Incidence and Genetic Diversity of Grapevine Pinot gris Virus in California

Grapevine Pinot gris virus (GPGV) was discovered in 2012 by high throughput sequencing (HTS) analysis of Pinot gris vineyards in Italy. GPGV is often symptomless but has also been associated with chlorotic mottling and leaf deformation. In 2015, this new member of the genus Trichovirus was first reported in the United States, in California. To assess the incidence of GPGV throughout grapegrowing regions in California, we tested multiple vineyards using real-time quantitative reverse transcription PCR. HTS and phylogenetics were used to evaluate the genetic diversity of GPGV strains recovered. GPGV was detected in 170 out of 716 (23%) grapevine samples, including white and red grape varieties, from several commercial vineyards and one nursery increase block. Moreover, GPGV was identified in three different counties (Yolo, Solano, and Napa) situated in northern California. In the case of Napa County, a widespread distribution of GPGV was determined. During the survey, symptomatic and asymptomatic plants tested positive for GPGV; however, characterized isolates shared close homology (>97% identity) with asymptomatic reference isolates, which was confirmed by phylogenetics. HTS revealed that GPGV-positive grapevines were also infected with other viruses and viroids. Finally, the relationship between GPGV infection and symptom expression is discussed.