram-negative bacteria were consistently isolated from gall tissues taken from diseased plants and identified through cultural, biochemical and molecular tests. The obtained isolates were oxidase positive, non-fluorescent on King’s B medium, utilized mannitol, and were able to grow at 37°C and on nutrient agar containing 2% NaCl. Based on the nutrient profiles revealed by the BIOLOG system, the isolates were identified as Agrobacterium tumefaciens with a probability of 99% and a similarity of 0.61. Furthermore, genomic amplifications were performed by PCR on DNA extracted from representative isolates, with a couple of primers targeting sequences of the Ti plasmid located within the virD region. To our knowledge, this is the first report of occurrence and outbreak of a crown gall disease caused by A. tumefaciens on D. viscosa.