Screening by a 3-primer PCR of North American PVYN isolates for European-type members of the tuber necrosis-inducing PVYNTN subgroup

Oligonucleotide primers for a 3-primer polymerase chain reaction (PCR) were optimized by adjusting their T-m values to identify European-type members of the potato tuber necrotic ringspot disease (PTNRD) inducing PVYNTN sub-g roup of PVYN. Fifty-seven North American isolate; of PVYN were screened usi ng this assay and one, originating from garden potato tubers in Ontario, wa s found to be positive. This isolate was confirmed to induce the diagnostic PTNRD, using a panel of 20 potato cultivars. AC Chaleur, AC Novachip, Cent ury Russet, Cherokee, and Frontier Russet reacted severely and developed PT NRD either at the time of harvest or during storage. About 800 tubers colle cted from New Brunswick and Prince Edward Island fields, from plants exhibi ting mosaic and leafroll symptoms were also screened for various strains:of PVY using PCR primers. Results indicate that primer pairs developed are sp ecific for PVY spp., PVYN, and PVYNTN.