Studies on a new grapevine disease in Trentino vineyards.

Symptoms of stunting, chlorotic mottling and leaf deformation with reduced yields and low quality of berries, were observed on cv. Pinot gris, in Trentino vineyards since 2003. Afterwards, similar symptoms were reported from cvs. Traminer, Pinot Noir in Trentino and Friuli-Venezia Giulia. Analysis by high throughput sequencing led to the discovery of a new trichovirus, named grapevine pinot gris virus (GPGV), closely related to grapevine inner berry necrosis (GINV). To define the aetiology and the biological features of the disease, field, greenhouse and laboratory studies were made. Field observations on a time span of three years (2010-12) indicated a progressive increase of diseased vines from 14,7 to 33,9 % in a cv. of Pinot gris vineyard whereas the incidence in a cv. Traminer vineyard was stationary and lower (ca.3%). RT-PCR assays showed that, in these vineyards, GPGV was present in all symptomatic but also in 70% of symptomless vines. Biological indexing demonstrated that GPGV is efficiently transmitted by grafting to Vitis riparia and V. vinifera cvs Pinot gris and Traminer inducing specific symptoms. A screening on different varieties and vineyards in the area suggests a widespread distribution of GPGV. Its presence appears closely associated with a disease condition although latent infections in symptomless vines can also occur.