Distinct Responses of Vitis aestivalis 'Norton' and Vitis vinifera 'Kishmish Vatkana' to Seven Viruses Revealed by Small RNA Sequencing

Grapevines are frequently infected by multiple viruses. Our previous study showed that Norton grapevine (Vitis aestivalis) is resistant to grapevine vein clearing virus (GVCV), a DNA virus in the family Caulimoviridae. To study the reaction of Norton to RNA viruses, we transferred seven RNA viruses to Norton from Kishmish Vatkana (KV) (V. vinifera) via graft transmission. We profiled viral small RNAs (vsRNAs) of the seven viruses and compared viral titers in Norton and KV. Total vsRNAs of grapevine leafroll-associated virus 1 (GLRaV-1), GLRaV-2, GLRaV-3, grapevine virus A (GVA), and grapevine Pinot gris virus (GPGV) were significantly less abundant in Norton than in KV, but total vsRNAs of grapevine fleck virus (GFkV) were more abundant in Norton than in KV. Total vsRNAs of grapevine rupestris stem pitting-associated virus (GRSPaV) were not different between Norton and KV. Grafting direction of Norton to KV or KV to Norton did not affect the quantity of vsRNAs. The genome coverage of GLRaV-1, GLRaV-2, GLRaV-3, and GVA vsRNAs was lower in Norton than KV. The 21- and 22-nucleotide classes of vsRNAs were predominant for all seven viruses. Virus quantification by quantitative PCR indicated that GLRaV-1 was undetectable in Norton; GLRaV-2, GLRaV-3, and GVA were less abundant in Norton; and GFkV was more abundant in Norton than in KV. These results demonstrated that Norton grapevine suppresses GLRaV-1, GLRaV-2, GLRaV-3, and GVA but supports GFkV in comparison with KV. This study revealed new facets of complex molecular interactions between grapevines and multiple viruses.