Detection of PVM RNA in potato samples by RT-PCR and confirmation of PCR products by restriction analysis. PCR amplicons (520 bp) were produced in RT-PCR using primers PVM3 and PVM4 from RNA extracted from PVM-Ca508 infected tuber (lanes 2), leaf (lane 4) and sprout (lanes 6) samples. PCR products were digested into two fragments, 370 and 150 bp with Msc I (lanes 3, 5, 7) for verification. M: Molecular weight marker (100 bp DNA ladder, New England Biolabs, Pickering, Ontario); No-template control (lane 1) and negative control (RNA extracted from healthy leaves, lane 8) were used for PCR. Gel electrophoresis: 1.5% Agarose-1000 (Invitrogen Canada, Burlington, Ontario).