Grapevine leafroll‐associated viruses and grapevine virus A in selected Vitis vinifera cultivars in northern Italy

Abstract

The occurrence of grapevine leafroll‐associated virus 1 (GLRaV‐1), grapevine leafroll‐associated virus 3 (GLRaV‐3) and grapevine virus A (GVA) was demonstrated in a viticultural region of northern Italy (Emilia‐Romagna) using immunoelectron microscopy. Virus incidence was subsequently assessed using ELISA. A total of 60.6% of the 150 clone selections tested, from 18 local Vitis vinifera cultivars, were found to be infected. ELISA did not reveal the presence of grapevine leafroll‐associated virus 2 (GLRaV‐2) or grapevine leafroll‐associated virus 5 (GLRaV‐5). GLRaV‐1, GLRaV‐3 and GVA were found individually and in various combinations. The most common findings were GLRaV‐1 alone (25.3%) and associated with GVA (33%). Serological data confirmed that the majority (91%) of the clones known to be affected by grapevine leafroll (GLR), on its own or in association with rugose wood (RW), contained viruses. On the other hand, where the RW phenomenon was present on its own, only 40% of these clones were ELISA‐positive. The implications for the biology of GLR and RW are discussed and the complex aetiology of these grapevine diseases is confirmed.