We ran the RT-PCR method for the identification of viral isolates in selected grapevine plants that will be used as a viral source for our experiment. Few individuals were tested from the vineyard and we selected plants infected with only one virus (GLRaV-3) and plants that have mixed infections with five different viruses (GFkV, GVA, GLRaV-3, GLRaV-2, and GPGV). The tested grapevines will be used in the next experimental faze – infection of selected treatment with appropriate viral inoculum.