Anti-GFKV monoclonal antibody, clone 7E5/G7

A survey of grapevine viruses present in the region of Calabria (southern Italy) was carried out, and the sanitary selection was conducted on various indigenous varieties. Serological (ELISA) and molecular (multiplex RT-PCR) tests were used to detect the viruses included in the Italian certification programme: Arabis mosaic virus (ArMV), Grapevine fanleaf virus (GFLV), Grapevine leafroll associated virus 1 (GLRaV-1), Grapevine leafroll associated virus 2 (GLRaV-2), Grapevine leafroll associated virus 3 (GLRaV-3), Grapevine virus A (GVA), Grapevine virus B (GVB) and Grapevine fleck virus (GFkV). The frequency with which the above viruses have been detected was 37.4, 32.6, 12.8, 7.7, 7.3, 1.9 and 0.3%, respectively, for GVA, GLRaV-3, GFLV, GFKV, GLRaV-1, GLRaV-2 and GVB. ArMV was never found. The sanitary selection allowed for the detection of 6 putative clones of Arvino', 2 of Magliocco dolce' and 2 of the rootstock 17-37' free of the above-mentioned viruses. The necessary process for the commercialization of these clones as certified' propagation material was accomplished, and their official approval by the Italian Ministry of Agriculture is currently in progress.

Infection of French-American hybrid grapevines by GLRaV-3 is latent, and information about the impact of the virus on the performance of these cultivars is scarce. This study compares several performance indices between Vidal blanc and St. Vincent grapevines that were naturally infected and those free of GLRaV-3. Virus infection did not affect grapevine vigor, but was linked to an approximately 5% reduction (p < 0.001) in average berry weight in both cultivars. Titratable acidity was 5 and 9% higher (p < 0.001) in the fruit from virus-positive St. Vincent and Vidal blanc grapevines, respectively, three to seven days prior to harvest. Also included in the study were Vidal blanc plants naturally infected by GLRaV-3 and grapevine fleck virus (GFkV). Plants with both viruses had a 7% reduction in average berry weight and titratable acidity levels were 14% higher compared to healthy plants (p < 0.001). Graft-indexing on Vitis vinifera L. cv. Cabernet Franc and Vitis rupestris Scheele cv. St. George indicators produced typical leafroll and fleck symptoms, respectively. These results suggest that latent infections in these French-American hybrid cultivars cannot be attributed to the low virulence of the viral strains, but probably to host tolerance.