Evolutionary Analysis of Grapevine Virus A: Insights into the Dispersion in Sicily (Italy)

Grapevine virus A (GVA) is a phloem-restricted virus (genus Vitivirus, family Betaflexiviridae) that cause crop losses of 5–22% in grapevine cultivars, transmitted by different species of pseudococcid mealybugs, the mealybug Heliococcus bohemicus, and by the scale insect Neopulvinaria innumerabilis. In this work, we studied the genetic structure and molecular variability of GVA, ascertaining its presence and spread in different commercial vineyards of four Sicilian provinces (Italy). In total, 11 autochthonous grapevine cultivars in 20 commercial Sicilian vineyards were investigated, for a total of 617 grapevine samples. Preliminary screening by serological (DAS-ELISA) analysis for GVA detection were conducted and subsequently confirmed by molecular (RT-PCR) analysis. Results showed that 10 out of the 11 cultivars analyzed were positive to GVA, for a total of 49 out of 617 samples (8%). A higher incidence of infection was detected on ‘Nerello Mascalese’, ‘Carricante’, ‘Perricone’ and ‘Nero d’Avola’ cultivars, followed by ‘Alicante’, ‘Grecanico’, ‘Catarratto’,‘Grillo’, ‘Nerello Cappuccio’ and ‘Zibibbo’, while in the ‘Moscato’ cultivar no infection was found. Phylogenetic analyses carried out on the coat protein (CP) gene of 16 GVA sequences selected in this study showed a low variability degree among the Sicilian isolates, closely related with other Italian isolates retrieved in GenBank, suggesting a common origin, probably due to the exchange of infected propagation material within the Italian territory.