The detection of tuber necrotic isolates of Potato virus Y, and the accurate discrimination of PVYO, PVYN and PVYC strains using RT-PCR

Potato tuber necrotic ringspot disease (PTNRD) is a damaging disease of potatoes, causing unsightly necrotic rings on the surface of tubers. The causal agent is thought to be tuber necrotic isolates of Potato virus Y, known as PVYNTN. The disease spoils tubers for processing and table use, and the lack of a diagnostic method makes control especially difficult. The development of an RT-PCR assay for the reliable detection of PVYNTN and discrimination of all the main strains of PVY (PVYO, PVYN and PVYC) is described. An assay was developed, exploiting a recombination site in the coat protein of PVYNTN, allowing more reliable diagnosis of these isolates. Although the conserved nucleotide differences observed between the strains was very small, competitive PCR and mutagenically separated PCR were both employed in the development of a robust assay. The assay was found to be more reliable than the most commonly used RT-PCR method, and should prove to be an important tool in the confirmation of symptoms and for the detection of PVYNTN in symptomless tissue, in disease surveys and seed health schemes. (C) 2002 Elsevier Science B,V. All rights reserved.