Incidence of virus infection in old vineyards of local grapevine varieties from Majorca: implications for clonal selection strategies

Three autochthonous grapevine varieties of Majorca (Spain) were analyzed for the presence of viruses listed by the international certification programs. Enzyme-Linked Immuno-Sorbent Assay (ELISA) screenings were performed in 193 vines from 46 vineyards included in a clonal selection. Virus-free vines were only 6.4%, 9.6% and 11.5%, in Manto Negro, Callet and Moll, respectively. Infections by grapevine leafroll associated viruses (GLRaVs) were ascertained in 71%, 78% and 60% of Manto Negro, Callet and Moll vines, respectively. Each variety was also highly infected by Grapevine fanleaf virus (GFLV) and Grapevine fleck virus (GFkV). The percentage of plants displaying multiple infections was 58.4% in Manto Negro, 63.8% in Callet and 42.6% in Moll. Thus, it was very difficult to identify virus- free clones with suitable agronomic characteristics to be considered as a reference for the grape market. In order to obtain certified propagation material under such conditions of endemic viral infection, sanitation should be the main focus in clonal selection processes. However, the time and financial requirements for proper sanitation process bring to consideration the need to use, at least temporarily, standard multiplication material while certified clones are achieved.