Identification of Potato virus Y Strains Associated with Tuber Damage During a Recent Virus Outbreak in Potato in Idaho

Authors: KARASEV, A - University Of Idaho; MEACHAM, T - University Of Idaho; HU, X - University Of Idaho; Whitworth, Jonathan; Gray, Stewart; OLSEN, N - University Of Idaho; NOLTE, P - University Of Idaho

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2008
Publication Date: 9/1/2008
Citation: Karasev, A.V., Meacham, T., Hu, X., Whitworth, J.L., Gray, S.M., Olsen, N., Nolte, P. 2008. Identification of Potato virus Y Strains Associated with Tuber Damage During a Recent Virus Outbreak in Potato in Idaho. Plant Disease. 92:1371.

Interpretive Summary: Potato virus Y (PVY) causes yield and quality loss in potato. Seed certification systems have managed PVY with tolerances that limit the amount of PVY in a seed crop. Before 1990, PVYO was the predominant strain in North America. PVYO produces yield loss, but has no effect on tuber quality. In recent years, necrotic strains of PVY (PVYN, PVYNTN, and PVYN:O) have been detected in many potato growing areas across the U.S. Many of these strains have mild foliar symptoms, making them difficult to detect in certification systems that rely mainly on visual symptoms. The necrotic isolates also are associated with tuber necrosis identified as Potato tuber necrotic ringspot disease (PTNRD). Although tuber necrotic strains have been reported across the U.S. there is little information available on their incidence and spread in commercial potato production. Foliar and tuber samples with and without symptoms associated with PVY were collected from commercial fields in Idaho in 2007. Serological (ELISA), molecular (RT-PCR and limited sequencing), and tobacco bioassay showed that PVY necrotic strains including PVYO, PVYNTN, PVYN:O, and mixtures of each were present in symptomatic foliar and tuber samples.

Technical Abstract: Potato virus Y causes yield and quality loss due to the presence of necrotic strains (PVYN, PVYNTN, PVYN:O). During June and July, 2007, thirty-eight random samples from different commercial fields with disease symptoms were collected from fields near Idaho Falls, Idaho. Plants from cvs. Russet Burbank, Alturas, and Ranger Russet showed mosaic and leaf yellowing symptoms. These plants were tested with DAS-ELISA and a multiplex RT-PCR assay and twenty five were confirmed PVY positive. The RT_PCR results showed that twenty were infected with PVYNTN or PVYN:O. During September and October, 2007, twenty-five Russet Burbank tuber samples with various degrees of internal tuber symptoms (e.g. brown spots) were collected near Idaho Falls, ID. Twenty-two tubers were PVY positive by DAS-ELISA and multiplex RT-PCR showed thirteen were PVYNTN, three were PVYO, and two were mixtures (one PVYNTN/N:O and one PVYO/N:O). In October 2007, six Highland Russet tubers collected near Twin Falls, ID had external tuber damage characteristic of Potato tuber necrotic ringspot disease (PTNRD) caused by PVY necrotic strains. All six tubers were PVY positive by DAS-ELISA and RT-PCR assays identified five as PVYNTN and one as PVYN:O. Mixtures were separated by tobacco assays. Asymptomatic tubers from the same lot were PVY negative by DAS-ELISA and RT-PCR. All PVYNTN isolates collected in 2007 produced systemic vein necrosis confirming them as necrotic isolates. Limited sequencing showed they had recombinant junctures two and three, identifying them as being related to the European strain of PVYNTN. The data suggests an increase in distribution and increase of PVY in commercial potato productions areas of Idaho in 2007 and the potential for an increase in PTNRD.