Anti-GLRaV-1 monoclonal antibody, clone 5B7/E23

Among the main pathogens infecting temperate fruit trees are Prune dwarf virus, Apple mosaic virus and Grapevine leafroll-associated virus I. In this work the detection and molecular characterization of the coat protein genes of isolates from these viral species were carried out. Total RNA was extracted from peach, apple and grapevine leaves and RTPCR reactions were performed using specific primers to each virus. The amplified cDNA fragments were cloned and sequenced. High identities were observed between coat protein nucleotide sequences of Brazilian isolates of PDV, ApMV and GLRaV-1 and isolates from other countries, independently from geographic origin and host. Coat protein molecular weights of these viruses were estimated by Western blot to be ca. 24kDa (PDV), 26kDa (ApMV) and 39kDa (GLRaV-1).

A great number of grapevine varieties (734) belonging to the different classes of the Vitaceae family (American and Asian Vitis, Vitis vinifera, interspecific hybrids) was screened to identify sources of resistance to fanleaf degeneration (GFLV and ArMV) and to leafroll disease (GLRaV-1 and 3). Special attention was paid to Middle Eastern Vitis vinifera sources due to the possibility that GFLV and V. vinifera evolved together in the Middle East. Inoculation was by green grafting. As the inoculation conditions were difficult to control, we considered a variety to be susceptible if the virus was found in at least one graft. That was true for all varieties for which the graft with a GFLV or GLRaV inoculum had been successful. It appeared to be more difficult to inoculate ArMV, possibly because the grapevine is not the principal host of this virus. In fact, it seems that this inoculation technique is not suitable for this type of investigation. On the one hand, the inoculation pressure is too strong. On the other hand, as the virus is in direct contact with the vessels, the technique does not allow to identify resistances that might occur in the first stage of a natural infection.