Evidence that the Closteroviruses GLRV-1 and GLRV-3 are causal agents of grapevine Leafroll disease

Young grapevine plants originated from virus-free clones of the cultivars Barbera and Pinot noir and from the hybrid LN-33 were inoculated by green grafting with grape sources infected only with grapevine leafroll-associated closterovirus 1 (GLRaV-1) or GLRaV-3. Green grafting was successful in most cases, and both GLRaV-1 and GLRaV-3 were capable of causing leafroll symptoms in inoculated vines. It is concluded that the 2 viruses found in northern Italy can be considered as causal agents of the grapevine leafroll disease and can be named "grapevine leafroll virus 1" and "grapevine leafroll virus 3", respectively.