First Paragraph: Among the virus-like agents which cause disease in grapevines are several which produce latent or non-symptomatic infections in Vitis vinifera. Research suggests that the severity of disease may vary according to the genotype of the rootstock which is grafted with infected scion wood. This may explain the reports of virus-like diseases which have been observed in California in vineyards where certified rootstock has been grafted with non-certified scion wood selections which appeared disease free when grafted on AXR#1.
