<i>Grapevine rupestris stem pitting-associated virus</i> is linked with grapevine vein necrosis

Abstract

Vein necrosis (VN), a virus-like disease latent in all European grapevine cultivars and in most American rootstock species and hybrids, induces necrosis of the veinlets of its specific indicator Vitis rupestris x Vitis berlandieri 110 R at the abaxial side of the leaf blade. VN is very common in southern Italy, e.g. 109 out of 218 of the putative grapevine clones selected during sanitary improvement programmes in the last few years indexed positive in 110 R. As assessed by ELISA, the same vines had a very low rate of infection (< 4 %) by major detrimental viruses (GFLV, GVA, GVB, GLRaV-1, GLRaV-2, GLRaV-3, GLRaV-7, GFkV) commonly looked for during selection. When the VN-positive 110 R indicators were checked by PCR and Western blot for the presence of Grapevine rupestris stem pittingassociated virus (GRSPaV) a strikingly high association (98 %) was observed between this virus and VN symptoms. Likewise, all 72 mother plants of Vitis rupestris used as indicators in indexing trials and recently discovered to be infected by GRSPaV, induced VN reactions after grafting onto 110 R. By contrast, no VN reactions developed in 110 R top-grafted on a single GRSPaV-free V. rupestris. Moreover, GRSPaV was consistently detected in the symptomatic lower leaves of the shoots of infected 110 R vines, but not in the symptomless upper leaves of the same shoots. These findings strongly suggest that GRSPaV is involved in the aetiology of VN.