Agroinoculation of Grapevine Pinot Gris Virus in tobacco and grapevine provides insights on viral pathogenesis.

Giulia Tarquini,Nazia Loi,Barbara Franco-Orozco,Francesca De Amicis,Laura Pagliari,Paolo Ermacora,Gian Luca Bianchi,Rita Musetti,Giusi Zaina,Marta Martini,Giuseppe Firrao,Emanuele De Paoli

doi:10.1371/journal.pone.0214010

Giulia Tarquini, Nazia Loi + Show 10 more

Open Access

https://doi.org/10.1371/journal.pone.0214010

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Abstract

The Grapevine Pinot Gris disease (GPG-d) is a novel disease characterized by symptoms such as leaf mottling and deformation, which has been recently reported in grapevines, and mostly in Pinot gris. Plants show obvious symptoms at the beginning of the growing season, while during summer symptom recovery frequently occurs, manifesting as symptomless leaves. A new Trichovirus, named Grapevine Pinot gris virus (GPGV), which belongs to the family Betaflexiviridae was found in association with infected plants. The detection of the virus in asymptomatic grapevines raised doubts about disease aetiology. Therefore, the primary target of this work was to set up a reliable system for the study of the disease in controlled conditions, avoiding interfering factor(s) that could affect symptom development. To this end, two clones of the virus, pRI::GPGV-vir and pRI::GPGV-lat, were generated from total RNA collected from one symptomatic and one asymptomatic Pinot gris grapevine, respectively. The clones, which encompassed the entire genome of the virus, were used in Agrobacterium-mediated inoculation of Vitis vinifera and Nicotiana benthamiana plants. All inoculated plants developed symptoms regardless of their inoculum source, demonstrating a correlation between the presence of GPGV and symptomatic manifestations. Four months post inoculum, the grapevines inoculated with the pRI::GPGV-lat clone developed asymptomatic leaves that were still positive to GPGV detection. Three to four weeks later (i.e. ca. 5 months post inoculum), the same phenomenon was observed in the grapevines inoculated with pRI::GPGV-vir. This observation perfectly matches symptom progression in infected field-grown grapevines, suggesting a possible role for plant antiviral mechanisms, such as RNA silencing, in the recovery process.

Highlights

A grapevine disease consisting of leaf mottling and deformation has been recently reported in northeast Italy and Slovenia[1]
The disease was detected for the first time in Pinot gris, so that the disorder is called “Grapevine Pinot gris disease” even though it was later identified in other varieties, such as Traminer, Tocai (Friulano) and Glera [2]
The aetiology of the Grapevine Pinot gris disease (GPG-d) is still questioned: in 2012 a new virus, named Grapevine Pinot Gris virus (GPGV), was identified in diseased grapevines in Trentino-Alto Adige [3], but its presence could not be directly correlated to the symptoms because the virus was detected in all symptomatic grapevines and in plants showing no visible alteration [2,3,4]

Summary

Introduction

A grapevine disease consisting of leaf mottling and deformation has been recently reported in northeast Italy and Slovenia[1]. The aetiology of the Grapevine Pinot gris disease (GPG-d) is still questioned: in 2012 a new virus, named Grapevine Pinot Gris virus (GPGV), was identified in diseased grapevines in Trentino-Alto Adige (northeast Italy) [3], but its presence could not be directly correlated to the symptoms because the virus was detected in all symptomatic grapevines and in plants showing no visible alteration [2,3,4]. The virus was detected in grapevines from other Italian regions affected by the disease as well as from other countries, a number of these wine growing regions have never reported symptoms of the disease [4]

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