Crown and cane gall of a blackberry-raspberry hybrid caused by Agrobacterium rhizogenes in Northern Italy

During a serious epidemic of crown and cane gall on the blackberry-raspberry hybrid Lockness in a specialized crop in the province of Treviso, Gram-negative bacteria were found associated with tumours. Following experimental inoculation these bacteria caused tumours on tomato stems and on the pot-grown hybrid canes in the greenhouse. These tumourogenic bacteria were found to possess the vir D2 gene, common to Ti and Ri plasmids. The fatty acid profile did not correspond to any known Agrobacterium species, but indicated an affinity with the genus Agrobacterium. A comparative analysis of the sequences of approximately 700 pb of 16 S DNA revealed that the bacteria had a high affinity with the three strains of Agrobacterium rhizogenes, in particular with a strain isolated from a peach tumour. The phenotype matched that of biovar 2. The associated bacteria that caused the crown and cane gall epidemic was identified as an unusual strain of Agrobacterium rhizogenes.