Infecting Nicotiana benthamiana and grapevine leaves with Grapevine fabavirus suggests its involvement in the crinkling and leaflet formation in grapevine leaves

‘Shine Muscat’ grapevines show symptoms of chlorotic mottling, leaf malformation, and leaflet in field. Identifying the specific pathogen responsible for these symptoms is difficult due to its susceptibility to multiple viruses. However, some studies suggest the involvement of Grapevine fabavirus (GFabV), although this has not been confirmed. To determine the symptoms induced by GFabV in plant leaves, seamless cloning was used to clone the full-length sequence of GFabV RNA1 and RNA2, which were then used to construct the pBI121-GFabV RNA1 and RNA2 expression vectors. The resulting clones were used to inoculate Nicotiana benthamiana and ‘Shine Muscat’ plants according to an Agrobacterium-mediated transformation. Visual symptoms and semi-quantitative RT-PCR results confirmed the infectivity. Sequencing showed that the nucleotide and amino acid homology between the GFabV RNA1 gene and ‘Nagano Purple’ (KX241482.1) were 100 %, and the nucleotide and amino acid homologies of the GFabV RNA2 gene of ‘Shine Muscat’ and ‘Black Beet’ (KX241485.1) were 98.8 % and 98.3 %, respectively. N. benthamiana and ‘Shine Muscat’ grapevines plants inoculated with GFabV RNA1 and RNA2 exhibited leaf crinkling on emerging leaves and leaflet symptoms. The inoculated leaves and the new young leaves showing the symptom were detected as GFabV RNA1 and RNA2 positive by RT-PCR. It could be concluded that the leaf crinkling and leaflet symptoms in ‘Shine Muscat’ grapevines are due to GFabV infection. The findings of this study enhance our understanding of the GFabV virus and paves the way for the control of viral diseases of grapevines.