Virus survey and sanitation for the recovery of ancient autochtonous Apulian grapes

In the frame of the Apulian Regional project Re.Ge.Vi.P. (“Recovery of Apulian grape germplasm”), in which 152 ancient autochthonous grape biotypes and cultivars were identified, a survey was conducted to assess the presence and incidence of eight viruses regulated in the Italian certification system: Grapevine virus A (GVA), Grapevine virus B (GVB), Grapevine leafroll-associated virus-1, -2, -3 (GLRaV-1, -2, -3), Grapevine fanleaf virus (GFLV), Grapevine fleck virus (GFkV) and Arabis mosaic virus (ArMV). Dormant canes from 80 table and wine grape accessions were ELISA-tested prior to their introduction in a repository of Apulian native germplasm. A great deal (85%) of the tested mother plants resulted positive for single or multiple infections. GLRaV-3 was the most represented virus (71.3%), followed by GFkV (45%) and GVA (42.5%). The presence of infectious degeneration agents was limited to GFLV (28.8%). GLRaV-1 was detected in 22.5% of the vines, whereas other viruses had either a low incidence (GLRaV-2) or were absent (GVB, ArMV). Infected accessions were submitted to sanitation, through in vitro meristem tip culture, in combination with heat therapy. To test the efficacy of virus elimination, a pool of 119 plantlets, deriving from micropropagation of treated explants was analysed by RT-PCR. Successful virus elimination occurred in 79% of the sanitized plants. GFLV and GFkV, which were both still present in eight treated explants, and GVA, were the viruses most recalcitrant to eradication. Results of this study allowed the addition of a number of minor autochthonous grape cultivars to the Apulian grapevine germplasm collection, thus contributing to the conservation of the hitherto neglected agro-biodiversity of Apulia