Detection of Agrobacterium tumefaciens in grapevine cuttings1

Crown gall is the most important bacterial disease of grapevine and is primarily associated with Agrobacterium tumefaciens biovar 3. The systemic distribution of the agrobacteria in grapevine requires the checking of nursery propagation material to reveal their presence in the xylem vessels. The methods adopted to demonstrate systemic survival are quite lengthy and, thus, this study aimed to develop a serological sampling procedure to rapidly detect A. tumefaciens in xylem extracts, obtained by vacuum extraction with suitable washing fluid, from asymptomatic one year‐old dormant grape cuttings. The suspension was centrifuged and the final concentrate used for immunofluorescence staining. The sensitivity threshold of the vacuum washing system and the effectiveness of the detection method were experimentally evaluated. The antiserum specificity was tested in a comparative study with a collection of A. tumefaciens strains from grapevine and other common grapevine contaminants. The vacuum washing system is discussed as an indexing tool in a much hoped for certification programme.